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

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 ---
// Discord rate limit: 2 channel renames per 10 minutes per channel (see https://discord.com/developers/docs/topics/rate-limits).
// When limit is reached we skip the rename and post: "Channel renamed too quickly. Try again <t:unlock:R>."

const RENAME_WINDOW_MS = 10 * 60 * 1000; // 10 minutes
const RENAME_LIMIT = 2;

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

function makeTicketName({ escalated, claimed }, ticket, guild) {
  const senderLocal = getSenderLocal(ticket.senderEmail);
  const num = ticket.ticketNumber || 1;
  if (escalated) {
    return claimed
      ? `e-ticket-${senderLocal}-${num}`
      : `escalated-ticket-${senderLocal}-${num}`;
  }
  return `ticket-${senderLocal}-${num}`;
}

async function canRename(ticket) {
  const now = Date.now();
  const fresh = await Ticket.findOne({ gmailThreadId: ticket.gmailThreadId })
    .select('renameCount renameWindowStart')
    .lean();
  if (!fresh) {
    return { ok: false, remaining: 0, waitMs: RENAME_WINDOW_MS };
  }

  const windowStart = (fresh.renameWindowStart && new Date(fresh.renameWindowStart).getTime()) || 0;
  const count = fresh.renameCount || 0;

  if (now - windowStart >= RENAME_WINDOW_MS) {
    await Ticket.updateOne(
      { gmailThreadId: ticket.gmailThreadId },
      { $set: { renameWindowStart: new Date(now), renameCount: 0 } }
    );
    ticket.renameWindowStart = new Date(now);
    ticket.renameCount = 0;
    return { ok: true, remaining: RENAME_LIMIT, waitMs: 0 };
  }

  if (count >= RENAME_LIMIT) {
    const waitMs = RENAME_WINDOW_MS - (now - windowStart);
    return { ok: false, remaining: 0, waitMs };
  }

  const updated = await Ticket.findOneAndUpdate(
    { gmailThreadId: ticket.gmailThreadId },
    { $inc: { renameCount: 1 } },
    { returnDocument: 'after' }
  )
    .select('renameCount renameWindowStart')
    .lean();

  if (!updated) {
    const waitMs = RENAME_WINDOW_MS - (now - windowStart);
    return { ok: false, remaining: 0, waitMs };
  }

  const newCount = updated.renameCount || 0;
  ticket.renameCount = newCount;
  ticket.renameWindowStart = updated.renameWindowStart;
  return { ok: true, remaining: RENAME_LIMIT - newCount, waitMs: 0 };
}

function minutesFromMs(ms) {
  return Math.max(1, Math.ceil(ms / 60000));
}

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

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

/**
 * 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, '\\$&');
}

/**
 * @deprecated Use getOrCreateTicketCategory instead.
 * @returns {null}
 */
function pickTicketCategoryId(guild, categoryIds) {
  console.warn('[tickets] pickTicketCategoryId is deprecated; use getOrCreateTicketCategory() instead');
  return null;
}

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);
  }
}

async function createTicketChannel(guild, ticketNumber, userId, subject) {
  if (CONFIG.USE_THREADS && CONFIG.THREAD_PARENT_CHANNEL) {
    const parentChannel = guild.channels.cache.get(CONFIG.THREAD_PARENT_CHANNEL);
    if (!parentChannel) {
      throw new Error('Thread parent channel not found');
    }

    const thread = await parentChannel.threads.create({
      name: `🎫・ticket-${ticketNumber}`,
      autoArchiveDuration: 1440,
      type: ChannelType.PrivateThread,
      invitable: false,
      reason: `Ticket #${ticketNumber}`
    });

    await thread.members.add(userId);
    // Add all members with the support role so they can see and reply in the thread
    if (CONFIG.ROLE_ID_TO_PING) {
      const role = guild.roles.cache.get(CONFIG.ROLE_ID_TO_PING);
      if (role?.members?.size) {
        for (const [memberId] of role.members) {
          if (memberId === userId) continue; // already added
          await thread.members.add(memberId).catch(() => {});
        }
      }
    }
    return thread;
  } else {
    let parentId;
    try {
      parentId = await getOrCreateTicketCategory(guild, CONFIG.TICKET_CATEGORY_ID, CONFIG.TICKET_CATEGORY_NAME);
    } catch (e) {
      console.error('getOrCreateTicketCategory (createTicketChannel):', e);
      throw new Error('Ticket category not found or could not be allocated');
    }

    let channel;
    try {
      channel = await guild.channels.create({
        name: `ticket-${ticketNumber}`,
        type: ChannelType.GuildText,
        parent: parentId,
        permissionOverwrites: [
          {
            id: guild.id,
            deny: [PermissionFlagsBits.ViewChannel]
          },
          {
            id: userId,
            allow: [
              PermissionFlagsBits.ViewChannel,
              PermissionFlagsBits.SendMessages,
              PermissionFlagsBits.ReadMessageHistory
            ]
          },
          {
            id: CONFIG.ROLE_ID_TO_PING,
            allow: [
              PermissionFlagsBits.ViewChannel,
              PermissionFlagsBits.SendMessages,
              PermissionFlagsBits.ReadMessageHistory
            ]
          }
        ]
      });
    } catch (e) {
      console.error('guild.channels.create (createTicketChannel):', e);
      throw e;
    }

    return channel;
  }
}

/**
 * Create a private Discord ticket thread under DISCORD_THREAD_CHANNEL_ID.
 * Adds creator and all members with ROLE_ID_TO_PING.
 * @param {import('discord.js').Guild} guild
 * @param {number} ticketNumber
 * @param {string} creatorUserId
 * @returns {Promise<import('discord.js').ThreadChannel>}
 */
async function createDiscordTicketAsThread(guild, ticketNumber, creatorUserId) {
  const parentId = CONFIG.DISCORD_THREAD_CHANNEL_ID;
  if (!parentId) throw new Error('DISCORD_THREAD_CHANNEL_ID is not set');
  const parentChannel = guild.channels.cache.get(parentId);
  if (!parentChannel) throw new Error('Discord thread parent channel not found');

  const thread = await parentChannel.threads.create({
    name: `🎫・ticket-${ticketNumber}`,
    autoArchiveDuration: 1440,
    type: ChannelType.PrivateThread,
    invitable: false,
    reason: `Ticket #${ticketNumber}`
  });

  await thread.members.add(creatorUserId);
  if (CONFIG.ROLE_ID_TO_PING) {
    const role = guild.roles.cache.get(CONFIG.ROLE_ID_TO_PING);
    if (role?.members?.size) {
      for (const [memberId] of role.members) {
        if (memberId === creatorUserId) continue;
        await thread.members.add(memberId).catch(() => {});
      }
    }
  }
  return thread;
}

/**
 * Create a private email ticket thread under EMAIL_THREAD_CHANNEL_ID.
 * Adds all members with ROLE_ID_TO_PING (no creator; email tickets have no Discord user).
 * @param {import('discord.js').Guild} guild
 * @param {number} ticketNumber
 * @param {string} chanName
 * @returns {Promise<import('discord.js').ThreadChannel>}
 */
async function createEmailTicketAsThread(guild, ticketNumber, chanName) {
  const parentId = CONFIG.EMAIL_THREAD_CHANNEL_ID;
  if (!parentId) throw new Error('EMAIL_THREAD_CHANNEL_ID is not set');
  const parentChannel = guild.channels.cache.get(parentId);
  if (!parentChannel) throw new Error('Email thread parent channel not found');

  const thread = await parentChannel.threads.create({
    name: chanName || `🎫・ticket-${ticketNumber}`,
    autoArchiveDuration: 1440,
    type: ChannelType.PrivateThread,
    invitable: false,
    reason: `Ticket #${ticketNumber}`
  });

  if (CONFIG.ROLE_ID_TO_PING) {
    const role = guild.roles.cache.get(CONFIG.ROLE_ID_TO_PING);
    if (role?.members?.size) {
      for (const [memberId] of role.members) {
        await thread.members.add(memberId).catch(() => {});
      }
    }
  }
  return thread;
}

// --- 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 };
}

function hasBlacklistedRole(member) {
  if (!CONFIG.BLACKLISTED_ROLES || CONFIG.BLACKLISTED_ROLES.length === 0) {
    return false;
  }
  return member.roles.cache.some(role =>
    CONFIG.BLACKLISTED_ROLES.includes(role.id)
  );
}

// --- ACTIVITY ---

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

// --- 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));
  const staleTickets = await Ticket.find({
    status: 'open',
    lastActivity: { $lt: cutoffTime, $ne: null }
  }).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 channel.send(CONFIG.DISCORD_AUTO_CLOSE_MESSAGE);

        await Ticket.updateOne(
          { gmailThreadId: ticket.gmailThreadId },
          { $set: { status: 'closed' } }
        );

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

        setTimeout(() => channel.delete().catch(() => {}), 5000);
      }
    } catch (error) {
      console.error(`Auto-close error for ticket ${ticket.gmailThreadId}:`, error);
    }
  }
}

async function checkReminders(client) {
  if (!CONFIG.REMINDER_ENABLED) return;

  const reminderTime = new Date(Date.now() - (CONFIG.REMINDER_AFTER_HOURS * 60 * 60 * 1000));
  const ticketsNeedingReminder = await Ticket.find({
    status: 'open',
    lastActivity: { $lt: reminderTime, $ne: null },
    reminderSent: false
  }).lean();

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

      const channel = await guild.channels.fetch(ticket.discordThreadId).catch(() => null);
      if (channel) {
        const ping = ticket.claimedBy
          ? `<@${ticket.claimedBy}>`
          : (CONFIG.ROLE_ID_TO_PING ? `<@&${CONFIG.ROLE_ID_TO_PING}>` : 'everyone');
        const message = CONFIG.REMINDER_MESSAGE
          .replace(/\{hours\}/g, String(CONFIG.REMINDER_AFTER_HOURS))
          .replace(/\{ping\}/g, ping);
        await channel.send(message);

        await Ticket.updateOne(
          { gmailThreadId: ticket.gmailThreadId },
          { $set: { reminderSent: true } }
        );
      }
    } catch (error) {
      console.error(`Reminder 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 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 Ticket.updateOne(
          { gmailThreadId: ticket.gmailThreadId },
          { $set: { claimedBy: null } }
        );

        await channel.send(
          `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);
    }
  }
}

module.exports = {
  getNextTicketNumber,
  pickTicketCategoryId,
  getOrCreateTicketCategory,
  cleanupEmptyOverflowCategory,
  createDiscordTicketAsThread,
  createEmailTicketAsThread,
  RENAME_WINDOW_MS,
  RENAME_LIMIT,
  getSenderLocal,
  makeTicketName,
  canRename,
  minutesFromMs,
  checkTicketCreationRateLimit,
  createTicketChannel,
  checkTicketLimits,
  hasBlacklistedRole,
  updateTicketActivity,
  checkAutoClose,
  checkReminders,
  checkAutoUnclaim
};