test(kanban): prove divergent rebase conflict

req: sync/011

examples/kanban/src/main.rs

@@ -67,13 +67,40 @@ impl CommandId {
     }
 }
 
+#[derive(Clone, Copy, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(rename_all = "lowercase")]
+enum CanonicalColumn {
+    Todo,
+    Doing,
+    Done,
+}
+
+impl CanonicalColumn {
+    fn parse(value: Option<&String>) -> Result<Self, SyncRejection> {
+        match value.map(String::as_str).unwrap_or("done") {
+            "todo" => Ok(Self::Todo),
+            "doing" => Ok(Self::Doing),
+            "done" => Ok(Self::Done),
+            _ => Err(SyncRejection::BadRequest("invalid column")),
+        }
+    }
+
+    fn index(self) -> usize {
+        match self {
+            Self::Todo => 0,
+            Self::Doing => 1,
+            Self::Done => 2,
+        }
+    }
+}
+
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 #[serde(rename_all = "camelCase")]
 struct SyncAcknowledgement {
     command_id: String,
     server_sequence: u64,
     card_id: u64,
-    canonical_column: &'static str,
+    canonical_column: CanonicalColumn,
     status: &'static str,
 }
 
@@ -89,7 +116,7 @@ struct SyncSnapshot {
 #[serde(rename_all = "camelCase")]
 struct SnapshotCard {
     id: u64,
-    column: &'static str,
+    column: CanonicalColumn,
 }
 
 #[derive(Debug)]
@@ -126,6 +153,7 @@ struct PersistedAcknowledgement {
     command_id: String,
     server_sequence: u64,
     card_id: u64,
+    canonical_column: CanonicalColumn,
 }
 
 impl SyncStore {
@@ -154,7 +182,7 @@ impl SyncStore {
                 command_id: stored.command_id,
                 server_sequence: stored.server_sequence,
                 card_id: stored.card_id,
-                canonical_column: "done",
+                canonical_column: stored.canonical_column,
                 status: "accepted",
             };
             if acknowledgements
@@ -221,6 +249,7 @@ impl From<&SyncAcknowledgement> for PersistedAcknowledgement {
             command_id: value.command_id.clone(),
             server_sequence: value.server_sequence,
             card_id: value.card_id,
+            canonical_column: value.canonical_column,
         }
     }
 }
@@ -325,7 +354,7 @@ async fn main() {
             .iter_mut()
             .find(|card| card.id == acknowledgement.card_id)
         {
-            card.column = 2;
+            card.column = acknowledgement.canonical_column.index();
         }
     }
     let state = Arc::new(AppState {
@@ -447,10 +476,11 @@ async fn sync_command(
         .and_then(|value| value.parse::<u64>().ok())
         .filter(|value| *value > 0)
         .ok_or(SyncRejection::BadRequest("invalid card_id"))?;
+    let canonical_column = CanonicalColumn::parse(params.get("column"))?;
 
     let mut sync = state.sync.lock().unwrap();
     if let Some(existing) = sync.acknowledgements.get(&command_id) {
-        if existing.card_id != card_id {
+        if existing.card_id != card_id || existing.canonical_column != canonical_column {
             return Err(SyncRejection::Conflict(
                 "command_id was already used for a different payload",
             ));
@@ -479,7 +509,7 @@ async fn sync_command(
         command_id: command_id.0.clone(),
         server_sequence: sync.next_sequence,
         card_id,
-        canonical_column: "done",
+        canonical_column,
         status: "accepted",
     };
     if let Some(store) = &state.sync_store {
@@ -488,7 +518,7 @@ async fn sync_command(
             SyncRejection::Storage
         })?;
     }
-    board.cards[card_index].column = 2;
+    board.cards[card_index].column = canonical_column.index();
     sync.next_sequence += 1;
     sync.acknowledgements
         .insert(command_id, acknowledgement.clone());
@@ -504,7 +534,7 @@ async fn sync_snapshot(State(state): State<Arc<AppState>>) -> Json<SyncSnapshot>
         .iter()
         .map(|card| SnapshotCard {
             id: card.id,
-            column: column_name(card.column),
+            column: canonical_column(card.column),
         })
         .collect();
     Json(SyncSnapshot {
@@ -514,11 +544,12 @@ async fn sync_snapshot(State(state): State<Arc<AppState>>) -> Json<SyncSnapshot>
     })
 }
 
-fn column_name(column: usize) -> &'static str {
-    ["todo", "doing", "done"]
-        .get(column)
-        .copied()
-        .unwrap_or("todo")
+fn canonical_column(column: usize) -> CanonicalColumn {
+    match column {
+        1 => CanonicalColumn::Doing,
+        2 => CanonicalColumn::Done,
+        _ => CanonicalColumn::Todo,
+    }
 }
 
 // req: sync/005 req: sync/006 req: sync/007 req: sync/013