/*
Copyright 2023, 2024 New Vector Ltd.

SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE in the repository root for full details.
*/

import {
  type AudioSource,
  type TrackReferenceOrPlaceholder,
  type VideoSource,
  observeParticipantEvents,
  observeParticipantMedia,
  roomEventSelector,
} from "@livekit/components-core";
import {
  type LocalParticipant,
  LocalTrack,
  type Participant,
  ParticipantEvent,
  type RemoteParticipant,
  Track,
  TrackEvent,
  facingModeFromLocalTrack,
  type Room as LivekitRoom,
  RoomEvent as LivekitRoomEvent,
  RemoteTrack,
} from "livekit-client";
import { type RoomMember } from "matrix-js-sdk";
import {
  BehaviorSubject,
  type Observable,
  Subject,
  combineLatest,
  distinctUntilKeyChanged,
  filter,
  fromEvent,
  interval,
  map,
  merge,
  of,
  startWith,
  switchMap,
  throttleTime,
} from "rxjs";

import { ViewModel } from "./ViewModel";
import { alwaysShowSelf } from "../settings/settings";
import { showConnectionStats } from "../settings/settings";
import { accumulate } from "../utils/observable";
import { type EncryptionSystem } from "../e2ee/sharedKeyManagement";
import { E2eeType } from "../e2ee/e2eeType";
import { type ReactionOption } from "../reactions";

export function observeTrackReference$(
  participant$: Observable<Participant | undefined>,
  source: Track.Source,
): Observable<TrackReferenceOrPlaceholder | undefined> {
  return participant$.pipe(
    switchMap((p) => {
      if (p) {
        return observeParticipantMedia(p).pipe(
          map(() => ({
            participant: p,
            publication: p.getTrackPublication(source),
            source,
          })),
          distinctUntilKeyChanged("publication"),
        );
      } else {
        return of(undefined);
      }
    }),
  );
}

export function observeRtpStreamStats$(
  participant: Participant,
  source: Track.Source,
  type: "inbound-rtp" | "outbound-rtp",
): Observable<
  RTCInboundRtpStreamStats | RTCOutboundRtpStreamStats | undefined
> {
  return combineLatest([
    observeTrackReference$(of(participant), source),
    interval(1000).pipe(startWith(0)),
  ]).pipe(
    switchMap(async ([trackReference]) => {
      const track = trackReference?.publication?.track;
      if (
        !track ||
        !(track instanceof RemoteTrack || track instanceof LocalTrack)
      ) {
        return undefined;
      }
      const report = await track.getRTCStatsReport();
      if (!report) {
        return undefined;
      }

      for (const v of report.values()) {
        if (v.type === type) {
          return v;
        }
      }

      return undefined;
    }),
    startWith(undefined),
  );
}

export function observeInboundRtpStreamStats$(
  participant: Participant,
  source: Track.Source,
): Observable<RTCInboundRtpStreamStats | undefined> {
  return observeRtpStreamStats$(participant, source, "inbound-rtp").pipe(
    map((x) => x as RTCInboundRtpStreamStats | undefined),
  );
}

export function observeOutboundRtpStreamStats$(
  participant: Participant,
  source: Track.Source,
): Observable<RTCOutboundRtpStreamStats | undefined> {
  return observeRtpStreamStats$(participant, source, "outbound-rtp").pipe(
    map((x) => x as RTCOutboundRtpStreamStats | undefined),
  );
}

function observeRemoteTrackReceivingOkay$(
  participant: Participant,
  source: Track.Source,
): Observable<boolean | undefined> {
  let lastStats: {
    framesDecoded: number | undefined;
    framesDropped: number | undefined;
    framesReceived: number | undefined;
  } = {
    framesDecoded: undefined,
    framesDropped: undefined,
    framesReceived: undefined,
  };

  return observeInboundRtpStreamStats$(participant, source).pipe(
    map((stats) => {
      if (!stats) return undefined;
      const { framesDecoded, framesDropped, framesReceived } = stats;
      return {
        framesDecoded,
        framesDropped,
        framesReceived,
      };
    }),
    filter((newStats) => !!newStats),
    map((newStats): boolean | undefined => {
      const oldStats = lastStats;
      lastStats = newStats;
      if (
        typeof newStats.framesReceived === "number" &&
        typeof oldStats.framesReceived === "number" &&
        typeof newStats.framesDecoded === "number" &&
        typeof oldStats.framesDecoded === "number"
      ) {
        const framesReceivedDelta =
          newStats.framesReceived - oldStats.framesReceived;
        const framesDecodedDelta =
          newStats.framesDecoded - oldStats.framesDecoded;

        // if we received >0 frames and managed to decode >0 frames then we treat that as success

        if (framesReceivedDelta > 0) {
          return framesDecodedDelta > 0;
        }
      }

      // no change
      return undefined;
    }),
    filter((x) => typeof x === "boolean"),
    startWith(undefined),
  );
}

function encryptionErrorObservable$(
  room: LivekitRoom,
  participant: Participant,
  encryptionSystem: EncryptionSystem,
  criteria: string,
): Observable<boolean> {
  return roomEventSelector(room, LivekitRoomEvent.EncryptionError).pipe(
    map((e) => {
      const [err] = e;
      if (encryptionSystem.kind === E2eeType.PER_PARTICIPANT) {
        return (
          // Ideally we would pull the participant identity from the field on the error.
          // However, it gets lost in the serialization process between workers.
          // So, instead we do a string match
          (err?.message.includes(participant.identity) &&
            err?.message.includes(criteria)) ??
          false
        );
      } else if (encryptionSystem.kind === E2eeType.SHARED_KEY) {
        return !!err?.message.includes(criteria);
      }

      return false;
    }),
    throttleTime(1000), // Throttle to avoid spamming the UI
    startWith(false),
  );
}

export enum EncryptionStatus {
  Connecting,
  Okay,
  KeyMissing,
  KeyInvalid,
  PasswordInvalid,
}

abstract class BaseMediaViewModel extends ViewModel {
  /**
   * The LiveKit video track for this media.
   */
  public readonly video$: Observable<TrackReferenceOrPlaceholder | undefined>;
  /**
   * Whether there should be a warning that this media is unencrypted.
   */
  public readonly unencryptedWarning$: Observable<boolean>;

  public readonly encryptionStatus$: Observable<EncryptionStatus>;

  /**
   * Whether this media corresponds to the local participant.
   */
  public abstract readonly local: boolean;

  public constructor(
    /**
     * An opaque identifier for this media.
     */
    public readonly id: string,
    /**
     * The Matrix room member to which this media belongs.
     */
    // TODO: Fully separate the data layer from the UI layer by keeping the
    // member object internal
    public readonly member: RoomMember | undefined,
    // We don't necessarily have a participant if a user connects via MatrixRTC but not (yet) through
    // livekit.
    protected readonly participant$: Observable<
      LocalParticipant | RemoteParticipant | undefined
    >,

    encryptionSystem: EncryptionSystem,
    audioSource: AudioSource,
    videoSource: VideoSource,
    livekitRoom: LivekitRoom,
    public readonly displayname$: Observable<string>,
  ) {
    super();
    const audio$ = observeTrackReference$(participant$, audioSource).pipe(
      this.scope.state(),
    );
    this.video$ = observeTrackReference$(participant$, videoSource).pipe(
      this.scope.state(),
    );
    this.unencryptedWarning$ = combineLatest(
      [audio$, this.video$],
      (a, v) =>
        encryptionSystem.kind !== E2eeType.NONE &&
        (a?.publication?.isEncrypted === false ||
          v?.publication?.isEncrypted === false),
    ).pipe(this.scope.state());

    this.encryptionStatus$ = this.participant$.pipe(
      switchMap((participant): Observable<EncryptionStatus> => {
        if (!participant) {
          return of(EncryptionStatus.Connecting);
        } else if (
          participant.isLocal ||
          encryptionSystem.kind === E2eeType.NONE
        ) {
          return of(EncryptionStatus.Okay);
        } else if (encryptionSystem.kind === E2eeType.PER_PARTICIPANT) {
          return combineLatest([
            encryptionErrorObservable$(
              livekitRoom,
              participant,
              encryptionSystem,
              "MissingKey",
            ),
            encryptionErrorObservable$(
              livekitRoom,
              participant,
              encryptionSystem,
              "InvalidKey",
            ),
            observeRemoteTrackReceivingOkay$(participant, audioSource),
            observeRemoteTrackReceivingOkay$(participant, videoSource),
          ]).pipe(
            map(([keyMissing, keyInvalid, audioOkay, videoOkay]) => {
              if (keyMissing) return EncryptionStatus.KeyMissing;
              if (keyInvalid) return EncryptionStatus.KeyInvalid;
              if (audioOkay || videoOkay) return EncryptionStatus.Okay;
              return undefined; // no change
            }),
            filter((x) => !!x),
            startWith(EncryptionStatus.Connecting),
          );
        } else {
          return combineLatest([
            encryptionErrorObservable$(
              livekitRoom,
              participant,
              encryptionSystem,
              "InvalidKey",
            ),
            observeRemoteTrackReceivingOkay$(participant, audioSource),
            observeRemoteTrackReceivingOkay$(participant, videoSource),
          ]).pipe(
            map(
              ([keyInvalid, audioOkay, videoOkay]):
                | EncryptionStatus
                | undefined => {
                if (keyInvalid) return EncryptionStatus.PasswordInvalid;
                if (audioOkay || videoOkay) return EncryptionStatus.Okay;
                return undefined; // no change
              },
            ),
            filter((x) => !!x),
            startWith(EncryptionStatus.Connecting),
          );
        }
      }),
      this.scope.state(),
    );
  }
}

/**
 * Some participant's media.
 */
export type MediaViewModel = UserMediaViewModel | ScreenShareViewModel;
export type UserMediaViewModel =
  | LocalUserMediaViewModel
  | RemoteUserMediaViewModel;

/**
 * Some participant's user media.
 */
abstract class BaseUserMediaViewModel extends BaseMediaViewModel {
  /**
   * Whether the participant is speaking.
   */
  public readonly speaking$ = this.participant$.pipe(
    switchMap((p) =>
      p
        ? observeParticipantEvents(p, ParticipantEvent.IsSpeakingChanged).pipe(
            map((p) => p.isSpeaking),
          )
        : of(false),
    ),
    this.scope.state(),
  );

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

  private readonly _cropVideo$ = new BehaviorSubject(true);
  /**
   * Whether the tile video should be contained inside the tile or be cropped to fit.
   */
  public readonly cropVideo$: Observable<boolean> = this._cropVideo$;

  public constructor(
    id: string,
    member: RoomMember | undefined,
    participant$: Observable<LocalParticipant | RemoteParticipant | undefined>,
    encryptionSystem: EncryptionSystem,
    livekitRoom: LivekitRoom,
    displayname$: Observable<string>,
    public readonly handRaised$: Observable<Date | null>,
    public readonly reaction$: Observable<ReactionOption | null>,
  ) {
    super(
      id,
      member,
      participant$,
      encryptionSystem,
      Track.Source.Microphone,
      Track.Source.Camera,
      livekitRoom,
      displayname$,
    );

    const media$ = participant$.pipe(
      switchMap((p) => (p && observeParticipantMedia(p)) ?? of(undefined)),
      this.scope.state(),
    );
    this.audioEnabled$ = media$.pipe(
      map((m) => m?.microphoneTrack?.isMuted === false),
    );
    this.videoEnabled$ = media$.pipe(
      map((m) => m?.cameraTrack?.isMuted === false),
    );
  }

  public toggleFitContain(): void {
    this._cropVideo$.next(!this._cropVideo$.value);
  }

  public get local(): boolean {
    return this instanceof LocalUserMediaViewModel;
  }

  public abstract get audioStreamStats$(): Observable<
    RTCInboundRtpStreamStats | RTCOutboundRtpStreamStats | undefined
  >;
  public abstract get videoStreamStats$(): Observable<
    RTCInboundRtpStreamStats | RTCOutboundRtpStreamStats | undefined
  >;
}

/**
 * The local participant's user media.
 */
export class LocalUserMediaViewModel extends BaseUserMediaViewModel {
  /**
   * Whether the video should be mirrored.
   */
  public readonly mirror$ = 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"),
      );
    }),
    this.scope.state(),
  );

  /**
   * Whether to show this tile in a highly visible location near the start of
   * the grid.
   */
  public readonly alwaysShow$ = alwaysShowSelf.value$;
  public readonly setAlwaysShow = alwaysShowSelf.setValue;

  public constructor(
    id: string,
    member: RoomMember | undefined,
    participant$: Observable<LocalParticipant | undefined>,
    encryptionSystem: EncryptionSystem,
    livekitRoom: LivekitRoom,
    displayname$: Observable<string>,
    handRaised$: Observable<Date | null>,
    reaction$: Observable<ReactionOption | null>,
  ) {
    super(
      id,
      member,
      participant$,
      encryptionSystem,
      livekitRoom,
      displayname$,
      handRaised$,
      reaction$,
    );
  }

  public audioStreamStats$ = combineLatest([
    this.participant$,
    showConnectionStats.value$,
  ]).pipe(
    switchMap(([p, showConnectionStats]) => {
      if (!p || !showConnectionStats) return of(undefined);
      return observeOutboundRtpStreamStats$(p, Track.Source.Microphone);
    }),
  );

  public videoStreamStats$ = combineLatest([
    this.participant$,
    showConnectionStats.value$,
  ]).pipe(
    switchMap(([p, showConnectionStats]) => {
      if (!p || !showConnectionStats) return of(undefined);
      return observeOutboundRtpStreamStats$(p, Track.Source.Camera);
    }),
  );
}

/**
 * A remote participant's user media.
 */
export class RemoteUserMediaViewModel extends BaseUserMediaViewModel {
  private readonly locallyMutedToggle$ = new Subject<void>();
  private readonly localVolumeAdjustment$ = new Subject<number>();
  private readonly localVolumeCommit$ = new Subject<void>();

  /**
   * The volume to which this participant's audio is set, as a scalar
   * multiplier.
   */
  public readonly localVolume$: Observable<number> = merge(
    this.locallyMutedToggle$.pipe(map(() => "toggle mute" as const)),
    this.localVolumeAdjustment$,
    this.localVolumeCommit$.pipe(map(() => "commit" as const)),
  ).pipe(
    accumulate({ volume: 1, committedVolume: 1 }, (state, event) => {
      switch (event) {
        case "toggle mute":
          return {
            ...state,
            volume: state.volume === 0 ? state.committedVolume : 0,
          };
        case "commit":
          // Dragging the slider to zero should have the same effect as
          // muting: keep the original committed volume, as if it were never
          // dragged
          return {
            ...state,
            committedVolume:
              state.volume === 0 ? state.committedVolume : state.volume,
          };
        default:
          // Volume adjustment
          return { ...state, volume: event };
      }
    }),
    map(({ volume }) => volume),
    this.scope.state(),
  );

  /**
   * Whether this participant's audio is disabled.
   */
  public readonly locallyMuted$: Observable<boolean> = this.localVolume$.pipe(
    map((volume) => volume === 0),
    this.scope.state(),
  );

  public constructor(
    id: string,
    member: RoomMember | undefined,
    participant$: Observable<RemoteParticipant | undefined>,
    encryptionSystem: EncryptionSystem,
    livekitRoom: LivekitRoom,
    displayname$: Observable<string>,
    handRaised$: Observable<Date | null>,
    reaction$: Observable<ReactionOption | null>,
  ) {
    super(
      id,
      member,
      participant$,
      encryptionSystem,
      livekitRoom,
      displayname$,
      handRaised$,
      reaction$,
    );

    // Sync the local volume with LiveKit
    combineLatest([
      participant$,
      this.localVolume$.pipe(this.scope.bind()),
    ]).subscribe(([p, volume]) => p && p.setVolume(volume));
  }

  public toggleLocallyMuted(): void {
    this.locallyMutedToggle$.next();
  }

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

  public commitLocalVolume(): void {
    this.localVolumeCommit$.next();
  }

  public audioStreamStats$ = combineLatest([
    this.participant$,
    showConnectionStats.value$,
  ]).pipe(
    switchMap(([p, showConnectionStats]) => {
      if (!p || !showConnectionStats) return of(undefined);
      return observeInboundRtpStreamStats$(p, Track.Source.Microphone);
    }),
  );

  public videoStreamStats$ = combineLatest([
    this.participant$,
    showConnectionStats.value$,
  ]).pipe(
    switchMap(([p, showConnectionStats]) => {
      if (!p || !showConnectionStats) return of(undefined);
      return observeInboundRtpStreamStats$(p, Track.Source.Camera);
    }),
  );
}

/**
 * Some participant's screen share media.
 */
export class ScreenShareViewModel extends BaseMediaViewModel {
  public constructor(
    id: string,
    member: RoomMember | undefined,
    participant$: Observable<LocalParticipant | RemoteParticipant>,
    encryptionSystem: EncryptionSystem,
    livekitRoom: LivekitRoom,
    displayname$: Observable<string>,
    public readonly local: boolean,
  ) {
    super(
      id,
      member,
      participant$,
      encryptionSystem,
      Track.Source.ScreenShareAudio,
      Track.Source.ScreenShare,
      livekitRoom,
      displayname$,
    );
  }
}