/*
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, needsHeroes} from "./RoomSummary.js";
import {SyncWriter} from "./timeline/persistence/SyncWriter.js";
import {GapWriter} from "./timeline/persistence/GapWriter.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";

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

    async _decryptSyncEntries(entries, txn) {
        await Promise.all(entries.map(async e => {
            if (e.eventType === "m.room.encrypted") {
                try {
                    const decryptedEvent = await this._roomEncryption.decryptNewSyncEvent(e.internalId, e.event, txn);
                    if (decryptedEvent) {
                        e.replaceWithDecrypted(decryptedEvent);
                    }
                } catch (err) {
                    e.setDecryptionError(err);
                }
            }
        }));
        return entries;
    }

    /** @package */
    async writeSync(roomResponse, membership, isInitialSync, txn) {
        const isTimelineOpen = !!this._timeline;
		const summaryChanges = this._summary.writeSync(
            roomResponse,
            membership,
            isInitialSync, isTimelineOpen,
            txn);
		const {entries: encryptedEntries, newLiveKey, memberChanges} =
            await this._syncWriter.writeSync(roomResponse, txn);
        // decrypt if applicable
        let entries = encryptedEntries;
        if (this._roomEncryption) {
            entries = await this._decryptSyncEntries(encryptedEntries, txn);
        }
        // fetch new members while we have txn open,
        // but don't make any in-memory changes yet
        let heroChanges;
        if (needsHeroes(summaryChanges)) {
            // room name disappeared, open heroes
            if (!this._heroes) {
                this._heroes = new Heroes(this._roomId);
            }
            heroChanges = await this._heroes.calculateChanges(summaryChanges.heroes, memberChanges, txn);
        }
        // pass member changes to device tracker
        if (this._roomEncryption && this.isTrackingMembers && memberChanges?.size) {
            await this._roomEncryption.writeMemberChanges(memberChanges, txn);
        }
        let removedPendingEvents;
        if (roomResponse.timeline && roomResponse.timeline.events) {
            removedPendingEvents = this._sendQueue.removeRemoteEchos(roomResponse.timeline.events, txn);
        }
        return {
            summaryChanges,
            newTimelineEntries: entries,
            newLiveKey,
            removedPendingEvents,
            memberChanges,
            heroChanges
        };
    }

    /** @package */
    afterSync({summaryChanges, newTimelineEntries, newLiveKey, removedPendingEvents, memberChanges, heroChanges}) {
        this._syncWriter.afterSync(newLiveKey);
        // encryption got enabled
        if (!this._summary.encryption && summaryChanges.encryption && !this._roomEncryption) {
            this._roomEncryption = this._createRoomEncryption(this, summaryChanges.encryption);
            if (this._roomEncryption) {
                this._sendQueue.enableEncryption(this._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.needsHeroes) {
                this._heroes = null;
            }
            emitChange = true;
        }
        if (this._heroes && heroChanges) {
            const oldName = this.name;
            this._heroes.applyChanges(heroChanges, this._summary);
            if (oldName !== this.name) {
                emitChange = true;
            }
        }
        if (emitChange) {
            this.emit("change");
            this._emitCollectionChange(this);
        }
        if (this._timeline) {
            this._timeline.appendLiveEntries(newTimelineEntries);
        }
        if (removedPendingEvents) {
            this._sendQueue.emitRemovals(removedPendingEvents);
        }
	}

    /** @package */
    resumeSending() {
        this._sendQueue.resumeSending();
    }

    /** @package */
	async load(summary, txn) {
        try {
            this._summary.load(summary);
            if (this._summary.encryption) {
                this._roomEncryption = this._createRoomEncryption(this, this._summary.encryption);
                if (this._roomEncryption) {
                    this._sendQueue.enableEncryption(this._roomEncryption);
                }
            }
            // need to load members for name?
            if (this._summary.needsHeroes) {
                this._heroes = new Heroes(this._roomId);
                const changes = await this._heroes.calculateChanges(this._summary.heroes, [], txn);
                this._heroes.applyChanges(changes, this._summary);
            }
            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,
                // 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();
        // 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;
        }
        return this._summary.name;
    }

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

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

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

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

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

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

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

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

    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.emit("change");
            this._emitCollectionChange(this);
            
            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 */
    async 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,
        });
        await this._timeline.load();
        return this._timeline;
    }

    get mediaRepository() {
        return this._hsApi.mediaRepository;
    }

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

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