#include "Shaders.h"

#ifdef _DEBUG

#include <gl/GLU.h>

PFNGLCREATESHADERPROGRAMEXTPROC glCreateShaderProgram = NULL;
PFNGLGETPROGRAMIVPROC glGetProgramiv = NULL;
PFNGLUSEPROGRAMPROC glUseProgram = NULL;
PFNGLGETPROGRAMINFOLOGPROC glGetProgramInfoLog = NULL;

void useProgram(GLhandleARB ah_Program)
{
	glUseProgram(ah_Program);
}

void initShaders()
{
	glGetProgramiv = (PFNGLGETPROGRAMIVPROC)myGetProcAddress("glGetProgramiv");
	glUseProgram = (PFNGLUSEPROGRAMPROC)myGetProcAddress("glUseProgram");
	glGetProgramInfoLog = (PFNGLGETPROGRAMINFOLOGPROC)myGetProcAddress("glGetProgramInfoLog");
	glCreateShaderProgram = (PFNGLCREATESHADERPROGRAMEXTPROC)myGetProcAddress("glCreateShaderProgramEXT");
	
	if (!(glCreateShaderProgram && glGetProgramiv && glUseProgram && glGetProgramInfoLog))
	{
		std::cerr <<  "Some shader functions are not available!" << std::endl;
	}
}

void PrintErrors()
{
	GLenum lr_Error = GL_NO_ERROR;
	int li_ErrorCount = 5;
	do
	{
		lr_Error = glGetError();
		if (lr_Error != GL_NO_ERROR)
		{
			li_ErrorCount--;
			char* ls_ErrorString = (char*)gluErrorString(lr_Error);
			if (ls_ErrorString != 0)
				std::cout << "OPENGL :: ERROR " << ls_ErrorString << std::endl;
		}
		if (li_ErrorCount == 0)
		{
			std::cout << "OPENGL :: ERROR Too many errors!" << std::endl;
			break;
		}
	} while (lr_Error != GL_NO_ERROR);
}

GLhandleARB createFragmentProgram(const char* as_FileName)
{
	GLhandleARB lh_Program = 0;

	char* ls_ShaderSource = textFileRead(as_FileName);
	if (ls_ShaderSource == NULL)
	{
		std::cerr << "Error reading file: " << as_FileName << std::endl;
		return lh_Program;
	}

	lh_Program = glCreateShaderProgram(GL_FRAGMENT_SHADER, ls_ShaderSource);
	printProgramInfoLog(lh_Program);

	return lh_Program;
}


char* textFileRead(const char* as_FileName) 
{
	FILE* lh_File;
	char* ls_Content = NULL;
	size_t li_Count = 0;

	if (as_FileName != NULL) 
	{
		fopen_s(&lh_File, as_FileName, "rt");

		if (lh_File != NULL) 
		{
			fseek(lh_File, 0, SEEK_END);
			li_Count = ftell(lh_File);
			rewind(lh_File);

			if (li_Count > 0) 
			{
				ls_Content = (char*) malloc(sizeof(char) * (li_Count + 1));
				li_Count = fread(ls_Content, sizeof(char), li_Count, lh_File);
				ls_Content[li_Count] = '\0';
			}

			fclose(lh_File);
		}
	}

	return ls_Content;
}

void printProgramInfoLog(GLhandleARB ah_Program)
{
	int li_InfologLength = 0;
	int li_CharsWritten = 0;
	char* ls_InfoLog;

	glGetProgramiv(ah_Program, GL_INFO_LOG_LENGTH, &li_InfologLength);

	if (li_InfologLength > 0)
	{
		ls_InfoLog = (char *)malloc(li_InfologLength);

		glGetProgramInfoLog(ah_Program, li_InfologLength, &li_CharsWritten, ls_InfoLog);

		std::cerr << ls_InfoLog << std::endl;
		free(ls_InfoLog);
	}
}

#endif