"use client";

/**
 * 摄像头预览:纯前端 getUserMedia 视频流,供调试抽屉的「视频流」视图使用。
 *
 * 与 use-voice-preview 分离:这里负责摄像头设备枚举与本地预览;开始视觉会话时,
 * 调用方会把这条 video track 加进语音 WebRTC PeerConnection。
 */

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

const CAMERA_VIDEO_CONSTRAINTS: MediaTrackConstraints = {
  width: { ideal: 640, max: 640 },
  height: { ideal: 360, max: 480 },
  frameRate: { ideal: 12, max: 15 },
};

function cameraErrorMessage(error: unknown): string {
  if (error instanceof DOMException) {
    if (error.name === "NotAllowedError")
      return "摄像头权限被拒绝，请在浏览器网站设置中允许使用摄像头。";
    if (error.name === "NotFoundError")
      return "未检测到可用摄像头，请连接或启用摄像头后重试。";
    if (error.name === "NotReadableError")
      return "摄像头正被其他应用占用，或系统未允许浏览器访问摄像头。";
  }
  if (error instanceof Error && error.message) return error.message;
  return "无法访问摄像头。";
}

export function useCameraPreview() {
  const [stream, setStream] = useState<MediaStream | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [starting, setStarting] = useState(false);
  const [devices, setDevices] = useState<MediaDeviceInfo[]>([]);
  const [deviceId, setDeviceId] = useState("");
  const streamRef = useRef<MediaStream | null>(null);
  const deviceIdRef = useRef("");

  const active = Boolean(stream);

  const refreshCameras = useCallback(async () => {
    if (!navigator.mediaDevices?.enumerateDevices) return;
    try {
      const list = await navigator.mediaDevices.enumerateDevices();
      setDevices(list.filter((d) => d.kind === "videoinput" && d.deviceId));
    } catch {
      /* 忽略枚举失败 */
    }
  }, []);

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

  const start = useCallback(async (): Promise<MediaStream | null> => {
    if (streamRef.current) return streamRef.current;
    setError(null);
    if (!window.isSecureContext || !navigator.mediaDevices?.getUserMedia) {
      setError("当前页面无法访问摄像头，请通过 https 或 localhost 访问。");
      return null;
    }
    setStarting(true);
    try {
      const id = deviceIdRef.current;
      const videoConstraints: MediaTrackConstraints = {
        ...CAMERA_VIDEO_CONSTRAINTS,
        ...(id ? { deviceId: { exact: id } } : {}),
      };
      const media = await navigator.mediaDevices.getUserMedia({
        video: videoConstraints,
      });
      streamRef.current = media;
      setStream(media);
      void refreshCameras();
      return media;
    } catch (mediaError) {
      setError(cameraErrorMessage(mediaError));
      return null;
    } finally {
      setStarting(false);
    }
  }, [refreshCameras]);

  const selectCamera = useCallback(
    async (id: string): Promise<MediaStream | null> => {
      deviceIdRef.current = id;
      setDeviceId(id);
      if (streamRef.current) {
        stop();
        return await start();
      }
      return null;
    },
    [start, stop],
  );

  useEffect(() => {
    if (!navigator.mediaDevices?.enumerateDevices) return;
    // eslint-disable-next-line react-hooks/set-state-in-effect
    void refreshCameras();
    navigator.mediaDevices.addEventListener("devicechange", refreshCameras);
    return () => {
      navigator.mediaDevices.removeEventListener("devicechange", refreshCameras);
    };
  }, [refreshCameras]);

  useEffect(() => stop, [stop]);

  return {
    stream,
    error,
    starting,
    devices,
    deviceId,
    active,
    start,
    stop,
    selectCamera,
  };
}

export type CameraPreview = ReturnType<typeof useCameraPreview>;