import React, { useState, useCallback } from 'react';
import { Upload, File, X, AlertCircle } from 'lucide-react';
import { Button } from '@/components/ui/button';
import { Card, CardContent } from '@/components/ui/card';

const FileUpload = ({ onFileSelect, acceptedTypes = '.pdf,.png,.jpg,.jpeg,.tiff,.tif,.txt' }) => {
  const [dragActive, setDragActive] = useState(false);
  const [selectedFile, setSelectedFile] = useState(null);
  const [error, setError] = useState('');

  const handleDrag = useCallback((e) => {
    e.preventDefault();
    e.stopPropagation();
    if (e.type === 'dragenter' || e.type === 'dragover') {
      setDragActive(true);
    } else if (e.type === 'dragleave') {
      setDragActive(false);
    }
  }, []);

  const handleDrop = useCallback((e) => {
    e.preventDefault();
    e.stopPropagation();
    setDragActive(false);
    
    if (e.dataTransfer.files && e.dataTransfer.files[0]) {
      handleFileSelection(e.dataTransfer.files[0]);
    }
  }, []);

  const handleFileSelection = (file) => {
    setError('');
    
    // Check file size (50MB limit)
    if (file.size > 50 * 1024 * 1024) {
      setError('File size must be less than 50MB');
      return;
    }

    // Check file type
    const allowedTypes = acceptedTypes.split(',').map(type => type.trim().toLowerCase());
    const fileExtension = '.' + file.name.split('.').pop().toLowerCase();
    
    if (!allowedTypes.includes(fileExtension)) {
      setError(`File type not supported. Allowed types: ${acceptedTypes}`);
      return;
    }

    setSelectedFile(file);
    onFileSelect(file);
  };

  const handleFileInput = (e) => {
    if (e.target.files && e.target.files[0]) {
      handleFileSelection(e.target.files[0]);
    }
  };

  const removeFile = () => {
    setSelectedFile(null);
    setError('');
    onFileSelect(null);
  };

  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];
  };

  return (
    <Card className="w-full">
      <CardContent className="p-6">
        <div className="space-y-4">
          {!selectedFile ? (
            <div
              className={`relative border-2 border-dashed rounded-lg p-8 text-center transition-colors ${
                dragActive
                  ? 'border-blue-500 bg-blue-50'
                  : 'border-gray-300 hover:border-gray-400'
              }`}
              onDragEnter={handleDrag}
              onDragLeave={handleDrag}
              onDragOver={handleDrag}
              onDrop={handleDrop}
            >
              <input
                type="file"
                accept={acceptedTypes}
                onChange={handleFileInput}
                className="absolute inset-0 w-full h-full opacity-0 cursor-pointer"
              />
              
              <div className="space-y-4">
                <Upload className="mx-auto h-12 w-12 text-gray-400" />
                <div>
                  <p className="text-lg font-medium text-gray-900">
                    Drop your file here, or{' '}
                    <span className="text-blue-600 hover:text-blue-500">browse</span>
                  </p>
                  <p className="text-sm text-gray-500 mt-2">
                    Supports: PDF, PNG, JPG, TIFF, TXT (max 50MB)
                  </p>
                </div>
              </div>
            </div>
          ) : (
            <div className="flex items-center justify-between p-4 bg-gray-50 rounded-lg">
              <div className="flex items-center space-x-3">
                <File className="h-8 w-8 text-blue-600" />
                <div>
                  <p className="font-medium text-gray-900">{selectedFile.name}</p>
                  <p className="text-sm text-gray-500">{formatFileSize(selectedFile.size)}</p>
                </div>
              </div>
              <Button
                variant="ghost"
                size="sm"
                onClick={removeFile}
                className="text-gray-500 hover:text-red-600"
              >
                <X className="h-4 w-4" />
              </Button>
            </div>
          )}

          {error && (
            <div className="flex items-center space-x-2 text-red-600 bg-red-50 p-3 rounded-lg">
              <AlertCircle className="h-4 w-4" />
              <span className="text-sm">{error}</span>
            </div>
          )}
        </div>
      </CardContent>
    </Card>
  );
};

export default FileUpload;