import Rx, { Observable } from 'rxjs';
import { BEHAVIOR, ENTITIES, RAD } from './enums';
import Arc from './arc';
import Random from './random';

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

function Particle(parent, bounds, config, globalGrid) {
    this.config = Object.assign({}, {
        behavior: BEHAVIOR.FREE,
        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.id = Random.id(6);

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

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

    this.leader = null;
    this.isLeader = false;

    this.arc = Arc.create(bounds, this.grids.global);
    this.updateConfig(this.config);
    this.nextFrame(globalGrid);
};

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

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

Particle.prototype.nextFrame = function() {
    this.arc = Arc.step(this.arc, this.config.bounds, this.config.speed);

    if (this.leader !== null) {
        this.arc = Arc.follow(this.arc, this.leader.arc);
    } else if (this.arc.length <= 0 && this.config.randomize) {
        this.arc = Arc.randomize(this.arc);
    }

    this.grids.vision = updateVisionGrid(this.arc, this.config, this.grids);
    const { hazards, particles } = look(this.arc, this.grids);

    if (hazards.length > 0) {
        this.arc = Arc.evade(this.arc);
    }

    this.updateLeader(particles);

    repaintContainer(this.nodes.container, this.arc);
    repaintBody(this.nodes.body, this.arc, this.isLeader);
    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;
    }
}

Particle.prototype.updateLeader = function(particles) {
    if (this.config.behavior !== BEHAVIOR.COHESION) {
        return;
    }

    if (this.leader === null && particles.length > 0) {
        // Head-to-head: particles see eachother but shouldn't both lead.
        const candidates = particles
            .filter(v => v.leader ? (v.leader.id !== this.id) : true);

        const leader = candidates.find(v => v.isLeader) || candidates[0];

        if (leader !== undefined) {
            leader.isLeader = true;
            this.leader = leader;
        }
    }

    if (this.leader === null) {
        return;
    }

    if (this.leader.nodes === undefined) {
        this.leader = null;
        return;
    }

    if (this.leader.leader !== null) {
        this.leader = this.leader.leader;
    }

    if (this.isLeader) {
        this.isLeader = false;
    }

    // Beware of circular leadership, where a leader sees its tail.
    if (this.leader.id === this.id) {
        this.leader = null;
    }
}

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

    return vision.reduce((acc, point) => {
        const x = arc.endX + point.x;
        const y = arc.endY + point.y;
        const p = global.getPoint({ x, y, type: ENTITIES.PARTICLE });

        if (p) {
            acc.particles.push(p);
        }

        if (global.getPoint({ x, y, type: ENTITIES.HAZARD })) {
            acc.hazards.push({ x, y });
        }

        return acc;
    }, { hazards: [], particles: [] });
}

// ===== DOM CREATION =====

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, id) {
    const node = document.createElement('div');
    node.className = 'particle-container';
    node.id = id;
    return node;
}

function createVisionGrid(config) {
    const { gridSize: side, visionRadius: radius } = config;
    const r0 = radius;
    const r1 = 45;

    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;
    }, []);
}


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);

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

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

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

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

    isLeader ? node.style.outline = '1px solid red' : node.style.outline = '';
}

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 = `-${arc.radius + arc.radius * arc.cosTheta}px`;
    node.style.top = `-${arc.radius - arc.radius * arc.sinTheta}px`;

    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;