/*

     File: GLUVertexArray.mm

 Abstract: 

 Utility toolkit for vao management and generation.

  Version: 1.2

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 */

#pragma mark -

#pragma mark Headers

// STL container types

#import <string>

#import <unordered_map>

// OpenGL core profile

#import <OpenGL/gl3.h>

// OpenGL vertices private type

#import "GLUVertices.h"

// OpenGL VAO header

#import "GLUVertexArray.h"

#pragma mark -

#pragma mark Private - Data Structures

namespace GLU

{

    // Name associated with an attribute or a binding point

    typedef std::string  Name;

    // Interleaved array

    struct VertexArray

    {

        GLuint mnVAO;

        GLuint mnBID;

        GLuint mnPID;

        GLuint mnCount;

        std::unordered_map<Name, GLuint>  m_Attributes;

    }; // GLUVertexArray

    typedef struct VertexArray  VertexArray;

} // GLU

#pragma mark -

#pragma mark Private - Utilities - Buffers

// Get a pointer into a buffer at an offset

static const GLchar *GLUBufferGetOffset(const GLsizeiptr nOffset)

{

    return((const GLchar *)nullptr + nOffset);

} // GLUBufferGetOffset

// Create a buffer

static GLuint GLUBufferCreate(const GLenum& rTarget,

                              const GLenum& rUsage,

                              const GLsizeiptr& rSize,

                              const GLfloat * const pArray)

{

    GLuint nBID = 0;

    glGenBuffers(1, &nBID);

    if(nBID)

    {

        glBindBuffer(rTarget, nBID);

        glBufferData(rTarget, rSize, pArray, rUsage);

        glBindBuffer(rTarget, 0);

    } // if

    return nBID;

} // GLUBufferCreate

#pragma mark -

#pragma mark Private - Utilities - Arrays

// Enable a generic vertex attribute

static BOOL GLUVertexAttributeArrayEnable(const GLint& rSize,

                                          const GLchar * const pName,

                                          const GLsizei& rStride,

                                          const GLvoid *pOffset,

                                          GLU::VertexArrayRef pVertexArray)

{

    BOOL bSuccess = pName != nullptr;

    if(bSuccess)

    {

        glUseProgram(pVertexArray->mnPID);

        const GLint nAttribLoc = glGetAttribLocation(pVertexArray->mnPID, pName);

        pVertexArray->m_Attributes[pName] = nAttribLoc;

        glVertexAttribPointer(nAttribLoc, rSize, GL_FLOAT, GL_FALSE, rStride, pOffset);

        glEnableVertexAttribArray(nAttribLoc);

    } // if

    return bSuccess;

} // GLUVertexAttributeArrayEnable

// Create an array buffer

static GLuint GLUArrayBufferCreate(const GLuint& rCount,

                                   const GLuint& rSPP,

                                   const GLfloat * const pArray)

{

    GLsizeiptr nSize = rSPP * rCount;

    return GLUBufferCreate(GL_ARRAY_BUFFER, GL_STATIC_DRAW, nSize, pArray);

} // GLUArrayBufferCreate

// Bind an array buffer

static void GLUArrayBufferBind(const GLuint nBID)

{

    glBindBuffer(GL_ARRAY_BUFFER,nBID);

} // GLUArrayBufferCreate

#pragma mark -

#pragma mark Private - Utilities - Vertices

// Get a float array from a STL vector representing a 2D object

static const GLfloat * GLUArrayGetPointer(const GLU::ArrayRef pArray)

{

    return((const GLfloat *)&pArray->m_Vertices[0]);

} // GLUArrayGetPointer

#pragma mark -

#pragma mark Private - Utilities - Vertex Array

// Create a buffer for vertices of a triangle fan

static void GLUVertexArrayEnable(const GLchar * const pPosition,

                                 const GLchar * const pTexCoord,

                                 const GLchar * const pColor,

                                 const GLU::ArrayRef pArray,

                                 GLU::VertexArrayRef pVertexArray)

{

    GLsizei nStride = sizeof(GLU::Vertex);

    pVertexArray->mnBID = GLUArrayBufferCreate(pVertexArray->mnCount, nStride, GLUArrayGetPointer(pArray));

    GLsizeiptr nOffsetTexCoord = sizeof(vector_float2);

    GLsizeiptr nOffsetColor    = 2 * nOffsetTexCoord;

    GLUArrayBufferBind(pVertexArray->mnBID);

    if(pPosition != nullptr)

    {

        GLUVertexAttributeArrayEnable(2, pPosition, nStride, GLUBufferGetOffset(0), pVertexArray);

    } // if

    if(pTexCoord != nullptr)

    {

        GLUVertexAttributeArrayEnable(2, pTexCoord, nStride, GLUBufferGetOffset(nOffsetTexCoord), pVertexArray);

    } // if

    if(pColor != nullptr)

    {

        GLUVertexAttributeArrayEnable(4, pColor, nStride, GLUBufferGetOffset(nOffsetColor), pVertexArray);

    } // if

} // GLUVertexArrayEnable

// Create a buffer for vertices of a triangle fan

static void GLUVertexArrayEnable(const GLchar * const pPosition,

                                 const GLchar * const pNormal,

                                 const GLchar * const pTexCoord,

                                 const GLchar * const pColor,

                                 const GLU::ArrayRef pArray,

                                 GLU::VertexArrayRef pVertexArray)

{

    GLsizei nStride = sizeof(GLU::Vertex);

    pVertexArray->mnBID = GLUArrayBufferCreate(pVertexArray->mnCount, nStride, GLUArrayGetPointer(pArray));

    GLsizeiptr nOffsetNormals  = sizeof(vector_float3);

    GLsizeiptr nOffsetTexCoord = 2 * nOffsetNormals;

    GLsizeiptr nOffsetColor    = 3 * nOffsetNormals;

    GLUArrayBufferBind(pVertexArray->mnBID);

    if(pPosition != nullptr)

    {

        GLUVertexAttributeArrayEnable(3, pPosition, nStride, GLUBufferGetOffset(0), pVertexArray);

    } // if

    if(pNormal != nullptr)

    {

        GLUVertexAttributeArrayEnable(3, pNormal, nStride, GLUBufferGetOffset(nOffsetNormals), pVertexArray);

    } // if

    if(pTexCoord != nullptr)

    {

        GLUVertexAttributeArrayEnable(3, pTexCoord, nStride, GLUBufferGetOffset(nOffsetTexCoord), pVertexArray);

    } // if

    if(pColor != nullptr)

    {

        GLUVertexAttributeArrayEnable(4, pColor, nStride, GLUBufferGetOffset(nOffsetColor), pVertexArray);

    } // if

} // GLUVertexArrayEnable

// Get the cached attribute location

static GLuint GLUVertexArrayGetAttribute(const GLU::Name &rName,

                                         GLU::VertexArrayRef pVertexArray)

{

    return pVertexArray->m_Attributes[rName];

} // GLUVertexArrayGetLocation

#pragma mark -

#pragma mark Public - Constructors

// Create a vao, representing a 2D object, using vertices, colors,

// and texture coordinates

GLU::VertexArrayRef GLU::VertexArrayCreate(const GLuint& rProgramID,

                                           const GLuint& rCount,

                                           const GLchar * const pPosition,

                                           const GLchar * const pTexCoord,

                                           const GLchar * const pColor,

                                           const GLU::ArrayRef pArray)

{

    GLU::VertexArrayRef pVertexArray = nullptr;

    if(rProgramID && pArray)

    {

        try

        {

            pVertexArray = new GLU::VertexArray;

            pVertexArray->mnPID   = rProgramID;

            pVertexArray->mnCount = rCount;

            glGenVertexArrays(1, &pVertexArray->mnVAO);

            if(pVertexArray->mnVAO)

            {

                glBindVertexArray(pVertexArray->mnVAO);

                GLUVertexArrayEnable(pPosition,

                                     pTexCoord,

                                     pColor,

                                     pArray,

                                     pVertexArray);

            } // if

        } // try

        catch(std::bad_alloc& ba)

        {

            NSLog(@">> ERROR: Failed allocating memory for CF mutable dictionary backing store: \"%s\"", ba.what());

        } // catch

    } // if

    return pVertexArray;

} // GLUVertexArrayCreate

// Create a vao, representing a 3D object, using vertices, normals,

// colors, and texture coordinates

GLU::VertexArrayRef GLU::VertexArrayCreate(const GLuint& rProgramID,

                                           const GLuint& rCount,

                                           const GLchar * const pPosition,

                                           const GLchar * const pNormal,

                                           const GLchar * const pTexCoord,

                                           const GLchar * const pColor,

                                           const GLU::ArrayRef pArray)

{

    GLU::VertexArrayRef pVertexArray = nullptr;

    if(rProgramID && pArray)

    {

        try

        {

            pVertexArray = new GLU::VertexArray;

            pVertexArray->mnPID   = rProgramID;

            pVertexArray->mnCount = rCount;

            glGenVertexArrays(1, &pVertexArray->mnVAO);

            if(pVertexArray->mnVAO)

            {

                glBindVertexArray(pVertexArray->mnVAO);

                GLUVertexArrayEnable(pPosition,

                                     pNormal,

                                     pTexCoord,

                                     pColor,

                                     pArray,

                                     pVertexArray);

            } // if

        } // try

        catch(std::bad_alloc& ba)

        {

            NSLog(@">> ERROR: Failed allocating memory for vertex array backing store: \"%s\"", ba.what());

            return;

        } // catch

    } // if

    return pVertexArray;

} // GLUVertexArrayCreate

#pragma mark -

#pragma mark Public - Destructor

// Delete the VAO opaque data reference

void GLU::VertexArrayDelete(GLU::VertexArrayRef pVertexArray)

{

    if(pVertexArray != nullptr)

    {

        pVertexArray->m_Attributes.clear();

        glDeleteBuffers(1, &pVertexArray->mnBID);

        glDeleteVertexArrays(1, &pVertexArray->mnVAO);

        delete pVertexArray;

    } // if

} // GLUVertexArrayDelete

#pragma mark -

#pragma mark Public - Accessors

// Get VBO id

const GLuint GLU::VertexArrayGetBuffer(const GLU::VertexArrayRef pVertexArray)

{

    return pVertexArray->mnBID;

} // GLUVertexArrayGetBuffer

// Get VAO id

const GLuint GLU::VertexArrayGetVAO(const GLU::VertexArrayRef pVertexArray)

{

    return pVertexArray->mnVAO;

} // GLUVertexArrayGetVAO

// Get the named attribute location

const GLuint GLU::VertexArrayGetLocation(const GLchar * const pName,

                                         const GLU::VertexArrayRef pVertexArray)

{

    return GLUVertexArrayGetAttribute(pName, pVertexArray);

} // GLUVertexArrayGetLocation

// Create VAO representing a quad

GLU::VertexArrayRef GLU::VertexArrayCreateQuad(const GLuint& rProgramID,

                                               const GLchar  * const pVertex,

                                               const GLchar  * const pColor,

                                               const GLfloat * const pColors,

                                               const GLchar  * const pTexCoords)

{

    GLU::VertexArrayRef pVertexArray = nullptr;

    GLU::ArrayRef pVertices = GLU::ArrayCreateQuad(nullptr, nullptr, pColors);

    if(pVertices != nullptr)

    {

        pVertexArray = GLU::VertexArrayCreate(rProgramID,

                                              4,

                                              pVertex,

                                              pTexCoords,

                                              pColor,

                                              pVertices);

        GLU::ArrayDelete(pVertices);

    } // if

    return pVertexArray;

} // GLUVertexArrayCreateQuad

// Create VAO representing a quad

GLU::VertexArrayRef GLU::VertexArrayCreateQuad(const GLuint& rProgramID,

                                               const GLchar  * const pColor,

                                               const GLfloat * const pColors,

                                               const GLchar  * const pTexCoords)

{

    GLU::VertexArrayRef pVertexArray = nullptr;

    GLU::ArrayRef pVertices = GLU::ArrayCreateQuad(nullptr, nullptr, pColors);

    if(pVertices != nullptr)

    {

        pVertexArray = GLU::VertexArrayCreate(rProgramID,

                                              4,

                                              nullptr,

                                              pTexCoords,

                                              pColor,

                                              pVertices);

        GLU::ArrayDelete(pVertices);

    } // if

    return pVertexArray;

} // GLUVertexArrayCreateQuad