/*
Copyright 2023 New Vector Ltd

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 {
  AudioSource,
  TrackReferenceOrPlaceholder,
  VideoSource,
  observeParticipantEvents,
  observeParticipantMedia,
} from "@livekit/components-core";
import { StateObservable, state } from "@react-rxjs/core";
import {
  LocalParticipant,
  LocalTrack,
  Participant,
  ParticipantEvent,
  RemoteParticipant,
  Track,
  TrackEvent,
  facingModeFromLocalTrack,
} from "livekit-client";
import { RoomMember } from "matrix-js-sdk/src/matrix";
import {
  BehaviorSubject,
  combineLatest,
  distinctUntilChanged,
  distinctUntilKeyChanged,
  fromEvent,
  map,
  of,
  startWith,
  switchMap,
  takeUntil,
} from "rxjs";

import { ViewModel } from "./ViewModel";

function observeTrackReference(
  participant: Participant,
  source: Track.Source,
): StateObservable<TrackReferenceOrPlaceholder> {
  return state(
    observeParticipantMedia(participant).pipe(
      map(() => ({
        participant,
        publication: participant.getTrack(source),
        source,
      })),
      distinctUntilKeyChanged("publication"),
    ),
  );
}

abstract class BaseTileViewModel extends ViewModel {
  /**
   * Whether the tile belongs to the local user.
   */
  public readonly local = this.participant.isLocal;
  /**
   * The LiveKit video track to be shown on this tile.
   */
  public readonly video: StateObservable<TrackReferenceOrPlaceholder>;
  /**
   * Whether there should be a warning that this media is unencrypted.
   */
  public readonly unencryptedWarning: StateObservable<boolean>;

  public constructor(
    // TODO: This is only needed for full screen toggling and can be removed as
    // soon as that code is moved into the view models
    public readonly id: string,
    /**
     * The Matrix room member to which this tile belongs.
     */
    // TODO: Fully separate the data layer from the UI layer by keeping the
    // member object internal
    public readonly member: RoomMember | undefined,
    protected readonly participant: LocalParticipant | RemoteParticipant,
    callEncrypted: boolean,
    audioSource: AudioSource,
    videoSource: VideoSource,
  ) {
    super();
    const audio = observeTrackReference(participant, audioSource);
    this.video = observeTrackReference(participant, videoSource);
    this.unencryptedWarning = state(
      combineLatest(
        [audio, this.video],
        (a, v) =>
          callEncrypted &&
          (a.publication?.isEncrypted === false ||
            v.publication?.isEncrypted === false),
      ).pipe(distinctUntilChanged()),
    );
  }
}

/**
 * A tile displaying some media.
 */
export type TileViewModel = UserMediaTileViewModel | ScreenShareTileViewModel;

/**
 * A tile displaying some participant's user media.
 */
export class UserMediaTileViewModel extends BaseTileViewModel {
  /**
   * Whether the video should be mirrored.
   */
  public readonly mirror = state(
    this.video.pipe(
      switchMap((v) => {
        const track = v.publication?.track;
        if (!(track instanceof LocalTrack)) return of(false);
        // Watch for track restarts, because they indicate a camera switch
        return fromEvent(track, TrackEvent.Restarted).pipe(
          startWith(null),
          // Mirror only front-facing cameras (those that face the user)
          map(() => facingModeFromLocalTrack(track).facingMode === "user"),
        );
      }),
    ),
  );

  /**
   * Whether the participant is speaking.
   */
  public readonly speaking = state(
    observeParticipantEvents(
      this.participant,
      ParticipantEvent.IsSpeakingChanged,
    ).pipe(map((p) => p.isSpeaking)),
  );

  private readonly _locallyMuted = new BehaviorSubject(false);
  /**
   * Whether we've disabled this participant's audio.
   */
  public readonly locallyMuted = state(this._locallyMuted);

  private readonly _localVolume = new BehaviorSubject(1);
  /**
   * The volume to which we've set this participant's audio, as a scalar
   * multiplier.
   */
  public readonly localVolume = state(this._localVolume);

  /**
   * Whether this participant is sending audio (i.e. is unmuted on their side).
   */
  public readonly audioEnabled: StateObservable<boolean>;
  /**
   * Whether this participant is sending video.
   */
  public readonly videoEnabled: StateObservable<boolean>;

  public constructor(
    id: string,
    member: RoomMember | undefined,
    participant: LocalParticipant | RemoteParticipant,
    callEncrypted: boolean,
  ) {
    super(
      id,
      member,
      participant,
      callEncrypted,
      Track.Source.Microphone,
      Track.Source.Camera,
    );

    const media = observeParticipantMedia(participant);
    this.audioEnabled = state(
      media.pipe(map((m) => m.microphoneTrack?.isMuted === false)),
    );
    this.videoEnabled = state(
      media.pipe(map((m) => m.cameraTrack?.isMuted === false)),
    );

    // Sync the local mute state and volume with LiveKit
    if (!this.local)
      combineLatest([this._locallyMuted, this._localVolume], (muted, volume) =>
        muted ? 0 : volume,
      )
        .pipe(takeUntil(this.destroyed))
        .subscribe((volume) => {
          (this.participant as RemoteParticipant).setVolume(volume);
        });
  }

  public toggleLocallyMuted(): void {
    this._locallyMuted.next(!this._locallyMuted.value);
  }

  public setLocalVolume(value: number): void {
    this._localVolume.next(value);
  }
}

/**
 * A tile displaying some participant's screen share.
 */
export class ScreenShareTileViewModel extends BaseTileViewModel {
  public constructor(
    id: string,
    member: RoomMember | undefined,
    participant: LocalParticipant | RemoteParticipant,
    callEncrypted: boolean,
  ) {
    super(
      id,
      member,
      participant,
      callEncrypted,
      Track.Source.ScreenShareAudio,
      Track.Source.ScreenShare,
    );
  }
}