snake/snake.go

package main

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

// initSnake Initialize the snake
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 - 3,
				y: y,
			},
			{
				x: x - 2,
				y: y,
			},
			{
				x: x - 1,
				y: y,
			},
		},
		length:    3,
		direction: 1,
	}

	return snake
}

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

	var tail []rune

	// 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)

	for i, j := range snake.tail {
		// The Tail end
		if i == 0 {
			left := getDirection(j, snake.tail[i+1])
			right := getDirection(j, snake.tail[i+1])
			tail = append(tail, getLineType(left, right))

			// The Bit behind the head
		} else if i == len(snake.tail)-1 {
			left := getDirection(j, snake.tail[i-1])
			right := getDirection(j, snake.head)
			tail = append(tail, getLineType(left, right))

			// The body of the snake
		} else {
			left := getDirection(j, snake.tail[i-1])
			right := getDirection(j, snake.tail[i+1])
			tail = append(tail, getLineType(left, right))

		}

	}

	// Draw the body
	for i, segment := range snake.tail {
		screen.SetContent(segment.x, segment.y, tail[i], 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 {
		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 {
		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 {
		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 {
		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
}

func validateDirection(snake *Snake, direction int) bool {
	if snake.direction == direction {
		return true
	} else if snake.direction == Left && direction == Right {
		return false
	} else if snake.direction == Right && direction == Left {
		return false
	} else if snake.direction == Up && direction == Down {
		return false
	} else if snake.direction == Down && direction == Up {
		return false
	} else {
		return true
	}
}

func getDirection(from Position, to Position) int {

	var direction int

	if from.x-to.x == 1 {
		direction = Left
	} else if from.x-to.x == -1 {
		direction = Right
	} else if from.y-to.y == 1 {
		direction = Up
	} else if from.y-to.y == -1 {
		direction = Down
	}

	return direction
}

func getLineType(from int, to int) rune {

	var lineType rune

	if (from == Left && to == Down) || (from == Down && to == Left) {
		lineType = '┐'
	} else if (from == Up && to == Right) || (from == Right && to == Up) {
		lineType = '└'
	} else if (from == Left && to == Right) || (from == Right && to == Left) {
		lineType = '─'
	} else if (from == Left && to == Up) || (from == Up && to == Left) {
		lineType = '┘'
	} else if (from == Right && to == Down) || (from == Down && to == Right) {
		lineType = '┌'
	} else if (from == Up && to == Down) || (from == Down && to == Up) {
		lineType = '│'
	}

	return lineType
}