import Vector3 from './Vector3';
import vec3 from '../glmatrix/vec3';

var EPSILON = 1e-5;

/**
 * @constructor
 * @alias clay.Ray
 * @param {clay.Vector3} [origin]
 * @param {clay.Vector3} [direction]
 */
var Ray = function (origin, direction) {
    /**
     * @type {clay.Vector3}
     */
    this.origin = origin || new Vector3();
    /**
     * @type {clay.Vector3}
     */
    this.direction = direction || new Vector3();
};

Ray.prototype = {

    constructor: Ray,

    // http://www.siggraph.org/education/materials/HyperGraph/raytrace/rayplane_intersection.htm
    /**
     * Calculate intersection point between ray and a give plane
     * @param  {clay.Plane} plane
     * @param  {clay.Vector3} [out]
     * @return {clay.Vector3}
     */
    intersectPlane: function (plane, out) {
        var pn = plane.normal.array;
        var d = plane.distance;
        var ro = this.origin.array;
        var rd = this.direction.array;

        var divider = vec3.dot(pn, rd);
        // ray is parallel to the plane
        if (divider === 0) {
            return null;
        }
        if (!out) {
            out = new Vector3();
        }
        var t = (vec3.dot(pn, ro) - d) / divider;
        vec3.scaleAndAdd(out.array, ro, rd, -t);
        out._dirty = true;
        return out;
    },

    /**
     * Mirror the ray against plane
     * @param  {clay.Plane} plane
     */
    mirrorAgainstPlane: function (plane) {
        // Distance to plane
        var d = vec3.dot(plane.normal.array, this.direction.array);
        vec3.scaleAndAdd(this.direction.array, this.direction.array, plane.normal.array, -d * 2);
        this.direction._dirty = true;
    },

    distanceToPoint: (function () {
        var v = vec3.create();
        return function (point) {
            vec3.sub(v, point, this.origin.array);
            // Distance from projection point to origin
            var b = vec3.dot(v, this.direction.array);
            if (b < 0) {
                return vec3.distance(this.origin.array, point);
            }
            // Squared distance from center to origin
            var c2 = vec3.lenSquared(v);
            // Squared distance from center to projection point
            return Math.sqrt(c2 - b * b);
        };
    })(),

    /**
     * Calculate intersection point between ray and sphere
     * @param  {clay.Vector3} center
     * @param  {number} radius
     * @param  {clay.Vector3} out
     * @return {clay.Vector3}
     */
    intersectSphere: (function () {
        var v = vec3.create();
        return function (center, radius, out) {
            var origin = this.origin.array;
            var direction = this.direction.array;
            center = center.array;
            vec3.sub(v, center, origin);
            // Distance from projection point to origin
            var b = vec3.dot(v, direction);
            // Squared distance from center to origin
            var c2 = vec3.squaredLength(v);
            // Squared distance from center to projection point
            var d2 = c2 - b * b;

            var r2 = radius * radius;
            // No intersection
            if (d2 > r2) {
                return;
            }

            var a = Math.sqrt(r2 - d2);
            // First intersect point
            var t0 = b - a;
            // Second intersect point
            var t1 = b + a;

            if (!out) {
                out = new Vector3();
            }
            if (t0 < 0) {
                if (t1 < 0) {
                    return null;
                }
                else {
                    vec3.scaleAndAdd(out.array, origin, direction, t1);
                    return out;
                }
            }
            else {
                vec3.scaleAndAdd(out.array, origin, direction, t0);
                return out;
            }
        };
    })(),

    // http://www.scratchapixel.com/lessons/3d-basic-lessons/lesson-7-intersecting-simple-shapes/ray-box-intersection/
    /**
     * Calculate intersection point between ray and bounding box
     * @param {clay.BoundingBox} bbox
     * @param {clay.Vector3}
     * @return {clay.Vector3}
     */
    intersectBoundingBox: function (bbox, out) {
        var dir = this.direction.array;
        var origin = this.origin.array;
        var min = bbox.min.array;
        var max = bbox.max.array;

        var invdirx = 1 / dir[0];
        var invdiry = 1 / dir[1];
        var invdirz = 1 / dir[2];

        var tmin, tmax, tymin, tymax, tzmin, tzmax;
        if (invdirx >= 0) {
            tmin = (min[0] - origin[0]) * invdirx;
            tmax = (max[0] - origin[0]) * invdirx;
        }
        else {
            tmax = (min[0] - origin[0]) * invdirx;
            tmin = (max[0] - origin[0]) * invdirx;
        }
        if (invdiry >= 0) {
            tymin = (min[1] - origin[1]) * invdiry;
            tymax = (max[1] - origin[1]) * invdiry;
        }
        else {
            tymax = (min[1] - origin[1]) * invdiry;
            tymin = (max[1] - origin[1]) * invdiry;
        }

        if ((tmin > tymax) || (tymin > tmax)) {
            return null;
        }

        if (tymin > tmin || tmin !== tmin) {
            tmin = tymin;
        }
        if (tymax < tmax || tmax !== tmax) {
            tmax = tymax;
        }

        if (invdirz >= 0) {
            tzmin = (min[2] - origin[2]) * invdirz;
            tzmax = (max[2] - origin[2]) * invdirz;
        }
        else {
            tzmax = (min[2] - origin[2]) * invdirz;
            tzmin = (max[2] - origin[2]) * invdirz;
        }

        if ((tmin > tzmax) || (tzmin > tmax)) {
            return null;
        }

        if (tzmin > tmin || tmin !== tmin) {
            tmin = tzmin;
        }
        if (tzmax < tmax || tmax !== tmax) {
            tmax = tzmax;
        }
        if (tmax < 0) {
            return null;
        }

        var t = tmin >= 0 ? tmin : tmax;

        if (!out) {
            out = new Vector3();
        }
        vec3.scaleAndAdd(out.array, origin, dir, t);
        return out;
    },

    // http://en.wikipedia.org/wiki/M%C3%B6ller%E2%80%93Trumbore_intersection_algorithm
    /**
     * Calculate intersection point between ray and three triangle vertices
     * @param {clay.Vector3} a
     * @param {clay.Vector3} b
     * @param {clay.Vector3} c
     * @param {boolean}           singleSided, CW triangle will be ignored
     * @param {clay.Vector3} [out]
     * @param {clay.Vector3} [barycenteric] barycentric coords
     * @return {clay.Vector3}
     */
    intersectTriangle: (function () {

        var eBA = vec3.create();
        var eCA = vec3.create();
        var AO = vec3.create();
        var vCross = vec3.create();

        return function (a, b, c, singleSided, out, barycenteric) {
            var dir = this.direction.array;
            var origin = this.origin.array;
            a = a.array;
            b = b.array;
            c = c.array;

            vec3.sub(eBA, b, a);
            vec3.sub(eCA, c, a);

            vec3.cross(vCross, eCA, dir);

            var det = vec3.dot(eBA, vCross);

            if (singleSided) {
                if (det > -EPSILON) {
                    return null;
                }
            }
            else {
                if (det > -EPSILON && det < EPSILON) {
                    return null;
                }
            }

            vec3.sub(AO, origin, a);
            var u = vec3.dot(vCross, AO) / det;
            if (u < 0 || u > 1) {
                return null;
            }

            vec3.cross(vCross, eBA, AO);
            var v = vec3.dot(dir, vCross) / det;

            if (v < 0 || v > 1 || (u + v > 1)) {
                return null;
            }

            vec3.cross(vCross, eBA, eCA);
            var t = -vec3.dot(AO, vCross) / det;

            if (t < 0) {
                return null;
            }

            if (!out) {
                out = new Vector3();
            }
            if (barycenteric) {
                Vector3.set(barycenteric, (1 - u - v), u, v);
            }
            vec3.scaleAndAdd(out.array, origin, dir, t);

            return out;
        };
    })(),

    /**
     * Apply an affine transform matrix to the ray
     * @return {clay.Matrix4} matrix
     */
    applyTransform: function (matrix) {
        Vector3.add(this.direction, this.direction, this.origin);
        Vector3.transformMat4(this.origin, this.origin, matrix);
        Vector3.transformMat4(this.direction, this.direction, matrix);

        Vector3.sub(this.direction, this.direction, this.origin);
        Vector3.normalize(this.direction, this.direction);
    },

    /**
     * Copy values from another ray
     * @param {clay.Ray} ray
     */
    copy: function (ray) {
        Vector3.copy(this.origin, ray.origin);
        Vector3.copy(this.direction, ray.direction);
    },

    /**
     * Clone a new ray
     * @return {clay.Ray}
     */
    clone: function () {
        var ray = new Ray();
        ray.copy(this);
        return ray;
    }
};

export default Ray;