/**
 * Branded PDF documents: payment receipts and registration invoices.
 *
 * Both are generated with pdfkit into backend/temp and returned as
 * { filePath, filename } for callers to attach to an email/WhatsApp send and
 * clean up afterwards (see notifications.js).
 *
 * Line items are built the same tranche-aware way the user dashboard renders
 * them (backend/src/utils/pricing.js) — merging tranches that share a
 * name/price/tier and separating early-bird lines from standard-price ones —
 * so the PDF total always matches computeRegistrationTotalDue().
 */

const fs = require('fs');
const path = require('path');
const PDFDocument = require('pdfkit');
const QRCode = require('qrcode');
const { getSetting } = require('./settingsCache');

function fmtAmount(amt) {
  return `R${Number(amt || 0).toFixed(2)}`;
}

function fmtDate(d) {
  try { return new Date(d).toLocaleDateString('en-GB', { day: 'numeric', month: 'long', year: 'numeric' }); } catch { return ''; }
}

function formatMethod(method) {
  const m = String(method || '').toLowerCase();
  if (!m) return '—';
  if (m === 'eft') return 'EFT';
  return m.replace(/^./, c => c.toUpperCase());
}

function tempDir() {
  const dir = path.join(__dirname, '..', '..', 'temp');
  if (!fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true });
  return dir;
}

function docNumber(prefix, id, date) {
  const year = new Date(date || Date.now()).getFullYear();
  const short = String(id || '').replace(/-/g, '').slice(-6).toUpperCase() || '000000';
  return `${prefix}-${year}-${short}`;
}

async function getBranding() {
  const [name, address, email, phone, primary, accent, logoUrl] = await Promise.all([
    getSetting('org_name', process.env.ORG_NAME || 'Cross Code'),
    getSetting('org_address', ''),
    getSetting('org_email', process.env.EMAIL_FROM || process.env.EMAIL_USER || ''),
    getSetting('org_phone', ''),
    getSetting('primary_color', ''),
    getSetting('accent_color', ''),
    getSetting('logo_url', ''),
  ]);
  const url = (process.env.FRONTEND_URL || process.env.APP_BASE_URL || 'http://localhost:3001').replace(/\/$/, '');
  let logoPath = null;
  if (logoUrl) {
    const p = path.join(__dirname, '..', '..', 'public', logoUrl.replace(/^\//, ''));
    if (fs.existsSync(p)) logoPath = p;
  }
  return { name, address, email, phone, brandColor: primary || accent || '#1e3a5f', url, logoPath };
}

/**
 * Merge a registration's tranches into display rows, same grouping logic as
 * the user dashboard: one row per (name, unit price, early-bird flag), with
 * `basePrice` carried along so callers can work out the early-bird discount.
 */
function buildLineItems(registrationOptions) {
  const rows = [];
  for (const ro of (registrationOptions || [])) {
    const variantLabel = ro.variant?.name ? ` (${ro.variant.name})` : '';
    const label = `${ro.eventOption?.name || 'Option'}${variantLabel}`;
    const basePrice = Number((ro.variant?.price ?? ro.eventOption?.price ?? 0));
    const tranches = Array.isArray(ro.tranches) && ro.tranches.length > 0
      ? ro.tranches
      : [{
          quantity: ro.quantity,
          priceSnapshot: (ro.priceSnapshot !== null && ro.priceSnapshot !== undefined) ? Number(ro.priceSnapshot) : basePrice,
          appliedTierId: ro.appliedTierId,
        }];
    for (const t of tranches) {
      const unitPrice = Number(t.priceSnapshot || 0);
      const isEarlyBird = !!t.appliedTierId;
      const key = `${label}__${isEarlyBird}__${unitPrice}`;
      let row = rows.find(r => r.key === key);
      if (!row) { row = { key, label, quantity: 0, unitPrice, isEarlyBird, basePrice }; rows.push(row); }
      row.quantity += (t.quantity || 0);
    }
  }
  return rows;
}

/** Draws a two-column item table starting at `y`; returns the y position after the last row. */
function drawItemsTable(doc, { x, width, y, rows, brandColor, headerLight = true }) {
  const colDesc = x;
  // Fixed-width columns anchored to the right edge so amounts never wrap,
  // regardless of the overall table width (receipt vs. narrower invoice table).
  const totalColW = 75, priceColW = 65, qtyColW = 35;
  const colTotal = x + width - totalColW;
  const colPrice = colTotal - priceColW;
  const colQty = colPrice - qtyColW;
  const rowH = 22;

  if (headerLight) {
    doc.rect(x, y, width, rowH).fill('#f8fafc');
    doc.fillColor('#64748b').font('Helvetica-Bold').fontSize(9);
  } else {
    doc.rect(x, y, width, rowH).fill(brandColor);
    doc.fillColor('#ffffff').font('Helvetica-Bold').fontSize(9);
  }
  doc.text('DESCRIPTION', colDesc + 8, y + 7);
  doc.text('QTY', colQty, y + 7, { width: qtyColW - 8, align: 'right' });
  doc.text('PRICE', colPrice, y + 7, { width: priceColW - 8, align: 'right' });
  doc.text('TOTAL', colTotal, y + 7, { width: totalColW - 8, align: 'right' });
  y += rowH;

  doc.font('Helvetica').fontSize(10).fillColor('#374151');
  for (const row of rows) {
    doc.text(row.label + (row.isEarlyBird ? '  (early bird)' : ''), colDesc + 8, y + 6, { width: colQty - colDesc - 12 });
    doc.text(String(row.quantity), colQty, y + 6, { width: qtyColW - 8, align: 'right' });
    doc.text(fmtAmount(row.unitPrice), colPrice, y + 6, { width: priceColW - 8, align: 'right' });
    doc.text(fmtAmount(row.unitPrice * row.quantity), colTotal, y + 6, { width: totalColW - 8, align: 'right' });
    doc.moveTo(x, y + rowH).lineTo(x + width, y + rowH).strokeColor('#e2e8f0').lineWidth(0.5).stroke();
    y += rowH;
  }
  return y;
}

// ─── Payment receipt ──────────────────────────────────────────────────────────

/**
 * @param {object} payment - from notifications.js loadPaymentFull: amount, method, externalId,
 *   createdAt, user, registration { event, registrationOptions[{eventOption,variant,tranches}] }
 * @returns {Promise<{ filePath: string, filename: string }>}
 */
async function generateReceiptPdf(payment) {
  const org = await getBranding();
  const reg = payment.registration;
  const user = reg?.user || payment.user;
  const eventTitle = reg?.event?.title || payment.event?.title || 'Event';
  const eventStartDate = reg?.event?.startDate || payment.event?.startDate || null;
  const eventDate = eventStartDate ? fmtDate(eventStartDate) : '';
  const receiptNo = docNumber('RCPT', payment.id, payment.createdAt);
  const rows = reg ? buildLineItems(reg.registrationOptions) : [];

  const filename = `receipt-${receiptNo}.pdf`;
  const filePath = path.join(tempDir(), `${Date.now()}-${filename}`);
  const doc = new PDFDocument({ size: 'A4', margin: 0 });
  const writeStream = fs.createWriteStream(filePath);
  doc.pipe(writeStream);

  const pageWidth = doc.page.width;
  const pageHeight = doc.page.height;
  const marginX = 40;

  // Header banner
  const bannerH = 150;
  doc.rect(0, 0, pageWidth, bannerH).fill(org.brandColor);
  if (org.logoPath) {
    try { doc.image(org.logoPath, marginX, 28, { fit: [36, 36] }); } catch {}
  }
  doc.fillColor('#ffffff').font('Helvetica-Bold').fontSize(13).text(org.name, marginX + (org.logoPath ? 46 : 0), 38, { width: 260 });
  doc.font('Helvetica-Bold').fontSize(26).text('Payment Receipt', marginX, 68, { width: 320 });
  doc.font('Helvetica').fontSize(11).text('Thank you for your payment.', marginX, 102, { width: 320 });
  if (eventStartDate) doc.font('Helvetica-Bold').fontSize(10).text('We look forward to seeing you at the event!', marginX, 122, { width: 320 });

  const metaX = pageWidth - 250;
  const meta = [
    ['Receipt No.', receiptNo],
    ['Date', fmtDate(payment.createdAt)],
    ['Payment Method', formatMethod(payment.method)],
    ['Transaction ID', payment.externalId || payment.id.slice(0, 12)],
  ];
  let metaY = 34;
  for (const [label, value] of meta) {
    doc.font('Helvetica').fontSize(9).fillColor('#ffffff').fillOpacity(0.75).text(label, metaX, metaY, { width: 90 });
    doc.font('Helvetica-Bold').fontSize(9).fillColor('#ffffff').fillOpacity(1).text(value, metaX + 90, metaY, { width: 120, align: 'right' });
    metaY += 24;
  }

  // Body
  let y = bannerH + 30;
  doc.font('Helvetica-Bold').fontSize(10).fillColor(org.brandColor).text('PAYER DETAILS', marginX, y);
  doc.font('Helvetica-Bold').fontSize(10).fillColor(org.brandColor).text('EVENT DETAILS', marginX + 280, y);
  y += 16;
  doc.font('Helvetica-Bold').fontSize(11).fillColor('#0f172a').text(user?.name || 'Guest', marginX, y);
  doc.font('Helvetica-Bold').fontSize(11).fillColor('#0f172a').text(eventTitle, marginX + 280, y, { width: 240 });
  y += 16;
  doc.font('Helvetica').fontSize(9).fillColor('#374151').text(user?.email || '', marginX, y);
  if (eventDate) doc.font('Helvetica').fontSize(9).fillColor('#374151').text(eventDate, marginX + 280, y);
  y += 14;
  if (user?.phoneNumber) doc.font('Helvetica').fontSize(9).fillColor('#374151').text(user.phoneNumber, marginX, y);
  y += 30;

  if (rows.length > 0) {
    y = drawItemsTable(doc, { x: marginX, width: pageWidth - marginX * 2, y, rows, brandColor: org.brandColor });
  }
  y += 20;

  const boxW = 160, boxH = 32;
  doc.font('Helvetica-Bold').fontSize(10).fillColor(org.brandColor).text('TOTAL PAID', pageWidth - marginX - boxW - 110, y + 10, { width: 90, align: 'right' });
  doc.roundedRect(pageWidth - marginX - boxW, y, boxW, boxH, 4).fill(org.brandColor);
  doc.font('Helvetica-Bold').fontSize(14).fillColor('#ffffff').text(fmtAmount(payment.amount), pageWidth - marginX - boxW, y + 9, { width: boxW, align: 'center' });
  y += boxH + 30;

  // Footer
  const footerH = 60;
  const footerY = Math.max(pageHeight - footerH, y + 20);
  doc.rect(0, footerY, pageWidth, footerH).fill('#0f172a');
  doc.font('Helvetica-BoldOblique').fontSize(16).fillColor('#ffffff').text('Thank you!', marginX, footerY + 20);
  doc.font('Helvetica').fontSize(9).fillColor('#94a3b8').text(org.url.replace(/^https?:\/\//, ''), 0, footerY + 24, { width: pageWidth - marginX, align: 'right' });

  doc.end();
  await new Promise((resolve, reject) => { writeStream.on('finish', resolve); writeStream.on('error', reject); });
  return { filePath, filename };
}

// ─── Invoice ───────────────────────────────────────────────────────────────────

/**
 * @param {object} registration - from notifications.js loadRegistrationFull: id, createdAt,
 *   user, event, registrationOptions[{eventOption,variant,tranches}], payments
 * @param {{ paymentUrl?: string|null, totalDue?: number, totalPaid?: number }} opts
 * @returns {Promise<{ filePath: string, filename: string }>}
 */
async function generateInvoicePdf(registration, { paymentUrl = null, totalDue = null, totalPaid = null } = {}) {
  const org = await getBranding();
  const { computeRegistrationTotalDue } = require('./pricing');
  const due = totalDue !== null ? totalDue : computeRegistrationTotalDue(registration, new Date());
  const paid = totalPaid !== null ? totalPaid : (registration.payments || []).reduce((s, p) => s + (p.amount || 0), 0);
  const balance = Math.max(due - paid, 0);
  const invoiceNo = docNumber('INV', registration.id, registration.createdAt);
  const rows = buildLineItems(registration.registrationOptions);

  // Subtotal/discount: only early-bird rows are compared against today's base price, so an
  // ordinary base-price change over time never shows up as a false "discount" on standard rows.
  const fullPriceTotal = rows.reduce((s, r) => s + (r.isEarlyBird ? r.basePrice : r.unitPrice) * r.quantity, 0);
  const chargedTotal = rows.reduce((s, r) => s + r.unitPrice * r.quantity, 0);
  const discount = Math.max(0, fullPriceTotal - chargedTotal);

  const filename = `invoice-${invoiceNo}.pdf`;
  const filePath = path.join(tempDir(), `${Date.now()}-${filename}`);
  const doc = new PDFDocument({ size: 'A4', margin: 0 });
  const writeStream = fs.createWriteStream(filePath);
  doc.pipe(writeStream);

  const pageWidth = doc.page.width;
  const pageHeight = doc.page.height;
  const sidebarW = 190;
  const mainX = sidebarW + 30;
  const mainW = pageWidth - mainX - 40;

  // Sidebar
  doc.rect(0, 0, sidebarW, pageHeight).fill('#111827');
  let sy = 40;
  if (org.logoPath) {
    try { doc.image(org.logoPath, 28, sy, { fit: [32, 32] }); sy += 0; } catch {}
  }
  doc.font('Helvetica-Bold').fontSize(12).fillColor('#ffffff').text(org.name, org.logoPath ? 68 : 28, sy + 8, { width: sidebarW - (org.logoPath ? 96 : 56) });
  sy += 60;
  doc.font('Helvetica-Bold').fontSize(20).fillColor('#ffffff').text('INVOICE', 28, sy, { width: sidebarW - 56 });
  sy += 28;
  doc.font('Helvetica-Bold').fontSize(11).fillColor(org.brandColor).text(invoiceNo, 28, sy, { width: sidebarW - 56 });
  sy += 34;
  doc.font('Helvetica').fontSize(8).fillColor('#94a3b8').text('DATE ISSUED', 28, sy);
  doc.font('Helvetica-Bold').fontSize(9).fillColor('#ffffff').text(fmtDate(registration.createdAt), 28, sy + 11);
  sy += 40;
  doc.font('Helvetica').fontSize(8).fillColor(org.brandColor).text('BILL TO', 28, sy);
  sy += 13;
  doc.font('Helvetica-Bold').fontSize(10).fillColor('#ffffff').text(registration.user?.name || 'Guest', 28, sy, { width: sidebarW - 56 });
  sy += 15;
  doc.font('Helvetica').fontSize(8).fillColor('#cbd5e1').text(registration.user?.email || '', 28, sy, { width: sidebarW - 56 });
  sy += 12;
  if (registration.user?.phoneNumber) { doc.font('Helvetica').fontSize(8).fillColor('#cbd5e1').text(registration.user.phoneNumber, 28, sy, { width: sidebarW - 56 }); sy += 12; }

  let by = pageHeight - 140;
  doc.font('Helvetica-Bold').fontSize(9).fillColor('#ffffff').text(org.name, 28, by, { width: sidebarW - 56 });
  by += 13;
  if (org.address) { doc.font('Helvetica').fontSize(8).fillColor('#94a3b8').text(org.address, 28, by, { width: sidebarW - 56 }); by += 12 * Math.ceil(org.address.length / 28); }
  if (org.email) { doc.font('Helvetica').fontSize(8).fillColor('#94a3b8').text(org.email, 28, by, { width: sidebarW - 56 }); by += 12; }
  doc.font('Helvetica').fontSize(8).fillColor('#94a3b8').text(org.url.replace(/^https?:\/\//, ''), 28, by, { width: sidebarW - 56 });

  // Main content
  let y = 40;
  doc.font('Helvetica-Bold').fontSize(9).fillColor(org.brandColor).text('EVENT', mainX, y);
  y += 14;
  doc.font('Helvetica-Bold').fontSize(14).fillColor('#0f172a').text(registration.event?.title || 'Event', mainX, y, { width: mainW });
  y += 18;
  if (registration.event?.startDate) { doc.font('Helvetica').fontSize(9).fillColor('#64748b').text(fmtDate(registration.event.startDate), mainX, y); y += 14; }
  y += 16;

  y = drawItemsTable(doc, { x: mainX, width: mainW, y, rows, brandColor: org.brandColor, headerLight: false });
  y += 16;

  const totalsX = mainX + mainW - 220;
  const totalLine = (label, value, opts = {}) => {
    doc.font(opts.bold ? 'Helvetica-Bold' : 'Helvetica').fontSize(opts.size || 10).fillColor(opts.color || '#374151')
      .text(label, totalsX, y, { width: 120 });
    doc.font(opts.bold ? 'Helvetica-Bold' : 'Helvetica').fontSize(opts.size || 10).fillColor(opts.color || '#374151')
      .text(value, totalsX + 120, y, { width: 100, align: 'right' });
    y += (opts.size || 10) + 10;
  };
  if (discount > 0.01) {
    totalLine('SUBTOTAL', fmtAmount(fullPriceTotal));
    totalLine('DISCOUNT', `-${fmtAmount(discount)}`, { color: '#059669' });
    doc.moveTo(totalsX, y).lineTo(totalsX + 220, y).strokeColor('#e2e8f0').stroke();
    y += 8;
  }
  totalLine('TOTAL DUE', fmtAmount(due), { bold: true, size: 13, color: org.brandColor });
  if (paid > 0) totalLine('Already paid', `-${fmtAmount(paid)}`, { size: 9 });
  if (paid > 0) totalLine('BALANCE DUE', fmtAmount(balance), { bold: true, size: 12, color: balance > 0 ? org.brandColor : '#059669' });
  y += 20;

  // Payment section
  if (balance > 0.01) {
    doc.font('Helvetica-Bold').fontSize(10).fillColor(org.brandColor).text('PAYMENT', mainX, y);
    y += 16;
    if (paymentUrl) {
      const qrSize = 100;
      try {
        const qrBuffer = await QRCode.toBuffer(paymentUrl, { width: qrSize, margin: 1 });
        doc.image(qrBuffer, mainX + mainW - qrSize, y, { width: qrSize, height: qrSize });
        doc.font('Helvetica').fontSize(8).fillColor('#94a3b8').text('Scan to pay', mainX + mainW - qrSize, y + qrSize + 4, { width: qrSize, align: 'center' });
      } catch {}
      doc.font('Helvetica').fontSize(9).fillColor('#374151').text('Pay online — tap the link or scan the QR code:', mainX, y, { width: mainW - 120 });
      doc.font('Helvetica-Bold').fontSize(10).fillColor('#2563eb').text(paymentUrl, mainX, y + 16, { width: mainW - 120, link: paymentUrl, underline: true });
      y += 60;
    } else {
      doc.font('Helvetica').fontSize(9).fillColor('#374151').text(`Pay online at ${org.url} or at the door (cash/card).`, mainX, y, { width: mainW });
      y += 24;
    }
  } else {
    doc.font('Helvetica-Bold').fontSize(11).fillColor('#059669').text('PAID IN FULL', mainX, y);
    y += 24;
  }

  // Footer
  const footerH = 40;
  const footerY = Math.max(pageHeight - footerH, y + 20);
  doc.rect(sidebarW, footerY, pageWidth - sidebarW, footerH).fill(org.brandColor);
  doc.font('Helvetica-Bold').fontSize(11).fillColor('#ffffff').text('Thank you for your support!', sidebarW, footerY + 13, { width: pageWidth - sidebarW, align: 'center' });

  doc.end();
  await new Promise((resolve, reject) => { writeStream.on('finish', resolve); writeStream.on('error', reject); });
  return { filePath, filename };
}

module.exports = { generateReceiptPdf, generateInvoicePdf, buildLineItems, getBranding, docNumber };