Snake/sources/js/Game.js

import {Tile, tiles} from "./Tile.js"
import {Snake, directions} from "./Snake.js";


export class Game {
    /**
     * Generate a new game of Snake
     * @param {HTMLCanvasElement} canvas
     */
    constructor(canvas) {
        if (canvas && canvas.nodeName === "CANVAS")
            this.ctx = canvas.getContext("2d");
        else
            throw new InvalidGameOption("canvas");

        this.size = [15, 15];
        this.direction = directions.RIGHT;
        this.snakeSpeed = 500;
        this.lives = 3;

        this.world = [];
        this.score = 0;
        this.onStart = null;
        this.onStop = null;
        this.onEat = null;
        this.onDie = null;
        this.onGameOver = null;
    }

    /**
     * Init the world with empty tiles
     */
    initWorld() {
        for (let x = 0; x < this.size[0]; x++)
            for (let y = 0; y < this.size[1]; y++) {
                if (!this.world[x])
                    this.world[x] = [];
                this.world[x][y] = new Tile(x, y, tiles.EMPTY, this);
            }
    }

    /**
     * Init the canvas
     */
    initCanvas() {
        this.ctx.canvas.ownerDocument.addEventListener("keydown", ev => {
            switch (ev.key) {
                case "ArrowUp":
                    if (this.lastDirection !== directions.DOWN)
                        this.direction = directions.UP;
                    break;
                case "ArrowRight":
                    if (this.lastDirection !== directions.LEFT)
                        this.direction = directions.RIGHT;
                    break;
                case "ArrowDown":
                    if (this.lastDirection !== directions.UP)
                        this.direction = directions.DOWN;
                    break;
                case "ArrowLeft":
                    if (this.lastDirection !== directions.RIGHT)
                        this.direction = directions.LEFT;
                    break;
            }
        });
    }

    /**
     * Draw the grid
     */
    drawGrid() {
        for (const l of this.world)
            for (const t of l)
                t.draw()
    }

    /**
     * Start the party
     */
    start() {
        if (this.onStart && typeof this.onStart === "function")
            this.onStart();

        this.direction = this.lastDirection = this.startDirection;
        this.snake = new Snake({startPos: this.size.map(s => Math.floor(s/2))});

        this.initWorld();
        this.updateSnake();
        this.drawGrid();
        this.initCanvas();
        this.appleGenerator();

        this.mainInterval = setInterval(() => this.main(), this.snakeSpeed);
    }

    /**
     * Stop the party
     */
    stop() {
        clearInterval(this.mainInterval);

        // Clear the grid
        this.ctx.globalCompositeOperation = "destination-out";
        this.ctx.fillRect(0, 0, this.ctx.canvas.width, this.ctx.canvas.height);
        this.ctx.globalCompositeOperation = "source-over";
        if (this.onStop && typeof this.onStop === "function")
            this.onStop();
    }

    /**
     * Restart the party
     */
    restart() {
        this.stop();
        this.start();
    }

    /**
     * The main loop pf the game
     */
    main() {
        try {
            this.moveSnake();
            this.drawGrid();
        } catch (err) {
            if (err instanceof GameOver) {
                this.lives--;
                if (this.lives <= 0) {
                    if (this.onGameOver && typeof this.onGameOver === "function")
                        this.onGameOver(this.score);
                    this.stop();
                    this.score = 0;
                } else {
                    if (this.onDie && typeof this.onDie === "function")
                        this.onDie(this.lives);
                    this.restart();
                }
            } else {
                console.error(err);
                alert("An error occurred !");
            }
        }
    }

    /**
     * Update the snake on the world and check for collision
     */
    updateSnake() {
        for (const [x, y] of this.snake.body)
            if (!(x in this.world) || !(y in this.world[x]))
                throw new GameOver();
            else {
                const t = this.world[x][y];
                if (t.type === tiles.APPLE) {
                    this.snake.eat();
                    this.appleGenerator();
                    this.score++;
                    if (this.onEat && typeof this.onEat === "function")
                        this.onEat(this.score);
                }
                t.type = tiles.SNAKE;
            }
    }

    /**
     * Move the snake
     */
    moveSnake() {
        this.snake.move(this.direction);
        this.lastDirection = this.direction;

        for (const l of this.world)
            for (const t of l)
                if (t.type === tiles.SNAKE)
                    t.type = tiles.EMPTY;

        this.updateSnake();
    }

    /**
     * Main loop fir apple generation
     */
    appleGenerator() {
        let pos = this.randCoords();

        this.world[pos[0]][pos[1]].type = tiles.APPLE;
    }

    /**
     * Generate random coordinates of empty tiles
     * @returns {[int, int]}
     */
    randCoords() {
        let pos;

        do {
            pos = [];

            for (const s of this.size)
                pos.push(Math.floor(Math.random() * s))
        } while (this.world[pos[0]][pos[1]].type !== tiles.EMPTY);

        return pos;
    }

    /**
     * Generate a new game of Snake
     * @param {[int, int]} size
     * @param {directions} direction
     * @param {int} snakeSpeed
     * @param {int} appleSpeed
     * @param {int} lives
     */
    load({size = [15, 15], direction = directions.RIGHT, snakeSpeed = 500, lives = 3} = {}) {
        if (size && Array.isArray(size) && size.length === 2 && size.filter(s => typeof s === "number" && s > 0 && s % 1 === 0).length === size.length)
            this.size = size;
        else
            throw new InvalidGameOption("size");

        if (direction && Object.values(directions).find(([x,y]) => direction[0] === x && direction[1] === y))
            this.direction = this.startDirection = this.lastDirection = direction;
        else
            throw new InvalidGameOption("direction");

        if (snakeSpeed && typeof snakeSpeed === "number" && snakeSpeed > 0 && snakeSpeed % 1 === 0)
            this.snakeSpeed = snakeSpeed;
        else
            throw new InvalidGameOption("snakeSpeed");

        if (lives && typeof lives === "number" && lives > 0 && lives % 1 === 0)
            this.lives = lives;
        else
            throw new InvalidGameOption("lives");
    }
}

export class InvalidGameOption extends Error {
    /**
     * @param {string} name
     */
    constructor(name) {
        super(`Invalid Game option: ${name}`);
    }
}

export class GameOver extends Error {
    constructor() {
        super("Game Over");
    }
}