First commit

.gitignore

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+# File created using '.gitignore Generator' for Visual Studio Code: https://bit.ly/vscode-gig
+
+# Created by https://www.gitignore.io/api/macos,visualstudiocode,terraform,windows
+# Edit at https://www.gitignore.io/?templates=macos,visualstudiocode,terraform,windows
+
+### macOS ###
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+### Terraform ###
+# Local .terraform directories
+**/.terraform/*
+
+# .tfstate files
+*.tfstate
+*.tfstate.*
+*.plan
+
+# Crash log files
+crash.log
+
+# Ignore any .tfvars files that are generated automatically for each Terraform run. Most
+# .tfvars files are managed as part of configuration and so should be included in
+# version control.
+#
+# example.tfvars
+
+# Ignore override files as they are usually used to override resources locally and so
+# are not checked in
+override.tf
+override.tf.json
+*_override.tf
+*_override.tf.json
+secrets.tfvars
+
+# Include override files you do wish to add to version control using negated pattern
+#
+# !example_override.tf
+
+### VisualStudioCode ###
+.vscode/*
+#!.vscode/settings.json
+#!.vscode/tasks.json
+#!.vscode/launch.json
+#!.vscode/extensions.json
+
+### VisualStudioCode Patch ###
+# Ignore all local history of files
+.history
+
+### Windows ###
+# Windows thumbnail cache files
+Thumbs.db
+ehthumbs.db
+ehthumbs_vista.db
+
+# Dump file
+*.stackdump
+
+# Folder config file
+[Dd]esktop.ini
+
+# Recycle Bin used on file shares
+$RECYCLE.BIN/
+
+# Windows Installer files
+*.cab
+*.msi
+*.msix
+*.msm
+*.msp
+
+# Windows shortcuts
+*.lnk
+
+# End of https://www.gitignore.io/api/macos,visualstudiocode,terraform,windows
+
+# Custom rules (everything added below won't be overriden by 'Generate .gitignore File' if you use 'Update' option)
+.vscode/*
+
+.idea

clockface.go

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+package clockface

clockface/main.go

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+package clockface
+
+import (
+	"math"
+	"time"
+)
+
+package clockface
+
+import (
+"git.nerdfortress.dev/mitch/gotdd/clockface"
+"math"
+"time"
+)
+
+const secondHandLength = 90
+const clockCentreX = 150
+const clockCentreY = 150
+
+type Point struct {
+	X float64
+	Y float64
+}
+
+func SecondHand(t time.Time) Point {
+	p := secondHandPoint(t)
+	p = Point{p.X * secondHandLength, p.Y * secondHandLength} //scale
+	p = Point{p.X, -p.Y}                                      //flip
+	p = Point{p.X + clockCentreX, p.Y + clockCentreY}         //translate
+	return p
+}
+
+func secondsInRadians(t time.Time) float64 {
+	return math.Pi / (30 / (float64(t.Second())))
+}
+
+func secondHandPoint(t time.Time) Point {
+	angle := secondsInRadians(t)
+	x := math.Sin(angle)
+	y := math.Cos(angle)
+	return Point{x, y}
+}

clockface_acceptance_test.go

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+package clockface
+
+import (
+	"testing"
+	"time"
+)
+
+package clockface
+
+import (
+"testing"
+"time"
+)
+
+func TestSecondHandAtMidnight(t *testing.T) {
+	tm := time.Date(1337, time.January, 1, 0, 0, 0, 0, time.UTC)
+
+	want := Point{X: 150, Y: 150 - 90}
+	got := SecondHand(tm)
+
+	if got != want {
+		t.Errorf("Got %v, want %v", got, want)
+	}
+}
+
+func TestSecondHandAt30Seconds(t *testing.T) {
+	tm := time.Date(1337, time.January, 1, 0, 0, 30, 0, time.UTC)
+
+	want := Point{X: 150, Y: 150 + 90}
+	got := SecondHand(tm)
+
+	if got != want {
+		t.Errorf("Got %v, wanted %v", got, want)
+	}
+}

clockface_test.go

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+package clockface
+
+import (
+	"math"
+	"testing"
+	"time"
+)
+
+package clockface
+
+import (
+"math"
+"testing"
+"time"
+)
+
+func simpleTime(hours, minutes, seconds int) time.Time {
+	return time.Date(312, time.October, 28, hours, minutes, seconds, 0, time.UTC)
+}
+
+func testName(t time.Time) string {
+	return t.Format("15:04:05")
+}
+
+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 !roughlyEqualFloat64(got, c.angle) {
+				t.Fatalf("Wanted %v radians, but got %v", c.angle, got)
+			}
+		})
+	}
+}
+
+func TestSecondHandVector(t *testing.T) {
+	cases := []struct {
+		time  time.Time
+		point Point
+	}{
+		{simpleTime(0, 0, 30), Point{0, -1}},
+		{simpleTime(0, 0, 45), Point{-1, 0}},
+	}
+
+	for _, c := range cases {
+		t.Run(testName(c.time), func(t *testing.T) {
+			got := secondHandPoint(c.time)
+			if !roughlyEqualPoint(got, c.point) {
+				t.Fatalf("Wanted %v Point, but got %v", c.point, got)
+			}
+		})
+	}
+}
+
+func roughlyEqualFloat64(a, b float64) bool {
+	const equalityThreshold = 1e-7
+	return math.Abs(a-b) < equalityThreshold
+}
+
+func roughlyEqualPoint(a, b Point) bool {
+	return roughlyEqualFloat64(a.X, b.X) &&
+		roughlyEqualFloat64(a.Y, b.Y)
+}

go.mod

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+module clockface
+
+go 1.17