var iD = {};
iD.Draw = function() {
    var event = d3.dispatch(draw, 'draw'),
        x0, x1,
        y0, y1;

    var feature = {
        type: 'Feature',
        geometry: {
            type: 'LineString',
            coordinates: []
        }
    };

    function draw() {
        this
            .on('mousemove.draw', mousemove)
            .on('click.draw', mousedown);
    }

    // move an elastic band that shows where the next point
    // will be
    function mousemove(e) {
        var target = this;
        function mouse() {
            var touches = d3.event.changedTouches;
            return touches ? d3.touches(target, touches)[0] : d3.mouse(target);
        }
        var ll = projection.invert(mouse());
        var elastic = {
            type: 'Feature',
            geometry: {
                type: 'LineString',
                coordinates: []
            }
        };
        if (!feature.geometry.coordinates.length) {
            feature.geometry.coordinates[0] = ll;
            event.draw(feature);
            feature.geometry.coordinates = [];
        } else {
            var l = feature.geometry.coordinates.length - 1;
            elastic.geometry.coordinates = [
                feature.geometry.coordinates[l],
                ll];
            event.draw(feature, elastic);
        }
    }

    // add a point
    function mousedown(e) {
        var target = this;
        function mouse() {
            var touches = d3.event.changedTouches;
            return touches ? d3.touches(target, touches)[0] : d3.mouse(target);
        }
        var ll = projection.invert(mouse());
        feature.geometry.coordinates.push(ll);
        event.draw(feature);
        d3.event.stopPropagation();
    }

    return d3.rebind(draw, event, "on");
};