// ============================================================
// CameraManager — 摄像头流采集
// 职责：获取用户摄像头 MediaStream，提供给 VideoPreview 和 EdgeProcessor
// ============================================================

import { useCallback, useRef, useState } from "react";

export interface CameraManagerHandle {
  /** 获取当前视频轨道 */
  stream: MediaStream | null;
  /** 捕获当前帧为 JPEG DataURL */
  captureFrame: () => string | null;
}

export function useCamera() {
  const videoRef = useRef<HTMLVideoElement>(null);
  const [stream, setStream] = useState<MediaStream | null>(null);
  const [error, setError] = useState<string | null>(null);

  const startCamera = useCallback(async () => {
    try {
      const mediaStream = await navigator.mediaDevices.getUserMedia({
        video: { facingMode: "environment", width: 640, height: 480 },
        audio: false,
      });
      setStream(mediaStream);
      if (videoRef.current) {
        videoRef.current.srcObject = mediaStream;
      }
      setError(null);
    } catch (err) {
      const message = err instanceof Error ? err.message : "无法访问摄像头";
      setError(message);
      console.error("[Camera] 获取摄像头失败:", err);
    }
  }, []);

  const stopCamera = useCallback(() => {
    stream?.getTracks().forEach((track) => track.stop());
    setStream(null);
  }, [stream]);

  /** 从 video 元素捕获当前帧为 JPEG DataURL */
  const captureFrame = useCallback((): string | null => {
    const video = videoRef.current;
    if (!video || video.readyState < 2) return null;

    const canvas = document.createElement("canvas");
    canvas.width = video.videoWidth;
    canvas.height = video.videoHeight;
    const ctx = canvas.getContext("2d");
    if (!ctx) return null;

    ctx.drawImage(video, 0, 0);
    return canvas.toDataURL("image/jpeg", 0.7);
  }, []);

  return { videoRef, stream, error, startCamera, stopCamera, captureFrame };
}
