snake.js

import {getInputDirection} from "./input.js"

export const SNAKE_SPEED = 7;

const snakeBody = [
    { x: 11, y: 11}
];
let newSegments = 0;

export function update()
{
    addSegments();
    const inputDirection = getInputDirection();
    for (let i = snakeBody.length - 2; i >= 0; i--) {
        snakeBody[i + 1] = {...snakeBody[i]}
    }
    snakeBody[0].x += inputDirection.x;
    snakeBody[0].y += inputDirection.y;
}

export function draw(gameBoard)
{
    console.log("draw the snake");
    snakeBody.forEach(segment => {
        const snakeElement = document.createElement('div')
        snakeElement.style.gridRowStart = segment.y;
        snakeElement.style.gridColumnStart = segment.x;
        snakeElement.classList.add("snake");
        gameBoard.appendChild(snakeElement);
    })
}

export function expandSnake(amount)
{
    newSegments = newSegments + amount;
}

export function onSnake(position, {ignoreHead = false} = {})
{
    return snakeBody.some((segment, index) => {
        if (ignoreHead && index === 0) return false;
        return equalPositions(segment, position);
    })
}

export function getSnakeHead()
{
    return snakeBody[0];
}

export function snakeIntersection()
{
    return onSnake(snakeBody[0], {ignoreHead: true})
}

function equalPositions(segment, position)
{
    return (segment.x === position.x && segment.y === position.y);
}

function addSegments()
{
    for (let i = 0; i < newSegments; i++) {
        snakeBody.push({...snakeBody[snakeBody.length - 1]})
    }
    newSegments = 0;
}