/**
 * Particle animation class.
 *
 * @copyright Dennis Eichhorn
 * @license   OMS License 2.2
 * @version   1.0.0
 * @since     1.0.0
 */
(function (jsOMS)
{
    'use strict';

    /** @namespace jsOMS.Animation.Canvas */
    jsOMS.Autoloader.defineNamespace('jsOMS.Animation.Canvas');

    jsOMS.Animation.Canvas.ParticleAnimation = class {
        /**
         *
         * @param {Object} canvas Canvas
         *
         * @constructor
         *
         * @since 1.0.0
         */
        constructor (canvas)
        {
            this.canvas = canvas;
            this.ctx    = canvas.getContext('2d');

            /** global: screen */
            this.width  = screen.width;
            this.height = screen.height;

            this.canvas.width  = this.width;
            this.canvas.height = this.height;

            this.particles   = [];
            this.maxDistance = 70;
            this.gravitation = 10000000;

            for (let i = 0; i < this.width * this.height / 3000; ++i) {
                this.particles.push(new jsOMS.Animation.Canvas.Particle(
                    Math.random() * this.width,
                    Math.random() * this.height,
                    -1 + Math.random() * 2,
                    -1 + Math.random() * 2,
                    1
                ));
            }
        };

        /**
         * Draw everything
         *
         * @param {Object} self Object reference for self invoke
         *
         * @return {void}
         *
         * @method
         *
         * @since 1.0.0
         */
        draw (self)
        {
            self = typeof self !== 'undefined' ? self : this;
            self.invalidate();

            const length = self.particles.length;

            for (let i = 0; i < length; ++i) {
                self.particles[i].draw(self.ctx);
            }

            self.updateParticles();
            jsOMS.Animation.Animation.requestAnimationFrame.call(window, function ()
            {
                self.draw(self);
            });
        };

        /**
         * Invalidate/clean canvas
         *
         * @return {void}
         *
         * @method
         *
         * @since 1.0.0
         */
        invalidate ()
        {
            this.ctx.clearRect(0, 0, this.width, this.height);
        };

        /**
         * Update particle
         *
         * @return {void}
         *
         * @method
         *
         * @since 1.0.0
         */
        updateParticles ()
        {
            let particle;
            let pos;
            let vel;
            let radius;

            const length = this.particles.length;

            for (let i = 0; i < length; ++i) {
                particle = this.particles[i];
                pos      = particle.getPosition();
                vel      = particle.getVelocity();
                radius   = particle.getRadius();

                pos.x += vel.x;
                pos.y += vel.y;

                // Change on wall hit
                if (pos.x + radius > this.width) {
                    pos.x = radius;
                } else if (pos.x - radius < 0) {
                    pos.x = this.width - radius;
                }

                if (pos.y + radius > this.height) {
                    pos.y = radius;
                } else if (pos.y - radius < 0) {
                    pos.y = this.height - radius;
                }

                particle.setPosition(pos.x, pos.y);
                particle.setVelocity(vel.x, vel.y);

                for (let j = i + 1; j < length; ++j) {
                    this.updateDistance(particle, this.particles[j]);
                }
            }
        };

        /**
         * Handle distance between particles
         *
         * @param {Particle} p1 Particle
         * @param {Particle} p2 Particle
         *
         * @return {void}
         *
         * @method
         *
         * @since 1.0.0
         */
        updateDistance (p1, p2)
        {
            const pos1 = p1.getPosition();
            const pos2 = p2.getPosition();
            const dx   = pos1.x - pos2.x;
            const dy   = pos1.y - pos2.y;
            const dist = Math.sqrt(dx * dx + dy * dy);

            const vel1 = p1.getVelocity();
            const vel2 = p2.getVelocity();

            // Draw line if particles are close
            if (dist <= this.maxDistance) {
                this.ctx.beginPath();
                this.ctx.strokeStyle = 'rgba(255, 255, 255, ' + ((1.2 - dist / this.maxDistance) * 0.5) + ')';
                this.ctx.moveTo(pos1.x, pos1.y);
                this.ctx.lineTo(pos2.x, pos2.y);
                this.ctx.stroke();
                this.ctx.closePath();

                // Accelerate based on distance (no acceleration yet)
                const ax = dx / this.gravitation;
                const ay = dy / this.gravitation;

                vel1.x -= ax;
                vel1.y -= ay;
                p1.setVelocity(vel1.x, vel1.y);

                vel2.x -= ax;
                vel2.y -= ay;
                p2.setVelocity(vel2.x, vel2.y);
            }
        };
    };
}(window.jsOMS = window.jsOMS || {}));