import { useCallback, useMemo } from 'react';
import { useMatrixClient } from './useMatrixClient';
import { useAccountData } from './useAccountData';

const PAARROT_EMOJI_USAGE_EVENT = 'paarrot.favemojis';
const MAX_TRACKED_EMOJIS = 50;

export type EmojiUsageData = {
  [shortcode: string]: {
    count: number;
    lastUsed: number;
  };
};

/**
 * Hook for tracking emoji usage and storing favorites in Matrix account data
 * Stores emoji usage stats under paarrot.favemojis in user's account data
 */
export function useEmojiUsage() {
  const mx = useMatrixClient();
  const event = useAccountData(PAARROT_EMOJI_USAGE_EVENT);

  const emojiUsage = useMemo((): EmojiUsageData => {
    const content = event?.getContent<EmojiUsageData>();
    return content || {};
  }, [event]);

  /**
   * Track emoji usage (max 1 per message as per spec)
   * @param shortcode - Emoji shortcode (e.g., 'thumbsup', 'smile')
   */
  const trackEmojiUsage = useCallback(
    async (shortcode: string) => {
      const now = Date.now();
      const currentUsage = { ...emojiUsage };

      // Update or create emoji entry
      currentUsage[shortcode] = {
        count: (currentUsage[shortcode]?.count || 0) + 1,
        lastUsed: now,
      };

      // Keep only top MAX_TRACKED_EMOJIS by usage count
      const entries = Object.entries(currentUsage);
      if (entries.length > MAX_TRACKED_EMOJIS) {
        entries.sort((a, b) => b[1].count - a[1].count);
        const topEmojis = entries.slice(0, MAX_TRACKED_EMOJIS);
        const newUsage: EmojiUsageData = {};
        topEmojis.forEach(([key, value]) => {
          newUsage[key] = value;
        });
        await mx.setAccountData(PAARROT_EMOJI_USAGE_EVENT, newUsage);
      } else {
        await mx.setAccountData(PAARROT_EMOJI_USAGE_EVENT, currentUsage);
      }
    },
    [mx, emojiUsage]
  );

  /**
   * Get most used emoji shortcode
   * @returns Shortcode of most used emoji, or undefined if none tracked
   */
  const getMostUsedEmoji = useCallback((): string | undefined => {
    const entries = Object.entries(emojiUsage);
    if (entries.length === 0) return undefined;

    // Sort by count descending, then by lastUsed descending
    entries.sort((a, b) => {
      if (b[1].count !== a[1].count) {
        return b[1].count - a[1].count;
      }
      return b[1].lastUsed - a[1].lastUsed;
    });

    return entries[0][0];
  }, [emojiUsage]);

  /**
   * Get top N most used emojis
   * @param count - Number of top emojis to return
   * @returns Array of shortcodes sorted by usage
   */
  const getTopEmojis = useCallback(
    (count: number = 10): string[] => {
      const entries = Object.entries(emojiUsage);
      entries.sort((a, b) => {
        if (b[1].count !== a[1].count) {
          return b[1].count - a[1].count;
        }
        return b[1].lastUsed - a[1].lastUsed;
      });
      return entries.slice(0, count).map(([shortcode]) => shortcode);
    },
    [emojiUsage]
  );

  return {
    emojiUsage,
    trackEmojiUsage,
    getMostUsedEmoji,
    getTopEmojis,
  };
}