/*
  Copyright 2018 Google LLC

  Use of this source code is governed by an MIT-style
  license that can be found in the LICENSE file or at
  https://opensource.org/licenses/MIT.
*/
import { assert } from "../../utils/assert.js";
import type { BackgroundSyncQueueStoreEntry, UnidentifiedQueueStoreEntry } from "./BackgroundSyncQueueDb.js";
import { BackgroundSyncQueueDb } from "./BackgroundSyncQueueDb.js";

/**
 * A class to manage storing requests from a Queue in IndexedDB,
 * indexed by their queue name for easier access.
 *
 * Most developers will not need to access this class directly;
 * it is exposed for advanced use cases.
 */
export class BackgroundSyncQueueStore {
  private readonly _queueName: string;
  private readonly _queueDb: BackgroundSyncQueueDb;

  /**
   * Associates this instance with a Queue instance, so entries added can be
   * identified by their queue name.
   *
   * @param queueName
   */
  constructor(queueName: string) {
    this._queueName = queueName;
    this._queueDb = new BackgroundSyncQueueDb();
  }

  /**
   * Append an entry last in the queue.
   *
   * @param entry
   */
  async pushEntry(entry: UnidentifiedQueueStoreEntry): Promise<void> {
    if (process.env.NODE_ENV !== "production") {
      assert!.isType(entry, "object", {
        moduleName: "serwist",
        className: "BackgroundSyncQueueStore",
        funcName: "pushEntry",
        paramName: "entry",
      });
      assert!.isType(entry.requestData, "object", {
        moduleName: "serwist",
        className: "BackgroundSyncQueueStore",
        funcName: "pushEntry",
        paramName: "entry.requestData",
      });
    }

    delete entry.id;
    entry.queueName = this._queueName;

    await this._queueDb.addEntry(entry);
  }

  /**
   * Prepend an entry first in the queue.
   *
   * @param entry
   */
  async unshiftEntry(entry: UnidentifiedQueueStoreEntry): Promise<void> {
    if (process.env.NODE_ENV !== "production") {
      assert!.isType(entry, "object", {
        moduleName: "serwist",
        className: "BackgroundSyncQueueStore",
        funcName: "unshiftEntry",
        paramName: "entry",
      });
      assert!.isType(entry.requestData, "object", {
        moduleName: "serwist",
        className: "BackgroundSyncQueueStore",
        funcName: "unshiftEntry",
        paramName: "entry.requestData",
      });
    }

    const firstId = await this._queueDb.getFirstEntryId();

    if (firstId) {
      // Pick an ID one less than the lowest ID in the object store.
      entry.id = firstId - 1;
    } else {
      delete entry.id;
    }
    entry.queueName = this._queueName;

    await this._queueDb.addEntry(entry);
  }

  /**
   * Removes and returns the last entry in the queue matching the `queueName`.
   *
   * @returns
   */
  async popEntry(): Promise<BackgroundSyncQueueStoreEntry | undefined> {
    return this._removeEntry(await this._queueDb.getLastEntryByQueueName(this._queueName));
  }

  /**
   * Removes and returns the first entry in the queue matching the `queueName`.
   *
   * @returns
   */
  async shiftEntry(): Promise<BackgroundSyncQueueStoreEntry | undefined> {
    return this._removeEntry(await this._queueDb.getFirstEntryByQueueName(this._queueName));
  }

  /**
   * Returns all entries in the store matching the `queueName`.
   *
   * @returns
   */
  async getAll(): Promise<BackgroundSyncQueueStoreEntry[]> {
    return await this._queueDb.getAllEntriesByQueueName(this._queueName);
  }

  /**
   * Returns the number of entries in the store matching the `queueName`.
   *
   * @returns
   */
  async size(): Promise<number> {
    return await this._queueDb.getEntryCountByQueueName(this._queueName);
  }

  /**
   * Deletes the entry for the given ID.
   *
   * WARNING: this method does not ensure the deleted entry belongs to this
   * queue (i.e. matches the `queueName`). But this limitation is acceptable
   * as this class is not publicly exposed. An additional check would make
   * this method slower than it needs to be.
   *
   * @param id
   */
  async deleteEntry(id: number): Promise<void> {
    await this._queueDb.deleteEntry(id);
  }

  /**
   * Removes and returns the first or last entry in the queue (based on the
   * `direction` argument) matching the `queueName`.
   *
   * @returns
   * @private
   */
  async _removeEntry(entry?: BackgroundSyncQueueStoreEntry): Promise<BackgroundSyncQueueStoreEntry | undefined> {
    if (entry) {
      await this.deleteEntry(entry.id);
    }
    return entry;
  }
}