/*
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 {Timeline} from "./timeline/Timeline.js";
import {FragmentIdComparer} from "./timeline/FragmentIdComparer.js";
import {SendQueue} from "./sending/SendQueue.js";
import {WrappedError} from "../error.js"
import {RoomMember} from "./members/RoomMember.js";
import {MemberList} from "./members/MemberList.js";

export class Room extends EventEmitter {
	constructor({roomId, storage, hsApi, emitCollectionChange, sendScheduler, pendingEvents, user}) {
        super();
        this._roomId = roomId;
        this._storage = storage;
        this._hsApi = hsApi;
		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, sendScheduler, pendingEvents});
        this._timeline = null;
        this._user = user;
        this._changedMembersDuringSync = null;
	}

    async writeSync(roomResponse, membership, txn) {
		const summaryChanges = this._summary.writeSync(roomResponse, membership, txn);
		const {entries, newLiveKey, changedMembers} = await this._syncWriter.writeSync(roomResponse, txn);
        let removedPendingEvents;
        if (roomResponse.timeline && roomResponse.timeline.events) {
            removedPendingEvents = this._sendQueue.removeRemoteEchos(roomResponse.timeline.events, txn);
        }
        return {summaryChanges, newTimelineEntries: entries, newLiveKey, removedPendingEvents, changedMembers};
    }

    afterSync({summaryChanges, newTimelineEntries, newLiveKey, removedPendingEvents, changedMembers}) {
        this._syncWriter.afterSync(newLiveKey);
        if (changedMembers.length) {
            if (this._changedMembersDuringSync) {
                for (const member of changedMembers) {
                    this._changedMembersDuringSync.set(member.userId, member);
                }
            }
            if (this._memberList) {
                this._memberList.afterSync(changedMembers);
            }
        }
        if (summaryChanges) {
            this._summary.applyChanges(summaryChanges);
            this.emit("change");
            this._emitCollectionChange(this);
        }
        if (this._timeline) {
            this._timeline.appendLiveEntries(newTimelineEntries);
        }
        if (removedPendingEvents) {
            this._sendQueue.emitRemovals(removedPendingEvents);
        }
	}

    resumeSending() {
        this._sendQueue.resumeSending();
    }

	load(summary, txn) {
        try {
            this._summary.load(summary);
            return this._syncWriter.load(txn);
        } catch (err) {
            throw new WrappedError(`Could not load room ${this._roomId}`, err);
        }
	}

    sendEvent(eventType, content) {
        return this._sendQueue.enqueueEvent(eventType, content);
    }

    async loadMemberList() {
        if (this._memberList) {
            this._memberList.retain();
            return this._memberList;
        } else {
            let members;
            if (!this._summary.hasFetchedMembers) {
                const paginationToken = this._summary.lastPaginationToken;
                // TODO: move all of this out of Room
                
                // if any members are changed by sync while we're fetching members,
                // they will end up here, so we check not to override them
                this._changedMembersDuringSync = new Map();
                
                const memberResponse = await this._hsApi.members(this._roomId, {at: paginationToken}).response;

                const txn = await this._storage.readWriteTxn([
                    this._storage.storeNames.roomSummary,
                    this._storage.storeNames.roomMembers,
                ]);
                const summaryChanges = this._summary.writeHasFetchedMembers(true, txn);
                const {roomMembers} = txn;
                const memberEvents = memberResponse.chunk;
                if (!Array.isArray(memberEvents)) {
                    throw new Error("malformed");
                }
                members = await Promise.all(memberEvents.map(async memberEvent => {
                    const userId = memberEvent?.state_key;
                    if (!userId) {
                        throw new Error("malformed");
                    }
                    // this member was changed during a sync that happened while calling /members
                    // and thus is more recent. Fetch it instead of overwriting.
                    if (this._changedMembersDuringSync.has(userId)) {
                        const memberData = await roomMembers.get(this._roomId, userId);
                        if (memberData) {
                            return new RoomMember(memberData);
                        }
                    } else {
                        const member = RoomMember.fromMemberEvent(this._roomId, memberEvent);
                        if (member) {
                            roomMembers.set(member.serialize());
                        }
                        return member;
                    }
                }));
                this._changedMembersDuringSync = null;
                await txn.complete();
                this._summary.applyChanges(summaryChanges);
            } else {
                const txn = await this._storage.readTxn([
                    this._storage.storeNames.roomMembers,
                ]);
                const memberDatas = await txn.roomMembers.getAll(this._roomId);
                members = memberDatas.map(d => new RoomMember(d));
            }
            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}
        }).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);
        }
    }

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

    get id() {
        return this._roomId;
    }

    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;
            },
            user: this._user,
        });
        await this._timeline.load();
        return this._timeline;
    }

    mxcUrlThumbnail(url, width, height, method) {
        return this._hsApi.mxcUrlThumbnail(url, width, height, method);
    }

    mxcUrl(url) {
        return this._hsApi.mxcUrl(url);
    }
}