/*
Copyright 2018, 2019 New Vector Ltd
Copyright 2020 The Matrix.org Foundation C.I.C.

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 { MatrixClient } from "matrix-js-sdk/src/client";
import SettingsStore from "../../settings/SettingsStore";
import { DefaultTagID, OrderedDefaultTagIDs, RoomUpdateCause, TagID } from "./models";
import { Algorithm } from "./algorithms/list-ordering/Algorithm";
import TagOrderStore from "../TagOrderStore";
import { AsyncStore } from "../AsyncStore";
import { Room } from "matrix-js-sdk/src/models/room";
import { ITagMap, ITagSortingMap, ListAlgorithm, SortAlgorithm } from "./algorithms/models";
import { getListAlgorithmInstance } from "./algorithms/list-ordering";
import { ActionPayload } from "../../dispatcher/payloads";
import defaultDispatcher from "../../dispatcher/dispatcher";
import { readReceiptChangeIsFor } from "../../utils/read-receipts";

interface IState {
    tagsEnabled?: boolean;

    preferredSort?: SortAlgorithm;
    preferredAlgorithm?: ListAlgorithm;
}

/**
 * The event/channel which is called when the room lists have been changed. Raised
 * with one argument: the instance of the store.
 */
export const LISTS_UPDATE_EVENT = "lists_update";

class _RoomListStore extends AsyncStore<ActionPayload> {
    private matrixClient: MatrixClient;
    private initialListsGenerated = false;
    private enabled = false;
    private algorithm: Algorithm;

    private readonly watchedSettings = [
        'RoomList.orderAlphabetically',
        'RoomList.orderByImportance',
        'feature_custom_tags',
    ];

    constructor() {
        super(defaultDispatcher);

        this.checkEnabled();
        for (const settingName of this.watchedSettings) SettingsStore.monitorSetting(settingName, null);
    }

    public get orderedLists(): ITagMap {
        if (!this.algorithm) return {}; // No tags yet.
        return this.algorithm.getOrderedRooms();
    }

    // TODO: Remove enabled flag when the old RoomListStore goes away
    private checkEnabled() {
        this.enabled = SettingsStore.isFeatureEnabled("feature_new_room_list");
        if (this.enabled) {
            console.log("⚡ new room list store engaged");
        }
    }

    private async readAndCacheSettingsFromStore() {
        const tagsEnabled = SettingsStore.isFeatureEnabled("feature_custom_tags");
        const orderByImportance = SettingsStore.getValue("RoomList.orderByImportance");
        const orderAlphabetically = SettingsStore.getValue("RoomList.orderAlphabetically");
        await this.updateState({
            tagsEnabled,
            preferredSort: orderAlphabetically ? SortAlgorithm.Alphabetic : SortAlgorithm.Recent,
            preferredAlgorithm: orderByImportance ? ListAlgorithm.Importance : ListAlgorithm.Natural,
        });
        this.setAlgorithmClass();
    }

    protected async onDispatch(payload: ActionPayload) {
        if (payload.action === 'MatrixActions.sync') {
            // Filter out anything that isn't the first PREPARED sync.
            if (!(payload.prevState === 'PREPARED' && payload.state !== 'PREPARED')) {
                return;
            }

            // TODO: Remove this once the RoomListStore becomes default
            this.checkEnabled();
            if (!this.enabled) return;

            this.matrixClient = payload.matrixClient;

            // Update any settings here, as some may have happened before we were logically ready.
            console.log("Regenerating room lists: Startup");
            await this.readAndCacheSettingsFromStore();
            await this.regenerateAllLists();
        }

        // TODO: Remove this once the RoomListStore becomes default
        if (!this.enabled) return;

        if (payload.action === 'on_client_not_viable' || payload.action === 'on_logged_out') {
            // Reset state without causing updates as the client will have been destroyed
            // and downstream code will throw NPE errors.
            this.reset(null, true);
            this.matrixClient = null;
            this.initialListsGenerated = false; // we'll want to regenerate them
        }

        // Everything below here requires a MatrixClient or some sort of logical readiness.
        const logicallyReady = this.matrixClient && this.initialListsGenerated;
        if (!logicallyReady) return;

        if (payload.action === 'setting_updated') {
            if (this.watchedSettings.includes(payload.settingName)) {
                console.log("Regenerating room lists: Settings changed");
                await this.readAndCacheSettingsFromStore();

                await this.regenerateAllLists(); // regenerate the lists now
            }
        }

        if (!this.algorithm) {
            // This shouldn't happen because `initialListsGenerated` implies we have an algorithm.
            throw new Error("Room list store has no algorithm to process dispatcher update with");
        }

        if (payload.action === 'MatrixActions.Room.receipt') {
            // First see if the receipt event is for our own user. If it was, trigger
            // a room update (we probably read the room on a different device).
            if (readReceiptChangeIsFor(payload.event, this.matrixClient)) {
                // TODO: Update room now that it's been read
                console.log(payload);
                return;
            }
        } else if (payload.action === 'MatrixActions.Room.tags') {
            // TODO: Update room from tags
            console.log(payload);
        } else if (payload.action === 'MatrixActions.Room.timeline') {
            const eventPayload = (<any>payload); // TODO: Type out the dispatcher types

            // Ignore non-live events (backfill)
            if (!eventPayload.isLiveEvent || !payload.isLiveUnfilteredRoomTimelineEvent) return;

            const roomId = eventPayload.event.getRoomId();
            const room = this.matrixClient.getRoom(roomId);
            console.log(`[RoomListDebug] Live timeline event ${eventPayload.event.getId()} in ${roomId}`);
            await this.handleRoomUpdate(room, RoomUpdateCause.Timeline);
        } else if (payload.action === 'MatrixActions.Event.decrypted') {
            const eventPayload = (<any>payload); // TODO: Type out the dispatcher types
            const roomId = eventPayload.event.getRoomId();
            const room = this.matrixClient.getRoom(roomId);
            if (!room) {
                console.warn(`Event ${eventPayload.event.getId()} was decrypted in an unknown room ${roomId}`);
                return;
            }
            console.log(`[RoomListDebug] Decrypted timeline event ${eventPayload.event.getId()} in ${roomId}`);
            // TODO: Check that e2e rooms are calculated correctly on initial load.
            // It seems like when viewing the room the timeline is decrypted, rather than at startup. This could
            // cause inaccuracies with the list ordering. We may have to decrypt the last N messages of every room :(
            await this.handleRoomUpdate(room, RoomUpdateCause.Timeline);
        } else if (payload.action === 'MatrixActions.accountData' && payload.event_type === 'm.direct') {
            // TODO: Update DMs
            console.log(payload);
        } else if (payload.action === 'MatrixActions.Room.myMembership') {
            // TODO: Update room from membership change
            console.log(payload);
        } else if (payload.action === 'MatrixActions.Room') {
            // TODO: Update room from creation/join
            console.log(payload);
        } else if (payload.action === 'view_room') {
            // TODO: Update sticky room
            console.log(payload);
        }
    }

    private async handleRoomUpdate(room: Room, cause: RoomUpdateCause): Promise<any> {
        const shouldUpdate = await this.algorithm.handleRoomUpdate(room, cause);
        if (shouldUpdate) {
            console.log(`[DEBUG] Room "${room.name}" (${room.roomId}) triggered by ${cause} requires list update`);
            this.emit(LISTS_UPDATE_EVENT, this);
        }
    }

    private getSortAlgorithmFor(tagId: TagID): SortAlgorithm {
        switch (tagId) {
            case DefaultTagID.Invite:
            case DefaultTagID.Untagged:
            case DefaultTagID.Archived:
            case DefaultTagID.LowPriority:
            case DefaultTagID.DM:
                return this.state.preferredSort;
            case DefaultTagID.Favourite:
            default:
                return SortAlgorithm.Manual;
        }
    }

    protected async updateState(newState: IState) {
        if (!this.enabled) return;

        await super.updateState(newState);
    }

    private setAlgorithmClass() {
        this.algorithm = getListAlgorithmInstance(this.state.preferredAlgorithm);
    }

    private async regenerateAllLists() {
        console.warn("Regenerating all room lists");
        const tags: ITagSortingMap = {};
        for (const tagId of OrderedDefaultTagIDs) {
            tags[tagId] = this.getSortAlgorithmFor(tagId);
        }

        if (this.state.tagsEnabled) {
            // TODO: Find a more reliable way to get tags (this doesn't work)
            const roomTags = TagOrderStore.getOrderedTags() || [];
            console.log("rtags", roomTags);
        }

        await this.algorithm.populateTags(tags);
        await this.algorithm.setKnownRooms(this.matrixClient.getRooms());

        this.initialListsGenerated = true;

        this.emit(LISTS_UPDATE_EVENT, this);
    }
}

export default class RoomListStore {
    private static internalInstance: _RoomListStore;

    public static get instance(): _RoomListStore {
        if (!RoomListStore.internalInstance) {
            RoomListStore.internalInstance = new _RoomListStore();
        }

        return RoomListStore.internalInstance;
    }
}