6 files changed, 31 insertions, 15 deletions
diff --git a/src/channel/app.rs b/src/channel/app.rs
index dc9e584..e3b169c 100644
--- a/src/channel/app.rs
+++ b/src/channel/app.rs
@@ -48,14 +48,14 @@ impl<'a> Channels<'a> {
     // This function is careless with respect to time, and gets you the channel as
     // it exists in the specific moment when you call it.
     pub async fn get(&self, channel: &Id) -> Result<Channel, Error> {
-        let not_found = || Error::NotFound(channel.clone());
-        let deleted = || Error::Deleted(channel.clone());
+        let to_not_found = || Error::NotFound(channel.clone());
+        let to_deleted = || Error::Deleted(channel.clone());
 
         let mut tx = self.db.begin().await?;
-        let channel = tx.channels().by_id(channel).await.not_found(not_found)?;
+        let channel = tx.channels().by_id(channel).await.not_found(to_not_found)?;
         tx.commit().await?;
 
-        channel.as_snapshot().ok_or_else(deleted)
+        channel.as_snapshot().ok_or_else(to_deleted)
     }
 
     pub async fn delete(&self, channel: &Id, deleted_at: &DateTime) -> Result<(), DeleteError> {
diff --git a/src/channel/handlers/send/mod.rs b/src/channel/handlers/send/mod.rs
index aa241e2..bde39e5 100644
--- a/src/channel/handlers/send/mod.rs
+++ b/src/channel/handlers/send/mod.rs
@@ -54,7 +54,9 @@ impl IntoResponse for Error {
     fn into_response(self) -> response::Response {
         let Self(error) = self;
         match error {
-            SendError::ChannelNotFound(_) => NotFound(error).into_response(),
+            SendError::ChannelNotFound(_) | SendError::ChannelDeleted(_) => {
+                NotFound(error).into_response()
+            }
             SendError::Name(_) | SendError::Database(_) => Internal::from(error).into_response(),
         }
     }
diff --git a/src/channel/handlers/send/test.rs b/src/channel/handlers/send/test.rs
index d77e07d..70d45eb 100644
--- a/src/channel/handlers/send/test.rs
+++ b/src/channel/handlers/send/test.rs
@@ -125,6 +125,6 @@ async fn deleted_channel() {
 
     assert!(matches!(
         error,
-        SendError::ChannelNotFound(error_channel) if channel.id == error_channel
+        SendError::ChannelDeleted(error_channel) if channel.id == error_channel
     ));
 }
diff --git a/src/channel/history.rs b/src/channel/history.rs
index 7f18e45..85da5a5 100644
--- a/src/channel/history.rs
+++ b/src/channel/history.rs
@@ -27,6 +27,15 @@ impl History {
         self.channel.clone()
     }
 
+    pub fn as_of<S>(&self, sequence: S) -> Option<Channel>
+    where
+        S: Into<Sequence>,
+    {
+        self.events()
+            .filter(Sequence::up_to(sequence.into()))
+            .collect()
+    }
+
     // Snapshot of this channel as of all events recorded in this history.
     pub fn as_snapshot(&self) -> Option<Channel> {
         self.events().collect()
diff --git a/src/message/app.rs b/src/message/app.rs
index 3c74628..9792c8f 100644
--- a/src/message/app.rs
+++ b/src/message/app.rs
@@ -29,13 +29,17 @@ impl<'a> Messages<'a> {
         sent_at: &DateTime,
         body: &Body,
     ) -> Result<Message, SendError> {
+        let to_not_found = || SendError::ChannelNotFound(channel.clone());
+        let to_deleted = || SendError::ChannelDeleted(channel.clone());
+
         let mut tx = self.db.begin().await?;
-        let channel = tx
-            .channels()
-            .by_id(channel)
-            .await
-            .not_found(|| SendError::ChannelNotFound(channel.clone()))?;
+        let channel = tx.channels().by_id(channel).await.not_found(to_not_found)?;
+
+        // Ordering: don't bother allocating a sequence number before we know the channel might
+        // exist.
         let sent = tx.sequence().next(sent_at).await?;
+        let channel = channel.as_of(sent).ok_or_else(to_deleted)?;
+
         let message = tx.messages().create(&channel, sender, &sent, body).await?;
         tx.commit().await?;
 
@@ -126,6 +130,8 @@ impl<'a> Messages<'a> {
 pub enum SendError {
     #[error("channel {0} not found")]
     ChannelNotFound(channel::Id),
+    #[error("channel {0} deleted")]
+    ChannelDeleted(channel::Id),
     #[error(transparent)]
     Database(#[from] sqlx::Error),
     #[error(transparent)]
diff --git a/src/message/repo.rs b/src/message/repo.rs
index 9a4f72f..e753134 100644
--- a/src/message/repo.rs
+++ b/src/message/repo.rs
@@ -2,7 +2,7 @@ use sqlx::{SqliteConnection, Transaction, sqlite::Sqlite};
 
 use super::{Body, History, Id, snapshot::Message};
 use crate::{
-    channel,
+    channel::{self, Channel},
     clock::DateTime,
     event::{Instant, Sequence},
     user::{self, User},
@@ -23,13 +23,12 @@ pub struct Messages<'t>(&'t mut SqliteConnection);
 impl Messages<'_> {
     pub async fn create(
         &mut self,
-        channel: &channel::History,
+        channel: &Channel,
         sender: &User,
         sent: &Instant,
         body: &Body,
     ) -> Result<History, sqlx::Error> {
         let id = Id::generate();
-        let channel_id = channel.id();
 
         let message = sqlx::query!(
             r#"
@@ -45,7 +44,7 @@ impl Messages<'_> {
                     body as "body: Body"
             "#,
             id,
-            channel_id,
+            channel.id,
             sender.id,
             sent.at,
             sent.sequence,