import type { SchedulingSuggestion, CandidateVehicle } from './types';

function csvCell(v: string | number | null | undefined): string {
  if (v === null || v === undefined) return '';
  const s = typeof v === 'number' ? String(v) : v;
  if (/[",\n\r]/.test(s)) return `"${s.replace(/"/g, '""')}"`;
  return s;
}

function pickTopCandidate(s: SchedulingSuggestion): CandidateVehicle | null {
  if (s.candidates.length === 0) return null;
  const sameRegion = s.candidates.filter(c => c.isSameRegion);
  const pool = sameRegion.length > 0 ? sameRegion : s.candidates;
  return pool.find(c => c.canQualifyAfterSwap) ?? pool[0];
}

function pctString(rate: number): string {
  return (rate * 100).toFixed(1) + '%';
}

function typeLabel(s: SchedulingSuggestion): string {
  return s.type === 'replace_qualified' ? '里程高·换下' : '里程低·换走';
}

const HEADERS = [
  '车牌号',
  '业务部门',
  '业务负责人',
  '客户',
  '车型',
  '运营区域',
  '调度类型',
  '当前年里程(km)',
  '年度考核(km)',
  '年度完成率',
  '客户30日均(km)',
  '客户7日均(km)',
  '剩余天数',
  '最优候选车牌',
  '候选当前里程(km)',
  '候选替换后预估(km)',
  '候选可达标',
  '候选区域',
  '干预状态',
] as const;

export function buildSuggestionsCsv(suggestions: SchedulingSuggestion[]): string {
  const rows: string[] = [HEADERS.map(csvCell).join(',')];
  for (const s of suggestions) {
    const v = s.currentVehicle;
    const top = pickTopCandidate(s);
    const notifStatus =
      s.candidates.find(c => c.notificationStatus === 'executed') ? '已执行'
      : s.candidates.find(c => c.notificationStatus === 'sent') ? '待执行'
      : '';
    rows.push([
      csvCell(v.plateNumber),
      csvCell(v.department ?? ''),
      csvCell(v.manager ?? ''),
      csvCell(v.customer ?? ''),
      csvCell(v.vehicleType),
      csvCell(v.region),
      csvCell(typeLabel(s)),
      csvCell(Math.round(v.currentYearMileage)),
      csvCell(Math.round(v.yearTarget)),
      csvCell(pctString(v.completionRate)),
      csvCell(Math.round(v.customerAvgDaily)),
      csvCell(Math.round(v.customerAvgDaily7d)),
      csvCell(v.daysLeft),
      csvCell(top?.plateNumber ?? ''),
      csvCell(top ? Math.round(top.totalMileage) : ''),
      csvCell(top ? Math.round(top.predictedAfterSwap) : ''),
      csvCell(top ? (top.canQualifyAfterSwap ? '是' : '否') : ''),
      csvCell(top?.region ?? ''),
      csvCell(notifStatus),
    ].join(','));
  }
  return rows.join('\r\n');
}

export function downloadCsv(filename: string, csv: string): void {
  // UTF-8 BOM so Excel opens Chinese characters correctly
  const blob = new Blob(['\uFEFF', csv], { type: 'text/csv;charset=utf-8' });
  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);
}

export function exportSuggestionsCsv(suggestions: SchedulingSuggestion[], prefix = '调度建议'): void {
  const now = new Date();
  const y = now.getFullYear();
  const m = String(now.getMonth() + 1).padStart(2, '0');
  const d = String(now.getDate()).padStart(2, '0');
  const hh = String(now.getHours()).padStart(2, '0');
  const mm = String(now.getMinutes()).padStart(2, '0');
  const csv = buildSuggestionsCsv(suggestions);
  downloadCsv(`${prefix}_${y}${m}${d}_${hh}${mm}.csv`, csv);
}