#include "sphere.h"

#define M_PI 3.14159265358979323846
#define MAGIC_RATIO 0.37139f

Sphere::Sphere(int n)
{
    // icosahedron :

    // top cap
    createVertex(0, 1);
    for(int i=0; i<5; i++)
        createVertex(i/5.f, 1-MAGIC_RATIO);

    // bottom cap
    createVertex(0, 0);
    for(int i=0; i<5; i++)
        createVertex((i+0.5f)/5.f, MAGIC_RATIO);

    // Compute faces
    for(int i=0; i<5; i++){
        int top = 1;
        int bottom = 7;
        int offset = (i+1)%5;
        // top cap
        addFace(0, top+i, top+offset);
        // bottom cap
        addFace(6, bottom+i, bottom+offset);
        // middle ribbon
        addFace(bottom+i, top+offset, top+i);
        addFace(top+offset, bottom+offset, bottom+i);
    }

    // geodesic subdivisions :
    for(int i=0; i<n; i++){
        edges = new Edge[vertices.size()-1];
        int nb_triangles = indices.size()/3;
        for(int j=0; j<nb_triangles; j++)
        {
            int vid[3];
            for(int k=0; k<3; k++)
            {
                int idA = indices[j*3 + k];
                int idB = indices[j*3 + (k+1)%3];
                int a = idA < idB ? idA : idB;
                int b = idA > idB ? idA : idB;
                vid[k] = getEdge(a, b);
            }
            for(int k=0; k<3; k++)
                addFace(indices[j*3 + k], vid[k], vid[(k+2)%3]);
            addFace(vid[0], vid[1], vid[2]);
        }
        delete[](edges);
        indices.erase(indices.begin(), indices.begin()+nb_triangles*3);
    }
}

int Sphere::getEdge(int a, int b)
{
    Edge* current = edges+a;
    int vid = -1;
    while(vid == -1)
    {
        if(current->b == b)
            vid = current->vertex;
        else if(current->next == NULL)
        {
            // creating subdivision vertex
            Vertex v;
            Vertex v0 = vertices[a];
            Vertex v1 = vertices[b];
            v.position = glm::normalize((v0.position + v1.position)/2.f);
            v.normal = v.position;

            // u/v sphériques, cohérents sur toute la sphère sauf des artefacts au niveau des u==0
            float newU = (v.position.x < 0 ? 1.5f : 1.f) + atan(v.position.z/v.position.x)/(2*M_PI);
            float newV = acos(v.position.y)/M_PI;
            v.texCoord = glm::vec2(newU - floor(newU), newV);
            // alternative, u/v moyennés :
            //v.texcoord_ = (v0.texcoord_ + v1.texcoord_)/2.f;

            vid = vertices.size();
            addVertex(v);
            // inserting the new vertex in the edge collection
            if(current->b == -1)
            {
                current->vertex = vid;
                current->b = b;
            }
            else
                current->next = new Edge(b, vid);
        }
        else
            current = current->next;
    }
    return vid;
}

void Sphere::createVertex(float u, float v)
{
        Vertex vert;
        vert.position = glm::vec3(cos(u*2*M_PI)*sin(v*M_PI),
                                   cos(v*M_PI),
                                   sin(u*2*M_PI)*sin(v*M_PI));
        vert.normal   = vert.position;
        vert.texCoord = glm::vec2(u, v);
        addVertex(vert);
    }