refactor: extract grid abstraction for reuse

internal/move/move.go

@@ -0,0 +1,36 @@
+// Package move provides types and functions to represent and manipulate moves on a 2D grid.
+package move
+
+type Move interface {
+	NumberOfRows() int
+	NumberOfColumns() int
+}
+
+type move struct {
+	numberOfRows    int
+	numberOfColumns int
+}
+
+func (m move) NumberOfRows() int {
+	return m.numberOfRows
+}
+
+func (m move) NumberOfColumns() int {
+	return m.numberOfColumns
+}
+
+var (
+	Up       = move{numberOfRows: -1, numberOfColumns: 0}
+	Down     = move{numberOfRows: 1, numberOfColumns: 0}
+	Right    = move{numberOfRows: 0, numberOfColumns: 1}
+	Left     = move{numberOfRows: 0, numberOfColumns: -1}
+	cardinal = []Move{Up, Down, Right, Left}
+
+	UpRight   = move{numberOfRows: -1, numberOfColumns: 1}
+	UpLeft    = move{numberOfRows: -1, numberOfColumns: -1}
+	DownRight = move{numberOfRows: 1, numberOfColumns: 1}
+	DownLeft  = move{numberOfRows: 1, numberOfColumns: -1}
+	ordinal   = []Move{UpRight, UpLeft, DownRight, DownLeft}
+
+	AllDirections = append(cardinal, ordinal...)
+)

internal/move/move_test.go

@@ -0,0 +1,91 @@
+package move_test
+
+import (
+	"testing"
+
+	"github.com/StevanFreeborn/advent-of-code-2025/internal/move"
+)
+
+func TestNumberOfRows(t *testing.T) {
+	tests := []struct {
+		move     move.Move
+		expected int
+	}{
+		{move.Up, -1},
+		{move.Down, 1},
+		{move.Right, 0},
+		{move.Left, 0},
+		{move.UpRight, -1},
+		{move.UpLeft, -1},
+		{move.DownRight, 1},
+		{move.DownLeft, 1},
+	}
+
+	for _, test := range tests {
+		if test.move.NumberOfRows() != test.expected {
+			t.Errorf("expected number of rows for move to be %d, got %d", test.expected, test.move.NumberOfRows())
+		}
+	}
+}
+
+func TestNumberOfColumns(t *testing.T) {
+	tests := []struct {
+		move     move.Move
+		expected int
+	}{
+		{move.Up, 0},
+		{move.Down, 0},
+		{move.Right, 1},
+		{move.Left, -1},
+		{move.UpRight, 1},
+		{move.UpLeft, -1},
+		{move.DownRight, 1},
+		{move.DownLeft, -1},
+	}
+
+	for _, test := range tests {
+		if test.move.NumberOfColumns() != test.expected {
+			t.Errorf("expected number of columns for move to be %d, got %d", test.expected, test.move.NumberOfColumns())
+		}
+	}
+}
+
+func TestAllDirectionsLength(t *testing.T) {
+	expectedLength := 8
+
+	if len(move.AllDirections) != expectedLength {
+		t.Errorf("expected AllDirections length to be %d, got %d", expectedLength, len(move.AllDirections))
+	}
+}
+
+func TestDefinedMoves(t *testing.T) {
+	definedMoves := []struct {
+		name            string
+		move            move.Move
+		expectedRows    int
+		expectedColumns int
+	}{
+		{"Up", move.Up, -1, 0},
+		{"Down", move.Down, 1, 0},
+		{"Right", move.Right, 0, 1},
+		{"Left", move.Left, 0, -1},
+		{"UpRight", move.UpRight, -1, 1},
+		{"UpLeft", move.UpLeft, -1, -1},
+		{"DownRight", move.DownRight, 1, 1},
+		{"DownLeft", move.DownLeft, 1, -1},
+	}
+
+	for _, dm := range definedMoves {
+		if dm.move == nil {
+			t.Errorf("expected move %s to be defined, got nil", dm.name)
+		}
+
+		if dm.move.NumberOfRows() != dm.expectedRows {
+			t.Errorf("expected move %s to have %d rows, got %d", dm.name, dm.expectedRows, dm.move.NumberOfRows())
+		}
+
+		if dm.move.NumberOfColumns() != dm.expectedColumns {
+			t.Errorf("expected move %s to have %d columns, got %d", dm.name, dm.expectedColumns, dm.move.NumberOfColumns())
+		}
+	}
+}