/**
 * Gmail service – OAuth client, send reply, send ticket-closed email.
 */
const { google } = require('googleapis');
const { CONFIG } = require('../config');
const { extractRawEmail, escapeHtml } = require('../utils');
const { getStaffSignatureBlocks } = require('./staffSignature');
const { logError } = require('./debugLog');
const { readEnvFile } = require('./configPersistence');

function sanitizeHeaderValue(v) { return String(v || '').replace(/[\r\n]+/g, ' ').trim(); }
const EMAIL_RE = /^[^@\s]+@[^@\s]+$/;

function getGmailClient() {
  const auth = new google.auth.OAuth2(
    process.env.GOOGLE_CLIENT_ID,
    process.env.GOOGLE_CLIENT_SECRET
  );
  auth.setCredentials({ refresh_token: CONFIG.REFRESH_TOKEN });
  return google.gmail({ version: 'v1', auth });
}

/**
 * Re-read REFRESH_TOKEN from .env, update in-memory config, and probe Google.
 * Used by the internal /gmail/reload endpoint so the weekly reauth chore does
 * not require a full container restart.
 *
 * Throws if the env file is missing the token, or if the probe call (getProfile)
 * fails — the caller surfaces the error so the UI can see why.
 *
 * @returns {Promise<{emailAddress: string}>}
 */
async function reloadGmailClient() {
  const envMap = readEnvFile();
  const newToken = envMap.get('REFRESH_TOKEN');
  if (!newToken) {
    const err = new Error('REFRESH_TOKEN not set in .env');
    err.code = 'ENOTOKEN';
    throw err;
  }
  process.env.REFRESH_TOKEN = newToken;
  CONFIG.REFRESH_TOKEN = newToken;
  const gmail = getGmailClient();
  const profile = await gmail.users.getProfile({ userId: 'me' });
  return { emailAddress: profile.data.emailAddress };
}

async function sendTicketClosedEmail(ticket, discordDisplayName) {
  try {
    const gmail = getGmailClient();

    // Send to the ticket sender (customer), not derived from thread (which can be support)
    const recipientEmail = sanitizeHeaderValue(extractRawEmail(ticket.senderEmail || '')).toLowerCase();
    if (!recipientEmail || recipientEmail === CONFIG.MY_EMAIL) return;
    if (!EMAIL_RE.test(recipientEmail)) {
      logError('sendTicketClosedEmail: invalid recipient', new Error(`Rejected: ${recipientEmail}`)).catch(() => {});
      return;
    }

    let subjectHeader = ticket.subject || 'Support';
    let msgId = null;
    try {
      const thread = await gmail.users.threads.get({
        userId: 'me',
        id: ticket.gmailThreadId
      });
      const messages = thread.data.messages || [];
      const lastMsg = [...messages].reverse()[0];
      if (lastMsg?.payload?.headers) {
        const subj = lastMsg.payload.headers.find(h => h.name === 'Subject')?.value;
        if (subj) subjectHeader = subj;
        msgId = sanitizeHeaderValue(lastMsg.payload.headers.find(h => h.name === 'Message-ID')?.value);
      }
    } catch (_) {
      /* use ticket.subject and no In-Reply-To if thread fetch fails */
    }

    const finalSubject = sanitizeHeaderValue(`${CONFIG.TICKET_CLOSE_SUBJECT_PREFIX} ${subjectHeader}`);
    const utf8Subject = `=?utf-8?B?${Buffer.from(
      finalSubject
    ).toString('base64')}?=`;

    const serverDisplayName = escapeHtml(discordDisplayName || CONFIG.SUPPORT_NAME || 'Support');
    const safeLogoUrl = escapeHtml(CONFIG.LOGO_URL || '');
    const safeSignature = escapeHtml(CONFIG.SIGNATURE || '').replace(/\n/g, '<br>');
    const safeCloseMessage = escapeHtml(CONFIG.TICKET_CLOSE_MESSAGE || '').replace(/\n/g, '<br>');
    const safeCloseSignature = escapeHtml(CONFIG.TICKET_CLOSE_SIGNATURE || '').replace(/\n/g, '<br>');
    const htmlBody = `
      <div style="font-family: sans-serif; font-size: 14px; color: #333;">
        <p><strong>From:</strong> ${serverDisplayName} on Discord</p>
        <p><strong>Message:</strong></p>
        <p>${safeCloseMessage}</p>
        <p style="margin-top: 16px;">${safeCloseSignature}</p>
        <hr style="border:none; border-top:1px solid #ddd; margin:20px 0;">
        <table border="0" cellpadding="0" cellspacing="0">
          <tr>
            <td style="padding-right: 12px;">
              ${safeLogoUrl ? `<img src="${safeLogoUrl}" width="65">` : ''}
            </td>
            <td style="border-left: 1px solid #ddd; padding-left: 12px;">
              <p style="margin: 0; font-weight: bold;">${serverDisplayName}</p>
              <div style="color: #666; font-size: 12px;">${safeSignature}</div>
            </td>
          </tr>
        </table>
      </div>`;

    const rawHeaders = [
      `From: ${sanitizeHeaderValue(CONFIG.MY_EMAIL)}`,
      `To: ${recipientEmail}`,
      `Subject: ${utf8Subject}`,
      msgId ? `In-Reply-To: ${msgId}` : '',
      msgId ? `References: ${msgId}` : '',
      'MIME-Version: 1.0',
      'Content-Type: text/html; charset="UTF-8"',
      '',
      htmlBody
    ].filter(Boolean);

    const raw = Buffer.from(rawHeaders.join('\r\n'))
      .toString('base64')
      .replace(/\+/g, '-')
      .replace(/\//g, '_')
      .replace(/=+$/, '');

    await gmail.users.messages.send({
      userId: 'me',
      requestBody: { raw, threadId: ticket.gmailThreadId }
    });
  } catch (err) {
    console.error('Ticket closed email error:', err);
  }
}

// StaffSignature model is registered in models.js; re-import here for use in this file
const { mongoose } = require('../db-connection');
const StaffSignature = mongoose.model('StaffSignature');

/**
 * Send a notification email in the ticket thread (e.g. escalation, high-priority).
 * @param {Object} ticket - Ticket with gmailThreadId, senderEmail, subject
 * @param {string} subjectLine - Subject line (e.g. "Ticket escalated" or "Priority updated")
 * @param {string} messageBody - Plain or HTML message body
 * @param {string} [fromLabel] - Label for "From" (e.g. "Support on Discord")
 * @param {string} [userId] - Discord user ID for signature (optional)
 */
async function sendTicketNotificationEmail(ticket, subjectLine, messageBody, fromLabel, userId = null) {
  try {
    const gmail = getGmailClient();
    const recipientEmail = sanitizeHeaderValue(extractRawEmail(ticket.senderEmail || '')).toLowerCase();
    if (!recipientEmail || recipientEmail === CONFIG.MY_EMAIL) return;
    if (!EMAIL_RE.test(recipientEmail)) {
      logError('sendTicketNotificationEmail: invalid recipient', new Error(`Rejected: ${recipientEmail}`)).catch(() => {});
      return;
    }

    let subjectHeader = ticket.subject || 'Support';
    let msgId = null;
    try {
      const thread = await gmail.users.threads.get({
        userId: 'me',
        id: ticket.gmailThreadId
      });
      const messages = thread.data.messages || [];
      const lastMsg = [...messages].reverse()[0];
      if (lastMsg?.payload?.headers) {
        const subj = lastMsg.payload.headers.find(h => h.name === 'Subject')?.value;
        if (subj) subjectHeader = subj;
        msgId = sanitizeHeaderValue(lastMsg.payload.headers.find(h => h.name === 'Message-ID')?.value);
      }
    } catch (_) {}

    const finalSubject = sanitizeHeaderValue(subjectLine || subjectHeader);
    const utf8Subject = `=?utf-8?B?${Buffer.from(finalSubject).toString('base64')}?=`;
    const label = escapeHtml(fromLabel || CONFIG.SUPPORT_NAME || 'Support');
    const safeBody = escapeHtml(messageBody || '').replace(/\n/g, '<br>');
    const safeLogoUrl = escapeHtml(CONFIG.LOGO_URL || '');
    
    // Get staff signature if userId provided
    let signatureBlocks = { text: '', html: '' };
    if (userId) {
      signatureBlocks = await getStaffSignatureBlocks(userId);
    }
    
  const safeSignature = escapeHtml(CONFIG.SIGNATURE || '').replace(/\n/g, '<br>');
  const serverDisplayName = label;
  const safeCloseMessage = safeBody;
  const safeCloseSignature = escapeHtml(CONFIG.TICKET_CLOSE_SIGNATURE || '').replace(/\n/g, '<br>');
  const htmlBody = `
    <div style="font-family: sans-serif; font-size: 14px; color: #333;">
      <p><strong>From:</strong> ${serverDisplayName} on Discord</p>
      <p><strong>Message:</strong></p>
      <p>${safeCloseMessage}</p>
      <p style="margin-top: 16px;">${safeCloseSignature}</p>
      <hr style="border:none; border-top:1px solid #ddd; margin:20px 0;">
      <table border="0" cellpadding="0" cellspacing="0">
        <tr>
          <td style="padding-right: 12px;">
            ${safeLogoUrl ? `<img src="${safeLogoUrl}" width="65">` : ''}
          </td>
          <td style="border-left: 1px solid #ddd; padding-left: 12px;">
            <p style="margin: 0; font-weight: bold;">${serverDisplayName}</p>
            <div style="color: #666; font-size: 12px;">${safeSignature}</div>
          </td>
        </tr>
      </table>
    </div>`;

    const rawHeaders = [
      `From: ${sanitizeHeaderValue(CONFIG.MY_EMAIL)}`,
      `To: ${recipientEmail}`,
      `Subject: ${utf8Subject}`,
      msgId ? `In-Reply-To: ${msgId}` : '',
      msgId ? `References: ${msgId}` : '',
      'MIME-Version: 1.0',
      'Content-Type: text/html; charset="UTF-8"',
      '',
      htmlBody
    ].filter(Boolean);

    const raw = Buffer.from(rawHeaders.join('\r\n'))
      .toString('base64')
      .replace(/\+/g, '-')
      .replace(/\//g, '_')
      .replace(/=+$/, '');

    await gmail.users.messages.send({
      userId: 'me',
      requestBody: { raw, threadId: ticket.gmailThreadId }
    });
  } catch (err) {
    console.error('Ticket notification email error:', err);
  }
}

/**
 * Send a Gmail reply to a ticket
 * @param {string} threadId - Gmail thread ID
 * @param {string} replyText - Reply text
 * @param {string} recipientEmail - Recipient email
 * @param {string} subject - Subject line
 * @param {string} messageId - Message ID (optional)
 * @param {string} userId - Discord user ID for optional personal valediction/tagline (optional)
 */
async function sendGmailReply(
  threadId,
  replyText,
  recipientEmail,
  subject,
  messageId,
  userId = null
) {
  const gmail = getGmailClient();

  const safeRecipient = sanitizeHeaderValue(extractRawEmail(recipientEmail || '')).toLowerCase();
  if (!EMAIL_RE.test(safeRecipient)) {
    logError('sendGmailReply: invalid recipient', new Error(`Rejected: ${safeRecipient}`)).catch(() => {});
    return null;
  }
  const safeMessageId = sanitizeHeaderValue(messageId);
  const safeSubject = sanitizeHeaderValue(`Re: ${subject}`);

  const utf8Subject = `=?utf-8?B?${Buffer.from(
    safeSubject
  ).toString('base64')}?=`;
  const safeLogoUrl = escapeHtml(CONFIG.LOGO_URL || '');

  let signatureBlocks = { text: '', html: '' };
  if (userId) {
    signatureBlocks = await getStaffSignatureBlocks(userId);
  }
  // signatureBlocks.html must arrive pre-escaped; do not inject raw HTML here.
  const safeStaffSigHtml = signatureBlocks.html ? signatureBlocks.html.replace(/\n/g, '<br>') : '';
  const safeStaffSigText = signatureBlocks.text;

  const htmlBody = `
    <div style="font-family: sans-serif; font-size: 14px; color: #333;">
      <p>${escapeHtml(replyText).replace(/\n/g, '<br>')}</p>
      ${safeStaffSigHtml ? `<p style="margin: 10px 0;">${safeStaffSigHtml}</p>` : ''}
      <div>
        ${safeLogoUrl ? `<img src="${safeLogoUrl}" width="65" alt="Indifferent Broccoli"><br>` : ''}
        Indifferent Broccoli Support<br>
        <a href="https://indifferentbroccoli.com/">https://indifferentbroccoli.com/</a><br>
        Join us on <a href="https://discord.gg/2vmfrrtvJY">Discord</a><br>
        <br>
        <em>"We eat lag for breakfast. Whatever."</em>
      </div>
    </div>`;

  const boundary = '000000000000' + Date.now().toString(16);

  const plainBody = [];
  plainBody.push(replyText);
  if (safeStaffSigText) {
    plainBody.push('');
    plainBody.push(safeStaffSigText);
  }
  plainBody.push('');
  plainBody.push('Indifferent Broccoli Support');
  plainBody.push('https://indifferentbroccoli.com/');
  plainBody.push('Join us on Discord: https://discord.gg/2vmfrrtvJY');
  plainBody.push('');
  plainBody.push('"We eat lag for breakfast. Whatever."');

  const raw = Buffer.from([
    `From: ${sanitizeHeaderValue(CONFIG.MY_EMAIL)}`,
    `To: ${safeRecipient}`,
    `Subject: ${utf8Subject}`,
    safeMessageId ? `In-Reply-To: ${safeMessageId}` : '',
    safeMessageId ? `References: ${safeMessageId}` : '',
    'MIME-Version: 1.0',
    'Content-Type: multipart/alternative; boundary="' + boundary + '"',
    '',
    '--' + boundary,
    'Content-Type: text/plain; charset="UTF-8"',
    '',
    ...plainBody,
    '',
    '--' + boundary,
    'Content-Type: text/html; charset="UTF-8"',
    '',
    htmlBody,
    '',
    '--' + boundary + '--'
  ].join('\r\n'))
    .toString('base64')
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
    .replace(/=+$/, '');

  await gmail.users.messages.send({
    userId: 'me',
    requestBody: { raw, threadId }
  });
}

module.exports = {
  getGmailClient,
  reloadGmailClient,
  sendGmailReply,
  sendTicketClosedEmail,
  sendTicketNotificationEmail
};