util.diamond.iterator.js

/**
 * A simple diamond pattern iterator which ends after one loop.
 *
 * Test case: [...load("util.diamond.iterator").loop({x:19,y:7},3)].map(i=>
 *               Game.rooms.W29N19.createConstructionSite(i.x,i.y,STRUCTURE_ROAD))
 */
class DiamondIterator {
    // public y;
    // public x;
    // private _radius;
    // private _dir
    // private _step;

    static loop(xy, radius) {
        const center = xy;
        const dist = radius;
        if (!_.isFinite(radius)) throw new Error("not finite: " + JSON.stringify([xy, radius]));
        return {
            [Symbol.iterator]: function() {
                return new DiamondIterator(center, dist);
            }
        };
    }

    static inside(pos, xy, radius) {
        return Math.abs(xy.x - pos.x) + Math.abs(xy.y - pos.y) < radius;
    }

    constructor(xy, radius) {
        if (!_.isFinite(radius)) throw new Error("not finite: " + JSON.stringify([xy, radius]));

        this._radius = radius;
        this.x = xy.x;
        this.y = xy.y;
        this._dir = TOP_RIGHT;
        this._stepA = radius - 0.25;
        this._stepB = 0.25;
    }

    next() {
        const a = this._stepA;
        const b = this._stepB;

        const result = {
            done: false,
            value: {},
        };

        switch(this._dir) {
            case TOP_RIGHT:
                result.value.x = Math.round(this.x - a); // (this._step - 0.25)); // A
                result.value.y = Math.round(this.y + b); // (this._step - this._radius + 0.25)); // B
                break;
            case BOTTOM_RIGHT:
                result.value.x = Math.round(this.x - b); // (this._step - this._radius + 0.25)); // B
                result.value.y = Math.round(this.y - a); // (this._step - 0.25)); // A
                break;
            case BOTTOM_LEFT:
                result.value.x = Math.round(this.x + a); // (this._step - 0.25)); // A
                result.value.y = Math.round(this.y - b); // (this._step - this._radius + 0.25)); // B
                break;
            case TOP_LEFT:
                result.value.x = Math.round(this.x + a); // (this._step - this._radius + 0.25); // B
                result.value.y = Math.round(this.y + b); // (this._step - 0.25)); // A
                break;
            default:
                return {
                    done: true,
                    value: false,
                }
        }

        this._stepA = a - 0.5;
        this._stepB = b + 0.5;

        if (this._stepA < 1) {
            this._dir = this._dir + 2;
            this._stepA = this._radius - 0.25;
            this._stepB = 0.25;
        }

        return result;
    }
}
module.exports = DiamondIterator;