Store `Message` instances using their events.

I found a test bug! The tests for deleting previously-deleted or previously-expired tests were using the wrong user to try to delete those messages. The tests happened to pass anyways because the message authorship check was done after the message lifecycle check. They would have no longer passed; the tests are fixed to use the sender, instead.

1 files changed, 57 insertions, 13 deletions

diff --git a/src/message/history.rs b/src/message/history.rs
index 2abdf2c..92cecc9 100644
--- a/src/message/history.rs
+++ b/src/message/history.rs
@@ -1,18 +1,67 @@
 use itertools::Itertools as _;
 
 use super::{
-    Message,
+    Body, Id, Message,
     event::{Deleted, Event, Sent},
 };
-use crate::event::Sequence;
+use crate::{
+    conversation::Conversation,
+    event::{Instant, Sequence},
+    user::{self, User},
+};
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct History {
     pub message: Message,
 }
 
+// Lifecycle interface
+impl History {
+    pub fn begin(conversation: &Conversation, sender: &User, body: &Body, sent: Instant) -> Self {
+        Self {
+            message: Message {
+                id: Id::generate(),
+                conversation: conversation.id.clone(),
+                sender: sender.id.clone(),
+                body: body.clone(),
+                sent,
+                deleted: None,
+            },
+        }
+    }
+
+    pub fn delete(self, deleted: Instant) -> Result<Self, DeleteError> {
+        if self.message.deleted.is_none() {
+            Ok(Self {
+                message: Message {
+                    deleted: Some(deleted),
+                    ..self.message
+                },
+            })
+        } else {
+            Err(DeleteError::Deleted(self.into()))
+        }
+    }
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum DeleteError {
+    #[error("message {} already deleted", .0.message.id)]
+    // Payload is boxed here to avoid copying an entire `History` around in any errors this error
+    // gets chained into. See <https://rust-lang.github.io/rust-clippy/master/index.html#result_large_err>.
+    Deleted(Box<History>),
+}
+
 // State interface
 impl History {
+    pub fn id(&self) -> &Id {
+        &self.message.id
+    }
+
+    pub fn sender(&self) -> &user::Id {
+        &self.message.sender
+    }
+
     // Snapshot of this message as it was when sent. (Note to the future: it's okay
     // if this returns a redacted or modified version of the message. If we
     // implement message editing by redacting the original body, then this should
@@ -30,15 +79,16 @@ impl History {
             .filter(Sequence::up_to(sequence.into()))
             .collect()
     }
-
-    // Snapshot of this message as of all events recorded in this history.
-    pub fn as_snapshot(&self) -> Option<Message> {
-        self.events().collect()
-    }
 }
 
 // Events interface
 impl History {
+    pub fn events(&self) -> impl Iterator<Item = Event> + Clone + use<> {
+        [self.sent()]
+            .into_iter()
+            .merge_by(self.deleted(), Sequence::merge)
+    }
+
     fn sent(&self) -> Event {
         Sent {
             message: self.message.clone(),
@@ -55,10 +105,4 @@ impl History {
             .into()
         })
     }
-
-    pub fn events(&self) -> impl Iterator<Item = Event> + use<> {
-        [self.sent()]
-            .into_iter()
-            .merge_by(self.deleted(), Sequence::merge)
-    }
 }