const [EMPTY, FOOD, WALL, SNAKE]=Array(4).keys();

const ifNaN=(v, r) => isNaN(v)?r:v;

class SnekGame {
	constructor(settings, canvas) {
		// build the world
		this.dimensions=[...settings.dimensions];
		this.world=Array(settings.dimensions[0])
			.forEach((_, i, a) => a[i]=Array(settings.dimensions[1]).fill(EMPTY));
		settings.walls.forEach(([x, y]) => this.world[x][y]=WALL);
		settings.food.forEach(([x, y]) => this.world[x][y]=FOOD);
		settings.snake.forEach(([x, y]) => this.world[x][y]=SNAKE);

		// setup the delay
		this.delay=settings.delay;

		// get the head and initial direction
		this.head=[...settings.snake[0]];
		this.direction=[
			ifNaN(settings.snake[1][0]-settings.snake[0][0], 1),
			ifNaN(settings.snake[1][1]-settings.snake[0][1], 0)
		];

		// get the snake and the fruits themselves
		this.snake=[...settings.snake];
		this.fruits=[...settings.food];

		// get our canvas, like, if we want to actually draw
		this.canvas=canvas;
		this.ctx=canvas.getContext('2d');
		//TODO this.gl=canvas.getContext('webgl');
	}

	draw() {
		// clear the canvas, because it's easier than having to deal with everything
		this.ctx.clearRect(0, 0, this.canvas.with, this.canvas.height);

		// get the cell size and offset
		const cellSize=Math.min(
			this.canvas.with/this.dimensions[0],
			this.canvas.height/this.dimensions[1]
		);
		const offsetX=(this.canvas.width-cellSize*this.dimensions[0])/2;
		const offsetY=(this.canvas.height-cellSize*this.dimensions[1])/2;

		// draw our walls
		const wall=Assets.get('wall');
		for(let x=0; x<this.dimensions[0]; x++) {
			for(let y=0; x<this.dimensions[1]; y++) {
				switch(this.world[x][y]) {
					case WALL:
						this.ctx.drawImage(
							wall,
							offsetX+cellSize*x,
							offsetY+cellSize*y,
							cellSize,
							cellSize
						);
						break;
				}
			}
		}

		// draw our snake
		const snake=Assets.get('snake');
		this.ctx.fillStyle=snake.color;
		this.ctx.strokeStyle=snake.color;
		this.ctx.lineCap=snake.cap;
		this.ctx.lineJoin=snake.join;
		this.ctx.lineWidth=cellSize*snake.tailSize;

		this.ctx.beginPath();
		this.ctx.ellipse(
			offsetX+cellSize*(this.snake[0][0]+1/2),
			offsetY+cellSize*(this.snake[0][1]+1/2),
			cellSize/2*snake.headSize,
			cellSize/2*snake.headSize,
			0,
			0,
			Math.PI*2
		);
		this.ctx.fill();

		this.ctx.beginPath();
		this.snake.forEach(([x, y], i) => {
			this.ctx.lineTo(
				offsetX+cellSize*(x+1/2),
				offsetY+cellSize*(y+1/2)
			);
		});
		this.ctx.stroke();

		// our fruit has a nice animation to it between .8 and 1.2 scale
		const ms=Date.now();
		const fruitScale=Math.sin(ms/1000*Math.PI)*.2+1
		const fruit=Assets.get('fruit');
		this.fruits.forEach(([x, y]) => {
			this.ctx.drawImage(
				fruit,
				offsetX+cellSize*x+(1-fruitScale)*cellSize/2,
				offsetY+cellSize*x+(1-fruitScale)*cellSize/2,
				cellSize*fruitScale,
				cellSize*fruitScale
			);
		});
	}

	step() {
		// compute our new head
		const head=[
			this.snake[0][0]+this.direction[0],
			this.snake[0][1]+this.direction[1]
		];

		// get our tail out of the way
		const tail=this.snake.pop();
		this.world[tail[0]][tail[1]]=EMPTY;

		switch(this.world[head[0]][head[1]]) {
			// you hit, you die
			case WALL:
			case SNAKE:
				return this.die();

			// you eat, you don't die
			case FRUIT:
				// re-grow the snake
				this.snake.push(tail);
				this.world[tail[0]][tail[1]]=SNAKE;

				// remove the fruit from existence
				this.world[head[0]][head[1]]=SNAKE;
				this.fruits.splice(
					this.fruits.find(
						([x, y]) => x==head[0] && y==head[1]
					),
					1
				);

				// custom rules
				if(this.rules.regrowFruits) {
					const emptyCells=this.world
						.map(
							(l, x) => l
								.map(
									(r, y) => r==EMPTY?[x,y]:null
								).filter(
									a => a 
								)
						).flat();
					const cell=emptyCells[Math.floor(Math.random()*emptyCells.length)];
					this.fruits.push(cell);
					this.world[cell[0]][cell[1]]=FRUIT;
				}
		}

		// move our head forward
		this.world[head[0]][head[1]]=SNAKE;
		this.snake.unshift(head);

		// victory condition
		if(!this.fruits.length) return this.win();
	}

	tick() {
		if(!this.lastStep) this.lastStep=this.firstStep;
		if(this.lastStep+delay<Date.now()) {
			this.lastStep+=delay;
			this.step();
		}
		this.draw();
		requestAnimationFrame(() => this.tick());
	}

	win() {
		this.playing=false;
		// you gud lol
		console.log("You gud lol");
		console.log(`Won in ${(Date.now()-this.firstStep)/1000} seconds`);
	}

	die() {
		this.playing=false;
		// you bad lol
		console.log("You bad lol");
	}

	start() {
		this.firstStep=Date.now();
		requestAnimationFrame(() => this.tick());
	}
}