A3: nearly there

go/TrafficLights/TrafficLight.go

@@ -31,6 +31,22 @@ var Colours = []Colour{
 	red, green, yellow,
 }
 
+func nextDirection(currentDirection CardinalDirection) CardinalDirection {
+	switch currentDirection {
+	case north:
+		return east
+	case south:
+		return west
+	case east:
+		return south
+	case west:
+		return north
+	default:
+		return north
+	}
+
+}
+
 func nextColour(currentColour Colour) Colour {
 	switch currentColour {
 	case red:
@@ -52,10 +68,10 @@ func main() {
 	var eastColour = make(chan Colour, 2)
 	var westColour = make(chan Colour, 2)
 
-	var northDirection = make(chan string, 4)
+	var northDirection = make(chan string, 2)
-	var southDirection = make(chan string, 4)
+	var southDirection = make(chan string, 2)
-	var eastDirection = make(chan string, 4)
+	var eastDirection = make(chan string, 2)
-	var westDirection = make(chan string, 4)
+	var westDirection = make(chan string, 2)
 
 	go TrafficLight(north, northColour, southColour, northDirection, eastDirection, southDirection)
 	go TrafficLight(south, southColour, northColour, southDirection, westDirection, northDirection)
@@ -65,27 +81,59 @@ func main() {
 	<-quitChannel
 }
 
-func TrafficLight(direction CardinalDirection, currentColour <-chan Colour, oppositeColour chan<- Colour, currentDirection <-chan string, nextDirection chan<- string, oppositeDirection chan<- string) {
+func TrafficLight(direction CardinalDirection, currentColour <-chan Colour, oppositeColour chan<- Colour, currentDirection <-chan string, nextDirectionChan chan<- string, oppositeDirection chan<- string) {
 	var colour = red
 
 	if direction != north && direction != south {
-		nextDirection <- "go"
+		nextDirectionChan <- string(nextDirection(direction))
+
 	}
 
 	for {
 		show(direction, colour)
 
-		oppositeColour <- nextColour(colour)
+		if colour == red {
-		select {
+			syncLight(currentDirection, oppositeDirection)
-		case msg := <-currentColour:
+			changeDirection(direction, currentDirection, nextDirectionChan)
-			if msg == nextColour(colour) {
-				colour = msg
-			}
 		}
+		colour = changeLight(colour, currentColour, oppositeColour)
 
 	}
 }
 
+func syncLight(currentDirection <-chan string, oppositeDirection chan<- string) {
+	oppositeDirection <- "sync"
+	select {
+	case msg := <-currentDirection:
+		if msg == "sync" {
+			return
+
+		}
+	}
+}
+
+func changeDirection(direction CardinalDirection, currentDirection <-chan string, nextDirectionChan chan<- string) {
+	nextDirectionChan <- string(nextDirection(direction))
+	select {
+	case msg := <-currentDirection:
+		if msg == string(direction) {
+			return
+		}
+	}
+}
+
+func changeLight(colour Colour, currentColour <-chan Colour, oppositeColour chan<- Colour) Colour {
+	oppositeColour <- nextColour(colour)
+
+	select {
+	case msg := <-currentColour:
+		if msg == nextColour(colour) {
+			return nextColour(colour)
+		}
+	}
+	return colour
+}
+
 func show(direction CardinalDirection, colour Colour) {
 	fmt.Println(string(direction), " : ", string(colour))
 }