'use strict';

/**
 * WhatsApp queue processor (#640 part D).
 *
 * Polls `whatsapp_queue` every 30s. For each pending row whose retry_count <
 * 3, builds the Meta template components from the stored message_data,
 * resolves the language code, and sends via whatsappService. Transient
 * failures bump retry_count; permanent failures mark the row 'failed'.
 *
 * Ported from filpgame/picpeak with the following changes:
 *   - Default language sourced from `app_settings.general_default_language`
 *     (matches our email-language resolution pattern) instead of a hardcoded
 *     `pt_BR`. Falls back to `en` then `en_US` if nothing is configured.
 *   - Cycle size + interval pulled from env vars so low-volume installs can
 *     dial back the poll frequency.
 *   - Exits gracefully when the `whatsapp` feature flag is off (no config
 *     polling, no queue queries).
 */

const { db } = require('../database/db');
const logger = require('../utils/logger');
const { sendWhatsAppMessage } = require('./whatsappService');

// IETF language tag (with hyphen or underscore) → Meta template language code.
// Meta template languages: https://developers.facebook.com/docs/whatsapp/business-management-api/message-templates/supported-languages
const LANGUAGE_MAP = {
  en:    'en_US', 'en-us': 'en_US', 'en_us': 'en_US',
  de:    'de_DE', 'de-de': 'de_DE', 'de_de': 'de_DE',
  pt:    'pt_BR', ptbr: 'pt_BR', 'pt-br': 'pt_BR', 'pt_br': 'pt_BR',
  ru:    'ru_RU', 'ru-ru': 'ru_RU', 'ru_ru': 'ru_RU',
  nl:    'nl_NL', 'nl-nl': 'nl_NL', 'nl_nl': 'nl_NL',
  fr:    'fr_FR', 'fr-fr': 'fr_FR', 'fr_fr': 'fr_FR',
  es:    'es_ES', 'es-es': 'es_ES', 'es_es': 'es_ES',
  it:    'it_IT', 'it-it': 'it_IT', 'it_it': 'it_IT',
  // Meta lists Arabic as a single code `ar` (no region variant). The common
  // BCP-47 region variants land on the same Meta code (#647).
  ar:    'ar', 'ar-sa': 'ar', 'ar_sa': 'ar', 'ar-eg': 'ar', 'ar_eg': 'ar',
  'ar-ar': 'ar', 'ar_ar': 'ar',
};

// Per-locale label embedded in the {{4}} password line. Meta templates only
// accept positional parameters in the body, so the "Password:" prefix has to
// be baked into the parameter itself rather than living in the template body.
const PASSWORD_LABELS = {
  pt_BR: '🔒 Senha',
  en_US: '🔒 Password',
  de_DE: '🔒 Passwort',
  ru_RU: '🔒 Пароль',
  nl_NL: '🔒 Wachtwoord',
  fr_FR: '🔒 Mot de passe',
  es_ES: '🔒 Contraseña',
  it_IT: '🔒 Password',
  ar:    '🔒 كلمة المرور',
};

const INTL_LOCALE_MAP = {
  pt_BR: 'pt-BR', en_US: 'en-US', de_DE: 'de-DE',
  ru_RU: 'ru-RU', nl_NL: 'nl-NL', fr_FR: 'fr-FR',
  es_ES: 'es-ES', it_IT: 'it-IT',
  // Pick a representative region for Arabic date formatting. Meta has no
  // region variant on the template code, but JS Intl needs one.
  ar:    'ar-SA',
};

const POLL_INTERVAL_MS = parseInt(process.env.WHATSAPP_QUEUE_POLL_MS || '30000', 10);
const CYCLE_BATCH_SIZE = parseInt(process.env.WHATSAPP_QUEUE_BATCH || '10', 10);
const MAX_RETRIES = 3;

let pollHandle = null;

/**
 * Resolve a Meta template language code from whatever's in the message_data
 * (admin-set per-event language) or the system default.
 *
 * Pass-through fallback (#647): if the admin types a code we don't have in
 * the map (e.g. `tr_TR` for Turkish, `zh_CN` for Chinese), but it matches
 * the Meta BCP-47 shape, we trust them and forward it as-is. Meta returns
 * template_not_found_in_language (132001) if the code doesn't match a
 * registered template, surfacing the typo back to the admin via the test
 * route's error response.
 */
function resolveLanguageCode(lang) {
  if (!lang) return null; // signal: caller should fall through to default
  const raw = String(lang).trim();
  if (!raw) return null;
  const normalised = raw.toLowerCase().replace(/-/g, '_');
  if (LANGUAGE_MAP[normalised]) return LANGUAGE_MAP[normalised];
  // Pass-through for valid-shape Meta codes the map doesn't enumerate.
  // Accept `xx` or `xx_YY` (case-insensitive on input); emit Meta's
  // canonical lowercase-language + uppercase-region form.
  const passthrough = /^([a-z]{2})(?:[_-]([a-z]{2}))?$/i.exec(raw);
  if (passthrough) {
    const [, langPart, regionPart] = passthrough;
    return regionPart ? `${langPart.toLowerCase()}_${regionPart.toUpperCase()}` : langPart.toLowerCase();
  }
  return null;
}

async function getSystemDefaultLanguageCode() {
  try {
    const row = await db('app_settings')
      .where('setting_key', 'general_default_language')
      .first();
    if (row && row.setting_value) {
      let lang = row.setting_value;
      try { lang = JSON.parse(lang); } catch (_) { /* not JSON, use raw */ }
      const resolved = resolveLanguageCode(typeof lang === 'string' ? lang.trim() : '');
      if (resolved) return resolved;
    }
  } catch (error) {
    logger.debug('whatsappProcessor: general_default_language read failed', { error: error.message });
  }
  return 'en_US';
}

function formatDate(raw, metaLangCode) {
  if (!raw) return '';
  try {
    const d = new Date(raw);
    if (Number.isNaN(d.getTime())) return '';
    const intlLocale = INTL_LOCALE_MAP[metaLangCode] || 'en-US';
    return d.toLocaleDateString(intlLocale, { day: '2-digit', month: '2-digit', year: 'numeric' });
  } catch {
    return '';
  }
}

// Default slot order — matches the operator-registered `gallery_ready`
// template's 5-parameter shape and preserves pre-#647 behaviour for installs
// that haven't configured `template_params`.
const DEFAULT_TEMPLATE_PARAMS = ['customer_name', 'event_name', 'gallery_link', 'password_line', 'expiry_date'];
const KNOWN_TEMPLATE_PARAMS = new Set(DEFAULT_TEMPLATE_PARAMS);

/**
 * Parse `whatsapp_configs.template_params` (JSON array string) into a
 * sanitized slot list. Unknown / non-string / duplicated keys are dropped;
 * empty / malformed input falls back to the default 5-slot shape so the
 * legacy `gallery_ready` template keeps working.
 */
function parseTemplateParams(raw) {
  if (!raw) return DEFAULT_TEMPLATE_PARAMS;
  try {
    const parsed = typeof raw === 'string' ? JSON.parse(raw) : raw;
    if (!Array.isArray(parsed)) return DEFAULT_TEMPLATE_PARAMS;
    const seen = new Set();
    const out = [];
    for (const k of parsed) {
      if (typeof k !== 'string') continue;
      if (!KNOWN_TEMPLATE_PARAMS.has(k)) continue;
      if (seen.has(k)) continue;
      seen.add(k);
      out.push(k);
    }
    return out.length > 0 ? out : DEFAULT_TEMPLATE_PARAMS;
  } catch (_) {
    return DEFAULT_TEMPLATE_PARAMS;
  }
}

/**
 * Build the positional body components for the configured template. The
 * `params` list controls which built-in values are emitted, and in what
 * order — so an admin who registered a 2-parameter Meta template with
 * `{{1}} = event_name, {{2}} = gallery_link` (e.g. #647) configures
 * `template_params: ["event_name","gallery_link"]` and gets exactly those
 * two positional values per send.
 *
 * Known slot keys: customer_name, event_name, gallery_link, password_line,
 * expiry_date. Anything else is filtered out by parseTemplateParams.
 */
function buildComponents(data, metaLang, params = DEFAULT_TEMPLATE_PARAMS) {
  const label = PASSWORD_LABELS[metaLang] || PASSWORD_LABELS.en_US;
  const hasRealPassword = data.gallery_password
    && data.gallery_password !== 'No password required'
    && data.gallery_password !== '(set at creation)';
  const passwordLine = hasRealPassword ? `${label}: ${data.gallery_password}` : '';
  const expiryLine = formatDate(data.expiry_date, metaLang);

  const valueFor = (key) => {
    switch (key) {
    case 'customer_name': return data.customer_name || '';
    case 'event_name':    return data.event_name || '';
    case 'gallery_link':  return data.gallery_link || '';
    case 'password_line': return passwordLine;
    case 'expiry_date':   return expiryLine;
    default:              return '';
    }
  };

  return params.map(valueFor);
}

async function getWhatsAppConfig() {
  try {
    return await db('whatsapp_configs').first();
  } catch (error) {
    logger.debug('whatsappProcessor: failed to read whatsapp_configs', { error: error.message });
    return null;
  }
}

/**
 * Enqueue a WhatsApp message. Safe to call without checking the feature flag
 * upstream — the processor's poll loop is the gate, so a queued message just
 * sits idle if the flag is off. Routes still SHOULD check the flag before
 * calling so the customer-facing error path (silent feature disabled vs. real
 * queue failure) stays distinguishable.
 */
async function queueWhatsapp(eventId, recipientPhone, messageType, messageData) {
  try {
    await db('whatsapp_queue').insert({
      event_id: eventId,
      recipient_phone: recipientPhone,
      message_type: messageType,
      message_data: JSON.stringify(messageData || {}),
      status: 'pending',
      retry_count: 0,
      created_at: new Date(),
    });
    logger.info(`WhatsApp queued: ${messageType} → ${recipientPhone}`);
  } catch (error) {
    logger.error('Error queueing WhatsApp message:', error);
    throw error;
  }
}

/**
 * One poll cycle. Reads up to CYCLE_BATCH_SIZE pending rows, sends each, and
 * updates retry/error/status fields. Wraps everything in defensive try/catch
 * so a single bad row can't stall the rest of the batch.
 */
async function processWhatsAppQueue() {
  let config;
  try {
    config = await getWhatsAppConfig();
  } catch (e) {
    // Tables not migrated yet — just bail.
    return;
  }
  if (!config || !config.enabled || !config.phone_number_id || !config.access_token) return;

  // Priority order for the *default* (when message_data.language is null):
  //   1. config.template_language — admin-pinned to match their Meta-registered
  //      template (#647). This is the only way to send Arabic/Chinese/etc.
  //      templates correctly, since general_default_language is the UI
  //      language not the template's.
  //   2. general_default_language — system fallback for installs that haven't
  //      pinned a template_language.
  //   3. en_US — hardcoded last resort.
  const configLanguage = resolveLanguageCode(config.template_language);
  const defaultLanguage = configLanguage || await getSystemDefaultLanguageCode();
  const params = parseTemplateParams(config.template_params);

  let pending;
  try {
    pending = await db('whatsapp_queue')
      .where('status', 'pending')
      .andWhere('retry_count', '<', MAX_RETRIES)
      .orderBy('created_at', 'asc')
      .limit(CYCLE_BATCH_SIZE);
  } catch (error) {
    logger.error('WhatsApp queue: failed to query pending rows', { error: error.message });
    return;
  }

  if (pending.length === 0) return;

  logger.info(`WhatsApp queue: processing ${pending.length} message(s)`);

  for (const item of pending) {
    try {
      const data = typeof item.message_data === 'string'
        ? JSON.parse(item.message_data || '{}')
        : item.message_data || {};

      const requestedLang = resolveLanguageCode(data.language);
      const metaLang = requestedLang || defaultLanguage;
      const components = buildComponents(data, metaLang, params);

      await sendWhatsAppMessage(item.recipient_phone, config, metaLang, components);

      await db('whatsapp_queue')
        .where('id', item.id)
        .update({ status: 'sent', sent_at: new Date(), error_message: null });
    } catch (error) {
      const newRetryCount = (item.retry_count || 0) + 1;
      const exhausted = newRetryCount >= MAX_RETRIES;
      await db('whatsapp_queue')
        .where('id', item.id)
        .update({
          retry_count: newRetryCount,
          error_message: String(error.message).slice(0, 2000),
          ...(exhausted ? { status: 'failed' } : {}),
        });
      logger.error(
        `WhatsApp message ${item.id} ${exhausted ? 'failed (permanent)' : `retry ${newRetryCount}/${MAX_RETRIES}`}:`,
        error.message,
      );
    }
  }
}

function startWhatsAppQueueProcessor() {
  if (pollHandle) {
    logger.info('WhatsApp queue processor already running — skipping start');
    return;
  }
  // Fire once shortly after boot so the first message in a fresh install
  // doesn't wait the full poll interval.
  setTimeout(() => {
    processWhatsAppQueue().catch((e) => logger.error('WhatsApp queue initial run failed', e));
  }, 5000);
  pollHandle = setInterval(() => {
    processWhatsAppQueue().catch((e) => logger.error('WhatsApp queue cycle failed', e));
  }, POLL_INTERVAL_MS);
  logger.info(`WhatsApp queue processor started (poll every ${POLL_INTERVAL_MS}ms)`);
}

function stopWhatsAppQueueProcessor() {
  if (pollHandle) {
    clearInterval(pollHandle);
    pollHandle = null;
    logger.info('WhatsApp queue processor stopped');
  }
}

module.exports = {
  queueWhatsapp,
  processWhatsAppQueue,
  startWhatsAppQueueProcessor,
  stopWhatsAppQueueProcessor,
  getWhatsAppConfig,
  // Exported for the admin route's test send + unit tests (#647 follow-up).
  buildComponents,
  parseTemplateParams,
  DEFAULT_TEMPLATE_PARAMS,
};