const { EventEmitter } = require('events');
const { stdin } = require('process');

class Game extends EventEmitter {
    constructor(width, height, sprites) {
        super();
        
        this.width = width;
        this.height = height;
        this.sprites = sprites;

        this.goals = 0;
        this.okGoals = 0;

        this.on('levelEnd', this.nextLevel);
        this.on('move', this.onMove);
    };

    resetLines() {
        this.lines = [];

        for(let y = 0; y < this.height; y ++) {
            const line = new Array(this.width).fill('air');
            this.lines.push(line);
        };
    };

    nextLevel() {
        this.okGoals = 0;
        this.resetLines();
        this.addBorderWalls();

        const walls = 1 + Math.random() * 2;
        for(let i = 0; i < walls; i ++)
            this.spawn('wall');

        const boxes = 1 + Math.floor(Math.random() * 2);
        this.goals = boxes;

        for(let i = 0; i < boxes; i ++) {
            this.spawn('box', 2);
            this.spawn('goal');
        };

        this.spawn('player');
        this.update();
    };

    getPlayerPos() {
        const y = this.lines.findIndex((line) => line.includes('player'));
        const line = this.lines[y];

        if(!line) {
            this.spawn('player');
            return this.getPlayerPos();
        };

        const x = line.indexOf('player');

        return { x, y };
    };

    setItemPos(x, y, newX, newY) {
        const char = this.lines[y][x];

        this.lines[y][x] = 'air';
        this.lines[newY][newX] = char;
    };

    moveItem(x, y, side) {
        const sides = {
            left: [ 'x', -1 ],
            up: [ 'y', -1 ],
            down: [ 'y', 1 ],
            right: [ 'x', 1 ]
        };

        const [ coord, apply ] = sides[side];
        const newPos = { x, y };

        newPos[coord] += apply;

        const collide = this.lines[newPos.y][newPos.x];
        const char = this.lines[y][x];

        if(collide === 'box') {
            const ok = this.moveItem(newPos.x, newPos.y, side);

            if(!ok) return;
        } else {
            if(char === 'box' && collide === 'goal') {
                this.okGoals ++;

                if(this.okGoals >= this.goals)
                    this.emit('levelEnd');

                this.lines[newPos.y][newPos.x] = 'air';

                return true;
            };

            if(collide !== 'air') return;
        };

        this.setItemPos(x, y, newPos.x, newPos.y);

        return true;
    };

    onMove(side) {
        const pos = this.getPlayerPos();

        this.moveItem(pos.x, pos.y, side);
        this.update();
    };

    spawn(item, offset = 1) {
        const randomPos = (max) => Math.floor(offset + Math.random() * (max - offset * 2));

        const x = randomPos(this.width);
        const y = randomPos(this.height);

        if(this.lines[y][x] === 'air') {
            this.lines[y][x] = item;
        } else {
            this.spawn(item, offset);
        };
    };

    addBorderWalls() {
        for(let x = 0; x < this.width; x ++) {
            this.lines[0][x] = 'wall';
            this.lines[this.height - 1][x] = 'wall';
        };
        
        for(let y = 0; y < this.height; y ++) {
            this.lines[y][0] = 'wall';
            this.lines[y][this.width - 1] = 'wall';
        };
    };

    update() {
        const frame = this.lines
            .map((line) => line.map((char) => this.sprites[char]).join(''))
            .join('\n');

        this.emit('update', frame);
    };
};

const game = new Game(16, 7, {
    player: '@',
    air: ' ',
    wall: '#',
    box: '%',
    goal: '$'
});

game.on('update', (state) => {
    console.clear();
    console.log(state);
});

game.nextLevel();

stdin.setRawMode(true);
stdin.setEncoding('utf-8')
stdin.resume();

const sides = {
    a: 'left',
    w: 'up',
    s: 'down',
    d: 'right'
};

stdin.on('data', (key) => {
    if(key === '\u0003') process.exit();

    const side = sides[key];

    if(side) game.emit('move', side);
});