import { useEffect, useRef, useState } from "react";
import { Eraser } from "lucide-react";

import { Button } from "@edr/ui-common";
import { cn } from "@/lib/utils";

interface ContractSignaturePadProps {
  onChange: (dataUrl: string | null) => void;
  className?: string;
}

export function ContractSignaturePad({
  onChange,
  className,
}: ContractSignaturePadProps) {
  const canvasRef = useRef<HTMLCanvasElement>(null);
  const drawing = useRef(false);
  const [empty, setEmpty] = useState(true);

  useEffect(() => {
    const canvas = canvasRef.current;
    if (!canvas) return;
    const ctx = canvas.getContext("2d");
    if (!ctx) return;
    const dpr = window.devicePixelRatio || 1;
    const w = canvas.offsetWidth;
    const h = canvas.offsetHeight;
    canvas.width = w * dpr;
    canvas.height = h * dpr;
    ctx.scale(dpr, dpr);
    ctx.strokeStyle = "#111";
    ctx.lineWidth = 2;
    ctx.lineCap = "round";
  }, []);

  const getPos = (e: React.MouseEvent | React.TouchEvent) => {
    const canvas = canvasRef.current!;
    const rect = canvas.getBoundingClientRect();
    if ("touches" in e) {
      const t = e.touches[0];
      return { x: t.clientX - rect.left, y: t.clientY - rect.top };
    }
    return { x: e.clientX - rect.left, y: e.clientY - rect.top };
  };

  const start = (e: React.MouseEvent | React.TouchEvent) => {
    drawing.current = true;
    const ctx = canvasRef.current?.getContext("2d");
    const { x, y } = getPos(e);
    ctx?.beginPath();
    ctx?.moveTo(x, y);
  };

  const move = (e: React.MouseEvent | React.TouchEvent) => {
    if (!drawing.current) return;
    const ctx = canvasRef.current?.getContext("2d");
    const { x, y } = getPos(e);
    ctx?.lineTo(x, y);
    ctx?.stroke();
    setEmpty(false);
    onChange(canvasRef.current?.toDataURL("image/png") ?? null);
  };

  const end = () => {
    drawing.current = false;
  };

  const clear = () => {
    const canvas = canvasRef.current;
    if (!canvas) return;
    const ctx = canvas.getContext("2d");
    if (!ctx) return;
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    setEmpty(true);
    onChange(null);
  };

  return (
    <div className={cn("space-y-2", className)}>
      <div className="overflow-hidden rounded-lg border-2 border-dashed border-border bg-white">
        <canvas
          ref={canvasRef}
          className="h-36 w-full touch-none cursor-crosshair"
          onMouseDown={start}
          onMouseMove={move}
          onMouseUp={end}
          onMouseLeave={end}
          onTouchStart={start}
          onTouchMove={move}
          onTouchEnd={end}
        />
      </div>
      <div className="flex items-center justify-between">
        <p className="text-xs text-muted-foreground">
          Draw your signature above
        </p>
        <Button type="button" variant="ghost" size="sm" className="gap-1" onClick={clear}>
          <Eraser className="size-3.5" />
          Clear
        </Button>
      </div>
      {empty && (
        <p className="text-xs text-amber-700">Signature is required before confirming.</p>
      )}
    </div>
  );
}