Rename "channel" to "conversation" within the server.

I've split this from the schema and API changes because, frankly, it's huge. Annoyingly so. There are no semantic changes in this, it's all symbol changes, but there are a _lot_ of them because the term "channel" leaks all over everything in a service whose primary role is managing messages sent to channels (now, conversations).

I found a buggy test while working on this! It's not fixed in this commit, because it felt mean to hide a real change in the middle of this much chaff.

1 files changed, 69 insertions, 0 deletions

diff --git a/src/conversation/history.rs b/src/conversation/history.rs
new file mode 100644
index 0000000..601614c
--- /dev/null
+++ b/src/conversation/history.rs
@@ -0,0 +1,69 @@
+use itertools::Itertools as _;
+
+use super::{
+    Conversation, Id,
+    event::{Created, Deleted, Event},
+};
+use crate::event::{Instant, Sequence};
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct History {
+    pub conversation: Conversation,
+    pub deleted: Option<Instant>,
+}
+
+// State interface
+impl History {
+    pub fn id(&self) -> &Id {
+        &self.conversation.id
+    }
+
+    // Snapshot of this conversation as it was when created. (Note to the future:
+    // it's okay if this returns a redacted or modified version of the conversation.
+    // If we implement renames by redacting the original name, then this should
+    // return the renamed conversation, not the original, even if that's not how
+    // it was "as created.")
+    pub fn as_created(&self) -> Conversation {
+        self.conversation.clone()
+    }
+
+    pub fn as_of<S>(&self, sequence: S) -> Option<Conversation>
+    where
+        S: Into<Sequence>,
+    {
+        self.events()
+            .filter(Sequence::up_to(sequence.into()))
+            .collect()
+    }
+
+    // Snapshot of this conversation as of all events recorded in this history.
+    pub fn as_snapshot(&self) -> Option<Conversation> {
+        self.events().collect()
+    }
+}
+
+// Event factories
+impl History {
+    pub fn events(&self) -> impl Iterator<Item = Event> + use<> {
+        [self.created()]
+            .into_iter()
+            .merge_by(self.deleted(), Sequence::merge)
+    }
+
+    fn created(&self) -> Event {
+        Created {
+            conversation: self.conversation.clone(),
+        }
+        .into()
+    }
+
+    fn deleted(&self) -> Option<Event> {
+        self.deleted.map(|instant| {
+            Deleted {
+                instant,
+                id: self.conversation.id.clone(),
+            }
+            .into()
+        })
+    }
+}