import type { ExportRequest, WorkerResult } from "./types";
let worker: Worker | undefined;
let nextId = 0;
const pending = new Map<
  number,
  {
    resolve: (blob: Blob) => void;
    reject: (error: Error) => void;
    format: string;
  }
>();
export function renderImage(request: ExportRequest): Promise<Blob> {
  if (!worker) {
    worker = new Worker(new URL("./export.worker.ts", import.meta.url), {
      type: "module",
    });
    worker.onmessage = ({ data }: MessageEvent<WorkerResult>) => {
      const job = pending.get(data.id);
      if (!job) return;
      pending.delete(data.id);
      if (data.error !== undefined) job.reject(new Error(data.error));
      else job.resolve(new Blob([data.bytes], { type: `image/${job.format}` }));
    };
    worker.onerror = () => {
      worker?.terminate();
      worker = undefined;
      for (const job of pending.values())
        job.reject(new Error("Image renderer failed"));
      pending.clear();
    };
  }
  return new Promise((resolve, reject) => {
    const id = ++nextId;
    pending.set(id, { resolve, reject, format: request.format });
    try {
      worker!.postMessage({ id, request, origin: window.location.origin });
    } catch (error) {
      pending.delete(id);
      reject(error);
    }
  });
}
export function downloadImage(blob: Blob, fileName: string) {
  const url = URL.createObjectURL(blob);
  const link = document.createElement("a");
  link.download = fileName.replace(/[\\/:*?"<>|]/gu, "-");
  link.href = url;
  document.body.append(link);
  link.click();
  link.remove();
  window.setTimeout(() => URL.revokeObjectURL(url), 1000);
}