/**
 * Ticket database helpers – counters, rename, limits, auto-close,
 * reminders, auto-unclaim, channel creation.
 */
const { ChannelType } = require('discord.js');
const { mongoose, withRetry } = require('../db-connection');
const { CONFIG } = require('../config');
const { enqueueSend, enqueueDelete } = require('./channelQueue');

const Ticket = mongoose.model('Ticket');
const TicketCounter = mongoose.model('TicketCounter');

// --- TICKET NUMBER ---

async function getNextTicketNumber(senderEmail) {
  const senderLocal = senderEmail.split('@')[0].toLowerCase();
  const counter = await TicketCounter.findOneAndUpdate(
    { senderLocal },
    { $inc: { counter: 1 } },
    { upsert: true, new: true, setDefaultsOnInsert: true }
  );
  return { local: senderLocal, number: counter.counter };
}

// --- RENAME + NAMING ---
// Renames flow through utils/renamer.js (RENAMER_BOT secondary token),
// which has its own Discord rate-limit bucket. We no longer gate on the
// primary bot's 2/10min per-channel budget here; 429s from the secondary
// bot surface via utils/renamer.js instead.

function getSenderLocal(senderEmail) {
  return (senderEmail || 'unknown').split('@')[0].toLowerCase();
}

function toDiscordSafeName(str) {
  return str
    .toLowerCase()
    .replace(/\s+/g, '-')
    .replace(/[^\p{L}\p{N}\p{Emoji_Presentation}-]/gu, '')
    .replace(/-{2,}/g, '-')
    .replace(/^-+|-+$/g, '')
    .slice(0, 100);
}

/**
 * Resolve a human-friendly creator nickname for channel naming.
 * Discord tickets: guild member displayName. Email tickets: senderLocal.
 * @param {import('discord.js').Guild} guild
 * @param {object} ticket
 * @returns {Promise<string>}
 */
async function resolveCreatorNickname(guild, ticket) {
  if (ticket.gmailThreadId.startsWith('discord-')) {
    // Prefer ticket.creatorId (stored on creation). Legacy fallback parses the
    // tail segment, which is correct for discord-${ts}-${userId} but returns
    // the message ID for discord-msg-${ts}-${msgId} — skip the parse for those.
    const creatorUserId = ticket.creatorId
      || (ticket.gmailThreadId.startsWith('discord-msg-') ? null : ticket.gmailThreadId.split('-').pop());
    if (!creatorUserId) return getSenderLocal(ticket.senderEmail);
    try {
      const member = await guild.members.fetch(creatorUserId);
      return member.displayName;
    } catch {
      return getSenderLocal(ticket.senderEmail);
    }
  }
  return getSenderLocal(ticket.senderEmail);
}

/**
 * Build a channel name from ticket state.
 * @param {'unclaimed'|'claimed'|'escalated'|'escalated-claimed'} state
 * @param {object} ticket
 * @param {string} creatorNickname - pre-resolved via resolveCreatorNickname
 * @param {string} [claimerEmoji] - required for claimed / escalated-claimed
 * @returns {string}
 */
function makeTicketName(state, ticket, creatorNickname, claimerEmoji) {
  const num = ticket.ticketNumber || 1;
  switch (state) {
    case 'claimed':
      return toDiscordSafeName(`${claimerEmoji}-${creatorNickname}-${num}`);
    case 'escalated':
      return toDiscordSafeName(`escalated-${creatorNickname}-${num}`);
    case 'escalated-claimed':
      return toDiscordSafeName(`e-${claimerEmoji}-${creatorNickname}-${num}`);
    case 'unclaimed':
    default:
      return toDiscordSafeName(`unclaimed-${creatorNickname}-${num}`);
  }
}

// --- RATE LIMIT (per-user ticket creation) ---

const ticketCreationByUser = new Map(); // userId -> { count, resetAt }

const TICKET_CREATION_SWEEP_TTL_MS = 48 * 60 * 60 * 1000;
const TICKET_CREATION_SWEEP_INTERVAL_MS = 6 * 60 * 60 * 1000;

function sweepTicketCreationByUser(now = Date.now()) {
  // An entry is stale when its window has been expired long enough that no
  // legitimate rate-limit decision would still consult it. resetAt is a future
  // ms timestamp when the window ends; cutoff is 48h past that.
  const cutoff = now - TICKET_CREATION_SWEEP_TTL_MS;
  for (const [key, entry] of ticketCreationByUser.entries()) {
    if ((entry?.resetAt ?? 0) < cutoff) ticketCreationByUser.delete(key);
  }
}

function startTicketsSweeps(trackInterval) {
  const handle = setInterval(() => sweepTicketCreationByUser(), TICKET_CREATION_SWEEP_INTERVAL_MS);
  if (typeof handle.unref === 'function') handle.unref();
  if (typeof trackInterval === 'function') trackInterval(handle);
  return handle;
}

/**
 * Check if the user can create a ticket (rate limit). If allowed, consumes one slot.
 * @param {string} userId - Discord user ID
 * @returns {{ allowed: boolean, retryAfterMs?: number }}
 */
function checkTicketCreationRateLimit(userId) {
  const limit = CONFIG.RATE_LIMIT_TICKETS_PER_USER;
  const windowMs = (CONFIG.RATE_LIMIT_WINDOW_MINUTES || 60) * 60 * 1000;
  if (!limit || limit <= 0) return { allowed: true };

  const now = Date.now();
  let entry = ticketCreationByUser.get(userId);
  if (!entry || now >= entry.resetAt) {
    entry = { count: 1, resetAt: now + windowMs };
    ticketCreationByUser.set(userId, entry);
    return { allowed: true };
  }
  if (entry.count >= limit) {
    return { allowed: false, retryAfterMs: entry.resetAt - now };
  }
  entry.count++;
  return { allowed: true };
}

// --- CHANNEL CREATION (overflow: Discord limit 50 channels per category) ---

const CHANNELS_PER_CATEGORY_LIMIT = 50;

function escapeCategoryNameForRegex(name) {
  return String(name).replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
}

function countChannelsInCategory(guild, categoryId) {
  return guild.channels.cache.filter(c => c.parentId === categoryId).size;
}

/**
 * Resolve or create a ticket category with dynamic overflow (Discord max 50 channels per category).
 * @param {import('discord.js').Guild} guild
 * @param {string} primaryCategoryId
 * @param {string} categoryName Display base name (primary category should match; overflows are "(Overflow N)")
 * @returns {Promise<string>}
 */
async function getOrCreateTicketCategory(guild, primaryCategoryId, categoryName) {
  if (!guild) {
    throw new Error('getOrCreateTicketCategory: guild is required');
  }
  if (!primaryCategoryId || !String(primaryCategoryId).trim()) {
    throw new Error('getOrCreateTicketCategory: primaryCategoryId is required');
  }
  try {
    let primary = guild.channels.cache.get(primaryCategoryId);
    if (!primary) {
      primary = await guild.channels.fetch(primaryCategoryId).catch(() => null);
    }
    if (!primary || primary.type !== ChannelType.GuildCategory) {
      throw new Error(`getOrCreateTicketCategory: primary category ${primaryCategoryId} not found or not a category`);
    }

    const escaped = escapeCategoryNameForRegex(categoryName);
    const overflowRe = new RegExp(`^${escaped} \\(Overflow (\\d+)\\)$`);

    const overflowMatches = [];
    for (const ch of guild.channels.cache.values()) {
      if (!ch || ch.type !== ChannelType.GuildCategory) continue;
      if (ch.id === primaryCategoryId) continue;
      const m = ch.name.match(overflowRe);
      if (m) overflowMatches.push({ ch, n: parseInt(m[1], 10) });
    }
    overflowMatches.sort((a, b) => a.n - b.n);

    const existingCategories = [primary, ...overflowMatches.map(x => x.ch)];

    for (const cat of existingCategories) {
      if (countChannelsInCategory(guild, cat.id) < CHANNELS_PER_CATEGORY_LIMIT) {
        return cat.id;
      }
    }

    const highestN = overflowMatches.length > 0 ? Math.max(...overflowMatches.map(x => x.n)) : 0;
    const nextN = highestN + 1;
    const newName = `${categoryName} (Overflow ${nextN})`;
    const lastCat = existingCategories[existingCategories.length - 1];
    const position = (lastCat?.rawPosition ?? lastCat?.position ?? 0) + 1;

    let newCat;
    try {
      newCat = await guild.channels.create({
        name: newName,
        type: ChannelType.GuildCategory,
        position
      });
    } catch (createErr) {
      console.error('getOrCreateTicketCategory: failed to create overflow category:', createErr);
      throw createErr;
    }
    return newCat.id;
  } catch (err) {
    console.error('getOrCreateTicketCategory:', err);
    const fallback = guild.channels.cache.get(primaryCategoryId);
    if (fallback?.type === ChannelType.GuildCategory) {
      return primaryCategoryId;
    }
    throw err;
  }
}

/**
 * Delete an overflow category if it is empty and its name matches "${categoryName} (Overflow N)".
 * Never deletes the primary category (exact name match).
 * @param {import('discord.js').Guild} guild
 * @param {string} categoryId
 * @param {string} categoryName
 */
async function cleanupEmptyOverflowCategory(guild, categoryId, categoryName) {
  try {
    if (!guild || !categoryId) return;
    const cached = guild.channels.cache.filter(c => c.parentId === categoryId);
    if (cached.size !== 0) return;

    let cat = guild.channels.cache.get(categoryId);
    if (!cat) {
      cat = await guild.channels.fetch(categoryId).catch(() => null);
    }
    if (!cat || cat.type !== ChannelType.GuildCategory) return;
    if (cat.name === categoryName) return;

    const escaped = escapeCategoryNameForRegex(categoryName);
    const overflowRe = new RegExp(`^${escaped} \\(Overflow \\d+\\)$`);
    if (!overflowRe.test(cat.name)) return;

    await cat.delete().catch(deleteErr => {
      console.error('cleanupEmptyOverflowCategory: delete failed:', deleteErr);
    });
  } catch (err) {
    console.error('cleanupEmptyOverflowCategory:', err);
  }
}

// --- LIMITS & PERMISSIONS ---

async function checkTicketLimits(senderEmail) {
  if (!CONFIG.GLOBAL_TICKET_LIMIT) return { ok: true };

  const currentCount = await Ticket.countDocuments({ senderEmail, status: 'open' });
  if (currentCount >= CONFIG.GLOBAL_TICKET_LIMIT) {
    return {
      ok: false,
      reason: `You have reached the maximum limit of ${CONFIG.GLOBAL_TICKET_LIMIT} open tickets.`
    };
  }

  return { ok: true };
}

// --- ACTIVITY ---

async function updateTicketActivity(gmailThreadId) {
  await Ticket.updateOne(
    { gmailThreadId },
    { $set: { lastActivity: new Date() } }
  );
}

// --- SCHEDULED CHECKS ---
// These accept `client` and optionally `sendTicketClosedEmail` to avoid circular deps.

async function checkAutoClose(client, sendTicketClosedEmail) {
  if (!CONFIG.AUTO_CLOSE_ENABLED) return;

  const cutoffTime = new Date(Date.now() - (CONFIG.AUTO_CLOSE_AFTER_HOURS * 60 * 60 * 1000));
  // Bounded per-tick so a huge backlog drains across successive hourly runs.
  const staleTickets = await withRetry(() => Ticket.find({
    status: 'open',
    lastActivity: { $lt: cutoffTime, $ne: null }
  }).sort({ createdAt: 1 }).limit(500).lean());

  for (const ticket of staleTickets) {
    try {
      const guild = client.guilds.cache.first();
      if (!guild) continue;

      const channel = await guild.channels.fetch(ticket.discordThreadId).catch(() => null);
      if (channel) {
        await enqueueSend(channel, CONFIG.DISCORD_AUTO_CLOSE_MESSAGE);

        // Persist pendingDelete BEFORE the delay so a shutdown mid-delay can be
        // resumed on boot via resumePendingDeletes(). Cleared after enqueueDelete
        // resolves; if the doc is gone the unset is a no-op.
        await withRetry(() => Ticket.updateOne(
          { gmailThreadId: ticket.gmailThreadId },
          { $set: { status: 'closed', pendingDelete: true } }
        ));

        await sendTicketClosedEmail(ticket, 'Auto-Close System', null);

        // Lazy require — broccolini-discord re-exports trackTimeout; cycle-safe.
        const { trackTimeout } = require('../broccolini-discord');
        trackTimeout(setTimeout(() => {
          enqueueDelete(channel).then(() => {
            withRetry(() => Ticket.updateOne(
              { gmailThreadId: ticket.gmailThreadId },
              { $unset: { pendingDelete: '' } }
            )).catch(() => {});
          }).catch(() => {});
        }, 5000));
      }
    } catch (error) {
      console.error(`Auto-close error for ticket ${ticket.gmailThreadId}:`, error);
    }
  }
}

async function checkAutoUnclaim(client) {
  if (!CONFIG.AUTO_UNCLAIM_ENABLED) return;

  const unclaimTime = new Date(Date.now() - (CONFIG.AUTO_UNCLAIM_AFTER_HOURS * 60 * 60 * 1000));
  const staleClaimedTickets = await withRetry(() => Ticket.find({
    status: 'open',
    claimedBy: { $ne: null },
    lastActivity: { $lt: unclaimTime, $ne: null }
  }).lean());

  for (const ticket of staleClaimedTickets) {
    try {
      const guild = client.guilds.cache.first();
      if (!guild) continue;

      const channel = await guild.channels.fetch(ticket.discordThreadId).catch(() => null);
      if (channel) {
        await withRetry(() => Ticket.updateOne(
          { gmailThreadId: ticket.gmailThreadId },
          { $set: { claimedBy: null } }
        ));

        await enqueueSend(channel,
          `This ticket has been auto-unclaimed due to inactivity (${CONFIG.AUTO_UNCLAIM_AFTER_HOURS} hours).`
        );

        console.log(`Auto-unclaimed ticket ${ticket.gmailThreadId}`);
      }
    } catch (error) {
      console.error(`Auto-unclaim error for ticket ${ticket.gmailThreadId}:`, error);
    }
  }
}

async function reconcileDeletedTicketChannels(client) {
  const guild = client.guilds.cache.get(CONFIG.DISCORD_GUILD_ID) || client.guilds.cache.first();
  if (!guild) return;

  // Bounded per-tick; a larger backlog drains in subsequent hourly runs.
  const openTickets = await Ticket.find({
    status: 'open',
    discordThreadId: { $ne: null }
  }).sort({ createdAt: 1 }).limit(500).lean();

  for (const ticket of openTickets) {
    try {
      let channel = guild.channels.cache.get(ticket.discordThreadId);
      if (!channel) {
        channel = await guild.channels.fetch(ticket.discordThreadId).catch(() => null);
      }
      if (!channel) {
        await Ticket.updateOne(
          { gmailThreadId: ticket.gmailThreadId },
          { $set: { status: 'closed', discordThreadId: null } }
        );
      }
    } catch (err) {
      console.error(`reconcileDeletedTicketChannels error for ${ticket.gmailThreadId}:`, err);
    }
  }
}

/**
 * Resume deletes that were pending when the bot last shut down. Called once
 * from the ready handler. Clears the flag regardless of fetch result so a
 * stale flag (e.g. channel already gone) can't loop.
 */
async function resumePendingDeletes(client) {
  const pending = await Ticket.find({ pendingDelete: true }).lean().catch(() => []);
  if (!pending.length) return;
  for (const ticket of pending) {
    try {
      const guild = client.guilds.cache.first();
      if (guild && ticket.discordThreadId) {
        const channel = await guild.channels.fetch(ticket.discordThreadId).catch(() => null);
        if (channel) {
          enqueueDelete(channel).catch(() => {});
        }
      }
      Ticket.updateOne(
        { gmailThreadId: ticket.gmailThreadId },
        { $unset: { pendingDelete: '' } }
      ).catch(() => {});
    } catch (e) {
      console.error('resumePendingDeletes error:', e);
    }
  }
}

module.exports = {
  getNextTicketNumber,
  getOrCreateTicketCategory,
  cleanupEmptyOverflowCategory,
  getSenderLocal,
  toDiscordSafeName,
  resolveCreatorNickname,
  makeTicketName,
  checkTicketCreationRateLimit,
  checkTicketLimits,
  updateTicketActivity,
  checkAutoClose,
  checkAutoUnclaim,
  reconcileDeletedTicketChannels,
  resumePendingDeletes,
  startTicketsSweeps
};