Move bearing into maths

pkg/maths/bearing.go

@@ -0,0 +1,82 @@
+package maths
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Bearing describes a compass direction
+type Bearing int
+
+const (
+	// North describes a 0,1 vector
+	North Bearing = iota
+	// NorthEast describes a 1,1 vector
+	NorthEast
+	// East describes a 1,0 vector
+	East
+	// SouthEast describes a 1,-1 vector
+	SouthEast
+	// South describes a 0,-1 vector
+	South
+	// SouthWest describes a -1,-1 vector
+	SouthWest
+	// West describes a -1,0 vector
+	West
+	// NorthWest describes a -1,1 vector
+	NorthWest
+)
+
+// bearingString simply describes the strings associated with a direction
+type bearingString struct {
+	Long  string
+	Short string
+}
+
+// bearingStrings is the set of strings for each direction
+var bearingStrings = []bearingString{
+	{"North", "N"},
+	{"NorthEast", "NE"},
+	{"East", "E"},
+	{"SouthEast", "SE"},
+	{"South", "S"},
+	{"SouthWest", "SW"},
+	{"West", "W"},
+	{"NorthWest", "NW"},
+}
+
+// String converts a Direction to a String
+func (d Bearing) String() string {
+	return bearingStrings[d].Long
+}
+
+// ShortString converts a Direction to a short string version
+func (d Bearing) ShortString() string {
+	return bearingStrings[d].Short
+}
+
+// FromString gets the Direction from a string
+func FromString(s string) (Bearing, error) {
+	for i, d := range bearingStrings {
+		if strings.EqualFold(d.Long, s) || strings.EqualFold(d.Short, s) {
+			return Bearing(i), nil
+		}
+	}
+	return -1, fmt.Errorf("unknown bearing: %s", s)
+}
+
+var bearingVectors = []Vector{
+	{X: 0, Y: 1},  // N
+	{X: 1, Y: 1},  // NE
+	{X: 1, Y: 0},  // E
+	{X: 1, Y: -1}, // SE
+	{X: 0, Y: -1}, // S
+	{X: -1, Y: 1}, // SW
+	{X: -1, Y: 0}, // W
+	{X: -1, Y: 1}, // NW
+}
+
+// Vector converts a Direction to a Vector
+func (d Bearing) Vector() Vector {
+	return bearingVectors[d]
+}