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|
use super::mailbox::MailMeta;
use super::snapshot::FrozenMailbox;
use super::unique_ident::UniqueIdent;
use anyhow::Result;
use futures::stream::{Stream, StreamExt, BoxStream};
use futures::future::FutureExt;
/// Query is in charge of fetching efficiently
/// requested data for a list of emails
pub struct Query<'a, 'b> {
pub frozen: &'a FrozenMailbox,
pub emails: &'b [UniqueIdent],
pub scope: QueryScope,
}
#[derive(Debug)]
pub enum QueryScope {
Index,
Partial,
Full,
}
impl QueryScope {
pub fn union(&self, other: &QueryScope) -> QueryScope {
match (self, other) {
(QueryScope::Full, _) | (_, QueryScope::Full) => QueryScope::Full,
(QueryScope::Partial, _) | (_, QueryScope::Partial) => QueryScope::Partial,
(QueryScope::Index, QueryScope::Index) => QueryScope::Index,
}
}
}
//type QueryResultStream = Box<dyn Stream<Item = Result<QueryResult>>>;
impl<'a, 'b> Query<'a, 'b> {
pub fn fetch(&self) -> BoxStream<Result<QueryResult>> {
match self.scope {
QueryScope::Index => Box::pin(futures::stream::iter(self.emails).map(|&uuid| Ok(QueryResult::IndexResult { uuid }))),
QueryScope::Partial => Box::pin(self.partial()),
QueryScope::Full => Box::pin(self.full()),
}
}
// --- functions below are private *for reasons*
fn partial<'d>(&'d self) -> impl Stream<Item = Result<QueryResult>> + 'd + Send {
async move {
let maybe_meta_list: Result<Vec<MailMeta>> = self.frozen.mailbox.fetch_meta(self.emails).await;
let list_res = maybe_meta_list
.map(|meta_list| meta_list
.into_iter()
.zip(self.emails)
.map(|(metadata, &uuid)| Ok(QueryResult::PartialResult { uuid, metadata }))
.collect()
)
.unwrap_or_else(|e| vec![Err(e)]);
futures::stream::iter(list_res)
}.flatten_stream()
}
fn full<'d>(&'d self) -> impl Stream<Item = Result<QueryResult>> + 'd + Send {
self.partial()
.then(move |maybe_meta| async move {
let meta = maybe_meta?;
let content = self
.frozen
.mailbox
.fetch_full(
*meta.uuid(),
&meta
.metadata()
.expect("meta to be PartialResult")
.message_key,
)
.await?;
Ok(meta.into_full(content).expect("meta to be PartialResult"))
})
}
}
#[derive(Debug, Clone)]
pub enum QueryResult {
IndexResult {
uuid: UniqueIdent,
},
PartialResult {
uuid: UniqueIdent,
metadata: MailMeta,
},
FullResult {
uuid: UniqueIdent,
metadata: MailMeta,
content: Vec<u8>,
},
}
impl QueryResult {
pub fn uuid(&self) -> &UniqueIdent {
match self {
Self::IndexResult { uuid, .. } => uuid,
Self::PartialResult { uuid, .. } => uuid,
Self::FullResult { uuid, .. } => uuid,
}
}
pub fn metadata(&self) -> Option<&MailMeta> {
match self {
Self::IndexResult { .. } => None,
Self::PartialResult { metadata, .. } => Some(metadata),
Self::FullResult { metadata, .. } => Some(metadata),
}
}
#[allow(dead_code)]
pub fn content(&self) -> Option<&[u8]> {
match self {
Self::FullResult { content, .. } => Some(content),
_ => None,
}
}
fn into_full(self, content: Vec<u8>) -> Option<Self> {
match self {
Self::PartialResult { uuid, metadata } => Some(Self::FullResult {
uuid,
metadata,
content,
}),
_ => None,
}
}
}
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