✨ (clockface): add hourHand implementation

Author: yuanyu90221

clockface_sample/clockface/clockface.go

@@ -5,16 +5,21 @@ import (
 	"time"
 )
 
+const (
+	secondsInHalfClock = 30
+	secondsInClock     = 2 * secondsInHalfClock
+	minutesInHalfClock = 30
+	minutesInClock     = 2 * minutesInHalfClock
+	hoursInHalfClock   = 6
+	hoursInClock       = 2 * hoursInHalfClock
+)
+
 // A Point represents a two-dimensional Cartesian coordinate
 type Point struct {
 	X float64
 	Y float64
 }
 
-const secondHandLength = 90
-const clockCentreX = 150
-const clockCentreY = 150
-
 // SecondHand is the unit vector of the second hand of an analogue clock at time `t`
 // represented as a Point.
 func SecondHand(t time.Time) Point {
@@ -26,16 +31,16 @@ func SecondHand(t time.Time) Point {
 }
 
 func secondsInRadians(t time.Time) float64 {
-	return (math.Pi / (30 / (float64(t.Second()))))
+	return (math.Pi / (secondsInHalfClock / (float64(t.Second()))))
 }
 
 func secondHandPoint(t time.Time) Point {
 	return angleToPoint(secondsInRadians(t))
 }
 
 func minutesInRadians(t time.Time) float64 {
-	return (secondsInRadians(t) / 60) +
-		(math.Pi / (30 / float64(t.Minute())))
+	return (secondsInRadians(t) / minutesInClock) +
+		(math.Pi / (minutesInHalfClock / float64(t.Minute())))
 }
 
 func angleToPoint(angle float64) Point {
@@ -49,4 +54,11 @@ func minuteHandPoint(t time.Time) Point {
 	return angleToPoint(minutesInRadians(t))
 }
 
-const minuteHandLength = 80
+func hoursInRadians(t time.Time) float64 {
+	return (minutesInRadians(t) / hoursInClock) +
+		(math.Pi / (hoursInHalfClock / float64(t.Hour()%hoursInClock)))
+}
+
+func hourHandPoint(t time.Time) Point {
+	return angleToPoint(hoursInRadians(t))
+}

clockface_sample/clockface/clockface_acceptance_test.go

@@ -126,3 +126,29 @@ 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{}
+			clockface.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)
+			}
+		})
+	}
+}

clockface_sample/clockface/clockface_test.go

@@ -100,3 +100,43 @@ func TestMinuteHandPoint(t *testing.T) {
 		})
 	}
 }
+
+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(got, c.angle) {
+				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(21, 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)
+			}
+		})
+	}
+}

clockface_sample/clockface/svgWriter.go

@@ -6,12 +6,21 @@ import (
 	"time"
 )
 
+const (
+	secondHandLength = 90
+	minuteHandLength = 80
+	hourHandLength   = 50
+	clockCentreX     = 150
+	clockCentreY     = 150
+)
+
 // SVGWriter writes an SVG representation of an analogue clock, showing the time t, to the writer w.
 func SVGWriter(w io.Writer, t time.Time) {
 	io.WriteString(w, svgStart)
 	io.WriteString(w, bezel)
 	secondHand(w, t)
 	minuteHand(w, t)
+	hourHand(w, t)
 	io.WriteString(w, svgEnd)
 }
 
@@ -43,3 +52,8 @@ const svgStart = `<?xml version="1.0" encoding="UTF-8" standalone="no"?>
 const bezel = `<circle cx="150" cy="150" r="100" style="fill:#fff;stroke:#000;stroke-width:5px;"/>`
 
 const svgEnd = `</svg>`
+
+func hourHand(w io.Writer, t time.Time) {
+	p := makeHand(hourHandPoint(t), hourHandLength)
+	fmt.Fprintf(w, `<line x1="150" y1="150" x2="%.3f" y2="%.3f" style="fill:none;stroke:#000;stroke-width:3px;"/>`, p.X, p.Y)
+}