import React, { useCallback, useState } from 'react';
import { useDropzone } from 'react-dropzone';
import { 
  Box, 
  Paper, 
  Typography, 
  CircularProgress, 
  Alert,
  Button
} from '@mui/material';
import CloudUploadIcon from '@mui/icons-material/CloudUpload';
import axios from 'axios';

const FileUpload = ({ onUploadSuccess, onProcessingStart, onProcessingEnd }) => {
  const [uploading, setUploading] = useState(false);
  const [error, setError] = useState(null);
  const [success, setSuccess] = useState(false);

  const onDrop = useCallback(async (acceptedFiles) => {
    if (acceptedFiles.length === 0) return;
    
    const file = acceptedFiles[0];
    
    // Check file type
    if (!file.name.toLowerCase().endsWith('.txt') && !file.name.toLowerCase().endsWith('.pdf')) {
      setError('Only .txt and .pdf files are allowed');
      return;
    }
    
    // Check file size (2MB limit)
    if (file.size > 2 * 1024 * 1024) {
      setError('File size exceeds 2MB limit');
      return;
    }
    
    setUploading(true);
    setError(null);
    setSuccess(false);
    onProcessingStart();
    
    const formData = new FormData();
    formData.append('file', file);
    
    try {
      const response = await axios.post('http://localhost:8000/upload', formData, {
        headers: {
          'Content-Type': 'multipart/form-data',
        },
      });
      
      setSuccess(true);
      onUploadSuccess(file.name);
    } catch (err) {
      console.error('Upload error:', err);
      setError(err.response?.data?.detail || 'Error uploading file. Please try again.');
    } finally {
      setUploading(false);
      onProcessingEnd();
    }
  }, [onUploadSuccess, onProcessingStart, onProcessingEnd]);

  const { getRootProps, getInputProps, isDragActive } = useDropzone({
    onDrop,
    accept: {
      'text/plain': ['.txt'],
      'application/pdf': ['.pdf'],
    },
    maxSize: 2 * 1024 * 1024, // 2MB
    multiple: false,
  });

  return (
    <Paper 
      elevation={2} 
      sx={{ 
        p: 3, 
        mb: 4,
        border: '2px dashed',
        borderColor: isDragActive ? 'primary.main' : 'grey.300',
        backgroundColor: isDragActive ? 'action.hover' : 'background.paper',
        transition: 'all 0.2s ease',
      }}
    >
      <Box
        {...getRootProps()}
        sx={{
          display: 'flex',
          flexDirection: 'column',
          alignItems: 'center',
          justifyContent: 'center',
          cursor: 'pointer',
          minHeight: '200px',
        }}
      >
        <input {...getInputProps()} />
        
        {uploading ? (
          <Box sx={{ display: 'flex', flexDirection: 'column', alignItems: 'center' }}>
            <CircularProgress size={60} sx={{ mb: 2 }} />
            <Typography variant="body1">Processing your file...</Typography>
          </Box>
        ) : (
          <>
            <CloudUploadIcon sx={{ fontSize: 60, color: 'primary.main', mb: 2 }} />
            <Typography variant="h6" gutterBottom>
              {isDragActive ? 'Drop the file here' : 'Drag & drop a file here, or click to select'}
            </Typography>
            <Typography variant="body2" color="text.secondary" align="center" sx={{ mb: 2 }}>
              Supported formats: .txt, .pdf (max 2MB)
            </Typography>
            <Button variant="contained" color="primary">
              Select File
            </Button>
          </>
        )}
      </Box>
      
      {error && (
        <Alert severity="error" sx={{ mt: 2 }}>
          {error}
        </Alert>
      )}
      
      {success && (
        <Alert severity="success" sx={{ mt: 2 }}>
          File uploaded successfully! You can now ask questions about the document.
        </Alert>
      )}
    </Paper>
  );
};

export default FileUpload;