feat(sync): replay durable projections from Rust

req: ms/001

req: ms/002

req: ms/003

hemx-sync/src/lib.rs

@@ -417,6 +417,29 @@ impl SyncEffect {
             payload: patch.payload(),
         }])
     }
+
+    /// Apply an optimistic projection now and carry the same ordinary batch in
+    /// the durable patch event so the framework sync runtime can replay it
+    /// after reload before acknowledgement.
+    pub fn durable(patch: FlatPatch, projection: EffectBatch) -> Self {
+        patch.validate().expect("FlatPatch must remain valid");
+        let projection_wire = projection
+            .to_wire()
+            .iter()
+            .map(u8::to_string)
+            .collect::<Vec<_>>()
+            .join(",");
+        let payload = format!(
+            r#"{{"patch":{},"projection":[{projection_wire}]}}"#,
+            patch.payload()
+        );
+        let mut ops = projection.ops;
+        ops.push(Effect::Emit {
+            name: PATCH_EVENT.to_owned(),
+            payload,
+        });
+        Self(ops)
+    }
 }
 
 impl IntoEffect for SyncEffect {
@@ -429,6 +452,24 @@ impl IntoEffect for SyncEffect {
 mod tests {
     use super::*;
 
+    #[test]
+    fn durable_patch_carries_and_applies_ordinary_projection_batch() {
+        let patch =
+            FlatPatch::for_interaction("cardColumn", PatchValue::String("done".into())).unwrap();
+        let projection = Effect::Emit {
+            name: "projected".into(),
+            payload: "card:1".into(),
+        }
+        .into_batch(hemx_core::BuildFingerprint(7));
+        let batch =
+            SyncEffect::durable(patch, projection).into_batch(hemx_core::BuildFingerprint(7));
+        assert_eq!(batch.ops.len(), 2);
+        assert!(matches!(&batch.ops[0], Effect::Emit { name, .. } if name == "projected"));
+        assert!(
+            matches!(&batch.ops[1], Effect::Emit { name, payload } if name == PATCH_EVENT && payload.contains("\"projection\":[") && payload.contains("$hemx-interaction"))
+        );
+    }
+
     #[test]
     fn acknowledgement_updates_atom_and_emits_queue_signal() {
         let atom = Atom::<String>::new(17);