/*
Copyright 2020 Bruno Windels <bruno@windels.cloud>

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 {EventEmitter} from "../../utils/EventEmitter.js";
import {RoomSummary} from "./RoomSummary.js";
import {SyncWriter} from "./timeline/persistence/SyncWriter.js";
import {GapWriter} from "./timeline/persistence/GapWriter.js";
import {readRawTimelineEntriesWithTxn} from "./timeline/persistence/TimelineReader.js";
import {Timeline} from "./timeline/Timeline.js";
import {FragmentIdComparer} from "./timeline/FragmentIdComparer.js";
import {SendQueue} from "./sending/SendQueue.js";
import {WrappedError} from "../error.js"
import {fetchOrLoadMembers} from "./members/load.js";
import {MemberList} from "./members/MemberList.js";
import {Heroes} from "./members/Heroes.js";
import {EventEntry} from "./timeline/entries/EventEntry.js";
import {EventKey} from "./timeline/EventKey.js";
import {Direction} from "./timeline/Direction.js";
import {DecryptionSource} from "../e2ee/common.js";

const EVENT_ENCRYPTED_TYPE = "m.room.encrypted";

export class Room extends EventEmitter {
    constructor({roomId, storage, hsApi, mediaRepository, emitCollectionChange, pendingEvents, user, createRoomEncryption, getSyncToken, clock}) {
        super();
        this._roomId = roomId;
        this._storage = storage;
        this._hsApi = hsApi;
        this._mediaRepository = mediaRepository;
        this._summary = new RoomSummary(roomId);
        this._fragmentIdComparer = new FragmentIdComparer([]);
        this._syncWriter = new SyncWriter({roomId, fragmentIdComparer: this._fragmentIdComparer});
        this._emitCollectionChange = emitCollectionChange;
        this._sendQueue = new SendQueue({roomId, storage, hsApi, pendingEvents});
        this._timeline = null;
        this._user = user;
        this._changedMembersDuringSync = null;
        this._memberList = null;
        this._createRoomEncryption = createRoomEncryption;
        this._roomEncryption = null;
        this._getSyncToken = getSyncToken;
        this._clock = clock;
    }

    _readRetryDecryptCandidateEntries(sinceEventKey, txn) {
        if (sinceEventKey) {
            return readRawTimelineEntriesWithTxn(this._roomId, sinceEventKey,
                Direction.Forward, Number.MAX_SAFE_INTEGER, this._fragmentIdComparer, txn);
        } else {
            // all messages for room ...
            // if you haven't decrypted any message in a room yet,
            // it's unlikely you will have tons of them.
            // so this should be fine as a last resort
            return readRawTimelineEntriesWithTxn(this._roomId, this._syncWriter.lastMessageKey,
                Direction.Backward, Number.MAX_SAFE_INTEGER, this._fragmentIdComparer, txn);
        }
    }

    async notifyRoomKey(roomKey) {
        if (!this._roomEncryption) {
            return;
        }
        const retryEventIds = this._roomEncryption.getEventIdsForRoomKey(roomKey);
        const stores = [
            this._storage.storeNames.timelineEvents,
            this._storage.storeNames.inboundGroupSessions,
        ];
        let txn;
        let retryEntries;
        if (retryEventIds) {
            retryEntries = [];
            txn = await this._storage.readTxn(stores);
            for (const eventId of retryEventIds) {
                const storageEntry = await txn.timelineEvents.getByEventId(this._roomId, eventId);
                if (storageEntry) {
                    retryEntries.push(new EventEntry(storageEntry, this._fragmentIdComparer));
                }
            }
        } else {
            // we only look for messages since lastDecryptedEventKey because
            // the timeline must be closed (otherwise getEventIdsForRoomKey would have found the event ids)
            // and to update the summary we only care about events since lastDecryptedEventKey
            const key = this._summary.data.lastDecryptedEventKey;
            // key might be missing if we haven't decrypted any events in this room
            const sinceEventKey = key && new EventKey(key.fragmentId, key.entryIndex);
            // check we have not already decrypted the most recent event in the room
            // otherwise we know that the messages for this room key will not update the room summary
            if (!sinceEventKey || !sinceEventKey.equals(this._syncWriter.lastMessageKey)) {
                txn = await this._storage.readTxn(stores.concat(this._storage.storeNames.timelineFragments));
                const candidateEntries = await this._readRetryDecryptCandidateEntries(sinceEventKey, txn);
                retryEntries = this._roomEncryption.findAndCacheEntriesForRoomKey(roomKey, candidateEntries);
            }
        }
        if (retryEntries?.length) {
            const decryptRequest = this._decryptEntries(DecryptionSource.Retry, retryEntries, txn);
            // this will close txn while awaiting decryption
            await decryptRequest.complete();

            this._timeline?.replaceEntries(retryEntries);
            // we would ideally write the room summary in the same txn as the groupSessionDecryptions in the
            // _decryptEntries entries and could even know which events have been decrypted for the first
            // time from DecryptionChanges.write and only pass those to the summary. As timeline changes
            // are not essential to the room summary, it's fine to write this in a separate txn for now.
            const changes = this._summary.data.applyTimelineEntries(retryEntries, false, false);
            if (await this._summary.writeAndApplyData(changes, this._storage)) {
                this._emitUpdate();
            }
        }
    }

    _setEncryption(roomEncryption) {
        if (roomEncryption && !this._roomEncryption) {
            this._roomEncryption = roomEncryption;
            this._sendQueue.enableEncryption(this._roomEncryption);
            if (this._timeline) {
                this._timeline.enableEncryption(this._decryptEntries.bind(this, DecryptionSource.Timeline));
            }
        }
    }

    /**
     * Used for decrypting when loading/filling the timeline, and retrying decryption,
     * not during sync, where it is split up during the multiple phases.
     */
    _decryptEntries(source, entries, inboundSessionTxn = null) {
        const request = new DecryptionRequest(async r => {
            if (!inboundSessionTxn) {
                inboundSessionTxn = await this._storage.readTxn([this._storage.storeNames.inboundGroupSessions]);
            }
            if (r.cancelled) return;
            const events = entries.filter(entry => {
                return entry.eventType === EVENT_ENCRYPTED_TYPE;
            }).map(entry => entry.event);
            const isTimelineOpen = this._isTimelineOpen;
            r.preparation = await this._roomEncryption.prepareDecryptAll(events, source, isTimelineOpen, inboundSessionTxn);
            if (r.cancelled) return;
            const changes = await r.preparation.decrypt();
            r.preparation = null;
            if (r.cancelled) return;
            const stores = [this._storage.storeNames.groupSessionDecryptions];
            if (isTimelineOpen) {
                // read to fetch devices if timeline is open
                stores.push(this._storage.storeNames.deviceIdentities);
            }
            const writeTxn = await this._storage.readWriteTxn(stores);
            let decryption;
            try {
                decryption = await changes.write(writeTxn);
            } catch (err) {
                writeTxn.abort();
                throw err;
            }
            await writeTxn.complete();
            decryption.applyToEntries(entries);
        });
        return request;
    }

    async prepareSync(roomResponse, membership, txn) {
        const summaryChanges = this._summary.data.applySyncResponse(roomResponse, membership)
        let roomEncryption = this._roomEncryption;
        // encryption is enabled in this sync
        if (!roomEncryption && summaryChanges.encryption) {
            roomEncryption = this._createRoomEncryption(this, summaryChanges.encryption);
        }

        let decryptPreparation;
        if (roomEncryption) {
            const events = roomResponse?.timeline?.events;
            if (Array.isArray(events)) {
                const eventsToDecrypt = events.filter(event => {
                    return event?.type === EVENT_ENCRYPTED_TYPE;
                });
                decryptPreparation = await roomEncryption.prepareDecryptAll(
                    eventsToDecrypt, DecryptionSource.Sync, this._isTimelineOpen, txn);
            }
        }

        return {
            roomEncryption,
            summaryChanges,
            decryptPreparation,
            decryptChanges: null,
        };
    }

    async afterPrepareSync(preparation) {
        if (preparation.decryptPreparation) {
            preparation.decryptChanges = await preparation.decryptPreparation.decrypt();
            preparation.decryptPreparation = null;
        }
    }

    /** @package */
    async writeSync(roomResponse, isInitialSync, {summaryChanges, decryptChanges, roomEncryption}, txn) {
        const {entries, newLiveKey, memberChanges} =
            await this._syncWriter.writeSync(roomResponse, txn);
        if (decryptChanges) {
            const decryption = await decryptChanges.write(txn);
            decryption.applyToEntries(entries);
        }
        // pass member changes to device tracker
        if (roomEncryption && this.isTrackingMembers && memberChanges?.size) {
            await roomEncryption.writeMemberChanges(memberChanges, txn);
        }
        // also apply (decrypted) timeline entries to the summary changes
        summaryChanges = summaryChanges.applyTimelineEntries(
            entries, isInitialSync, !this._isTimelineOpen, this._user.id);
        // write summary changes, and unset if nothing was actually changed
        summaryChanges = this._summary.writeData(summaryChanges, txn);
        // fetch new members while we have txn open,
        // but don't make any in-memory changes yet
        let heroChanges;
        if (summaryChanges?.needsHeroes) {
            // room name disappeared, open heroes
            if (!this._heroes) {
                this._heroes = new Heroes(this._roomId);
            }
            heroChanges = await this._heroes.calculateChanges(summaryChanges.heroes, memberChanges, txn);
        }
        let removedPendingEvents;
        if (Array.isArray(roomResponse.timeline?.events)) {
            removedPendingEvents = this._sendQueue.removeRemoteEchos(roomResponse.timeline.events, txn);
        }
        return {
            summaryChanges,
            roomEncryption,
            newTimelineEntries: entries,
            newLiveKey,
            removedPendingEvents,
            memberChanges,
            heroChanges,
        };
    }

    /**
     * @package
     * Called with the changes returned from `writeSync` to apply them and emit changes.
     * No storage or network operations should be done here.
     */
    afterSync({summaryChanges, newTimelineEntries, newLiveKey, removedPendingEvents, memberChanges, heroChanges, roomEncryption}) {
        this._syncWriter.afterSync(newLiveKey);
        this._setEncryption(roomEncryption);
        if (memberChanges.size) {
            if (this._changedMembersDuringSync) {
                for (const [userId, memberChange] of memberChanges.entries()) {
                    this._changedMembersDuringSync.set(userId, memberChange.member);
                }
            }
            if (this._memberList) {
                this._memberList.afterSync(memberChanges);
            }
        }
        let emitChange = false;
        if (summaryChanges) {
            this._summary.applyChanges(summaryChanges);
            if (!this._summary.data.needsHeroes) {
                this._heroes = null;
            }
            emitChange = true;
        }
        if (this._heroes && heroChanges) {
            const oldName = this.name;
            this._heroes.applyChanges(heroChanges, this._summary.data);
            if (oldName !== this.name) {
                emitChange = true;
            }
        }
        if (emitChange) {
            this._emitUpdate();
        }
        if (this._timeline) {
            this._timeline.appendLiveEntries(newTimelineEntries);
        }
        if (removedPendingEvents) {
            this._sendQueue.emitRemovals(removedPendingEvents);
        }
    }

    needsAfterSyncCompleted({memberChanges}) {
        return this._roomEncryption?.needsToShareKeys(memberChanges);
    }

    /**
     * Only called if the result of writeSync had `needsAfterSyncCompleted` set.
     * Can be used to do longer running operations that resulted from the last sync,
     * like network operations.
     */
    async afterSyncCompleted() {
        if (this._roomEncryption) {
            await this._roomEncryption.flushPendingRoomKeyShares(this._hsApi);
        }
    }

    /** @package */
    async start(pendingOperations) {
        if (this._roomEncryption) {
            try {
                const roomKeyShares = pendingOperations?.get("share_room_key");
                if (roomKeyShares) {
                    // if we got interrupted last time sending keys to newly joined members
                    await this._roomEncryption.flushPendingRoomKeyShares(this._hsApi, roomKeyShares);
                }
            } catch (err) {
                // we should not throw here
                console.error(`could not send out (all) pending room keys for room ${this.id}`, err.stack);
            }
        }
        this._sendQueue.resumeSending();
    }

    /** @package */
    async load(summary, txn) {
        try {
            this._summary.load(summary);
            if (this._summary.data.encryption) {
                const roomEncryption = this._createRoomEncryption(this, this._summary.data.encryption);
                this._setEncryption(roomEncryption);
            }
            // need to load members for name?
            if (this._summary.data.needsHeroes) {
                this._heroes = new Heroes(this._roomId);
                const changes = await this._heroes.calculateChanges(this._summary.data.heroes, [], txn);
                this._heroes.applyChanges(changes, this._summary.data);
            }
            return this._syncWriter.load(txn);
        } catch (err) {
            throw new WrappedError(`Could not load room ${this._roomId}`, err);
        }
    }

    /** @public */
    sendEvent(eventType, content) {
        return this._sendQueue.enqueueEvent(eventType, content);
    }

    /** @public */
    async loadMemberList() {
        if (this._memberList) {
            // TODO: also await fetchOrLoadMembers promise here
            this._memberList.retain();
            return this._memberList;
        } else {
            const members = await fetchOrLoadMembers({
                summary: this._summary,
                roomId: this._roomId,
                hsApi: this._hsApi,
                storage: this._storage,
                syncToken: this._getSyncToken(),
                // to handle race between /members and /sync
                setChangedMembersMap: map => this._changedMembersDuringSync = map,
            });
            this._memberList = new MemberList({
                members,
                closeCallback: () => { this._memberList = null; }
            });
            return this._memberList;
        }
    } 

    /** @public */
    async fillGap(fragmentEntry, amount) {
        // TODO move some/all of this out of Room
        if (fragmentEntry.edgeReached) {
            return;
        }
        const response = await this._hsApi.messages(this._roomId, {
            from: fragmentEntry.token,
            dir: fragmentEntry.direction.asApiString(),
            limit: amount,
            filter: {
                lazy_load_members: true,
                include_redundant_members: true,
            }
        }).response();

        const txn = await this._storage.readWriteTxn([
            this._storage.storeNames.pendingEvents,
            this._storage.storeNames.timelineEvents,
            this._storage.storeNames.timelineFragments,
        ]);
        let removedPendingEvents;
        let gapResult;
        try {
            // detect remote echos of pending messages in the gap
            removedPendingEvents = this._sendQueue.removeRemoteEchos(response.chunk, txn);
            // write new events into gap
            const gapWriter = new GapWriter({
                roomId: this._roomId,
                storage: this._storage,
                fragmentIdComparer: this._fragmentIdComparer,
            });
            gapResult = await gapWriter.writeFragmentFill(fragmentEntry, response, txn);
        } catch (err) {
            txn.abort();
            throw err;
        }
        await txn.complete();
        if (this._roomEncryption) {
            const decryptRequest = this._decryptEntries(DecryptionSource.Timeline, gapResult.entries);
            await decryptRequest.complete();
        }
        // once txn is committed, update in-memory state & emit events
        for (const fragment of gapResult.fragments) {
            this._fragmentIdComparer.add(fragment);
        }
        if (removedPendingEvents) {
            this._sendQueue.emitRemovals(removedPendingEvents);
        }
        if (this._timeline) {
            this._timeline.addGapEntries(gapResult.entries);
        }
    }

    /** @public */
    get name() {
        if (this._heroes) {
            return this._heroes.roomName;
        }
        const summaryData = this._summary.data;
        if (summaryData.name) {
            return summaryData.name;
        }
        if (summaryData.canonicalAlias) {
            return summaryData.canonicalAlias;
        }
        return null;
    }

    /** @public */
    get id() {
        return this._roomId;
    }

    get avatarUrl() {
        if (this._summary.data.avatarUrl) {
            return this._summary.data.avatarUrl;
        } else if (this._heroes) {
            return this._heroes.roomAvatarUrl;
        }
        return null;
    }

    get lastMessageTimestamp() {
        return this._summary.data.lastMessageTimestamp;
    }

    get isUnread() {
        return this._summary.data.isUnread;
    }

    get notificationCount() {
        return this._summary.data.notificationCount;
    }
    
    get highlightCount() {
        return this._summary.data.highlightCount;
    }

    get isLowPriority() {
        const tags = this._summary.data.tags;
        return !!(tags && tags['m.lowpriority']);
    }

    get isEncrypted() {
        return !!this._summary.data.encryption;
    }

    enableSessionBackup(sessionBackup) {
        this._roomEncryption?.enableSessionBackup(sessionBackup);
    }

    get isTrackingMembers() {
        return this._summary.data.isTrackingMembers;
    }

    async _getLastEventId() {
        const lastKey = this._syncWriter.lastMessageKey;
        if (lastKey) {
            const txn = await this._storage.readTxn([
                this._storage.storeNames.timelineEvents,
            ]);
            const eventEntry = await txn.timelineEvents.get(this._roomId, lastKey);
            return eventEntry?.event?.event_id;
        }
    }

    get _isTimelineOpen() {
        return !!this._timeline;
    }

    _emitUpdate() {
        // once for event emitter listeners
        this.emit("change");
        // and once for collection listeners
        this._emitCollectionChange(this);
    }

    async clearUnread() {
        if (this.isUnread || this.notificationCount) {
            const txn = await this._storage.readWriteTxn([
                this._storage.storeNames.roomSummary,
            ]);
            let data;
            try {
                data = this._summary.writeClearUnread(txn);
            } catch (err) {
                txn.abort();
                throw err;
            }
            await txn.complete();
            this._summary.applyChanges(data);
            this._emitUpdate();
            
            try {
                const lastEventId = await this._getLastEventId();
                if (lastEventId) {
                    await this._hsApi.receipt(this._roomId, "m.read", lastEventId);
                }
            } catch (err) {
                // ignore ConnectionError
                if (err.name !== "ConnectionError") {
                    throw err;
                }
            }
        }
    }

    /** @public */
    openTimeline() {
        if (this._timeline) {
            throw new Error("not dealing with load race here for now");
        }
        console.log(`opening the timeline for ${this._roomId}`);
        this._timeline = new Timeline({
            roomId: this.id,
            storage: this._storage,
            fragmentIdComparer: this._fragmentIdComparer,
            pendingEvents: this._sendQueue.pendingEvents,
            closeCallback: () => {
                console.log(`closing the timeline for ${this._roomId}`);
                this._timeline = null;
                if (this._roomEncryption) {
                    this._roomEncryption.notifyTimelineClosed();
                }
            },
            user: this._user,
            clock: this._clock
        });
        if (this._roomEncryption) {
            this._timeline.enableEncryption(this._decryptEntries.bind(this, DecryptionSource.Timeline));
        }
        return this._timeline;
    }

    get mediaRepository() {
        return this._mediaRepository;
    }

    /** @package */
    writeIsTrackingMembers(value, txn) {
        return this._summary.writeIsTrackingMembers(value, txn);
    }

    /** @package */
    applyIsTrackingMembersChanges(changes) {
        this._summary.applyChanges(changes);
    }

    dispose() {
        this._roomEncryption?.dispose();
        this._timeline?.dispose();
    }
}

class DecryptionRequest {
    constructor(decryptFn) {
        this._cancelled = false;
        this.preparation = null;
        this._promise = decryptFn(this);
    }

    complete() {
        return this._promise;
    }

    get cancelled() {
        return this._cancelled;
    }

    dispose() {
        this._cancelled = true;
        if (this.preparation) {
            this.preparation.dispose();
        }
    }
}