lib/src/support/cache/RedisCache.ts

import {Cache, Maybe} from '../../util'
import {Inject, Injectable} from '../../di'
import {Redis} from '../redis/Redis'

/**
 * Redis-driven Cache implementation.
 */
@Injectable()
export class RedisCache extends Cache {
    /** The Redis service. */
    @Inject()
    protected readonly redis!: Redis

    async arrayPop(key: string): Promise<string | undefined> {
        return this.redis.pipe()
            .tap(redis => redis.lpop(key))
            .resolve()
    }

    async arrayPush(key: string, value: string): Promise<void> {
        await this.redis.pipe()
            .tap(redis => redis.rpush(key, value))
            .resolve()
    }

    async decrement(key: string, amount?: number): Promise<number | undefined> {
        return this.redis.pipe()
            .tap(redis => redis.decrby(key, amount ?? 1))
            .resolve()
    }

    async increment(key: string, amount?: number): Promise<number | undefined> {
        return this.redis.pipe()
            .tap(redis => redis.incrby(key, amount ?? 1))
            .resolve()
    }

    async drop(key: string): Promise<void> {
        await this.redis.pipe()
            .tap(redis => redis.del(key))
            .resolve()
    }

    async fetch(key: string): Promise<string | undefined> {
        return this.redis.pipe()
            .tap(redis => redis.get(key))
            .tap(value => value ?? undefined)
            .resolve()
    }

    async has(key: string): Promise<boolean> {
        return this.redis.pipe()
            .tap(redis => redis.exists(key))
            .tap(numExisting => numExisting > 0)
            .resolve()
    }

    pop(key: string): Promise<Maybe<string>> {
        return new Promise<Maybe<string>>((res, rej) => {
            this.redis.pipe()
                .tap(redis => {
                    redis.multi()
                        .get(key, (err, value) => {
                            if ( err ) {
                                rej(err)
                            } else {
                                res(value)
                            }
                        })
                        .del(key)
                })
        })
    }

    async put(key: string, value: string, expires?: Date): Promise<void> {
        await this.redis.multi()
            .tap(redis => redis.set(key, value))
            .when(Boolean(expires), redis => {
                const seconds = Math.round((expires!.getTime() - (new Date()).getTime()) / 1000)  // eslint-disable-line @typescript-eslint/no-non-null-assertion
                return redis.expire(key, seconds)
            })
            .tap(pipeline => pipeline.exec())
            .resolve()
    }
}