import { useState, useRef, useCallback } from "react";

interface DropZoneProps {
  onFilesSelected: (files: File[]) => void;
  disabled?: boolean;
}

export default function DropZone({ onFilesSelected, disabled }: DropZoneProps) {
  const [isDragging, setIsDragging] = useState(false);
  const inputRef = useRef<HTMLInputElement>(null);
  const dragCounter = useRef(0);

  const handleDragEnter = useCallback((e: React.DragEvent) => {
    e.preventDefault();
    dragCounter.current++;
    if (e.dataTransfer.items.length > 0) {
      setIsDragging(true);
    }
  }, []);

  const handleDragLeave = useCallback((e: React.DragEvent) => {
    e.preventDefault();
    dragCounter.current--;
    if (dragCounter.current === 0) {
      setIsDragging(false);
    }
  }, []);

  const handleDragOver = useCallback((e: React.DragEvent) => {
    e.preventDefault();
  }, []);

  const handleDrop = useCallback(
    (e: React.DragEvent) => {
      e.preventDefault();
      setIsDragging(false);
      dragCounter.current = 0;
      if (disabled) return;

      const files = Array.from(e.dataTransfer.files);
      if (files.length > 0) {
        onFilesSelected(files);
      }
    },
    [onFilesSelected, disabled],
  );

  const handleClick = () => {
    if (!disabled) {
      inputRef.current?.click();
    }
  };

  const handleFileChange = (e: React.ChangeEvent<HTMLInputElement>) => {
    const files = Array.from(e.target.files || []);
    if (files.length > 0) {
      onFilesSelected(files);
    }
    e.target.value = "";
  };

  return (
    <div
      onDragEnter={handleDragEnter}
      onDragLeave={handleDragLeave}
      onDragOver={handleDragOver}
      onDrop={handleDrop}
      onClick={handleClick}
      className={`
        border border-dashed rounded-sm px-6 py-8
        flex flex-col items-center justify-center gap-2
        transition-colors duration-fast ease-crisp cursor-pointer
        ${isDragging
          ? "border-signal bg-signal-quiet"
          : disabled
            ? "border-paper-edge bg-paper-deep/40 cursor-not-allowed opacity-60"
            : "border-paper-edge bg-paper hover:border-ink hover:bg-paper-deep/40"
        }
      `}
    >
      <span className="font-mono text-[10px] uppercase tracking-[0.2em] text-ink-muted">
        {isDragging ? "Release" : "Drop"}
      </span>
      <p className="font-display text-xl text-ink">
        {disabled
          ? "Select a device first"
          : isDragging
            ? "Release to send"
            : "Drop files here"}
      </p>
      <p className="text-xs text-ink-muted">
        or click to choose
      </p>
      <input
        ref={inputRef}
        type="file"
        multiple
        className="hidden"
        onChange={handleFileChange}
      />
    </div>
  );
}