/*
Copyright 2016 OpenMarket Ltd

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.
*/

var React = require('react');
var ReactDOM = require("react-dom");
var q = require("q");

var Matrix = require("matrix-js-sdk");

var sdk = require('../../index');
var MatrixClientPeg = require("../../MatrixClientPeg");
var dis = require("../../dispatcher");
var ObjectUtils = require('../../ObjectUtils');
var Modal = require("../../Modal");
var UserActivity = require("../../UserActivity");
var KeyCode = require('../../KeyCode');

var PAGINATE_SIZE = 20;
var INITIAL_SIZE = 20;
var TIMELINE_CAP = 250; // the most events to show in a timeline

var DEBUG = false;

if (DEBUG) {
    // using bind means that we get to keep useful line numbers in the console
    var debuglog = console.log.bind(console);
} else {
    var debuglog = function () {};
}

/*
 * Component which shows the notification timeline, based on TimelinePanel
 */
var NotificationPanel = React.createClass({
    displayName: 'NotificationPanel',

    propTypes: {
        // where to position the event given by eventId, in pixels from the
        // bottom of the viewport. If not given, will try to put the event
        // half way down the viewport.
        eventPixelOffset: React.PropTypes.number,

        // callback which is called when the panel is scrolled.
        onScroll: React.PropTypes.func,

        // opacity for dynamic UI fading effects
        opacity: React.PropTypes.number,
    },

    getInitialState: function() {
        return {
            events: [],
            notificationsLoading: true, // track whether our room timeline is loading

            // canBackPaginate == false may mean:
            //
            // * we haven't (successfully) loaded the notifications yet, or:
            //
            // * the server indicated that there were no more visible events
            //  (normally implying we got to the start of time), or:
            //
            // * we gave up asking the server for more events
            canBackPaginate: false,

            // canForwardPaginate == false may mean:
            //
            // * we haven't (successfully) loaded the notifications yet
            //
            // * we have got to the end of time and are now tracking live
            //   notifications
            //
            // * we are looking at some historical point, but gave up asking
            //   the server for more events
            canForwardPaginate: false,

            backPaginating: false,
            forwardPaginating: false,
        };
    },

    componentWillMount: function() {
        debuglog("NotificationPanel: mounting");

        MatrixClientPeg.get().on("Notification.timeline", this.onNotificationTimeline);

        this._initNotification(this.props);
    },

    shouldComponentUpdate: function(nextProps, nextState) {
        if (!ObjectUtils.shallowEqual(this.props, nextProps)) {
            if (DEBUG) {
                console.group("NotificationPanel.shouldComponentUpdate: props change");
                console.log("props before:", this.props);
                console.log("props after:", nextProps);
                console.groupEnd();
            }
            return true;
        }

        if (!ObjectUtils.shallowEqual(this.state, nextState)) {
            if (DEBUG) {
                console.group("NotificationPanel.shouldComponentUpdate: state change");
                console.log("state before:", this.state);
                console.log("state after:", nextState);
                console.groupEnd();
            }
            return true;
        }

        return false;
    },

    componentWillUnmount: function() {
        // set a boolean to say we've been unmounted, which any pending
        // promises can use to throw away their results.
        //
        // (We could use isMounted, but facebook have deprecated that.)
        this.unmounted = true;

        var client = MatrixClientPeg.get();
        if (client) {
            client.removeListener("Notification.timeline", this.onNotificationTimeline);
        }
    },

    // set off a pagination request.
    onMessageListFillRequest: function(backwards) {
        var dir = backwards ? EventTimeline.BACKWARDS : EventTimeline.FORWARDS;
        var canPaginateKey = backwards ? 'canBackPaginate' : 'canForwardPaginate';
        var paginatingKey = backwards ? 'backPaginating' : 'forwardPaginating';

        if (!this.state[canPaginateKey]) {
            debuglog("NotificationPanel: have given up", dir, "paginating notifications");
            return q(false);
        }

        if(!this._timelineWindow.canPaginate(dir)) {
            debuglog("TimelinePanel: can't", dir, "paginate any further");
            this.setState({[canPaginateKey]: false});
            return q(false);
        }

        debuglog("TimelinePanel: Initiating paginate; backwards:"+backwards);
        this.setState({[paginatingKey]: true});

        return this._timelineWindow.paginate(dir, PAGINATE_SIZE).then((r) => {
            if (this.unmounted) { return; }

            debuglog("TimelinePanel: paginate complete backwards:"+backwards+"; success:"+r);

            var newState = {
                [paginatingKey]: false,
                [canPaginateKey]: r,
                events: this._getEvents(),
            };

            // moving the window in this direction may mean that we can now
            // paginate in the other where we previously could not.
            var otherDirection = backwards ? EventTimeline.FORWARDS : EventTimeline.BACKWARDS;
            var canPaginateOtherWayKey = backwards ? 'canForwardPaginate' : 'canBackPaginate';
            if (!this.state[canPaginateOtherWayKey] &&
                    this._timelineWindow.canPaginate(otherDirection)) {
                debuglog('TimelinePanel: can now', otherDirection, 'paginate again');
                newState[canPaginateOtherWayKey] = true;
            }

            this.setState(newState);

            return r;
        });
    },

    onMessageListScroll: function () {
        if (this.props.onScroll) {
            this.props.onScroll();
        }

        // we hide the read marker when it first comes onto the screen, but if
        // it goes back off the top of the screen (presumably because the user
        // clicks on the 'jump to bottom' button), we need to re-enable it.
        if (this.getReadMarkerPosition() < 0) {
            this.setState({readMarkerVisible: true});
        }
    },

    onRoomTimeline: function(ev, room, toStartOfTimeline, removed, data) {
        // ignore events for other rooms
        if (room !== this.props.room) return;

        // ignore anything but real-time updates at the end of the room:
        // updates from pagination will happen when the paginate completes.
        if (toStartOfTimeline || !data || !data.liveEvent) return;

        if (!this.refs.messagePanel) return;

        if (!this.refs.messagePanel.getScrollState().stuckAtBottom) {
            // we won't load this event now, because we don't want to push any
            // events off the other end of the timeline. But we need to note
            // that we can now paginate.
            this.setState({canForwardPaginate: true});
            return;
        }

        // tell the timeline window to try to advance itself, but not to make
        // an http request to do so.
        //
        // we deliberately avoid going via the ScrollPanel for this call - the
        // ScrollPanel might already have an active pagination promise, which
        // will fail, but would stop us passing the pagination request to the
        // timeline window.
        //
        // see https://github.com/vector-im/vector-web/issues/1035
        this._timelineWindow.paginate(EventTimeline.FORWARDS, 1, false).done(() => {
            if (this.unmounted) { return; }

            var events = this._timelineWindow.getEvents();
            var lastEv = events[events.length-1];

            // if we're at the end of the live timeline, append the pending events
            if (!this._timelineWindow.canPaginate(EventTimeline.FORWARDS)) {
                events.push(... this.props.room.getPendingEvents());
            }

            var updatedState = {events: events};

            // when a new event arrives when the user is not watching the
            // window, but the window is in its auto-scroll mode, make sure the
            // read marker is visible.
            //
            // We ignore events we have sent ourselves; we don't want to see the
            // read-marker when a remote echo of an event we have just sent takes
            // more than the timeout on userCurrentlyActive.
            //
            var myUserId = MatrixClientPeg.get().credentials.userId;
            var sender = ev.sender ? ev.sender.userId : null;
            var callback = null;
            if (sender != myUserId && !UserActivity.userCurrentlyActive()) {
                updatedState.readMarkerVisible = true;
            } else if(lastEv && this.getReadMarkerPosition() === 0) {
                // we know we're stuckAtBottom, so we can advance the RM
                // immediately, to save a later render cycle
                this._setReadMarker(lastEv.getId(), lastEv.getTs(), true);
                updatedState.readMarkerVisible = false;
                updatedState.readMarkerEventId = lastEv.getId();
                callback = this.props.onReadMarkerUpdated;
            }

            this.setState(updatedState, callback);
        });
    },

    onRoomTimelineReset: function(room) {
        if (room !== this.props.room) return;

        if (this.refs.messagePanel && this.refs.messagePanel.isAtBottom()) {
            this._loadTimeline();
        }
    },

    onRoomRedaction: function(ev, room) {
        if (this.unmounted) return;

        // ignore events for other rooms
        if (room !== this.props.room) return;

        // we could skip an update if the event isn't in our timeline,
        // but that's probably an early optimisation.
        this.forceUpdate();
    },

    onRoomReceipt: function(ev, room) {
        if (this.unmounted) return;

        // ignore events for other rooms
        if (room !== this.props.room) return;

        this.forceUpdate();
    },

    onLocalEchoUpdated: function(ev, room, oldEventId) {
        if (this.unmounted) return;

        // ignore events for other rooms
        if (room !== this.props.room) return;

        this._reloadEvents();
    },

    /* jump down to the bottom of this room, where new events are arriving
     */
    jumpToLiveTimeline: function() {
        // if we can't forward-paginate the existing timeline, then there
        // is no point reloading it - just jump straight to the bottom.
        //
        // Otherwise, reload the timeline rather than trying to paginate
        // through all of space-time.
        if (this._timelineWindow.canPaginate(EventTimeline.FORWARDS)) {
            this._loadTimeline();
        } else {
            if (this.refs.messagePanel) {
                this.refs.messagePanel.scrollToBottom();
            }
        }
    },

    /* scroll to show the read-up-to marker. We put it 1/3 of the way down
     * the container.
     */
    jumpToReadMarker: function() {
        if (!this.refs.messagePanel)
            return;

        if (!this.state.readMarkerEventId)
            return;

        // we may not have loaded the event corresponding to the read-marker
        // into the _timelineWindow. In that case, attempts to scroll to it
        // will fail.
        //
        // a quick way to figure out if we've loaded the relevant event is
        // simply to check if the messagepanel knows where the read-marker is.
        var ret = this.refs.messagePanel.getReadMarkerPosition();
        if (ret !== null) {
            // The messagepanel knows where the RM is, so we must have loaded
            // the relevant event.
            this.refs.messagePanel.scrollToEvent(this.state.readMarkerEventId,
                                                 0, 1/3);
            return;
        }

        // Looks like we haven't loaded the event corresponding to the read-marker.
        // As with jumpToLiveTimeline, we want to reload the timeline around the
        // read-marker.
        this._loadTimeline(this.state.readMarkerEventId, 0, 1/3);
    },


    /* update the read-up-to marker to match the read receipt
     */
    forgetReadMarker: function() {
        var rmId = this._getCurrentReadReceipt();

        // see if we know the timestamp for the rr event
        var tl = this.props.room.getTimelineForEvent(rmId);
        var rmTs;
        if (tl) {
            var event = tl.getEvents().find((e) => { return e.getId() == rmId });
            if (event) {
                rmTs = event.getTs();
            }
        }

        this._setReadMarker(rmId, rmTs);
    },

    /* return true if the content is fully scrolled down and we are
     * at the end of the live timeline.
     */
    isAtEndOfLiveTimeline: function() {
        return this.refs.messagePanel
            && this.refs.messagePanel.isAtBottom()
            && this._timelineWindow
            && !this._timelineWindow.canPaginate(EventTimeline.FORWARDS);
    },


    /* get the current scroll state. See ScrollPanel.getScrollState for
     * details.
     *
     * returns null if we are not mounted.
     */
    getScrollState: function() {
        if (!this.refs.messagePanel) { return null; }
        return this.refs.messagePanel.getScrollState();
    },

    // returns one of:
    //
    //  null: there is no read marker
    //  -1: read marker is above the window
    //   0: read marker is visible
    //  +1: read marker is below the window
    getReadMarkerPosition: function() {
        if (!this.refs.messagePanel) { return null; }
        var ret = this.refs.messagePanel.getReadMarkerPosition();
        if (ret !== null) {
            return ret;
        }

        // the messagePanel doesn't know where the read marker is.
        // if we know the timestamp of the read marker, make a guess based on that.
        var rmTs = TimelinePanel.roomReadMarkerTsMap[this.props.room.roomId];
        if (rmTs && this.state.events.length > 0) {
            if (rmTs < this.state.events[0].getTs()) {
                return -1;
            } else {
                return 1;
            }
        }

        return null;
    },

    /**
     * called by the parent component when PageUp/Down/etc is pressed.
     *
     * We pass it down to the scroll panel.
     */
    handleScrollKey: function(ev) {
        if (!this.refs.messagePanel) { return; }

        // jump to the live timeline on ctrl-end, rather than the end of the
        // timeline window.
        if (ev.ctrlKey && ev.keyCode == KeyCode.END) {
            this.jumpToLiveTimeline();
        } else {
            this.refs.messagePanel.handleScrollKey(ev);
        }
    },

    _initTimeline: function(props) {
        var initialEvent = props.eventId;
        var pixelOffset = props.eventPixelOffset;

        // if a pixelOffset is given, it is relative to the bottom of the
        // container. If not, put the event in the middle of the container.
        var offsetBase = 1;
        if (pixelOffset == null) {
            offsetBase = 0.5;
        }

        return this._loadTimeline(initialEvent, pixelOffset, offsetBase);
    },

    /**
     * (re)-load the event timeline, and initialise the scroll state, centered
     * around the given event.
     *
     * @param {string?}  eventId the event to focus on. If undefined, will
     *    scroll to the bottom of the room.
     *
     * @param {number?} pixelOffset   offset to position the given event at
     *    (pixels from the offsetBase). If omitted, defaults to 0.
     *
     * @param {number?} offsetBase the reference point for the pixelOffset. 0
     *     means the top of the container, 1 means the bottom, and fractional
     *     values mean somewhere in the middle. If omitted, it defaults to 0.
     *
     * returns a promise which will resolve when the load completes.
     */
    _loadTimeline: function(eventId, pixelOffset, offsetBase) {
        this._timelineWindow = new Matrix.TimelineWindow(
            MatrixClientPeg.get(), this.props.room,
            {windowLimit: TIMELINE_CAP});

        var onLoaded = () => {
            this._reloadEvents();

            // If we switched away from the room while there were pending
            // outgoing events, the read-marker will be before those events.
            // We need to skip over any which have subsequently been sent.
            this._advanceReadMarkerPastMyEvents();

            this.setState({
                canBackPaginate: this._timelineWindow.canPaginate(EventTimeline.BACKWARDS),
                canForwardPaginate: this._timelineWindow.canPaginate(EventTimeline.FORWARDS),
                timelineLoading: false,
            }, () => {
                // initialise the scroll state of the message panel
                if (!this.refs.messagePanel) {
                    // this shouldn't happen - we know we're mounted because
                    // we're in a setState callback, and we know
                    // timelineLoading is now false, so render() should have
                    // mounted the message panel.
                    console.log("can't initialise scroll state because " +
                                "messagePanel didn't load");
                    return;
                }
                if (eventId) {
                    this.refs.messagePanel.scrollToEvent(eventId, pixelOffset,
                                                         offsetBase);
                } else {
                    this.refs.messagePanel.scrollToBottom();
                }

                this.sendReadReceipt();
                this.updateReadMarker();
            });
        };

        var onError = (error) => {
            this.setState({timelineLoading: false});
            var msg = error.message ? error.message : JSON.stringify(error);
            var ErrorDialog = sdk.getComponent("dialogs.ErrorDialog");

            var onFinished;

            // if we were given an event ID, then when the user closes the
            // dialog, let's jump to the end of the timeline. If we weren't,
            // something has gone badly wrong and rather than causing a loop of
            // undismissable dialogs, let's just give up.
            if (eventId) {
                onFinished = () => {
                    // go via the dispatcher so that the URL is updated
                    dis.dispatch({
                        action: 'view_room',
                        room_id: this.props.room.roomId,
                    });
                };
            }
            var message = "Vector was trying to load a specific point in this room's timeline but ";
            if (error.errcode == 'M_FORBIDDEN') {
                message += "you do not have permission to view the message in question.";
            } else {
                message += "was unable to find it.";
            }
            Modal.createDialog(ErrorDialog, {
                title: "Failed to load timeline position",
                description: message,
                onFinished: onFinished,
            });
        }

        var prom = this._timelineWindow.load(eventId, INITIAL_SIZE);

        // if we already have the event in question, TimelineWindow.load
        // returns a resolved promise.
        //
        // In this situation, we don't really want to defer the update of the
        // state to the next event loop, because it makes room-switching feel
        // quite slow. So we detect that situation and shortcut straight to
        // calling _reloadEvents and updating the state.

        if (prom.isFulfilled()) {
            onLoaded();
        } else {
            this.setState({
                events: [],
                canBackPaginate: false,
                canForwardPaginate: false,
                timelineLoading: true,
            });

            prom = prom.then(onLoaded, onError)
        }

        prom.done();
    },

    // handle the completion of a timeline load or localEchoUpdate, by
    // reloading the events from the timelinewindow and pending event list into
    // the state.
    _reloadEvents: function() {
        // we might have switched rooms since the load started - just bin
        // the results if so.
        if (this.unmounted) return;

        this.setState({
            events: this._getEvents(),
        });
    },

    // get the list of events from the timeline window and the pending event list
    _getEvents: function() {
        var events = this._timelineWindow.getEvents();

        // if we're at the end of the live timeline, append the pending events
        if (!this._timelineWindow.canPaginate(EventTimeline.FORWARDS)) {
            events.push(... this.props.room.getPendingEvents());
        }

        return events;
    },

    _indexForEventId: function(evId) {
        for (var i = 0; i < this.state.events.length; ++i) {
            if (evId == this.state.events[i].getId()) {
                return i;
            }
        }
        return null;
    },

    _getLastDisplayedEventIndex: function(opts) {
        opts = opts || {};
        var ignoreOwn = opts.ignoreOwn || false;
        var ignoreEchoes = opts.ignoreEchoes || false;
        var allowPartial = opts.allowPartial || false;

        var messagePanel = this.refs.messagePanel;
        if (messagePanel === undefined) return null;

        var wrapperRect = ReactDOM.findDOMNode(messagePanel).getBoundingClientRect();
        var myUserId = MatrixClientPeg.get().credentials.userId;

        for (var i = this.state.events.length-1; i >= 0; --i) {
            var ev = this.state.events[i];

            if (ignoreOwn && ev.sender && ev.sender.userId == myUserId) {
                continue;
            }

            // local echoes have a fake event ID
            if (ignoreEchoes && ev.status) {
                continue;
            }

            var node = messagePanel.getNodeForEventId(ev.getId());
            if (!node) continue;

            var boundingRect = node.getBoundingClientRect();
            if ((allowPartial && boundingRect.top < wrapperRect.bottom) ||
                (!allowPartial && boundingRect.bottom < wrapperRect.bottom)) {
                return i;
            }
        }
        return null;
    },

    /**
     * get the id of the event corresponding to our user's latest read-receipt.
     *
     * @param {Boolean} ignoreSynthesized If true, return only receipts that
     *                                    have been sent by the server, not
     *                                    implicit ones generated by the JS
     *                                    SDK.
     */
    _getCurrentReadReceipt: function(ignoreSynthesized) {
        var client = MatrixClientPeg.get();
        // the client can be null on logout
        if (client == null)
            return null;

        var myUserId = client.credentials.userId;
        return this.props.room.getEventReadUpTo(myUserId, ignoreSynthesized);
    },

    _setReadMarker: function(eventId, eventTs, inhibitSetState) {
        if (TimelinePanel.roomReadMarkerMap[this.props.room.roomId] == eventId) {
            // don't update the state (and cause a re-render) if there is
            // no change to the RM.
            return;
        }

        // ideally we'd sync these via the server, but for now just stash them
        // in a map.
        TimelinePanel.roomReadMarkerMap[this.props.room.roomId] = eventId;

        // in order to later figure out if the read marker is
        // above or below the visible timeline, we stash the timestamp.
        TimelinePanel.roomReadMarkerTsMap[this.props.room.roomId] = eventTs;

        if (inhibitSetState) {
            return;
        }

        // run the render cycle before calling the callback, so that
        // getReadMarkerPosition() returns the right thing.
        this.setState({
            readMarkerEventId: eventId,
        }, this.props.onReadMarkerUpdated);
    },

    render: function() {
        var MessagePanel = sdk.getComponent("structures.MessagePanel");
        var Loader = sdk.getComponent("elements.Spinner");

        // just show a spinner while the timeline loads.
        //
        // put it in a div of the right class (mx_RoomView_messagePanel) so
        // that the order in the roomview flexbox is correct, and
        // mx_RoomView_messageListWrapper to position the inner div in the
        // right place.
        //
        // Note that the click-on-search-result functionality relies on the
        // fact that the messagePanel is hidden while the timeline reloads,
        // but that the RoomHeader (complete with search term) continues to
        // exist.
        if (this.state.timelineLoading) {
            return (
                    <div className="mx_RoomView_messagePanel mx_RoomView_messageListWrapper">
                        <Loader />
                    </div>
            );
        }

        // give the messagepanel a stickybottom if we're at the end of the
        // live timeline, so that the arrival of new events triggers a
        // scroll.
        //
        // Make sure that stickyBottom is *false* if we can paginate
        // forwards, otherwise if somebody hits the bottom of the loaded
        // events when viewing historical messages, we get stuck in a loop
        // of paginating our way through the entire history of the room.
        var stickyBottom = !this._timelineWindow.canPaginate(EventTimeline.FORWARDS);

        return (
            <MessagePanel ref="messagePanel"
                    hidden={ this.props.hidden }
                    backPaginating={ this.state.backPaginating }
                    forwardPaginating={ this.state.forwardPaginating }
                    events={ this.state.events }
                    highlightedEventId={ this.props.highlightedEventId }
                    readMarkerEventId={ this.state.readMarkerEventId }
                    readMarkerVisible={ this.state.readMarkerVisible }
                    suppressFirstDateSeparator={ this.state.canBackPaginate }
                    showUrlPreview = { this.props.showUrlPreview }
                    ourUserId={ MatrixClientPeg.get().credentials.userId }
                    stickyBottom={ stickyBottom }
                    onScroll={ this.onMessageListScroll }
                    onFillRequest={ this.onMessageListFillRequest }
                    opacity={ this.props.opacity }
            />
        );
    },
});

module.exports = TimelinePanel;