lib/src/support/cache/MemoryCache.ts

import {Cache, Collection, Awaitable} from '../../util'

/**
 * An in-memory implementation of the Cache.
 * This is the default implementation for compatibility, but applications should switch to a persistent-backed cache driver.
 */
export class MemoryCache extends Cache {
    /** Static collection of in-memory cache items. */
    private static cacheItems: Collection<{key: string, value: string, expires?: Date}> = new Collection<{key: string; value: string, expires?: Date}>()

    /** Static collection of in-memory arrays. */
    private static cacheArrays: Collection<{key: string, values: string[]}> = new Collection<{key: string; values: string[]}>()

    public fetch(key: string): string|undefined {
        const now = new Date()
        return MemoryCache.cacheItems
            .where('key', '=', key)
            .firstWhere(item => {
                return !item.expires || now < item.expires
            })?.value
    }

    public put(key: string, value: string, expires?: Date): Awaitable<void> {
        const existing = MemoryCache.cacheItems.firstWhere('key', '=', key)
        if ( existing ) {
            existing.value = value
            existing.expires = expires
        } else {
            MemoryCache.cacheItems.push({ key,
                value,
                expires })
        }
    }

    public has(key: string): Awaitable<boolean> {
        const now = new Date()
        return Boolean(MemoryCache.cacheItems
            .where('key', '=', key)
            .firstWhere(item => {
                return !item.expires || now < item.expires
            }))
    }

    public drop(key: string): Awaitable<void> {
        MemoryCache.cacheItems = MemoryCache.cacheItems.where('key', '!=', key)
    }

    public decrement(key: string, amount = 1): Awaitable<number | undefined> {
        const nextValue = (parseInt(this.fetch(key) ?? '0', 10) ?? 0) - amount
        this.put(key, String(nextValue))
        return nextValue
    }

    public increment(key: string, amount = 1): Awaitable<number | undefined> {
        const nextValue = (parseInt(this.fetch(key) ?? '0', 10) ?? 0) + amount
        this.put(key, String(nextValue))
        return nextValue
    }

    public pop(key: string): Awaitable<string | undefined> {
        const value = this.fetch(key)
        this.drop(key)
        return value
    }

    public arrayPop(key: string): Awaitable<string | undefined> {
        const arr = MemoryCache.cacheArrays.firstWhere('key', '=', key)
        if ( arr ) {
            return arr.values.shift()
        }
    }

    public arrayPush(key: string, value: string): Awaitable<void> {
        const arr = MemoryCache.cacheArrays.firstWhere('key', '=', key)
        if ( arr ) {
            arr.values.push(value)
        } else {
            MemoryCache.cacheArrays.push({
                key,
                values: [value],
            })
        }
    }
}