/* -------------------------- */		
/*        tracesPlugin        */		
/* -------------------------- */		

var tracesPlugin = function tracesPlugin(cls = "traces") {
 
 	let traceLineWidth = 2
	let traceStrokeStyleLight = "rgba(128, 0, 255, 0.02)"
	let traceStroke = '#FF2400' // "red"
	let traceOpacity = 0.7
	let traceFill = 'transparent'
	let traceLength = 5000
	let tracePath = d => "M" + d.join("L")
	let traces = []		// get your actions together

	var layerMark
	var layerEnter
	var parentclass = "traces"
	var cls = cls				// 
		
	var elemsUpdate 
	var elemsEnter 
	var elemsMerge 
	var elemsExit

	function tracesPlugin() { }
 
 	tracesPlugin.render = function () {
	
			layerMark = d3.select("svg").selectAll("." + parentclass).data(['cls'])
			layerEnter = layerMark.enter().append("g").attr("class", parentclass)
			
			elemsUpdate = d3.select("." + parentclass).selectAll("." + cls).data(["path"])
			elemsEnter = elemsUpdate.enter().insert("path")
			elemsMerge = elemsEnter.merge(elemsUpdate)
					.attr("class", cls)
					.attr("d", d => tracesPlugin.path())
					.style("fill", function(d, i) { return traceFill })
					.style("stroke", function(d) { return traceStroke })			
					.style("stroke-width", function(d) { return traceLineWidth })	
					.style("opacity",  traceOpacity)

			elemsExit = elemsUpdate.exit().remove()
	}

	tracesPlugin.addstep = function (step) {
		traces.push(step)														// add present
		traces.splice(0, traces.length - traceLength)	// remove past
	}

 	tracesPlugin.traces = function () {	
		return traces
	}

 	tracesPlugin.path = function () {	
		return tracePath(traces)
	}
	
	tracesPlugin.clear = function() {
			traces = []
			let p = d3.select("." + parentclass).selectAll("." + cls).remove()
	}	
	
		
	tracesPlugin.hc = function(_) {
			if (arguments.length < 1) return traceLength
			traceLength = _
			return tracesPlugin
	}	
			
	tracesPlugin.hs = function(_) {
			if (arguments.length < 1) return traceStroke
			traceStroke = _
			return tracesPlugin
	}	
	tracesPlugin.ho = function(_) {
			if (arguments.length < 1) return traceOpacity
			traceOpacity = _
			return tracesPlugin
	}	
	
	
	
	return tracesPlugin	
}
;