scrabble-solver/packages/dictionaries/src/lib/MemoryCache.ts

Scrabble Solver 2 - Free, open-source, cross-platform, multi-language analysis tool for Scrabble, Scrabble Duel, Super Scrabble, Letter League, Crossplay, Literaki, and Kelimelik. Quickly find the top-scoring words using the given board and tiles.

import { type Trie } from '@kamilmielnik/trie';
import { type Locale } from '@scrabble-solver/types';

import { CACHE_STALE_THRESHOLD } from '../constants';
import type { Cache } from '../types';

export class MemoryCache implements Cache<Locale, Trie> {
  private readonly cache: Partial<Record<Locale, Trie>> = {};

  private readonly cacheTimestamps: Partial<Record<Locale, number>> = {};

  public get(locale: Locale): Promise<Trie | undefined> {
    return Promise.resolve(this.cache[locale]);
  }

  public getLastModifiedTimestamp(locale: Locale): number | undefined {
    return this.cacheTimestamps[locale];
  }

  public has(locale: Locale): boolean {
    return typeof this.cache[locale] !== 'undefined';
  }

  public isStale(locale: Locale): boolean | undefined {
    const timestamp = this.getLastModifiedTimestamp(locale);

    if (!this.has(locale) || typeof timestamp === 'undefined') {
      return undefined;
    }

    const timeSinceModification = Math.abs(timestamp - Date.now());
    return timeSinceModification > CACHE_STALE_THRESHOLD;
  }

  public set(locale: Locale, trie: Trie): Promise<void> {
    this.cacheTimestamps[locale] = Date.now();
    this.cache[locale] = trie;
    return Promise.resolve();
  }
}