/**
 * Copyright 2015 CANAL+ Group
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import type {
  IMediaKeySession,
  IMediaKeys,
} from "../../../compat/browser_compatibility_types";
import { closeSession, generateKeyRequest, loadSession } from "../../../compat/eme";
import log from "../../../log";
import assert from "../../../utils/assert";
import isNullOrUndefined from "../../../utils/is_null_or_undefined";
import type { IProcessedProtectionData } from "../types";
import KeySessionRecord from "./key_session_record";

/**
 * Create and store MediaKeySessions linked to a single MediaKeys
 * instance.
 *
 * Keep track of sessionTypes and of the initialization data each
 * MediaKeySession is created for.
 * @class LoadedSessionsStore
 */
export default class LoadedSessionsStore {
  /** MediaKeys instance on which the MediaKeySessions are created. */
  private readonly _mediaKeys: IMediaKeys;

  /** Store unique MediaKeySession information per initialization data. */
  private _storage: IStoredSessionEntry[];

  /**
   * Create a new LoadedSessionsStore, which will store information about
   * loaded MediaKeySessions on the given MediaKeys instance.
   * @param {MediaKeys} mediaKeys
   */
  constructor(mediaKeys: IMediaKeys) {
    this._mediaKeys = mediaKeys;
    this._storage = [];
  }

  /**
   * Create a new MediaKeySession and store it in this store.
   * @param {Object} initData
   * @param {string} sessionType
   * @returns {Object}
   */
  public createSession(
    initData: IProcessedProtectionData,
    sessionType: MediaKeySessionType,
  ): IStoredSessionEntry {
    const keySessionRecord = new KeySessionRecord(initData);
    log.debug("DRM", "calling `createSession`", { sessionType });
    const mediaKeySession = this._mediaKeys.createSession(sessionType);
    const entry = {
      mediaKeySession,
      sessionType,
      keySessionRecord,
      isGeneratingRequest: false,
      isLoadingPersistentSession: false,
      closingStatus: { type: "none" as const },
    };
    if (!isNullOrUndefined(mediaKeySession.closed)) {
      mediaKeySession.closed
        .then(() => {
          log.info("DRM", "session was closed, removing it.", {
            sessionId: mediaKeySession.sessionId,
          });
          const index = this.getIndex(keySessionRecord);
          if (index >= 0 && this._storage[index].mediaKeySession === mediaKeySession) {
            this._storage.splice(index, 1);
          }
        })
        .catch((e: unknown) => {
          // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
          log.warn("DRM", `MediaKeySession.closed rejected: ${e}`);
        });
    }

    this._storage.push({ ...entry });
    log.debug("DRM", "MediaKeySession added", {
      sessionType: entry.sessionType,
      currentlyLoaded: this._storage.length,
    });
    return entry;
  }

  /**
   * Find a stored entry compatible with the initialization data given and moves
   * this entry at the end of the `LoadedSessionsStore`''s storage, returned by
   * its `getAll` method.
   *
   * This can be used for example to tell when a previously-stored
   * entry is re-used to then be able to implement a caching replacement
   * algorithm based on the least-recently-used values by just evicting the first
   * values returned by `getAll`.
   * @param {Object} initializationData
   * @returns {Object|null}
   */
  public reuse(initializationData: IProcessedProtectionData): IStoredSessionEntry | null {
    for (let i = this._storage.length - 1; i >= 0; i--) {
      const stored = this._storage[i];
      if (stored.keySessionRecord.isCompatibleWith(initializationData)) {
        this._storage.splice(i, 1);
        this._storage.push(stored);
        log.debug("DRM", "Reusing session:", {
          sessionId: stored.mediaKeySession.sessionId,
          sessionType: stored.sessionType,
        });
        return { ...stored };
      }
    }
    return null;
  }

  /**
   * Get `LoadedSessionsStore`'s entry for a given MediaKeySession.
   * Returns `null` if the given MediaKeySession is not stored in the
   * `LoadedSessionsStore`.
   * @param {MediaKeySession} mediaKeySession
   * @returns {Object|null}
   */
  public getEntryForSession(
    mediaKeySession: IMediaKeySession,
  ): IStoredSessionEntry | null {
    for (let i = this._storage.length - 1; i >= 0; i--) {
      const stored = this._storage[i];
      if (stored.mediaKeySession === mediaKeySession) {
        return { ...stored };
      }
    }
    return null;
  }

  /**
   * Generate a license request on the given MediaKeySession, while indicating
   * to the LoadedSessionsStore that a license-request is pending so
   * session-closing orders are properly scheduled after it is done.
   * @param {Object} mediaKeySession
   * @param {string|undefined} initializationDataType - Initialization data type
   * given e.g. by the "encrypted" event for the corresponding request.
   * @param {Uint8Array} initializationData - Initialization data given e.g. by
   * the "encrypted" event for the corresponding request.
   * @returns {Promise}
   */
  public async generateLicenseRequest(
    mediaKeySession: IMediaKeySession,
    initializationDataType: string | undefined,
    initializationData: Uint8Array<ArrayBuffer>,
  ): Promise<unknown> {
    let entry: IStoredSessionEntry | undefined;
    for (const stored of this._storage) {
      if (stored.mediaKeySession === mediaKeySession) {
        entry = stored;
        break;
      }
    }
    if (entry === undefined) {
      log.error(
        "DRM",
        "generateRequest error. No MediaKeySession found with " +
          "the given initData and initDataType",
      );
      return generateKeyRequest(
        mediaKeySession,
        initializationDataType,
        initializationData,
      );
    }

    entry.isGeneratingRequest = true;

    // Note the `as string` is needed due to TypeScript not understanding that
    // the `closingStatus` might change in the next checks
    if ((entry.closingStatus.type as string) !== "none") {
      throw new Error("The `MediaKeySession` is being closed.");
    }
    try {
      await generateKeyRequest(
        mediaKeySession,
        initializationDataType,
        initializationData,
      );
    } catch (err) {
      if (entry === undefined) {
        throw err;
      }
      entry.isGeneratingRequest = false;
      if (entry.closingStatus.type === "awaiting") {
        entry.closingStatus.start();
      }
      throw err;
    }
    if (entry === undefined) {
      return undefined;
    }
    entry.isGeneratingRequest = false;
    if (entry.closingStatus.type === "awaiting") {
      entry.closingStatus.start();
    }
  }

  /**
   * @param {Object} mediaKeySession
   * @param {string} sessionId
   * @returns {Promise}
   */
  public async loadPersistentSession(
    mediaKeySession: IMediaKeySession,
    sessionId: string,
  ): Promise<boolean> {
    let entry: IStoredSessionEntry | undefined;
    for (const stored of this._storage) {
      if (stored.mediaKeySession === mediaKeySession) {
        entry = stored;
        break;
      }
    }
    if (entry === undefined) {
      log.error(
        "DRM",
        "loadPersistentSession error. No MediaKeySession found with " +
          "the given initData and initDataType",
      );
      return loadSession(mediaKeySession, sessionId);
    }
    entry.isLoadingPersistentSession = true;

    // Note the `as string` is needed due to TypeScript not understanding that
    // the `closingStatus` might change in the next checks
    if ((entry.closingStatus.type as string) !== "none") {
      throw new Error("The `MediaKeySession` is being closed.");
    }
    let ret: boolean;
    try {
      ret = await loadSession(mediaKeySession, sessionId);
    } catch (err) {
      if (entry === undefined) {
        throw err;
      }
      entry.isLoadingPersistentSession = false;
      if (entry.closingStatus.type === "awaiting") {
        entry.closingStatus.start();
      }
      throw err;
    }
    if (entry === undefined) {
      return ret;
    }
    entry.isLoadingPersistentSession = false;
    if (entry.closingStatus.type === "awaiting") {
      entry.closingStatus.start();
    }
    return ret;
  }

  /**
   * Close a MediaKeySession and remove its related stored information from the
   * `LoadedSessionsStore`.
   * Emit when done.
   * @param {Object} mediaKeySession
   * @returns {Promise}
   */
  public async closeSession(mediaKeySession: IMediaKeySession): Promise<boolean> {
    let entry: IStoredSessionEntry | undefined;
    for (const stored of this._storage) {
      if (stored.mediaKeySession === mediaKeySession) {
        entry = stored;
        break;
      }
    }
    if (entry === undefined) {
      log.warn(
        "DRM",
        "No MediaKeySession found with " + "the given initData and initDataType",
      );
      return Promise.resolve(false);
    }
    return this._closeEntry(entry);
  }

  /**
   * Returns the number of stored MediaKeySessions in this LoadedSessionsStore.
   * @returns {number}
   */
  public getLength(): number {
    return this._storage.length;
  }

  /**
   * Returns information about all stored MediaKeySession, in the order in which
   * the MediaKeySession have been created.
   * @returns {Array.<Object>}
   */
  public getAll(): IStoredSessionEntry[] {
    return this._storage;
  }

  /**
   * Close all sessions in this store.
   * Emit `null` when done.
   * @returns {Promise}
   */
  public async closeAllSessions(): Promise<void> {
    const allEntries = this._storage;
    log.debug("DRM", "Closing all current MediaKeySessions", {
      numberOfEntries: allEntries.length,
    });

    // re-initialize the storage, so that new interactions with the
    // `LoadedSessionsStore` do not rely on MediaKeySessions we're in the
    // process of removing
    this._storage = [];

    const closingProms = allEntries.map((entry) => this._closeEntry(entry));
    await Promise.all(closingProms);
  }

  /**
   * Find the given `MediaKeySession` in the `LoadedSessionsStore` and removes
   * any reference to it without actually closing it.
   *
   * Returns `true` if the given `mediaKeySession` has been found and removed,
   * `false` otherwise.
   *
   * Note that this may create a `MediaKeySession` leakage in the wrong
   * conditions, cases where this method should be called should be very
   * carefully evaluated.
   * @param {MediaKeySession} mediaKeySession
   * @returns {boolean}
   */
  public removeSessionWithoutClosingIt(mediaKeySession: IMediaKeySession): boolean {
    assert(
      mediaKeySession.sessionId === "",
      "Initialized `MediaKeySession`s should always be properly closed",
    );
    for (let i = this._storage.length - 1; i >= 0; i--) {
      const stored = this._storage[i];
      if (stored.mediaKeySession === mediaKeySession) {
        log.debug("DRM", "Removing session without closing it", {
          sessionId: mediaKeySession.sessionId,
        });
        this._storage.splice(i, 1);
        return true;
      }
    }
    return false;
  }

  /**
   * Get the index of a stored MediaKeySession entry based on its
   * `KeySessionRecord`.
   * Returns -1 if not found.
   * @param {Object} record
   * @returns {number}
   */
  private getIndex(record: KeySessionRecord): number {
    for (let i = 0; i < this._storage.length; i++) {
      const stored = this._storage[i];
      if (stored.keySessionRecord === record) {
        return i;
      }
    }
    return -1;
  }

  /**
   * Prepare the closure of a `MediaKeySession` stored as an entry of the
   * `LoadedSessionsStore`.
   * Allows to postpone the closure action if another MediaKeySession action
   * is already pending.
   * @param {Object} entry
   * @returns {Promise.<boolean>}
   */
  private async _closeEntry(entry: IStoredSessionEntry): Promise<boolean> {
    const { mediaKeySession } = entry;
    return new Promise((resolve, reject) => {
      if (
        entry !== undefined &&
        (entry.isLoadingPersistentSession || entry.isGeneratingRequest)
      ) {
        entry.closingStatus = {
          type: "awaiting",
          start: tryClosingEntryAndResolve,
        };
      } else {
        tryClosingEntryAndResolve();
      }
      function tryClosingEntryAndResolve() {
        if (entry !== undefined) {
          entry.closingStatus = { type: "pending" };
        }
        safelyCloseMediaKeySession(mediaKeySession)
          .then(() => {
            if (entry !== undefined) {
              entry.closingStatus = { type: "done" };
            }
            resolve(true);
          })
          .catch((err) => {
            if (entry !== undefined) {
              entry.closingStatus = { type: "failed" };
            }
            reject(err);
          });
      }
    });
  }
}

/** Information linked to a `MediaKeySession` created by the `LoadedSessionsStore`. */
export interface IStoredSessionEntry {
  /**
   * The `KeySessionRecord` linked to the MediaKeySession.
   * It keeps track of all key ids that are currently known to be associated to
   * the MediaKeySession.
   *
   * Initially only assiociated with the initialization data given, you may want
   * to add to it other key ids if you find out that there are also linked to
   * that session.
   *
   * Regrouping all those key ids into the `KeySessionRecord` in that way allows
   * the `LoadedSessionsStore` to perform compatibility checks when future
   * initialization data is encountered.
   */
  keySessionRecord: KeySessionRecord;

  /** The MediaKeySession created. */
  mediaKeySession: IMediaKeySession;

  /**
   * The MediaKeySessionType (e.g. "temporary" or "persistent-license") with
   * which the MediaKeySession was created.
   */
  sessionType: MediaKeySessionType;

  /**
   * Set to `true` while a `generateRequest` call is pending.
   * This information might be useful as it is one of the operation we have to
   * wait for before closing a MediaKeySession.
   */
  isGeneratingRequest: boolean;

  /**
   * Set to `true` while a `load` call is pending.
   * This information might be useful as it is one of the operation we have to
   * wait for before closing a MediaKeySession.
   */
  isLoadingPersistentSession: boolean;

  /**
   * The status of a potential `MediaKeySession`'s close request.
   * Closing a MediaKeySession could be made complex as it normally cannot
   * happen until `generateRequest` or `load` has been called.
   *
   * To avoid problems while still staying compatible to the most devices
   * possible - which may have strange implementation of the specification -
   * we're adding the `closingStatus` property allowing to perform multiple
   * type of interaction while a close operation is either pending or is
   * awaited.
   */
  closingStatus: /** Status when the MediaKeySession is currently being closed. */
    | { type: "pending" }
    /** Status when the MediaKeySession has been closed. */
    | { type: "done" }
    /** Status when the MediaKeySession failed to close. */
    | { type: "failed" }
    /**
     * Status when a close order has been received for this MediaKeySession
     * while some sensitive operation (examples are `generateRequest` and `load`
     * calls).
     * The `LoadedSessionsStore` should call `start` once it has finished those
     * operations.
     */
    | {
        type: "awaiting";
        start: () => void;
      }
    /** Status when the MediaKeySession failed to close. */
    | { type: "none" };
}

/**
 * Close a MediaKeySession and just log an error if it fails (while resolving).
 * Emits then complete when done.
 * @param {MediaKeySession} mediaKeySession
 * @returns {Promise}
 */
async function safelyCloseMediaKeySession(
  mediaKeySession: IMediaKeySession,
): Promise<void> {
  const sessionId = mediaKeySession.sessionId;
  log.debug("DRM", "Trying to close a MediaKeySession", {
    sessionId,
  });
  try {
    await closeSession(mediaKeySession);
    log.debug("DRM", "Succeeded to close MediaKeySession", {
      sessionId,
    });
    return;
  } catch (err: unknown) {
    log.error(
      "DRM",
      "Could not close MediaKeySession: " +
        (err instanceof Error ? err.toString() : "Unknown error"),
      { sessionId },
    );
    return;
  }
}