// Single particle movement.
// Goal: per-frame decisions
// 20 x 20 grid

// The trickiest portion of this iteration was animating the curved paths.  Calculating arc length (for scalar speed) along an elliptical
// geometry is quite difficult, so the current solution uses circular paths, which change radius and sometimes rotation after a random
// number of frames have emitted.  A smoothstep cubic curve was considered, but maintaining consistent entry and exit angles will affect
// performance for large particle counts.

// This algorithm travels a random period of time around a random arc.
// If a wall is detected, a 180-degree turn is executed.

import Rx, { Observable } from 'rxjs';
import AnimationBase from './animation0';
import DOM from './dom';
import Store from './store';

const speed = 4;
const visionRadius = 50;
const grid = {};
const t45 = Math.PI / 4;
const t90 = Math.PI / 2;
const t270 = 3 * Math.PI / 2;
const t360 = Math.PI * 2;

const movementCircle = document.createElement('div');
movementCircle.className = 'anim3-movement-circle';

const visionGrid = document.createElement('div');
visionGrid.className = 'anim3-vision-grid';

const particle = document.createElement('div');
particle.className = 'anim3-particle';

const visionGridPoints = calculateVisionGridPoints();

function move(store) {
    let {
        clockwise,
        interval,
        circleX,
        circleY,
        particleX,
        particleY,
        radius,
        theta
    } = store.get();

    // If wall detected, tight 180
    if (detectWall(store) && radius !== 20) {
        const radius0 = radius;
        radius = 20;
        interval = Math.PI * 20 / speed;
        circleX -= (radius - radius0) * Math.cos(theta);
        circleY += (radius - radius0) * Math.sin(theta);
    } else if (interval <= 0) {
        const radius0 = radius;

        interval = Math.round(Math.random() * 10) + 50;
        radius = Math.round(Math.random() * 200) + 50;

        if (Math.random() < 0.5) {
            clockwise = !clockwise;
            theta = (theta + Math.PI) % t360;
            circleX -= (radius + radius0) * Math.cos(theta);
            circleY += (radius + radius0) * Math.sin(theta);
        } else {
            circleX -= (radius - radius0) * Math.cos(theta);
            circleY += (radius - radius0) * Math.sin(theta);
        }
    }

    interval -= 1;

    const delta = speed / radius;
    theta += (clockwise ? -delta : +delta);
    theta = (theta > 0 ? theta % t360 : t360 - theta);

    particleX = circleX + radius * Math.cos(theta);
    particleY = circleY - radius * Math.sin(theta);

    store.set({
        clockwise,
        interval,
        circleX,
        circleY,
        particleX,
        particleY,
        radius,
        theta
    });
}

function detectWall(store) {
    const len = visionGridPoints.length;

    const { particleX, particleY } = store.get();

    const gridX = particleX - particleX % 5;
    const gridY = particleY - particleY % 5;

    for (let i = 0; i < len; i++) {
        const { x, y } = visionGridPoints[i];
        const xx = x + gridX;
        const yy = y + gridY;

        if (grid[xx] && grid[xx][yy] && grid[xx][yy].type === 'wall') {
            console.warn("Wall detected", xx, yy);
            // TODO this goes somewhere else
            // DOM.container.dispatchEvent(new CustomEvent('stop'));
            return true;
        }
    }

    return false;
}

function transformMovementCircle(store) {
    // TODO UPDATE ONLY IF THETA CHANGED - MUST HAVE PREVSTATE
    const { circleX, circleY, radius, theta } = store.get();
    const r = Math.abs(radius);

    movementCircle.style.left = `${circleX - r}px`;
    movementCircle.style.top = `${circleY - r}px`;
    movementCircle.style.height = `${2 * r}px`;
    movementCircle.style.width = `${2 * r}px`;
    movementCircle.style.borderRadius = `${r}px`;
}

function transformParticle(store) {
    const { clockwise, particleX, particleY, theta } = store.get();
    const rad = clockwise ? Math.PI - theta : t360 - theta;

    particle.style.left = `${particleX}px`;
    particle.style.top = `${particleY}px`;
    particle.style.transform = `rotate(${rad}rad)`;
}

function transformVisionGrid(store) {
    const {
        circleX,
        circleY,
        clockwise,
        particleX,
        particleY,
        radius,
        theta
    } = store.get();

    const r0 = Math.min(theta, theta - Math.PI);
    const r1 = Math.max(theta, theta + Math.PI);

    const gridX = particleX - particleX % 5;
    const gridY = particleY - particleY % 5;

    visionGridPoints.forEach(({ x, y, alpha, div }, i) => {
        if (alpha >= 0 && alpha <= r0) {
            div.style.display = (clockwise ? 'none' : 'block');
        } else if (alpha >= theta && alpha <= r1) {
            div.style.display = (clockwise ? 'none' : 'block');
        } else {
            div.style.display = (clockwise ? 'block' : 'none');
        }

        div.style.left = `${x + gridX}px`;
        div.style.top = `${-y + gridY}px`;
    });
}

function calculateVisionGridPoints() {
    const gridSize = 5;

    const squareGrid = [];
    for (let x = -visionRadius; x <= visionRadius; x += gridSize) {
        for (let y = -visionRadius; y <= visionRadius; y += gridSize) {
            let alpha = Math.atan(y / x);

            if (x === 0 && y === 0) {
                alpha = 0;
            } else if (x === 0 && y < 0) {
                alpha = t270;
            } else if (y === 0 && x < 0) {
                alpha = Math.PI;
            } else if (x === 0 && y > 0) {
                alpha = t90;
            } else if (x < 0 && y < 0) {
                alpha = alpha + Math.PI;
            } else if (x <= 0) {
                alpha = Math.PI + alpha;
            } else if (y < 0) {
                alpha = 2 * Math.PI + alpha;
            }

            squareGrid.push({ x, y, alpha });
        }
    }

    const r0 = Math.pow(visionRadius, 2);
    const r1 = Math.pow(visionRadius - gridSize, 2);

    return squareGrid.reduce((acc, point) => {
        const p = Math.pow(point.x, 2) + Math.pow(point.y, 2);
        if (p > r0 || p < r1) {
            return acc;
        }

        const div = document.createElement('div');
        div.className = 'anim3-dot';

        acc.push(Object.assign(point, { div }));
        return acc;
    }, []);
}

function reset() {
    while (DOM.container.childNodes.length) {
        DOM.container.removeChild(DOM.container.firstChild);
    }

    const store = new Store({
        clockwise: false,
        interval: 10,
        circleX: 300,
        circleY: 300,
        radius: 270,
        theta: Math.PI * 3 / 4
    });

    move(store);

    transformParticle(store);
    // transformMovementCircle(store);
    // transformVisionGrid(store);

    DOM.container.appendChild(particle);
    DOM.container.appendChild(movementCircle);

    visionGridPoints.forEach(point => {
        DOM.container.appendChild(point.div);
    });

    return store;
};

function init() {
    const store = reset();

    for (let x = 0; x <= 600; x += 5) {
        grid[x] = {};
        for (let y = 0; y <= 600; y += 5) {
            grid[x][y] = { type: null };

            if (x === 0 || y === 0 || x === 600 || y === 600) {
                grid[x][y] = { type: 'wall' };
            }
        }
    }

    const stop$ = Rx.Observable.fromEvent(DOM.container, 'stop');
    const fps$ = Rx.Observable.interval(1000 / 32)
        .map(_ => store)
        // .take(300)
        // .take(15)
        .takeUntil(stop$); console.error("CLICK TO STOP");

    const click$ = Rx.Observable.fromEvent(DOM.container, 'click');
    click$.subscribe(() => {
        DOM.container.dispatchEvent(new CustomEvent('stop'));
    });

    fps$.subscribe(move);
    fps$.subscribe(transformParticle);
    // fps$.subscribe(transformMovementCircle);
    fps$.subscribe(transformVisionGrid);
};

const Animation3 = Object.assign({}, AnimationBase, { init, reset });

export default Animation3;