/*
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.
*/

function applySyncResponse(data, roomResponse, membership, isInitialSync, isTimelineOpen, ownUserId) {
    if (roomResponse.summary) {
        data = updateSummary(data, roomResponse.summary);
    }
    if (membership !== data.membership) {
        data = data.cloneIfNeeded();
        data.membership = membership;
    }
    // state comes before timeline
    if (roomResponse.state) {
        data = roomResponse.state.events.reduce((data, event) => {
            return processEvent(data, event, isInitialSync, isTimelineOpen, ownUserId);
        }, data);
    }
    if (roomResponse.timeline) {
        const {timeline} = roomResponse;
        if (timeline.prev_batch) {
            data = data.cloneIfNeeded();
            data.lastPaginationToken = timeline.prev_batch;
        }
        data = timeline.events.reduce((data, event) => {
            return processEvent(data, event, isInitialSync, isTimelineOpen, ownUserId);
        }, data);
    }
    const unreadNotifications = roomResponse.unread_notifications;
    if (unreadNotifications) {
        data = data.cloneIfNeeded();
        data.highlightCount = unreadNotifications.highlight_count;
        data.notificationCount = unreadNotifications.notification_count;
    }

    return data;
}

function processEvent(data, event, isInitialSync, isTimelineOpen, ownUserId) {
    if (event.type === "m.room.encryption") {
        if (!data.isEncrypted) {
            data = data.cloneIfNeeded();
            data.isEncrypted = true;
        }
    } else if (event.type === "m.room.name") {
        const newName = event.content?.name;
        if (newName !== data.name) {
            data = data.cloneIfNeeded();
            data.name = newName;
        }
    } else if (event.type === "m.room.avatar") {
        const newUrl = event.content?.url;
        if (newUrl !== data.avatarUrl) {
            data = data.cloneIfNeeded();
            data.avatarUrl = newUrl;
        }
    } else if (event.type === "m.room.message") {
        data = data.cloneIfNeeded();
        data.lastMessageTimestamp = event.origin_server_ts;
        if (!isInitialSync && event.sender !== ownUserId && !isTimelineOpen) {
            data.isUnread = true;
        }
        const {content} = event;
        const body = content?.body;
        const msgtype = content?.msgtype;
        if (msgtype === "m.text") {
            data.lastMessageBody = body;
        }
    } else if (event.type === "m.room.canonical_alias") {
        const content = event.content;
        data = data.cloneIfNeeded();
        data.canonicalAlias = content.alias;
        data.altAliases = content.alt_aliases;
    }
    return data;
}

function updateSummary(data, summary) {
    const heroes = summary["m.heroes"];
    const inviteCount = summary["m.joined_member_count"];
    const joinCount = summary["m.invited_member_count"];

    if (heroes) {
        data = data.cloneIfNeeded();
        data.heroes = heroes;
    }
    if (Number.isInteger(inviteCount)) {
        data = data.cloneIfNeeded();
        data.inviteCount = inviteCount;
    }
    if (Number.isInteger(joinCount)) {
        data = data.cloneIfNeeded();
        data.joinCount = joinCount;
    }
    return data;
}

class SummaryData {
    constructor(copy, roomId) {
        this.roomId = copy ? copy.roomId : roomId;
        this.name = copy ? copy.name : null;
        this.lastMessageBody = copy ? copy.lastMessageBody : null;
        this.lastMessageTimestamp = copy ? copy.lastMessageTimestamp : null;
        this.isUnread = copy ? copy.isUnread : false;
        this.isEncrypted = copy ? copy.isEncrypted : false;
        this.isDirectMessage = copy ? copy.isDirectMessage : false;
        this.membership = copy ? copy.membership : null;
        this.inviteCount = copy ? copy.inviteCount : 0;
        this.joinCount = copy ? copy.joinCount : 0;
        this.heroes = copy ? copy.heroes : null;
        this.canonicalAlias = copy ? copy.canonicalAlias : null;
        this.altAliases = copy ? copy.altAliases : null;
        this.hasFetchedMembers = copy ? copy.hasFetchedMembers : false;
        this.lastPaginationToken = copy ? copy.lastPaginationToken : null;
        this.avatarUrl = copy ? copy.avatarUrl : null;
        this.notificationCount = copy ? copy.notificationCount : 0;
        this.highlightCount = copy ? copy.highlightCount : 0;
        this.cloned = copy ? true : false;
    }

    cloneIfNeeded() {
        if (this.cloned) {
            return this;
        } else {
            return new SummaryData(this);
        }
    }

    serialize() {
        const {cloned, ...serializedProps} = this;
        return serializedProps;
    }
}

export class RoomSummary {
	constructor(roomId, ownUserId) {
        this._ownUserId = ownUserId;
        this._data = new SummaryData(null, roomId);
	}

	get name() {
		if (this._data.name) {
            return this._data.name;
        }
        if (this._data.canonicalAlias) {
            return this._data.canonicalAlias;
        }
        if (Array.isArray(this._data.altAliases) && this._data.altAliases.length !== 0) {
            return this._data.altAliases[0];
        }
        if (Array.isArray(this._data.heroes) && this._data.heroes.length !== 0) {
            return this._data.heroes.join(", ");
        }
        return this._data.roomId;
	}

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

    get notificationCount() {
        return this._data.notificationCount;
    }

	get lastMessage() {
		return this._data.lastMessageBody;
	}

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

	get inviteCount() {
		return this._data.inviteCount;
	}

	get joinCount() {
		return this._data.joinCount;
	}

    get avatarUrl() {
        return this._data.avatarUrl;
    }

    get hasFetchedMembers() {
        return this._data.hasFetchedMembers;
    }

    get lastPaginationToken() {
        return this._data.lastPaginationToken;
    }

    writeClearUnread(txn) {
        const data = new SummaryData(this._data);
        data.isUnread = false;
        data.notificationCount = 0;
        data.highlightCount = 0;
        txn.roomSummary.set(data.serialize());
        return data;
    }

    writeHasFetchedMembers(value, txn) {
        const data = new SummaryData(this._data);
        data.hasFetchedMembers = value;
        txn.roomSummary.set(data.serialize());
        return data;
    }

	writeSync(roomResponse, membership, isInitialSync, isTimelineOpen, txn) {
        // clear cloned flag, so cloneIfNeeded makes a copy and
        // this._data is not modified if any field is changed.
        this._data.cloned = false;
		const data = applySyncResponse(
            this._data, roomResponse,
            membership,
            isInitialSync, isTimelineOpen,
            this._ownUserId);
		if (data !== this._data) {
            // need to think here how we want to persist
            // things like unread status (as read marker, or unread count)?
            // we could very well load additional things in the load method
            // ... the trade-off is between constantly writing the summary
            // on every sync, or doing a bit of extra reading on load
            // and have in-memory only variables for visualization
            txn.roomSummary.set(data.serialize());
            return data;
		}
	}

    applyChanges(data) {
        this._data = data;
    }

	async load(summary) {
        this._data = new SummaryData(summary);
	}
}

export function tests() {
    return {
        "membership trigger change": function(assert) {
            const summary = new RoomSummary("id");
            let written = false;
            const changes = summary.writeSync({}, "join", {roomSummary: {set: () => { written = true; }}});
            assert(changes);
            assert(written);
            assert.equal(changes.membership, "join");
        }
    }
}