pacman.js/MovingObject.js

class MovingObject extends GameObject {
    constructor(game, x, y) {
        super(game, x, y);
        this.dir = {x: 0, y: 0};
        this.speed = 1;

        this.turnTimeout = null;
    }

    changeDir(dir) {
        if (this.dir.x === dir.x && this.dir.y === dir.y) {
            return;
        }

        if (this.dir.x === dir.x || this.dir.y === dir.y) {
            clearTimeout(this.turnTimeout);
            this.dir = dir;
            return;
        }

        const isX = this.dir.x !== 0;
        let curPos;
        let dirPositive;

        if (isX) {
            curPos = this.x;
            dirPositive = this.dir.x > 0;
        } else if (this.dir.y !== 0) {
            curPos = this.y;
            dirPositive = this.dir.y > 0;
        }

        let targetSwitch;
        if (dirPositive) {
            targetSwitch = Math.ceil(curPos + 0.5) - 0.5;
        } else {
            targetSwitch = Math.floor(curPos - 0.5) + 0.5;
        }

        const distance = Math.abs(curPos - targetSwitch);
        const duration = distance / this.speed * 1000;

        clearTimeout(this.turnTimeout);
        this.turnTimeout = setTimeout(() => {
            if (isX) {
                this.x = targetSwitch;
            } else {
                this.y = targetSwitch;
            }
            this.dir = dir;
        }, duration);
    }

    update(deltaTime) {
        const ticks = Math.floor(deltaTime / 16);
        const tickLength = deltaTime / ticks;

        for(let i = 0; i < ticks; i++) {
            this.x += this.dir.x * (this.speed * tickLength / 1000);
            this.y += this.dir.y * (this.speed * tickLength / 1000);

            const nextTile = this.getNextTile(this.dir.x, this.dir.y);

            if (!nextTile.tile) {
                if (nextTile.distanceX <= 0.5 || nextTile.distanceY <= 0.5) {

                    return;
                }
            }

            if (nextTile.tile.solid) {
                if (nextTile.distanceX <= 0.5) {
                    this.x = nextTile.tile.x - this.dir.x + 0.5;
                }
                if (nextTile.distanceY <= 0.5) {
                    this.y = nextTile.tile.y - this.dir.y + 0.5;
                }
            }
        }
    }

    getNextTile(offsetX, offsetY) {
        const tileX = Math.round(this.x - 0.5);
        const tileY = Math.round(this.y - 0.5);

        const nextX = tileX + offsetX;
        const nextY = tileY + offsetY;

        const distanceX = Math.abs(this.x - (offsetX >= 0 ? nextX : nextX + 1));
        const distanceY = Math.abs(this.y - (offsetY >= 0 ? nextY : nextY + 1));

        return {
            tile: this.game.map.getTile(nextX, nextY),
            distanceX: distanceX,
            distanceY: distanceY,
        };
    }
}