#include "shaderprogram.h"
#include <fstream>
#include <GL/glew.h>
#include <GL/gl.h>

char *slurpFile(const char* filename)
{

    std::ifstream f(filename);
    f.seekg(0, std::ios::end);
    int len = f.tellg();
    f.seekg(0, std::ios::beg);

    char *data = new char[len + 1];
    f.read(data, len);
    f.close();

    data[len] = '\0';

    return data;
}

ShaderProgram::ShaderProgram(const char *vertPath, const char *fragPath)
{
    const GLchar *vdata = slurpFile(vertPath);
    vert = glCreateShader(GL_VERTEX_SHADER);

    glShaderSource(vert, 1, &vdata, NULL);
    glCompileShader(vert);

    GLint status;
    glGetShaderiv(vert, GL_COMPILE_STATUS, &status);

    if (status == GL_FALSE)
    {

        GLint infoLogLength;
        glGetShaderiv(vert, GL_INFO_LOG_LENGTH, &infoLogLength);

        GLchar *strInfoLog = new GLchar[infoLogLength + 1];
        glGetShaderInfoLog(vert, infoLogLength, NULL, strInfoLog);
        fprintf(stderr, "ERROR COMPILING VERTEX SHADER:\n%s", strInfoLog);
        delete [] strInfoLog;
    }

    delete [] vdata;

    const char *fdata = slurpFile(fragPath);

    frag = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(frag, 1, &fdata, NULL);
    glCompileShader(frag);
    glGetShaderiv(frag, GL_COMPILE_STATUS, &status);

    if (status == GL_FALSE)
    {

        GLint infoLogLength;
        glGetShaderiv(frag, GL_INFO_LOG_LENGTH, &infoLogLength);

        GLchar *strInfoLog = new GLchar[infoLogLength + 1];
        glGetShaderInfoLog(frag, infoLogLength, NULL, strInfoLog);
        fprintf(stderr, "ERROR COMPILING FRAGMENT SHADER:\n%s", strInfoLog);
        delete [] strInfoLog;
    }

    delete [] fdata;

    program = glCreateProgram();
    glAttachShader(program, vert);
    glAttachShader(program, frag);

    glLinkProgram(program);

    glGetProgramiv(program, GL_LINK_STATUS, &status);

    if (status == GL_FALSE)
    {
        GLint infoLogLength;
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &infoLogLength);
        GLchar *strInfoLog = new GLchar[infoLogLength + 1];
        glGetProgramInfoLog(program, infoLogLength, NULL, strInfoLog);
        fprintf(stderr, "LINKER FAILURE: %s\n", strInfoLog);
        delete[] strInfoLog;
    }
}

void ShaderProgram::begin()
{
    glUseProgram(program);
}

void ShaderProgram::end()
{
    glUseProgram(0);
}