cache the dictionary

Author: neverRare

src/dictionary/parallel_parser.ts

@@ -18,45 +18,53 @@ class ParserWorker {
     new URL("./worker.ts", import.meta.url),
     { type: "module" },
   );
+  #cachedSource = "";
+  #cachedDictionary: Dictionary = new Map();
   [Symbol.dispose]() {
     this.#worker.terminate();
   }
   parse(position: number, source: string): Promise<Dictionary> {
-    return new Promise((resolve, reject) => {
-      const messageCallback = (event: MessageEvent) => {
-        const result = event.data as Result;
-        switch (result.type) {
-          case "value":
-            resolve(result.value);
-            break;
-          case "error":
-            reject(
-              new AggregateError(
-                result.error.map((result) =>
-                  new PositionedError(result.message, {
-                    position: mapNullable(
-                      result.position,
-                      ({ position: offsetPosition, length }) => ({
-                        position: position + offsetPosition,
-                        length,
-                      }),
-                    ) ?? undefined,
-                  })
+    if (this.#cachedSource === source) {
+      return Promise.resolve(this.#cachedDictionary);
+    } else {
+      return new Promise((resolve, reject) => {
+        const messageCallback = (event: MessageEvent) => {
+          const result = event.data as Result;
+          switch (result.type) {
+            case "value":
+              resolve(result.value);
+              this.#cachedSource = source;
+              this.#cachedDictionary = result.value;
+              break;
+            case "error":
+              reject(
+                new AggregateError(
+                  result.error.map((result) =>
+                    new PositionedError(result.message, {
+                      position: mapNullable(
+                        result.position,
+                        ({ position: offsetPosition, length }) => ({
+                          position: position + offsetPosition,
+                          length,
+                        }),
+                      ) ?? undefined,
+                    })
+                  ),
                 ),
-              ),
-            );
-            break;
-        }
-        this.#worker.removeEventListener("message", messageCallback);
-      };
-      this.#worker.addEventListener("message", messageCallback);
-      const errorCallback = (event: ErrorEvent) => {
-        reject(event.error);
-        this.#worker.removeEventListener("error", errorCallback);
-      };
-      this.#worker.addEventListener("error", errorCallback);
-      this.#worker.postMessage(source);
-    });
+              );
+              break;
+          }
+          this.#worker.removeEventListener("message", messageCallback);
+        };
+        this.#worker.addEventListener("message", messageCallback);
+        const errorCallback = (event: ErrorEvent) => {
+          reject(event.error);
+          this.#worker.removeEventListener("error", errorCallback);
+        };
+        this.#worker.addEventListener("error", errorCallback);
+        this.#worker.postMessage(source);
+      });
+    }
   }
 }
 export class Parser {