import React, { useCallback, useState } from 'react';
import { useDropzone } from 'react-dropzone';
import { motion, AnimatePresence } from 'framer-motion';
import { 
  CloudArrowUpIcon, 
  DocumentIcon, 
  CheckCircleIcon,
  XCircleIcon,
  XMarkIcon 
} from '@heroicons/react/24/outline';
import { uploadDocument } from '../services/api';
import toast from 'react-hot-toast';

const FileUploader = ({ darkMode, onClose }) => {
  const [uploading, setUploading] = useState(false);
  const [uploadedFiles, setUploadedFiles] = useState([]);

  const onDrop = useCallback(async (acceptedFiles) => {
    setUploading(true);
    
    for (const file of acceptedFiles) {
      try {
        console.log(`Starting upload for file: ${file.name}, size: ${file.size} bytes`);
        
        const formData = new FormData();
        formData.append('file', file);
        
        // Check file size limits
        const maxSize = 100 * 1024 * 1024; // 100MB
        if (file.size > maxSize) {
          toast.error(`${file.name} is too large (${formatFileSize(file.size)}). Maximum size is 100MB.`);
          setUploadedFiles(prev => [...prev, {
            name: file.name,
            size: file.size,
            status: 'error',
            error: 'File too large (max 100MB)'
          }]);
          continue; // Skip this file
        } else if (file.size > 10 * 1024 * 1024) {
          toast(`Warning: ${file.name} is large (${formatFileSize(file.size)}). Upload may take time.`, {
            icon: '⚠️',
            duration: 6000
          });
        }
        
        await uploadDocument(formData);
        
        setUploadedFiles(prev => [...prev, {
          name: file.name,
          size: file.size,
          status: 'success'
        }]);
        
        toast.success(`${file.name} uploaded successfully!`);
        console.log(`Successfully uploaded: ${file.name}`);
        
      } catch (error) {
        console.error(`Failed to upload ${file.name}:`, error);
        
        setUploadedFiles(prev => [...prev, {
          name: file.name,
          size: file.size,
          status: 'error',
          error: error.message
        }]);
        
        // More specific error messages
        let errorMessage = `Failed to upload ${file.name}`;
        if (error.message.includes('Network Error')) {
          errorMessage += ': Network connection failed. Check if the server is running.';
        } else if (error.message.includes('timeout')) {
          errorMessage += ': Upload timed out. File may be too large.';
        } else if (error.message.includes('413')) {
          errorMessage += ': File too large (max 100MB allowed).';
        } else if (error.message.includes('415')) {
          errorMessage += ': Unsupported file type.';
        } else if (error.message.includes('500')) {
          errorMessage += ': Server error. Check server logs.';
        } else {
          errorMessage += `: ${error.message}`;
        }
        
        toast.error(errorMessage);
      }
    }
    
    setUploading(false);
  }, []);

  const { getRootProps, getInputProps, isDragActive } = useDropzone({
    onDrop,
    accept: {
      'application/pdf': ['.pdf'],
      'application/vnd.openxmlformats-officedocument.wordprocessingml.document': ['.docx'],
      'text/plain': ['.txt']
    },
    multiple: true
  });

  const formatFileSize = (bytes) => {
    if (bytes === 0) return '0 Bytes';
    const k = 1024;
    const sizes = ['Bytes', 'KB', 'MB', 'GB'];
    const i = Math.floor(Math.log(bytes) / Math.log(k));
    return parseFloat((bytes / Math.pow(k, i)).toFixed(2)) + ' ' + sizes[i];
  };

  const removeFile = (index) => {
    setUploadedFiles(prev => prev.filter((_, i) => i !== index));
  };

  return (
    <div className="space-y-4">
      {/* Dropzone */}
      <motion.div
        {...getRootProps()}
        whileHover={{ scale: 1.02 }}
        whileTap={{ scale: 0.98 }}
        className={`file-drop-zone border-2 border-dashed rounded-2xl p-8 text-center cursor-pointer transition-all ${
          isDragActive
            ? darkMode
              ? 'border-primary-400 bg-primary-900/20'
              : 'border-primary-500 bg-primary-50'
            : darkMode
              ? 'border-gray-600 hover:border-gray-500 bg-gray-800'
              : 'border-gray-300 hover:border-gray-400 bg-gray-50'
        }`}
      >
        <input {...getInputProps()} />
        
        <CloudArrowUpIcon className={`w-12 h-12 mx-auto mb-4 ${
          isDragActive
            ? darkMode ? 'text-primary-400' : 'text-primary-500'
            : darkMode ? 'text-gray-400' : 'text-gray-500'
        }`} />
        
        <h3 className={`text-lg font-semibold mb-2 ${
          darkMode ? 'text-white' : 'text-gray-900'
        }`}>
          {isDragActive ? 'Drop files here' : 'Upload study materials'}
        </h3>
        
        <p className={`mb-4 ${
          darkMode ? 'text-gray-400' : 'text-gray-600'
        }`}>
          Drag & drop files here, or click to browse
        </p>
        
        <p className={`text-xs mb-4 ${
          darkMode ? 'text-gray-500' : 'text-gray-500'
        }`}>
          Maximum file size: 100MB
        </p>
        
        <div className="flex justify-center space-x-2">
          <span className={`px-3 py-1 rounded-full text-xs font-medium ${
            darkMode 
              ? 'bg-blue-900/30 text-blue-400' 
              : 'bg-blue-100 text-blue-700'
          }`}>
            PDF
          </span>
          <span className={`px-3 py-1 rounded-full text-xs font-medium ${
            darkMode 
              ? 'bg-green-900/30 text-green-400' 
              : 'bg-green-100 text-green-700'
          }`}>
            DOCX
          </span>
          <span className={`px-3 py-1 rounded-full text-xs font-medium ${
            darkMode 
              ? 'bg-purple-900/30 text-purple-400' 
              : 'bg-purple-100 text-purple-700'
          }`}>
            TXT
          </span>
        </div>
      </motion.div>

      {/* Upload Progress */}
      {uploading && (
        <motion.div
          initial={{ opacity: 0, y: 20 }}
          animate={{ opacity: 1, y: 0 }}
          className={`p-4 rounded-lg ${
            darkMode ? 'bg-gray-800' : 'bg-gray-100'
          }`}
        >
          <div className="flex items-center space-x-3">
            <div className="animate-spin rounded-full h-5 w-5 border-b-2 border-primary-500"></div>
            <span className={`${darkMode ? 'text-gray-300' : 'text-gray-700'}`}>
              Uploading files...
            </span>
          </div>
        </motion.div>
      )}

      {/* Uploaded Files List */}
      <AnimatePresence>
        {uploadedFiles.length > 0 && (
          <motion.div
            initial={{ opacity: 0, height: 0 }}
            animate={{ opacity: 1, height: 'auto' }}
            exit={{ opacity: 0, height: 0 }}
            className="space-y-2"
          >
            <h4 className={`font-medium ${
              darkMode ? 'text-gray-300' : 'text-gray-700'
            }`}>
              Uploaded Files
            </h4>
            
            {uploadedFiles.map((file, index) => (
              <motion.div
                key={index}
                initial={{ opacity: 0, x: -20 }}
                animate={{ opacity: 1, x: 0 }}
                className={`flex items-center justify-between p-3 rounded-lg ${
                  darkMode ? 'bg-gray-800' : 'bg-gray-100'
                }`}
              >
                <div className="flex items-center space-x-3">
                  <DocumentIcon className={`w-5 h-5 ${
                    darkMode ? 'text-gray-400' : 'text-gray-500'
                  }`} />
                  
                  <div>
                    <p className={`text-sm font-medium ${
                      darkMode ? 'text-white' : 'text-gray-900'
                    }`}>
                      {file.name}
                    </p>
                    <p className={`text-xs ${
                      darkMode ? 'text-gray-500' : 'text-gray-400'
                    }`}>
                      {formatFileSize(file.size)}
                    </p>
                  </div>
                </div>
                
                <div className="flex items-center space-x-2">
                  {file.status === 'success' ? (
                    <CheckCircleIcon className="w-5 h-5 text-green-500" />
                  ) : (
                    <XCircleIcon className="w-5 h-5 text-red-500" />
                  )}
                  
                  <button
                    onClick={() => removeFile(index)}
                    className={`p-1 rounded transition-colors ${
                      darkMode
                        ? 'hover:bg-gray-700 text-gray-400'
                        : 'hover:bg-gray-200 text-gray-500'
                    }`}
                  >
                    <XMarkIcon className="w-4 h-4" />
                  </button>
                </div>
              </motion.div>
            ))}
          </motion.div>
        )}
      </AnimatePresence>

      {/* Close Button */}
      {onClose && (
        <div className="flex justify-end">
          <button
            onClick={onClose}
            className={`px-4 py-2 rounded-lg font-medium transition-colors ${
              darkMode
                ? 'bg-gray-700 hover:bg-gray-600 text-white'
                : 'bg-gray-200 hover:bg-gray-300 text-gray-700'
            }`}
          >
            Close
          </button>
        </div>
      )}
    </div>
  );
};

export default FileUploader;