import React, { useRef, useState, useEffect } from 'react';
import { Eraser, Check } from 'lucide-react';

interface SignatureCaptureProps {
  onSignatureComplete: (signatureDataUrl: string) => void;
  width?: number;
  height?: number;
  initialSignature?: string | null;
}

export const SignatureCapture: React.FC<SignatureCaptureProps> = ({ 
  onSignatureComplete, 
  width = 600, 
  height = 200,
  initialSignature = null
}) => {
  const canvasRef = useRef<HTMLCanvasElement>(null);
  const [isDrawing, setIsDrawing] = useState(false);
  const [hasSignature, setHasSignature] = useState(false);

  // Initialize canvas context
  useEffect(() => {
    const canvas = canvasRef.current;
    if (!canvas) return;

    const ctx = canvas.getContext('2d');
    if (!ctx) return;

    // Detect theme for stroke color (visible on black/dark or white screens)
    const isDark = document.documentElement.classList.contains('dark');
    ctx.strokeStyle = isDark ? '#fafafa' : '#09090b';
    ctx.lineWidth = 3;
    ctx.lineCap = 'round';
    ctx.lineJoin = 'round';

    // Handle high DPI displays for crisp rendering
    const dpr = window.devicePixelRatio || 1;
    canvas.width = width * dpr;
    canvas.height = height * dpr;
    canvas.style.width = `${width}px`;
    canvas.style.height = `${height}px`;
    ctx.scale(dpr, dpr);

    if (initialSignature) {
      const img = new Image();
      img.onload = () => {
        ctx.drawImage(img, 0, 0, width, height);
      };
      img.src = initialSignature;
      setHasSignature(true);
    } else {
      ctx.clearRect(0, 0, canvas.width, canvas.height);
      setHasSignature(false);
    }
  }, [width, height, initialSignature]);

  // Adjust stroke color if theme toggles during active view
  useEffect(() => {
    const canvas = canvasRef.current;
    if (!canvas) return;
    const ctx = canvas.getContext('2d');
    if (!ctx) return;
    
    const isDark = document.documentElement.classList.contains('dark');
    ctx.strokeStyle = isDark ? '#fafafa' : '#09090b';
  });

  const startDrawing = (e: React.MouseEvent<HTMLCanvasElement> | React.TouchEvent<HTMLCanvasElement>) => {
    e.preventDefault();
    const canvas = canvasRef.current;
    if (!canvas) return;

    const ctx = canvas.getContext('2d');
    if (!ctx) return;

    const rect = canvas.getBoundingClientRect();
    let clientX, clientY;

    if ('touches' in e) {
      clientX = e.touches[0].clientX;
      clientY = e.touches[0].clientY;
    } else {
      clientX = (e as React.MouseEvent).clientX;
      clientY = (e as React.MouseEvent).clientY;
    }

    ctx.beginPath();
    ctx.moveTo(clientX - rect.left, clientY - rect.top);
    setIsDrawing(true);
  };

  const draw = (e: React.MouseEvent<HTMLCanvasElement> | React.TouchEvent<HTMLCanvasElement>) => {
    e.preventDefault();
    if (!isDrawing) return;

    const canvas = canvasRef.current;
    if (!canvas) return;

    const ctx = canvas.getContext('2d');
    if (!ctx) return;

    const rect = canvas.getBoundingClientRect();
    let clientX, clientY;

    if ('touches' in e) {
      clientX = e.touches[0].clientX;
      clientY = e.touches[0].clientY;
    } else {
      clientX = (e as React.MouseEvent).clientX;
      clientY = (e as React.MouseEvent).clientY;
    }

    ctx.lineTo(clientX - rect.left, clientY - rect.top);
    ctx.stroke();
    setHasSignature(true);
  };

  const stopDrawing = () => {
    setIsDrawing(false);
  };

  const clearSignature = () => {
    const canvas = canvasRef.current;
    if (!canvas) return;

    const ctx = canvas.getContext('2d');
    if (!ctx) return;

    ctx.clearRect(0, 0, canvas.width, canvas.height);
    setHasSignature(false);
    onSignatureComplete('');
  };

  const handleSave = () => {
    const canvas = canvasRef.current;
    if (!canvas || !hasSignature) return;

    const dataUrl = canvas.toDataURL('image/png');
    onSignatureComplete(dataUrl);
  };

  return (
    <div className="flex flex-col w-full max-w-2xl mx-auto">
      <div className="relative rounded-2xl bg-ink-50 border-2 border-dashed border-ink-200 overflow-hidden shadow-inner group">
        
        {/* Helper Text */}
        {!hasSignature && (
          <div className="absolute inset-0 flex items-center justify-center pointer-events-none">
            <p className="text-ink-400 font-medium text-sm">
              Draw your signature here
            </p>
          </div>
        )}

        <canvas
          ref={canvasRef}
          onMouseDown={startDrawing}
          onMouseMove={draw}
          onMouseUp={stopDrawing}
          onMouseOut={stopDrawing}
          onTouchStart={startDrawing}
          onTouchMove={draw}
          onTouchEnd={stopDrawing}
          className="touch-none cursor-crosshair relative z-10 w-full"
          style={{ width: '100%', height: `${height}px`, maxWidth: `${width}px` }}
        />
      </div>

      <div className="flex items-center justify-between mt-4">
        <button
          type="button"
          onClick={clearSignature}
          disabled={!hasSignature}
          className="flex items-center gap-2 px-4 py-2 text-sm font-semibold text-ink-500 hover:text-red-600 hover:bg-red-500/10 rounded-xl transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
        >
          <Eraser className="w-4 h-4" />
          Clear
        </button>

        <button
          type="button"
          onClick={handleSave}
          disabled={!hasSignature}
          className="flex items-center gap-2 px-6 py-2.5 text-sm font-bold text-ink-0 bg-ink-900 hover:bg-ink-800 rounded-xl transition-all shadow-md hover:shadow-lg disabled:opacity-50 disabled:cursor-not-allowed disabled:hover:shadow-md hover:-translate-y-0.5"
        >
          <Check className="w-4 h-4" />
          Accept & Sign
        </button>
      </div>
    </div>
  );
};
