#include <algorithm>

#include "Collision/Collision.h"
#include "Engine/GLM.h"
#include "Core/World.h"
#include "Rendering/Model.h"

namespace Collision
{

//note: this one hasnt been delta adjusted like RayVsAABB has
bool RayAABBIntr(const Ray& ray, const AABB& box)
{
    glm::vec3 w = 75.0f * ray.Direction();
    glm::vec3 v = glm::abs(w);
    glm::vec3 c = ray.Origin() - box.Origin() + w;
    glm::vec3 half = box.HalfSize();

    if (abs(c.x) > v.x + half.x) {
        return false;
    }
    if (abs(c.y) > v.y + half.y) {
        return false;
    }
    if (abs(c.z) > v.z + half.z) {
        return false;
    }

    if (abs(c.y*w.z - c.z*w.y) > half.y*v.z + half.z*v.y) {
        return false;
    }
    if (abs(c.x*w.z - c.z*w.x) > half.x*v.z + half.z*v.x) {
        return false;
    }
    return !(abs(c.x*w.y - c.y*w.x) > half.x*v.y + half.y*v.x);
}

bool RayVsAABB(const Ray& ray, const AABB& box)
{
    float dummy;
    return RayVsAABB(ray, box, dummy);
}

bool RayVsAABB(const Ray& ray, const AABB& box, float& outDistance)
{
    glm::vec3 invdir = 1.0f / ray.Direction();
    glm::vec3 origin = ray.Origin();

    float t1 = (box.MinCorner().x - origin.x)*invdir.x;
    float t2 = (box.MaxCorner().x - origin.x)*invdir.x;
    float t3 = (box.MinCorner().y - origin.y)*invdir.y;
    float t4 = (box.MaxCorner().y - origin.y)*invdir.y;
    float t5 = (box.MinCorner().z - origin.z)*invdir.z;
    float t6 = (box.MaxCorner().z - origin.z)*invdir.z;

    float tmin = std::max(std::max(std::min(t1, t2), std::min(t3, t4)), std::min(t5, t6));
    float tmax = std::min(std::min(std::max(t1, t2), std::max(t3, t4)), std::max(t5, t6));

    //if (tmax < 0 || tmin > tmax)
    //if tmin,tmax are almost the same (i.e. hitting exactly in the corner) then tmin might be slightly 
    //greater than tmax becuase of floating-precision problems. fixed by adding a small delta to tmax
    if (tmax < 0 || tmin>(tmax + 0.0001f))
        return false;

    outDistance = (tmin > 0) ? tmin : tmax;
    return true;
}

bool AABBVsAABB(const AABB& a, const AABB& b)
{
    const glm::vec3& aCenter = a.Origin();
    const glm::vec3& bCenter = b.Origin();
    const glm::vec3& aHSize = a.HalfSize();
    const glm::vec3& bHSize = b.HalfSize();
    //Test will probably exit because of the X and Z axes more often, so test them first.
    if (abs(aCenter[0] - bCenter[0]) > (aHSize[0] + bHSize[0])) {
        return false;
    }
    if (abs(aCenter[2] - bCenter[2]) > (aHSize[2] + bHSize[2])) {
        return false;
    }
    return (abs(aCenter[1] - bCenter[1]) <= (aHSize[1] + bHSize[1]));
}

bool AABBVsAABB(const AABB& a, const AABB& b, glm::vec3& minimumTranslation)
{
    minimumTranslation = glm::vec3(0, 0, 0);
    const glm::vec3& aMax = a.MaxCorner();
    const glm::vec3& bMax = b.MaxCorner();
    const glm::vec3& aMin = a.MinCorner();
    const glm::vec3& bMin = b.MinCorner();
    const glm::vec3& bSize = b.Size();
    const glm::vec3& aSize = a.Size();
    float minOffset = INFINITY;
    float off;
    auto axisesIntersecting = glm::tvec3<bool, glm::highp>(false, false, false);
    for (int i = 0; i < 3; ++i) {
        off = bMax[i] - aMin[i];
        if (off > 0 && off < bSize[i] + aSize[i]) {
            if (off < minOffset) {
                minimumTranslation = glm::vec3();
                minimumTranslation[i] = minOffset = off;
            }
            axisesIntersecting[i] = true;
        }
        off = aMax[i] - bMin[i];
        if (off > 0 && off < bSize[i] + aSize[i]) {
            if (off < minOffset) {
                minOffset = off;
                minimumTranslation = glm::vec3();
                minimumTranslation[i] = -off;
            }
            axisesIntersecting[i] = true;
        }
    }
    return glm::all(axisesIntersecting);
}

bool RayVsModel(const Ray& ray,
    const std::vector<RawModel::Vertex>& modelVertices,
    const std::vector<unsigned int>& modelIndices)
{
    for (int i = 0; i < modelIndices.size(); ++i) {
        glm::vec3 v0 = modelVertices[modelIndices[i]].Position;
        glm::vec3 e1 = modelVertices[modelIndices[++i]].Position - v0;		//v1 - v0
        glm::vec3 e2 = modelVertices[modelIndices[++i]].Position - v0;		//v2 - v0
        glm::vec3 m = ray.Origin() - v0;
        glm::vec3 MxE1 = glm::cross(m, e1);
        glm::vec3 DxE2 = glm::cross(ray.Direction(), e2);
        float DetInv = glm::dot(e1, DxE2);
        if (std::abs(DetInv) < FLT_EPSILON) {
            continue;
        }
        DetInv = 1.0f / DetInv;
        float u = glm::dot(m, DxE2) * DetInv;
        float v = glm::dot(ray.Direction(), MxE1) * DetInv;
        //u,v can be very close to 0 but still negative sometimes. added a deltafactor to compensate for that problem
        if ((u + 0.001f) < 0 || (v + 0.001f) < 0 || 1 < u + v) {
            continue;
        }
        //Here, u and v are positive, u+v <= 1, and if distance is positive - triangle is hit.
        if (0 <= glm::dot(e2, MxE1) * DetInv) {
            return true;
        }
    }
    return false;
}

bool RayVsModel(const Ray& ray,
    const std::vector<RawModel::Vertex>& modelVertices,
    const std::vector<unsigned int>& modelIndices,
    float& outDistance,
    float& outUCoord,
    float& outVCoord)
{
    outDistance = INFINITY;
    bool hit = false;
    for (int i = 0; i < modelIndices.size(); ++i) {
        glm::vec3 v0 = modelVertices[modelIndices[i]].Position;
        glm::vec3 e1 = modelVertices[modelIndices[++i]].Position - v0;		//v1 - v0
        glm::vec3 e2 = modelVertices[modelIndices[++i]].Position - v0;		//v2 - v0
        glm::vec3 m = ray.Origin() - v0;
        glm::vec3 MxE1 = glm::cross(m, e1);
        glm::vec3 DxE2 = glm::cross(ray.Direction(), e2);//pVec
        float DetInv = glm::dot(e1, DxE2);
        if (std::abs(DetInv) < FLT_EPSILON) {
            continue;
        }
        DetInv = 1.0f / DetInv;
        float dist = glm::dot(e2, MxE1) * DetInv;
        if (dist >= outDistance) {
            continue;
        }
        float u = glm::dot(m, DxE2) * DetInv;
        float v = glm::dot(ray.Direction(), MxE1) * DetInv;

        //u,v can be very close to 0 but still negative sometimes. added a deltafactor to compensate for that problem
        //If u and v are positive, u+v <= 1, dist is positive, and less than closest.
        if (0 <= (u + 0.001f) && 0 <= (v + 0.001f) && u + v <= 1 && 0 <= dist) {
            outDistance = dist;
            outUCoord = u;
            outVCoord = v;
            hit = true;
        }
    }
    return hit;
}

bool RayVsModel(const Ray& ray,
    const std::vector<RawModel::Vertex>& modelVertices,
    const std::vector<unsigned int>& modelIndices,
    glm::vec3& outHitPosition)
{
    float u;
    float v;
    float dist;
    bool hit = RayVsModel(ray, modelVertices, modelIndices, dist, u, v);
    outHitPosition = ray.Origin() + dist * ray.Direction();
    return hit;
}

bool AABBvsTriangles(const AABB& box, const std::vector<RawModel::Vertex>& modelVertices, const std::vector<unsigned int>& modelIndices, const glm::mat4& modelMatrix, glm::vec3& outResolutionVector)
{
    bool hit = false;
    
    const glm::vec3& origin = box.Origin();
    const glm::vec3& min = box.MinCorner();
    const glm::vec3& max = box.MaxCorner();

    outResolutionVector.x = INFINITY;

    for (int i = 0; i < modelIndices.size(); ++i) {
        glm::vec3 p = modelVertices[i].Position;
        p = glm::vec3(modelMatrix * glm::vec4(p.x, p.y, p.z, 1));

        float distFromOrigin = glm::abs(origin.x - p.x);
        float penetration = box.HalfSize().x - distFromOrigin;
        if (penetration > 0 && penetration < glm::abs(outResolutionVector.x)) {
            if (p.x > origin.x) {
                outResolutionVector.x = -penetration;
            } else {
                outResolutionVector.x = penetration;
            }
            hit = true;
        }
        //glm::vec3 pLocal = origin - p;
        //for (int axis = 0; axis < 3; ++axis) {
        //    if (p[axis] < min[axis] || p[axis] > max[axis]) {
        //        continue;
        //    }

        //    if (glm::abs(pLocal[axis]) < box.HalfSize()[axis]) {
        //        outResolutionVector[axis] = (glm::sign(pLocal[axis]) * box.HalfSize()[axis]) - pLocal[axis];
        //        hit = true;
        //    }
        //}
    }

    return hit;
}

bool attachAABBComponentFromModel(World* world, EntityID id)
{
    if (!world->HasComponent(id, "Model")) {
        return false;
    }
    ComponentWrapper model = world->GetComponent(id, "Model");
    ComponentWrapper collision = world->AttachComponent(id, "AABB");
    Model* modelRes = ResourceManager::Load<Model>(model["Resource"]);
    if (modelRes == nullptr) {
        return false;
    }

    glm::mat4 modelMatrix = modelRes->Matrix();

    glm::vec3 mini = glm::vec3(INFINITY, INFINITY, INFINITY);
    glm::vec3 maxi = glm::vec3(-INFINITY, -INFINITY, -INFINITY);
	for (unsigned int i = 0; i < modelRes->NumberOfVertices(); i++) {
		const auto& v = modelRes->Vertices()[i];
        const auto& wPos = modelMatrix * glm::vec4(v.Position.x, v.Position.y, v.Position.z, 1);
        maxi.x = std::max(wPos.x, maxi.x);
        maxi.y = std::max(wPos.y, maxi.y);
        maxi.z = std::max(wPos.z, maxi.z);
        mini.x = std::min(wPos.x, mini.x);
        mini.y = std::min(wPos.y, mini.y);
        mini.z = std::min(wPos.z, mini.z);
    }
    collision["Origin"] = 0.5f * (maxi + mini);
    collision["Size"] = maxi - mini;
    return true;
}

boost::optional<EntityAABB> EntityAbsoluteAABB(EntityWrapper& entity)
{
    if (!entity.HasComponent("AABB")) {
        return boost::none;
    }

    ComponentWrapper& cAABB = entity["AABB"];
    glm::vec3 absPosition = Transform::AbsolutePosition(entity.World, entity.ID);
    glm::vec3 absScale = Transform::AbsoluteScale(entity.World, entity.ID);
    glm::vec3 origin = absPosition + (glm::vec3)cAABB["Origin"];
    glm::vec3 size = (glm::vec3)cAABB["Size"] * absScale;

    EntityAABB aabb = EntityAABB::FromOriginSize(origin, size);
    aabb.Entity = entity;

    return aabb;
}

}