import { useCallback, useRef, useState, type DragEvent } from 'react';

import { getDndApi } from '../shared/dndApi';

const AUDIO_EXTENSIONS = new Set(['.mp3', '.wav', '.ogg', '.m4a', '.aac']);
const PREVIEW_EXTENSIONS = new Set([
  '.png',
  '.jpg',
  '.jpeg',
  '.webp',
  '.gif',
  '.bmp',
  '.mp4',
  '.webm',
  '.mov',
]);

function fileExtension(filePath: string): string {
  const dot = filePath.lastIndexOf('.');
  return dot >= 0 ? filePath.slice(dot).toLowerCase() : '';
}

export function getDroppedFilePaths(e: DragEvent): string[] {
  const files = e.dataTransfer?.files;
  if (!files?.length) return [];
  const getPathForFile = getDndApi().getPathForFile;
  return Array.from(files)
    .map((file) => getPathForFile(file))
    .filter((path) => path.length > 0);
}

export function filterAudioFilePaths(paths: string[]): string[] {
  return paths.filter((path) => AUDIO_EXTENSIONS.has(fileExtension(path)));
}

export function pickFirstPreviewFilePath(paths: string[]): string | null {
  for (const path of paths) {
    if (PREVIEW_EXTENSIONS.has(fileExtension(path))) return path;
  }
  return null;
}

function dragHasFiles(e: DragEvent): boolean {
  return Array.from(e.dataTransfer?.types ?? []).includes('Files');
}

type UseFileDropZoneOptions = {
  disabled?: boolean;
  onDropPaths: (paths: string[]) => void;
  filterPaths?: (paths: string[]) => string[];
};

export function useFileDropZone({
  disabled = false,
  onDropPaths,
  filterPaths,
}: UseFileDropZoneOptions) {
  const [dragOver, setDragOver] = useState(false);
  const depthRef = useRef(0);

  const onDragEnter = useCallback(
    (e: DragEvent) => {
      if (disabled || !dragHasFiles(e)) return;
      e.preventDefault();
      e.stopPropagation();
      depthRef.current += 1;
      setDragOver(true);
    },
    [disabled],
  );

  const onDragLeave = useCallback(
    (e: DragEvent) => {
      if (disabled) return;
      e.preventDefault();
      e.stopPropagation();
      depthRef.current = Math.max(0, depthRef.current - 1);
      if (depthRef.current === 0) setDragOver(false);
    },
    [disabled],
  );

  const onDragOver = useCallback(
    (e: DragEvent) => {
      if (disabled || !dragHasFiles(e)) return;
      e.preventDefault();
      e.stopPropagation();
      e.dataTransfer.dropEffect = 'copy';
    },
    [disabled],
  );

  const onDrop = useCallback(
    (e: DragEvent) => {
      if (disabled || !dragHasFiles(e)) return;
      e.preventDefault();
      e.stopPropagation();
      depthRef.current = 0;
      setDragOver(false);
      const raw = getDroppedFilePaths(e);
      const paths = filterPaths ? filterPaths(raw) : raw;
      if (paths.length === 0) return;
      onDropPaths(paths);
    },
    [disabled, filterPaths, onDropPaths],
  );

  return { dragOver, onDragEnter, onDragLeave, onDragOver, onDrop };
}