TLをPush型にする（Write only) (MisskeyIO#185)

* 一時的に Redis に書き込むユーザーをモデレータのみに絞る

---------

Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>

packages/backend/src/core/FeaturedService.ts

@@ -0,0 +1,116 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import * as Redis from 'ioredis';
+import type { MiNote, MiUser } from '@/models/index.js';
+import { DI } from '@/di-symbols.js';
+import { bindThis } from '@/decorators.js';
+
+const GLOBAL_NOTES_RANKING_WINDOW = 1000 * 60 * 60 * 24 * 3; // 3日ごと
+const PER_USER_NOTES_RANKING_WINDOW = 1000 * 60 * 60 * 24 * 7; // 1週間ごと
+const HASHTAG_RANKING_WINDOW = 1000 * 60 * 60; // 1時間ごと
+
+@Injectable()
+export class FeaturedService {
+	constructor(
+		@Inject(DI.redis)
+		private redisClient: Redis.Redis, // TODO: 専用のRedisサーバーを設定できるようにする
+	) {
+	}
+
+	@bindThis
+	private getCurrentWindow(windowRange: number): number {
+		const passed = new Date().getTime() - new Date(new Date().getFullYear(), 0, 1).getTime();
+		return Math.floor(passed / windowRange);
+	}
+
+	@bindThis
+	private async updateRankingOf(name: string, windowRange: number, element: string, score = 1): Promise<void> {
+		const currentWindow = this.getCurrentWindow(windowRange);
+		const redisTransaction = this.redisClient.multi();
+		redisTransaction.zincrby(
+			`${name}:${currentWindow}`,
+			score,
+			element);
+		redisTransaction.expire(
+			`${name}:${currentWindow}`,
+			(windowRange * 3) / 1000,
+			'NX'); // "NX -- Set expiry only when the key has no expiry" = 有効期限がないときだけ設定
+		await redisTransaction.exec();
+	}
+
+	@bindThis
+	private async getRankingOf(name: string, windowRange: number, threshold: number): Promise<string[]> {
+		const currentWindow = this.getCurrentWindow(windowRange);
+		const previousWindow = currentWindow - 1;
+
+		const redisPipeline = this.redisClient.pipeline();
+		redisPipeline.zrange(
+			`${name}:${currentWindow}`, 0, threshold, 'REV', 'WITHSCORES');
+		redisPipeline.zrange(
+			`${name}:${previousWindow}`, 0, threshold, 'REV', 'WITHSCORES');
+		const [currentRankingResult, previousRankingResult] = await redisPipeline.exec().then(result => result ? result.map(r => r[1] as string[]) : [[], []]);
+
+		const ranking = new Map<string, number>();
+		for (let i = 0; i < currentRankingResult.length; i += 2) {
+			const noteId = currentRankingResult[i];
+			const score = parseInt(currentRankingResult[i + 1], 10);
+			ranking.set(noteId, score);
+		}
+		for (let i = 0; i < previousRankingResult.length; i += 2) {
+			const noteId = previousRankingResult[i];
+			const score = parseInt(previousRankingResult[i + 1], 10);
+			const exist = ranking.get(noteId);
+			if (exist != null) {
+				ranking.set(noteId, (exist + score) / 2);
+			} else {
+				ranking.set(noteId, score);
+			}
+		}
+
+		return Array.from(ranking.keys());
+	}
+
+	@bindThis
+	public updateGlobalNotesRanking(noteId: MiNote['id'], score = 1): Promise<void> {
+		return this.updateRankingOf('featuredGlobalNotesRanking', GLOBAL_NOTES_RANKING_WINDOW, noteId, score);
+	}
+
+	@bindThis
+	public updateInChannelNotesRanking(channelId: MiNote['channelId'], noteId: MiNote['id'], score = 1): Promise<void> {
+		return this.updateRankingOf(`featuredInChannelNotesRanking:${channelId}`, GLOBAL_NOTES_RANKING_WINDOW, noteId, score);
+	}
+
+	@bindThis
+	public updatePerUserNotesRanking(userId: MiUser['id'], noteId: MiNote['id'], score = 1): Promise<void> {
+		return this.updateRankingOf(`featuredPerUserNotesRanking:${userId}`, PER_USER_NOTES_RANKING_WINDOW, noteId, score);
+	}
+
+	@bindThis
+	public updateHashtagsRanking(hashtag: string, score = 1): Promise<void> {
+		return this.updateRankingOf('featuredHashtagsRanking', HASHTAG_RANKING_WINDOW, hashtag, score);
+	}
+
+	@bindThis
+	public getGlobalNotesRanking(threshold: number): Promise<MiNote['id'][]> {
+		return this.getRankingOf('featuredGlobalNotesRanking', GLOBAL_NOTES_RANKING_WINDOW, threshold);
+	}
+
+	@bindThis
+	public getInChannelNotesRanking(channelId: MiNote['channelId'], threshold: number): Promise<MiNote['id'][]> {
+		return this.getRankingOf(`featuredInChannelNotesRanking:${channelId}`, GLOBAL_NOTES_RANKING_WINDOW, threshold);
+	}
+
+	@bindThis
+	public getPerUserNotesRanking(userId: MiUser['id'], threshold: number): Promise<MiNote['id'][]> {
+		return this.getRankingOf(`featuredPerUserNotesRanking:${userId}`, PER_USER_NOTES_RANKING_WINDOW, threshold);
+	}
+
+	@bindThis
+	public getHashtagsRanking(threshold: number): Promise<string[]> {
+		return this.getRankingOf('featuredHashtagsRanking', HASHTAG_RANKING_WINDOW, threshold);
+	}
+}