import { useState, useRef } from 'react';
import { Camera, Upload, X, CheckCircle2, AlertCircle, Info } from 'lucide-react';
import { Html5Qrcode } from 'html5-qrcode';

interface QRScannerProps {
    onScanSuccess: (scannedText: string) => void;
    onClose: () => void;
}

export default function QRScanner({ onScanSuccess, onClose }: QRScannerProps) {
    const [scanMode, setScanMode] = useState<'camera' | 'file' | null>(null);
    const [scanning, setScanning] = useState(false);
    const [error, setError] = useState<string>('');
    const [success, setSuccess] = useState(false);
    const html5QrCodeRef = useRef<Html5Qrcode | null>(null);
    const fileInputRef = useRef<HTMLInputElement>(null);

    const startCamera = async () => {
        setError('');
        setScanMode('camera');
        setScanning(true);

        // Wait for DOM to render the #qr-reader div
        await new Promise(resolve => setTimeout(resolve, 100));

        try {
            // Check if we're on HTTPS or localhost
            if (window.location.protocol !== 'https:' && !window.location.hostname.includes('localhost')) {
                throw new Error('Camera requires HTTPS or localhost. Use: bun run dev');
            }

            const html5QrCode = new Html5Qrcode('qr-reader');
            html5QrCodeRef.current = html5QrCode;

            await html5QrCode.start(
                { facingMode: 'environment' },
                {
                    fps: 10,
                    qrbox: { width: 250, height: 250 },
                    aspectRatio: 1.0,
                },
                (decodedText) => {
                    if (decodedText.startsWith('SEEDPGP1:')) {
                        setSuccess(true);
                        onScanSuccess(decodedText);
                        stopCamera();
                    } else {
                        setError('QR code found, but not a valid SEEDPGP1 frame');
                    }
                },
                () => {
                    // Ignore frequent scanning errors
                }
            );
        } catch (err: any) {
            console.error('Camera error:', err);
            setError(`Camera failed: ${err.message || 'Permission denied or not available'}`);
            setScanning(false);
            setScanMode(null);
        }
    };


    const stopCamera = async () => {
        if (html5QrCodeRef.current) {
            try {
                await html5QrCodeRef.current.stop();
                html5QrCodeRef.current.clear();
            } catch (err) {
                console.error('Error stopping camera:', err);
            }
            html5QrCodeRef.current = null;
        }
        setScanning(false);
        setScanMode(null);
    };

    const handleFileUpload = async (e: React.ChangeEvent<HTMLInputElement>) => {
        const file = e.target.files?.[0];
        if (!file) return;

        setError('');
        setScanMode('file');
        setScanning(true);

        try {
            const html5QrCode = new Html5Qrcode('qr-reader-file');

            // Try scanning with verbose mode
            const decodedText = await html5QrCode.scanFile(file, true);

            if (decodedText.startsWith('SEEDPGP1:')) {
                setSuccess(true);
                onScanSuccess(decodedText);
                html5QrCode.clear();
            } else {
                setError(`Found QR code, but not SEEDPGP format: ${decodedText.substring(0, 30)}...`);
            }
        } catch (err: any) {
            console.error('File scan error:', err);

            // Provide helpful error messages
            if (err.message?.includes('No MultiFormat')) {
                setError('Could not detect QR code in image. Try: 1) Taking a clearer photo, 2) Ensuring good lighting, 3) Screenshot from the Backup tab');
            } else {
                setError(`Scan failed: ${err.message || 'Unknown error'}`);
            }
        } finally {
            setScanning(false);
            // Reset file input so same file can be selected again
            if (fileInputRef.current) {
                fileInputRef.current.value = '';
            }
        }
    };

    const handleClose = async () => {
        await stopCamera();
        onClose();
    };

    return (
        <div className="fixed inset-0 bg-black/60 backdrop-blur-sm z-50 flex items-center justify-center p-4 animate-in fade-in">
            <div className="bg-white rounded-2xl shadow-2xl max-w-md w-full overflow-hidden animate-in zoom-in-95">
                {/* Header */}
                <div className="bg-gradient-to-r from-slate-900 to-slate-800 p-4 text-white flex items-center justify-between">
                    <div className="flex items-center gap-2">
                        <Camera size={20} />
                        <h2 className="font-bold text-lg">Scan QR Code</h2>
                    </div>
                    <button
                        onClick={handleClose}
                        className="p-1.5 hover:bg-white/20 rounded-lg transition-colors"
                    >
                        <X size={20} />
                    </button>
                </div>

                {/* Content */}
                <div className="p-6 space-y-4">
                    {/* Error Display */}
                    {error && (
                        <div className="p-3 bg-red-50 border-l-4 border-red-500 rounded-r-lg flex gap-2 text-red-800 text-xs leading-relaxed">
                            <AlertCircle size={16} className="shrink-0 mt-0.5" />
                            <p>{error}</p>
                        </div>
                    )}

                    {/* Success Display */}
                    {success && (
                        <div className="p-3 bg-green-50 border-l-4 border-green-500 rounded-r-lg flex gap-2 text-green-800 text-sm">
                            <CheckCircle2 size={16} className="shrink-0 mt-0.5" />
                            <p>QR code scanned successfully!</p>
                        </div>
                    )}

                    {/* Mode Selection */}
                    {!scanMode && (
                        <div className="space-y-3">
                            <button
                                onClick={startCamera}
                                className="w-full py-4 bg-gradient-to-r from-blue-600 to-blue-700 text-white rounded-xl font-semibold flex items-center justify-center gap-2 hover:from-blue-700 hover:to-blue-800 transition-all shadow-lg"
                            >
                                <Camera size={20} />
                                Use Camera
                            </button>

                            <button
                                onClick={() => fileInputRef.current?.click()}
                                className="w-full py-4 bg-gradient-to-r from-slate-700 to-slate-800 text-white rounded-xl font-semibold flex items-center justify-center gap-2 hover:from-slate-800 hover:to-slate-900 transition-all shadow-lg"
                            >
                                <Upload size={20} />
                                Upload Image
                            </button>

                            <input
                                ref={fileInputRef}
                                type="file"
                                accept="image/*"
                                onChange={handleFileUpload}
                                className="hidden"
                            />

                            {/* Info Box */}
                            <div className="pt-4 border-t border-slate-200">
                                <div className="flex gap-2 text-xs text-slate-600 leading-relaxed">
                                    <Info size={14} className="shrink-0 mt-0.5 text-blue-600" />
                                    <div>
                                        <p><strong>Camera:</strong> Requires HTTPS or localhost</p>
                                        <p className="mt-1"><strong>Upload:</strong> Screenshot QR from Backup tab for testing</p>
                                    </div>
                                </div>
                            </div>
                        </div>
                    )}

                    {/* Camera View */}
                    {scanMode === 'camera' && scanning && (
                        <div className="space-y-3">
                            <div id="qr-reader" className="rounded-lg overflow-hidden border-2 border-slate-200"></div>
                            <button
                                onClick={stopCamera}
                                className="w-full py-3 bg-red-600 text-white rounded-lg font-semibold hover:bg-red-700 transition-colors"
                            >
                                Stop Camera
                            </button>
                        </div>
                    )}

                    {/* File Processing View */}
                    {scanMode === 'file' && scanning && (
                        <div className="py-8 text-center">
                            <div className="inline-block animate-spin rounded-full h-8 w-8 border-4 border-slate-200 border-t-blue-600"></div>
                            <p className="mt-3 text-sm text-slate-600">Processing image...</p>
                        </div>
                    )}

                    {/* Hidden div for file scanning */}
                    <div id="qr-reader-file" className="hidden"></div>
                </div>
            </div>
        </div>
    );
}