clockface: add hours

clockface/clockface.go

@@ -14,6 +14,7 @@ type Point struct {
 }
 
 const (
+	hourHandLength   = 50
 	minuteHandLength = 80
 	secondHandLength = 90
 	clockCentreX     = 150
@@ -37,6 +38,7 @@ func SVGWriter(w io.Writer, t time.Time) {
 	io.WriteString(w, bezel)
 	secondHand(w, t)
 	minuteHand(w, t)
+	hourHand(w, t)
 	io.WriteString(w, svgEnd)
 }
 
@@ -52,6 +54,12 @@ func minuteHand(w io.Writer, t time.Time) {
 	makeHand(w, minuteHandLength, p)
 }
 
+// MinuteHand is the unit vector of the minute hand of an analogue clock at the time `t` represented as a Point
+func hourHand(w io.Writer, t time.Time) {
+	p := hourHandPoint(t)
+	makeHand(w, hourHandLength, p)
+}
+
 func makeHand(w io.Writer, length float64, p Point) {
 	p = Point{p.X * length, p.Y * length}             // scale
 	p = Point{p.X, -p.Y}                              // flip
@@ -64,6 +72,14 @@ func makeHand(w io.Writer, length float64, p Point) {
 	)
 }
 
+func hoursInRadians(t time.Time) float64 {
+	return (minutesInRadians(t) / 12) + math.Pi/(6/float64(t.Hour()%12))
+}
+
+func hourHandPoint(t time.Time) Point {
+	return angleToPoint(hoursInRadians(t))
+}
+
 func minutesInRadians(t time.Time) float64 {
 	return (secondsInRadians(t) / 60) + math.Pi/(30/float64(t.Minute()))
 }

clockface/clockface_acceptance_test.go

@@ -65,7 +65,6 @@ func TestSVGWriterMinuteHand(t *testing.T) {
 		line Line
 	}{
 		{simpleTime(0, 0, 0), Line{150, 150, 150, 70}},
-		// {simpleTime(0, 0, 30), Line{150, 150, 150, 240}},
 	}
 
 	for _, c := range cases {
@@ -87,6 +86,33 @@ func TestSVGWriterMinuteHand(t *testing.T) {
 	}
 }
 
+func TestSVGWriterHourHand(t *testing.T) {
+	cases := []struct {
+		time time.Time
+		line Line
+	}{
+		{simpleTime(6, 0, 0), Line{150, 150, 150, 200}},
+	}
+
+	for _, c := range cases {
+		t.Run(testName(c.time), func(t *testing.T) {
+			b := bytes.Buffer{}
+			SVGWriter(&b, c.time)
+
+			svg := Svg{}
+			xml.Unmarshal(b.Bytes(), &svg)
+
+			if !containsLine(c.line, svg.Line) {
+				t.Errorf(
+					"Expected to find the hour hand line %+v in the SVG lines %v",
+					c.line,
+					svg.Line,
+				)
+			}
+		})
+	}
+}
+
 func containsLine(l Line, ls []Line) bool {
 	for _, line := range ls {
 		if line == l {

clockface/clockface_test.go

@@ -6,6 +6,47 @@ import (
 	"time"
 )
 
+func TestHoursInRadians(t *testing.T) {
+	cases := []struct {
+		time  time.Time
+		angle float64
+	}{
+		{simpleTime(6, 0, 0), math.Pi},
+		{simpleTime(0, 0, 0), 0},
+		{simpleTime(21, 0, 0), math.Pi * 1.5},
+		{simpleTime(0, 1, 30), math.Pi / ((6 * 60 * 60) / 90)},
+	}
+
+	for _, c := range cases {
+		t.Run(testName(c.time), func(t *testing.T) {
+			got := hoursInRadians(c.time)
+
+			if !roughlyEqualFloat64(c.angle, got) {
+				t.Fatalf("Wanted %v radians, but got %v", c.angle, got)
+			}
+		})
+	}
+}
+
+func TestHourHandPoint(t *testing.T) {
+	cases := []struct {
+		time  time.Time
+		point Point
+	}{
+		{simpleTime(6, 0, 0), Point{0, -1}},
+		{simpleTime(9, 0, 0), Point{-1, 0}},
+	}
+
+	for _, c := range cases {
+		t.Run(testName(c.time), func(t *testing.T) {
+			got := hourHandPoint(c.time)
+			if !roughlyEqualPoint(got, c.point) {
+				t.Fatalf("Wanted %v Point, but got %v", c.point, got)
+			}
+		})
+	}
+}
+
 func TestMinutesInRadians(t *testing.T) {
 	cases := []struct {
 		time  time.Time
@@ -26,28 +67,6 @@ func TestMinutesInRadians(t *testing.T) {
 	}
 }
 
-func TestSecondsInRadians(t *testing.T) {
-	cases := []struct {
-		time  time.Time
-		angle float64
-	}{
-		{simpleTime(0, 0, 30), math.Pi},
-		{simpleTime(0, 0, 0), 0},
-		{simpleTime(0, 0, 45), (math.Pi / 2) * 3},
-		{simpleTime(0, 0, 7), (math.Pi / 30) * 7},
-	}
-
-	for _, c := range cases {
-		t.Run(testName(c.time), func(t *testing.T) {
-			got := secondsInRadians(c.time)
-
-			if c.angle != got {
-				t.Fatalf("Wanted %v radians, but got %v", c.angle, got)
-			}
-		})
-	}
-}
-
 func TestMinuteHandPoint(t *testing.T) {
 	cases := []struct {
 		time  time.Time
@@ -67,6 +86,28 @@ func TestMinuteHandPoint(t *testing.T) {
 	}
 }
 
+func TestSecondsInRadians(t *testing.T) {
+	cases := []struct {
+		time  time.Time
+		angle float64
+	}{
+		{simpleTime(0, 0, 30), math.Pi},
+		{simpleTime(0, 0, 0), 0},
+		{simpleTime(0, 0, 45), (math.Pi / 2) * 3},
+		{simpleTime(0, 0, 7), (math.Pi / 30) * 7},
+	}
+
+	for _, c := range cases {
+		t.Run(testName(c.time), func(t *testing.T) {
+			got := secondsInRadians(c.time)
+
+			if c.angle != got {
+				t.Fatalf("Wanted %v radians, but got %v", c.angle, got)
+			}
+		})
+	}
+}
+
 func TestSecondHandPoint(t *testing.T) {
 	cases := []struct {
 		time  time.Time