/**
 * WhatsApp-formatted message builders.
 *
 * Styling reference: https://faq.whatsapp.com/539178204879377/
 *   *bold*    _italic_    ~strikethrough~    ```monospace```
 *   > blockquote    - unordered list    1. numbered list
 *   # Heading 1    ## Heading 2    ### Heading 3
 */

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

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

const { getSettingSync } = require('./settingsCache');

function getOrg() {
  return {
    name:  getSettingSync('org_name', process.env.ORG_NAME || 'Hope Events'),
    email: process.env.EMAIL_FROM || process.env.EMAIL_USER || '',
    url:   (process.env.FRONTEND_URL || process.env.APP_BASE_URL || 'http://localhost:3001').replace(/\/$/, ''),
  };
}

// ─── Registration confirmation ────────────────────────────────────────────────

/**
 * @param {object} reg - full registration from loadRegistrationFull
 * @param {{ isNew?: boolean, balance?: number, totalDue?: number, totalPaid?: number }} opts
 */
function buildWARegistration(reg, { isNew = true, balance, totalDue, totalPaid } = {}) {
  const org = getOrg();
  const eventTitle = reg.event?.title || 'the event';
  const eventDate  = reg.event?.startDate ? fmtDateShort(reg.event.startDate) : '';
  const name       = reg.user?.name || 'there';

  const heading = isNew ? '🎉 *Registration Confirmed!*' : '✏️ *Registration Updated*';
  const intro = isNew
    ? `You're registered for *${eventTitle}*${eventDate ? ` on ${eventDate}` : ''}.`
    : `Your registration for *${eventTitle}* has been updated.`;

  const items = (reg.registrationOptions || [])
    .map(ro => `- ${ro.eventOption?.name || 'Option'} ×${ro.quantity} — ${fmtAmount((ro.eventOption?.price || 0) * ro.quantity)}`)
    .join('\n');

  const paid    = totalPaid  ?? (reg.payments || []).reduce((s, p) => s + (p.amount || 0), 0);
  const due     = totalDue   ?? 0;
  const bal     = balance    ?? Math.max(due - paid, 0);

  const finLine = bal <= 0
    ? `✅ *Fully paid — you're all set!*`
    : `*Balance due:* ${fmtAmount(bal)}\n_Pay at ${org.url} or at the door._`;

  return [
    heading,
    '',
    `Hi ${name},`,
    '',
    intro,
    '',
    '*Your selections:*',
    items || '—',
    '',
    `*Total:* ${fmtAmount(due)}   *Paid:* ${fmtAmount(paid)}`,
    finLine,
    '',
    `_${org.name}_ | ${org.url}`,
  ].join('\n');
}

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

function buildWAPayment(payment) {
  const org        = getOrg();
  const eventTitle = payment.registration?.event?.title || payment.event?.title || 'the event';
  const name       = (payment.registration?.user || payment.user)?.name || 'there';
  const amount     = fmtAmount(payment.amount);

  const reg     = payment.registration;
  let balLine   = '';
  if (reg) {
    const { computeRegistrationTotalDue } = require('./pricing');
    const totalDue  = computeRegistrationTotalDue(reg, payment.createdAt || new Date());
    const totalPaid = (reg.payments || []).reduce((s, p) => s + (p.amount || 0), 0);
    const balance   = Math.max(totalDue - totalPaid, 0);
    balLine = balance <= 0
      ? `\n✅ *Fully paid!* Your tickets have been sent.`
      : `\n*Remaining balance:* ${fmtAmount(balance)}\n_Pay the remainder at ${org.url} or at the door._`;
  }

  return [
    `✅ *Payment Received*`,
    '',
    `Hi ${name},`,
    '',
    `We've received your payment of *${amount}* for *${eventTitle}*.`,
    balLine,
    '',
    `_${org.name}_ | ${org.url}`,
  ].join('\n');
}

// ─── Check-in confirmation (Main Tickets, door check-in) ───────────────────────

function buildWACheckIn(ticket, qtyRedeemed, totalRedeemed, remaining) {
  const org        = getOrg();
  const eventTitle = ticket.event?.title || 'the event';
  const name       = ticket.user?.name || 'there';
  const fullyCheckedIn = remaining <= 0;

  return [
    `✅ *Checked In*`,
    '',
    `Hi ${name},`,
    '',
    `*${qtyRedeemed}* checked in for *${eventTitle}*.`,
    `*${totalRedeemed} of ${ticket.quantity || 1}* checked in${fullyCheckedIn ? '' : `, *${remaining}* remaining`}.`,
    '',
    `_${org.name}_ | ${org.url}`,
  ].join('\n');
}

// ─── Login notification ───────────────────────────────────────────────────────

function buildWALogin({ name, when, location, userAgent }) {
  const org = getOrg();
  return [
    `🔐 *New Login Detected*`,
    '',
    `Hi ${name || 'there'},`,
    '',
    `A new login to your *${org.name}* account was detected.`,
    '',
    `*Time:* ${when}`,
    `*Location:* ${location}`,
    `*Device:* ${userAgent}`,
    '',
    `> _Not you?_ Change your password immediately at ${org.url} or contact ${org.email}.`,
    '',
    `_If this was you, no action is needed._`,
  ].join('\n');
}

// ─── Welcome ──────────────────────────────────────────────────────────────────

function buildWAWelcome({ name, events }) {
  const org  = getOrg();
  const hasEvents = Array.isArray(events) && events.length > 0;

  const eventsBlock = hasEvents
    ? [
        '*Upcoming events:*',
        ...events.map(e =>
          `- *${e.title}* — ${new Date(e.startDate).toLocaleDateString('en-GB', { day: 'numeric', month: 'short', year: 'numeric' })}`
        ),
      ].join('\n')
    : 'Keep an eye on our website for upcoming events.';

  return [
    `🎉 *Welcome to ${org.name}!*`,
    '',
    `Hi ${name || 'there'},`,
    '',
    `Your account is set up and ready. Use it to register for events, manage your bookings, and access your tickets.`,
    '',
    eventsBlock,
    '',
    `${org.url}`,
  ].join('\n');
}

// ─── Account closed ───────────────────────────────────────────────────────────

function buildWAAccountClosed({ name, dataDeleted }) {
  const org = getOrg();
  const detail = dataDeleted
    ? 'All personal data associated with your account has been permanently deleted.'
    : `Your account has been deactivated. To also delete your personal data, contact ${org.email}.`;

  return [
    `🔒 *Account Closed*`,
    '',
    `Hi ${name || 'there'},`,
    '',
    `Your *${org.name}* account has been successfully closed.`,
    '',
    detail,
    '',
    `_${org.name}_ | ${org.email}`,
  ].join('\n');
}

// ─── Ticket delivery caption ──────────────────────────────────────────────────

function buildWATicketCaption({ name, eventTitle, eventDate }) {
  return [
    `🎟️ *Your tickets for ${eventTitle}*`,
    '',
    `Hi ${name || 'there'}! Your tickets${eventDate ? ` for *${eventDate}*` : ''} are attached.`,
    'Please show this PDF (printed or on your phone) at the event entrance.',
  ].join('\n');
}

// ─── Refund notification ──────────────────────────────────────────────────────

function buildWARefund(payment) {
  const org        = getOrg();
  const user       = payment.user;
  const eventTitle = payment.registration?.event?.title || payment.event?.title || 'the event';
  const amt        = fmtAmount(Math.abs(payment.amount || 0));
  const name       = user?.name || 'there';

  return [
    `💸 *Refund Processed*`,
    '',
    `Hi ${name},`,
    '',
    `A refund of *${amt}* for *${eventTitle}* has been processed.`,
    '',
    `Refunds may take a few business days to appear depending on your bank.`,
    '',
    `_${org.name}_ | ${org.email}`,
  ].join('\n');
}

// ─── Donation applied to a registration ────────────────────────────────────────
//
// Distinct from buildWAPayment: sent to the REGISTRANT when staff apply someone else's
// donation to their registration — anonymous (no donor name), and never "payment received"
// wording since they didn't pay anything themselves.

function buildWADonationAppliedToRegistrant(payment) {
  const org        = getOrg();
  const reg        = payment.registration;
  const eventTitle = reg?.event?.title || 'the event';
  const name       = reg?.user?.name || 'there';
  const amount     = fmtAmount(payment.amount);

  let balLine = '';
  if (reg) {
    const { computeRegistrationTotalDue } = require('./pricing');
    const totalDue  = computeRegistrationTotalDue(reg, payment.createdAt || new Date());
    const totalPaid = (reg.payments || []).reduce((s, p) => s + (p.amount || 0), 0);
    const balance   = Math.max(totalDue - totalPaid, 0);
    balLine = balance <= 0
      ? `\n✅ *Fully paid!* Your tickets have been sent.`
      : `\n*Remaining balance:* ${fmtAmount(balance)}\n_Pay the remainder at ${org.url} or at the door._`;
  }

  return [
    `🎁 *Donation Applied*`,
    '',
    `Hi ${name},`,
    '',
    `A donation of *${amount}* was applied to your registration for *${eventTitle}*.`,
    balLine,
    '',
    `_${org.name}_ | ${org.url}`,
  ].join('\n');
}

module.exports = {
  buildWARegistration,
  buildWAPayment,
  buildWARefund,
  buildWADonationAppliedToRegistrant,
  buildWALogin,
  buildWAWelcome,
  buildWAAccountClosed,
  buildWATicketCaption,
  buildWACheckIn,
};