import ExcelJS from 'exceljs';

// Brand palette — matches finance-workbook.ts / ActionButton's primary variant, kept as a
// small local copy rather than a shared import since these are two unrelated export domains.
const BRAND = 'FF14714C';
const BRAND_TINT = 'FFEAF5EF';
const INK = 'FF1F2937';
const MUTED = 'FF6B7280';
const BORDER = 'FFE2E5E1';
const WHITE = 'FFFFFFFF';

const THIN_BORDER: Partial<ExcelJS.Borders> = {
  top: { style: 'thin', color: { argb: BORDER } },
  left: { style: 'thin', color: { argb: BORDER } },
  bottom: { style: 'thin', color: { argb: BORDER } },
  right: { style: 'thin', color: { argb: BORDER } },
};

/** Column order is the contract — passenger-excel.ts reads by this same header order. */
export const PASSENGER_TEMPLATE_COLUMNS = [
  'Full Name',
  'Date of Birth (YYYY-MM-DD)',
  'Passenger Type',
  'ID Document Type',
  'ID Document Number',
  'Passport Number',
  'Passport Country',
  'Nationality',
  'Phone',
  'Email',
] as const;

const REQUIRED_ROW = 200;

export interface PassengerTemplateInput {
  trainNumber: string;
  origin: string;
  destination: string;
  travelDate: string;
  seatClassName: string;
  adultCount: number;
  childCount: number;
}

export async function buildPassengerTemplate(input: PassengerTemplateInput): Promise<Blob> {
  const wb = new ExcelJS.Workbook();
  wb.creator = 'EDR Passenger Backoffice';
  wb.created = new Date();

  const ws = wb.addWorksheet('Passengers', { views: [{ state: 'frozen', ySplit: 5 }] });
  ws.columns = PASSENGER_TEMPLATE_COLUMNS.map((h) => ({ width: h.length < 14 ? 18 : h.length + 4 }));

  // ── Title + trip context banner ──────────────────────────────────────────
  ws.mergeCells(1, 1, 1, PASSENGER_TEMPLATE_COLUMNS.length);
  const title = ws.getCell(1, 1);
  title.value = 'EDR Group Booking — Passenger Template';
  title.font = { bold: true, size: 16, color: { argb: WHITE } };
  title.fill = { type: 'pattern', pattern: 'solid', fgColor: { argb: BRAND } };
  title.alignment = { vertical: 'middle', horizontal: 'left', indent: 1 };
  ws.getRow(1).height = 30;
  for (let c = 1; c <= PASSENGER_TEMPLATE_COLUMNS.length; c++) ws.getCell(1, c).fill = title.fill;

  ws.mergeCells(2, 1, 2, PASSENGER_TEMPLATE_COLUMNS.length);
  const subtitle = ws.getCell(2, 1);
  subtitle.value = `Train ${input.trainNumber} · ${input.origin} → ${input.destination} · ${input.travelDate} · ${input.seatClassName}`;
  subtitle.font = { size: 11, color: { argb: INK } };
  subtitle.alignment = { vertical: 'middle', horizontal: 'left', indent: 1 };
  ws.getRow(2).height = 20;

  ws.mergeCells(3, 1, 3, PASSENGER_TEMPLATE_COLUMNS.length);
  const requirement = ws.getCell(3, 1);
  const total = input.adultCount + input.childCount;
  requirement.value = `Fill in exactly ${total} passenger row${total === 1 ? '' : 's'} below — ${input.adultCount} Adult${input.adultCount === 1 ? '' : 's'} + ${input.childCount} Child${input.childCount === 1 ? '' : 'ren'}. One row per passenger, in any order.`;
  requirement.font = { italic: true, size: 10, color: { argb: MUTED } };
  requirement.alignment = { vertical: 'middle', horizontal: 'left', indent: 1 };
  ws.getRow(3).height = 18;

  ws.mergeCells(4, 1, 4, PASSENGER_TEMPLATE_COLUMNS.length);
  const instructions = ws.getCell(4, 1);
  instructions.value =
    'Columns marked * are required. Date of Birth must be YYYY-MM-DD and not in the future — it determines Adult/Child pricing (under 5 = Child). ' +
    'ID Document Type must be one of: NATIONAL_ID, PASSPORT, DRIVING_LICENSE, OTHER. Do not rename or reorder columns.';
  instructions.font = { size: 9, color: { argb: MUTED } };
  instructions.alignment = { vertical: 'middle', horizontal: 'left', indent: 1, wrapText: true };
  ws.getRow(4).height = 28;

  // ── Header row ────────────────────────────────────────────────────────────
  const headerRow = ws.getRow(5);
  const requiredCols = new Set([0, 1, 2, 3]); // Full Name, DOB, Passenger Type, ID Document Type
  PASSENGER_TEMPLATE_COLUMNS.forEach((h, i) => {
    const cell = headerRow.getCell(i + 1);
    cell.value = requiredCols.has(i) ? `${h} *` : h;
    cell.font = { bold: true, color: { argb: WHITE }, size: 11 };
    cell.fill = { type: 'pattern', pattern: 'solid', fgColor: { argb: BRAND } };
    cell.alignment = { vertical: 'middle', horizontal: 'left', wrapText: true };
    cell.border = THIN_BORDER;
  });
  headerRow.height = 30;

  // ── One filled example row so the format is obvious at a glance ──────────
  const example = ws.getRow(6);
  const exampleValues = [
    'Abebe Kebede',
    '1990-05-15',
    'Adult',
    'NATIONAL_ID',
    'ET123456789',
    '',
    '',
    'Ethiopian',
    '+251911234567',
    'abebe@example.com',
  ];
  exampleValues.forEach((v, i) => {
    const cell = example.getCell(i + 1);
    cell.value = v;
    cell.font = { italic: true, color: { argb: MUTED } };
    cell.fill = { type: 'pattern', pattern: 'solid', fgColor: { argb: BRAND_TINT } };
    cell.border = THIN_BORDER;
  });

  // ── Blank rows with borders + dropdown validation for Passenger Type / ID Document Type ──
  // exceljs's types only expose per-cell `cell.dataValidation`, not a worksheet-level range API.
  for (let r = 7; r <= REQUIRED_ROW; r++) {
    const row = ws.getRow(r);
    for (let c = 1; c <= PASSENGER_TEMPLATE_COLUMNS.length; c++) {
      row.getCell(c).border = THIN_BORDER;
    }
    row.getCell(3).dataValidation = {
      type: 'list',
      allowBlank: true,
      formulae: ['"Adult,Child"'],
      showErrorMessage: true,
      errorTitle: 'Invalid Passenger Type',
      error: 'Choose Adult or Child.',
    };
    row.getCell(4).dataValidation = {
      type: 'list',
      allowBlank: true,
      formulae: ['"NATIONAL_ID,PASSPORT,DRIVING_LICENSE,OTHER"'],
      showErrorMessage: true,
      errorTitle: 'Invalid ID Document Type',
      error: 'Choose NATIONAL_ID, PASSPORT, DRIVING_LICENSE, or OTHER.',
    };
  }

  const buffer = await wb.xlsx.writeBuffer();
  return new Blob([buffer], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' });
}