class Boid {

    constructor(radius, color, x, y, direction, id, scene_width, scene_height) {
        // Boid properties
        this.radius = radius;
        this.color = color;
        this.x = x;
        this.y = y;
        this.direction = direction;
        this.id = id;

        // World properties
        this.scene_width = scene_width;
        this.scene_height = scene_height;

        // Boid "dynamic" properties
        this.rayLength = 40;
        this.turnStepAmount = 20;
        this.stepAmount = 4;
        this.fieldOfView = 270;
        this.boidBuffer = 20;
    }

    move(boids) {
        // this.direction += Math.random() * (2 * this.turnStepAmount) - this.turnStepAmount

        this.direction = this.findNextRay(boids);

        var vector = this.findPoint(this.x, this.y, this.stepAmount, this.direction);
        this.x = vector.x;
        this.y = vector.y;
    }

    buildRays() {
        let rays = new Array();

        let rayInteval = 2;
        let noOfSteps = this.fieldOfView / rayInteval;
        let is_clockwise = Math.random() >= 0.5;

        for (let i = 0; i < noOfSteps / 2; i++) {
            if (i == 0) {
                rays.push(rayInteval * i);
                continue;
            }

            if (is_clockwise) {
                rays.push(rayInteval * -i);
            }

            rays.push(rayInteval * i);

            if (!is_clockwise) {
                rays.push(rayInteval * -i);
            }
        }

        return rays;
    }

    findNextRay(boids) {
        let rays = this.buildRays();

        for (let i = 0; i < rays.length; i++) {
            let tweakAngle = 0;
            // if (Math.random() > 0.95) {
            //     tweakAngle = this.turnStepAmount * Math.random() - (this.turnStepAmount / 2);
            // }

            let rayAngle = tweakAngle + this.direction + rays[i];

            // Check against all other boids
            if (this.detectBoids(rayAngle, boids)) {
                continue;
            }

            // Check against scene boundaries
            if (this.detectBox(this.scene_width, this.scene_height, rayAngle)) {
                continue;
            }

            return rayAngle;
        }

        console.log('cannot find suitable ray');
        return false;
    }

    detectBoids(direction, boids) {
        for (let i = 0; i < boids.length; i++) {
            if (this.detectBoid(direction, boids[i])) {
                return true;
            }
        }

        return false;
    }

    detectBoid(direction, boid) {
        // rule out ourselves
        if (this.id == boid.id) {
            return false;
        }

        // let cross = this.doPathsCross(direction, boid);
        //
        // if (cross) {
        //     console.log('paths cross detected');
        // }

        let intersect = this.boidsIntersect(boid);

        if (intersect) {
            console.log('boids intersect detected');
        }

        return intersect;
    }

    boidsIntersect(boid) {
        return this.twoCirclesIntersect(this.radius, boid.radius, this.x, boid.x, this.y, boid.y);
    }

    twoCirclesIntersect(r1, r2, x1, x2, y1, y2) {
        // from https://planetcalc.com/8098/ (bottom of page)
        // https://mathworld.wolfram.com/Circle-CircleIntersection.html
        // d is the abs distance between the two circles center
        let d = this.distanceBetweenPoints(x1, x2, y1, y2);

        // a is distance to our x3 point ( I think )
        let a = (Math.pow(r1, 2) - Math.pow(r2, 2) + Math.pow(d, 2)) / (2 * d);

        // h is some other segment of some other circle ( I dont really know )
        let h = Math.sqrt(Math.pow(r1, 2) - Math.pow(a, 2));

        // x3 and y3 represent the point between the two circle midpoints, perpindicular to which will be our intersects
        // ( maybe )
        let x3 = x1 + ((a / d) * (x2 - x1));
        let y3 = y1 + ((a / d) * (y2 - y1));

        // x4 and y4 are one of the intersect points
        let x4 = x3 + ((h / d) * (y2 - y1));
        let y4 = y3 - ((h / d) * (x2 - x1));

        if (!x4 || !y4) {
            return false;
        }
        console.log('intersecting circles');
        return {
            x: x4,
            y: y4
        };
    }

    distanceBetweenPoints(x1, x2, y1, y2) {
        let dx = Math.abs(x1 - x2);
        let dy = Math.abs(y1 - y2);

        return Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
    }

    doPathsCross(direction, boid) {
        let thisFututrePosition = this.findPoint(this.x, this.y, this.boidBuffer, direction);
        let thisPath = {
            x1: this.x,
            y1: this.y,
            x2: thisFututrePosition.x,
            y2: thisFututrePosition.y
        };

        let boidFuturePosition = this.findPoint(boid.x, boid.y, boid.boidBuffer, boid.direction);
        let boidPath = {
            x1: boid.x,
            y1: boid.y,
            x2: boidFuturePosition.x,
            y2: boidFuturePosition.y
        };

        let thisIntersectsBoid = this.pathsIntersect(
            thisPath.x1, thisPath.y1, thisPath.x2, thisPath.y2, boidPath.x1, boidPath.y1, boidPath.x2, boidPath.y2
        );

        if (thisIntersectsBoid) {
            return true;
        }

        return false;
    }

    pathsIntersect(x1, y1, x2, y2, x3, y3, x4, y4) {
        // Check if none of the lines are of length 0
        if ((x1 === x2 && y1 === y2) || (x3 === x4 && y3 === y4)) {
            return false
        }

        let denominator = ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))

        // // Lines are parallel
        // if (denominator === 0) {
        //     return false
        // }

        let ua = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / denominator
        let ub = ((x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)) / denominator

        // is the intersection along the segments
        if (ua < 0 || ua > 1 || ub < 0 || ub > 1) {
            return false
        }

        // Return a object with the x and y coordinates of the intersection
        let x = x1 + ua * (x2 - x1)
        let y = y1 + ua * (y2 - y1)

        return {
            x,
            y
        }
    }

    detectBox(width, height, direction) {
        let point = this.findPoint(this.x, this.y, this.rayLength, direction);

        if (point.x - this.radius < 0 ||
            point.y - this.radius < 0 ||
            point.x + this.radius > width - 0 ||
            point.y + this.radius > height - 0
        ) {
            return true;
        }

        return false;
    }

    findPoint(x1, y1, length, angle) {
        angle *= Math.PI / 180;

        var x2 = x1 + length * Math.cos(angle),
            y2 = y1 + length * Math.sin(angle);

        return {
            x: x2,
            y: y2
        };
    }

    draw(context) {
        this.drawBoid(context);
        // this.drawRay(context, this.x, this.y, this.rayLength, this.direction);
    }

    drawBoid(context) {
        context.beginPath();
        context.fillStyle = "blue";
        context.arc(this.x, this.y, this.radius, 0, 2 * Math.PI);
        context.stroke();
        context.restore();
    }

    drawRay(context, x, y, perceptionDistance, direction) {
        let point = this.findPoint(x, y, perceptionDistance, direction);
        context.lineWidth = 1;
        context.beginPath();
        context.moveTo(x, y);
        context.lineTo(point.x, point.y);
        context.stroke();
        context.restore();
    }
}