iD.MapillaryImageLayer = function(context) {
    var mapillary = iD.services.mapillary(),
        debouncedRedraw = _.debounce(function () { context.pan([0,0]); }, 1000),
        rtree = rbush(),
        enabled = false,
        layer;


    function showThumbnail(imageKey) {
        var thumb = mapillary.selectedThumbnail();

        d3.selectAll('.layer-mapillary-images .viewfield-group, .layer-mapillary-signs .icon-sign')
            .classed('selected', function(d) { return d.key === thumb; });

        mapillary.showThumbnail(context.container(), imageKey);
    }

    function hideThumbnail() {
        d3.selectAll('.layer-mapillary-images .viewfield-group, .layer-mapillary-signs .icon-sign')
            .classed('selected', false);

        mapillary.hideThumbnail(context.container());
    }

    function showLayer() {
        layer
            .style('display', 'block')
            .style('opacity', 0)
            .transition()
            .duration(500)
            .style('opacity', 1)
            .each('end', debouncedRedraw);
    }

    function hideLayer() {
        debouncedRedraw.cancel();
        hideThumbnail();
        layer
            .transition()
            .duration(500)
            .style('opacity', 0)
            .each('end', function() {
                layer
                    .style('display', 'none')
                    .selectAll('.viewfield-group')
                    .remove();
            });
    }

    function transform(d) {
        var t = iD.svg.PointTransform(context.projection)(d);
        if (d.ca) t += ' rotate(' + Math.floor(d.ca) + ',0,0)';
        return t;
    }

    function imagesLoaded(data) {
        if (!data.features.length) return;

        var images = [],
            image, loc;

        for (var i = 0; i < data.features.length; i++) {
            image = data.features[i];
            loc = image.geometry.coordinates;
            images.push([loc[0], loc[1], loc[0], loc[1], {
                key: image.properties.key,
                ca: image.properties.ca,
                loc: loc
            }]);
        }

        rtree.load(images);
        debouncedRedraw();
    }

    function drawMarkers() {
        var data = rtree
            .search(context.map().extent().rectangle())
            .map(function(d) { return d[4]; });

        var markers = layer.selectAll('.viewfield-group')
            .data(data, function(d) { return d.key; });

        // Enter
        var enter = markers.enter()
            .append('g')
            .attr('class', 'viewfield-group');

        enter.append('path')
            .attr('class', 'viewfield')
            .attr('transform', 'scale(1.5,1.5),translate(-8, -13)')
            .attr('d', 'M 6,9 C 8,8.4 8,8.4 10,9 L 16,-2 C 12,-5 4,-5 0,-2 z');

        enter.append('circle')
            .attr('dx', '0')
            .attr('dy', '0')
            .attr('r', '6');

        // Update
        markers
            .attr('transform', transform);

        // Exit
        markers.exit()
            .remove();
    }


    function render(selection) {
        layer = selection.selectAll('svg')
            .data([0]);

        // Enter
        layer.enter()
            .append('svg')
            .style('display', enabled ? 'block' : 'none')
            .on('click', function() {   // deselect/select
                var image = d3.event.target.__data__;
                if (image.key === mapillary.selectedThumbnail()) {
                    hideThumbnail();
                } else {
                    mapillary.selectedThumbnail(image.key);
                    context.map().centerEase(image.loc);
                    showThumbnail(image.key);
                }
            })
            .on('mouseover', function() {
                showThumbnail(d3.event.target.__data__.key);
            })
            .on('mouseout', function() {
                var thumb = mapillary.selectedThumbnail();
                if (thumb) {
                    showThumbnail(thumb);
                } else {
                    hideThumbnail();
                }
            });

        if (enabled) {
            drawMarkers();
            mapillary.loadImages(context.projection, layer.dimensions());
        }
    }

    render.enable = function(_) {
        if (!arguments.length) return enabled;
        enabled = _;
        if (enabled) {
            showLayer();
        } else {
            hideLayer();
        }
        return render;
    };

    render.dimensions = function(_) {
        if (!arguments.length) return layer.dimensions();
        layer.dimensions(_);
        return render;
    };


    mapillary
        .on('loadedImages', imagesLoaded);

    return render;
};