snake/snake.go

package main

import (
	"github.com/gdamore/tcell/v2"
)

func initSnake(snakex *int, snakey *int) Snake {
	var x, y int = *snakex, *snakey
	snake := Snake{
		head: Position{
			x: x,
			y: y,
		},
		tail: []Position{
			{
				x: x - 1,
				y: y,
			},
			{
				x: x - 2,
				y: y,
			},
			{
				x: x - 3,
				y: y,
			},
		},
		length:    3,
		direction: 1,
	}

	return snake
}

func drawSnake(screen tcell.Screen, style tcell.Style, snake *Snake) {

	// Reverse tail, chop of the excesses,
	snake.tail = ReverseSlice(snake.tail)
	if len(snake.tail) > snake.length {
		snake.tail = snake.tail[:snake.length]
	}
	// reverse it back to the original order, replace the tail in `snake`
	snake.tail = ReverseSlice(snake.tail)

	// Draw the body
	for _, segment := range snake.tail {
		screen.SetContent(segment.x, segment.y, '+', nil, style)
	}

	// Draw the head, make sure it is on top of everything
	screen.SetContent(snake.head.x, snake.head.y, '0', nil, style)

}

func snakeDirection(press int, snake *Snake) {
	if press == Left {
		if snake.direction != Right {
			snake.head.x--
			snake.tail = append(snake.tail, Position{x: snake.head.x + 1, y: snake.head.y})
			snake.direction = press
		}
	} else if press == Right {
		if snake.direction != Left {
			snake.head.x++
			snake.tail = append(snake.tail, Position{x: snake.head.x - 1, y: snake.head.y})
			snake.direction = press
		}
	} else if press == Up {
		if snake.direction != Down {
			snake.head.y--
			snake.tail = append(snake.tail, Position{x: snake.head.x, y: snake.head.y + 1})
			snake.direction = press
		}
	} else if press == Down {
		if snake.direction != Up {
			snake.head.y++
			snake.tail = append(snake.tail, Position{x: snake.head.x, y: snake.head.y - 1})
			snake.direction = press
		}
	}
}

// Check if a pos hits the tail
func hitsTail(snake *Snake, x int, y int) bool {
	var hit bool = false

	for _, segment := range snake.tail {
		if segment.x == x && segment.y == y {
			hit = true
		}
	}

	return hit
}

func ReverseSlice[T comparable](s []T) []T {
	var r []T
	for i := len(s) - 1; i >= 0; i-- {
		r = append(r, s[i])
	}
	return r
}