Merge pull request 'Aerogramme refactoring' (#57) from feat/more-imap-qol into main

Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/aerogramme/pulls/57

11 files changed, 1349 insertions, 1025 deletions

diff --git a/src/imap/attributes.rs b/src/imap/attributes.rs
new file mode 100644
index 0000000..7a55632
--- /dev/null
+++ b/src/imap/attributes.rs
@@ -0,0 +1,49 @@
+use imap_codec::imap_types::fetch::{MacroOrMessageDataItemNames, MessageDataItemName};
+
+/// Internal decisions based on fetched attributes
+/// passed by the client
+
+pub struct AttributesProxy {
+    pub attrs: Vec<MessageDataItemName<'static>>,
+}
+impl AttributesProxy {
+    pub fn new(attrs: &MacroOrMessageDataItemNames<'static>, is_uid_fetch: bool) -> Self {
+        // Expand macros
+        let mut fetch_attrs = match attrs {
+            MacroOrMessageDataItemNames::Macro(m) => {
+                use imap_codec::imap_types::fetch::Macro;
+                use MessageDataItemName::*;
+                match m {
+                    Macro::All => vec![Flags, InternalDate, Rfc822Size, Envelope],
+                    Macro::Fast => vec![Flags, InternalDate, Rfc822Size],
+                    Macro::Full => vec![Flags, InternalDate, Rfc822Size, Envelope, Body],
+                    _ => {
+                        tracing::error!("unimplemented macro");
+                        vec![]
+                    }
+                }
+            }
+            MacroOrMessageDataItemNames::MessageDataItemNames(a) => a.clone(),
+        };
+
+        // Handle uids
+        if is_uid_fetch && !fetch_attrs.contains(&MessageDataItemName::Uid) {
+            fetch_attrs.push(MessageDataItemName::Uid);
+        }
+
+        Self { attrs: fetch_attrs }
+    }
+
+    pub fn need_body(&self) -> bool {
+        self.attrs.iter().any(|x| {
+            matches!(
+                x,
+                MessageDataItemName::Body
+                    | MessageDataItemName::BodyExt { .. }
+                    | MessageDataItemName::Rfc822
+                    | MessageDataItemName::Rfc822Text
+                    | MessageDataItemName::BodyStructure
+            )
+        })
+    }
+}
diff --git a/src/imap/command/examined.rs b/src/imap/command/examined.rs
index 0d688c0..ec16973 100644
--- a/src/imap/command/examined.rs
+++ b/src/imap/command/examined.rs
@@ -125,7 +125,7 @@ impl<'a> ExaminedContext<'a> {
     }
 
     pub async fn noop(self) -> Result<(Response<'static>, flow::Transition)> {
-        self.mailbox.mailbox.force_sync().await?;
+        self.mailbox.0.mailbox.force_sync().await?;
 
         let updates = self.mailbox.update().await?;
         Ok((
diff --git a/src/imap/command/selected.rs b/src/imap/command/selected.rs
index c8cc680..35c3eb4 100644
--- a/src/imap/command/selected.rs
+++ b/src/imap/command/selected.rs
@@ -136,21 +136,23 @@ impl<'a> SelectedContext<'a> {
 
     pub async fn search(
         self,
-        _charset: &Option<Charset<'a>>,
-        _criteria: &SearchKey<'a>,
-        _uid: &bool,
+        charset: &Option<Charset<'a>>,
+        criteria: &SearchKey<'a>,
+        uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
+        let found = self.mailbox.search(charset, criteria, *uid).await?;
         Ok((
             Response::build()
                 .to_req(self.req)
-                .message("Not implemented")
-                .bad()?,
+                .set_body(found)
+                .message("SEARCH completed")
+                .ok()?,
             flow::Transition::None,
         ))
     }
 
     pub async fn noop(self) -> Result<(Response<'static>, flow::Transition)> {
-        self.mailbox.mailbox.force_sync().await?;
+        self.mailbox.0.mailbox.force_sync().await?;
 
         let updates = self.mailbox.update().await?;
         Ok((
diff --git a/src/imap/flags.rs b/src/imap/flags.rs
new file mode 100644
index 0000000..0f6ec64
--- /dev/null
+++ b/src/imap/flags.rs
@@ -0,0 +1,30 @@
+use imap_codec::imap_types::core::Atom;
+use imap_codec::imap_types::flag::{Flag, FlagFetch};
+
+pub fn from_str(f: &str) -> Option<FlagFetch<'static>> {
+    match f.chars().next() {
+        Some('\\') => match f {
+            "\\Seen" => Some(FlagFetch::Flag(Flag::Seen)),
+            "\\Answered" => Some(FlagFetch::Flag(Flag::Answered)),
+            "\\Flagged" => Some(FlagFetch::Flag(Flag::Flagged)),
+            "\\Deleted" => Some(FlagFetch::Flag(Flag::Deleted)),
+            "\\Draft" => Some(FlagFetch::Flag(Flag::Draft)),
+            "\\Recent" => Some(FlagFetch::Recent),
+            _ => match Atom::try_from(f.strip_prefix('\\').unwrap().to_string()) {
+                Err(_) => {
+                    tracing::error!(flag=%f, "Unable to encode flag as IMAP atom");
+                    None
+                }
+                Ok(a) => Some(FlagFetch::Flag(Flag::system(a))),
+            },
+        },
+        Some(_) => match Atom::try_from(f.to_string()) {
+            Err(_) => {
+                tracing::error!(flag=%f, "Unable to encode flag as IMAP atom");
+                None
+            }
+            Ok(a) => Some(FlagFetch::Flag(Flag::keyword(a))),
+        },
+        None => None,
+    }
+}
diff --git a/src/imap/imf_view.rs b/src/imap/imf_view.rs
new file mode 100644
index 0000000..4297769
--- /dev/null
+++ b/src/imap/imf_view.rs
@@ -0,0 +1,97 @@
+use imap_codec::imap_types::core::{IString, NString};
+use imap_codec::imap_types::envelope::{Address, Envelope};
+
+use eml_codec::imf;
+
+/// Envelope rules are defined in RFC 3501, section 7.4.2
+/// https://datatracker.ietf.org/doc/html/rfc3501#section-7.4.2
+///
+/// Some important notes:
+///
+/// If the Sender or Reply-To lines are absent in the [RFC-2822]
+/// header, or are present but empty, the server sets the
+/// corresponding member of the envelope to be the same value as
+/// the from member (the client is not expected to know to do
+/// this). Note: [RFC-2822] requires that all messages have a valid
+/// From header.  Therefore, the from, sender, and reply-to
+/// members in the envelope can not be NIL.
+///
+/// If the Date, Subject, In-Reply-To, and Message-ID header lines
+/// are absent in the [RFC-2822] header, the corresponding member
+/// of the envelope is NIL; if these header lines are present but
+/// empty the corresponding member of the envelope is the empty
+/// string.
+
+//@FIXME return an error if the envelope is invalid instead of panicking
+//@FIXME some fields must be defaulted if there are not set.
+pub fn message_envelope(msg: &imf::Imf) -> Envelope<'static> {
+    let from = msg.from.iter().map(convert_mbx).collect::<Vec<_>>();
+
+    Envelope {
+        date: NString(
+            msg.date
+                .as_ref()
+                .map(|d| IString::try_from(d.to_rfc3339()).unwrap()),
+        ),
+        subject: NString(
+            msg.subject
+                .as_ref()
+                .map(|d| IString::try_from(d.to_string()).unwrap()),
+        ),
+        sender: msg
+            .sender
+            .as_ref()
+            .map(|v| vec![convert_mbx(v)])
+            .unwrap_or(from.clone()),
+        reply_to: if msg.reply_to.is_empty() {
+            from.clone()
+        } else {
+            convert_addresses(&msg.reply_to)
+        },
+        from,
+        to: convert_addresses(&msg.to),
+        cc: convert_addresses(&msg.cc),
+        bcc: convert_addresses(&msg.bcc),
+        in_reply_to: NString(
+            msg.in_reply_to
+                .iter()
+                .next()
+                .map(|d| IString::try_from(d.to_string()).unwrap()),
+        ),
+        message_id: NString(
+            msg.msg_id
+                .as_ref()
+                .map(|d| IString::try_from(d.to_string()).unwrap()),
+        ),
+    }
+}
+
+pub fn convert_addresses(addrlist: &Vec<imf::address::AddressRef>) -> Vec<Address<'static>> {
+    let mut acc = vec![];
+    for item in addrlist {
+        match item {
+            imf::address::AddressRef::Single(a) => acc.push(convert_mbx(a)),
+            imf::address::AddressRef::Many(l) => acc.extend(l.participants.iter().map(convert_mbx)),
+        }
+    }
+    return acc;
+}
+
+pub fn convert_mbx(addr: &imf::mailbox::MailboxRef) -> Address<'static> {
+    Address {
+        name: NString(
+            addr.name
+                .as_ref()
+                .map(|x| IString::try_from(x.to_string()).unwrap()),
+        ),
+        // SMTP at-domain-list (source route) seems obsolete since at least 1991
+        // https://www.mhonarc.org/archive/html/ietf-822/1991-06/msg00060.html
+        adl: NString(None),
+        mailbox: NString(Some(
+            IString::try_from(addr.addrspec.local_part.to_string()).unwrap(),
+        )),
+        host: NString(Some(
+            IString::try_from(addr.addrspec.domain.to_string()).unwrap(),
+        )),
+    }
+}
diff --git a/src/imap/index.rs b/src/imap/index.rs
new file mode 100644
index 0000000..01dd2ef
--- /dev/null
+++ b/src/imap/index.rs
@@ -0,0 +1,95 @@
+use std::num::NonZeroU32;
+
+use anyhow::{anyhow, bail, Result};
+use imap_codec::imap_types::sequence::{self, SequenceSet};
+
+use crate::mail::uidindex::{ImapUid, UidIndex};
+use crate::mail::unique_ident::UniqueIdent;
+
+pub struct Index<'a>(pub &'a UidIndex);
+impl<'a> Index<'a> {
+    pub fn fetch(
+        self: &Index<'a>,
+        sequence_set: &SequenceSet,
+        by_uid: bool,
+    ) -> Result<Vec<MailIndex<'a>>> {
+        let mail_vec = self
+            .0
+            .idx_by_uid
+            .iter()
+            .map(|(uid, uuid)| (*uid, *uuid))
+            .collect::<Vec<_>>();
+
+        let mut mails = vec![];
+
+        if by_uid {
+            if mail_vec.is_empty() {
+                return Ok(vec![]);
+            }
+            let iter_strat = sequence::Strategy::Naive {
+                largest: mail_vec.last().unwrap().0,
+            };
+
+            let mut i = 0;
+            for uid in sequence_set.iter(iter_strat) {
+                while mail_vec.get(i).map(|mail| mail.0 < uid).unwrap_or(false) {
+                    i += 1;
+                }
+                if let Some(mail) = mail_vec.get(i) {
+                    if mail.0 == uid {
+                        mails.push(MailIndex {
+                            i: NonZeroU32::try_from(i as u32 + 1).unwrap(),
+                            uid: mail.0,
+                            uuid: mail.1,
+                            flags: self
+                                .0
+                                .table
+                                .get(&mail.1)
+                                .ok_or(anyhow!("mail is missing from index"))?
+                                .1
+                                .as_ref(),
+                        });
+                    }
+                } else {
+                    break;
+                }
+            }
+        } else {
+            if mail_vec.is_empty() {
+                bail!("No such message (mailbox is empty)");
+            }
+
+            let iter_strat = sequence::Strategy::Naive {
+                largest: NonZeroU32::try_from((mail_vec.len()) as u32).unwrap(),
+            };
+
+            for i in sequence_set.iter(iter_strat) {
+                if let Some(mail) = mail_vec.get(i.get() as usize - 1) {
+                    mails.push(MailIndex {
+                        i,
+                        uid: mail.0,
+                        uuid: mail.1,
+                        flags: self
+                            .0
+                            .table
+                            .get(&mail.1)
+                            .ok_or(anyhow!("mail is missing from index"))?
+                            .1
+                            .as_ref(),
+                    });
+                } else {
+                    bail!("No such mail: {}", i);
+                }
+            }
+        }
+
+        Ok(mails)
+    }
+}
+
+pub struct MailIndex<'a> {
+    pub i: NonZeroU32,
+    pub uid: ImapUid,
+    pub uuid: UniqueIdent,
+    pub flags: &'a Vec<String>,
+}
diff --git a/src/imap/mail_view.rs b/src/imap/mail_view.rs
new file mode 100644
index 0000000..de9bfe3
--- /dev/null
+++ b/src/imap/mail_view.rs
@@ -0,0 +1,247 @@
+use std::num::NonZeroU32;
+
+use anyhow::{anyhow, bail, Result};
+use chrono::{Offset, TimeZone, Utc};
+
+use imap_codec::imap_types::core::NString;
+use imap_codec::imap_types::datetime::DateTime;
+use imap_codec::imap_types::fetch::{
+    MessageDataItem, MessageDataItemName, Section as FetchSection,
+};
+use imap_codec::imap_types::flag::Flag;
+use imap_codec::imap_types::response::Data;
+
+use eml_codec::{
+    imf,
+    part::{composite::Message, AnyPart},
+};
+
+use crate::mail::query::QueryResult;
+
+use crate::imap::attributes::AttributesProxy;
+use crate::imap::flags;
+use crate::imap::imf_view::message_envelope;
+use crate::imap::index::MailIndex;
+use crate::imap::mime_view;
+use crate::imap::response::Body;
+
+pub struct MailView<'a> {
+    pub in_idx: MailIndex<'a>,
+    pub query_result: &'a QueryResult<'a>,
+    pub content: FetchedMail<'a>,
+}
+
+impl<'a> MailView<'a> {
+    pub fn new(query_result: &'a QueryResult<'a>, in_idx: MailIndex<'a>) -> Result<MailView<'a>> {
+        Ok(Self {
+            in_idx,
+            query_result,
+            content: match query_result {
+                QueryResult::FullResult { content, .. } => {
+                    let (_, parsed) =
+                        eml_codec::parse_message(&content).or(Err(anyhow!("Invalid mail body")))?;
+                    FetchedMail::new_from_message(parsed)
+                }
+                QueryResult::PartialResult { metadata, .. } => {
+                    let (_, parsed) = eml_codec::parse_imf(&metadata.headers)
+                        .or(Err(anyhow!("unable to parse email headers")))?;
+                    FetchedMail::Partial(parsed)
+                }
+                QueryResult::IndexResult { .. } => FetchedMail::IndexOnly,
+            },
+        })
+    }
+
+    fn uid(&self) -> MessageDataItem<'static> {
+        MessageDataItem::Uid(self.in_idx.uid.clone())
+    }
+
+    fn flags(&self) -> MessageDataItem<'static> {
+        MessageDataItem::Flags(
+            self.in_idx
+                .flags
+                .iter()
+                .filter_map(|f| flags::from_str(f))
+                .collect(),
+        )
+    }
+
+    fn rfc_822_size(&self) -> Result<MessageDataItem<'static>> {
+        let sz = self
+            .query_result
+            .metadata()
+            .ok_or(anyhow!("mail metadata are required"))?
+            .rfc822_size;
+        Ok(MessageDataItem::Rfc822Size(sz as u32))
+    }
+
+    fn rfc_822_header(&self) -> Result<MessageDataItem<'static>> {
+        let hdrs: NString = self
+            .query_result
+            .metadata()
+            .ok_or(anyhow!("mail metadata are required"))?
+            .headers
+            .to_vec()
+            .try_into()?;
+        Ok(MessageDataItem::Rfc822Header(hdrs))
+    }
+
+    fn rfc_822_text(&self) -> Result<MessageDataItem<'static>> {
+        let txt: NString = self.content.as_full()?.raw_body.to_vec().try_into()?;
+        Ok(MessageDataItem::Rfc822Text(txt))
+    }
+
+    fn rfc822(&self) -> Result<MessageDataItem<'static>> {
+        let full: NString = self.content.as_full()?.raw_part.to_vec().try_into()?;
+        Ok(MessageDataItem::Rfc822(full))
+    }
+
+    fn envelope(&self) -> MessageDataItem<'static> {
+        MessageDataItem::Envelope(message_envelope(self.content.imf().clone()))
+    }
+
+    fn body(&self) -> Result<MessageDataItem<'static>> {
+        Ok(MessageDataItem::Body(mime_view::bodystructure(
+            self.content.as_full()?.child.as_ref(),
+        )?))
+    }
+
+    fn body_structure(&self) -> Result<MessageDataItem<'static>> {
+        Ok(MessageDataItem::Body(mime_view::bodystructure(
+            self.content.as_full()?.child.as_ref(),
+        )?))
+    }
+
+    /// maps to BODY[<section>]<<partial>> and BODY.PEEK[<section>]<<partial>>
+    /// peek does not implicitly set the \Seen flag
+    /// eg. BODY[HEADER.FIELDS (DATE FROM)]
+    /// eg. BODY[]<0.2048>
+    fn body_ext(
+        &self,
+        section: &Option<FetchSection<'static>>,
+        partial: &Option<(u32, NonZeroU32)>,
+        peek: &bool,
+    ) -> Result<(MessageDataItem<'static>, SeenFlag)> {
+        // Manage Seen flag
+        let mut seen = SeenFlag::DoNothing;
+        let seen_flag = Flag::Seen.to_string();
+        if !peek && !self.in_idx.flags.iter().any(|x| *x == seen_flag) {
+            // Add \Seen flag
+            //self.mailbox.add_flags(uuid, &[seen_flag]).await?;
+            seen = SeenFlag::MustAdd;
+        }
+
+        // Process message
+        let (text, origin) =
+            match mime_view::body_ext(self.content.as_anypart()?, section, partial)? {
+                mime_view::BodySection::Full(body) => (body, None),
+                mime_view::BodySection::Slice { body, origin_octet } => (body, Some(origin_octet)),
+            };
+
+        let data: NString = text.to_vec().try_into()?;
+
+        return Ok((
+            MessageDataItem::BodyExt {
+                section: section.as_ref().map(|fs| fs.clone()),
+                origin,
+                data,
+            },
+            seen,
+        ));
+    }
+
+    fn internal_date(&self) -> Result<MessageDataItem<'static>> {
+        let dt = Utc
+            .fix()
+            .timestamp_opt(
+                i64::try_from(
+                    self.query_result
+                        .metadata()
+                        .ok_or(anyhow!("mail metadata were not fetched"))?
+                        .internaldate
+                        / 1000,
+                )?,
+                0,
+            )
+            .earliest()
+            .ok_or(anyhow!("Unable to parse internal date"))?;
+        Ok(MessageDataItem::InternalDate(DateTime::unvalidated(dt)))
+    }
+
+    pub fn filter(&self, ap: &AttributesProxy) -> Result<(Body<'static>, SeenFlag)> {
+        let mut seen = SeenFlag::DoNothing;
+        let res_attrs = ap
+            .attrs
+            .iter()
+            .map(|attr| match attr {
+                MessageDataItemName::Uid => Ok(self.uid()),
+                MessageDataItemName::Flags => Ok(self.flags()),
+                MessageDataItemName::Rfc822Size => self.rfc_822_size(),
+                MessageDataItemName::Rfc822Header => self.rfc_822_header(),
+                MessageDataItemName::Rfc822Text => self.rfc_822_text(),
+                MessageDataItemName::Rfc822 => self.rfc822(),
+                MessageDataItemName::Envelope => Ok(self.envelope()),
+                MessageDataItemName::Body => self.body(),
+                MessageDataItemName::BodyStructure => self.body_structure(),
+                MessageDataItemName::BodyExt {
+                    section,
+                    partial,
+                    peek,
+                } => {
+                    let (body, has_seen) = self.body_ext(section, partial, peek)?;
+                    seen = has_seen;
+                    Ok(body)
+                }
+                MessageDataItemName::InternalDate => self.internal_date(),
+            })
+            .collect::<Result<Vec<_>, _>>()?;
+
+        Ok((
+            Body::Data(Data::Fetch {
+                seq: self.in_idx.i,
+                items: res_attrs.try_into()?,
+            }),
+            seen,
+        ))
+    }
+}
+
+pub enum SeenFlag {
+    DoNothing,
+    MustAdd,
+}
+
+// -------------------
+
+pub enum FetchedMail<'a> {
+    IndexOnly,
+    Partial(imf::Imf<'a>),
+    Full(AnyPart<'a>),
+}
+impl<'a> FetchedMail<'a> {
+    pub fn new_from_message(msg: Message<'a>) -> Self {
+        Self::Full(AnyPart::Msg(msg))
+    }
+
+    fn as_anypart(&self) -> Result<&AnyPart<'a>> {
+        match self {
+            FetchedMail::Full(x) => Ok(&x),
+            _ => bail!("The full message must be fetched, not only its headers"),
+        }
+    }
+
+    fn as_full(&self) -> Result<&Message<'a>> {
+        match self {
+            FetchedMail::Full(AnyPart::Msg(x)) => Ok(&x),
+            _ => bail!("The full message must be fetched, not only its headers AND it must be an AnyPart::Msg."),
+        }
+    }
+
+    fn imf(&self) -> &imf::Imf<'a> {
+        match self {
+            FetchedMail::Full(AnyPart::Msg(x)) => &x.imf,
+            FetchedMail::Partial(x) => &x,
+            _ => panic!("Can't contain AnyPart that is not a message"),
+        }
+    }
+}
diff --git a/src/imap/mailbox_view.rs b/src/imap/mailbox_view.rs
index 861d27c..e4ffdcd 100644
--- a/src/imap/mailbox_view.rs
+++ b/src/imap/mailbox_view.rs
@@ -1,35 +1,28 @@
-use std::borrow::Cow;
-use std::iter::zip;
 use std::num::NonZeroU32;
 use std::sync::Arc;
 
-use anyhow::{anyhow, bail, Error, Result};
-use chrono::{Offset, TimeZone, Utc};
+use anyhow::{anyhow, Error, Result};
 
 use futures::stream::{FuturesOrdered, StreamExt};
 
-use imap_codec::imap_types::body::{BasicFields, Body as FetchBody, BodyStructure, SpecificFields};
-use imap_codec::imap_types::core::{AString, Atom, IString, NString, NonEmptyVec};
-use imap_codec::imap_types::datetime::DateTime;
-use imap_codec::imap_types::envelope::{Address, Envelope};
-use imap_codec::imap_types::fetch::{
-    MacroOrMessageDataItemNames, MessageDataItem, MessageDataItemName, Section as FetchSection,
-};
+use imap_codec::imap_types::core::Charset;
+use imap_codec::imap_types::fetch::{MacroOrMessageDataItemNames, MessageDataItem};
 use imap_codec::imap_types::flag::{Flag, FlagFetch, FlagPerm, StoreResponse, StoreType};
 use imap_codec::imap_types::response::{Code, Data, Status};
-use imap_codec::imap_types::sequence::{self, SequenceSet};
-
-use eml_codec::{
-    header, imf, mime,
-    mime::r#type::Deductible,
-    part::{composite::Message, AnyPart},
-};
-
-use crate::cryptoblob::Key;
+use imap_codec::imap_types::search::SearchKey;
+use imap_codec::imap_types::sequence::SequenceSet;
+
+use crate::mail::mailbox::Mailbox;
+use crate::mail::query::QueryScope;
+use crate::mail::snapshot::FrozenMailbox;
+use crate::mail::uidindex::{ImapUid, ImapUidvalidity};
+
+use crate::imap::attributes::AttributesProxy;
+use crate::imap::flags;
+use crate::imap::index::Index;
+use crate::imap::mail_view::{MailView, SeenFlag};
 use crate::imap::response::Body;
-use crate::mail::mailbox::{MailMeta, Mailbox};
-use crate::mail::uidindex::{ImapUid, ImapUidvalidity, UidIndex};
-use crate::mail::unique_ident::UniqueIdent;
+use crate::imap::search;
 
 const DEFAULT_FLAGS: [Flag; 5] = [
     Flag::Seen,
@@ -39,377 +32,6 @@ const DEFAULT_FLAGS: [Flag; 5] = [
     Flag::Draft,
 ];
 
-enum FetchedMail<'a> {
-    Partial(imf::Imf<'a>),
-    Full(AnyPart<'a>),
-}
-impl<'a> FetchedMail<'a> {
-    fn new_from_message(msg: Message<'a>) -> Self {
-        FetchedMail::Full(AnyPart::Msg(msg))
-    }
-
-    /*fn new_from_header(hdr: imf::Imf<'a>) -> Self {
-        FetchedMail::Partial(hdr)
-    }*/
-
-    fn as_anypart(&self) -> Result<&AnyPart<'a>> {
-        match self {
-            FetchedMail::Full(x) => Ok(&x),
-            _ => bail!("The full message must be fetched, not only its headers"),
-        }
-    }
-
-    fn as_full(&self) -> Result<&Message<'a>> {
-        match self {
-            FetchedMail::Full(AnyPart::Msg(x)) => Ok(&x),
-            _ => bail!("The full message must be fetched, not only its headers AND it must be an AnyPart::Msg."),
-        }
-    }
-
-    fn imf(&self) -> &imf::Imf<'a> {
-        match self {
-            FetchedMail::Full(AnyPart::Msg(x)) => &x.imf,
-            FetchedMail::Partial(x) => &x,
-            _ => panic!("Can't contain AnyPart that is not a message"),
-        }
-    }
-}
-
-pub struct AttributesProxy {
-    attrs: Vec<MessageDataItemName<'static>>,
-}
-impl AttributesProxy {
-    fn new(attrs: &MacroOrMessageDataItemNames<'static>, is_uid_fetch: bool) -> Self {
-        // Expand macros
-        let mut fetch_attrs = match attrs {
-            MacroOrMessageDataItemNames::Macro(m) => {
-                use imap_codec::imap_types::fetch::Macro;
-                use MessageDataItemName::*;
-                match m {
-                    Macro::All => vec![Flags, InternalDate, Rfc822Size, Envelope],
-                    Macro::Fast => vec![Flags, InternalDate, Rfc822Size],
-                    Macro::Full => vec![Flags, InternalDate, Rfc822Size, Envelope, Body],
-                    _ => {
-                        tracing::error!("unimplemented macro");
-                        vec![]
-                    }
-                }
-            }
-            MacroOrMessageDataItemNames::MessageDataItemNames(a) => a.clone(),
-        };
-
-        // Handle uids
-        if is_uid_fetch && !fetch_attrs.contains(&MessageDataItemName::Uid) {
-            fetch_attrs.push(MessageDataItemName::Uid);
-        }
-
-        Self { attrs: fetch_attrs }
-    }
-
-    fn need_body(&self) -> bool {
-        self.attrs.iter().any(|x| {
-            matches!(
-                x,
-                MessageDataItemName::Body
-                    | MessageDataItemName::BodyExt { .. }
-                    | MessageDataItemName::Rfc822
-                    | MessageDataItemName::Rfc822Text
-                    | MessageDataItemName::BodyStructure
-            )
-        })
-    }
-}
-
-pub struct MailIdentifiers {
-    i: NonZeroU32,
-    uid: ImapUid,
-    uuid: UniqueIdent,
-}
-struct MailIdentifiersList(Vec<MailIdentifiers>);
-
-impl MailIdentifiersList {
-    fn uuids(&self) -> Vec<UniqueIdent> {
-        self.0.iter().map(|mi| mi.uuid).collect()
-    }
-}
-
-pub struct MailView<'a> {
-    ids: &'a MailIdentifiers,
-    meta: &'a MailMeta,
-    flags: &'a Vec<String>,
-    content: FetchedMail<'a>,
-}
-
-enum SeenFlag {
-    DoNothing,
-    MustAdd,
-}
-
-impl<'a> MailView<'a> {
-    fn uid(&self) -> MessageDataItem<'static> {
-        MessageDataItem::Uid(self.ids.uid.clone())
-    }
-
-    fn flags(&self) -> MessageDataItem<'static> {
-        MessageDataItem::Flags(
-            self.flags
-                .iter()
-                .filter_map(|f| string_to_flag(f))
-                .collect(),
-        )
-    }
-
-    fn rfc_822_size(&self) -> MessageDataItem<'static> {
-        MessageDataItem::Rfc822Size(self.meta.rfc822_size as u32)
-    }
-
-    fn rfc_822_header(&self) -> MessageDataItem<'static> {
-        MessageDataItem::Rfc822Header(NString(
-            self.meta
-                .headers
-                .to_vec()
-                .try_into()
-                .ok()
-                .map(IString::Literal),
-        ))
-    }
-
-    fn rfc_822_text(&self) -> Result<MessageDataItem<'static>> {
-        Ok(MessageDataItem::Rfc822Text(NString(
-            self.content
-                .as_full()?
-                .raw_body
-                .to_vec()
-                .try_into()
-                .ok()
-                .map(IString::Literal),
-        )))
-    }
-
-    fn rfc822(&self) -> Result<MessageDataItem<'static>> {
-        Ok(MessageDataItem::Rfc822(NString(
-            self.content
-                .as_full()?
-                .raw_part
-                .to_vec()
-                .try_into()
-                .ok()
-                .map(IString::Literal),
-        )))
-    }
-
-    fn envelope(&self) -> MessageDataItem<'static> {
-        MessageDataItem::Envelope(message_envelope(self.content.imf().clone()))
-    }
-
-    fn body(&self) -> Result<MessageDataItem<'static>> {
-        Ok(MessageDataItem::Body(build_imap_email_struct(
-            self.content.as_full()?.child.as_ref(),
-        )?))
-    }
-
-    fn body_structure(&self) -> Result<MessageDataItem<'static>> {
-        Ok(MessageDataItem::Body(build_imap_email_struct(
-            self.content.as_full()?.child.as_ref(),
-        )?))
-    }
-
-    /// maps to BODY[<section>]<<partial>> and BODY.PEEK[<section>]<<partial>>
-    /// peek does not implicitly set the \Seen flag
-    /// eg. BODY[HEADER.FIELDS (DATE FROM)]
-    /// eg. BODY[]<0.2048>
-    fn body_ext<'b>(
-        &self,
-        section: &Option<FetchSection<'b>>,
-        partial: &Option<(u32, NonZeroU32)>,
-        peek: &bool,
-    ) -> Result<(MessageDataItem<'b>, SeenFlag)> {
-        let mut seen = SeenFlag::DoNothing;
-
-        // Extract message section
-        let text = get_message_section(self.content.as_anypart()?, section)?;
-
-        let seen_flag = Flag::Seen.to_string();
-        if !peek && !self.flags.iter().any(|x| *x == seen_flag) {
-            // Add \Seen flag
-            //self.mailbox.add_flags(uuid, &[seen_flag]).await?;
-            seen = SeenFlag::MustAdd;
-        }
-
-        // Handle <<partial>> which cut the message bytes
-        let (text, origin) = apply_partial(partial, &text);
-
-        let data = NString(text.to_vec().try_into().ok().map(IString::Literal));
-
-        return Ok((
-            MessageDataItem::BodyExt {
-                section: section.as_ref().map(|fs| fs.clone()),
-                origin,
-                data,
-            },
-            seen,
-        ));
-    }
-
-    fn internal_date(&self) -> Result<MessageDataItem<'static>> {
-        let dt = Utc
-            .fix()
-            .timestamp_opt(i64::try_from(self.meta.internaldate / 1000)?, 0)
-            .earliest()
-            .ok_or(anyhow!("Unable to parse internal date"))?;
-        Ok(MessageDataItem::InternalDate(DateTime::unvalidated(dt)))
-    }
-
-    fn filter<'b>(&self, ap: &AttributesProxy) -> Result<(Body<'static>, SeenFlag)> {
-        let mut seen = SeenFlag::DoNothing;
-        let res_attrs = ap
-            .attrs
-            .iter()
-            .map(|attr| match attr {
-                MessageDataItemName::Uid => Ok(self.uid()),
-                MessageDataItemName::Flags => Ok(self.flags()),
-                MessageDataItemName::Rfc822Size => Ok(self.rfc_822_size()),
-                MessageDataItemName::Rfc822Header => Ok(self.rfc_822_header()),
-                MessageDataItemName::Rfc822Text => self.rfc_822_text(),
-                MessageDataItemName::Rfc822 => self.rfc822(),
-                MessageDataItemName::Envelope => Ok(self.envelope()),
-                MessageDataItemName::Body => self.body(),
-                MessageDataItemName::BodyStructure => self.body_structure(),
-                MessageDataItemName::BodyExt {
-                    section,
-                    partial,
-                    peek,
-                } => {
-                    let (body, has_seen) = self.body_ext(section, partial, peek)?;
-                    seen = has_seen;
-                    Ok(body)
-                }
-                MessageDataItemName::InternalDate => self.internal_date(),
-            })
-            .collect::<Result<Vec<_>, _>>()?;
-
-        Ok((
-            Body::Data(Data::Fetch {
-                seq: self.ids.i,
-                items: res_attrs.try_into()?,
-            }),
-            seen,
-        ))
-    }
-}
-
-fn apply_partial<'a>(
-    partial: &'_ Option<(u32, NonZeroU32)>,
-    text: &'a [u8],
-) -> (&'a [u8], Option<u32>) {
-    match partial {
-        Some((begin, len)) => {
-            if *begin as usize > text.len() {
-                (&[][..], Some(*begin))
-            } else if (begin + len.get()) as usize >= text.len() {
-                (&text[*begin as usize..], Some(*begin))
-            } else {
-                (
-                    &text[*begin as usize..(begin + len.get()) as usize],
-                    Some(*begin),
-                )
-            }
-        }
-        None => (&text[..], None),
-    }
-}
-
-pub struct BodyIdentifier<'a> {
-    msg_uuid: &'a UniqueIdent,
-    msg_key: &'a Key,
-}
-
-#[derive(Default)]
-pub struct MailSelectionBuilder<'a> {
-    //attrs: AttributeProxy,
-    mail_count: usize,
-    need_body: bool,
-    mi: &'a [MailIdentifiers],
-    meta: &'a [MailMeta],
-    flags: &'a [&'a Vec<String>],
-    bodies: &'a [Vec<u8>],
-}
-
-impl<'a> MailSelectionBuilder<'a> {
-    fn new(need_body: bool, mail_count: usize) -> Self {
-        Self {
-            mail_count,
-            need_body,
-            ..MailSelectionBuilder::default()
-        }
-    }
-
-    fn with_mail_identifiers(&mut self, mi: &'a [MailIdentifiers]) -> &mut Self {
-        self.mi = mi;
-        self
-    }
-
-    fn with_metadata(&mut self, meta: &'a [MailMeta]) -> &mut Self {
-        self.meta = meta;
-        self
-    }
-
-    fn with_flags(&mut self, flags: &'a [&'a Vec<String>]) -> &mut Self {
-        self.flags = flags;
-        self
-    }
-
-    fn bodies_to_collect(&self) -> Vec<BodyIdentifier> {
-        if !self.need_body {
-            return vec![];
-        }
-        zip(self.mi, self.meta)
-            .map(|(mi, meta)| BodyIdentifier {
-                msg_uuid: &mi.uuid,
-                msg_key: &meta.message_key,
-            })
-            .collect::<Vec<_>>()
-    }
-
-    fn with_bodies(&mut self, rbodies: &'a [Vec<u8>]) -> &mut Self {
-        self.bodies = rbodies;
-        self
-    }
-
-    fn build(&self) -> Result<Vec<MailView<'a>>> {
-        let mut bodies = vec![];
-
-        if !self.need_body {
-            for m in self.meta.iter() {
-                let (_, hdrs) =
-                    eml_codec::parse_imf(&m.headers).or(Err(anyhow!("Invalid mail headers")))?;
-                bodies.push(FetchedMail::Partial(hdrs));
-            }
-        } else {
-            for rb in self.bodies.iter() {
-                let (_, p) = eml_codec::parse_message(&rb).or(Err(anyhow!("Invalid mail body")))?;
-                bodies.push(FetchedMail::new_from_message(p));
-            }
-        }
-
-        if self.mi.len() != self.mail_count && self.meta.len() != self.mail_count
-            || self.flags.len() != self.mail_count
-            || bodies.len() != self.mail_count
-        {
-            return Err(anyhow!("Can't build a mail view selection as parts were not correctly registered into the builder."));
-        }
-
-        Ok(zip(self.mi, zip(self.meta, zip(self.flags, bodies)))
-            .map(|(ids, (meta, (flags, content)))| MailView {
-                ids,
-                meta,
-                flags,
-                content,
-            })
-            .collect())
-    }
-}
-
 /// A MailboxView is responsible for giving the client the information
 /// it needs about a mailbox, such as an initial summary of the mailbox's
 /// content and continuous updates indicating when the content
@@ -417,20 +39,12 @@ impl<'a> MailSelectionBuilder<'a> {
 /// To do this, it keeps a variable `known_state` that corresponds to
 /// what the client knows, and produces IMAP messages to be sent to the
 /// client that go along updates to `known_state`.
-pub struct MailboxView {
-    pub(crate) mailbox: Arc<Mailbox>,
-    known_state: UidIndex,
-}
+pub struct MailboxView(pub FrozenMailbox);
 
 impl MailboxView {
     /// Creates a new IMAP view into a mailbox.
     pub async fn new(mailbox: Arc<Mailbox>) -> Self {
-        let state = mailbox.current_uid_index().await;
-
-        Self {
-            mailbox,
-            known_state: state,
-        }
+        Self(mailbox.frozen().await)
     }
 
     /// Create an updated view, useful to make a diff
@@ -440,11 +54,8 @@ impl MailboxView {
     /// This does NOT trigger a sync, it bases itself on what is currently
     /// loaded in RAM by Bayou.
     pub async fn update(&mut self) -> Result<Vec<Body<'static>>> {
-        let old_view: &mut Self = self;
-        let new_view = Self {
-            mailbox: old_view.mailbox.clone(),
-            known_state: old_view.mailbox.current_uid_index().await,
-        };
+        let old_snapshot = self.0.update().await;
+        let new_snapshot = &self.0.snapshot;
 
         let mut data = Vec::<Body>::new();
 
@@ -465,8 +76,8 @@ impl MailboxView {
 
         // - notify client of expunged mails
         let mut n_expunge = 0;
-        for (i, (_uid, uuid)) in old_view.known_state.idx_by_uid.iter().enumerate() {
-            if !new_view.known_state.table.contains_key(uuid) {
+        for (i, (_uid, uuid)) in old_snapshot.idx_by_uid.iter().enumerate() {
+            if !new_snapshot.table.contains_key(uuid) {
                 data.push(Body::Data(Data::Expunge(
                     NonZeroU32::try_from((i + 1 - n_expunge) as u32).unwrap(),
                 )));
@@ -475,21 +86,21 @@ impl MailboxView {
         }
 
         // - if new mails arrived, notify client of number of existing mails
-        if new_view.known_state.table.len() != old_view.known_state.table.len() - n_expunge
-            || new_view.known_state.uidvalidity != old_view.known_state.uidvalidity
+        if new_snapshot.table.len() != old_snapshot.table.len() - n_expunge
+            || new_snapshot.uidvalidity != old_snapshot.uidvalidity
         {
-            data.push(new_view.exists_status()?);
+            data.push(self.exists_status()?);
         }
 
-        if new_view.known_state.uidvalidity != old_view.known_state.uidvalidity {
+        if new_snapshot.uidvalidity != old_snapshot.uidvalidity {
             // TODO: do we want to push less/more info than this?
-            data.push(new_view.uidvalidity_status()?);
-            data.push(new_view.uidnext_status()?);
+            data.push(self.uidvalidity_status()?);
+            data.push(self.uidnext_status()?);
         } else {
             // - if flags changed for existing mails, tell client
-            for (i, (_uid, uuid)) in new_view.known_state.idx_by_uid.iter().enumerate() {
-                let old_mail = old_view.known_state.table.get(uuid);
-                let new_mail = new_view.known_state.table.get(uuid);
+            for (i, (_uid, uuid)) in new_snapshot.idx_by_uid.iter().enumerate() {
+                let old_mail = old_snapshot.table.get(uuid);
+                let new_mail = new_snapshot.table.get(uuid);
                 if old_mail.is_some() && old_mail != new_mail {
                     if let Some((uid, flags)) = new_mail {
                         data.push(Body::Data(Data::Fetch {
@@ -497,7 +108,7 @@ impl MailboxView {
                             items: vec![
                                 MessageDataItem::Uid(*uid),
                                 MessageDataItem::Flags(
-                                    flags.iter().filter_map(|f| string_to_flag(f)).collect(),
+                                    flags.iter().filter_map(|f| flags::from_str(f)).collect(),
                                 ),
                             ]
                             .try_into()?,
@@ -506,7 +117,6 @@ impl MailboxView {
                 }
             }
         }
-        *old_view = new_view;
         Ok(data)
     }
 
@@ -532,21 +142,21 @@ impl MailboxView {
         flags: &[Flag<'a>],
         is_uid_store: &bool,
     ) -> Result<Vec<Body<'static>>> {
-        self.mailbox.opportunistic_sync().await?;
+        self.0.sync().await?;
 
         let flags = flags.iter().map(|x| x.to_string()).collect::<Vec<_>>();
 
-        let mails = self.get_mail_ids(sequence_set, *is_uid_store)?;
+        let mails = self.index().fetch(sequence_set, *is_uid_store)?;
         for mi in mails.iter() {
             match kind {
                 StoreType::Add => {
-                    self.mailbox.add_flags(mi.uuid, &flags[..]).await?;
+                    self.0.mailbox.add_flags(mi.uuid, &flags[..]).await?;
                 }
                 StoreType::Remove => {
-                    self.mailbox.del_flags(mi.uuid, &flags[..]).await?;
+                    self.0.mailbox.del_flags(mi.uuid, &flags[..]).await?;
                 }
                 StoreType::Replace => {
-                    self.mailbox.set_flags(mi.uuid, &flags[..]).await?;
+                    self.0.mailbox.set_flags(mi.uuid, &flags[..]).await?;
                 }
             }
         }
@@ -556,10 +166,10 @@ impl MailboxView {
     }
 
     pub async fn expunge(&mut self) -> Result<Vec<Body<'static>>> {
-        self.mailbox.opportunistic_sync().await?;
+        self.0.sync().await?;
+        let state = self.0.peek().await;
 
         let deleted_flag = Flag::Deleted.to_string();
-        let state = self.mailbox.current_uid_index().await;
         let msgs = state
             .table
             .iter()
@@ -567,7 +177,7 @@ impl MailboxView {
             .map(|(uuid, _)| *uuid);
 
         for msg in msgs {
-            self.mailbox.delete(msg).await?;
+            self.0.mailbox.delete(msg).await?;
         }
 
         self.update().await
@@ -579,11 +189,11 @@ impl MailboxView {
         to: Arc<Mailbox>,
         is_uid_copy: &bool,
     ) -> Result<(ImapUidvalidity, Vec<(ImapUid, ImapUid)>)> {
-        let mails = self.get_mail_ids(sequence_set, *is_uid_copy)?;
+        let mails = self.index().fetch(sequence_set, *is_uid_copy)?;
 
         let mut new_uuids = vec![];
         for mi in mails.iter() {
-            new_uuids.push(to.copy_from(&self.mailbox, mi.uuid).await?);
+            new_uuids.push(to.copy_from(&self.0.mailbox, mi.uuid).await?);
         }
 
         let mut ret = vec![];
@@ -606,21 +216,18 @@ impl MailboxView {
         to: Arc<Mailbox>,
         is_uid_copy: &bool,
     ) -> Result<(ImapUidvalidity, Vec<(ImapUid, ImapUid)>, Vec<Body<'static>>)> {
-        let mails = self.get_mail_ids(sequence_set, *is_uid_copy)?;
+        let mails = self.index().fetch(sequence_set, *is_uid_copy)?;
 
-        let mut new_uuids = vec![];
         for mi in mails.iter() {
-            let copy_action = to.copy_from(&self.mailbox, mi.uuid).await?;
-            new_uuids.push(copy_action);
-            self.mailbox.delete(mi.uuid).await?
+            to.move_from(&self.0.mailbox, mi.uuid).await?;
         }
 
         let mut ret = vec![];
         let to_state = to.current_uid_index().await;
-        for (mi, new_uuid) in mails.iter().zip(new_uuids.iter()) {
+        for mi in mails.iter() {
             let dest_uid = to_state
                 .table
-                .get(new_uuid)
+                .get(&mi.uuid)
                 .ok_or(anyhow!("moved mail not in destination mailbox"))?
                 .0;
             ret.push((mi.uid, dest_uid));
@@ -639,152 +246,100 @@ impl MailboxView {
         attributes: &'b MacroOrMessageDataItemNames<'static>,
         is_uid_fetch: &bool,
     ) -> Result<Vec<Body<'static>>> {
+        // [1/6] Pre-compute data
+        //  a. what are the uuids of the emails we want?
+        //  b. do we need to fetch the full body?
         let ap = AttributesProxy::new(attributes, *is_uid_fetch);
+        let query_scope = match ap.need_body() {
+            true => QueryScope::Full,
+            _ => QueryScope::Partial,
+        };
+        let mail_idx_list = self.index().fetch(sequence_set, *is_uid_fetch)?;
 
-        // Prepare data
-        let mids = MailIdentifiersList(self.get_mail_ids(sequence_set, *is_uid_fetch)?);
-        let mail_count = mids.0.len();
-        let uuids = mids.uuids();
-        let meta = self.mailbox.fetch_meta(&uuids).await?;
-        let flags = uuids
+        // [2/6] Fetch the emails
+        let uuids = mail_idx_list
             .iter()
-            .map(|uuid| {
-                self.known_state
-                    .table
-                    .get(uuid)
-                    .map(|(_uuid, f)| f)
-                    .ok_or(anyhow!("missing email from the flag table"))
-            })
-            .collect::<Result<Vec<_>, _>>()?;
-
-        // Start filling data to build the view
-        let mut selection = MailSelectionBuilder::new(ap.need_body(), mail_count);
-        selection
-            .with_mail_identifiers(&mids.0)
-            .with_metadata(&meta)
-            .with_flags(&flags);
+            .map(|midx| midx.uuid)
+            .collect::<Vec<_>>();
+        let query_result = self.0.query(&uuids, query_scope).fetch().await?;
 
-        // Asynchronously fetch full bodies (if needed)
-        let btc = selection.bodies_to_collect();
-        let future_bodies = btc
+        // [3/6] Derive an IMAP-specific view from the results, apply the filters
+        let views = query_result
             .iter()
-            .map(|bi| async move {
-                let body = self.mailbox.fetch_full(*bi.msg_uuid, bi.msg_key).await?;
-                Ok::<_, anyhow::Error>(body)
-            })
-            .collect::<FuturesOrdered<_>>();
-        let bodies = future_bodies
-            .collect::<Vec<_>>()
-            .await
-            .into_iter()
+            .zip(mail_idx_list.into_iter())
+            .map(|(qr, midx)| MailView::new(qr, midx))
             .collect::<Result<Vec<_>, _>>()?;
 
-        // Add bodies
-        selection.with_bodies(bodies.as_slice());
-
-        // Build mail selection views
-        let views = selection.build()?;
-
-        // Filter views to build the result
-        // Also identify what must be put as seen
-        let filtered_view = views
+        // [4/6] Apply the IMAP transformation, bubble up any error
+        // We get 2 results:
+        //   - The one we send to the client
+        //   - The \Seen flags we must set internally
+        let (flag_mgmt, imap_ret): (Vec<_>, Vec<_>) = views
             .iter()
-            .filter_map(|mv| mv.filter(&ap).ok().map(|(body, seen)| (mv, body, seen)))
-            .collect::<Vec<_>>();
-        // Register seen flags
-        let future_flags = filtered_view
+            .map(|mv| mv.filter(&ap).map(|(body, seen)| ((mv, seen), body)))
+            .collect::<Result<Vec<_>, _>>()?
+            .into_iter()
+            .unzip();
+
+        // [5/6] Register the \Seen flags
+        flag_mgmt
             .iter()
-            .filter(|(_mv, _body, seen)| matches!(seen, SeenFlag::MustAdd))
-            .map(|(mv, _body, _seen)| async move {
+            .filter(|(_mv, seen)| matches!(seen, SeenFlag::MustAdd))
+            .map(|(mv, _seen)| async move {
                 let seen_flag = Flag::Seen.to_string();
-                self.mailbox.add_flags(mv.ids.uuid, &[seen_flag]).await?;
+                self.0
+                    .mailbox
+                    .add_flags(*mv.query_result.uuid(), &[seen_flag])
+                    .await?;
                 Ok::<_, anyhow::Error>(())
             })
-            .collect::<FuturesOrdered<_>>();
-
-        future_flags
+            .collect::<FuturesOrdered<_>>()
             .collect::<Vec<_>>()
             .await
             .into_iter()
             .collect::<Result<_, _>>()?;
 
-        let command_body = filtered_view
-            .into_iter()
-            .map(|(_mv, body, _seen)| body)
-            .collect::<Vec<_>>();
-
-        Ok(command_body)
+        // [6/6] Build the final result that will be sent to the client.
+        Ok(imap_ret)
     }
 
-    // ----
-
-    // Gets the IMAP ID, the IMAP UIDs and, the Aerogramme UUIDs of mails identified by a SequenceSet of
-    // sequence numbers (~ IMAP selector)
-    fn get_mail_ids(
+    /// A naive search implementation...
+    pub async fn search<'a>(
         &self,
-        sequence_set: &SequenceSet,
-        by_uid: bool,
-    ) -> Result<Vec<MailIdentifiers>> {
-        let mail_vec = self
-            .known_state
-            .idx_by_uid
-            .iter()
-            .map(|(uid, uuid)| (*uid, *uuid))
-            .collect::<Vec<_>>();
+        _charset: &Option<Charset<'a>>,
+        search_key: &SearchKey<'a>,
+        uid: bool,
+    ) -> Result<Vec<Body<'static>>> {
+        // 1. Compute the subset of sequence identifiers we need to fetch
+        // based on the search query
+        let crit = search::Criteria(search_key);
+        let (seq_set, seq_type) = crit.to_sequence_set();
 
-        let mut mails = vec![];
+        // 2. Get the selection
+        let selection = self.index().fetch(&seq_set, seq_type.is_uid())?;
 
-        if by_uid {
-            if mail_vec.is_empty() {
-                return Ok(vec![]);
-            }
-            let iter_strat = sequence::Strategy::Naive {
-                largest: mail_vec.last().unwrap().0,
-            };
-
-            let mut i = 0;
-            for uid in sequence_set.iter(iter_strat) {
-                while mail_vec.get(i).map(|mail| mail.0 < uid).unwrap_or(false) {
-                    i += 1;
-                }
-                if let Some(mail) = mail_vec.get(i) {
-                    if mail.0 == uid {
-                        mails.push(MailIdentifiers {
-                            i: NonZeroU32::try_from(i as u32 + 1).unwrap(),
-                            uid: mail.0,
-                            uuid: mail.1,
-                        });
-                    }
-                } else {
-                    break;
-                }
-            }
-        } else {
-            if mail_vec.is_empty() {
-                bail!("No such message (mailbox is empty)");
-            }
+        // 3. Filter the selection based on the ID / UID / Flags
 
-            let iter_strat = sequence::Strategy::Naive {
-                largest: NonZeroU32::try_from((mail_vec.len()) as u32).unwrap(),
-            };
-
-            for i in sequence_set.iter(iter_strat) {
-                if let Some(mail) = mail_vec.get(i.get() as usize - 1) {
-                    mails.push(MailIdentifiers {
-                        i,
-                        uid: mail.0,
-                        uuid: mail.1,
-                    });
-                } else {
-                    bail!("No such mail: {}", i);
-                }
-            }
-        }
+        // 4. If needed, filter the selection based on the metadata
+        let _need_meta = crit.need_meta();
 
-        Ok(mails)
+        // 5. If needed, filter the selection based on the body
+        let _need_body = crit.need_body();
+
+        // 6. Format the result according to the client's taste:
+        // either return UID or ID.
+        let selection_fmt = match uid {
+            true => selection.into_iter().map(|in_idx| in_idx.uid).collect(),
+            _ => selection.into_iter().map(|in_idx| in_idx.i).collect(),
+        };
+
+        Ok(vec![Body::Data(Data::Search(selection_fmt))])
     }
 
     // ----
+    fn index<'a>(&'a self) -> Index<'a> {
+        Index(&self.0.snapshot)
+    }
 
     /// Produce an OK [UIDVALIDITY _] message corresponding to `known_state`
     fn uidvalidity_status(&self) -> Result<Body<'static>> {
@@ -798,7 +353,7 @@ impl MailboxView {
     }
 
     pub(crate) fn uidvalidity(&self) -> ImapUidvalidity {
-        self.known_state.uidvalidity
+        self.0.snapshot.uidvalidity
     }
 
     /// Produce an OK [UIDNEXT _] message corresponding to `known_state`
@@ -813,7 +368,7 @@ impl MailboxView {
     }
 
     pub(crate) fn uidnext(&self) -> ImapUid {
-        self.known_state.uidnext
+        self.0.snapshot.uidnext
     }
 
     /// Produce an EXISTS message corresponding to the number of mails
@@ -823,7 +378,7 @@ impl MailboxView {
     }
 
     pub(crate) fn exists(&self) -> Result<u32> {
-        Ok(u32::try_from(self.known_state.idx_by_uid.len())?)
+        Ok(u32::try_from(self.0.snapshot.idx_by_uid.len())?)
     }
 
     /// Produce a RECENT message corresponding to the number of
@@ -834,7 +389,8 @@ impl MailboxView {
 
     pub(crate) fn recent(&self) -> Result<u32> {
         let recent = self
-            .known_state
+            .0
+            .snapshot
             .idx_by_flag
             .get(&"\\Recent".to_string())
             .map(|os| os.len())
@@ -850,10 +406,11 @@ impl MailboxView {
         // 1. Collecting all the possible flags in the mailbox
         // 1.a Fetch them from our index
         let mut known_flags: Vec<Flag> = self
-            .known_state
+            .0
+            .snapshot
             .idx_by_flag
             .flags()
-            .filter_map(|f| match string_to_flag(f) {
+            .filter_map(|f| match flags::from_str(f) {
                 Some(FlagFetch::Flag(fl)) => Some(fl),
                 _ => None,
             })
@@ -889,9 +446,10 @@ impl MailboxView {
     }
 
     pub(crate) fn unseen_count(&self) -> usize {
-        let total = self.known_state.table.len();
+        let total = self.0.snapshot.table.len();
         let seen = self
-            .known_state
+            .0
+            .snapshot
             .idx_by_flag
             .get(&Flag::Seen.to_string())
             .map(|x| x.len())
@@ -900,456 +458,25 @@ impl MailboxView {
     }
 }
 
-fn string_to_flag(f: &str) -> Option<FlagFetch<'static>> {
-    match f.chars().next() {
-        Some('\\') => match f {
-            "\\Seen" => Some(FlagFetch::Flag(Flag::Seen)),
-            "\\Answered" => Some(FlagFetch::Flag(Flag::Answered)),
-            "\\Flagged" => Some(FlagFetch::Flag(Flag::Flagged)),
-            "\\Deleted" => Some(FlagFetch::Flag(Flag::Deleted)),
-            "\\Draft" => Some(FlagFetch::Flag(Flag::Draft)),
-            "\\Recent" => Some(FlagFetch::Recent),
-            _ => match Atom::try_from(f.strip_prefix('\\').unwrap().to_string()) {
-                Err(_) => {
-                    tracing::error!(flag=%f, "Unable to encode flag as IMAP atom");
-                    None
-                }
-                Ok(a) => Some(FlagFetch::Flag(Flag::system(a))),
-            },
-        },
-        Some(_) => match Atom::try_from(f.to_string()) {
-            Err(_) => {
-                tracing::error!(flag=%f, "Unable to encode flag as IMAP atom");
-                None
-            }
-            Ok(a) => Some(FlagFetch::Flag(Flag::keyword(a))),
-        },
-        None => None,
-    }
-}
-
-/// Envelope rules are defined in RFC 3501, section 7.4.2
-/// https://datatracker.ietf.org/doc/html/rfc3501#section-7.4.2
-///
-/// Some important notes:
-///
-/// If the Sender or Reply-To lines are absent in the [RFC-2822]
-/// header, or are present but empty, the server sets the
-/// corresponding member of the envelope to be the same value as
-/// the from member (the client is not expected to know to do
-/// this). Note: [RFC-2822] requires that all messages have a valid
-/// From header.  Therefore, the from, sender, and reply-to
-/// members in the envelope can not be NIL.
-///
-/// If the Date, Subject, In-Reply-To, and Message-ID header lines
-/// are absent in the [RFC-2822] header, the corresponding member
-/// of the envelope is NIL; if these header lines are present but
-/// empty the corresponding member of the envelope is the empty
-/// string.
-
-//@FIXME return an error if the envelope is invalid instead of panicking
-//@FIXME some fields must be defaulted if there are not set.
-fn message_envelope(msg: &imf::Imf) -> Envelope<'static> {
-    let from = msg.from.iter().map(convert_mbx).collect::<Vec<_>>();
-
-    Envelope {
-        date: NString(
-            msg.date
-                .as_ref()
-                .map(|d| IString::try_from(d.to_rfc3339()).unwrap()),
-        ),
-        subject: NString(
-            msg.subject
-                .as_ref()
-                .map(|d| IString::try_from(d.to_string()).unwrap()),
-        ),
-        sender: msg
-            .sender
-            .as_ref()
-            .map(|v| vec![convert_mbx(v)])
-            .unwrap_or(from.clone()),
-        reply_to: if msg.reply_to.is_empty() {
-            from.clone()
-        } else {
-            convert_addresses(&msg.reply_to)
-        },
-        from,
-        to: convert_addresses(&msg.to),
-        cc: convert_addresses(&msg.cc),
-        bcc: convert_addresses(&msg.bcc),
-        in_reply_to: NString(
-            msg.in_reply_to
-                .iter()
-                .next()
-                .map(|d| IString::try_from(d.to_string()).unwrap()),
-        ),
-        message_id: NString(
-            msg.msg_id
-                .as_ref()
-                .map(|d| IString::try_from(d.to_string()).unwrap()),
-        ),
-    }
-}
-
-fn convert_addresses(addrlist: &Vec<imf::address::AddressRef>) -> Vec<Address<'static>> {
-    let mut acc = vec![];
-    for item in addrlist {
-        match item {
-            imf::address::AddressRef::Single(a) => acc.push(convert_mbx(a)),
-            imf::address::AddressRef::Many(l) => acc.extend(l.participants.iter().map(convert_mbx)),
-        }
-    }
-    return acc;
-}
-
-fn convert_mbx(addr: &imf::mailbox::MailboxRef) -> Address<'static> {
-    Address {
-        name: NString(
-            addr.name
-                .as_ref()
-                .map(|x| IString::try_from(x.to_string()).unwrap()),
-        ),
-        // SMTP at-domain-list (source route) seems obsolete since at least 1991
-        // https://www.mhonarc.org/archive/html/ietf-822/1991-06/msg00060.html
-        adl: NString(None),
-        mailbox: NString(Some(
-            IString::try_from(addr.addrspec.local_part.to_string()).unwrap(),
-        )),
-        host: NString(Some(
-            IString::try_from(addr.addrspec.domain.to_string()).unwrap(),
-        )),
-    }
-}
-
-/*
---CAPTURE--
-b fetch 29878:29879 (BODY)
-* 29878 FETCH (BODY (("text" "plain" ("charset" "utf-8") NIL NIL "quoted-printable" 3264 82)("text" "html" ("charset" "utf-8") NIL NIL "quoted-printable" 31834 643) "alternative"))
-* 29879 FETCH (BODY ("text" "html" ("charset" "us-ascii") NIL NIL "7bit" 4107 131))
-                                   ^^^^^^^^^^^^^^^^^^^^^^ ^^^ ^^^ ^^^^^^ ^^^^ ^^^
-                                   |                      |   |   |      |    | number of lines
-                                   |                      |   |   |      | size
-                                   |                      |   |   | content transfer encoding
-                                   |                      |   | description
-                                   |                      | id
-                                   | parameter list
-b OK Fetch completed (0.001 + 0.000 secs).
-*/
-
-fn build_imap_email_struct<'a>(part: &AnyPart<'a>) -> Result<BodyStructure<'static>> {
-    match part {
-        AnyPart::Mult(x) => {
-            let itype = &x.mime.interpreted_type;
-            let subtype = IString::try_from(itype.subtype.to_string())
-                .unwrap_or(unchecked_istring("alternative"));
-
-            let inner_bodies = x
-                .children
-                .iter()
-                .filter_map(|inner| build_imap_email_struct(&inner).ok())
-                .collect::<Vec<_>>();
-            NonEmptyVec::validate(&inner_bodies)?;
-            let bodies = NonEmptyVec::unvalidated(inner_bodies);
-
-            Ok(BodyStructure::Multi {
-                bodies,
-                subtype,
-                extension_data: None,
-                /*Some(MultipartExtensionData {
-                    parameter_list: vec![],
-                    disposition: None,
-                    language: None,
-                    location: None,
-                    extension: vec![],
-                })*/
-            })
-        }
-        AnyPart::Txt(x) => {
-            let mut basic = basic_fields(&x.mime.fields, x.body.len())?;
-
-            // Get the interpreted content type, set it
-            let itype = match &x.mime.interpreted_type {
-                Deductible::Inferred(v) | Deductible::Explicit(v) => v,
-            };
-            let subtype =
-                IString::try_from(itype.subtype.to_string()).unwrap_or(unchecked_istring("plain"));
-
-            // Add charset to the list of parameters if we know it has been inferred as it will be
-            // missing from the parsed content.
-            if let Deductible::Inferred(charset) = &itype.charset {
-                basic.parameter_list.push((
-                    unchecked_istring("charset"),
-                    IString::try_from(charset.to_string()).unwrap_or(unchecked_istring("us-ascii")),
-                ));
-            }
-
-            Ok(BodyStructure::Single {
-                body: FetchBody {
-                    basic,
-                    specific: SpecificFields::Text {
-                        subtype,
-                        number_of_lines: nol(x.body),
-                    },
-                },
-                extension_data: None,
-            })
-        }
-        AnyPart::Bin(x) => {
-            let basic = basic_fields(&x.mime.fields, x.body.len())?;
-
-            let default = mime::r#type::NaiveType {
-                main: &b"application"[..],
-                sub: &b"octet-stream"[..],
-                params: vec![],
-            };
-            let ct = x.mime.fields.ctype.as_ref().unwrap_or(&default);
-
-            let r#type =
-                IString::try_from(String::from_utf8_lossy(ct.main).to_string()).or(Err(
-                    anyhow!("Unable to build IString from given Content-Type type given"),
-                ))?;
-
-            let subtype =
-                IString::try_from(String::from_utf8_lossy(ct.sub).to_string()).or(Err(anyhow!(
-                    "Unable to build IString from given Content-Type subtype given"
-                )))?;
-
-            Ok(BodyStructure::Single {
-                body: FetchBody {
-                    basic,
-                    specific: SpecificFields::Basic { r#type, subtype },
-                },
-                extension_data: None,
-            })
-        }
-        AnyPart::Msg(x) => {
-            let basic = basic_fields(&x.mime.fields, x.raw_part.len())?;
-
-            Ok(BodyStructure::Single {
-                body: FetchBody {
-                    basic,
-                    specific: SpecificFields::Message {
-                        envelope: Box::new(message_envelope(&x.imf)),
-                        body_structure: Box::new(build_imap_email_struct(x.child.as_ref())?),
-                        number_of_lines: nol(x.raw_part),
-                    },
-                },
-                extension_data: None,
-            })
-        }
-    }
-}
-
-fn nol(input: &[u8]) -> u32 {
-    input
-        .iter()
-        .filter(|x| **x == b'\n')
-        .count()
-        .try_into()
-        .unwrap_or(0)
-}
-
-/// s is set to static to ensure that only compile time values
-/// checked by developpers are passed.
-fn unchecked_istring(s: &'static str) -> IString {
-    IString::try_from(s).expect("this value is expected to be a valid imap-codec::IString")
-}
-
-fn basic_fields(m: &mime::NaiveMIME, sz: usize) -> Result<BasicFields<'static>> {
-    let parameter_list = m
-        .ctype
-        .as_ref()
-        .map(|x| {
-            x.params
-                .iter()
-                .map(|p| {
-                    (
-                        IString::try_from(String::from_utf8_lossy(p.name).to_string()),
-                        IString::try_from(p.value.to_string()),
-                    )
-                })
-                .filter(|(k, v)| k.is_ok() && v.is_ok())
-                .map(|(k, v)| (k.unwrap(), v.unwrap()))
-                .collect()
-        })
-        .unwrap_or(vec![]);
-
-    Ok(BasicFields {
-        parameter_list,
-        id: NString(
-            m.id.as_ref()
-                .and_then(|ci| IString::try_from(ci.to_string()).ok()),
-        ),
-        description: NString(
-            m.description
-                .as_ref()
-                .and_then(|cd| IString::try_from(cd.to_string()).ok()),
-        ),
-        content_transfer_encoding: match m.transfer_encoding {
-            mime::mechanism::Mechanism::_8Bit => unchecked_istring("8bit"),
-            mime::mechanism::Mechanism::Binary => unchecked_istring("binary"),
-            mime::mechanism::Mechanism::QuotedPrintable => unchecked_istring("quoted-printable"),
-            mime::mechanism::Mechanism::Base64 => unchecked_istring("base64"),
-            _ => unchecked_istring("7bit"),
-        },
-        // @FIXME we can't compute the size of the message currently...
-        size: u32::try_from(sz)?,
-    })
-}
-
-/// Extract message section for section identifier passed by the FETCH BODY[<section>]<<partial>>
-/// request
-///
-/// Example of message sections:
-///
-/// ```
-///    HEADER     ([RFC-2822] header of the message)
-///    TEXT       ([RFC-2822] text body of the message) MULTIPART/MIXED
-///    1          TEXT/PLAIN
-///    2          APPLICATION/OCTET-STREAM
-///    3          MESSAGE/RFC822
-///    3.HEADER   ([RFC-2822] header of the message)
-///    3.TEXT     ([RFC-2822] text body of the message) MULTIPART/MIXED
-///    3.1        TEXT/PLAIN
-///    3.2        APPLICATION/OCTET-STREAM
-///    4          MULTIPART/MIXED
-///    4.1        IMAGE/GIF
-///    4.1.MIME   ([MIME-IMB] header for the IMAGE/GIF)
-///    4.2        MESSAGE/RFC822
-///    4.2.HEADER ([RFC-2822] header of the message)
-///    4.2.TEXT   ([RFC-2822] text body of the message) MULTIPART/MIXED
-///    4.2.1      TEXT/PLAIN
-///    4.2.2      MULTIPART/ALTERNATIVE
-///    4.2.2.1    TEXT/PLAIN
-///    4.2.2.2    TEXT/RICHTEXT
-/// ```
-fn get_message_section<'a>(
-    parsed: &'a AnyPart<'a>,
-    section: &Option<FetchSection>,
-) -> Result<Cow<'a, [u8]>> {
-    let msg = parsed
-        .as_message()
-        .ok_or(anyhow!("Part must be a message"))?;
-    match section {
-        Some(FetchSection::Text(None)) => Ok(msg.raw_body.into()),
-        Some(FetchSection::Text(Some(part))) => map_subpart(parsed, part.0.as_ref(), |part_msg| {
-            Ok(part_msg
-                .as_message()
-                .ok_or(Error::msg(
-                    "Not a message/rfc822 part while expected by request (TEXT)",
-                ))?
-                .raw_body
-                .into())
-        }),
-        Some(FetchSection::Header(part)) => map_subpart(
-            parsed,
-            part.as_ref().map(|p| p.0.as_ref()).unwrap_or(&[]),
-            |part_msg| {
-                Ok(part_msg
-                    .as_message()
-                    .ok_or(Error::msg(
-                        "Not a message/rfc822 part while expected by request (HEADER)",
-                    ))?
-                    .raw_headers
-                    .into())
-            },
-        ),
-        Some(
-            FetchSection::HeaderFields(part, fields) | FetchSection::HeaderFieldsNot(part, fields),
-        ) => {
-            let invert = matches!(section, Some(FetchSection::HeaderFieldsNot(_, _)));
-            let fields = fields
-                .as_ref()
-                .iter()
-                .map(|x| match x {
-                    AString::Atom(a) => a.inner().as_bytes(),
-                    AString::String(IString::Literal(l)) => l.as_ref(),
-                    AString::String(IString::Quoted(q)) => q.inner().as_bytes(),
-                })
-                .collect::<Vec<_>>();
-
-            map_subpart(
-                parsed,
-                part.as_ref().map(|p| p.0.as_ref()).unwrap_or(&[]),
-                |part_msg| {
-                    let mut ret = vec![];
-                    let mime = match &part_msg {
-                        AnyPart::Msg(msg) => msg.child.mime(),
-                        other => other.mime(),
-                    };
-                    for f in mime.kv.iter() {
-                        let (k, v) = match f {
-                            header::Field::Good(header::Kv2(k, v)) => (k, v),
-                            _ => continue,
-                        };
-                        if fields.as_slice().iter().any(|x| (x == k) ^ invert) {
-                            ret.extend(*k);
-                            ret.extend(b": ");
-                            ret.extend(*v);
-                            ret.extend(b"\r\n");
-                        }
-                    }
-                    ret.extend(b"\r\n");
-                    Ok(ret.into())
-                },
-            )
-        }
-        Some(FetchSection::Part(part)) => map_subpart(parsed, part.0.as_ref(), |part| {
-            let bytes = match &part {
-                AnyPart::Txt(p) => p.body,
-                AnyPart::Bin(p) => p.body,
-                AnyPart::Msg(p) => p.raw_part,
-                AnyPart::Mult(_) => bail!("Multipart part has no body"),
-            };
-            Ok(bytes.to_vec().into())
-        }),
-        Some(FetchSection::Mime(part)) => map_subpart(parsed, part.0.as_ref(), |part| {
-            let bytes = match &part {
-                AnyPart::Txt(p) => p.mime.fields.raw,
-                AnyPart::Bin(p) => p.mime.fields.raw,
-                AnyPart::Msg(p) => p.child.mime().raw,
-                AnyPart::Mult(p) => p.mime.fields.raw,
-            };
-            Ok(bytes.to_vec().into())
-        }),
-        None => Ok(msg.raw_part.into()),
-    }
-}
-
-/// Fetch a MIME SubPart
-///
-/// eg. FETCH BODY[4.2.2.1] -> [4, 2, 2, 1]
-fn map_subpart<'a, F, R>(part: &AnyPart<'a>, path: &[NonZeroU32], f: F) -> Result<R>
-where
-    F: FnOnce(&AnyPart<'a>) -> Result<R>,
-{
-    if path.is_empty() {
-        f(part)
-    } else {
-        match part {
-            AnyPart::Mult(x) => map_subpart(
-                x.children
-                    .get(path[0].get() as usize - 1)
-                    .ok_or(anyhow!("Unable to resolve subpath {:?}, current multipart has only {} elements", path, x.children.len()))?,
-                &path[1..],
-                f),
-            AnyPart::Msg(x) => map_subpart(x.child.as_ref(), path, f),
-            _ => bail!("You tried to access a subpart on an atomic part (text or binary). Unresolved subpath {:?}", path),
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::cryptoblob;
-    use crate::mail::unique_ident;
     use imap_codec::encode::Encoder;
+    use imap_codec::imap_types::core::NonEmptyVec;
     use imap_codec::imap_types::fetch::Section;
+    use imap_codec::imap_types::fetch::{MacroOrMessageDataItemNames, MessageDataItemName};
     use imap_codec::imap_types::response::Response;
     use imap_codec::ResponseCodec;
     use std::fs;
 
+    use crate::cryptoblob;
+    use crate::imap::index::MailIndex;
+    use crate::imap::mail_view::MailView;
+    use crate::imap::mime_view;
+    use crate::mail::mailbox::MailMeta;
+    use crate::mail::query::QueryResult;
+    use crate::mail::unique_ident;
+
     #[test]
     fn mailview_body_ext() -> Result<()> {
         let ap = AttributesProxy::new(
@@ -1363,7 +490,6 @@ mod tests {
             false,
         );
 
-        let flags = vec![];
         let key = cryptoblob::gen_key();
         let meta = MailMeta {
             internaldate: 0u64,
@@ -1371,20 +497,23 @@ mod tests {
             message_key: key,
             rfc822_size: 8usize,
         };
-        let ids = MailIdentifiers {
+
+        let index_entry = (NonZeroU32::MIN, vec![]);
+        let mail_in_idx = MailIndex {
             i: NonZeroU32::MIN,
-            uid: NonZeroU32::MIN,
+            uid: index_entry.0,
             uuid: unique_ident::gen_ident(),
+            flags: &index_entry.1,
         };
         let rfc822 = b"Subject: hello\r\nFrom: a@a.a\r\nTo: b@b.b\r\nDate: Thu, 12 Oct 2023 08:45:28 +0000\r\n\r\nhello world";
-        let content = FetchedMail::new_from_message(eml_codec::parse_message(rfc822)?.1);
-
-        let mv = MailView {
-            ids: &ids,
-            content,
-            meta: &meta,
-            flags: &flags,
+        let qr = QueryResult::FullResult {
+            uuid: mail_in_idx.uuid.clone(),
+            index: &index_entry,
+            metadata: meta,
+            content: rfc822.to_vec(),
         };
+
+        let mv = MailView::new(&qr, mail_in_idx)?;
         let (res_body, _seen) = mv.filter(&ap)?;
 
         let fattr = match res_body {
@@ -1452,7 +581,7 @@ mod tests {
 
             let test_repr = Response::Data(Data::Fetch {
                 seq: NonZeroU32::new(1).unwrap(),
-                items: NonEmptyVec::from(MessageDataItem::Body(build_imap_email_struct(
+                items: NonEmptyVec::from(MessageDataItem::Body(mime_view::bodystructure(
                     &message.child,
                 )?)),
             });
diff --git a/src/imap/mime_view.rs b/src/imap/mime_view.rs
new file mode 100644
index 0000000..1f36c47
--- /dev/null
+++ b/src/imap/mime_view.rs
@@ -0,0 +1,538 @@
+use std::borrow::Cow;
+use std::collections::HashSet;
+use std::num::NonZeroU32;
+
+use anyhow::{anyhow, bail, Result};
+
+use imap_codec::imap_types::body::{BasicFields, Body as FetchBody, BodyStructure, SpecificFields};
+use imap_codec::imap_types::core::{AString, IString, NString, NonEmptyVec};
+use imap_codec::imap_types::fetch::{Part as FetchPart, Section as FetchSection};
+
+use eml_codec::{
+    header, mime, mime::r#type::Deductible, part::composite, part::discrete, part::AnyPart,
+};
+
+use crate::imap::imf_view::message_envelope;
+
+pub enum BodySection<'a> {
+    Full(Cow<'a, [u8]>),
+    Slice {
+        body: Cow<'a, [u8]>,
+        origin_octet: u32,
+    },
+}
+
+/// Logic for BODY[<section>]<<partial>>
+/// Works in 3 times:
+///  1. Find the section (RootMime::subset)
+///  2. Apply the extraction logic (SelectedMime::extract), like TEXT, HEADERS, etc.
+///  3. Keep only the given subset provided by partial
+///
+/// Example of message sections:
+///
+/// ```
+///    HEADER     ([RFC-2822] header of the message)
+///    TEXT       ([RFC-2822] text body of the message) MULTIPART/MIXED
+///    1          TEXT/PLAIN
+///    2          APPLICATION/OCTET-STREAM
+///    3          MESSAGE/RFC822
+///    3.HEADER   ([RFC-2822] header of the message)
+///    3.TEXT     ([RFC-2822] text body of the message) MULTIPART/MIXED
+///    3.1        TEXT/PLAIN
+///    3.2        APPLICATION/OCTET-STREAM
+///    4          MULTIPART/MIXED
+///    4.1        IMAGE/GIF
+///    4.1.MIME   ([MIME-IMB] header for the IMAGE/GIF)
+///    4.2        MESSAGE/RFC822
+///    4.2.HEADER ([RFC-2822] header of the message)
+///    4.2.TEXT   ([RFC-2822] text body of the message) MULTIPART/MIXED
+///    4.2.1      TEXT/PLAIN
+///    4.2.2      MULTIPART/ALTERNATIVE
+///    4.2.2.1    TEXT/PLAIN
+///    4.2.2.2    TEXT/RICHTEXT
+/// ```
+pub fn body_ext<'a>(
+    part: &'a AnyPart<'a>,
+    section: &'a Option<FetchSection<'a>>,
+    partial: &'a Option<(u32, NonZeroU32)>,
+) -> Result<BodySection<'a>> {
+    let root_mime = NodeMime(part);
+    let (extractor, path) = SubsettedSection::from(section);
+    let selected_mime = root_mime.subset(path)?;
+    let extracted_full = selected_mime.extract(&extractor)?;
+    Ok(extracted_full.to_body_section(partial))
+}
+
+/// Logic for BODY and BODYSTRUCTURE
+///
+/// ```raw
+/// b fetch 29878:29879 (BODY)
+/// * 29878 FETCH (BODY (("text" "plain" ("charset" "utf-8") NIL NIL "quoted-printable" 3264 82)("text" "html" ("charset" "utf-8") NIL NIL "quoted-printable" 31834 643) "alternative"))
+/// * 29879 FETCH (BODY ("text" "html" ("charset" "us-ascii") NIL NIL "7bit" 4107 131))
+///                                   ^^^^^^^^^^^^^^^^^^^^^^ ^^^ ^^^ ^^^^^^ ^^^^ ^^^
+///                                   |                      |   |   |      |    | number of lines
+///                                   |                      |   |   |      | size
+///                                   |                      |   |   | content transfer encoding
+///                                   |                      |   | description
+///                                   |                      | id
+///                                   | parameter list
+/// b OK Fetch completed (0.001 + 0.000 secs).
+/// ```
+pub fn bodystructure(part: &AnyPart) -> Result<BodyStructure<'static>> {
+    NodeMime(part).structure()
+}
+
+/// NodeMime
+///
+/// Used for recursive logic on MIME.
+/// See SelectedMime for inspection.
+struct NodeMime<'a>(&'a AnyPart<'a>);
+impl<'a> NodeMime<'a> {
+    /// A MIME object is a tree of elements.
+    /// The path indicates which element must be picked.
+    /// This function returns the picked element as the new view
+    fn subset(self, path: Option<&'a FetchPart>) -> Result<SelectedMime<'a>> {
+        match path {
+            None => Ok(SelectedMime(self.0)),
+            Some(v) => self.rec_subset(v.0.as_ref()),
+        }
+    }
+
+    fn rec_subset(self, path: &'a [NonZeroU32]) -> Result<SelectedMime> {
+        if path.is_empty() {
+            Ok(SelectedMime(self.0))
+        } else {
+            match self.0 {
+                AnyPart::Mult(x) => {
+                    let next = Self(x.children
+                        .get(path[0].get() as usize - 1)
+                        .ok_or(anyhow!("Unable to resolve subpath {:?}, current multipart has only {} elements", path, x.children.len()))?);
+                    next.rec_subset(&path[1..])
+                },
+                AnyPart::Msg(x) => {
+                    let next = Self(x.child.as_ref());
+                    next.rec_subset(path)
+                },
+                _ => bail!("You tried to access a subpart on an atomic part (text or binary). Unresolved subpath {:?}", path),
+            }
+        }
+    }
+
+    fn structure(&self) -> Result<BodyStructure<'static>> {
+        match self.0 {
+            AnyPart::Txt(x) => NodeTxt(self, x).structure(),
+            AnyPart::Bin(x) => NodeBin(self, x).structure(),
+            AnyPart::Mult(x) => NodeMult(self, x).structure(),
+            AnyPart::Msg(x) => NodeMsg(self, x).structure(),
+        }
+    }
+}
+
+//----------------------------------------------------------
+
+/// A FetchSection must be handled in 2 times:
+///  - First we must extract the MIME part
+///  - Then we must process it as desired
+/// The given struct mixes both work, so
+/// we separate this work here.
+enum SubsettedSection<'a> {
+    Part,
+    Header,
+    HeaderFields(&'a NonEmptyVec<AString<'a>>),
+    HeaderFieldsNot(&'a NonEmptyVec<AString<'a>>),
+    Text,
+    Mime,
+}
+impl<'a> SubsettedSection<'a> {
+    fn from(section: &'a Option<FetchSection>) -> (Self, Option<&'a FetchPart>) {
+        match section {
+            Some(FetchSection::Text(maybe_part)) => (Self::Text, maybe_part.as_ref()),
+            Some(FetchSection::Header(maybe_part)) => (Self::Header, maybe_part.as_ref()),
+            Some(FetchSection::HeaderFields(maybe_part, fields)) => {
+                (Self::HeaderFields(fields), maybe_part.as_ref())
+            }
+            Some(FetchSection::HeaderFieldsNot(maybe_part, fields)) => {
+                (Self::HeaderFieldsNot(fields), maybe_part.as_ref())
+            }
+            Some(FetchSection::Mime(part)) => (Self::Mime, Some(part)),
+            Some(FetchSection::Part(part)) => (Self::Part, Some(part)),
+            None => (Self::Part, None),
+        }
+    }
+}
+
+/// Used for current MIME inspection
+///
+/// See NodeMime for recursive logic
+struct SelectedMime<'a>(&'a AnyPart<'a>);
+impl<'a> SelectedMime<'a> {
+    /// The subsetted fetch section basically tells us the
+    /// extraction logic to apply on our selected MIME.
+    /// This function acts as a router for these logic.
+    fn extract(&self, extractor: &SubsettedSection<'a>) -> Result<ExtractedFull<'a>> {
+        match extractor {
+            SubsettedSection::Text => self.text(),
+            SubsettedSection::Header => self.header(),
+            SubsettedSection::HeaderFields(fields) => self.header_fields(fields, false),
+            SubsettedSection::HeaderFieldsNot(fields) => self.header_fields(fields, true),
+            SubsettedSection::Part => self.part(),
+            SubsettedSection::Mime => self.mime(),
+        }
+    }
+
+    fn mime(&self) -> Result<ExtractedFull<'a>> {
+        let bytes = match &self.0 {
+            AnyPart::Txt(p) => p.mime.fields.raw,
+            AnyPart::Bin(p) => p.mime.fields.raw,
+            AnyPart::Msg(p) => p.child.mime().raw,
+            AnyPart::Mult(p) => p.mime.fields.raw,
+        };
+        Ok(ExtractedFull(bytes.into()))
+    }
+
+    fn part(&self) -> Result<ExtractedFull<'a>> {
+        let bytes = match &self.0 {
+            AnyPart::Txt(p) => p.body,
+            AnyPart::Bin(p) => p.body,
+            AnyPart::Msg(p) => p.raw_part,
+            AnyPart::Mult(_) => bail!("Multipart part has no body"),
+        };
+        Ok(ExtractedFull(bytes.to_vec().into()))
+    }
+
+    /// The [...] HEADER.FIELDS, and HEADER.FIELDS.NOT part
+    /// specifiers refer to the [RFC-2822] header of the message or of
+    /// an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
+    /// HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
+    /// field-name (as defined in [RFC-2822]) names, and return a
+    /// subset of the header.  The subset returned by HEADER.FIELDS
+    /// contains only those header fields with a field-name that
+    /// matches one of the names in the list; similarly, the subset
+    /// returned by HEADER.FIELDS.NOT contains only the header fields
+    /// with a non-matching field-name.  The field-matching is
+    /// case-insensitive but otherwise exact.
+    fn header_fields(
+        &self,
+        fields: &'a NonEmptyVec<AString<'a>>,
+        invert: bool,
+    ) -> Result<ExtractedFull<'a>> {
+        // Build a lowercase ascii hashset with the fields to fetch
+        let index = fields
+            .as_ref()
+            .iter()
+            .map(|x| {
+                match x {
+                    AString::Atom(a) => a.inner().as_bytes(),
+                    AString::String(IString::Literal(l)) => l.as_ref(),
+                    AString::String(IString::Quoted(q)) => q.inner().as_bytes(),
+                }
+                .to_ascii_lowercase()
+            })
+            .collect::<HashSet<_>>();
+
+        // Extract MIME headers
+        let mime = match &self.0 {
+            AnyPart::Msg(msg) => msg.child.mime(),
+            other => other.mime(),
+        };
+
+        // Filter our MIME headers based on the field index
+        // 1. Keep only the correctly formatted headers
+        // 2. Keep only based on the index presence or absence
+        // 3. Reduce as a byte vector
+        let buffer = mime
+            .kv
+            .iter()
+            .filter_map(|field| match field {
+                header::Field::Good(header::Kv2(k, v)) => Some((k, v)),
+                _ => None,
+            })
+            .filter(|(k, _)| index.contains(&k.to_ascii_lowercase()) ^ invert)
+            .fold(vec![], |mut acc, (k, v)| {
+                acc.extend(*k);
+                acc.extend(b": ");
+                acc.extend(*v);
+                acc.extend(b"\r\n");
+                acc
+            });
+
+        Ok(ExtractedFull(buffer.into()))
+    }
+
+    /// The HEADER [...] part specifiers refer to the [RFC-2822] header of the message or of
+    /// an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
+    /// ```raw
+    /// HEADER     ([RFC-2822] header of the message)
+    /// ```
+    fn header(&self) -> Result<ExtractedFull<'a>> {
+        let msg = self
+            .0
+            .as_message()
+            .ok_or(anyhow!("Selected part must be a message/rfc822"))?;
+        Ok(ExtractedFull(msg.raw_headers.into()))
+    }
+
+    /// The TEXT part specifier refers to the text body of the message, omitting the [RFC-2822] header.
+    fn text(&self) -> Result<ExtractedFull<'a>> {
+        let msg = self
+            .0
+            .as_message()
+            .ok_or(anyhow!("Selected part must be a message/rfc822"))?;
+        Ok(ExtractedFull(msg.raw_body.into()))
+    }
+
+    // ------------
+
+    /// Basic field of a MIME part that is
+    /// common to all parts
+    fn basic_fields(&self) -> Result<BasicFields<'static>> {
+        let sz = match self.0 {
+            AnyPart::Txt(x) => x.body.len(),
+            AnyPart::Bin(x) => x.body.len(),
+            AnyPart::Msg(x) => x.raw_part.len(),
+            AnyPart::Mult(_) => 0,
+        };
+        let m = self.0.mime();
+        let parameter_list = m
+            .ctype
+            .as_ref()
+            .map(|x| {
+                x.params
+                    .iter()
+                    .map(|p| {
+                        (
+                            IString::try_from(String::from_utf8_lossy(p.name).to_string()),
+                            IString::try_from(p.value.to_string()),
+                        )
+                    })
+                    .filter(|(k, v)| k.is_ok() && v.is_ok())
+                    .map(|(k, v)| (k.unwrap(), v.unwrap()))
+                    .collect()
+            })
+            .unwrap_or(vec![]);
+
+        Ok(BasicFields {
+            parameter_list,
+            id: NString(
+                m.id.as_ref()
+                    .and_then(|ci| IString::try_from(ci.to_string()).ok()),
+            ),
+            description: NString(
+                m.description
+                    .as_ref()
+                    .and_then(|cd| IString::try_from(cd.to_string()).ok()),
+            ),
+            content_transfer_encoding: match m.transfer_encoding {
+                mime::mechanism::Mechanism::_8Bit => unchecked_istring("8bit"),
+                mime::mechanism::Mechanism::Binary => unchecked_istring("binary"),
+                mime::mechanism::Mechanism::QuotedPrintable => {
+                    unchecked_istring("quoted-printable")
+                }
+                mime::mechanism::Mechanism::Base64 => unchecked_istring("base64"),
+                _ => unchecked_istring("7bit"),
+            },
+            // @FIXME we can't compute the size of the message currently...
+            size: u32::try_from(sz)?,
+        })
+    }
+}
+
+// ---------------------------
+struct NodeMsg<'a>(&'a NodeMime<'a>, &'a composite::Message<'a>);
+impl<'a> NodeMsg<'a> {
+    fn structure(&self) -> Result<BodyStructure<'static>> {
+        let basic = SelectedMime(self.0 .0).basic_fields()?;
+
+        Ok(BodyStructure::Single {
+            body: FetchBody {
+                basic,
+                specific: SpecificFields::Message {
+                    envelope: Box::new(message_envelope(&self.1.imf)),
+                    body_structure: Box::new(NodeMime(&self.1.child).structure()?),
+                    number_of_lines: nol(self.1.raw_part),
+                },
+            },
+            extension_data: None,
+        })
+    }
+}
+struct NodeMult<'a>(&'a NodeMime<'a>, &'a composite::Multipart<'a>);
+impl<'a> NodeMult<'a> {
+    fn structure(&self) -> Result<BodyStructure<'static>> {
+        let itype = &self.1.mime.interpreted_type;
+        let subtype = IString::try_from(itype.subtype.to_string())
+            .unwrap_or(unchecked_istring("alternative"));
+
+        let inner_bodies = self
+            .1
+            .children
+            .iter()
+            .filter_map(|inner| NodeMime(&inner).structure().ok())
+            .collect::<Vec<_>>();
+
+        NonEmptyVec::validate(&inner_bodies)?;
+        let bodies = NonEmptyVec::unvalidated(inner_bodies);
+
+        Ok(BodyStructure::Multi {
+            bodies,
+            subtype,
+            extension_data: None,
+            /*Some(MultipartExtensionData {
+            parameter_list: vec![],
+            disposition: None,
+            language: None,
+            location: None,
+            extension: vec![],
+            })*/
+        })
+    }
+}
+struct NodeTxt<'a>(&'a NodeMime<'a>, &'a discrete::Text<'a>);
+impl<'a> NodeTxt<'a> {
+    fn structure(&self) -> Result<BodyStructure<'static>> {
+        let mut basic = SelectedMime(self.0 .0).basic_fields()?;
+
+        // Get the interpreted content type, set it
+        let itype = match &self.1.mime.interpreted_type {
+            Deductible::Inferred(v) | Deductible::Explicit(v) => v,
+        };
+        let subtype =
+            IString::try_from(itype.subtype.to_string()).unwrap_or(unchecked_istring("plain"));
+
+        // Add charset to the list of parameters if we know it has been inferred as it will be
+        // missing from the parsed content.
+        if let Deductible::Inferred(charset) = &itype.charset {
+            basic.parameter_list.push((
+                unchecked_istring("charset"),
+                IString::try_from(charset.to_string()).unwrap_or(unchecked_istring("us-ascii")),
+            ));
+        }
+
+        Ok(BodyStructure::Single {
+            body: FetchBody {
+                basic,
+                specific: SpecificFields::Text {
+                    subtype,
+                    number_of_lines: nol(self.1.body),
+                },
+            },
+            extension_data: None,
+        })
+    }
+}
+
+struct NodeBin<'a>(&'a NodeMime<'a>, &'a discrete::Binary<'a>);
+impl<'a> NodeBin<'a> {
+    fn structure(&self) -> Result<BodyStructure<'static>> {
+        let basic = SelectedMime(self.0 .0).basic_fields()?;
+
+        let default = mime::r#type::NaiveType {
+            main: &b"application"[..],
+            sub: &b"octet-stream"[..],
+            params: vec![],
+        };
+        let ct = self.1.mime.fields.ctype.as_ref().unwrap_or(&default);
+
+        let r#type = IString::try_from(String::from_utf8_lossy(ct.main).to_string()).or(Err(
+            anyhow!("Unable to build IString from given Content-Type type given"),
+        ))?;
+
+        let subtype = IString::try_from(String::from_utf8_lossy(ct.sub).to_string()).or(Err(
+            anyhow!("Unable to build IString from given Content-Type subtype given"),
+        ))?;
+
+        Ok(BodyStructure::Single {
+            body: FetchBody {
+                basic,
+                specific: SpecificFields::Basic { r#type, subtype },
+            },
+            extension_data: None,
+        })
+    }
+}
+
+// ---------------------------
+
+struct ExtractedFull<'a>(Cow<'a, [u8]>);
+impl<'a> ExtractedFull<'a> {
+    /// It is possible to fetch a substring of the designated text.
+    /// This is done by appending an open angle bracket ("<"), the
+    /// octet position of the first desired octet, a period, the
+    /// maximum number of octets desired, and a close angle bracket
+    /// (">") to the part specifier.  If the starting octet is beyond
+    /// the end of the text, an empty string is returned.
+    ///
+    /// Any partial fetch that attempts to read beyond the end of the
+    /// text is truncated as appropriate.  A partial fetch that starts
+    /// at octet 0 is returned as a partial fetch, even if this
+    /// truncation happened.
+    ///
+    /// Note: This means that BODY[]<0.2048> of a 1500-octet message
+    /// will return BODY[]<0> with a literal of size 1500, not
+    /// BODY[].
+    ///
+    /// Note: A substring fetch of a HEADER.FIELDS or
+    /// HEADER.FIELDS.NOT part specifier is calculated after
+    /// subsetting the header.
+    fn to_body_section(self, partial: &'_ Option<(u32, NonZeroU32)>) -> BodySection<'a> {
+        match partial {
+            Some((begin, len)) => self.partialize(*begin, *len),
+            None => BodySection::Full(self.0),
+        }
+    }
+
+    fn partialize(self, begin: u32, len: NonZeroU32) -> BodySection<'a> {
+        // Asked range is starting after the end of the content,
+        // returning an empty buffer
+        if begin as usize > self.0.len() {
+            return BodySection::Slice {
+                body: Cow::Borrowed(&[][..]),
+                origin_octet: begin,
+            };
+        }
+
+        // Asked range is ending after the end of the content,
+        // slice only the beginning of the buffer
+        if (begin + len.get()) as usize >= self.0.len() {
+            return BodySection::Slice {
+                body: match self.0 {
+                    Cow::Borrowed(body) => Cow::Borrowed(&body[begin as usize..]),
+                    Cow::Owned(body) => Cow::Owned(body[begin as usize..].to_vec()),
+                },
+                origin_octet: begin,
+            };
+        }
+
+        // Range is included inside the considered content,
+        // this is the "happy case"
+        BodySection::Slice {
+            body: match self.0 {
+                Cow::Borrowed(body) => {
+                    Cow::Borrowed(&body[begin as usize..(begin + len.get()) as usize])
+                }
+                Cow::Owned(body) => {
+                    Cow::Owned(body[begin as usize..(begin + len.get()) as usize].to_vec())
+                }
+            },
+            origin_octet: begin,
+        }
+    }
+}
+
+/// ---- LEGACY
+
+/// s is set to static to ensure that only compile time values
+/// checked by developpers are passed.
+fn unchecked_istring(s: &'static str) -> IString {
+    IString::try_from(s).expect("this value is expected to be a valid imap-codec::IString")
+}
+
+// Number Of Lines
+fn nol(input: &[u8]) -> u32 {
+    input
+        .iter()
+        .filter(|x| **x == b'\n')
+        .count()
+        .try_into()
+        .unwrap_or(0)
+}
diff --git a/src/imap/mod.rs b/src/imap/mod.rs
index aac1fd3..4142ef9 100644
--- a/src/imap/mod.rs
+++ b/src/imap/mod.rs
@@ -1,8 +1,15 @@
+mod attributes;
 mod capability;
 mod command;
+mod flags;
 mod flow;
+mod imf_view;
+mod index;
+mod mail_view;
 mod mailbox_view;
+mod mime_view;
 mod response;
+mod search;
 mod session;
 
 use std::net::SocketAddr;
diff --git a/src/imap/search.rs b/src/imap/search.rs
new file mode 100644
index 0000000..b3c6b05
--- /dev/null
+++ b/src/imap/search.rs
@@ -0,0 +1,130 @@
+use imap_codec::imap_types::core::NonEmptyVec;
+use imap_codec::imap_types::search::SearchKey;
+use imap_codec::imap_types::sequence::{SeqOrUid, Sequence, SequenceSet};
+use std::num::NonZeroU32;
+
+pub enum SeqType {
+    Undefined,
+    NonUid,
+    Uid,
+}
+impl SeqType {
+    pub fn is_uid(&self) -> bool {
+        matches!(self, Self::Uid)
+    }
+}
+
+pub struct Criteria<'a>(pub &'a SearchKey<'a>);
+impl<'a> Criteria<'a> {
+    /// Returns a set of email identifiers that is greater or equal
+    /// to the set of emails to return
+    pub fn to_sequence_set(&self) -> (SequenceSet, SeqType) {
+        match self.0 {
+            SearchKey::All => (sequence_set_all(), SeqType::Undefined),
+            SearchKey::SequenceSet(seq_set) => (seq_set.clone(), SeqType::NonUid),
+            SearchKey::Uid(seq_set) => (seq_set.clone(), SeqType::Uid),
+            SearchKey::Not(_inner) => {
+                tracing::debug!(
+                    "using NOT in a search request is slow: it selects all identifiers"
+                );
+                (sequence_set_all(), SeqType::Undefined)
+            }
+            SearchKey::Or(left, right) => {
+                tracing::debug!("using OR in a search request is slow: no deduplication is done");
+                let (base, base_seqtype) = Self(&left).to_sequence_set();
+                let (ext, ext_seqtype) = Self(&right).to_sequence_set();
+
+                // Check if we have a UID/ID conflict in fetching: now we don't know how to handle them
+                match (base_seqtype, ext_seqtype) {
+                    (SeqType::Uid, SeqType::NonUid) | (SeqType::NonUid, SeqType::Uid) => {
+                        (sequence_set_all(), SeqType::Undefined)
+                    }
+                    (SeqType::Undefined, x) | (x, _) => {
+                        let mut new_vec = base.0.into_inner();
+                        new_vec.extend_from_slice(ext.0.as_ref());
+                        let seq = SequenceSet(
+                            NonEmptyVec::try_from(new_vec)
+                                .expect("merging non empty vec lead to non empty vec"),
+                        );
+                        (seq, x)
+                    }
+                }
+            }
+            SearchKey::And(search_list) => {
+                tracing::debug!(
+                    "using AND in a search request is slow: no intersection is performed"
+                );
+                search_list
+                    .as_ref()
+                    .iter()
+                    .map(|crit| Self(&crit).to_sequence_set())
+                    .min_by(|(x, _), (y, _)| {
+                        let x_size = approx_sequence_set_size(x);
+                        let y_size = approx_sequence_set_size(y);
+                        x_size.cmp(&y_size)
+                    })
+                    .unwrap_or((sequence_set_all(), SeqType::Undefined))
+            }
+            _ => (sequence_set_all(), SeqType::Undefined),
+        }
+    }
+
+    /// Not really clever as we can have cases where we filter out
+    /// the email before needing to inspect its meta.
+    /// But for now we are seeking the most basic/stupid algorithm.
+    pub fn need_meta(&self) -> bool {
+        use SearchKey::*;
+        match self.0 {
+            // IMF Headers
+            Bcc(_) | Cc(_) | From(_) | Header(..) | SentBefore(_) | SentOn(_) | SentSince(_)
+            | Subject(_) | To(_) => true,
+            // Internal Date is also stored in MailMeta
+            Before(_) | On(_) | Since(_) => true,
+            // Message size is also stored in MailMeta
+            Larger(_) | Smaller(_) => true,
+            And(and_list) => and_list.as_ref().iter().any(|sk| Criteria(sk).need_meta()),
+            Not(inner) => Criteria(inner).need_meta(),
+            Or(left, right) => Criteria(left).need_meta() || Criteria(right).need_meta(),
+            _ => false,
+        }
+    }
+
+    pub fn need_body(&self) -> bool {
+        use SearchKey::*;
+        match self.0 {
+            Text(_) | Body(_) => true,
+            And(and_list) => and_list.as_ref().iter().any(|sk| Criteria(sk).need_body()),
+            Not(inner) => Criteria(inner).need_body(),
+            Or(left, right) => Criteria(left).need_body() || Criteria(right).need_body(),
+            _ => false,
+        }
+    }
+}
+
+fn sequence_set_all() -> SequenceSet {
+    SequenceSet::from(Sequence::Range(
+        SeqOrUid::Value(NonZeroU32::MIN),
+        SeqOrUid::Asterisk,
+    ))
+}
+
+// This is wrong as sequences can overlap
+fn approx_sequence_set_size(seq_set: &SequenceSet) -> u64 {
+    seq_set.0.as_ref().iter().fold(0u64, |acc, seq| {
+        acc.saturating_add(approx_sequence_size(seq))
+    })
+}
+
+// This is wrong as sequence UID can have holes,
+// as we don't know the number of messages in the mailbox also
+fn approx_sequence_size(seq: &Sequence) -> u64 {
+    match seq {
+        Sequence::Single(_) => 1,
+        Sequence::Range(SeqOrUid::Asterisk, _) | Sequence::Range(_, SeqOrUid::Asterisk) => u64::MAX,
+        Sequence::Range(SeqOrUid::Value(x1), SeqOrUid::Value(x2)) => {
+            let x2 = x2.get() as i64;
+            let x1 = x1.get() as i64;
+            (x2 - x1).abs().try_into().unwrap_or(1)
+        }
+    }
+}