import React, { useRef, useState } from 'react';
import { Button } from './ui/button';
import { Upload, File, X, FileText, Presentation, CloudUpload } from 'lucide-react';
import { Card } from './ui/card';
import { Badge } from './ui/badge';
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from './ui/select';
import { Dialog, DialogContent, DialogDescription, DialogFooter, DialogHeader, DialogTitle } from './ui/dialog';
import type { UploadedFile, FileType } from '../App';

interface FileUploadAreaProps {
  uploadedFiles: UploadedFile[];
  onFileUpload: (files: File[]) => void;
  onRemoveFile: (index: number) => void;
  onFileTypeChange: (index: number, type: FileType) => void;

  // ✅ 新增：真正触发后端上传（App 里实现）
  onUploadFile?: (index: number) => void;
  onUploadAll?: () => void;

  disabled?: boolean;
}

interface PendingFile {
  file: File;
  type: FileType;
}

export function FileUploadArea({
  uploadedFiles,
  onFileUpload,
  onRemoveFile,
  onFileTypeChange,
  onUploadFile,
  onUploadAll,
  disabled = false,
}: FileUploadAreaProps) {
  const [isDragging, setIsDragging] = useState(false);
  const fileInputRef = useRef<HTMLInputElement>(null);
  const [pendingFiles, setPendingFiles] = useState<PendingFile[]>([]);
  const [showTypeDialog, setShowTypeDialog] = useState(false);

  const handleDragOver = (e: React.DragEvent) => {
    e.preventDefault();
    if (!disabled) setIsDragging(true);
  };

  const handleDragLeave = () => {
    setIsDragging(false);
  };

  const handleDrop = (e: React.DragEvent) => {
    e.preventDefault();
    setIsDragging(false);
    if (disabled) return;

    const files = Array.from(e.dataTransfer.files).filter((file) =>
      ['.pdf', '.docx', '.pptx'].some((ext) => file.name.toLowerCase().endsWith(ext))
    );

    if (files.length > 0) {
      setPendingFiles(files.map((file) => ({ file, type: 'other' as FileType })));
      setShowTypeDialog(true);
    }
  };

  const handleFileSelect = (e: React.ChangeEvent<HTMLInputElement>) => {
    const files = Array.from(e.target.files || []);
    if (files.length > 0) {
      setPendingFiles(files.map((file) => ({ file, type: 'other' as FileType })));
      setShowTypeDialog(true);
    }
    e.target.value = '';
  };

  const handleConfirmUpload = () => {
    // 这里只“入库”，不触发后端上传（符合你现在的逻辑）
    onFileUpload(pendingFiles.map((pf) => pf.file));

    // 把用户在弹窗里选的 type 同步到父组件列表（通过 index 偏移）
    const startIndex = uploadedFiles.length;
    pendingFiles.forEach((pf, idx) => {
      setTimeout(() => {
        onFileTypeChange(startIndex + idx, pf.type);
      }, 0);
    });

    setPendingFiles([]);
    setShowTypeDialog(false);
  };

  const handleCancelUpload = () => {
    setPendingFiles([]);
    setShowTypeDialog(false);
  };

  const handlePendingFileTypeChange = (index: number, type: FileType) => {
    setPendingFiles((prev) => prev.map((pf, i) => (i === index ? { ...pf, type } : pf)));
  };

  const getFileIcon = (filename: string) => {
    const lower = filename.toLowerCase();
    if (lower.endsWith('.pdf')) return FileText;
    if (lower.endsWith('.docx')) return File;
    if (lower.endsWith('.pptx')) return Presentation;
    return File;
  };

  const formatFileSize = (bytes: number) => {
    if (bytes < 1024) return bytes + ' B';
    if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' KB';
    return (bytes / (1024 * 1024)).toFixed(1) + ' MB';
  };

  const hasPendingUploads = uploadedFiles.some((f) => !f.uploaded);

  return (
    <Card className="p-4 space-y-3">
      <div className="flex items-center justify-between">
        <div className="flex items-center gap-2">
          <h4 className="text-sm">Course Materials</h4>
          {uploadedFiles.length > 0 && <Badge variant="secondary">{uploadedFiles.length} file(s)</Badge>}
        </div>

        {/* ✅ Upload All Pending（只在存在 pending 且提供了回调时显示） */}
        {uploadedFiles.length > 0 && hasPendingUploads && !!onUploadAll && (
          <Button
            variant="outline"
            size="sm"
            className="h-8 text-xs gap-2"
            disabled={disabled}
            onClick={(e) => {
              e.preventDefault();
              e.stopPropagation();
              onUploadAll();
            }}
            title="Upload all pending files"
          >
            <CloudUpload className="h-4 w-4" />
            Upload All
          </Button>
        )}
      </div>

      {/* Upload Area */}
      <div
        onDragOver={handleDragOver}
        onDragLeave={handleDragLeave}
        onDrop={handleDrop}
        className={`
          border-2 border-dashed rounded-lg p-4 text-center transition-colors
          ${isDragging ? 'border-primary bg-accent' : 'border-border'}
          ${disabled ? 'opacity-50 cursor-not-allowed' : 'cursor-pointer'}
        `}
        onClick={() => !disabled && fileInputRef.current?.click()}
      >
        <Upload className="h-6 w-6 mx-auto mb-2 text-muted-foreground" />
        <p className="text-sm text-muted-foreground mb-1">{disabled ? 'Please log in to upload' : 'Drop files or click to upload'}</p>
        <p className="text-xs text-muted-foreground">.pdf, .docx, .pptx</p>
        <input
          ref={fileInputRef}
          type="file"
          multiple
          accept=".pdf,.docx,.pptx"
          onChange={handleFileSelect}
          className="hidden"
          disabled={disabled}
        />
      </div>

      {/* Uploaded Files List */}
      {uploadedFiles.length > 0 && (
        <div className="space-y-3 max-h-64 overflow-y-auto">
          {uploadedFiles.map((uploadedFile, index) => {
            const Icon = getFileIcon(uploadedFile.file.name);
            const isUploaded = !!uploadedFile.uploaded;

            return (
              <div key={index} className="p-3 bg-muted rounded-md space-y-2">
                <div className="flex items-center gap-2 group">
                  <Icon className="h-4 w-4 text-muted-foreground flex-shrink-0" />
                  <div className="flex-1 min-w-0">
                    <p className="text-sm truncate">{uploadedFile.file.name}</p>
                    <p className="text-xs text-muted-foreground">{formatFileSize(uploadedFile.file.size)}</p>
                  </div>

                  {/* ✅ 单文件 Upload（仅未上传时显示 & 必须有回调） */}
                  {!isUploaded && !!onUploadFile && (
                    <Button
                      variant="secondary"
                      size="sm"
                      className="h-7 text-xs px-2"
                      disabled={disabled}
                      onClick={(e) => {
                        e.preventDefault();
                        e.stopPropagation();
                        onUploadFile(index);
                      }}
                      title="Upload this file to backend"
                    >
                      Upload
                    </Button>
                  )}

                  {/* ✅ 已上传状态 */}
                  {isUploaded && (
                    <Badge variant="secondary" className="text-[10px]">
                      Uploaded{typeof uploadedFile.uploadedChunks === 'number' ? ` (+${uploadedFile.uploadedChunks})` : ''}
                    </Badge>
                  )}

                  <Button
                    variant="ghost"
                    size="icon"
                    className="h-6 w-6 opacity-0 group-hover:opacity-100 transition-opacity"
                    onClick={(e) => {
                      e.stopPropagation();
                      onRemoveFile(index);
                    }}
                    title="Remove"
                  >
                    <X className="h-3 w-3" />
                  </Button>
                </div>

                <div className="space-y-1">
                  <label className="text-xs text-muted-foreground">File Type</label>
                  <Select value={uploadedFile.type} onValueChange={(value) => onFileTypeChange(index, value as FileType)}>
                    <SelectTrigger className="h-8 text-xs">
                      <SelectValue />
                    </SelectTrigger>
                    <SelectContent>
                      <SelectItem value="syllabus">Syllabus</SelectItem>
                      <SelectItem value="lecture-slides">Lecture Slides / PPT</SelectItem>
                      <SelectItem value="literature-review">Literature Review / Paper</SelectItem>
                      <SelectItem value="other">Other Course Document</SelectItem>
                    </SelectContent>
                  </Select>
                </div>
              </div>
            );
          })}
        </div>
      )}

      {/* Type Selection Dialog */}
      {showTypeDialog && (
        <Dialog open={showTypeDialog} onOpenChange={setShowTypeDialog}>
          <DialogContent className="sm:max-w-[425px]">
            <DialogHeader>
              <DialogTitle>Select File Types</DialogTitle>
              <DialogDescription>Please select the type for each file you are uploading.</DialogDescription>
            </DialogHeader>

            <div className="space-y-3 max-h-64 overflow-y-auto">
              {pendingFiles.map((pendingFile, index) => {
                const Icon = getFileIcon(pendingFile.file.name);
                return (
                  <div key={index} className="p-3 bg-muted rounded-md space-y-2">
                    <div className="flex items-center gap-2 group">
                      <Icon className="h-4 w-4 text-muted-foreground flex-shrink-0" />
                      <div className="flex-1 min-w-0">
                        <p className="text-sm truncate">{pendingFile.file.name}</p>
                        <p className="text-xs text-muted-foreground">{formatFileSize(pendingFile.file.size)}</p>
                      </div>
                    </div>

                    <div className="space-y-1">
                      <label className="text-xs text-muted-foreground">File Type</label>
                      <Select
                        value={pendingFile.type}
                        onValueChange={(value) => handlePendingFileTypeChange(index, value as FileType)}
                      >
                        <SelectTrigger className="h-8 text-xs">
                          <SelectValue />
                        </SelectTrigger>
                        <SelectContent>
                          <SelectItem value="syllabus">Syllabus</SelectItem>
                          <SelectItem value="lecture-slides">Lecture Slides / PPT</SelectItem>
                          <SelectItem value="literature-review">Literature Review / Paper</SelectItem>
                          <SelectItem value="other">Other Course Document</SelectItem>
                        </SelectContent>
                      </Select>
                    </div>
                  </div>
                );
              })}
            </div>

            <DialogFooter>
              <Button variant="outline" onClick={handleCancelUpload}>
                Cancel
              </Button>
              <Button onClick={handleConfirmUpload}>Upload</Button>
            </DialogFooter>
          </DialogContent>
        </Dialog>
      )}
    </Card>
  );
}