/*
 * Copyright (C) 2026 Fluxer Contributors
 *
 * This file is part of Fluxer.
 *
 * Fluxer is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Fluxer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with Fluxer. If not, see <https://www.gnu.org/licenses/>.
 */

import type {GuildEmoji, GuildEmojiWithUser} from '~/records/GuildEmojiRecord';
import type {GuildSticker, GuildStickerWithUser} from '~/records/GuildStickerRecord';
import {sortBySnowflakeDesc} from '~/utils/SnowflakeUtils';

type EmojiUpdateListener = (emojis: ReadonlyArray<GuildEmojiWithUser>) => void;
type StickerUpdateListener = (stickers: ReadonlyArray<GuildStickerWithUser>) => void;

const emojiCache = new Map<string, ReadonlyArray<GuildEmojiWithUser>>();
const stickerCache = new Map<string, ReadonlyArray<GuildStickerWithUser>>();

const emojiListeners = new Map<string, Set<EmojiUpdateListener>>();
const stickerListeners = new Map<string, Set<StickerUpdateListener>>();

const freezeList = <T>(items: ReadonlyArray<T>): ReadonlyArray<T> => Object.freeze([...items]);

const notifyListeners = <T>(
	listeners: Map<string, Set<(items: ReadonlyArray<T>) => void>>,
	guildId: string,
	value: ReadonlyArray<T>,
) => {
	const listenersForGuild = listeners.get(guildId);
	if (!listenersForGuild) return;
	for (const listener of listenersForGuild) {
		listener(value);
	}
};

const setCache = <T extends {id: string}>(
	cache: Map<string, ReadonlyArray<T>>,
	listeners: Map<string, Set<(items: ReadonlyArray<T>) => void>>,
	guildId: string,
	value: ReadonlyArray<T>,
	shouldNotify: boolean,
) => {
	const frozen = freezeList(sortBySnowflakeDesc(value));
	cache.set(guildId, frozen);
	if (shouldNotify) {
		notifyListeners(listeners, guildId, frozen);
	}
};

export const seedGuildEmojiCache = (guildId: string, emojis: ReadonlyArray<GuildEmojiWithUser>): void => {
	setCache(emojiCache, emojiListeners, guildId, emojis, false);
};

export const seedGuildStickerCache = (guildId: string, stickers: ReadonlyArray<GuildStickerWithUser>): void => {
	setCache(stickerCache, stickerListeners, guildId, stickers, false);
};

export const subscribeToGuildEmojiUpdates = (guildId: string, listener: EmojiUpdateListener): (() => void) => {
	let listenersForGuild = emojiListeners.get(guildId);
	if (!listenersForGuild) {
		listenersForGuild = new Set();
		emojiListeners.set(guildId, listenersForGuild);
	}
	listenersForGuild.add(listener);
	return () => {
		listenersForGuild?.delete(listener);
		if (listenersForGuild && listenersForGuild.size === 0) {
			emojiListeners.delete(guildId);
		}
	};
};

export const subscribeToGuildStickerUpdates = (guildId: string, listener: StickerUpdateListener): (() => void) => {
	let listenersForGuild = stickerListeners.get(guildId);
	if (!listenersForGuild) {
		listenersForGuild = new Set();
		stickerListeners.set(guildId, listenersForGuild);
	}
	listenersForGuild.add(listener);
	return () => {
		listenersForGuild?.delete(listener);
		if (listenersForGuild && listenersForGuild.size === 0) {
			stickerListeners.delete(guildId);
		}
	};
};

export const patchGuildEmojiCacheFromGateway = (guildId: string, updates: ReadonlyArray<GuildEmoji>) => {
	const previous = emojiCache.get(guildId) ?? [];
	const previousUserById = new Map(previous.map((emoji) => [emoji.id, emoji.user]));

	const next = updates.map((emoji) => ({
		...emoji,
		user: emoji.user ?? previousUserById.get(emoji.id),
	}));

	setCache(emojiCache, emojiListeners, guildId, next, true);
};

export const patchGuildStickerCacheFromGateway = (guildId: string, updates: ReadonlyArray<GuildSticker>) => {
	const previous = stickerCache.get(guildId) ?? [];
	const previousUserById = new Map(previous.map((sticker) => [sticker.id, sticker.user]));

	const next = updates.map((sticker) => ({
		...sticker,
		user: sticker.user ?? previousUserById.get(sticker.id),
	}));

	setCache(stickerCache, stickerListeners, guildId, next, true);
};