dust/js/particle.js

import Rx, { Observable } from 'rxjs';
import { RAD } from './enums';
import Store from './store';

const random = {
    bool: (weight) => Math.random() < (weight || 0.5),
    color: () => `rgb(${Math.floor(Math.random() * 255)}, ${Math.floor(Math.random() * 255)}, ${Math.floor(Math.random() * 255)})`,
    num: (min, max) => min + Math.round(Math.random() * max),
}

// ===== Constructor =====

function Particle(parent, bounds, config, globalGrid) {
    this.config = Object.assign({
        bounds,
        color: random.color(),
        gridSize: 5,
        randomize: true,
        showMovementCircle: false,
        showVisionGrid: false,
        speed: 4,
        visionRadius: 50
    }, config);

    this.grids = {
        global: globalGrid || {},
        vision: createVisionGrid(this.config)
    };

    this.arc = createArc(bounds, this.grids, this.config); // TODO no need to pass config after testing

    this.nodes = {
        body: createBodyNode(this.config),
        circle: undefined,
        container: createContainerNode(this.config),
        parent,
        visionGrid: undefined,
    };

    this.nodes.container.appendChild(this.nodes.body);
    parent.appendChild(this.nodes.container);

    this.updateConfig(this.config);
    this.nextFrame();
};

// ===== PROTOTYPE =====

Particle.prototype.remove = function() {
    this.nodes.parent.removeChild(this.nodes.container);
    return this;
}

Particle.prototype.nextFrame = function() {
    this.arc = stepArc(this.arc, this.config);
    this.grids.vision = updateVisionGrid(this.arc, this.config, this.grids);

    this.arc = evade(this.arc, this.grids.vision);

    repaintContainer(this.nodes.container, this.arc);
    repaintBody(this.nodes.body, this.arc);
    repaintCircle(this.nodes.circle, this.arc);
    repaintVisionGrid(this.nodes.visionGrid, this.arc, this.grids);
}

Particle.prototype.updateConfig = function(config) {
    Object.assign(this.config, config);

    const { showMovementCircle, showVisionGrid } = this.config;

    if (showMovementCircle === true && this.nodes.circle === undefined) {
        this.nodes.circle = createCircleNode(config);
        this.nodes.container.appendChild(this.nodes.circle);
    }

    if (showMovementCircle === false && this.nodes.circle !== undefined) {
        this.nodes.container.removeChild(this.nodes.circle);
        delete this.nodes.circle;
    }

    if (showVisionGrid === true && this.nodes.visionGrid === undefined) {
        this.nodes.visionGrid = createVisionGridNodes(this.config, this.grids, this.nodes);
    }

    if (showVisionGrid === false && this.nodes.visionGrid !== undefined) {
        delete this.nodex.visionGrid;
    }
}

// ===== CREATION =====

function createArc(bounds, grids, config) {
    let arc = {
        centerX: random.num(0, bounds.width),
        centerY: random.num(0, bounds.height),
        clockwise: random.bool(),
        endX: 0,
        endY: 0,
        length: random.num(RAD.t90, RAD.t360),
        radius: random.num(100, 200),
        theta: random.num(RAD.t90, RAD.t360),
    };

    arc.endX = arc.centerX + arc.radius * Math.cos(arc.theta);
    arc.endY = arc.centerY - arc.radius * Math.sin(arc.theta);

    arc = overflowArc(arc, bounds);

    const x = arc.endX - arc.endX % 5;
    const y = arc.endY - arc.endY % 5;

    // If starting in a hazard, recurse.
    if (grids.global[x] !== undefined && grids.global[x][y] !== undefined) {
        arc = createArc(bounds, grids, config);
    }

    return arc;
}

function createBodyNode(config) {
    const node = document.createElement('div');
    node.className = 'particle-body';
    node.style.backgroundColor = config.color;
    return node;
}

function createCircleNode(config) {
    if (config.showMovementCircle === false) {
        return undefined;
    }

    const node = document.createElement('div');
    node.className = 'particle-movement-circle';
    node.style.borderColor = config.color;
    return node;
}

function createContainerNode(config) {
    const node = document.createElement('div');
    node.className = 'particle-container';
    return node;
}

function createVisionGrid(config) {
    const { gridSize: side, visionRadius: radius } = config;
    const r0 = radius;
    const r1 = radius - side;

    const points = [];

    for (let x = -radius; x <= radius; x += side) {
        for (let y = -radius; y <= radius; y += side) {
            // Omit large slices of unused circle
            if (x > y || x < -y) {
                continue;
            }

            // Include vision band
            const r = Math.pow(Math.pow(x, 2) + Math.pow(y, 2), 0.5);
            if (r > r0 || r < r1) {
                continue;
            }

            let alpha = Math.atan(y / x);
            if (x < 0) {
                alpha += RAD.t180;
            }

            points.push({ x, y, r, alpha, touch: false });
        }
    }

    return points;
}

function createVisionGridNodes(config, grids, nodes) {
    if (config.showVisionGrid === false) {
        return undefined;
    }

    return grids.vision.reduce((acc, { x, y }) => {
        const div = document.createElement('div');
        div.className = 'particle-vision-dot';
        div.style.backgroundColor = config.color;
        nodes.container.appendChild(div);

        acc.push(div);

        return acc;
    }, []);
}

// ===== CALCULATIONS =====

function stepArc(arc, { bounds, randomize, speed }) {
    // Randomly change radius and rotation direction.
    if (arc.length <= 0) {
        arc.length = random.num(RAD.t90, RAD.t360);

        if (randomize === true) {
            arc = moveArc(arc, random.num(100, 200));

            if (random.bool(0.8)) {
                arc.clockwise = !arc.clockwise;
                arc = reverseArc(arc);
            }
        }
    }

    // Ensure constant velocity and theta between 0 and 2π.
    const delta = speed / arc.radius;
    arc.length -= delta;

    arc.theta += (arc.clockwise ? -delta : +delta);
    arc.theta = (arc.theta > 0 ? arc.theta % RAD.t360 : RAD.t360 + arc.theta);

    arc.endX = arc.centerX + arc.radius * Math.cos(arc.theta); // TODO perf here
    arc.endY = arc.centerY - arc.radius * Math.sin(arc.theta); // TODO perf here

    // Overflow.
    arc = overflowArc(arc, bounds);

    return arc;
}

function overflowArc(arc, bounds) {
    if (arc.endX < 0) {
        arc.endX += bounds.width;
        arc.centerX += bounds.width
    } else if (arc.endX > bounds.width) {
        arc.endX -= bounds.width;
        arc.centerX -= bounds.width
    }

    if (arc.endY < 0) {
        arc.endY += bounds.height;
        arc.centerY += bounds.height
    } else if (arc.endY > bounds.height) {
        arc.endY -= bounds.height;
        arc.centerY -= bounds.height
    }

    return arc;
}

function moveArc(arc, newRadius) {
    const r0 = arc.radius;
    const r1 = newRadius;

    // Moves arc center to new radius while keeping theta constant.
    arc.centerX -= (r1 - r0) * Math.cos(arc.theta); // TODO perf here
    arc.centerY += (r1 - r0) * Math.sin(arc.theta); // TODO perf here
    arc.radius = r1;

    return arc;
}

function reverseArc(arc) {
    arc.theta = (arc.theta + RAD.t180) % RAD.t360;
    arc.centerX -= (2 * arc.radius) * Math.cos(arc.theta); // TODO perf here
    arc.centerY += (2 * arc.radius) * Math.sin(arc.theta); // TODO perf here

    return arc;
}

function updateVisionGrid(arc, config, grids) {
    const { global, vision } = grids;

    return vision.reduce((acc, point) => {
        const rad = arc.clockwise
            ? point.alpha - arc.theta
            : point.alpha - arc.theta + RAD.t180;

        point.x = point.r * Math.cos(rad);
        point.y = point.r * Math.sin(rad);

        const x = arc.endX + point.x;
        const y = arc.endY + point.y;

        const gridX = x - x % 5;
        const gridY = y - y % 5;

        point.touch = (global[gridX] !== undefined && global[gridX][gridY] !== undefined);

        return acc.concat(point);
    }, []);
}

// ===== ACTIONS =====
function evade(arc, visionGrid) {
    const danger = visionGrid.reduce((acc, v) => acc || v.touch, false);

    if (danger === false) {
        return arc;
    }

    const evasionArc = moveArc(arc, 20);
    evasionArc.length = 1;

    return evasionArc;
}

// ===== RENDERING =====
function repaintContainer(node, arc) {
    node.style.left = `${arc.endX}px`;
    node.style.top = `${arc.endY}px`;
}

function repaintBody(node, arc) {
    const rad = arc.clockwise
        ? RAD.t180 - arc.theta
        : RAD.t360 - arc.theta;

    node.style.transform = `rotate(${rad + RAD.t45}rad)`;
}

function repaintCircle(node, arc) {
    if (node === undefined) {
        return;
    }

    node.style.width = `${2 * arc.radius}px`;
    node.style.height = `${2 * arc.radius}px`;

    node.style.left = `-${arc.radius + arc.radius * Math.cos(arc.theta)}px`;  // TODO perf here
    node.style.top = `-${arc.radius - arc.radius * Math.sin(arc.theta)}px`;   // TODO perf here

    node.style.borderRadius = `${arc.radius}px`;
}

function repaintVisionGrid(nodes, arc, grids) {
    if (nodes === undefined) {
        return;
    }

    grids.vision.forEach(({ x, y, touch }, i) => {
        nodes[i].style.left = `${x}px`;
        nodes[i].style.top = `${y}px`;

        nodes[i].style.border = (touch ? '2px solid red' : '0');
    });
}

export default Particle;