Never spawn food within one move of any snake.

go.sum

@@ -2,6 +2,7 @@ github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=

standard.go

@@ -157,7 +157,7 @@ func (r *StandardRuleset) placeFoodFixed(b *BoardState) error {
 	// Finally, always place 1 food in center of board for dramatic purposes
 	isCenterOccupied := true
 	centerCoord := Point{(b.Width - 1) / 2, (b.Height - 1) / 2}
-	unoccupiedPoints := r.getUnoccupiedPoints(b)
+	unoccupiedPoints := r.getUnoccupiedPoints(b, true)
 	for _, point := range unoccupiedPoints {
 		if point == centerCoord {
 			isCenterOccupied = false
@@ -526,7 +526,7 @@ func (r *StandardRuleset) maybeSpawnFood(b *BoardState) error {
 
 func (r *StandardRuleset) spawnFood(b *BoardState, n int) error {
 	for i := 0; i < n; i++ {
-		unoccupiedPoints := r.getUnoccupiedPoints(b)
+		unoccupiedPoints := r.getUnoccupiedPoints(b, false)
 		if len(unoccupiedPoints) > 0 {
 			newFood := unoccupiedPoints[rand.Intn(len(unoccupiedPoints))]
 			b.Food = append(b.Food, newFood)
@@ -535,7 +535,7 @@ func (r *StandardRuleset) spawnFood(b *BoardState, n int) error {
 	return nil
 }
 
-func (r *StandardRuleset) getUnoccupiedPoints(b *BoardState) []Point {
+func (r *StandardRuleset) getUnoccupiedPoints(b *BoardState, includePossibleMoves bool) []Point {
 	pointIsOccupied := map[int32]map[int32]bool{}
 	for _, p := range b.Food {
 		if _, xExists := pointIsOccupied[p.X]; !xExists {
@@ -544,11 +544,26 @@ func (r *StandardRuleset) getUnoccupiedPoints(b *BoardState) []Point {
 		pointIsOccupied[p.X][p.Y] = true
 	}
 	for _, snake := range b.Snakes {
-		for _, p := range snake.Body {
+		for i, p := range snake.Body {
 			if _, xExists := pointIsOccupied[p.X]; !xExists {
 				pointIsOccupied[p.X] = map[int32]bool{}
 			}
 			pointIsOccupied[p.X][p.Y] = true
+
+			if i == 0 && !includePossibleMoves {
+				nextMovePoints := []Point{
+					{X: p.X - 1, Y: p.Y},
+					{X: p.X + 1, Y: p.Y},
+					{X: p.X, Y: p.Y - 1},
+					{X: p.X, Y: p.Y + 1},
+				}
+				for _, nextP := range nextMovePoints {
+					if _, xExists := pointIsOccupied[nextP.X]; !xExists {
+						pointIsOccupied[nextP.X] = map[int32]bool{}
+					}
+					pointIsOccupied[nextP.X][nextP.Y] = true
+				}
+			}
 		}
 	}
 
@@ -570,7 +585,7 @@ func (r *StandardRuleset) getUnoccupiedPoints(b *BoardState) []Point {
 
 func (r *StandardRuleset) getEvenUnoccupiedPoints(b *BoardState) []Point {
 	// Start by getting unoccupied points
-	unoccupiedPoints := r.getUnoccupiedPoints(b)
+	unoccupiedPoints := r.getUnoccupiedPoints(b, true)
 
 	// Create a new array to hold points that are  even
 	evenUnoccupiedPoints := []Point{}

standard_test.go

@@ -44,17 +44,18 @@ func TestCreateInitialBoardState(t *testing.T) {
 		Err             error
 	}{
 		{1, 1, []string{"one"}, 0, nil},
-		{1, 2, []string{"one"}, 1, nil},
+		{1, 2, []string{"one"}, 0, nil},
+		{1, 4, []string{"one"}, 1, nil},
+		{2, 2, []string{"one"}, 1, nil},
 		{9, 8, []string{"one"}, 1, nil},
-		{2, 2, []string{"one", "two"}, 2, nil},
+		{2, 2, []string{"one", "two"}, 0, nil},
-		{2, 2, []string{"one", "two"}, 2, nil},
 		{1, 1, []string{"one", "two"}, 2, errors.New("not enough space to place snake")},
 		{1, 2, []string{"one", "two"}, 2, errors.New("not enough space to place snake")},
 		{BoardSizeSmall, BoardSizeSmall, []string{"one", "two"}, 3, nil},
 	}
 
 	r := StandardRuleset{}
-	for _, test := range tests {
+	for testNum, test := range tests {
 		state, err := r.CreateInitialBoardState(test.Width, test.Height, test.IDs)
 		require.Equal(t, test.Err, err)
 		if err != nil {
@@ -68,7 +69,7 @@ func TestCreateInitialBoardState(t *testing.T) {
 		for i, id := range test.IDs {
 			require.Equal(t, id, state.Snakes[i].ID)
 		}
-		require.Len(t, state.Food, test.ExpectedNumFood)
+		require.Len(t, state.Food, test.ExpectedNumFood, testNum)
 	}
 }
 
@@ -212,7 +213,7 @@ func TestPlaceSnakes(t *testing.T) {
 
 	r := StandardRuleset{}
 	for _, test := range tests {
-		require.Equal(t, test.BoardState.Width*test.BoardState.Height, int32(len(r.getUnoccupiedPoints(test.BoardState))))
+		require.Equal(t, test.BoardState.Width*test.BoardState.Height, int32(len(r.getUnoccupiedPoints(test.BoardState, true))))
 		err := r.placeSnakes(test.BoardState)
 		require.Equal(t, test.Err, err, "Snakes: %d", len(test.BoardState.Snakes))
 		if err == nil {
@@ -1732,7 +1733,7 @@ func TestGetUnoccupiedPoints(t *testing.T) {
 
 	r := StandardRuleset{}
 	for _, test := range tests {
-		unoccupiedPoints := r.getUnoccupiedPoints(test.Board)
+		unoccupiedPoints := r.getUnoccupiedPoints(test.Board, true)
 		require.Equal(t, len(test.Expected), len(unoccupiedPoints))
 		for i, e := range test.Expected {
 			require.Equal(t, e, unoccupiedPoints[i])
@@ -1834,12 +1835,12 @@ func TestMaybeSpawnFood(t *testing.T) {
 		ExpectedFood []Point
 	}{
 		// Use pre-tested seeds and results
-		{123, []Point{}, []Point{{2, 2}}},
+		{123, []Point{}, []Point{{2, 3}}},
 		{456, []Point{{4, 4}}, []Point{{4, 4}}},
 		{789, []Point{{4, 4}}, []Point{{4, 4}}},
-		{1024, []Point{}, []Point{{4, 1}}},
+		{1024, []Point{}, []Point{{1, 2}}},
-		{511, []Point{{4, 4}}, []Point{{4, 4}, {2, 0}}},
+		{511, []Point{{4, 4}}, []Point{{4, 4}, {4, 1}}},
-		{165, []Point{{4, 4}}, []Point{{4, 4}, {3, 1}}},
+		{165, []Point{{4, 4}}, []Point{{4, 4}, {4, 2}}},
 	}
 
 	r := StandardRuleset{}
@@ -1864,6 +1865,21 @@ func TestMaybeSpawnFood(t *testing.T) {
 	}
 }
 
+func TestSpawnFood(t *testing.T) {
+	b := &BoardState{
+		Height: 1,
+		Width:  3,
+		Snakes: []Snake{
+			{Body: []Point{{1, 0}}},
+		},
+	}
+	// Food should never spawn, no room
+	r := StandardRuleset{}
+	err := r.spawnFood(b, 99)
+	require.NoError(t, err)
+	require.Equal(t, len(b.Food), 0)
+}
+
 func TestIsGameOver(t *testing.T) {
 	tests := []struct {
 		Snakes   []Snake