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

export interface WebcamState {
  videoRef: React.RefObject<HTMLVideoElement | null>;
  isReady: boolean;
  error: string | null;
  facingMode: 'user' | 'environment';
  switchCamera: () => void;
}

/**
 * Hook to access the device webcam.
 * Supports front/back camera toggle for mobile devices.
 */
export function useWebcam(): WebcamState {
  const videoRef = useRef<HTMLVideoElement | null>(null);
  const streamRef = useRef<MediaStream | null>(null);
  const [isReady, setIsReady] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [facingMode, setFacingMode] = useState<'user' | 'environment'>('user');

  const startCamera = useCallback(async (mode: 'user' | 'environment') => {
    // Stop any existing stream first
    streamRef.current?.getTracks().forEach(t => t.stop());
    setIsReady(false);
    setError(null);

    try {
      const stream = await navigator.mediaDevices.getUserMedia({
        video: { width: { ideal: 1280 }, height: { ideal: 720 }, facingMode: mode },
        audio: false,
      });
      streamRef.current = stream;

      if (videoRef.current) {
        videoRef.current.srcObject = stream;
        videoRef.current.onloadedmetadata = () => {
          videoRef.current?.play();
          setIsReady(true);
        };
      }
    } catch (err) {
      const msg = err instanceof Error ? err.message : String(err);
      setError(
        msg.includes('Permission')
          ? 'Camera permission denied. Please allow camera access and reload.'
          : `Camera error: ${msg}`
      );
    }
  }, []);

  // Start camera on mount and whenever facingMode changes
  useEffect(() => {
    startCamera(facingMode);
    return () => {
      streamRef.current?.getTracks().forEach(t => t.stop());
    };
  }, [facingMode, startCamera]);

  const switchCamera = useCallback(() => {
    setFacingMode(prev => (prev === 'user' ? 'environment' : 'user'));
  }, []);

  return { videoRef, isReady, error, facingMode, switchCamera };
}