import type { CapturedEventEvidence } from "./event-evidence-capture.js";

export async function captureMediaStreamFrame(
  stream: MediaStream,
  now: () => number = Date.now,
): Promise<CapturedEventEvidence> {
  const track = stream.getVideoTracks()[0];
  if (!track || track.readyState === "ended") {
    throw new Error("screen-share video track is unavailable");
  }
  const video = document.createElement("video");
  video.muted = true;
  video.playsInline = true;
  video.srcObject = stream;
  try {
    await Promise.race([
      video.play(),
      new Promise<never>((_, reject) =>
        setTimeout(() => reject(new Error("screen frame timed out")), 2_000),
      ),
    ]);
    if (video.readyState < HTMLMediaElement.HAVE_CURRENT_DATA) {
      await Promise.race([
        new Promise<void>((resolve) =>
          video.addEventListener("loadeddata", () => resolve(), { once: true }),
        ),
        new Promise<never>((_, reject) =>
          setTimeout(() => reject(new Error("screen frame timed out")), 2_000),
        ),
      ]);
    }
    const settings = track.getSettings();
    const width = video.videoWidth || settings.width || 0;
    const height = video.videoHeight || settings.height || 0;
    if (!width || !height) throw new Error("screen frame has no dimensions");
    const canvas = document.createElement("canvas");
    const scale = Math.min(1, 1280 / width);
    canvas.width = Math.max(1, Math.round(width * scale));
    canvas.height = Math.max(1, Math.round(height * scale));
    const context = canvas.getContext("2d");
    if (!context) throw new Error("screen frame canvas is unavailable");
    const capturedAt = now();
    context.drawImage(video, 0, 0, canvas.width, canvas.height);
    const blob = await canvasToJpeg(canvas);
    return {
      blob,
      capturedAt,
      width: canvas.width,
      height: canvas.height,
      source: "screen-share",
      syncQuality: "exact",
    };
  } finally {
    video.pause();
    video.srcObject = null;
  }
}

function canvasToJpeg(canvas: HTMLCanvasElement): Promise<Blob> {
  return new Promise((resolve, reject) => {
    canvas.toBlob(
      (blob) =>
        blob
          ? resolve(blob)
          : reject(new Error("screen frame JPEG encoding failed")),
      "image/jpeg",
      0.82,
    );
  });
}