#include <windows.h>
#include <stdio.h>
#include "opengl.h"


// Program
PFNGLCREATEPROGRAMPROC glCreateProgram = NULL;
PFNGLDELETEPROGRAMPROC glDeleteProgram = NULL;
PFNGLUSEPROGRAMPROC glUseProgram = NULL;
PFNGLATTACHSHADERPROC glAttachShader = NULL;
PFNGLDETACHSHADERPROC glDetachShader = NULL;
PFNGLLINKPROGRAMPROC glLinkProgram = NULL;
PFNGLGETPROGRAMIVPROC glGetProgramiv = NULL;
PFNGLGETSHADERINFOLOGPROC glGetShaderInfoLog = NULL;
PFNGLGETUNIFORMLOCATIONPROC glGetUniformLocation = NULL;
PFNGLUNIFORM1IPROC glUniform1i = NULL;
PFNGLUNIFORM1IVPROC glUniform1iv = NULL;
PFNGLUNIFORM2IVPROC glUniform2iv = NULL;
PFNGLUNIFORM3IVPROC glUniform3iv = NULL;
PFNGLUNIFORM4IVPROC glUniform4iv = NULL;
PFNGLUNIFORM1FPROC glUniform1f = NULL;
PFNGLUNIFORM1FVPROC glUniform1fv = NULL;
PFNGLUNIFORM2FVPROC glUniform2fv = NULL;
PFNGLUNIFORM3FVPROC glUniform3fv = NULL;
PFNGLUNIFORM4FVPROC glUniform4fv = NULL;
PFNGLUNIFORM4FPROC glUniform4f = NULL;
PFNGLUNIFORMMATRIX4FVPROC glUniformMatrix4fv = NULL;
PFNGLGETATTRIBLOCATIONPROC glGetAttribLocation = NULL;
PFNGLVERTEXATTRIB1FPROC glVertexAttrib1f = NULL;
PFNGLVERTEXATTRIB1FVPROC glVertexAttrib1fv = NULL;
PFNGLVERTEXATTRIB2FVPROC glVertexAttrib2fv = NULL;
PFNGLVERTEXATTRIB3FVPROC glVertexAttrib3fv = NULL;
PFNGLVERTEXATTRIB4FVPROC glVertexAttrib4fv = NULL;
PFNGLENABLEVERTEXATTRIBARRAYPROC glEnableVertexAttribArray = NULL;
PFNGLDISABLEVERTEXATTRIBARRAYPROC glDisableVertexAttribArray = NULL;
PFNGLBINDATTRIBLOCATIONPROC glBindAttribLocation = NULL;
PFNGLGETACTIVEUNIFORMPROC glGetActiveUniform = NULL;

// Shader
PFNGLCREATESHADERPROC glCreateShader = NULL;
PFNGLDELETESHADERPROC glDeleteShader = NULL;
PFNGLSHADERSOURCEPROC glShaderSource = NULL;
PFNGLCOMPILESHADERPROC glCompileShader = NULL;
PFNGLGETSHADERIVPROC glGetShaderiv = NULL;

// VBO
PFNGLGENBUFFERSPROC glGenBuffers = NULL;
PFNGLBINDBUFFERPROC	glBindBuffer = NULL;
PFNGLBUFFERDATAPROC	glBufferData = NULL;
PFNGLVERTEXATTRIBPOINTERPROC glVertexAttribPointer = NULL;
PFNGLDELETEBUFFERSPROC glDeleteBuffers = NULL;

PFNGLGENBUFFERSARBPROC glGenBuffersARB = NULL;
PFNGLBINDBUFFERARBPROC glBindBufferARB = NULL;
PFNGLBUFFERDATAARBPROC glBufferDataARB = NULL;
PFNGLDELETEBUFFERSARBPROC glDeleteBuffersARB = NULL;
PFNGLMAPBUFFERARBPROC glMapBufferARB = NULL;
PFNGLUNMAPBUFFERARBPROC glUnmapBufferARB = NULL;

PFNGLACTIVETEXTUREARBPROC glActiveTexture = NULL;
PFNGLCLIENTACTIVETEXTUREPROC glClientActiveTexture = NULL;
PFNGLMULTITEXCOORD2FPROC glMultiTexCoord2f = NULL;

PFNGLGENFRAMEBUFFERSPROC glGenFramebuffers = NULL;
PFNGLBINDFRAMEBUFFERPROC glBindFramebuffer = NULL;
PFNGLFRAMEBUFFERTEXTURE2DPROC glFramebufferTexture2D = NULL;
PFNGLDRAWBUFFERSPROC glDrawBuffers = NULL;
PFNGLCHECKFRAMEBUFFERSTATUSPROC glCheckFramebufferStatus = NULL;
PFNGLDELETEFRAMEBUFFERSPROC glDeleteFramebuffers = NULL;

void OpenGL_Init()
{
    // Program
    glCreateProgram = (PFNGLCREATEPROGRAMPROC)wglGetProcAddress("glCreateProgram");
    glDeleteProgram = (PFNGLDELETEPROGRAMPROC)wglGetProcAddress("glDeleteProgram");
    glUseProgram = (PFNGLUSEPROGRAMPROC)wglGetProcAddress("glUseProgram");
    glAttachShader = (PFNGLATTACHSHADERPROC)wglGetProcAddress("glAttachShader");
    glDetachShader = (PFNGLDETACHSHADERPROC)wglGetProcAddress("glDetachShader");
    glLinkProgram = (PFNGLLINKPROGRAMPROC)wglGetProcAddress("glLinkProgram");
    glGetProgramiv = (PFNGLGETPROGRAMIVPROC)wglGetProcAddress("glGetProgramiv");
    glGetShaderInfoLog = (PFNGLGETSHADERINFOLOGPROC)wglGetProcAddress("glGetShaderInfoLog");
    glGetUniformLocation = (PFNGLGETUNIFORMLOCATIONPROC)wglGetProcAddress("glGetUniformLocation");
    glUniform1i = (PFNGLUNIFORM1IPROC)wglGetProcAddress("glUniform1i");
    glUniform1iv = (PFNGLUNIFORM1IVPROC)wglGetProcAddress("glUniform1iv");
    glUniform2iv = (PFNGLUNIFORM2IVPROC)wglGetProcAddress("glUniform2iv");
    glUniform3iv = (PFNGLUNIFORM3IVPROC)wglGetProcAddress("glUniform3iv");
    glUniform4iv = (PFNGLUNIFORM4IVPROC)wglGetProcAddress("glUniform4iv");
    glUniform1f = (PFNGLUNIFORM1FPROC)wglGetProcAddress("glUniform1f");
    glUniform1fv = (PFNGLUNIFORM1FVPROC)wglGetProcAddress("glUniform1fv");
    glUniform2fv = (PFNGLUNIFORM2FVPROC)wglGetProcAddress("glUniform2fv");
    glUniform3fv = (PFNGLUNIFORM3FVPROC)wglGetProcAddress("glUniform3fv");
    glUniform4fv = (PFNGLUNIFORM4FVPROC)wglGetProcAddress("glUniform4fv");
    glUniform4f = (PFNGLUNIFORM4FPROC)wglGetProcAddress("glUniform4f");
    glUniformMatrix4fv = (PFNGLUNIFORMMATRIX4FVPROC)wglGetProcAddress("glUniformMatrix4fv");
    glGetAttribLocation = (PFNGLGETATTRIBLOCATIONPROC)wglGetProcAddress("glGetAttribLocation");
    glVertexAttrib1f = (PFNGLVERTEXATTRIB1FPROC)wglGetProcAddress("glVertexAttrib1f");
    glVertexAttrib1fv = (PFNGLVERTEXATTRIB1FVPROC)wglGetProcAddress("glVertexAttrib1fv");
    glVertexAttrib2fv = (PFNGLVERTEXATTRIB2FVPROC)wglGetProcAddress("glVertexAttrib2fv");
    glVertexAttrib3fv = (PFNGLVERTEXATTRIB3FVPROC)wglGetProcAddress("glVertexAttrib3fv");
    glVertexAttrib4fv = (PFNGLVERTEXATTRIB4FVPROC)wglGetProcAddress("glVertexAttrib4fv");
    glEnableVertexAttribArray = (PFNGLENABLEVERTEXATTRIBARRAYPROC)wglGetProcAddress("glEnableVertexAttribArray");
    glBindAttribLocation = (PFNGLBINDATTRIBLOCATIONPROC)wglGetProcAddress("glBindAttribLocation");

    // Shader
    glCreateShader = (PFNGLCREATESHADERPROC)wglGetProcAddress("glCreateShader");
    glDeleteShader = (PFNGLDELETESHADERPROC)wglGetProcAddress("glDeleteShader");
    glShaderSource = (PFNGLSHADERSOURCEPROC)wglGetProcAddress("glShaderSource");
    glCompileShader = (PFNGLCOMPILESHADERPROC)wglGetProcAddress("glCompileShader");
    glGetShaderiv = (PFNGLGETSHADERIVPROC)wglGetProcAddress("glGetShaderiv");

    // VBO
    glGenBuffers = (PFNGLGENBUFFERSPROC)wglGetProcAddress("glGenBuffers");
    glBindBuffer = (PFNGLBINDBUFFERPROC)wglGetProcAddress("glBindBuffer");
    glBufferData = (PFNGLBUFFERDATAPROC)wglGetProcAddress("glBufferData");
    glVertexAttribPointer = (PFNGLVERTEXATTRIBPOINTERPROC)wglGetProcAddress("glVertexAttribPointer");
    glDeleteBuffers = (PFNGLDELETEBUFFERSPROC)wglGetProcAddress("glDeleteBuffers");

    glGenBuffersARB = (PFNGLGENBUFFERSARBPROC)wglGetProcAddress("glGenBuffersARB");
    glBindBufferARB = (PFNGLBINDBUFFERARBPROC)wglGetProcAddress("glBindBufferARB");
    glBufferDataARB = (PFNGLBUFFERDATAARBPROC)wglGetProcAddress("glBufferDataARB");
    glDeleteBuffersARB = (PFNGLDELETEBUFFERSARBPROC)wglGetProcAddress("glDeleteBuffersARB");
    glMapBufferARB = (PFNGLMAPBUFFERARBPROC)wglGetProcAddress("glMapBufferARB");
    glUnmapBufferARB = (PFNGLUNMAPBUFFERARBPROC)wglGetProcAddress("glUnmapBufferARB");

    glActiveTexture = (PFNGLACTIVETEXTUREARBPROC)wglGetProcAddress("glActiveTexture");
    glClientActiveTexture = (PFNGLCLIENTACTIVETEXTUREPROC)wglGetProcAddress("glClientActiveTexture");
    glMultiTexCoord2f = (PFNGLMULTITEXCOORD2FPROC)wglGetProcAddress("glMultiTexCoord2f");

    glGenFramebuffers = (PFNGLGENFRAMEBUFFERSPROC)wglGetProcAddress("glGenFramebuffers");
    glBindFramebuffer = (PFNGLBINDFRAMEBUFFERPROC)wglGetProcAddress("glBindFramebuffer");
    glFramebufferTexture2D = (PFNGLFRAMEBUFFERTEXTURE2DPROC)wglGetProcAddress("glFramebufferTexture2D");
    glDrawBuffers = (PFNGLDRAWBUFFERSPROC)wglGetProcAddress("glDrawBuffers");
    glCheckFramebufferStatus = (PFNGLCHECKFRAMEBUFFERSTATUSPROC)wglGetProcAddress("glCheckFramebufferStatus");
    glDeleteFramebuffers = (PFNGLDELETEFRAMEBUFFERSPROC)wglGetProcAddress("glDeleteFramebuffers");
}

BOOL OpenGL_ExtExists(char *ext)
{
    char *glext = (char *)glGetString(GL_EXTENSIONS);
    if (glext)
    {
        if (strstr(glext, ext))
            return TRUE;
    }
    return FALSE;
}

GLuint OpenGL_BuildProgram(const GLchar *vertSource, const GLchar *fragSource)
{
    if (!glCreateShader || !glShaderSource || !glCompileShader || !glCreateProgram ||
        !glAttachShader || !glLinkProgram || !glUseProgram || !glDetachShader)
        return 0;

    GLuint vertShader = glCreateShader(GL_VERTEX_SHADER);
    GLuint fragShader = glCreateShader(GL_FRAGMENT_SHADER);

    if (!vertShader || !fragShader)
        return 0;

    const GLchar *vertSrc[2] = { "#define VERTEX\n", vertSource };
    const GLchar *fragSrc[2] = { "#define FRAGMENT\n", fragSource };

    glShaderSource(vertShader, 2, vertSrc, NULL);
    glShaderSource(fragShader, 2, fragSrc, NULL);

    GLint isCompiled = 0;

    glCompileShader(vertShader);
    if (glGetShaderiv)
    {
        glGetShaderiv(vertShader, GL_COMPILE_STATUS, &isCompiled);
        if (isCompiled == GL_FALSE)
        {
            if (glDeleteShader)
                glDeleteShader(vertShader);

            return 0;
        }
    }

    glCompileShader(fragShader);
    if (glGetShaderiv)
    {
        glGetShaderiv(fragShader, GL_COMPILE_STATUS, &isCompiled);
        if (isCompiled == GL_FALSE)
        {
            if (glDeleteShader)
                glDeleteShader(fragShader);

            return 0;
        }
    }

    GLuint program = glCreateProgram();
    if (program)
    {
        glAttachShader(program, vertShader);
        glAttachShader(program, fragShader);

        glLinkProgram(program);

        glDetachShader(program, vertShader);
        glDetachShader(program, fragShader);
        glDeleteShader(vertShader);
        glDeleteShader(fragShader);

        if (glGetProgramiv)
        {
            GLint isLinked = 0;
            glGetProgramiv(program, GL_LINK_STATUS, &isLinked);
            if (isLinked == GL_FALSE)
            {
                if (glDeleteProgram)
                    glDeleteProgram(program);

                return 0;
            }
        }
    }

    return program;
}

GLuint OpenGL_BuildProgramFromFile(const char *filePath)
{
    GLuint program = 0;

    FILE *file = fopen(filePath, "rb");
    if (file)
    {
        fseek(file, 0, SEEK_END);
        long fileSize = ftell(file);
        fseek(file, 0, SEEK_SET);

        char *source = malloc(fileSize + 1);
        if (source)
        {
            fread(source, fileSize, 1, file);
            fclose(file);

            source[fileSize] = 0;

            program = OpenGL_BuildProgram(source, source);
            free(source);
        }
    }

    return program;
}