import { useState, useRef } from 'react';
import { Upload, File, X, CheckCircle, AlertCircle } from 'lucide-react';

/*
 * SFR-02 공통컴포넌트: 파일 업로드
 */

interface FileUploadProps {
  /** 허용 확장자 (예: '.xlsx,.csv,.pdf') */
  accept?: string;
  /** 다중 파일 허용 */
  multiple?: boolean;
  /** 최대 파일 크기 (MB) */
  maxSizeMB?: number;
  /** 파일 선택 콜백 */
  onFilesSelected?: (files: File[]) => void;
  className?: string;
}

export function FileUpload({
  accept = '.xlsx,.csv,.pdf,.hwp,.docx',
  multiple = false,
  maxSizeMB = 50,
  onFilesSelected,
  className = '',
}: FileUploadProps) {
  const inputRef = useRef<HTMLInputElement>(null);
  const [files, setFiles] = useState<{ file: File; status: 'ready' | 'done' | 'error'; msg?: string }[]>([]);
  const [dragOver, setDragOver] = useState(false);

  const processFiles = (fileList: FileList) => {
    const newFiles = Array.from(fileList).map((file) => {
      if (file.size > maxSizeMB * 1024 * 1024) {
        return { file, status: 'error' as const, msg: `파일 크기 초과 (최대 ${maxSizeMB}MB)` };
      }
      return { file, status: 'ready' as const };
    });
    setFiles((prev) => (multiple ? [...prev, ...newFiles] : newFiles));
    onFilesSelected?.(newFiles.filter((f) => f.status === 'ready').map((f) => f.file));
  };

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

  const handleDrop = (e: React.DragEvent) => {
    e.preventDefault();
    setDragOver(false);
    if (e.dataTransfer.files.length) processFiles(e.dataTransfer.files);
  };

  const formatSize = (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`;
  };

  return (
    <div className={className}>
      <div
        onClick={() => inputRef.current?.click()}
        onDragOver={(e) => { e.preventDefault(); setDragOver(true); }}
        onDragLeave={() => setDragOver(false)}
        onDrop={handleDrop}
        className={`border-2 border-dashed rounded-lg p-6 text-center cursor-pointer transition-colors ${
          dragOver
            ? 'border-blue-500/50 bg-blue-500/5'
            : 'border-slate-700/50 hover:border-slate-600/50 hover:bg-surface-overlay'
        }`}
      >
        <Upload className="w-8 h-8 text-hint mx-auto mb-2" />
        <p className="text-[11px] text-muted-foreground">
          클릭하여 파일을 선택하거나 드래그하여 업로드
        </p>
        <p className="text-[9px] text-hint mt-1">
          {accept.replace(/\./g, '').toUpperCase().replace(/,/g, ' · ')} | 최대 {maxSizeMB}MB
          {multiple && ' | 다중 파일 가능'}
        </p>
        <input
          ref={inputRef}
          type="file"
          accept={accept}
          multiple={multiple}
          onChange={(e) => e.target.files && processFiles(e.target.files)}
          className="hidden"
        />
      </div>

      {/* 파일 목록 */}
      {files.length > 0 && (
        <div className="mt-2 space-y-1">
          {files.map((f, i) => (
            <div
              key={i}
              className={`flex items-center gap-2 px-3 py-2 rounded-lg text-[11px] ${
                f.status === 'error'
                  ? 'bg-red-500/10 border border-red-500/20'
                  : f.status === 'done'
                  ? 'bg-green-500/10 border border-green-500/20'
                  : 'bg-surface-overlay border border-border'
              }`}
            >
              {f.status === 'error' ? (
                <AlertCircle className="w-3.5 h-3.5 text-red-400 shrink-0" />
              ) : f.status === 'done' ? (
                <CheckCircle className="w-3.5 h-3.5 text-green-400 shrink-0" />
              ) : (
                <File className="w-3.5 h-3.5 text-hint shrink-0" />
              )}
              <span className="text-label truncate flex-1">{f.file.name}</span>
              <span className="text-hint text-[10px] shrink-0">{formatSize(f.file.size)}</span>
              {f.msg && <span className="text-red-400 text-[10px] shrink-0">{f.msg}</span>}
              <button type="button" aria-label={`${f.file.name} 제거`} onClick={() => removeFile(i)} className="text-hint hover:text-muted-foreground shrink-0">
                <X className="w-3 h-3" />
              </button>
            </div>
          ))}
        </div>
      )}
    </div>
  );
}