const API = (() => {
  const BASE = '/api';

  function token() { return localStorage.getItem('ev_token') || ''; }

  async function req(method, path, body = null, isForm = false) {
    const headers = {};
    if (token()) headers['Authorization'] = 'Bearer ' + token();
    let fetchBody = null;
    if (body) {
      if (isForm) {
        fetchBody = body;
      } else {
        headers['Content-Type'] = 'application/json';
        fetchBody = JSON.stringify(body);
      }
    }
    const res = await fetch(BASE + path, { method, headers, body: fetchBody });
    if (res.status === 401) { Auth.logout(); return; }
    if (!res.ok) {
      const err = await res.json().catch(() => ({ detail: '오류가 발생했습니다.' }));
      throw new Error(err.detail || '오류');
    }
    const ct = res.headers.get('content-type') || '';
    if (ct.includes('spreadsheet') || ct.includes('octet') || ct.includes('excel')) {
      return res.blob();
    }
    return res.json().catch(() => ({}));
  }

  // 엑셀 다운로드 전용 함수 — 인증 토큰 포함, 에러 처리 강화
  async function download(path, filename) {
    try {
      const headers = {};
      if (token()) headers['Authorization'] = 'Bearer ' + token();

      const res = await fetch(BASE + path, { method: 'GET', headers });

      if (res.status === 401) { Auth.logout(); return; }
      if (!res.ok) {
        const err = await res.json().catch(() => ({ detail: '다운로드 오류' }));
        throw new Error(err.detail || '다운로드 오류');
      }

      const blob = await res.blob();
      if (!blob || blob.size === 0) {
        alert('데이터가 없어 엑셀 파일을 생성할 수 없습니다.');
        return;
      }

      const url = URL.createObjectURL(blob);
      const a   = document.createElement('a');
      a.href     = url;
      a.download = filename;
      document.body.appendChild(a);
      a.click();
      document.body.removeChild(a);
      URL.revokeObjectURL(url);
    } catch(e) {
      alert('엑셀 다운로드 실패: ' + e.message);
    }
  }

  return {
    get:      (path)       => req('GET',    path),
    post:     (path, body) => req('POST',   path, body, body instanceof FormData),
    put:      (path, body) => req('PUT',    path, body, body instanceof FormData),
    patch:    (path, body) => req('PATCH',  path, body, body instanceof FormData),
    delete:   (path)       => req('DELETE', path),
    download,
  };
})();