feat(plugin-stack-persistence): compose strategies

Author: ENvironmentSet

.changeset/shaggy-foxes-compose.md

@@ -0,0 +1,5 @@
+---
+"@stackflow/plugin-stack-persistence": minor
+---
+
+Add `composeStrategies` to combine keyed snapshot metadata reuse strategies.

extensions/plugin-stack-persistence/src/composeStrategies.ts

@@ -0,0 +1,53 @@
+import type { StackSnapshotStrategy } from "./StackSnapshotStrategy";
+
+type StrategiesMetadata<
+  Strategies extends Record<string, StackSnapshotStrategy<unknown>>,
+> = {
+  [Key in keyof Strategies]: Strategies[Key] extends StackSnapshotStrategy<
+    infer Metadata
+  >
+    ? Metadata
+    : never;
+};
+
+function isMetadataRecord(
+  metadata: unknown,
+): metadata is Record<string, unknown> {
+  return (
+    typeof metadata === "object" &&
+    metadata !== null &&
+    !Array.isArray(metadata)
+  );
+}
+
+export function composeStrategies<
+  Strategies extends Record<string, StackSnapshotStrategy<unknown>>,
+>(
+  strategies: Strategies,
+): StackSnapshotStrategy<StrategiesMetadata<Strategies>> {
+  const keys = Object.keys(strategies) as Array<keyof Strategies>;
+
+  return {
+    createMetadata(args) {
+      return Object.fromEntries(
+        keys.map((key) => [key, strategies[key].createMetadata(args)]),
+      ) as StrategiesMetadata<Strategies>;
+    },
+    shouldReuse({ record, initialContext }) {
+      if (!isMetadataRecord(record.metadata)) return false;
+      if (!keys.every((key) => Object.hasOwn(record.metadata, key))) {
+        return false;
+      }
+
+      return keys.every((key) => {
+        return strategies[key].shouldReuse({
+          record: {
+            ...record,
+            metadata: record.metadata[key],
+          },
+          initialContext,
+        });
+      });
+    },
+  };
+}

extensions/plugin-stack-persistence/src/index.ts

@@ -1,6 +1,7 @@
+export { composeStrategies } from "./composeStrategies";
 export {
+  StackSnapshotRecordLoadError,
   StackSnapshotRecordSaveError,
-  StackSnapshotRecordLoadError
 } from "./errors";
 export { StackSnapshotRecord } from "./StackSnapshotRecord";
 export { StackSnapshotStorage } from "./StackSnapshotStorage";