#include "vertexbuffer.h"
#include <cassert>
#include <climits>

VertexBuffer::VertexBuffer() : m_isValid(false) {
}

VertexBuffer::~VertexBuffer() {
    if(m_isValid) {
        glDeleteBuffers(1, &m_vertexVboId);
        glDeleteBuffers(1, &m_indexVboId);
    }
}

bool VertexBuffer::IsValid() const {
    return m_isValid;
}

void VertexBuffer::SetMeshData(VertexData* vd, int vertexCount) {
    assert(vertexCount <= USHRT_MAX);
    if(vertexCount == 0)
        return;
 
    if(!m_isValid) {
        glGenBuffers(1, &m_vertexVboId);
        glGenBuffers(1, &m_indexVboId);
    }

    m_vertexCount = vertexCount;

    glBindBuffer(GL_ARRAY_BUFFER, m_vertexVboId);
    glBufferData(GL_ARRAY_BUFFER, sizeof(VertexData) * vertexCount, vd, GL_STATIC_DRAW);

    // Pour le moment, generer le index array pour inclure tout les vertex, sans 
    // optimisation pour reduire le nombre de vertex envoyes a la carte
    // Idealement cet array devrait etre utiliser pour reutiliser les vertex et ainsi
    // sauver du temps en envoyant moins de donnees a la carte (il devrait etre construit
    // en meme temps que le buffer vd est rempli..)
    uint16_t* idx = new uint16_t[vertexCount];
    for(int i = 0; i < vertexCount; ++i)
        idx[i] = i;

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_indexVboId);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(uint16_t) * vertexCount, idx, GL_STATIC_DRAW);
    delete [] idx;

    m_isValid = true;
}

void VertexBuffer::Render() const {
    if(IsValid())
    {
        glClientActiveTexture(GL_TEXTURE0);
        glBindBuffer(GL_ARRAY_BUFFER, m_vertexVboId);
        glEnableClientState(GL_VERTEX_ARRAY);
        glVertexPointer(3, GL_FLOAT, sizeof(VertexData), (char*)0);
        glEnableClientState(GL_COLOR_ARRAY);
        glColorPointer(3, GL_FLOAT, sizeof(VertexData), (char*)12);
        glEnableClientState(GL_TEXTURE_COORD_ARRAY);
        glTexCoordPointer(2, GL_FLOAT, sizeof(VertexData), (char*)24);

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_indexVboId);
        glDrawElements(GL_QUADS, m_vertexCount, GL_UNSIGNED_SHORT, (char*)0);
        // TODO
        //glDrawRangeElements(GL_TRIANGLES, 0, 3, 3, GL_UNSIGNED_SHORT, (char*)0);

        glDisableClientState(GL_VERTEX_ARRAY);
        glDisableClientState(GL_COLOR_ARRAY);
        glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    }
}

int VertexBuffer::Count() const {
    return m_vertexCount;
}

void VertexBuffer::Flush() {
    if (m_isValid) {
        glDeleteBuffers(1, &m_vertexVboId);
        glDeleteBuffers(1, &m_indexVboId);
    }
    m_isValid = false;
}