use gl::types::{GLboolean, GLchar, GLenum, GLfloat, GLint, GLsizeiptr, GLuint};
use safex::glx::*;
use safex::xlib::*;
use std::ffi::{c_void, CString};
use std::{mem, ptr};

// Vertex data
static VERTEX_DATA: [GLfloat; 6] = [0.0, 0.5, 0.5, -0.5, -0.5, -0.5];

// Shader sources
static VS_SRC: &'static str = "
#version 140
in vec2 position;
void main() {
    gl_Position = vec4(position, 0.0, 1.0);
}";

static FS_SRC: &'static str = "
#version 140
out vec4 out_color;
void main() {
    out_color = vec4(1.0, 1.0, 1.0, 1.0);
}";

fn compile_shader(src: &str, ty: GLenum) -> GLuint {
    let shader;
    unsafe {
        shader = gl::CreateShader(ty);
        // Attempt to compile the shader
        let c_str = CString::new(src.as_bytes()).unwrap();
        gl::ShaderSource(shader, 1, &c_str.as_ptr(), ptr::null());
        gl::CompileShader(shader);

        // Get the compile status
        let mut status = gl::FALSE as GLint;
        gl::GetShaderiv(shader, gl::COMPILE_STATUS, &mut status);

        // Fail on error
        if status != (gl::TRUE as GLint) {
            let mut len = 0;
            gl::GetShaderiv(shader, gl::INFO_LOG_LENGTH, &mut len);
            let mut buf = Vec::with_capacity(len as usize);
            buf.set_len((len as usize) - 1); // subtract 1 to skip the trailing null character
            gl::GetShaderInfoLog(
                shader,
                len,
                ptr::null_mut(),
                buf.as_mut_ptr() as *mut GLchar,
            );
            panic!(
                "{}",
                std::str::from_utf8(&buf)
                    .ok()
                    .expect("ShaderInfoLog not valid utf8")
            );
        }
    }
    shader
}

fn link_program(vs: GLuint, fs: GLuint) -> GLuint {
    unsafe {
        let program = gl::CreateProgram();
        gl::AttachShader(program, vs);
        gl::AttachShader(program, fs);
        gl::LinkProgram(program);
        // Get the link status
        let mut status = gl::FALSE as GLint;
        gl::GetProgramiv(program, gl::LINK_STATUS, &mut status);

        // Fail on error
        if status != (gl::TRUE as GLint) {
            let mut len: GLint = 0;
            gl::GetProgramiv(program, gl::INFO_LOG_LENGTH, &mut len);
            let mut buf = Vec::with_capacity(len as usize);
            buf.set_len((len as usize) - 1); // subtract 1 to skip the trailing null character
            gl::GetProgramInfoLog(
                program,
                len,
                ptr::null_mut(),
                buf.as_mut_ptr() as *mut GLchar,
            );
            panic!(
                "{}",
                std::str::from_utf8(&buf)
                    .ok()
                    .expect("ProgramInfoLog not valid utf8")
            );
        }
        program
    }
}

fn main() {
    let display = Display::open(None);
    let screen = Screen::default(&display);
    let vi = glx_choose_visual(
        &display,
        &mut [GLX_RGBA, GLX_DEPTH_SIZE, 24, GLX_DOUBLEBUFFER, GLX_NONE],
    )
    .unwrap();
    let window =
        Window::new_with_glx(&display, &screen, &vi, None, 0, 0, 200, 200, 1, 0, 0, &vi).unwrap();

    let glc = GLXContext::create(&display, &vi, None, gl::TRUE as i32);
    glx_make_current(&display, &window, &glc);

    gl::load_with(|string| glc.get_proc_address(string).unwrap() as *mut c_void);

    let vs = compile_shader(VS_SRC, gl::VERTEX_SHADER);
    let fs = compile_shader(FS_SRC, gl::FRAGMENT_SHADER);
    let program = link_program(vs, fs);

    let mut vao = 0;
    let mut vbo = 0;

    unsafe {
        // Create Vertex Array Object
        gl::GenVertexArrays(1, &mut vao);
        gl::BindVertexArray(vao);

        // Create a Vertex Buffer Object and copy the vertex data to it
        gl::GenBuffers(1, &mut vbo);
        gl::BindBuffer(gl::ARRAY_BUFFER, vbo);
        gl::BufferData(
            gl::ARRAY_BUFFER,
            (VERTEX_DATA.len() * mem::size_of::<GLfloat>()) as GLsizeiptr,
            mem::transmute(&VERTEX_DATA[0]),
            gl::STATIC_DRAW,
        );

        // Use shader program
        gl::UseProgram(program);
        gl::BindFragDataLocation(program, 0, CString::new("out_color").unwrap().as_ptr());

        // Specify the layout of the vertex data
        let pos_attr = gl::GetAttribLocation(program, CString::new("position").unwrap().as_ptr());
        gl::EnableVertexAttribArray(pos_attr as GLuint);
        gl::VertexAttribPointer(
            pos_attr as GLuint,
            2,
            gl::FLOAT,
            gl::FALSE as GLboolean,
            0,
            ptr::null(),
        );
    }

    window.map(&display);

    window.run(|event, control_flow| match event {
        WindowEvent::Expose => {
            unsafe {
                gl::Viewport(0, 0, 100, 100);
                gl::ClearColor(0.3, 0.3, 0.3, 1.0);
                gl::Clear(gl::COLOR_BUFFER_BIT);
                // Draw a triangle from the 3 vertices
                gl::DrawArrays(gl::TRIANGLES, 0, 3);
            }
            window.glx_swap_buffers();
        }
    })
}