Implemented picking turn method

lib/gather/gather.js

@@ -171,7 +171,31 @@ Gather.prototype.modifyGatherer = (user, callback) => {
 	return this.gatherers
 		.filter(gatherer => gatherer.id === user.id)
 		.forEach(callback);
-}
+};
+
+// Determines picking order of teams
+// Marine 1 pick first
+// 2 picks for each team subsequently
+
+Gather.prototype.pickingTurn = () => {
+	if (this.current !== 'selection') return null;
+	let alienCount = this.aliens().length;
+	let marineCount = this.marines().length;
+	let total = marineCount + alienCount;
+	if (alienCount + marineCount === 2) return "marine";
+	if (marineCount > alienCount) return "alien";
+	if (marineCount < alienCount) return "marine";
+	switch (total) {
+		case 4:
+			return "alien";
+		case 6:
+			return "marine";
+		case 8:
+			return "alien";
+		case 10:
+			return "marine";
+	}
+};
 
 Gather.prototype.moveToMarine = user => {
 	if (this.marines().length >= this.TEAM_SIZE) return;

spec/gather.js

@@ -217,6 +217,51 @@ describe("Gather Model:", function () {
 		});
 	});
 
+	describe("pickingTurn", function () {
+		var marineLeader, alienLeader;
+		beforeEach(function () {
+			gatherers.forEach(function (gatherer, index) {
+				gather.addGatherer(gatherer);
+			});
+			gatherers.forEach(function (gatherer, index) {
+				let candidate = gather.gatherers[index % 2];
+				gather.selectLeader(gatherer, candidate);
+			});
+			marineLeader = gather.marineLeader();
+			alienLeader = gather.alienLeader();
+			assert.isNotNull(marineLeader);
+			assert.isNotNull(alienLeader);
+			assert.equal(gather.current, "selection");
+		});
+		it ("returns null if current state is not selection", function () {
+			gather = Gather();
+			assert.isNull(gather.pickingTurn());
+		});
+		it ("gives first pick to aliens, then 2 for each side after", function () {
+			var gathererCursor = 2; // Picking i=2 gatherer next
+			var assertMarineNextMove = function () {
+				assert.equal(gather.pickingTurn(), "marine");
+				gather.moveToMarine(gather.gatherers[gathererCursor], marineLeader);
+				gathererCursor++;
+			};
+			var assertAlienNextMove = function () {
+				assert.equal(gather.pickingTurn(), "alien");
+				gather.moveToAlien(gather.gatherers[gathererCursor], alienLeader);	
+				gathererCursor++;
+			};
+			assertMarineNextMove();
+			assertAlienNextMove();
+			assertAlienNextMove();
+			assertMarineNextMove();
+			assertMarineNextMove();
+			assertAlienNextMove();
+			assertAlienNextMove();
+			assertMarineNextMove();
+			assertMarineNextMove();
+			assertAlienNextMove();
+		});
+	});
+
 	describe("moveToLobby", function () {
 		it ("moves a player to lobby", function () {
 			gather.addUser(user);