/*
Copyright 2024 New Vector Ltd.
Copyright 2022 The Matrix.org Foundation C.I.C.

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

import {
    EventType,
    MatrixClient,
    MatrixEvent,
    MatrixEventEvent,
    MsgType,
    RelationType,
    TypedEventEmitter,
} from "matrix-js-sdk/src/matrix";
import { SimpleObservable } from "matrix-widget-api";
import { logger } from "matrix-js-sdk/src/logger";
import { defer, IDeferred } from "matrix-js-sdk/src/utils";

import { Playback, PlaybackInterface, PlaybackState } from "../../audio/Playback";
import { PlaybackManager } from "../../audio/PlaybackManager";
import { UPDATE_EVENT } from "../../stores/AsyncStore";
import { MediaEventHelper } from "../../utils/MediaEventHelper";
import { IDestroyable } from "../../utils/IDestroyable";
import {
    VoiceBroadcastLiveness,
    VoiceBroadcastInfoEventType,
    VoiceBroadcastInfoState,
    VoiceBroadcastInfoEventContent,
    VoiceBroadcastRecordingsStore,
    showConfirmListenBroadcastStopCurrentDialog,
} from "..";
import { RelationsHelper, RelationsHelperEvent } from "../../events/RelationsHelper";
import { VoiceBroadcastChunkEvents } from "../utils/VoiceBroadcastChunkEvents";
import { determineVoiceBroadcastLiveness } from "../utils/determineVoiceBroadcastLiveness";
import { _t } from "../../languageHandler";

export enum VoiceBroadcastPlaybackState {
    Paused = "pause",
    Playing = "playing",
    Stopped = "stopped",
    Buffering = "buffering",
    Error = "error",
}

export enum VoiceBroadcastPlaybackEvent {
    TimesChanged = "times_changed",
    LivenessChanged = "liveness_changed",
    StateChanged = "state_changed",
    InfoStateChanged = "info_state_changed",
}

export type VoiceBroadcastPlaybackTimes = {
    duration: number;
    position: number;
    timeLeft: number;
};

interface EventMap {
    [VoiceBroadcastPlaybackEvent.TimesChanged]: (times: VoiceBroadcastPlaybackTimes) => void;
    [VoiceBroadcastPlaybackEvent.LivenessChanged]: (liveness: VoiceBroadcastLiveness) => void;
    [VoiceBroadcastPlaybackEvent.StateChanged]: (
        state: VoiceBroadcastPlaybackState,
        playback: VoiceBroadcastPlayback,
    ) => void;
    [VoiceBroadcastPlaybackEvent.InfoStateChanged]: (state: VoiceBroadcastInfoState) => void;
}

export class VoiceBroadcastPlayback
    extends TypedEventEmitter<VoiceBroadcastPlaybackEvent, EventMap>
    implements IDestroyable, PlaybackInterface
{
    private state = VoiceBroadcastPlaybackState.Stopped;
    private chunkEvents = new VoiceBroadcastChunkEvents();
    /** @var Map: event Id → undecryptable event */
    private utdChunkEvents: Map<string, MatrixEvent> = new Map();
    private playbacks = new Map<string, Playback>();
    private currentlyPlaying: MatrixEvent | null = null;
    /** @var total duration of all chunks in milliseconds */
    private duration = 0;
    /** @var current playback position in milliseconds */
    private position = 0;
    public readonly liveData = new SimpleObservable<number[]>();
    private liveness: VoiceBroadcastLiveness = "not-live";

    // set via addInfoEvent() in constructor
    private infoState!: VoiceBroadcastInfoState;
    private lastInfoEvent!: MatrixEvent;

    // set via setUpRelationsHelper() in constructor
    private chunkRelationHelper!: RelationsHelper;
    private infoRelationHelper!: RelationsHelper;

    private skipToNext?: number;
    private skipToDeferred?: IDeferred<void>;

    public constructor(
        public readonly infoEvent: MatrixEvent,
        private client: MatrixClient,
        private recordings: VoiceBroadcastRecordingsStore,
    ) {
        super();
        this.addInfoEvent(this.infoEvent);
        this.infoEvent.on(MatrixEventEvent.BeforeRedaction, this.onBeforeRedaction);
        this.setUpRelationsHelper();
    }

    private async setUpRelationsHelper(): Promise<void> {
        this.infoRelationHelper = new RelationsHelper(
            this.infoEvent,
            RelationType.Reference,
            VoiceBroadcastInfoEventType,
            this.client,
        );
        this.infoRelationHelper.getCurrent().forEach(this.addInfoEvent);

        if (this.infoState !== VoiceBroadcastInfoState.Stopped) {
            // Only required if not stopped. Stopped is the final state.
            this.infoRelationHelper.on(RelationsHelperEvent.Add, this.addInfoEvent);

            try {
                await this.infoRelationHelper.emitFetchCurrent();
            } catch (err) {
                logger.warn("error fetching server side relation for voice broadcast info", err);
                // fall back to local events
                this.infoRelationHelper.emitCurrent();
            }
        }

        this.chunkRelationHelper = new RelationsHelper(
            this.infoEvent,
            RelationType.Reference,
            EventType.RoomMessage,
            this.client,
        );
        this.chunkRelationHelper.on(RelationsHelperEvent.Add, this.addChunkEvent);

        try {
            // TODO Michael W: only fetch events if needed, blocked by PSF-1708
            await this.chunkRelationHelper.emitFetchCurrent();
        } catch (err) {
            logger.warn("error fetching server side relation for voice broadcast chunks", err);
            // fall back to local events
            this.chunkRelationHelper.emitCurrent();
        }
    }

    private addChunkEvent = async (event: MatrixEvent): Promise<boolean> => {
        if (!event.getId() && !event.getTxnId()) {
            // skip events without id and txn id
            return false;
        }

        if (event.isDecryptionFailure()) {
            this.onChunkEventDecryptionFailure(event);
            return false;
        }

        if (event.getContent()?.msgtype !== MsgType.Audio) {
            // skip non-audio event
            return false;
        }

        this.chunkEvents.addEvent(event);
        this.setDuration(this.chunkEvents.getLength());

        if (this.getState() === VoiceBroadcastPlaybackState.Buffering) {
            await this.startOrPlayNext();
        }

        return true;
    };

    private onChunkEventDecryptionFailure = (event: MatrixEvent): void => {
        const eventId = event.getId();

        if (!eventId) {
            // This should not happen, as the existence of the Id is checked before the call.
            // Log anyway and return.
            logger.warn("Broadcast chunk decryption failure for event without Id", {
                broadcast: this.infoEvent.getId(),
            });
            return;
        }

        if (!this.utdChunkEvents.has(eventId)) {
            event.once(MatrixEventEvent.Decrypted, this.onChunkEventDecrypted);
        }

        this.utdChunkEvents.set(eventId, event);
        this.setError();
    };

    private onChunkEventDecrypted = async (event: MatrixEvent): Promise<void> => {
        const eventId = event.getId();

        if (!eventId) {
            // This should not happen, as the existence of the Id is checked before the call.
            // Log anyway and return.
            logger.warn("Broadcast chunk decrypted for event without Id", { broadcast: this.infoEvent.getId() });
            return;
        }

        this.utdChunkEvents.delete(eventId);
        await this.addChunkEvent(event);

        if (this.utdChunkEvents.size === 0) {
            // no more UTD events, recover from error to paused
            this.setState(VoiceBroadcastPlaybackState.Paused);
        }
    };

    private startOrPlayNext = async (): Promise<void> => {
        if (this.currentlyPlaying) {
            return this.playNext();
        }

        return await this.start();
    };

    private addInfoEvent = (event: MatrixEvent): void => {
        if (this.lastInfoEvent && this.lastInfoEvent.getTs() >= event.getTs()) {
            // Only handle newer events
            return;
        }

        const state = event.getContent()?.state;

        if (!Object.values(VoiceBroadcastInfoState).includes(state)) {
            // Do not handle unknown voice broadcast states
            return;
        }

        this.lastInfoEvent = event;
        this.setInfoState(state);
    };

    private onBeforeRedaction = (): void => {
        if (this.getState() !== VoiceBroadcastPlaybackState.Stopped) {
            this.stop();
            // destroy cleans up everything
            this.destroy();
        }
    };

    private async tryLoadPlayback(chunkEvent: MatrixEvent): Promise<void> {
        try {
            return await this.loadPlayback(chunkEvent);
        } catch (err: any) {
            logger.warn("Unable to load broadcast playback", {
                message: err.message,
                broadcastId: this.infoEvent.getId(),
                chunkId: chunkEvent.getId(),
            });
            this.setError();
        }
    }

    private async loadPlayback(chunkEvent: MatrixEvent): Promise<void> {
        const eventId = chunkEvent.getId();

        if (!eventId) {
            throw new Error("Broadcast chunk event without Id occurred");
        }

        const helper = new MediaEventHelper(chunkEvent);
        const blob = await helper.sourceBlob.value;
        const buffer = await blob.arrayBuffer();
        const playback = PlaybackManager.instance.createPlaybackInstance(buffer);
        await playback.prepare();
        playback.clockInfo.populatePlaceholdersFrom(chunkEvent);
        this.playbacks.set(eventId, playback);
        playback.on(UPDATE_EVENT, (state) => this.onPlaybackStateChange(chunkEvent, state));
        playback.clockInfo.liveData.onUpdate(([position]) => {
            this.onPlaybackPositionUpdate(chunkEvent, position);
        });
    }

    private unloadPlayback(event: MatrixEvent): void {
        const playback = this.playbacks.get(event.getId()!);
        if (!playback) return;

        playback.destroy();
        this.playbacks.delete(event.getId()!);
    }

    private onPlaybackPositionUpdate = (event: MatrixEvent, position: number): void => {
        if (event !== this.currentlyPlaying) return;

        const newPosition = this.chunkEvents.getLengthTo(event) + position * 1000; // observable sends seconds

        // do not jump backwards - this can happen when transiting from one to another chunk
        if (newPosition < this.position) return;

        this.setPosition(newPosition);
    };

    private setDuration(duration: number): void {
        if (this.duration === duration) return;

        this.duration = duration;
        this.emitTimesChanged();
        this.liveData.update([this.timeSeconds, this.durationSeconds]);
    }

    private setPosition(position: number): void {
        if (this.position === position) return;

        this.position = position;
        this.emitTimesChanged();
        this.liveData.update([this.timeSeconds, this.durationSeconds]);
    }

    private emitTimesChanged(): void {
        this.emit(VoiceBroadcastPlaybackEvent.TimesChanged, {
            duration: this.durationSeconds,
            position: this.timeSeconds,
            timeLeft: this.timeLeftSeconds,
        });
    }

    private onPlaybackStateChange = async (event: MatrixEvent, newState: PlaybackState): Promise<void> => {
        if (event !== this.currentlyPlaying) return;
        if (newState !== PlaybackState.Stopped) return;

        await this.playNext();
        this.unloadPlayback(event);
    };

    private async playNext(): Promise<void> {
        if (!this.currentlyPlaying) return;

        const next = this.chunkEvents.getNext(this.currentlyPlaying);

        if (next) {
            return this.playEvent(next);
        }

        if (
            this.getInfoState() === VoiceBroadcastInfoState.Stopped &&
            this.chunkEvents.getSequenceForEvent(this.currentlyPlaying) === this.lastChunkSequence
        ) {
            this.stop();
        } else {
            // No more chunks available, although the broadcast is not finished → enter buffering state.
            this.setState(VoiceBroadcastPlaybackState.Buffering);
        }
    }

    /**
     * @returns {number} The last chunk sequence from the latest info event.
     *                   Falls back to the length of received chunks if the info event does not provide the number.
     */
    private get lastChunkSequence(): number {
        return (
            this.lastInfoEvent.getContent<VoiceBroadcastInfoEventContent>()?.last_chunk_sequence ||
            this.chunkEvents.getNumberOfEvents()
        );
    }

    private async playEvent(event: MatrixEvent): Promise<void> {
        this.setState(VoiceBroadcastPlaybackState.Playing);
        this.currentlyPlaying = event;
        const playback = await this.tryGetOrLoadPlaybackForEvent(event);
        playback?.play();
    }

    private async tryGetOrLoadPlaybackForEvent(event: MatrixEvent): Promise<Playback | undefined> {
        try {
            return await this.getOrLoadPlaybackForEvent(event);
        } catch (err: any) {
            logger.warn("Unable to load broadcast playback", {
                message: err.message,
                broadcastId: this.infoEvent.getId(),
                chunkId: event.getId(),
            });
            this.setError();
        }
    }

    private async getOrLoadPlaybackForEvent(event: MatrixEvent): Promise<Playback | undefined> {
        const eventId = event.getId();

        if (!eventId) {
            throw new Error("Broadcast chunk event without Id occurred");
        }

        if (!this.playbacks.has(eventId)) {
            // set to buffering while loading the chunk data
            const currentState = this.getState();
            this.setState(VoiceBroadcastPlaybackState.Buffering);
            await this.loadPlayback(event);
            this.setState(currentState);
        }

        const playback = this.playbacks.get(eventId);

        if (!playback) {
            throw new Error(`Unable to find playback for event ${event.getId()}`);
        }

        // try to load the playback for the next event for a smooth(er) playback
        const nextEvent = this.chunkEvents.getNext(event);
        if (nextEvent) this.tryLoadPlayback(nextEvent);

        return playback;
    }

    private getCurrentPlayback(): Playback | undefined {
        if (!this.currentlyPlaying) return;
        return this.playbacks.get(this.currentlyPlaying.getId()!);
    }

    public getLiveness(): VoiceBroadcastLiveness {
        return this.liveness;
    }

    private setLiveness(liveness: VoiceBroadcastLiveness): void {
        if (this.liveness === liveness) return;

        this.liveness = liveness;
        this.emit(VoiceBroadcastPlaybackEvent.LivenessChanged, liveness);
    }

    public get currentState(): PlaybackState {
        return PlaybackState.Playing;
    }

    public get timeSeconds(): number {
        return this.position / 1000;
    }

    public get durationSeconds(): number {
        return this.duration / 1000;
    }

    public get timeLeftSeconds(): number {
        // Sometimes the meta data and the audio files are a little bit out of sync.
        // Be sure it never returns a negative value.
        return Math.max(0, Math.round(this.durationSeconds) - this.timeSeconds);
    }

    public async skipTo(timeSeconds: number): Promise<void> {
        this.skipToNext = timeSeconds;

        if (this.skipToDeferred) {
            // Skip to position is already in progress. Return the promise for that.
            return this.skipToDeferred.promise;
        }

        this.skipToDeferred = defer();

        while (this.skipToNext !== undefined) {
            // Skip to position until skipToNext is undefined.
            // skipToNext can be set if skipTo is called while already skipping.
            const skipToNext = this.skipToNext;
            this.skipToNext = undefined;
            await this.doSkipTo(skipToNext);
        }

        this.skipToDeferred.resolve();
        this.skipToDeferred = undefined;
    }

    private async doSkipTo(timeSeconds: number): Promise<void> {
        const time = timeSeconds * 1000;
        const event = this.chunkEvents.findByTime(time);

        if (!event) {
            logger.warn("voice broadcast chunk event to skip to not found");
            return;
        }

        const currentPlayback = this.getCurrentPlayback();
        const skipToPlayback = await this.tryGetOrLoadPlaybackForEvent(event);
        const currentPlaybackEvent = this.currentlyPlaying;

        if (!skipToPlayback) {
            logger.warn("voice broadcast chunk to skip to not found", event);
            return;
        }

        this.currentlyPlaying = event;

        if (currentPlayback && currentPlaybackEvent && currentPlayback !== skipToPlayback) {
            // only stop and unload the playback here without triggering other effects, e.g. play next
            currentPlayback.off(UPDATE_EVENT, this.onPlaybackStateChange);
            await currentPlayback.stop();
            currentPlayback.on(UPDATE_EVENT, this.onPlaybackStateChange);
            this.unloadPlayback(currentPlaybackEvent);
        }

        const offsetInChunk = time - this.chunkEvents.getLengthTo(event);
        await skipToPlayback.skipTo(offsetInChunk / 1000);

        if (this.state === VoiceBroadcastPlaybackState.Playing && !skipToPlayback.isPlaying) {
            await skipToPlayback.play();
        }

        this.setPosition(time);
    }

    public async start(): Promise<void> {
        if (this.state === VoiceBroadcastPlaybackState.Playing) return;

        const currentRecording = this.recordings.getCurrent();

        if (currentRecording && currentRecording.getState() !== VoiceBroadcastInfoState.Stopped) {
            const shouldStopRecording = await showConfirmListenBroadcastStopCurrentDialog();

            if (!shouldStopRecording) {
                // keep recording
                return;
            }

            await this.recordings.getCurrent()?.stop();
        }

        const chunkEvents = this.chunkEvents.getEvents();

        const toPlay =
            this.getInfoState() === VoiceBroadcastInfoState.Stopped
                ? chunkEvents[0] // start at the beginning for an ended voice broadcast
                : chunkEvents[chunkEvents.length - 1]; // start at the current chunk for an ongoing voice broadcast

        if (toPlay) {
            return this.playEvent(toPlay);
        }

        this.setState(VoiceBroadcastPlaybackState.Buffering);
    }

    public stop(): void {
        // error is a final state
        if (this.getState() === VoiceBroadcastPlaybackState.Error) return;

        this.setState(VoiceBroadcastPlaybackState.Stopped);
        this.getCurrentPlayback()?.stop();
        this.currentlyPlaying = null;
        this.setPosition(0);
    }

    public pause(): void {
        // error is a final state
        if (this.getState() === VoiceBroadcastPlaybackState.Error) return;

        // stopped voice broadcasts cannot be paused
        if (this.getState() === VoiceBroadcastPlaybackState.Stopped) return;

        this.setState(VoiceBroadcastPlaybackState.Paused);
        this.getCurrentPlayback()?.pause();
    }

    public resume(): void {
        // error is a final state
        if (this.getState() === VoiceBroadcastPlaybackState.Error) return;

        if (!this.currentlyPlaying) {
            // no playback to resume, start from the beginning
            this.start();
            return;
        }

        this.setState(VoiceBroadcastPlaybackState.Playing);
        this.getCurrentPlayback()?.play();
    }

    /**
     * Toggles the playback:
     * stopped → playing
     * playing → paused
     * paused → playing
     */
    public async toggle(): Promise<void> {
        // error is a final state
        if (this.getState() === VoiceBroadcastPlaybackState.Error) return;

        if (this.state === VoiceBroadcastPlaybackState.Stopped) {
            await this.start();
            return;
        }

        if (this.state === VoiceBroadcastPlaybackState.Paused) {
            this.resume();
            return;
        }

        this.pause();
    }

    public getState(): VoiceBroadcastPlaybackState {
        return this.state;
    }

    private setState(state: VoiceBroadcastPlaybackState): void {
        if (this.state === state) {
            return;
        }

        this.state = state;
        this.emit(VoiceBroadcastPlaybackEvent.StateChanged, state, this);
    }

    /**
     * Set error state. Stop current playback, if any.
     */
    private setError(): void {
        this.setState(VoiceBroadcastPlaybackState.Error);
        this.getCurrentPlayback()?.stop();
        this.currentlyPlaying = null;
        this.setPosition(0);
    }

    public getInfoState(): VoiceBroadcastInfoState {
        return this.infoState;
    }

    private setInfoState(state: VoiceBroadcastInfoState): void {
        if (this.infoState === state) {
            return;
        }

        this.infoState = state;
        this.emit(VoiceBroadcastPlaybackEvent.InfoStateChanged, state);
        this.setLiveness(determineVoiceBroadcastLiveness(this.infoState));
    }

    public get errorMessage(): string {
        if (this.getState() !== VoiceBroadcastPlaybackState.Error) return "";
        if (this.utdChunkEvents.size) return _t("voice_broadcast|failed_decrypt");
        return _t("voice_broadcast|failed_generic");
    }

    public destroy(): void {
        for (const [, utdEvent] of this.utdChunkEvents) {
            utdEvent.off(MatrixEventEvent.Decrypted, this.onChunkEventDecrypted);
        }

        this.utdChunkEvents.clear();

        this.chunkRelationHelper.destroy();
        this.infoRelationHelper.destroy();
        this.removeAllListeners();

        this.chunkEvents = new VoiceBroadcastChunkEvents();
        this.playbacks.forEach((p) => p.destroy());
        this.playbacks = new Map<string, Playback>();
    }
}