const WINDOW_MS = 150_000; // 2.5 minutes
const recentPosts = new Map();

function normalizeKey(text) {
  return text.toLowerCase().replace(/\s+/g, " ").trim().slice(0, 200);
}

function dedupePriorMessages(priorMessages) {
  const seen = new Set();
  return priorMessages.filter(({ channelId, messageId }) => {
    const entry = `${channelId}:${messageId}`;
    if (seen.has(entry)) return false;
    seen.add(entry);
    return true;
  });
}

function trackCrossChannelPost(guildId, userId, channelId, messageId, keySuffix) {
  const normalized = normalizeKey(keySuffix);
  if (!normalized) {
    return { duplicateAcrossChannels: false, priorMessages: [] };
  }

  const key = `${guildId}:${userId}:${normalized}`;
  const now = Date.now();
  const existing = recentPosts.get(key);

  if (existing && now - existing.firstSeen < WINDOW_MS) {
    const priorMessages = [...existing.messages.entries()].map(([chId, msgId]) => ({
      channelId: chId,
      messageId: msgId,
    }));

    existing.channels.add(channelId);
    existing.messages.set(channelId, messageId);

    const duplicateAcrossChannels = existing.channels.size >= 2;
    return { duplicateAcrossChannels, priorMessages: duplicateAcrossChannels ? priorMessages : [] };
  }

  recentPosts.set(key, {
    channels: new Set([channelId]),
    messages: new Map([[channelId, messageId]]),
    firstSeen: now,
  });

  pruneExpiredPosts(now);

  return { duplicateAcrossChannels: false, priorMessages: [] };
}

function pruneExpiredPosts(now) {
  if (recentPosts.size <= 5000) return;

  for (const [entryKey, entry] of recentPosts) {
    if (now - entry.firstSeen > WINDOW_MS) {
      recentPosts.delete(entryKey);
    }
  }
}

export function trackCrossChannelMessage(guildId, userId, channelId, messageId, text) {
  return trackCrossChannelPost(guildId, userId, channelId, messageId, normalizeKey(text));
}

export function trackCrossChannelKeys(guildId, userId, channelId, messageId, keys) {
  const uniqueKeys = [...new Set(keys.map((key) => normalizeKey(key)).filter(Boolean))];
  if (uniqueKeys.length === 0) {
    return { duplicateAcrossChannels: false, priorMessages: [] };
  }

  const trackers = uniqueKeys.map((key) =>
    trackCrossChannelPost(guildId, userId, channelId, messageId, key)
  );

  const duplicateAcrossChannels = trackers.some((tracker) => tracker.duplicateAcrossChannels);
  const priorMessages = duplicateAcrossChannels
    ? dedupePriorMessages(trackers.flatMap((tracker) => tracker.priorMessages))
    : [];

  return { duplicateAcrossChannels, priorMessages };
}

export { dedupePriorMessages };