#include "misc.h"
#include <stdio.h>

GLuint CreateBufferObject(GLenum bufferType, GLsizeiptr size, GLenum usage, void * data)
{
	GLuint object;
	glGenBuffers(1, &object);
	glBindBuffer(bufferType, object);
	glBufferData(bufferType, size, data, usage);
	glBindBuffer(bufferType, 0);

	return object;
}

char* LoadFileContent(const char *path) {
	FILE* pFile = fopen(path, "rb");
	if (pFile) {
		fseek(pFile, 0, SEEK_END);
		int nLen = ftell(pFile);
		char* buffer = nullptr;
		if (nLen != 0) {
			buffer = new char[nLen + 1];
			rewind(pFile);
			fread(buffer, nLen, 1, pFile);
			buffer[nLen] = '\0';
		}
		else {
			printf("load file %s fail, content is 0\n", path);
		}
		fclose(pFile);
		return buffer;
	}
	else {
		printf("open file %s fail\n", path);
	}
	fclose(pFile);
	return nullptr;
}

GLuint CompileShader(GLenum shaderType, const char * shaderPath)
{
	//创建shader
	GLuint shader = glCreateShader(shaderType);
	if (shader == 0) {
		printf("glCreateShader false\n");
		return 0;
	}
	//读取shader代码
	const char* shaderCode = LoadFileContent(shaderPath);
	if (shaderCode == nullptr) {
		printf("load shader code from file: %s false\n", shaderPath);
		return 0;
	}
	//把shader代码 从内存传到显存
	glShaderSource(shader, 1, &shaderCode, nullptr);
	glCompileShader(shader);

	GLint compileResult = GL_TRUE;
	glGetShaderiv(shader, GL_COMPILE_STATUS, &compileResult);
	if (compileResult == GL_FALSE) {
		char szLog[1024] = { 0 };
		GLsizei logLen = 0;//实际错误日志长度
		glGetShaderInfoLog(shader, 1024, &logLen, szLog);
		printf("Compile shader fail error log is : %s \n shader code :\n %s \n ", szLog, shaderCode);
		glDeleteShader(shader);
		return 0;
	}

	return shader;
}

/**
* 创建一个GPU程序
*/
GLuint CreateGPUProgram(const char* vsShaderPath, const char* fsShaderPath) {

	GLuint vsShader = CompileShader(GL_VERTEX_SHADER,vsShaderPath);
	GLuint fsShader = CompileShader(GL_FRAGMENT_SHADER,fsShaderPath);

	//创建program
	GLuint program = glCreateProgram();

	//绑定shader
	glAttachShader(program, vsShader);
	glAttachShader(program, fsShader);

	//连接
	glLinkProgram(program);

	//解绑shader
	glDetachShader(program, vsShader);
	glDetachShader(program, fsShader);

	//删除shader
	glDeleteShader(vsShader);
	glDeleteShader(fsShader);

	//检查错误
	GLint nResult;
	glGetProgramiv(program, GL_LINK_STATUS, &nResult);
	if (nResult == GL_FALSE) {
		char log[1024] = { 0 };
		GLsizei writed = 0;
		glGetProgramInfoLog(program, 1024, &writed, log);
		printf("Create CPU program fail error %s\n", log);
		glDeleteProgram(program);
		program = 0;
	}

	return program;
}