1 files changed, 89 insertions, 0 deletions
diff --git a/extension/react-app/src/util/editCache.ts b/extension/react-app/src/util/editCache.ts
new file mode 100644
index 00000000..b8071127
--- /dev/null
+++ b/extension/react-app/src/util/editCache.ts
@@ -0,0 +1,89 @@
+import { useApi } from "../util/api";
+import { FileEdit, SerializedDebugContext } from "../../../src/client";
+import { useCallback, useEffect, useState } from "react";
+
+export function useEditCache() {
+  const { debugApi } = useApi();
+
+  const fetchNewEdit = useCallback(
+    async (debugContext: SerializedDebugContext) => {
+      return (
+        await debugApi?.editEndpointDebugEditPost({
+          serializedDebugContext: debugContext,
+        })
+      )?.completion;
+    },
+    [debugApi]
+  );
+
+  const [editCache, setEditCache] = useState(new EditCache(fetchNewEdit));
+
+  useEffect(() => {
+    setEditCache(new EditCache(fetchNewEdit));
+  }, [fetchNewEdit]);
+
+  return editCache;
+}
+
+/**
+ * Stores preloaded edits, invalidating based off of debug context changes
+ */
+class EditCache {
+  private _lastDebugContext: SerializedDebugContext | undefined;
+  private _cachedEdits: FileEdit[] | undefined;
+  private _fetchNewEdit: (
+    debugContext: SerializedDebugContext
+  ) => Promise<FileEdit[] | undefined>;
+  private _debounceTimer: NodeJS.Timeout | undefined;
+
+  private _debugContextChanged(debugContext: SerializedDebugContext): boolean {
+    if (!this._lastDebugContext) {
+      return true;
+    }
+
+    return (
+      JSON.stringify(this._lastDebugContext) !== JSON.stringify(debugContext)
+    );
+  }
+
+  private _debugContextComplete(debugContext: SerializedDebugContext): boolean {
+    return debugContext.rangesInFiles.length > 0;
+  }
+
+  public async preloadEdit(debugContext: SerializedDebugContext) {
+    if (this._debounceTimer) {
+      clearTimeout(this._debounceTimer);
+    }
+    if (
+      this._debugContextComplete(debugContext) &&
+      this._debugContextChanged(debugContext)
+    ) {
+      this._debounceTimer = setTimeout(async () => {
+        console.log("Preloading edits");
+        this._cachedEdits = await this._fetchNewEdit(debugContext);
+        this._lastDebugContext = debugContext;
+      }, 200);
+    }
+  }
+
+  public async getEdit(
+    debugContext: SerializedDebugContext
+  ): Promise<FileEdit[]> {
+    if (this._debugContextChanged(debugContext)) {
+      console.log("Cache miss");
+      this._cachedEdits = await this._fetchNewEdit(debugContext);
+    } else {
+      console.log("Cache hit");
+    }
+
+    return this._cachedEdits!;
+  }
+
+  constructor(
+    fetchNewEdit: (
+      debugContext: SerializedDebugContext
+    ) => Promise<FileEdit[] | undefined>
+  ) {
+    this._fetchNewEdit = fetchNewEdit;
+  }
+}