from src.core import Snake, Direction

def test_snake_initialization():
    """Test snake initialization with default values"""
    snake = Snake((100, 100), 20)
    assert snake.block_size == 20
    assert snake.direction == Direction.RIGHT
    assert len(snake.body) == 1
    assert snake.body[0] == (100, 100)
    assert not snake.growing

def test_snake_movement():
    """Test snake movement in different directions"""
    snake = Snake((100, 100), 20)
    
    # Test right movement (default direction)
    snake.move(100)  # time parameter
    assert snake.body[0] == (120, 100)
    
    # Test down movement
    snake.change_direction(Direction.DOWN)
    snake.move(200)
    assert snake.body[0] == (120, 120)
    
    # Test left movement
    snake.change_direction(Direction.LEFT)
    snake.move(300)
    assert snake.body[0] == (100, 120)
    
    # Test up movement
    snake.change_direction(Direction.UP)
    snake.move(400)
    assert snake.body[0] == (100, 100)

def test_snake_growth():
    """Test snake growth when eating food"""
    snake = Snake((100, 100), 20)
    original_length = len(snake.body)
    
    snake.grow()
    snake.move(100)
    
    assert len(snake.body) == original_length + 1

def test_snake_collision():
    """Test snake collision detection"""
    snake = Snake((100, 100), 20)
    
    # Test wall collision
    assert snake.check_collision(200, 200) == False  # No collision
    snake.body[0] = (-20, 100)  # Move outside left wall
    assert snake.check_collision(200, 200) == True
    
    # Test self collision
    snake = Snake((100, 100), 20)
    snake.body = [(100, 100), (120, 100), (120, 120), (100, 120), (100, 100)]
    assert snake.check_collision(200, 200) == True

def test_invalid_direction_change():
    """Test that snake cannot reverse direction"""
    snake = Snake((100, 100), 20)
    
    # Try to change to opposite direction (LEFT while going RIGHT)
    snake.change_direction(Direction.LEFT)
    assert snake.direction == Direction.RIGHT
    
    # Valid direction change
    snake.change_direction(Direction.DOWN)
    assert snake.direction == Direction.DOWN
    
    # Try to change to opposite direction (UP while going DOWN)
    snake.change_direction(Direction.UP)
    assert snake.direction == Direction.DOWN