'use client';

import React, { useState, useCallback, useRef } from 'react';
import {
  Upload,
  FileSpreadsheet,
  Download,
  CheckCircle2,
  XCircle,
  AlertCircle,
  Loader2,
} from 'lucide-react';

export interface BatchResult {
  totalCount: number;
  successCount: number;
  failCount: number;
  failures: { row: number; reason: string }[];
  data?: any[];
}

export interface ExcelUploaderProps {
  title: string;
  description?: string;
  templateUrl?: string;
  uploadUrl: string;
  onSuccess?: (result: BatchResult) => void;
  accept?: string;
}

interface PreviewData {
  headers: string[];
  rows: string[][];
}

export default function ExcelUploader({
  title,
  description,
  templateUrl,
  uploadUrl,
  onSuccess,
  accept = '.xlsx',
}: ExcelUploaderProps) {
  const [file, setFile] = useState<File | null>(null);
  const [preview, setPreview] = useState<PreviewData | null>(null);
  const [rowCount, setRowCount] = useState(0);
  const [isDragging, setIsDragging] = useState(false);
  const [isUploading, setIsUploading] = useState(false);
  const [result, setResult] = useState<BatchResult | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [showFailures, setShowFailures] = useState(false);

  const fileInputRef = useRef<HTMLInputElement>(null);

  const resetState = useCallback(() => {
    setFile(null);
    setPreview(null);
    setRowCount(0);
    setResult(null);
    setError(null);
    setShowFailures(false);
    if (fileInputRef.current) {
      fileInputRef.current.value = '';
    }
  }, []);

  const handleFile = useCallback((selectedFile: File) => {
    if (!selectedFile.name.endsWith('.xlsx')) {
      setError('지원하지 않는 파일 형식입니다. .xlsx 파일을 선택해주세요.');
      return;
    }

    setError(null);
    setResult(null);
    setFile(selectedFile);
    setShowFailures(false);

    // Parse file for preview (filename + row count estimation)
    const reader = new FileReader();
    reader.onload = (e) => {
      try {
        // Simple row count from binary content (approximate)
        // In production, you'd use xlsx library for proper parsing
        const content = e.target?.result;
        if (content) {
          // For preview purposes, we'll just show the filename
          // A full xlsx parser would be needed for actual cell data
          setRowCount(0); // Will be updated by server response
          setPreview(null); // Preview requires xlsx library
        }
      } catch {
        // Ignore parse errors for preview
      }
    };
    reader.readAsArrayBuffer(selectedFile);
  }, []);

  const handleDragOver = useCallback((e: React.DragEvent) => {
    e.preventDefault();
    setIsDragging(true);
  }, []);

  const handleDragLeave = useCallback((e: React.DragEvent) => {
    e.preventDefault();
    setIsDragging(false);
  }, []);

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

    const droppedFile = e.dataTransfer.files[0];
    if (droppedFile) {
      handleFile(droppedFile);
    }
  }, [handleFile]);

  const handleFileSelect = useCallback((e: React.ChangeEvent<HTMLInputElement>) => {
    const selectedFile = e.target.files?.[0];
    if (selectedFile) {
      handleFile(selectedFile);
    }
  }, [handleFile]);

  const handleUpload = useCallback(async () => {
    if (!file) return;

    setIsUploading(true);
    setError(null);
    setResult(null);

    try {
      const formData = new FormData();
      formData.append('file', file);

      const response = await fetch(uploadUrl, {
        method: 'POST',
        body: formData,
      });

      const json = await response.json();

      if (!response.ok || !json.success) {
        throw new Error(json.message || '업로드 중 오류가 발생했습니다.');
      }

      const batchResult: BatchResult = json.data;
      setResult(batchResult);
      setRowCount(batchResult.totalCount);

      if (batchResult.failCount === 0 && onSuccess) {
        onSuccess(batchResult);
      }
    } catch (err) {
      const message = err instanceof Error ? err.message : '알 수 없는 오류가 발생했습니다.';
      setError(message);
    } finally {
      setIsUploading(false);
    }
  }, [file, uploadUrl, onSuccess]);

  const handleDownloadTemplate = useCallback(() => {
    if (templateUrl) {
      window.open(templateUrl, '_blank');
    }
  }, [templateUrl]);

  return (
    <div className="rounded-2xl bg-white border border-gray-200 shadow-sm p-6">
      {/* Header */}
      <div className="mb-6">
        <h3 className="text-lg font-semibold text-gray-900">{title}</h3>
        {description && (
          <p className="mt-1 text-sm text-gray-500">{description}</p>
        )}
      </div>

      {/* Drop Zone */}
      <div
        onDragOver={handleDragOver}
        onDragLeave={handleDragLeave}
        onDrop={handleDrop}
        onClick={() => fileInputRef.current?.click()}
        className={`
          relative border-2 border-dashed rounded-xl p-8 text-center cursor-pointer
          transition-colors duration-200
          ${isDragging
            ? 'border-indigo-500 bg-indigo-50'
            : 'border-gray-300 hover:border-indigo-400 hover:bg-gray-50'
          }
        `}
      >
        <input
          ref={fileInputRef}
          type="file"
          accept={accept}
          onChange={handleFileSelect}
          className="hidden"
        />
        <FileSpreadsheet className="mx-auto h-10 w-10 text-gray-400" />
        <p className="mt-3 text-sm text-gray-600">
          엑셀 파일을 드래그하거나 <span className="text-indigo-600 font-medium">[파일 선택]</span>
        </p>
        <p className="mt-1 text-xs text-gray-400">지원 형식: {accept}</p>
      </div>

      {/* Template Download */}
      {templateUrl && (
        <div className="mt-4">
          <button
            type="button"
            onClick={handleDownloadTemplate}
            className="inline-flex items-center gap-2 text-sm text-indigo-600 hover:text-indigo-700 font-medium"
          >
            <Download className="h-4 w-4" />
            템플릿 다운로드
          </button>
        </div>
      )}

      {/* File Info */}
      {file && (
        <div className="mt-6 p-4 bg-gray-50 rounded-xl border border-gray-200">
          <div className="flex items-center justify-between">
            <div className="flex items-center gap-3">
              <FileSpreadsheet className="h-5 w-5 text-indigo-600" />
              <div>
                <p className="text-sm font-medium text-gray-900">{file.name}</p>
                <p className="text-xs text-gray-500">
                  {rowCount > 0 ? `${rowCount}행` : '행 수 분석 중...'}
                </p>
              </div>
            </div>
            <button
              type="button"
              onClick={resetState}
              className="text-xs text-gray-500 hover:text-gray-700"
            >
              취소
            </button>
          </div>
        </div>
      )}

      {/* Preview Table */}
      {preview && (
        <div className="mt-6">
          <h4 className="text-sm font-medium text-gray-700 mb-3">미리보기</h4>
          <div className="overflow-x-auto rounded-lg border border-gray-200">
            <table className="min-w-full divide-y divide-gray-200">
              <thead className="bg-gray-50">
                <tr>
                  {preview.headers.map((header, i) => (
                    <th
                      key={i}
                      className="px-4 py-2 text-left text-xs font-medium text-gray-500 uppercase tracking-wider"
                    >
                      {header}
                    </th>
                  ))}
                </tr>
              </thead>
              <tbody className="bg-white divide-y divide-gray-200">
                {preview.rows.slice(0, 5).map((row, i) => (
                  <tr key={i}>
                    {row.map((cell, j) => (
                      <td key={j} className="px-4 py-2 text-sm text-gray-900 whitespace-nowrap">
                        {cell}
                      </td>
                    ))}
                  </tr>
                ))}
              </tbody>
            </table>
          </div>
          {preview.rows.length > 5 && (
            <p className="mt-2 text-xs text-gray-500">
              상위 5행만 표시됩니다 (총 {preview.rows.length}행)
            </p>
          )}
        </div>
      )}

      {/* Upload Button */}
      {file && !result && (
        <div className="mt-6">
          <button
            type="button"
            onClick={handleUpload}
            disabled={isUploading}
            className="inline-flex items-center justify-center gap-2 px-6 py-2.5 bg-indigo-600 text-white text-sm font-medium rounded-xl hover:bg-indigo-700 disabled:opacity-50 disabled:cursor-not-allowed transition-colors"
          >
            {isUploading ? (
              <>
                <Loader2 className="h-4 w-4 animate-spin" />
                업로드 중...
              </>
            ) : (
              <>
                <Upload className="h-4 w-4" />
                일괄 등록
              </>
            )}
          </button>
        </div>
      )}

      {/* Error State */}
      {error && (
        <div className="mt-6 p-4 bg-red-50 border border-red-200 rounded-xl">
          <div className="flex items-start gap-3">
            <AlertCircle className="h-5 w-5 text-red-500 mt-0.5 flex-shrink-0" />
            <div>
              <p className="text-sm font-medium text-red-800">오류</p>
              <p className="mt-1 text-sm text-red-700">{error}</p>
            </div>
          </div>
        </div>
      )}

      {/* Results */}
      {result && (
        <div className="mt-6 space-y-4">
          {/* Summary */}
          <div className={`p-4 rounded-xl border ${
            result.failCount === 0
              ? 'bg-green-50 border-green-200'
              : 'bg-amber-50 border-amber-200'
          }`}>
            <div className="flex items-center gap-3">
              {result.failCount === 0 ? (
                <CheckCircle2 className="h-5 w-5 text-green-600" />
              ) : (
                <AlertCircle className="h-5 w-5 text-amber-600" />
              )}
              <p className={`text-sm font-medium ${
                result.failCount === 0 ? 'text-green-800' : 'text-amber-800'
              }`}>
                {result.totalCount}건 중 {result.successCount}건 성공
                {result.failCount > 0 && `, ${result.failCount}건 실패`}
              </p>
            </div>
          </div>

          {/* Failure Details */}
          {result.failCount > 0 && (
            <div className="border border-gray-200 rounded-xl overflow-hidden">
              <button
                type="button"
                onClick={() => setShowFailures(!showFailures)}
                className="w-full flex items-center justify-between px-4 py-3 bg-gray-50 hover:bg-gray-100 transition-colors"
              >
                <div className="flex items-center gap-2">
                  <XCircle className="h-4 w-4 text-red-500" />
                  <span className="text-sm font-medium text-gray-700">실패 상세</span>
                  <span className="text-xs text-gray-500">({result.failures.length}건)</span>
                </div>
                <svg
                  className={`h-4 w-4 text-gray-500 transition-transform ${showFailures ? 'rotate-180' : ''}`}
                  fill="none"
                  viewBox="0 0 24 24"
                  stroke="currentColor"
                >
                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 9l-7 7-7-7" />
                </svg>
              </button>

              {showFailures && (
                <div className="divide-y divide-gray-200 max-h-64 overflow-y-auto">
                  {result.failures.map((failure, i) => (
                    <div key={i} className="px-4 py-3">
                      <div className="flex items-start gap-2">
                        <span className="text-xs font-mono text-gray-500 bg-gray-100 px-2 py-0.5 rounded">
                          Row {failure.row}
                        </span>
                        <p className="text-sm text-red-600">{failure.reason}</p>
                      </div>
                    </div>
                  ))}
                </div>
              )}
            </div>
          )}

          {/* Reset Button */}
          <button
            type="button"
            onClick={resetState}
            className="text-sm text-indigo-600 hover:text-indigo-700 font-medium"
          >
            다른 파일 업로드
          </button>
        </div>
      )}
    </div>
  );
}