From 33a19d02b5d7f3cb8ef25371f3893809638a4f6c Mon Sep 17 00:00:00 2001
From: Mike Pennisi <mike@mikepennisi.com>
Date: Sat, 14 Dec 2013 17:11:31 -0500
Subject: [PATCH] Implement `Chart#demux`

Provide mixin users with a means to split the input data across mixins.
---
 src/chart.js        |  9 +++++--
 test/tests/chart.js | 62 +++++++++++++++++++++++++++++++++++++--------
 2 files changed, 58 insertions(+), 13 deletions(-)

diff --git a/src/chart.js b/src/chart.js
index 555a366..aa2fea8 100644
--- a/src/chart.js
+++ b/src/chart.js
@@ -127,7 +127,7 @@ Chart.prototype.mixin = function(mixinName, chart) {
 
 Chart.prototype.draw = function(data) {
 
-	var layerName, mixinName;
+	var layerName, mixinName, mixinData;
 
 	data = transformCascade.call(this, this, data);
 
@@ -136,7 +136,12 @@ Chart.prototype.draw = function(data) {
 	}
 
 	for (mixinName in this._mixins) {
-		this._mixins[mixinName].draw(data);
+		if (this.demux) {
+			mixinData = this.demux(mixinName, data);
+		} else {
+			mixinData = data;
+		}
+		this._mixins[mixinName].draw(mixinData);
 	}
 };
 
diff --git a/test/tests/chart.js b/test/tests/chart.js
index 77896f2..aa161cb 100644
--- a/test/tests/chart.js
+++ b/test/tests/chart.js
@@ -89,26 +89,66 @@ suite("d3.chart", function() {
 		});
 	});
 
-	suite("#mixin", function() {
+	suite("Mixins", function() {
 		setup(function() {
 			d3.chart("test", {});
 			this.myChart = d3.select("#test").chart("test");
 			var mixinChart = this.mixinChart = d3.select("body").chart("test");
 			sinon.spy(mixinChart, "draw");
 		});
-		test("returns the requested mixin", function() {
-			this.myChart.mixin("myMixin", this.mixinChart);
+		suite("#mixin", function() {
+			test("returns the requested mixin", function() {
+				this.myChart.mixin("myMixin", this.mixinChart);
 
-			assert.equal(this.myChart.mixin("myMixin"), this.mixinChart);
+				assert.equal(this.myChart.mixin("myMixin"), this.mixinChart);
+			});
+			test("connects the specified chart", function() {
+				var data = [23, 45];
+				this.myChart.mixin("myMixin", this.mixinChart);
+				this.myChart.draw(data);
+
+				assert.equal(this.mixinChart.draw.callCount, 1);
+				assert.equal(this.mixinChart.draw.args[0].length, 1);
+				assert.deepEqual(this.mixinChart.draw.args[0][0], data);
+			});
 		});
-		test("connects the specified chart", function() {
-			var data = [23, 45];
-			this.myChart.mixin("myMixin", this.mixinChart);
-			this.myChart.draw(data);
 
-			assert.equal(this.mixinChart.draw.callCount, 1);
-			assert.equal(this.mixinChart.draw.args[0].length, 1);
-			assert.deepEqual(this.mixinChart.draw.args[0][0], data);
+		suite("#demux", function() {
+			var data = {
+				series1: [1, 2, 3],
+				series2: [4, 5, 6]
+			};
+			setup(function() {
+				this.mixinChart2 = d3.select("body").chart("test");
+				sinon.spy(this.mixinChart2, "draw");
+				this.myChart.mixin("mixin1", this.mixinChart);
+				this.myChart.mixin("mixin2", this.mixinChart2);
+			});
+			test("uses provided function to demultiplex data", function() {
+				this.myChart.demux = function(mixinName, data) {
+					if (mixinName === "mixin1") {
+						return data.series1;
+					}
+					return data;
+				};
+				this.myChart.draw(data);
+
+				assert.deepEqual(
+					this.mixinChart.draw.args,
+					[[[1, 2, 3]]],
+					"Demuxes data passed to charts with registered function"
+				);
+				assert.deepEqual(
+					this.mixinChart2.draw.args[0][0].series1,
+					data.series1,
+					"Unmodified data passes through to mixins directly"
+				);
+				assert.deepEqual(
+					this.mixinChart2.draw.args[0][0].series2,
+					data.series2,
+					"Unmodified data passes through to mixins directly"
+				);
+			});
 		});
 	});