/**
 * Per-channel rename serialization with coalescing.
 * Renames route through utils/renamer.js (secondary bot token, RENAMER_BOT),
 * which has its own Discord-side rate bucket — no in-process throttle needed.
 * We serialize per channel so concurrent PATCHes don't land out of order, and
 * coalesce rapid successive calls so only the latest name is written.
 */

const { logWarn, logError } = require('../services/debugLog');
const { renameChannel } = require('../utils/renamer');

// Per-channel: { chain: Promise, pendingName: string | null }.
// enqueueRename updates pendingName synchronously (latest wins) and chains an
// executeRename link. executeRename reads the latest pendingName at start.
const renameChains = new Map();

async function executeRename(channel, entry) {
  const currentName = entry.pendingName;
  if (currentName == null) return;
  try {
    try {
      await renameChannel(channel.id, currentName);
    } catch (err) {
      // Secondary bot rate-limited (429), unauthorized (401), missing permission
      // (403), or no token configured — fall back to the primary Discord.js client.
      // Non-fallback errors rethrow so enqueueRename's catch can classify/log.
      if (err && err.fallback === true && channel && typeof channel.setName === 'function') {
        // Local log only; discord.js's REST client transparently handles 429s
        // on the primary fallback, so this used to post a paired warning to
        // the debug channel for every secondary-bot quota event with no
        // operator action required. Keep the visibility in container logs.
        console.warn(
          `[renameQueue] secondary-bot ${err.status ?? 'unavailable'}; falling back to primary channel=${channel.id}`
        );
        await channel.setName(currentName);
      } else {
        throw err;
      }
    }
  } finally {
    // Clear only if no newer call arrived during the PATCH. If pendingName
    // has changed, leave it — the link queued by that newer call picks it up.
    if (entry.pendingName === currentName) {
      entry.pendingName = null;
    }
  }
}

function enqueueRename(channel, newName) {
  let entry = renameChains.get(channel.id);
  if (!entry) {
    entry = { chain: Promise.resolve(), pendingName: newName };
    renameChains.set(channel.id, entry);
  } else {
    entry.pendingName = newName;
  }

  const next = entry.chain.catch(() => {}).then(() => executeRename(channel, entry));
  entry.chain = next;

  next.catch((err) => {
    logWarn('renameQueue', `Rename failed for ${channel.name}: ${err && err.message || err}`).catch(() => {});
    const status = err && err.status;
    const msg = (err && err.message) || String(err);
    if (status === 401 || status === 403) {
      logError(
        'renameQueue:token/permission',
        new Error(`secondary-bot ${status} channel=${channel.id} name=${channel.name}: ${msg}`)
      ).catch(() => {});
    } else if (status === 429) {
      logError(
        'renameQueue:secondary-bot ratelimited',
        new Error(`429 channel=${channel.id} name=${channel.name}: ${msg}`)
      ).catch(() => {});
    }
  }).finally(() => {
    if (renameChains.get(channel.id) === entry && entry.chain === next && entry.pendingName == null) {
      renameChains.delete(channel.id);
    }
  });
  return next;
}

// Shares renameChains so a move+rename pair on the same channel executes in
// call order. No coalescing: every move is a distinct chain link.
//
// lockPermissions: false preserves the channel's existing permission overwrites
// across the parent change. With the default (true), Discord re-syncs the
// channel's overwrites to match the new category and wipes per-user grants —
// in practice that kicked the ticket creator and any /add'd users off the
// channel on every escalate / de-escalate / /move.
function enqueueMove(channel, categoryId) {
  let entry = renameChains.get(channel.id);
  if (!entry) {
    entry = { chain: Promise.resolve(), pendingName: null };
    renameChains.set(channel.id, entry);
  }

  const next = entry.chain.catch(() => {}).then(() => channel.setParent(categoryId, { lockPermissions: false }));
  entry.chain = next;

  next.catch((err) => {
    logWarn('moveQueue', `Move failed for ${channel.name}: ${err && err.message || err}`).catch(() => {});
    const status = err && err.status;
    const msg = (err && err.message) || String(err);
    if (status === 401 || status === 403) {
      logError(
        'moveQueue:token/permission',
        new Error(`${status} channel=${channel.id} categoryId=${categoryId}: ${msg}`)
      ).catch(() => {});
    } else if (status === 429) {
      logError(
        'moveQueue:ratelimited',
        new Error(`429 channel=${channel.id} categoryId=${categoryId}: ${msg}`)
      ).catch(() => {});
    }
  }).finally(() => {
    if (renameChains.get(channel.id) === entry && entry.chain === next && entry.pendingName == null) {
      renameChains.delete(channel.id);
    }
  });
  return next;
}

// Shares renameChains so a permissionOverwrite mutation serializes with pending
// renames/moves on the same channel. Mode 'create' calls
// `channel.permissionOverwrites.create(id, perms)`; 'delete' calls
// `channel.permissionOverwrites.delete(id)`. No coalescing.
function enqueueOverwrite(channel, id, perms, mode = 'create') {
  let entry = renameChains.get(channel.id);
  if (!entry) {
    entry = { chain: Promise.resolve(), pendingName: null };
    renameChains.set(channel.id, entry);
  }

  const next = entry.chain.catch(() => {}).then(() =>
    mode === 'delete'
      ? channel.permissionOverwrites.delete(id)
      : channel.permissionOverwrites.create(id, perms)
  );
  entry.chain = next;

  next.catch((err) => {
    logWarn('overwriteQueue', `Overwrite ${mode} failed for ${channel.name}: ${err && err.message || err}`).catch(() => {});
    const status = err && err.status;
    const msg = (err && err.message) || String(err);
    if (status === 401 || status === 403) {
      logError(
        'overwriteQueue:token/permission',
        new Error(`${status} channel=${channel.id} target=${id} mode=${mode}: ${msg}`)
      ).catch(() => {});
    } else if (status === 429) {
      logError(
        'overwriteQueue:ratelimited',
        new Error(`429 channel=${channel.id} target=${id} mode=${mode}: ${msg}`)
      ).catch(() => {});
    }
  }).finally(() => {
    if (renameChains.get(channel.id) === entry && entry.chain === next && entry.pendingName == null) {
      renameChains.delete(channel.id);
    }
  });
  return next;
}

// Shares renameChains so setTopic serializes with pending renames/moves.
function enqueueTopic(channel, text) {
  let entry = renameChains.get(channel.id);
  if (!entry) {
    entry = { chain: Promise.resolve(), pendingName: null };
    renameChains.set(channel.id, entry);
  }

  const next = entry.chain.catch(() => {}).then(() => channel.setTopic(text));
  entry.chain = next;

  next.catch((err) => {
    logWarn('topicQueue', `Topic set failed for ${channel.name}: ${err && err.message || err}`).catch(() => {});
    const status = err && err.status;
    const msg = (err && err.message) || String(err);
    if (status === 401 || status === 403) {
      logError(
        'topicQueue:token/permission',
        new Error(`${status} channel=${channel.id}: ${msg}`)
      ).catch(() => {});
    } else if (status === 429) {
      logError(
        'topicQueue:ratelimited',
        new Error(`429 channel=${channel.id}: ${msg}`)
      ).catch(() => {});
    }
  }).finally(() => {
    if (renameChains.get(channel.id) === entry && entry.chain === next && entry.pendingName == null) {
      renameChains.delete(channel.id);
    }
  });
  return next;
}

// Per-channel promise chain for send ordering and to prevent interleaving.
const sendChains = new Map();

function enqueueSend(channel, ...args) {
  if (!channel || typeof channel.send !== 'function') {
    return Promise.reject(new Error('enqueueSend: invalid channel'));
  }
  const prev = sendChains.get(channel.id) || Promise.resolve();
  const next = prev.catch(() => {}).then(() => channel.send(...args));
  sendChains.set(channel.id, next);
  next.catch(() => {}).finally(() => {
    if (sendChains.get(channel.id) === next) sendChains.delete(channel.id);
  });
  return next;
}

// Delete a channel only after every in-flight send/rename/move on it has drained.
// Chains on both renameChains and sendChains so "pending send in-flight, delete
// racing it" can no longer hit Discord's unknown-channel 10003.
function enqueueDelete(channel) {
  if (!channel || typeof channel.delete !== 'function') {
    return Promise.reject(new Error('enqueueDelete: invalid channel'));
  }
  const renameEntry = renameChains.get(channel.id);
  const prevRename = renameEntry ? renameEntry.chain : Promise.resolve();
  const prevSend = sendChains.get(channel.id) || Promise.resolve();

  const next = Promise.all([
    prevRename.catch(() => {}),
    prevSend.catch(() => {})
  ]).then(() => channel.delete().catch(() => {}));

  if (renameEntry) renameEntry.chain = next;
  sendChains.set(channel.id, next);

  next.finally(() => {
    if (renameEntry && renameChains.get(channel.id) === renameEntry && renameEntry.chain === next) {
      renameChains.delete(channel.id);
    }
    if (sendChains.get(channel.id) === next) sendChains.delete(channel.id);
  });
  return next;
}

module.exports = { enqueueRename, enqueueMove, enqueueOverwrite, enqueueTopic, enqueueSend, enqueueDelete };