// Fragment and vertex shaders code
static const GLchar* pszFragShader = "\
   precision mediump float;\
   varying vec4 v_Color;\
   void main (void)\
   {\
       gl_FragColor = v_Color;\
   }";

static const GLchar* pszVertShader = "\
   varying vec4  v_Color;\
   attribute vec4  a_Color;\
   attribute highp vec4  a_Position;\
   void main(void)\
   {\
       v_Color = a_Color;\
       gl_Position = a_Position;\
   }";

GLint myglfwGetShaderProgram(const char *vertex_shader_source, const char *fragment_shader_source) {
    enum Consts {INFOLOG_LEN = 512};
    GLchar infoLog[INFOLOG_LEN];
    GLint fragment_shader;
    GLint success;
    GLint vertex_shader;
    const char *pvertex_shader = vertex_shader_source;
    const char *pfragment_shader = fragment_shader_source;

    /* Vertex shader */
    vertex_shader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex_shader, 1, &pvertex_shader, NULL);
    glCompileShader(vertex_shader);
    glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(vertex_shader, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::VERTEX::COMPILATION_FAILED\n%s\n", infoLog);
    }

    /* Fragment shader */
    fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment_shader, 1, &pfragment_shader, NULL);
    glCompileShader(fragment_shader);
    glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(fragment_shader, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n%s\n", infoLog);
    }

    /* Link shaders */
    shader_program = glCreateProgram();
    glAttachShader(shader_program, vertex_shader);
    glAttachShader(shader_program, fragment_shader);
    glBindAttribLocation(shader_program, VERTEX_POS_INDX, "a_Position");
    glBindAttribLocation(shader_program, COLOR_POS_INDX, "a_Color");
    glLinkProgram(shader_program);
    glGetProgramiv(shader_program, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shader_program, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::PROGRAM::LINKING_FAILED\n%s\n", infoLog);
    }

    glEnableVertexAttribArray(VERTEX_POS_INDX);
    glEnableVertexAttribArray(COLOR_POS_INDX);

    glUseProgram(shader_program);

    glGenBuffers(1, &vbo_vertex);
    glGenBuffers(1, &vbo_color);

    glDeleteShader(vertex_shader);
    glDeleteShader(fragment_shader);
    return shader_program;
}

void DrawArrays(GLenum mode, GLint first, GLsizei count) {

    int vertexLocation = glGetAttribLocation(shader_program, "a_Position");
    int colorLocation = glGetAttribLocation(shader_program, "a_Color");

    glBindBuffer(GL_ARRAY_BUFFER, vbo_vertex);
    glBufferData(GL_ARRAY_BUFFER, (count + first) *
            (sizeof(GLfloat) * 3), vertices, GL_STATIC_DRAW);
    glVertexAttribPointer(vertexLocation, 3, GL_FLOAT, GL_FALSE, 0, 0);

    glBindBuffer(GL_ARRAY_BUFFER, vbo_color);
    glBufferData(GL_ARRAY_BUFFER, (count + first) *
            (sizeof(GLfloat) * 4), colors, GL_STATIC_DRAW);
    glVertexAttribPointer(colorLocation, 4, GL_FLOAT, GL_FALSE, 0, 0);

    glDrawArrays(mode, first, count);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
}