import { useCallback, useState } from 'react';
import { loadPdfFromFile } from '../pdf/pdfService';
import {
  canMergeQueue,
  createMergeQueueItemId,
  getReadyMergeQueuePdfs,
  hasMergeQueueErrors,
  isMergeQueueLoading,
  moveMergeQueueItem,
} from './mergeQueueHelpers';
import type { MergeQueueItem } from './mergeTypes';

export function useMergeQueue() {
  const [items, setItems] = useState<MergeQueueItem[]>([]);

  const addFiles = useCallback((files: File[]) => {
    const pdfFiles = files.filter(
      (file) =>
        file.type === 'application/pdf' ||
        file.name.toLowerCase().endsWith('.pdf')
    );

    if (pdfFiles.length === 0) return;

    const queuedItems: MergeQueueItem[] = pdfFiles.map((file) => ({
      id: createMergeQueueItemId(),
      file,
      name: file.name,
      size: file.size,
      pageCount: null,
      pdf: null,
      status: 'loading',
    }));

    setItems((current) => [...current, ...queuedItems]);

    queuedItems.forEach((item) => {
      void (async () => {
        try {
          const loadedPdf = await loadPdfFromFile(item.file);

          setItems((current) =>
            current.map((currentItem) =>
              currentItem.id === item.id
                ? {
                    ...currentItem,
                    pdf: loadedPdf,
                    pageCount: loadedPdf.pageCount,
                    status: 'ready',
                    error: undefined,
                  }
                : currentItem
            )
          );
        } catch (error) {
          console.error(error);

          setItems((current) =>
            current.map((currentItem) =>
              currentItem.id === item.id
                ? {
                    ...currentItem,
                    status: 'error',
                    error: 'Could not load this PDF.',
                  }
                : currentItem
            )
          );
        }
      })();
    });
  }, []);

  const removeItem = useCallback((itemId: string) => {
    setItems((current) => current.filter((item) => item.id !== itemId));
  }, []);

  const moveItemUp = useCallback((itemId: string) => {
    setItems((current) => moveMergeQueueItem(current, itemId, 'up'));
  }, []);

  const moveItemDown = useCallback((itemId: string) => {
    setItems((current) => moveMergeQueueItem(current, itemId, 'down'));
  }, []);

  const clearQueue = useCallback(() => {
    setItems([]);
  }, []);

  return {
    items,
    addFiles,
    removeItem,
    moveItemUp,
    moveItemDown,
    clearQueue,
    readyPdfs: getReadyMergeQueuePdfs(items),
    canMerge: canMergeQueue(items),
    hasErrors: hasMergeQueueErrors(items),
    isLoading: isMergeQueueLoading(items),
  };
}