/** Promise-based wrapper around the filter Web Worker. */
import type {
  FilterRequest,
  FilterResponse,
  FilterSuccess,
} from "./filterTypes.ts";

export interface ImageInput {
  width: number;
  height: number;
  rgba: Uint8ClampedArray;
}

export interface FilterClient {
  run(script: string, image: ImageInput): Promise<FilterSuccess>;
  terminate(): void;
}

export function createFilterClient(): FilterClient {
  const worker = new Worker(new URL("./filter.worker.ts", import.meta.url), {
    type: "module",
  });

  let nextId = 1;
  const pending = new Map<
    number,
    { resolve: (r: FilterSuccess) => void; reject: (e: Error) => void }
  >();

  worker.onmessage = (e: MessageEvent<FilterResponse>) => {
    const res = e.data;
    const entry = pending.get(res.id);
    if (!entry) return;
    pending.delete(res.id);
    if (res.ok) {
      entry.resolve(res);
    } else {
      const err = new Error(res.error) as Error & { logs?: string[] };
      err.logs = res.logs;
      entry.reject(err);
    }
  };

  worker.onerror = (e) => {
    // A worker-level error rejects everything in flight.
    const err = new Error(e.message || "Filter worker crashed");
    for (const { reject } of pending.values()) reject(err);
    pending.clear();
  };

  return {
    run(script, image) {
      return new Promise<FilterSuccess>((resolve, reject) => {
        const id = nextId++;
        pending.set(id, { resolve, reject });
        // Copy the bytes so the caller's source image stays intact after the
        // buffer is transferred to the worker.
        const rgba = image.rgba.slice();
        const req: FilterRequest = {
          id,
          script,
          width: image.width,
          height: image.height,
          rgba,
        };
        worker.postMessage(req, [rgba.buffer]);
      });
    },
    terminate() {
      worker.terminate();
      pending.clear();
    },
  };
}