/*
 * SPDX-FileCopyrightText: syuilo and misskey-project
 * SPDX-License-Identifier: AGPL-3.0-only
 */

import { Inject, Injectable } from '@nestjs/common';
import * as Redis from 'ioredis';
import { DI } from '@/di-symbols.js';
import type { MiNote } from '@/models/Note.js';
import { bindThis } from '@/decorators.js';
import type { MiUser, NotesRepository } from '@/models/_.js';
import type { Config } from '@/config.js';
import { PER_NOTE_REACTION_USER_PAIR_CACHE_MAX } from '@/const.js';

const REDIS_DELTA_PREFIX = 'reactionsBufferDeltas';
const REDIS_PAIR_PREFIX = 'reactionsBufferPairs';

@Injectable()
export class ReactionsBufferingService {
	constructor(
		@Inject(DI.config)
		private config: Config,

		@Inject(DI.redisForReactions)
		private redisForReactions: Redis.Redis, // TODO: 専用のRedisインスタンスにする

		@Inject(DI.notesRepository)
		private notesRepository: NotesRepository,
	) {
	}

	@bindThis
	public async create(noteId: MiNote['id'], userId: MiUser['id'], reaction: string, currentPairs: string[]): Promise<void> {
		const pipeline = this.redisForReactions.pipeline();
		pipeline.hincrby(`${REDIS_DELTA_PREFIX}:${noteId}`, reaction, 1);
		for (let i = 0; i < currentPairs.length; i++) {
			pipeline.zadd(`${REDIS_PAIR_PREFIX}:${noteId}`, i, currentPairs[i]);
		}
		pipeline.zadd(`${REDIS_PAIR_PREFIX}:${noteId}`, Date.now(), `${userId}/${reaction}`);
		pipeline.zremrangebyrank(`${REDIS_PAIR_PREFIX}:${noteId}`, 0, -(PER_NOTE_REACTION_USER_PAIR_CACHE_MAX + 1));
		await pipeline.exec();
	}

	@bindThis
	public async delete(noteId: MiNote['id'], userId: MiUser['id'], reaction: string): Promise<void> {
		const pipeline = this.redisForReactions.pipeline();
		pipeline.hincrby(`${REDIS_DELTA_PREFIX}:${noteId}`, reaction, -1);
		pipeline.zrem(`${REDIS_PAIR_PREFIX}:${noteId}`, `${userId}/${reaction}`);
		// TODO: 「消した要素一覧」も持っておかないとcreateされた時に上書きされて復活する
		await pipeline.exec();
	}

	@bindThis
	public async get(noteId: MiNote['id']): Promise<{
		deltas: Record<string, number>;
		pairs: ([MiUser['id'], string])[];
	}> {
		const pipeline = this.redisForReactions.pipeline();
		pipeline.hgetall(`${REDIS_DELTA_PREFIX}:${noteId}`);
		pipeline.zrange(`${REDIS_PAIR_PREFIX}:${noteId}`, 0, -1);
		const results = await pipeline.exec();

		const resultDeltas = results![0][1] as Record<string, string>;
		const resultPairs = results![1][1] as string[];

		const deltas = {} as Record<string, number>;
		for (const [name, count] of Object.entries(resultDeltas)) {
			deltas[name] = parseInt(count);
		}

		const pairs = resultPairs.map(x => x.split('/') as [MiUser['id'], string]);

		return {
			deltas,
			pairs,
		};
	}

	@bindThis
	public async getMany(noteIds: MiNote['id'][]): Promise<Map<MiNote['id'], {
		deltas: Record<string, number>;
		pairs: ([MiUser['id'], string])[];
	}>> {
		const map = new Map<MiNote['id'], {
			deltas: Record<string, number>;
			pairs: ([MiUser['id'], string])[];
		}>();

		const pipeline = this.redisForReactions.pipeline();
		for (const noteId of noteIds) {
			pipeline.hgetall(`${REDIS_DELTA_PREFIX}:${noteId}`);
			pipeline.zrange(`${REDIS_PAIR_PREFIX}:${noteId}`, 0, -1);
		}
		const results = await pipeline.exec();

		const opsForEachNotes = 2;
		for (let i = 0; i < noteIds.length; i++) {
			const noteId = noteIds[i];
			const resultDeltas = results![i * opsForEachNotes][1] as Record<string, string>;
			const resultPairs = results![i * opsForEachNotes + 1][1] as string[];

			const deltas = {} as Record<string, number>;
			for (const [name, count] of Object.entries(resultDeltas)) {
				deltas[name] = parseInt(count);
			}

			const pairs = resultPairs.map(x => x.split('/') as [MiUser['id'], string]);

			map.set(noteId, {
				deltas,
				pairs,
			});
		}

		return map;
	}

	// TODO: scanは重い可能性があるので、別途 bufferedNoteIds を直接Redis上に持っておいてもいいかもしれない
	@bindThis
	public async bake(): Promise<void> {
		const bufferedNoteIds = [];
		let cursor = '0';
		do {
			// https://github.com/redis/ioredis#transparent-key-prefixing
			const result = await this.redisForReactions.scan(
				cursor,
				'MATCH',
				`${this.config.redis.prefix}:${REDIS_DELTA_PREFIX}:*`,
				'COUNT',
				'1000');

			cursor = result[0];
			bufferedNoteIds.push(...result[1].map(x => x.replace(`${this.config.redis.prefix}:${REDIS_DELTA_PREFIX}:`, '')));
		} while (cursor !== '0');

		const bufferedMap = await this.getMany(bufferedNoteIds);

		// clear
		const pipeline = this.redisForReactions.pipeline();
		for (const noteId of bufferedNoteIds) {
			pipeline.del(`${REDIS_DELTA_PREFIX}:${noteId}`);
			pipeline.del(`${REDIS_PAIR_PREFIX}:${noteId}`);
		}
		await pipeline.exec();

		// TODO: SQL一個にまとめたい
		for (const [noteId, buffered] of bufferedMap) {
			const sql = Object.entries(buffered.deltas)
				.map(([reaction, count]) =>
					`jsonb_set("reactions", '{${reaction}}', (COALESCE("reactions"->>'${reaction}', '0')::int + ${count})::text::jsonb)`)
				.join(' || ');

			this.notesRepository.createQueryBuilder().update()
				.set({
					reactions: () => sql,
					reactionAndUserPairCache: buffered.pairs.map(x => x.join('/')),
				})
				.where('id = :id', { id: noteId })
				.execute();
		}
	}
}