Merge pull request 'CONDSTORE' (#71) from feat/condstore-try-2 into main

Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/aerogramme/pulls/71

10 files changed, 417 insertions, 133 deletions

diff --git a/src/imap/attributes.rs b/src/imap/attributes.rs
index cf7cb52..d094f1a 100644
--- a/src/imap/attributes.rs
+++ b/src/imap/attributes.rs
@@ -1,4 +1,5 @@
 use imap_codec::imap_types::fetch::{MacroOrMessageDataItemNames, MessageDataItemName, Section};
+use imap_codec::imap_types::command::FetchModifier;
 
 /// Internal decisions based on fetched attributes
 /// passed by the client
@@ -7,7 +8,7 @@ pub struct AttributesProxy {
     pub attrs: Vec<MessageDataItemName<'static>>,
 }
 impl AttributesProxy {
-    pub fn new(attrs: &MacroOrMessageDataItemNames<'static>, is_uid_fetch: bool) -> Self {
+    pub fn new(attrs: &MacroOrMessageDataItemNames<'static>, modifiers: &[FetchModifier], is_uid_fetch: bool) -> Self {
         // Expand macros
         let mut fetch_attrs = match attrs {
             MacroOrMessageDataItemNames::Macro(m) => {
@@ -31,9 +32,23 @@ impl AttributesProxy {
             fetch_attrs.push(MessageDataItemName::Uid);
         }
 
+        // Handle inferred MODSEQ tag
+        let is_changed_since = modifiers
+            .iter()
+            .any(|m| matches!(m, FetchModifier::ChangedSince(..)));
+        if is_changed_since && !fetch_attrs.contains(&MessageDataItemName::ModSeq) {
+            fetch_attrs.push(MessageDataItemName::ModSeq);
+        }
+
         Self { attrs: fetch_attrs }
     }
 
+    pub fn is_enabling_condstore(&self) -> bool {
+        self.attrs.iter().any(|x| {
+            matches!(x, MessageDataItemName::ModSeq)
+        })
+    }
+
     pub fn need_body(&self) -> bool {
         self.attrs.iter().any(|x| {
             match x {
diff --git a/src/imap/capability.rs b/src/imap/capability.rs
index feadb6b..6533ccb 100644
--- a/src/imap/capability.rs
+++ b/src/imap/capability.rs
@@ -1,8 +1,11 @@
+use imap_codec::imap_types::command::{FetchModifier, StoreModifier, SelectExamineModifier};
 use imap_codec::imap_types::core::NonEmptyVec;
 use imap_codec::imap_types::extensions::enable::{CapabilityEnable, Utf8Kind};
 use imap_codec::imap_types::response::Capability;
 use std::collections::HashSet;
 
+use crate::imap::attributes::AttributesProxy;
+
 fn capability_unselect() -> Capability<'static> {
     Capability::try_from("UNSELECT").unwrap()
 }
@@ -11,9 +14,11 @@ fn capability_condstore() -> Capability<'static> {
     Capability::try_from("CONDSTORE").unwrap()
 }
 
+/*
 fn capability_qresync() -> Capability<'static> {
     Capability::try_from("QRESYNC").unwrap()
 }
+*/
 
 #[derive(Debug, Clone)]
 pub struct ServerCapability(HashSet<Capability<'static>>);
@@ -26,7 +31,7 @@ impl Default for ServerCapability {
             Capability::Move,
             Capability::LiteralPlus,
             capability_unselect(),
-            //capability_condstore(),
+            capability_condstore(),
             //capability_qresync(),
         ]))
     }
@@ -48,15 +53,29 @@ impl ServerCapability {
     }
 }
 
-enum ClientStatus {
+#[derive(Clone)]
+pub enum ClientStatus {
     NotSupportedByServer,
     Disabled,
     Enabled,
 }
+impl ClientStatus {
+    pub fn is_enabled(&self) -> bool {
+        matches!(self, Self::Enabled)
+    }
+
+    pub fn enable(&self) -> Self {
+        match self {
+            Self::Disabled => Self::Enabled,
+            other => other.clone(),
+        }
+    }
+}
+
 
 pub struct ClientCapability {
-    condstore: ClientStatus,
-    utf8kind: Option<Utf8Kind>,
+    pub condstore: ClientStatus,
+    pub utf8kind: Option<Utf8Kind>,
 }
 
 impl ClientCapability {
@@ -70,6 +89,36 @@ impl ClientCapability {
         }
     }
 
+    pub fn enable_condstore(&mut self) {
+        self.condstore = self.condstore.enable();
+    }
+
+    pub fn attributes_enable(&mut self, ap: &AttributesProxy) {
+        if ap.is_enabling_condstore() {
+            self.enable_condstore()
+        }
+    }
+
+    pub fn fetch_modifiers_enable(&mut self, mods: &[FetchModifier]) {
+        if mods.iter().any(|x| matches!(x, FetchModifier::ChangedSince(..))) {
+            self.enable_condstore()
+        }
+    }
+
+    pub fn store_modifiers_enable(&mut self, mods: &[StoreModifier]) {
+        if mods.iter().any(|x| matches!(x, StoreModifier::UnchangedSince(..))) {
+            self.enable_condstore()
+        }
+    }
+
+    pub fn select_enable(&mut self, mods: &[SelectExamineModifier]) {
+        for m in mods.iter() {
+            match m {
+                SelectExamineModifier::Condstore => self.enable_condstore(),
+            }
+        }
+    }
+
     pub fn try_enable(
         &mut self,
         caps: &[CapabilityEnable<'static>],
diff --git a/src/imap/command/authenticated.rs b/src/imap/command/authenticated.rs
index 1481a80..9b6bb24 100644
--- a/src/imap/command/authenticated.rs
+++ b/src/imap/command/authenticated.rs
@@ -2,7 +2,7 @@ use std::collections::BTreeMap;
 use std::sync::Arc;
 
 use anyhow::{anyhow, bail, Result};
-use imap_codec::imap_types::command::{Command, CommandBody};
+use imap_codec::imap_types::command::{Command, CommandBody, SelectExamineModifier};
 use imap_codec::imap_types::core::{Atom, Literal, NonEmptyVec, QuotedChar};
 use imap_codec::imap_types::datetime::DateTime;
 use imap_codec::imap_types::extensions::enable::CapabilityEnable;
@@ -58,8 +58,8 @@ pub async fn dispatch<'a>(
         } => ctx.status(mailbox, item_names).await,
         CommandBody::Subscribe { mailbox } => ctx.subscribe(mailbox).await,
         CommandBody::Unsubscribe { mailbox } => ctx.unsubscribe(mailbox).await,
-        CommandBody::Select { mailbox } => ctx.select(mailbox).await,
-        CommandBody::Examine { mailbox } => ctx.examine(mailbox).await,
+        CommandBody::Select { mailbox, modifiers } => ctx.select(mailbox, modifiers).await,
+        CommandBody::Examine { mailbox, modifiers } => ctx.examine(mailbox, modifiers).await,
         CommandBody::Append {
             mailbox,
             flags,
@@ -292,7 +292,7 @@ impl<'a> AuthenticatedContext<'a> {
             }
         };
 
-        let view = MailboxView::new(mb).await;
+        let view = MailboxView::new(mb, self.client_capabilities.condstore.is_enabled()).await;
 
         let mut ret_attrs = vec![];
         for attr in attributes.iter() {
@@ -311,8 +311,9 @@ impl<'a> AuthenticatedContext<'a> {
                     bail!("quota not implemented, can't return freed storage after EXPUNGE will be run");
                 },
                 StatusDataItemName::HighestModSeq => {
-                    bail!("highestmodseq not yet implemented");
-                }
+                    self.client_capabilities.enable_condstore();
+                    StatusDataItem::HighestModSeq(view.highestmodseq().get())
+                },
             });
         }
 
@@ -404,6 +405,7 @@ impl<'a> AuthenticatedContext<'a> {
                           it is therefore correct to not return it even if there are unseen messages
       RFC9051 (imap4rev2) says that OK [UNSEEN] responses are deprecated after SELECT and EXAMINE
       For Aerogramme, we just don't send the OK [UNSEEN], it's correct to do in both specifications.
+    
 
     20 select "INBOX.achats"
     * FLAGS (\Answered \Flagged \Deleted \Seen \Draft $Forwarded JUNK $label1)
@@ -420,7 +422,10 @@ impl<'a> AuthenticatedContext<'a> {
     async fn select(
         self,
         mailbox: &MailboxCodec<'a>,
+        modifiers: &[SelectExamineModifier],
     ) -> Result<(Response<'static>, flow::Transition)> {
+        self.client_capabilities.select_enable(modifiers);
+
         let name: &str = MailboxName(mailbox).try_into()?;
 
         let mb_opt = self.user.open_mailbox(&name).await?;
@@ -438,7 +443,7 @@ impl<'a> AuthenticatedContext<'a> {
         };
         tracing::info!(username=%self.user.username, mailbox=%name, "mailbox.selected");
 
-        let mb = MailboxView::new(mb).await;
+        let mb = MailboxView::new(mb, self.client_capabilities.condstore.is_enabled()).await;
         let data = mb.summary()?;
 
         Ok((
@@ -455,7 +460,10 @@ impl<'a> AuthenticatedContext<'a> {
     async fn examine(
         self,
         mailbox: &MailboxCodec<'a>,
+        modifiers: &[SelectExamineModifier],
     ) -> Result<(Response<'static>, flow::Transition)> {
+        self.client_capabilities.select_enable(modifiers);
+
         let name: &str = MailboxName(mailbox).try_into()?;
 
         let mb_opt = self.user.open_mailbox(&name).await?;
@@ -473,7 +481,7 @@ impl<'a> AuthenticatedContext<'a> {
         };
         tracing::info!(username=%self.user.username, mailbox=%name, "mailbox.examined");
 
-        let mb = MailboxView::new(mb).await;
+        let mb = MailboxView::new(mb, self.client_capabilities.condstore.is_enabled()).await;
         let data = mb.summary()?;
 
         Ok((
@@ -496,7 +504,7 @@ impl<'a> AuthenticatedContext<'a> {
     ) -> Result<(Response<'static>, flow::Transition)> {
         let append_tag = self.req.tag.clone();
         match self.append_internal(mailbox, flags, date, message).await {
-            Ok((_mb, uidvalidity, uid)) => Ok((
+            Ok((_mb, uidvalidity, uid, _modseq)) => Ok((
                 Response::build()
                     .tag(append_tag)
                     .message("APPEND completed")
@@ -537,7 +545,7 @@ impl<'a> AuthenticatedContext<'a> {
         flags: &[Flag<'a>],
         date: &Option<DateTime>,
         message: &Literal<'a>,
-    ) -> Result<(Arc<Mailbox>, ImapUidvalidity, ImapUidvalidity)> {
+    ) -> Result<(Arc<Mailbox>, ImapUidvalidity, ImapUid, ModSeq)> {
         let name: &str = MailboxName(mailbox).try_into()?;
 
         let mb_opt = self.user.open_mailbox(&name).await?;
@@ -555,9 +563,9 @@ impl<'a> AuthenticatedContext<'a> {
         let flags = flags.iter().map(|x| x.to_string()).collect::<Vec<_>>();
         // TODO: filter allowed flags? ping @Quentin
 
-        let (uidvalidity, uid) = mb.append(msg, None, &flags[..]).await?;
+        let (uidvalidity, uid, modseq) = mb.append(msg, None, &flags[..]).await?;
 
-        Ok((mb, uidvalidity, uid))
+        Ok((mb, uidvalidity, uid, modseq))
     }
 }
 
diff --git a/src/imap/command/examined.rs b/src/imap/command/examined.rs
index 3dd11e2..9fc0990 100644
--- a/src/imap/command/examined.rs
+++ b/src/imap/command/examined.rs
@@ -1,16 +1,18 @@
 use std::sync::Arc;
+use std::num::NonZeroU64;
 
 use anyhow::Result;
-use imap_codec::imap_types::command::{Command, CommandBody};
+use imap_codec::imap_types::command::{Command, CommandBody, FetchModifier};
 use imap_codec::imap_types::core::Charset;
 use imap_codec::imap_types::fetch::MacroOrMessageDataItemNames;
 use imap_codec::imap_types::search::SearchKey;
 use imap_codec::imap_types::sequence::SequenceSet;
 
+use crate::imap::attributes::AttributesProxy;
 use crate::imap::capability::{ClientCapability, ServerCapability};
 use crate::imap::command::{anystate, authenticated};
 use crate::imap::flow;
-use crate::imap::mailbox_view::MailboxView;
+use crate::imap::mailbox_view::{MailboxView, UpdateParameters};
 use crate::imap::response::Response;
 use crate::mail::user::User;
 
@@ -37,8 +39,9 @@ pub async fn dispatch(ctx: ExaminedContext<'_>) -> Result<(Response<'static>, fl
         CommandBody::Fetch {
             sequence_set,
             macro_or_item_names,
+            modifiers,
             uid,
-        } => ctx.fetch(sequence_set, macro_or_item_names, uid).await,
+        } => ctx.fetch(sequence_set, macro_or_item_names, modifiers, uid).await,
         CommandBody::Search {
             charset,
             criteria,
@@ -88,17 +91,33 @@ impl<'a> ExaminedContext<'a> {
         self,
         sequence_set: &SequenceSet,
         attributes: &'a MacroOrMessageDataItemNames<'static>,
+        modifiers: &[FetchModifier],
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        match self.mailbox.fetch(sequence_set, attributes, uid).await {
-            Ok(resp) => Ok((
-                Response::build()
-                    .to_req(self.req)
-                    .message("FETCH completed")
-                    .set_body(resp)
-                    .ok()?,
-                flow::Transition::None,
-            )),
+        let ap = AttributesProxy::new(attributes, modifiers, *uid);
+        let mut changed_since: Option<NonZeroU64> = None;
+        modifiers.iter().for_each(|m| match m {
+            FetchModifier::ChangedSince(val) => {
+                changed_since = Some(*val);
+            },
+        });
+
+        match self.mailbox.fetch(sequence_set, &ap, changed_since, uid).await {
+            Ok(resp) => {
+                // Capabilities enabling logic only on successful command
+                // (according to my understanding of the spec)
+                self.client_capabilities.attributes_enable(&ap);
+                self.client_capabilities.fetch_modifiers_enable(modifiers);
+
+                Ok((
+                    Response::build()
+                        .to_req(self.req)
+                        .message("FETCH completed")
+                        .set_body(resp)
+                        .ok()?,
+                    flow::Transition::None,
+                ))
+            },
             Err(e) => Ok((
                 Response::build()
                     .to_req(self.req)
@@ -115,7 +134,10 @@ impl<'a> ExaminedContext<'a> {
         criteria: &SearchKey<'a>,
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        let found = self.mailbox.search(charset, criteria, *uid).await?;
+        let (found, enable_condstore) = self.mailbox.search(charset, criteria, *uid).await?;
+        if enable_condstore {
+            self.client_capabilities.enable_condstore();
+        }
         Ok((
             Response::build()
                 .to_req(self.req)
@@ -127,9 +149,9 @@ impl<'a> ExaminedContext<'a> {
     }
 
     pub async fn noop(self) -> Result<(Response<'static>, flow::Transition)> {
-        self.mailbox.0.mailbox.force_sync().await?;
+        self.mailbox.internal.mailbox.force_sync().await?;
 
-        let updates = self.mailbox.update().await?;
+        let updates = self.mailbox.update(UpdateParameters::default()).await?;
         Ok((
             Response::build()
                 .to_req(self.req)
diff --git a/src/imap/command/selected.rs b/src/imap/command/selected.rs
index 35c3eb4..c13b71a 100644
--- a/src/imap/command/selected.rs
+++ b/src/imap/command/selected.rs
@@ -1,7 +1,8 @@
 use std::sync::Arc;
+use std::num::NonZeroU64;
 
 use anyhow::Result;
-use imap_codec::imap_types::command::{Command, CommandBody};
+use imap_codec::imap_types::command::{Command, CommandBody, FetchModifier, StoreModifier};
 use imap_codec::imap_types::core::Charset;
 use imap_codec::imap_types::fetch::MacroOrMessageDataItemNames;
 use imap_codec::imap_types::flag::{Flag, StoreResponse, StoreType};
@@ -13,9 +14,9 @@ use imap_codec::imap_types::sequence::SequenceSet;
 use crate::imap::capability::{ClientCapability, ServerCapability};
 use crate::imap::command::{anystate, authenticated, MailboxName};
 use crate::imap::flow;
-use crate::imap::mailbox_view::MailboxView;
+use crate::imap::mailbox_view::{MailboxView, UpdateParameters};
 use crate::imap::response::Response;
-
+use crate::imap::attributes::AttributesProxy;
 use crate::mail::user::User;
 
 pub struct SelectedContext<'a> {
@@ -43,8 +44,9 @@ pub async fn dispatch<'a>(
         CommandBody::Fetch {
             sequence_set,
             macro_or_item_names,
+            modifiers,
             uid,
-        } => ctx.fetch(sequence_set, macro_or_item_names, uid).await,
+        } => ctx.fetch(sequence_set, macro_or_item_names, modifiers, uid).await,
         CommandBody::Search {
             charset,
             criteria,
@@ -56,8 +58,9 @@ pub async fn dispatch<'a>(
             kind,
             response,
             flags,
+            modifiers,
             uid,
-        } => ctx.store(sequence_set, kind, response, flags, uid).await,
+        } => ctx.store(sequence_set, kind, response, flags, modifiers, uid).await,
         CommandBody::Copy {
             sequence_set,
             mailbox,
@@ -113,17 +116,34 @@ impl<'a> SelectedContext<'a> {
         self,
         sequence_set: &SequenceSet,
         attributes: &'a MacroOrMessageDataItemNames<'static>,
+        modifiers: &[FetchModifier],
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        match self.mailbox.fetch(sequence_set, attributes, uid).await {
-            Ok(resp) => Ok((
-                Response::build()
-                    .to_req(self.req)
-                    .message("FETCH completed")
-                    .set_body(resp)
-                    .ok()?,
-                flow::Transition::None,
-            )),
+        let ap = AttributesProxy::new(attributes, modifiers, *uid);
+        let mut changed_since: Option<NonZeroU64> = None;
+        modifiers.iter().for_each(|m| match m {
+            FetchModifier::ChangedSince(val) => {
+                changed_since = Some(*val);
+            },
+        });
+
+        match self.mailbox.fetch(sequence_set, &ap, changed_since, uid).await {
+            Ok(resp) => {
+                // Capabilities enabling logic only on successful command
+                // (according to my understanding of the spec)
+                self.client_capabilities.attributes_enable(&ap);
+                self.client_capabilities.fetch_modifiers_enable(modifiers);
+
+                // Response to the client
+                Ok((
+                    Response::build()
+                        .to_req(self.req)
+                        .message("FETCH completed")
+                        .set_body(resp)
+                        .ok()?,
+                    flow::Transition::None,
+                ))
+            },
             Err(e) => Ok((
                 Response::build()
                     .to_req(self.req)
@@ -140,7 +160,10 @@ impl<'a> SelectedContext<'a> {
         criteria: &SearchKey<'a>,
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        let found = self.mailbox.search(charset, criteria, *uid).await?;
+        let (found, enable_condstore) = self.mailbox.search(charset, criteria, *uid).await?;
+        if enable_condstore {
+            self.client_capabilities.enable_condstore();
+        }
         Ok((
             Response::build()
                 .to_req(self.req)
@@ -152,9 +175,9 @@ impl<'a> SelectedContext<'a> {
     }
 
     pub async fn noop(self) -> Result<(Response<'static>, flow::Transition)> {
-        self.mailbox.0.mailbox.force_sync().await?;
+        self.mailbox.internal.mailbox.force_sync().await?;
 
-        let updates = self.mailbox.update().await?;
+        let updates = self.mailbox.update(UpdateParameters::default()).await?;
         Ok((
             Response::build()
                 .to_req(self.req)
@@ -185,19 +208,39 @@ impl<'a> SelectedContext<'a> {
         kind: &StoreType,
         response: &StoreResponse,
         flags: &[Flag<'a>],
+        modifiers: &[StoreModifier],
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        let data = self
+        let mut unchanged_since: Option<NonZeroU64> = None;
+        modifiers.iter().for_each(|m| match m {
+            StoreModifier::UnchangedSince(val) => {
+                unchanged_since = Some(*val);
+            },
+        });
+
+        let (data, modified) = self
             .mailbox
-            .store(sequence_set, kind, response, flags, uid)
+            .store(sequence_set, kind, response, flags, unchanged_since, uid)
             .await?;
 
-        Ok((
-            Response::build()
+        let mut ok_resp = Response::build()
                 .to_req(self.req)
                 .message("STORE completed")
-                .set_body(data)
-                .ok()?,
+                .set_body(data);
+
+
+        match modified[..] {
+            [] => (),
+            [_head, ..] => {
+                let modified_str = format!("MODIFIED {}", modified.into_iter().map(|x| x.to_string()).collect::<Vec<_>>().join(","));
+                ok_resp = ok_resp.code(Code::Other(CodeOther::unvalidated(modified_str.into_bytes())));
+            },
+        };
+
+
+        self.client_capabilities.store_modifiers_enable(modifiers);
+
+        Ok((ok_resp.ok()?,
             flow::Transition::None,
         ))
     }
diff --git a/src/imap/index.rs b/src/imap/index.rs
index 4853374..9b794b8 100644
--- a/src/imap/index.rs
+++ b/src/imap/index.rs
@@ -1,9 +1,9 @@
-use std::num::NonZeroU32;
+use std::num::{NonZeroU32, NonZeroU64};
 
 use anyhow::{anyhow, Result};
-use imap_codec::imap_types::sequence::{self, SeqOrUid, Sequence, SequenceSet};
+use imap_codec::imap_types::sequence::{SeqOrUid, Sequence, SequenceSet};
 
-use crate::mail::uidindex::{ImapUid, UidIndex};
+use crate::mail::uidindex::{ImapUid, ModSeq, UidIndex};
 use crate::mail::unique_ident::UniqueIdent;
 
 pub struct Index<'a> {
@@ -17,12 +17,10 @@ impl<'a> Index<'a> {
             .iter()
             .enumerate()
             .map(|(i_enum, (&uid, &uuid))| {
-                let flags = internal
+                let (_, modseq, flags) = internal
                     .table
                     .get(&uuid)
-                    .ok_or(anyhow!("mail is missing from index"))?
-                    .1
-                    .as_ref();
+                    .ok_or(anyhow!("mail is missing from index"))?;
                 let i_int: u32 = (i_enum + 1).try_into()?;
                 let i: NonZeroU32 = i_int.try_into()?;
 
@@ -30,6 +28,7 @@ impl<'a> Index<'a> {
                     i,
                     uid,
                     uuid,
+                    modseq: *modseq,
                     flags,
                 })
             })
@@ -61,10 +60,8 @@ impl<'a> Index<'a> {
         if self.imap_index.is_empty() {
             return vec![];
         }
-        let iter_strat = sequence::Strategy::Naive {
-            largest: self.last().expect("The mailbox is not empty").uid,
-        };
-        let mut unroll_seq = sequence_set.iter(iter_strat).collect::<Vec<_>>();
+        let largest = self.last().expect("The mailbox is not empty").uid;
+        let mut unroll_seq = sequence_set.iter(largest).collect::<Vec<_>>();
         unroll_seq.sort();
 
         let start_seq = match unroll_seq.iter().next() {
@@ -103,11 +100,9 @@ impl<'a> Index<'a> {
         if self.imap_index.is_empty() {
             return Ok(vec![]);
         }
-        let iter_strat = sequence::Strategy::Naive {
-            largest: NonZeroU32::try_from(self.imap_index.len() as u32)?,
-        };
+        let largest = NonZeroU32::try_from(self.imap_index.len() as u32)?;
         let mut acc = sequence_set
-            .iter(iter_strat)
+            .iter(largest)
             .map(|wanted_id| {
                 self.imap_index
                     .get((wanted_id.get() as usize) - 1)
@@ -131,6 +126,36 @@ impl<'a> Index<'a> {
             _ => self.fetch_on_id(sequence_set),
         }
     }
+
+    pub fn fetch_changed_since(
+        self: &'a Index<'a>,
+        sequence_set: &SequenceSet,
+        maybe_modseq: Option<NonZeroU64>,
+        by_uid: bool,
+    ) -> Result<Vec<&'a MailIndex<'a>>> {
+        let raw = self.fetch(sequence_set, by_uid)?;
+        let res = match maybe_modseq {
+            Some(pit) => raw.into_iter().filter(|midx| midx.modseq > pit).collect(),
+            None => raw,
+        };
+
+        Ok(res)
+    }
+
+    pub fn fetch_unchanged_since(
+        self: &'a Index<'a>,
+        sequence_set: &SequenceSet,
+        maybe_modseq: Option<NonZeroU64>,
+        by_uid: bool,
+    ) -> Result<(Vec<&'a MailIndex<'a>>, Vec<&'a MailIndex<'a>>)> {
+        let raw = self.fetch(sequence_set, by_uid)?;
+        let res = match maybe_modseq {
+            Some(pit) => raw.into_iter().partition(|midx| midx.modseq <= pit),
+            None => (raw, vec![]),
+        };
+
+        Ok(res)
+    }
 }
 
 #[derive(Clone, Debug)]
@@ -138,6 +163,7 @@ pub struct MailIndex<'a> {
     pub i: NonZeroU32,
     pub uid: ImapUid,
     pub uuid: UniqueIdent,
+    pub modseq: ModSeq,
     pub flags: &'a Vec<String>,
 }
 
diff --git a/src/imap/mail_view.rs b/src/imap/mail_view.rs
index eeb6b4b..a8db733 100644
--- a/src/imap/mail_view.rs
+++ b/src/imap/mail_view.rs
@@ -90,6 +90,7 @@ impl<'a> MailView<'a> {
                     Ok(body)
                 }
                 MessageDataItemName::InternalDate => self.internal_date(),
+                MessageDataItemName::ModSeq => Ok(self.modseq()),
             })
             .collect::<Result<Vec<_>, _>>()?;
 
@@ -252,6 +253,10 @@ impl<'a> MailView<'a> {
             .ok_or(anyhow!("Unable to parse internal date"))?;
         Ok(MessageDataItem::InternalDate(DateTime::unvalidated(dt)))
     }
+
+    fn modseq(&self) -> MessageDataItem<'static> {
+        MessageDataItem::ModSeq(self.in_idx.modseq)
+    }
 }
 
 pub enum SeenFlag {
diff --git a/src/imap/mailbox_view.rs b/src/imap/mailbox_view.rs
index 513567f..07fa3ad 100644
--- a/src/imap/mailbox_view.rs
+++ b/src/imap/mailbox_view.rs
@@ -1,21 +1,23 @@
-use std::num::NonZeroU32;
+use std::num::{NonZeroU32, NonZeroU64};
 use std::sync::Arc;
+use std::collections::HashSet;
 
 use anyhow::{anyhow, Error, Result};
 
 use futures::stream::{FuturesOrdered, StreamExt};
 
 use imap_codec::imap_types::core::Charset;
-use imap_codec::imap_types::fetch::{MacroOrMessageDataItemNames, MessageDataItem};
+use imap_codec::imap_types::fetch::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::response::{Code, CodeOther, Data, Status};
 use imap_codec::imap_types::search::SearchKey;
 use imap_codec::imap_types::sequence::SequenceSet;
 
+use crate::mail::unique_ident::UniqueIdent;
 use crate::mail::mailbox::Mailbox;
 use crate::mail::query::QueryScope;
 use crate::mail::snapshot::FrozenMailbox;
-use crate::mail::uidindex::{ImapUid, ImapUidvalidity};
+use crate::mail::uidindex::{ImapUid, ImapUidvalidity, ModSeq};
 
 use crate::imap::attributes::AttributesProxy;
 use crate::imap::flags;
@@ -32,6 +34,21 @@ const DEFAULT_FLAGS: [Flag; 5] = [
     Flag::Draft,
 ];
 
+pub struct UpdateParameters {
+    pub silence: HashSet<UniqueIdent>,
+    pub with_modseq: bool,
+    pub with_uid: bool,
+}
+impl Default for UpdateParameters {
+    fn default() -> Self {
+        Self {
+            silence: HashSet::new(),
+            with_modseq: false,
+            with_uid: false,
+        }
+    }
+}
+
 /// 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
@@ -39,12 +56,18 @@ const DEFAULT_FLAGS: [Flag; 5] = [
 /// 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 FrozenMailbox);
+pub struct MailboxView {
+    pub internal: FrozenMailbox,
+    pub is_condstore: bool,
+}
 
 impl MailboxView {
     /// Creates a new IMAP view into a mailbox.
-    pub async fn new(mailbox: Arc<Mailbox>) -> Self {
-        Self(mailbox.frozen().await)
+    pub async fn new(mailbox: Arc<Mailbox>, is_cond: bool) -> Self {
+        Self { 
+            internal: mailbox.frozen().await,
+            is_condstore: is_cond,
+        }
     }
 
     /// Create an updated view, useful to make a diff
@@ -53,9 +76,9 @@ impl MailboxView {
     /// what the client knows and what is actually in the mailbox.
     /// 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_snapshot = self.0.update().await;
-        let new_snapshot = &self.0.snapshot;
+    pub async fn update(&mut self, params: UpdateParameters) -> Result<Vec<Body<'static>>> {
+        let old_snapshot = self.internal.update().await;
+        let new_snapshot = &self.internal.snapshot;
 
         let mut data = Vec::<Body>::new();
 
@@ -99,19 +122,31 @@ impl MailboxView {
         } else {
             // - if flags changed for existing mails, tell client
             for (i, (_uid, uuid)) in new_snapshot.idx_by_uid.iter().enumerate() {
+                if params.silence.contains(uuid) {
+                    continue;
+                }
+
                 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 {
+                    if let Some((uid, modseq, flags)) = new_mail {
+                        let mut items = vec![
+                            MessageDataItem::Flags(
+                                flags.iter().filter_map(|f| flags::from_str(f)).collect(),
+                            ),
+                        ];
+
+                        if params.with_uid {
+                            items.push(MessageDataItem::Uid(*uid));
+                        }
+
+                        if params.with_modseq {
+                            items.push(MessageDataItem::ModSeq(*modseq));
+                        }
+
                         data.push(Body::Data(Data::Fetch {
                             seq: NonZeroU32::try_from((i + 1) as u32).unwrap(),
-                            items: vec![
-                                MessageDataItem::Uid(*uid),
-                                MessageDataItem::Flags(
-                                    flags.iter().filter_map(|f| flags::from_str(f)).collect(),
-                                ),
-                            ]
-                            .try_into()?,
+                            items: items.try_into()?,
                         }));
                     }
                 }
@@ -130,8 +165,11 @@ impl MailboxView {
         data.extend(self.flags_status()?.into_iter());
         data.push(self.uidvalidity_status()?);
         data.push(self.uidnext_status()?);
-        self.unseen_first_status()?
-            .map(|unseen_status| data.push(unseen_status));
+        if self.is_condstore {
+            data.push(self.highestmodseq_status()?);
+        }
+        /*self.unseen_first_status()?
+            .map(|unseen_status| data.push(unseen_status));*/
 
         Ok(data)
     }
@@ -140,50 +178,68 @@ impl MailboxView {
         &mut self,
         sequence_set: &SequenceSet,
         kind: &StoreType,
-        _response: &StoreResponse,
+        response: &StoreResponse,
         flags: &[Flag<'a>],
+        unchanged_since: Option<NonZeroU64>,
         is_uid_store: &bool,
-    ) -> Result<Vec<Body<'static>>> {
-        self.0.sync().await?;
+    ) -> Result<(Vec<Body<'static>>, Vec<NonZeroU32>)> {
+        self.internal.sync().await?;
 
         let flags = flags.iter().map(|x| x.to_string()).collect::<Vec<_>>();
 
         let idx = self.index()?;
-        let mails = idx.fetch(sequence_set, *is_uid_store)?;
-        for mi in mails.iter() {
+        let (editable, in_conflict) = idx
+            .fetch_unchanged_since(sequence_set, unchanged_since, *is_uid_store)?;
+
+        for mi in editable.iter() {
             match kind {
                 StoreType::Add => {
-                    self.0.mailbox.add_flags(mi.uuid, &flags[..]).await?;
+                    self.internal.mailbox.add_flags(mi.uuid, &flags[..]).await?;
                 }
                 StoreType::Remove => {
-                    self.0.mailbox.del_flags(mi.uuid, &flags[..]).await?;
+                    self.internal.mailbox.del_flags(mi.uuid, &flags[..]).await?;
                 }
                 StoreType::Replace => {
-                    self.0.mailbox.set_flags(mi.uuid, &flags[..]).await?;
+                    self.internal.mailbox.set_flags(mi.uuid, &flags[..]).await?;
                 }
             }
         }
 
-        // @TODO: handle _response
-        self.update().await
+        let silence = match response {
+            StoreResponse::Answer => HashSet::new(),
+            StoreResponse::Silent => editable.iter().map(|midx| midx.uuid).collect(),
+        };
+
+        let conflict_id_or_uid = match is_uid_store {
+            true => in_conflict.into_iter().map(|midx| midx.uid).collect(),
+            _ => in_conflict.into_iter().map(|midx| midx.i).collect(),
+        };
+
+        let summary = self.update(UpdateParameters {
+            with_uid: *is_uid_store,
+            with_modseq: unchanged_since.is_some(),
+            silence,
+        }).await?;
+
+        Ok((summary, conflict_id_or_uid))
     }
 
     pub async fn expunge(&mut self) -> Result<Vec<Body<'static>>> {
-        self.0.sync().await?;
-        let state = self.0.peek().await;
+        self.internal.sync().await?;
+        let state = self.internal.peek().await;
 
         let deleted_flag = Flag::Deleted.to_string();
         let msgs = state
             .table
             .iter()
-            .filter(|(_uuid, (_uid, flags))| flags.iter().any(|x| *x == deleted_flag))
+            .filter(|(_uuid, (_uid, _modseq, flags))| flags.iter().any(|x| *x == deleted_flag))
             .map(|(uuid, _)| *uuid);
 
         for msg in msgs {
-            self.0.mailbox.delete(msg).await?;
+            self.internal.mailbox.delete(msg).await?;
         }
 
-        self.update().await
+        self.update(UpdateParameters::default()).await
     }
 
     pub async fn copy(
@@ -197,7 +253,7 @@ impl MailboxView {
 
         let mut new_uuids = vec![];
         for mi in mails.iter() {
-            new_uuids.push(to.copy_from(&self.0.mailbox, mi.uuid).await?);
+            new_uuids.push(to.copy_from(&self.internal.mailbox, mi.uuid).await?);
         }
 
         let mut ret = vec![];
@@ -224,7 +280,7 @@ impl MailboxView {
         let mails = idx.fetch(sequence_set, *is_uid_copy)?;
 
         for mi in mails.iter() {
-            to.move_from(&self.0.mailbox, mi.uuid).await?;
+            to.move_from(&self.internal.mailbox, mi.uuid).await?;
         }
 
         let mut ret = vec![];
@@ -238,7 +294,10 @@ impl MailboxView {
             ret.push((mi.uid, dest_uid));
         }
 
-        let update = self.update().await?;
+        let update = self.update(UpdateParameters {
+            with_uid: *is_uid_copy,
+            ..UpdateParameters::default()
+        }).await?;
 
         Ok((to_state.uidvalidity, ret, update))
     }
@@ -248,27 +307,32 @@ impl MailboxView {
     pub async fn fetch<'b>(
         &self,
         sequence_set: &SequenceSet,
-        attributes: &'b MacroOrMessageDataItemNames<'static>,
+        ap: &AttributesProxy,
+        changed_since: Option<NonZeroU64>,
         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 ap = AttributesProxy::new(attributes, *is_uid_fetch);
         let query_scope = match ap.need_body() {
             true => QueryScope::Full,
             _ => QueryScope::Partial,
         };
         tracing::debug!("Query scope {:?}", query_scope);
         let idx = self.index()?;
-        let mail_idx_list = idx.fetch(sequence_set, *is_uid_fetch)?;
+        let mail_idx_list = idx.fetch_changed_since(
+            sequence_set, 
+            changed_since, 
+            *is_uid_fetch
+        )?;
 
         // [2/6] Fetch the emails
         let uuids = mail_idx_list
             .iter()
             .map(|midx| midx.uuid)
             .collect::<Vec<_>>();
-        let query_result = self.0.query(&uuids, query_scope).fetch().await?;
+        let query_result = self.internal.query(&uuids, query_scope).fetch().await?;
 
         // [3/6] Derive an IMAP-specific view from the results, apply the filters
         let views = query_result
@@ -294,7 +358,7 @@ impl MailboxView {
             .filter(|(_mv, seen)| matches!(seen, SeenFlag::MustAdd))
             .map(|(mv, _seen)| async move {
                 let seen_flag = Flag::Seen.to_string();
-                self.0
+                self.internal
                     .mailbox
                     .add_flags(*mv.query_result.uuid(), &[seen_flag])
                     .await?;
@@ -316,7 +380,7 @@ impl MailboxView {
         _charset: &Option<Charset<'a>>,
         search_key: &SearchKey<'a>,
         uid: bool,
-    ) -> Result<Vec<Body<'static>>> {
+    ) -> Result<(Vec<Body<'static>>, bool)> {
         // 1. Compute the subset of sequence identifiers we need to fetch
         // based on the search query
         let crit = search::Criteria(search_key);
@@ -332,20 +396,30 @@ impl MailboxView {
         // 4. Fetch additional info about the emails
         let query_scope = crit.query_scope();
         let uuids = to_fetch.iter().map(|midx| midx.uuid).collect::<Vec<_>>();
-        let query_result = self.0.query(&uuids, query_scope).fetch().await?;
+        let query_result = self.internal.query(&uuids, query_scope).fetch().await?;
 
         // 5. If needed, filter the selection based on the body
         let kept_query = crit.filter_on_query(&to_fetch, &query_result)?;
 
         // 6. Format the result according to the client's taste:
         // either return UID or ID.
-        let final_selection = kept_idx.into_iter().chain(kept_query.into_iter());
+        let final_selection = kept_idx.iter().chain(kept_query.iter());
         let selection_fmt = match uid {
             true => final_selection.map(|in_idx| in_idx.uid).collect(),
             _ => final_selection.map(|in_idx| in_idx.i).collect(),
         };
 
-        Ok(vec![Body::Data(Data::Search(selection_fmt))])
+        // 7. Add the modseq entry if needed
+        let is_modseq = crit.is_modseq();
+        let maybe_modseq = match is_modseq {
+            true => {
+                let final_selection = kept_idx.iter().chain(kept_query.iter());
+                final_selection.map(|in_idx| in_idx.modseq).max().map(|r| NonZeroU64::try_from(r)).transpose()?
+            },
+            _ => None,
+        };
+
+        Ok((vec![Body::Data(Data::Search(selection_fmt, maybe_modseq))], is_modseq))
     }
 
     // ----
@@ -354,7 +428,7 @@ impl MailboxView {
     /// It's not trivial to refactor the code to do that, so we are doing
     /// some useless computation for now...
     fn index<'a>(&'a self) -> Result<Index<'a>> {
-        Index::new(&self.0.snapshot)
+        Index::new(&self.internal.snapshot)
     }
 
     /// Produce an OK [UIDVALIDITY _] message corresponding to `known_state`
@@ -369,7 +443,7 @@ impl MailboxView {
     }
 
     pub(crate) fn uidvalidity(&self) -> ImapUidvalidity {
-        self.0.snapshot.uidvalidity
+        self.internal.snapshot.uidvalidity
     }
 
     /// Produce an OK [UIDNEXT _] message corresponding to `known_state`
@@ -384,7 +458,19 @@ impl MailboxView {
     }
 
     pub(crate) fn uidnext(&self) -> ImapUid {
-        self.0.snapshot.uidnext
+        self.internal.snapshot.uidnext
+    }
+
+    pub(crate) fn highestmodseq_status(&self) -> Result<Body<'static>> {
+        Ok(Body::Status(Status::ok(
+            None, 
+            Some(Code::Other(CodeOther::unvalidated(format!("HIGHESTMODSEQ {}", self.highestmodseq()).into_bytes()))),
+            "Highest",
+        )?))
+    }
+
+    pub(crate) fn highestmodseq(&self) -> ModSeq {
+        self.internal.snapshot.highestmodseq
     }
 
     /// Produce an EXISTS message corresponding to the number of mails
@@ -394,7 +480,7 @@ impl MailboxView {
     }
 
     pub(crate) fn exists(&self) -> Result<u32> {
-        Ok(u32::try_from(self.0.snapshot.idx_by_uid.len())?)
+        Ok(u32::try_from(self.internal.snapshot.idx_by_uid.len())?)
     }
 
     /// Produce a RECENT message corresponding to the number of
@@ -403,6 +489,7 @@ impl MailboxView {
         Ok(Body::Data(Data::Recent(self.recent()?)))
     }
 
+    #[allow(dead_code)]
     fn unseen_first_status(&self) -> Result<Option<Body<'static>>> {
         Ok(self
             .unseen_first()?
@@ -412,21 +499,22 @@ impl MailboxView {
             .transpose()?)
     }
 
+    #[allow(dead_code)]
     fn unseen_first(&self) -> Result<Option<NonZeroU32>> {
         Ok(self
-            .0
+            .internal
             .snapshot
             .table
             .values()
             .enumerate()
-            .find(|(_i, (_imap_uid, flags))| !flags.contains(&"\\Seen".to_string()))
+            .find(|(_i, (_imap_uid, _modseq, flags))| !flags.contains(&"\\Seen".to_string()))
             .map(|(i, _)| NonZeroU32::try_from(i as u32 + 1))
             .transpose()?)
     }
 
     pub(crate) fn recent(&self) -> Result<u32> {
         let recent = self
-            .0
+            .internal
             .snapshot
             .idx_by_flag
             .get(&"\\Recent".to_string())
@@ -443,7 +531,7 @@ 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
-            .0
+            .internal
             .snapshot
             .idx_by_flag
             .flags()
@@ -483,9 +571,9 @@ impl MailboxView {
     }
 
     pub(crate) fn unseen_count(&self) -> usize {
-        let total = self.0.snapshot.table.len();
+        let total = self.internal.snapshot.table.len();
         let seen = self
-            .0
+            .internal
             .snapshot
             .idx_by_flag
             .get(&Flag::Seen.to_string())
@@ -524,6 +612,7 @@ mod tests {
                     peek: false,
                 },
             ]),
+            &[],
             false,
         );
 
@@ -535,12 +624,13 @@ mod tests {
             rfc822_size: 8usize,
         };
 
-        let index_entry = (NonZeroU32::MIN, vec![]);
+        let index_entry = (NonZeroU32::MIN, NonZeroU64::MIN, vec![]);
         let mail_in_idx = MailIndex {
             i: NonZeroU32::MIN,
             uid: index_entry.0,
+            modseq: index_entry.1,
             uuid: unique_ident::gen_ident(),
-            flags: &index_entry.1,
+            flags: &index_entry.2,
         };
         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 qr = QueryResult::FullResult {
diff --git a/src/imap/mod.rs b/src/imap/mod.rs
index 2640183..61a265a 100644
--- a/src/imap/mod.rs
+++ b/src/imap/mod.rs
@@ -175,6 +175,11 @@ async fn client(mut ctx: ClientContext) -> Result<()> {
                         }
                     }
                 },
+                flow => {
+                    server.enqueue_status(Status::bye(None, "Unsupported server flow event").unwrap());
+                    tracing::error!("session task exited for {:?} due to unsupported flow {:?}", ctx.addr, flow);
+
+                }
             },
 
             // Managing response generated by Aerogramme
diff --git a/src/imap/search.rs b/src/imap/search.rs
index c4888d0..61cbad5 100644
--- a/src/imap/search.rs
+++ b/src/imap/search.rs
@@ -1,8 +1,8 @@
-use std::num::NonZeroU32;
+use std::num::{NonZeroU32, NonZeroU64};
 
 use anyhow::Result;
 use imap_codec::imap_types::core::NonEmptyVec;
-use imap_codec::imap_types::search::SearchKey;
+use imap_codec::imap_types::search::{SearchKey, MetadataItemSearch};
 use imap_codec::imap_types::sequence::{SeqOrUid, Sequence, SequenceSet};
 
 use crate::imap::index::MailIndex;
@@ -112,6 +112,17 @@ impl<'a> Criteria<'a> {
         }
     }
 
+    pub fn is_modseq(&self) -> bool {
+        use SearchKey::*;
+        match self.0 {
+            And(and_list) => and_list.as_ref().iter().any(|child| Criteria(child).is_modseq()),
+            Or(left, right) => Criteria(left).is_modseq() || Criteria(right).is_modseq(),
+            Not(child) => Criteria(child).is_modseq(),
+            ModSeq { .. } => true,
+            _ => false,
+        } 
+    }
+
     /// Returns emails that we now for sure we want to keep
     /// but also a second list of emails we need to investigate further by
     /// fetching some remote data
@@ -176,6 +187,7 @@ impl<'a> Criteria<'a> {
             // Sequence logic
             maybe_seq if is_sk_seq(maybe_seq) => is_keep_seq(maybe_seq, midx).into(),
             maybe_flag if is_sk_flag(maybe_flag) => is_keep_flag(maybe_flag, midx).into(),
+            ModSeq { metadata_item , modseq } => is_keep_modseq(metadata_item, modseq, midx).into(),
 
             // All the stuff we can't evaluate yet
             Bcc(_) | Cc(_) | From(_) | Header(..) | SentBefore(_) | SentOn(_) | SentSince(_)
@@ -210,9 +222,10 @@ impl<'a> Criteria<'a> {
             Not(expr) => !Criteria(expr).is_keep_on_query(mail_view),
             All => true,
 
-            // Reevaluating our previous logic...
+            //@FIXME Reevaluating our previous logic...
             maybe_seq if is_sk_seq(maybe_seq) => is_keep_seq(maybe_seq, &mail_view.in_idx),
             maybe_flag if is_sk_flag(maybe_flag) => is_keep_flag(maybe_flag, &mail_view.in_idx),
+            ModSeq { metadata_item , modseq } => is_keep_modseq(metadata_item, modseq, &mail_view.in_idx).into(),
 
             // Filter on mail meta
             Before(search_naive) => match mail_view.stored_naive_date() {
@@ -318,7 +331,8 @@ fn approx_sequence_set_size(seq_set: &SequenceSet) -> u64 {
 }
 
 // This is wrong as sequence UID can have holes,
-// as we don't know the number of messages in the mailbox also
+// as we don't know the number of messages in the mailbox also 
+// we gave to guess
 fn approx_sequence_size(seq: &Sequence) -> u64 {
     match seq {
         Sequence::Single(_) => 1,
@@ -458,3 +472,10 @@ fn is_keep_seq(sk: &SearchKey, midx: &MailIndex) -> bool {
         _ => unreachable!(),
     }
 }
+
+fn is_keep_modseq(filter: &Option<MetadataItemSearch>, modseq: &NonZeroU64, midx: &MailIndex) -> bool {
+    if filter.is_some() {
+        tracing::warn!(filter=?filter, "Ignoring search metadata filter as it's not supported yet");
+    }
+    modseq <= &midx.modseq 
+}