import { useState, useCallback, useRef } from 'react';
import { FileItem, UploadStatus } from '../types';
import { uploadBatchToHub } from '../services/hfService';

export const useFileUpload = () => {
  const [files, setFiles] = useState<FileItem[]>([]);
  const [isUploading, setIsUploading] = useState(false);
  
  // Use Ref to access latest state inside async loops without dependencies issues
  const filesRef = useRef<FileItem[]>([]);
  filesRef.current = files;

  // --- CONFIGURATION FOR SPEED ---
  // Tăng số lượng file mỗi lần gửi để giảm thời gian tạo commit trên HF
  const BATCH_SIZE = 10; 
  // Số lượng request gửi song song (Browser thường giới hạn 6 domain connections)
  const CONCURRENCY_LIMIT = 5; 

  // --- UPLOAD LOGIC ---

  const addFiles = useCallback((newFilesList: FileItem[]) => {
    setFiles((prev) => [...prev, ...newFilesList]);
  }, []);

  const removeFile = useCallback((id: string) => {
    setFiles((prev) => prev.filter((f) => f.id !== id));
  }, []);

  const updateFilePath = useCallback((id: string, newPath: string) => {
    setFiles((prev) => prev.map((f) => (f.id === id ? { ...f, path: newPath } : f)));
  }, []);

  const startUpload = useCallback(async () => {
    // Filter pending files
    const pendingFiles = filesRef.current.filter(
      (f) => f.status === UploadStatus.IDLE || f.status === UploadStatus.ERROR
    );

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

    setIsUploading(true);

    // 1. Chunk files into Batches
    const batches: FileItem[][] = [];
    for (let i = 0; i < pendingFiles.length; i += BATCH_SIZE) {
      batches.push(pendingFiles.slice(i, i + BATCH_SIZE));
    }

    // A queue of batches to process
    const queue = [...batches];
    let activeWorkers = 0;

    // Helper to update status safely
    const updateBatchStatus = (batchItems: FileItem[], status: UploadStatus, result?: { urls?: string[], error?: string }) => {
      setFiles((prev) => 
        prev.map((f) => {
           const batchIndex = batchItems.findIndex(b => b.id === f.id);
           if (batchIndex !== -1) {
             return {
               ...f,
               status: status,
               url: status === UploadStatus.SUCCESS ? result?.urls?.[batchIndex] : f.url,
               error: status === UploadStatus.ERROR ? result?.error : undefined
             };
           }
           return f;
        })
      );
    };

    // 2. The Worker Function
    // Process one batch, then immediately grab the next one from the queue
    const processNextBatch = async (): Promise<void> => {
      if (queue.length === 0) return;

      const batch = queue.shift();
      if (!batch) return;

      activeWorkers++;
      
      // Update UI -> UPLOADING
      updateBatchStatus(batch, UploadStatus.UPLOADING);

      try {
        const payload = batch.map(item => ({
            id: item.id,
            file: item.file,
            path: item.path
        }));

        const urls = await uploadBatchToHub(payload);
        
        // Update UI -> SUCCESS
        updateBatchStatus(batch, UploadStatus.SUCCESS, { urls });

      } catch (err: any) {
        console.error("Batch failed:", err);
        // Update UI -> ERROR
        updateBatchStatus(batch, UploadStatus.ERROR, { error: err.message || "Upload failed" });
      } finally {
        activeWorkers--;
        // Recursively process next batch if available
        if (queue.length > 0) {
            await processNextBatch();
        }
      }
    };

    // 3. Start Initial Workers (Pool)
    // Create exactly CONCURRENCY_LIMIT workers that will keep eating from the queue
    const initialWorkers = [];
    const limit = Math.min(CONCURRENCY_LIMIT, batches.length);
    
    for (let i = 0; i < limit; i++) {
        initialWorkers.push(processNextBatch());
    }

    // Wait for all workers to finish depleting the queue
    await Promise.all(initialWorkers);
    
    setIsUploading(false);

  }, []); // Remove 'files' dependency to avoid closure staleness, use ref

  return {
    files,
    isUploading,
    addFiles,
    removeFile,
    updateFilePath,
    startUpload
  };
};