From e81ceecffc4107ac2fc1fdc797d76c1cc5d1b07b Mon Sep 17 00:00:00 2001
From: Marc Di Luzio <marc.diluzio@gmail.com>
Date: Fri, 5 Jun 2020 15:48:44 +0100
Subject: [PATCH] Add more maths functions for the Vectors

---
 pkg/game/geom.go      |  24 ++++++
 pkg/game/geom_test.go | 171 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 195 insertions(+)
 create mode 100644 pkg/game/geom_test.go

diff --git a/pkg/game/geom.go b/pkg/game/geom.go
index 7d45198..f65680b 100644
--- a/pkg/game/geom.go
+++ b/pkg/game/geom.go
@@ -1,5 +1,7 @@
 package game
 
+import "math"
+
 // Vector desribes a 3D vector
 type Vector struct {
 	X float64 `json:"x"`
@@ -11,3 +13,25 @@ func (v *Vector) Add(v2 Vector) {
 	v.X += v2.X
 	v.Y += v2.Y
 }
+
+// Added calculates a new vector
+func (v Vector) Added(v2 Vector) Vector {
+	v.Add(v2)
+	return v
+}
+
+// Negated returns a negated vector
+func (v Vector) Negated() Vector {
+	return Vector{-v.X, -v.Y}
+}
+
+// Length returns the length of the vector
+func (v Vector) Length() float64 {
+	return math.Sqrt(v.X*v.X + v.Y*v.Y)
+}
+
+// Distance returns the distance between two vectors
+func (v Vector) Distance(v2 Vector) float64 {
+	// Negate the two vectors and calciate the length
+	return v.Added(v2.Negated()).Length()
+}
diff --git a/pkg/game/geom_test.go b/pkg/game/geom_test.go
new file mode 100644
index 0000000..af24cc5
--- /dev/null
+++ b/pkg/game/geom_test.go
@@ -0,0 +1,171 @@
+package game
+
+import (
+	"math"
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type VectorTest struct {
+	name string
+	vec  Vector
+	arg  Vector
+	want Vector
+}
+
+var additionTests = []VectorTest{
+	{
+		name: "Basic addition 1",
+		vec: Vector{
+			X: 0.0,
+			Y: 0.0,
+		},
+		arg: Vector{
+			1.0,
+			1.0,
+		},
+		want: Vector{
+			1.0,
+			1.0,
+		},
+	},
+	{
+		name: "Basic addition 2",
+		vec: Vector{
+			X: 1.0,
+			Y: 2.0,
+		},
+		arg: Vector{
+			3.0,
+			4.0,
+		},
+		want: Vector{
+			4.0,
+			6.0,
+		},
+	},
+}
+
+func TestVector_Add(t *testing.T) {
+
+	for _, tt := range additionTests {
+		t.Run(tt.name, func(t *testing.T) {
+			v := Vector{
+				X: tt.vec.X,
+				Y: tt.vec.Y,
+			}
+			v.Add(tt.arg)
+			assert.Equal(t, tt.want, v, "Add did not produce expected result")
+		})
+	}
+}
+
+func TestVector_Added(t *testing.T) {
+	for _, tt := range additionTests {
+		t.Run(tt.name, func(t *testing.T) {
+			v := Vector{
+				X: tt.vec.X,
+				Y: tt.vec.Y,
+			}
+			assert.Equal(t, tt.want, v.Added(tt.arg), "Added didn't return expected value")
+		})
+	}
+}
+
+func TestVector_Negated(t *testing.T) {
+	tests := []struct {
+		name string
+		vec  Vector
+		want Vector
+	}{
+		{
+			name: "Simple check 1",
+			vec:  Vector{1, 1},
+			want: Vector{-1, -1},
+		},
+		{
+			name: "Simple check 2",
+			vec:  Vector{1, -1},
+			want: Vector{-1, 1},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			v := Vector{
+				X: tt.vec.X,
+				Y: tt.vec.Y,
+			}
+			if got := v.Negated(); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Vector.Negated() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestVector_Length(t *testing.T) {
+	tests := []struct {
+		name string
+		vec  Vector
+		want float64
+	}{
+		{
+			name: "Simple length 1",
+			vec:  Vector{1, 0},
+			want: 1,
+		}, {
+			name: "Simple length 2",
+			vec:  Vector{1, -1},
+			want: math.Sqrt(2),
+		}, {
+			name: "Simple length 3",
+			vec:  Vector{0, 0},
+			want: 0,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			v := Vector{
+				X: tt.vec.X,
+				Y: tt.vec.Y,
+			}
+			if got := v.Length(); got != tt.want {
+				t.Errorf("Vector.Length() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestVector_Distance(t *testing.T) {
+	tests := []struct {
+		name string
+		vec  Vector
+		arg  Vector
+		want float64
+	}{
+		{
+			name: "Simple distance 1",
+			vec:  Vector{0, 0},
+			arg:  Vector{1, 0},
+			want: 1,
+		},
+		{
+			name: "Simple distance 2",
+			vec:  Vector{1, 1},
+			arg:  Vector{-1, -1},
+			want: math.Sqrt(8),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			v := Vector{
+				X: tt.vec.X,
+				Y: tt.vec.Y,
+			}
+			if got := v.Distance(tt.arg); got != tt.want {
+				t.Errorf("Vector.Distance() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}