#include "shader.h"
#include <glew/glew.h>
#include <QFile>
#include <QTextStream>
#include <iostream>
#include "glassert.h"

const std::string Shader::DEFAULT_VERT = "#version 330\nlayout(location = 0)in vec3 inPosition;\nvoid main(){gl_Position = vec4(inPosition, 1.0);}";
const std::string Shader::DEFAULT_FRAG = "#version 330\nlayout(location = 0)out vec4 outColor;\nvoid main(){outColor = vec4(1, 0, 0, 1);}";

Shader::Shader(const QString &vertFilename, const QString &fragFilename)
{
    program = glAssert(glCreateProgram());

    GLuint vertexShaderId = createShader(vertFilename, GL_VERTEX_SHADER);
    GLuint fragmentShaderId = createShader(fragFilename, GL_FRAGMENT_SHADER);

    glAssert(glAttachShader(program, vertexShaderId));
    glAssert(glAttachShader(program, fragmentShaderId));

    glAssert(glBindAttribLocation(program, 0, "inPosition"));
    glAssert(glBindAttribLocation(program, 1, "inNormal"));
    glAssert(glBindAttribLocation(program, 2, "inTexCoord"));

    glAssert(glLinkProgram(program));

    // check errors
    GLint linked;
    glAssert(glGetProgramiv(program, GL_LINK_STATUS, &linked));
    if (!linked) {
        std::cerr << "Program not linked" << std::endl;
        printProgramInfoLog(program);
        program = 0;
    }
    else
        std::cout << "Shader successfully compiled" << std::endl;

    glAssert(glDetachShader(program, vertexShaderId));
    glAssert(glDetachShader(program, fragmentShaderId));
    glAssert(glDeleteShader(vertexShaderId));
    glAssert(glDeleteShader(fragmentShaderId));
}

Shader::~Shader()
{
    bool ok;
    glAssert(ok = glIsProgram(program))
    if(ok)
        glAssert(glDeleteProgram(program));
}


QString Shader::fileToString(QString filename)
{
    QFile f(filename);
    if(!f.open(QFile::ReadOnly | QFile::Text))
        return NULL;
    QTextStream in(&f);
    return in.readAll();
}

GLuint Shader::createShader(QString filename, GLenum shaderType)
{
    QString source = fileToString(filename);
    glAssert(GLuint shaderId = glCreateShader(shaderType));
    const GLchar *data = (const GLchar *)source.toStdString().c_str();
    glAssert(glShaderSource(shaderId, 1, &data, NULL));

    glAssert(glCompileShader(shaderId));

    // check errors
    GLint compiled;
    glAssert(glGetShaderiv(shaderId, GL_COMPILE_STATUS, &compiled));
    if (!compiled) {
        std::cerr << "[" << filename.toStdString() << "] Vertex shader not compiled : " << std::endl;
        printShaderInfoLog(shaderId);
        return 0;
    }
    else
        return shaderId;
}

void Shader::printShaderInfoLog(GLuint shaderId)
{
    int infoLogLen = 0;
    int charsWritten = 0;
    GLchar *infoLog;
    glAssert(glGetShaderiv(shaderId, GL_INFO_LOG_LENGTH, &infoLogLen));
    if (infoLogLen > 0) {
        infoLog = new GLchar[infoLogLen];
        glAssert(glGetShaderInfoLog(shaderId, infoLogLen, &charsWritten, infoLog));
        std::cerr << "InfoLog:" << std::endl << infoLog << std::endl;
        delete [] infoLog;
    }
}

void Shader::printProgramInfoLog(GLuint programId)
{
    int infoLogLen = 0;
    int charsWritten = 0;
    GLchar *infoLog;
    glAssert(glGetProgramiv(programId, GL_INFO_LOG_LENGTH, &infoLogLen));
    if (infoLogLen > 0) {
        infoLog = new GLchar[infoLogLen];
        glAssert(glGetProgramInfoLog(programId, infoLogLen, &charsWritten, infoLog));
        std::cerr << "InfoLog:" << std::endl << infoLog << std::endl;
        delete [] infoLog;
    }
}

GLuint Shader::getProgramId()
{
    return program;
}