#include "mesh.h"
#include "glassert.h"

#define BUFFER_OFFSET(i) ((char *)NULL + (i))

Mesh::~Mesh()
{
    destroyGL();
}

void Mesh::addVertex(const Vertex& v)
{
    if(!locked)
        vertices.push_back(v);
}

void Mesh::addFace(int i1, int i2, int i3)
{
    if(!locked)
    {
        indices.push_back(i1);
        indices.push_back(i2);
        indices.push_back(i3);
    }
}

void Mesh::initGL()
{
    if(locked)
        destroyGL();

    // create VAO
    glAssert(glGenVertexArrays(1, &vao));
    glAssert(glBindVertexArray(vao));

    // create VBOs
    glAssert(glGenBuffers(NB_BUFFERS, vbo));

    // init vertex vbo
    glAssert(glBindBuffer(GL_ARRAY_BUFFER, vbo[VERTEX_BUFFER]));
    glAssert(glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(Vertex), vertices.data(), GL_STATIC_DRAW));

    // position attribute
    glAssert(glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(0)));
    glAssert(glEnableVertexAttribArray(0));
    // normal attribute
    glAssert(glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(sizeof(glm::vec3))));
    glAssert(glEnableVertexAttribArray(1));
    // texCoord attribute
    glAssert(glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(2*sizeof(glm::vec3))));
    glAssert(glEnableVertexAttribArray(2));

    // init indices vbo
    glAssert(glBindBuffer(GL_ARRAY_BUFFER, vbo[INDICES_BUFFER]));
    glAssert(glBufferData(GL_ARRAY_BUFFER, indices.size() * sizeof(GLuint), indices.data(), GL_STATIC_DRAW));

    // unbind vao
    glAssert(glBindVertexArray(0));

    locked = true;
}

void Mesh::destroyGL()
{
    if(locked)
    {
        locked = false;
        glAssert(glDeleteVertexArrays(1, &vao));
        vao = 0;
        glAssert(glDeleteBuffers(2, vbo));
        vbo[0] = 0;
        vbo[1] = 0;
    }
}

void Mesh::draw()
{
    if(locked)
    {
        glAssert(glBindVertexArray(vao));
        glAssert(glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, indices.data()));
    }
}