source: extensions/rv_gmaps/trunk/template/data_loader.js @ 6245

function PwgDataLoader( map, opts )
{
        this._map = map;
        this.options = Object.extend(
                {
                        reload_data_timeout: 1800,
                        rectangle_of_confusion: G_DEFAULT_ICON.iconSize
                }
                , opts || {} );
        this.options.rectangle_of_confusion = new GSize( this.options.rectangle_of_confusion.width, this.options.rectangle_of_confusion.height );
        if (this.options.rectangle_of_confusion.width<16) this.options.rectangle_of_confusion.width=16;
        if (this.options.rectangle_of_confusion.height<16) this.options.rectangle_of_confusion.height=16;
}


// returns the number of digits (between 0 and 6) to round a lat/lon so that it does not vary by more than factor*pow(-exp)
getLatLonDigits = function(d, factor, exp)
{
        if (d<0) return getLatLonDigits(-d,factor,exp);
        var digits = Math.ceil( exp - Math.log(d*factor)/Math.LN10 );
        return digits<0 ? 0 : (digits>6 ? 6 : digits);
}

Math.roundN = function(d, digits) { var c = Math.pow(10,digits); return Math.round(d*c)/c; }


PwgDataLoader.prototype =  {


_urlMapData: null,
_timerReloadData: null,
_dataLoading: false,

_previousLoadDataReq : {box: null, zoom:0, resultBounds:null},

start: function(urlMapData)
{
        this._urlMapData = urlMapData;
        GEvent.bind( this._map, "movestart", this, this.clearTimerReloadData );
        GEvent.bind( this._map, "moveend", this, this._onMapMoveEnd );
        this._loadData();
},

terminate: function()
{
        this.clearTimerReloadData();
        this._map = null;
},

clearTimerReloadData : function()
{
        if (this._timerReloadData)
        {
                clearTimeout( this._timerReloadData );
                this._timerReloadData = null;
                return true;
        }
        return false;
},

_onMapMoveEnd: function()
{
        this.clearTimerReloadData();
        this._timerReloadData = setTimeout(  this._onTimeoutLoadData.bind(this), this.options.reload_data_timeout );
},


_onTimeoutLoadData: function ()
{
        if (this._dataLoading) return; // still in progress
        this.clearTimerReloadData();
        this._loadData();
},

_loadData: function()
{
        var bounds = this._map.getBounds();

        // BEGIN BUG in maps api 2.185 up to "today" 2.193 - when map wraps horizontally more than 360 deg - the getBounds is wrong
        if ( this._map.getZoom() <= 2 || this._map.getZoom() == 3 && this._map.getSize().width > 1000 )
        {
                bounds = new GLatLngBounds(
                                new GLatLng( bounds.getSouthWest().lat(),  -180 ),
                                new GLatLng( bounds.getNorthEast().lat(),  180 )
                        );
        }
        // END BUG
        var latRange = bounds.toSpan().lat();
        var latPrec = latRange * this.options.rectangle_of_confusion.height / this._map.getSize().height;

        var lonRange = bounds.toSpan().lng();
        var lonPrec = ( lonRange>=0 ? lonRange : 360-lonRange )* this.options.rectangle_of_confusion.width / this._map.getSize().width;

        if ( this._previousLoadDataReq.box!=null )
        { // not the first time
                if ( this._previousLoadDataReq.box.containsBounds( bounds ) )
                {
                        if ( this._previousLoadDataReq.resultBounds == null )
                                return; // no images here
                        if ( this._map.getZoom() <= this._previousLoadDataReq.zoom )
                                return;
                        else
                        {
                                if (
                                        this._map.getZoom() == this._previousLoadDataReq.zoom + 1
                                        && this._map.getZoom() < this._map.getBoundsZoomLevel(this._previousLoadDataReq.resultBounds)
                                        )
                                {
                                        if (document.is_debug) GLog.write('no load: zoom crt: '+this._map.getZoom()+'; prev: '+this._previousLoadDataReq.zoom+'; target: '+this._map.getBoundsZoomLevel(this._previousLoadDataReq.resultBounds));
                                        return;
                                }
                        }
                }
                else
                {
                }
        }

        var nd=0, sd=0, ed=0, wd=0;
        if ( !bounds.isFullLat() )
        {
                nd = latRange*12/100;
                sd = latRange*4/100;
        }
        if ( !bounds.isFullLng() )
        {
                ed = lonRange*9/100;
                wd = lonRange*7/100;
        }
        var digits = Math.max( getLatLonDigits(latRange,4,2), getLatLonDigits(lonRange,4,2) );
        var box = new GLatLngBounds(
                        new GLatLng( Math.roundN(bounds.getSouthWest().lat()-sd,digits), Math.roundN( bounds.getSouthWest().lng()-wd,digits ) ),
                        new GLatLng( Math.roundN(bounds.getNorthEast().lat()+nd,digits), Math.roundN( bounds.getNorthEast().lng()+ed,digits) )
                );

        var url = this._urlMapData;
        url += "&box=" + box.getSouthWest().toUrlValue(5) + "," + box.getNorthEast().toUrlValue(5);
        url += "&lap=" +  Math.roundN( latPrec, getLatLonDigits(latPrec,1,1) ).toString();
        url += "&lop=" +  Math.roundN( lonPrec, getLatLonDigits(lonPrec,1,1) ).toString();

        if (document.is_debug) {
                GLog.write( "bounds: " + this._map.getBounds().getSouthWest().toUrlValue() + " " + this._map.getBounds().getNorthEast().toUrlValue() +"; zoom: "+this._map.getZoom() +"; size: "+this._map.getSize().toString() +"; c: "+this._map.getCenter().toUrlValue() );
                GLog.writeUrl( url );
        }

        this._previousLoadDataReq.box = box;
        this._previousLoadDataReq.zoom = this._map.getZoom();
        this._previousLoadDataReq.resultBounds = null;
        this._dataLoading = true;

        try {
                GEvent.trigger( this, "dataloading" );
                GDownloadUrl(url, this._onDataReceived.bind(this) );
        }
        catch (e) {
                this._dataLoading = false;
                this._previousLoadDataReq.box=null;
                GEvent.trigger( this, "dataloadfailed", 600, e );
        }
},

_onDataReceived: function(data, responseCode)
{
        var resp;
        try
        {
                if (responseCode!=200)
                {
                        this._previousLoadDataReq.box=null;
                        GEvent.trigger( this, "dataloadfailed", responseCode, null );
                }
                else
                try
                {
                        eval('resp = ' + data);
                        if (resp.nb_items == undefined)
                                throw new Error( "DATA DECODING ERROR" );

                        this._previousLoadDataReq.resultBounds = resp.bounds;
                        if (document.is_debug && resp.debug) GLog.write( resp.debug );
                        GEvent.trigger( this, "dataloaded", resp );
                }
                catch (e)       {
                        this._previousLoadDataReq.box=null;
                        GEvent.trigger( this, "dataloadfailed", responseCode, e );
                        var s = e.message;
                        s += '\n' + data.substr(0,1000);
                        alert( s );
                }
        }
        finally {
                this._dataLoading = false;
        }
}

}