mechanics.go

package main

import (
	"math/rand"

	"github.com/golang-cz/snake/proto"
)

func (s *Server) createSnake(username string) (uint64, error) {
	s.lastSnakeId++

	randOffset := uint(rand.Intn(10) - rand.Intn(10))

	snakeId := s.lastSnakeId
	s.state.Snakes[snakeId] = &proto.Snake{
		Id:    snakeId,
		Name:  username,
		Color: randColor(),
		Body: []*proto.Square{
			{X: 36, Y: 35 + randOffset},
			{X: 35, Y: 35 + randOffset},
			{X: 34, Y: 35 + randOffset},
		},
		Direction: &right,
	}

	return snakeId, nil
}

func turnSnake(snake *proto.Snake, direction *proto.Direction, buf int) error {
	lastDirection := *snake.Direction
	if len(snake.NextDirections) > 0 {
		lastDirection = *snake.NextDirections[len(snake.NextDirections)-1]
	}

	// Same direction.
	if lastDirection == *direction {
		return proto.ErrTurnSameDirection
	}

	// Disallow turnabouts.
	switch {
	case lastDirection == proto.Direction_up && *direction == proto.Direction_down:
		return proto.ErrTurnAbout
	case lastDirection == proto.Direction_down && *direction == proto.Direction_up:
		return proto.ErrTurnAbout
	case lastDirection == proto.Direction_left && *direction == proto.Direction_right:
		return proto.ErrTurnAbout
	case lastDirection == proto.Direction_right && *direction == proto.Direction_left:
		return proto.ErrTurnAbout
	}

	if len(snake.NextDirections) > buf {
		snake.NextDirections = append(snake.NextDirections[:buf], direction)
	} else {
		snake.NextDirections = append(snake.NextDirections, direction)
	}

	return nil
}