kv-orm/core

import { Datastore, Value, Key } from "../Datastore/Datastore";
import {
  SearchStrategy,
  SearchOptions,
  SearchResult,
} from "../Datastore/Datastore";

export class MemoryDatastore extends Datastore {
  private SEARCH_FIRST_LIMIT = 1000;
  private SEARCH_FIRST_DEFAULT = 1000;
  private data: Map<Key, Value> = new Map(); // "remembers the original insertion order of the keys", https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map

  public searchStrategies = [SearchStrategy.prefix];

  _read(key: Key): Promise<Value> {
    return Promise.resolve(this.data.get(key) || null);
  }

  _write(key: Key, value: Value): Promise<void> {
    this.data.set(key, value);
    return Promise.resolve();
  }

  _delete(key: Key): Promise<void> {
    this.data.delete(key);
    return Promise.resolve();
  }

  _search({
    term,
    first = this.SEARCH_FIRST_DEFAULT,
    after = `-1`,
  }: SearchOptions): Promise<SearchResult> {
    if (first > this.SEARCH_FIRST_LIMIT) first = this.SEARCH_FIRST_LIMIT;
    if (first < 0) first = 0;

    let keys = Array.from(this.data.keys()).filter((key: Key) =>
      key.startsWith(term)
    );

    keys = keys.slice(+after + 1);

    const hasNextPage = keys.length > first;

    keys = keys.slice(0, first);

    const cursor = (+after + (hasNextPage ? first : keys.length)).toString();

    return Promise.resolve({
      keys,
      hasNextPage,
      cursor,
    });
  }
}