// Copyright (c) 2025 Joseph Hale
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.

import { debounce, type DebouncedFunc } from 'lodash';

export interface ExternalKeyValueStore {
  get: (key: string) => Promise<string | null>;
  set: (key: string, value: string) => Promise<void>;
}

export default class KeyValueStore {
  private external: ExternalKeyValueStore;
  private setters = new Map<
    string,
    DebouncedFunc<(value: string) => Promise<void>>
  >();

  constructor(external?: ExternalKeyValueStore) {
    this.external = external ?? new InMemoryKeyValueStore();
  }

  async put(key: string, value: string): Promise<void> {
    if (!this.setters.has(key)) {
      const setter = async (newVal: string) =>
        await this.external.set(key, newVal);
      this.setters.set(key, debounce(setter, 1000, { trailing: true }));
      return setter(value);
    } else {
      return this.setters.get(key)!(value);
    }
  }

  async read(key: string, defaultValue: string = ''): Promise<string> {
    const value = await this.external.get(key);
    return value ?? defaultValue;
  }
}

class InMemoryKeyValueStore implements ExternalKeyValueStore {
  private store = new Map<string, string>();

  async get(key: string): Promise<string | null> {
    return this.store.get(key) ?? null;
  }

  async set(key: string, value: string): Promise<void> {
    this.store.set(key, value);
  }
}