// twister_timeline.js
// 2013 Miguel Freitas
//
// Provides objects to keep track of timeline display state to request new posts efficiently.
//
// Currently is being used only for "home" timeline, but the list of users can be an arbitrary
// subset of users we follow. In other words: this objects may be used for displaying profiles
// of those users more efficiently than iterating through dht posts.


var _idTrackerMap = {};
var _idTrackerSpam = new idTrackerObj();
var _lastHaveMap = {};
var _refreshInProgress = false;
var _newPostsPending = 0;
var timelineLoaded = false;

/* object to keep tracking of post ids for a given user, that is, which
 * posts have already been received, processed, shown + which ones to request.
 * modes of operation:
 * "latestFirstTime" this is the first time the timeline is obtained, we known
 *                   nothing about the last post ids. there will be no gap since
 *                   timeline is empty on screen.
 * "latest" this is used when we have a timeline on screen but we want to update
 *          it with the latest posts. since getposts rpc may limit the number of
 *          posts to receive, a gap may be created. that is, between the most
 *          recent post of the previous update and the lower id received by getposts.
 * "fillgap" this is used to fill the gap after "latest" was used.
 * "older"  this is used to scroll down the timeline, to older posts than are
 *          currently being shown on screen.
 */
function idTrackerObj()
{
    this.latest = -1;
    this.oldest = -1;
    this.gapHigh = -1;
    this.gapLow = -1;

    // getRequest method creates a single user item of getposts rpc list parameter
    this.getRequest = function (mode) {
        if( mode == 'latest' || mode == 'latestFirstTime' ) {
            this.gapHigh = -1;
            this.gapLow = this.latest;
            return { since_id: this.latest };
        } else if( mode == 'fillgap') {
            return { max_id: this.gapHigh-1, since_id: this.gapLow };
        } else if( mode == 'older') {
            return ( this.oldest >= 0 ) ? { max_id: this.oldest-1 } : {};
        } else {
           console.log("getRequest: unknown mode");
        }
    }

    // receiveId method notifies that a post was received (and possibly shown)
    this.receivedId = function (mode, id, shown){
        if( id > this.latest ) this.latest = id;
        if( shown ) {
            if( this.oldest < 0 || id < this.oldest ) this.oldest = id;
        }
        if( mode == 'latest' ||
            mode == 'latestFirstTime' ||
            mode == 'fillgap') {
            if( this.gapHigh < 0 || id < this.gapHigh )
                this.gapHigh = id;
        } else if( mode == 'older') {
            // no gaps: posts are already received in descending order
        } else {
           console.log("receivedId: unknown mode");
        }
    }
}

/* object to maintain a request state for several users.
 * each user is tracked by idTrackerObj in global _idTrackerMap.
 */
function requestObj(users, mode, count, getspam)
{
    this.users = users;
    this.mode = mode; // 'latest', 'latestFirstTime' or 'older'
    this.count = count;
    this.getspam = getspam;

    // getRequest method returns the list parameter expected by getposts rpc
    this.getRequest = function() {
        var req = [];
        if( this.mode == 'done')
            return req;
        if( this.getspam ) {
            return _idTrackerSpam.getRequest(this.mode);
        }
        for( var i = 0; i < this.users.length; i++ ) {
            var user = this.users[i];
            if( !(user in _idTrackerMap) )
                _idTrackerMap[user] = new idTrackerObj();
            var r = _idTrackerMap[user].getRequest(this.mode);
            r.username = user;
            req.push(r);
        }
        return req;
    }

    // receiveId method notifies that a post was received (and possibly shown)
    this.reportProcessedPost = function(user, id, shown) {
        if( this.getspam ) {
            _idTrackerSpam.receivedId(this.mode, id, shown);
        }
        if( this.users.indexOf(user) >= 0 ) {
            _idTrackerMap[user].receivedId(this.mode, id, shown);
        }
    }

    // doneReportProcessing is called after an getposts response is processed
    // mode changing may require a new request (to fill gaps)
    this.doneReportProcessing = function(receivedCount) {
        if( this.mode == 'latest') this.mode = 'fillgap';
        if( this.mode == 'latestFirstTime') this.mode = 'done';
        if( this.mode == 'older') this.mode = 'done';
        if( receivedCount < this.count ) this.mode = 'done';
    }
}

// json rpc with requestObj as parameter
function requestGetposts(req)
{
    var r = req.getRequest();
    if( !req.getspam ) {
        if( r.length ) {
            twisterRpc("getposts", [req.count,r],
                       function(req, posts) {processReceivedPosts(req, posts);}, req,
                       function(req, ret) {console.log("ajax error:" + ret);}, req);
        }
    } else {
        twisterRpc("getspamposts", [req.count,r.max_id?r.max_id:-1,r.since_id?r.since_id:-1],
                   function(req, posts) {processReceivedPosts(req, posts);}, req,
                   function(req, ret) {console.log("ajax error:" + ret);}, req);
    }
}

// callback to getposts rpc when updating the timeline
// process the received posts (adding them to screen) and do another
// request if needed
function processReceivedPosts(req, posts)
{
    for( var i = 0; i < posts.length; i++ ) {
        var post = posts[i];
        var streamPost = postToElem(post, "original");
        var timePost = post["userpost"]["time"];
        streamPost.attr("data-time",timePost);

        // post will only be shown if appended to the stream list
        var streamPostAppended = false;

        // insert the post in timeline ordered by (you guessed) time
        // FIXME: lame! searching everything everytime. please optimize!
        var streamItemsParent = $.MAL.getStreamPostsParent();
        var streamItems = streamItemsParent.children();
        if( streamItems.length == 0) {
            // timeline is empty
            streamItemsParent.append( streamPost );
            streamPostAppended = true;
        } else {
            var j = 0;
            for( j = 0; j < streamItems.length; j++) {
                var streamItem = streamItems.eq(j);
                var timeItem = streamItem.attr("data-time");
                if( timeItem == undefined ||
                    timePost > parseInt(timeItem) ) {
                    // this post in stream is older, so post must be inserted above
                    streamItem.before(streamPost);
                    streamPostAppended = true;
                    break;
                }
            }
            if( j == streamItems.length ) {
                // no older posts in stream, so post is to be inserted below
                if( req.mode == "older" || req.mode == "latestFirstTime" ) {
                    // note: when filling gaps, the post must be discarded (not
                    // shown) since it can never be older than what we already
                    // have on timeline. this is a problem due to requesting from
                    // several users at the same time, as some older posts might
                    // be included to complete the <count> in getposts because
                    // other users may have already been excluded by since_id.
                    streamItemsParent.append( streamPost );
                    streamPostAppended = true;
                }
            }
        }

        if( streamPostAppended ) {
            streamPost.show();
        }
        req.reportProcessedPost(post["userpost"]["n"],post["userpost"]["k"], streamPostAppended);
    }
    req.doneReportProcessing(posts.length);

    if( req.mode == "done" ) {
        timelineLoaded = true;
        $.MAL.postboardLoaded();
        _refreshInProgress = false;
    } else {
        requestGetposts(req);
    }
}

// request timeline update for a given list of users
function requestTimelineUpdate(mode, count, timelineUsers, getspam)
{
    if( _refreshInProgress )
        return;
    $.MAL.postboardLoading();
    _refreshInProgress = true;
    if( timelineUsers.length ) {
        var req = new requestObj(timelineUsers, mode, count, getspam);
        requestGetposts(req);
    } else {
        console.log("requestTimelineUpdate: not following any users");
    }
    if( mode == "latest" || mode == "latestFirstTime" ) {
        _newPostsPending = 0;
        $.MAL.reportNewPosts(0);
    }
}

// getlasthave is called every second to check if followed users have posted anything new
function requestLastHave() {
    twisterRpc("getlasthave", [defaultScreenName],
           function(req, ret) {processLastHave(ret);}, null,
           function(req, ret) {console.log("ajax error:" + ret);}, null);
}

// handle getlasthave response. the increase in lasthave cannot be assumed to
// produce new items for timeline since some posts might be directmessages (which
// won't be returned by getposts, normally).
function processLastHave(userHaves)
{
    var reqConfirmNewPosts = [];
    var newPostsLocal = 0;
    for( var user in userHaves ) {
        if( userHaves.hasOwnProperty(user) ) {
            // checks for _idTrackerMap as well. the reason is that getlasthave
            // returns all users we follow, but the current timeline might be
            // for just a single user.
            if( user in _lastHaveMap && user in _idTrackerMap) {
                if( userHaves[user] > _lastHaveMap[user] ) {
                    newPostsLocal += userHaves[user] - _lastHaveMap[user];
                    reqConfirmNewPosts.push( {username:user, since_id:_lastHaveMap[user]} );
                }
            }
            _lastHaveMap[user] = userHaves[user];

            if( user == defaultScreenName ) {
                if( lastPostId == undefined || userHaves[user] > lastPostId ) {
                    incLastPostId(userHaves[user]);
                }
            }
        }
    }

    // now do a getposts to confirm the number of new haves with are effectively new public posts
    if( newPostsLocal ) {
        twisterRpc("getposts", [newPostsLocal, reqConfirmNewPosts],
               function(expected, posts) {processNewPostsConfirmation(expected, posts);}, newPostsLocal,
               function(req, ret) {console.log("ajax error:" + ret);}, null);
    }
}

// callback for getposts to update the number of new pending posts not shown in timeline
function processNewPostsConfirmation(expected, posts)
{
    _newPostsPending += posts.length;
    if( _newPostsPending ) {
        $.MAL.reportNewPosts(_newPostsPending);
    }
    if( posts.length < expected ) {
        // new DMs have probably been produced by users we follow.
        // check with getdirectmsgs
        requestDMsCount();
    }

    // TODO: possibly cache this response
}

function timelineChangedUser()
{
    _idTrackerMap = {};
    _idTrackerSpam = new idTrackerObj();
    _lastHaveMap = {};
    _refreshInProgress = false;
    _newPostsPending = 0;
    timelineLoaded = false;
}