'use client';

import React, { useEffect, useRef, useState, useCallback } from 'react';
import { Html5Qrcode } from 'html5-qrcode';
import { X, Camera, AlertCircle, ZoomIn, ZoomOut } from 'lucide-react';

interface BarcodeScannerProps {
  onScan: (value: string) => void;
  onClose: () => void;
}

export default function BarcodeScanner({ onScan, onClose }: BarcodeScannerProps) {
  const containerRef = useRef<HTMLDivElement>(null);
  const [error, setError] = useState('');
  const [zoom, setZoom] = useState(1);
  const [zoomMax, setZoomMax] = useState(3);
  const [supportsZoom, setSupportsZoom] = useState(false);
  const initializedRef = useRef(false);
  const scannerRef = useRef<Html5Qrcode | null>(null);
  const trackRef = useRef<MediaStreamTrack | null>(null);

  const applyZoom = useCallback(async (level: number, video?: HTMLVideoElement | null) => {
    const v = video || (document.querySelector('#sr-barcode-scanner video') as HTMLVideoElement | null);
    if (v && v.srcObject) {
      if (trackRef.current && supportsZoom) {
        try { await trackRef.current.applyConstraints({ advanced: [{ zoom: level }] as any }); } catch { }
      }
      (v as HTMLElement).style.transform = `scale(${level})`;
    }
  }, [supportsZoom]);

  useEffect(() => {
    // StrictMode guard: skip second effect run
    if (initializedRef.current) return;
    initializedRef.current = true;

    const el = containerRef.current;
    if (!el) return;

    const id = 'sr-barcode-scanner';
    el.id = id;
    el.innerHTML = '';

    let cancelled = false;
    const s = new Html5Qrcode(id);
    scannerRef.current = s;

    const startWithFacing = async (facingMode: 'environment' | 'user') => {
      await s.start(
        { facingMode },
        { fps: 30 },
        (decodedText) => {
          if (cancelled) return;
          try { s.stop(); } catch { }
          onScan(decodedText);
        },
        () => {}
      );
      // Set up zoom after camera starts
      setTimeout(() => {
        if (cancelled) return;
        const video = el.querySelector('video');
        if (video && video.srcObject) {
          (video as HTMLElement).style.transition = 'transform 0.2s';
          (video as HTMLElement).style.transformOrigin = 'center center';
          const track = (video.srcObject as MediaStream).getVideoTracks()[0];
          if (track) {
            trackRef.current = track;
            const caps = track.getCapabilities() as any;
            if (caps?.zoom) { setSupportsZoom(true); setZoomMax(caps.zoom.max || 3); }
          }
        }
      }, 300);
    };

    startWithFacing('environment').catch(() => {
      return startWithFacing('user');
    }).catch((err: unknown) => {
      if (cancelled) return;
      const msg = err instanceof Error ? err.message : String(err);
      const isIOS = navigator.userAgent.includes('iPhone') || navigator.userAgent.includes('iPad');
      if (msg.includes('NotAllowed') || msg.includes('Permission')) {
        setError(isIOS ? 'Camera denied. Settings → Safari → Camera → Allow.' : 'Camera permission denied.');
      } else if (msg.includes('NotFound')) {
        setError('No camera found on this device.');
      } else {
        setError(msg);
      }
    });

    return () => {
      cancelled = true;
      try { s.stop(); } catch { }
    };
  }, []);

  const handleZoomIn = () => {
    const newZoom = Math.min(zoom + 0.5, zoomMax);
    setZoom(newZoom);
    applyZoom(newZoom);
  };
  const handleZoomOut = () => {
    const newZoom = Math.max(zoom - 0.5, 0.5);
    setZoom(newZoom);
    applyZoom(newZoom);
  };

  return (
    <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/60 backdrop-blur-sm" onClick={onClose}>
      <div className="bg-white rounded-2xl shadow-xl overflow-hidden w-full max-w-sm mx-4" onClick={(e) => e.stopPropagation()}>
        <div className="flex items-center justify-between px-4 py-3 border-b border-slate-200">
          <div className="flex items-center gap-2">
            <Camera className="w-4 h-5 text-primary" />
            <span className="text-sm font-bold text-slate-900">Scan Barcode</span>
          </div>
          <button onClick={onClose} className="p-1 hover:bg-slate-100 rounded-lg transition-colors">
            <X className="w-5 h-5 text-slate-400" />
          </button>
        </div>

        {error ? (
          <div className="p-6 text-center space-y-4">
            <div className="w-12 h-12 mx-auto rounded-full bg-red-50 flex items-center justify-center">
              <AlertCircle className="w-6 h-6 text-red-500" />
            </div>
            <p className="text-sm text-slate-600">{error}</p>
            <button onClick={onClose} className="px-6 py-2.5 bg-primary text-white rounded-xl text-sm font-medium">Close</button>
          </div>
        ) : (
          <>
            <div className="relative w-full aspect-[4/3] overflow-hidden">
              <div ref={containerRef} className="absolute inset-0 bg-black" />
              <div className="absolute bottom-3 right-3 flex items-center gap-1 bg-black/60 rounded-full px-2 py-1.5 z-10">
                <button onClick={handleZoomOut} className="p-1 text-white/70 hover:text-white" type="button"><ZoomOut className="w-4 h-4" /></button>
                <span className="text-[10px] text-white font-mono min-w-[24px] text-center">{zoom.toFixed(1)}x</span>
                <button onClick={handleZoomIn} className="p-1 text-white/70 hover:text-white" type="button"><ZoomIn className="w-4 h-4" /></button>
              </div>
            </div>
            <p className="text-[11px] text-slate-500 text-center py-3 px-4">Position the barcode or QR code within the scanning area</p>
          </>
        )}
      </div>
    </div>
  );
}