//! This example shows how you might use an `Indexmap` in OpenGL.

#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]

extern crate gl;
use gl::types::*;

extern crate glutin;
use glutin::*;

extern crate retro_pixel;
use retro_pixel::palettes::NES_PALETTE;
use retro_pixel::*;

// std
use std::collections::HashSet;
use std::ffi::CString;
use std::mem::{size_of, size_of_val};
use std::ptr::null;

fn main() {
  unsafe {
    let nes_width = 256u32;
    let nes_height = 240u32;
    let default_upscale = 3;
    let (start_width, start_height) = (nes_width * default_upscale, nes_height * default_upscale);

    // Window and OpenGL setup
    let mut events_loop = glutin::EventsLoop::new();
    let window_builder = glutin::WindowBuilder::new()
      .with_dimensions(start_width, start_height)
      .with_title("Indexmap Demo (Use arrow keys to move)");
    let context = glutin::ContextBuilder::new()
      .with_gl(GlRequest::Specific(Api::OpenGl, (3, 3)))
      .with_gl_profile(GlProfile::Core)
      .with_vsync(true);
    let window = glutin::GlWindow::new(window_builder, context, &events_loop)
      .map_err(|e| eprintln!("==Window Creation Error==\n{}", e))
      .unwrap();
    window.make_current().expect("Could not make the OpenGL context current");
    window.set_position(100, 15);
    gl::load_with(|symbol| window.get_proc_address(symbol) as *const _);
    gl::Viewport(0, 0, start_width as i32, start_height as i32);
    gl::ClearColor(0.1, 0.1, 0.1, 1.0);

    // get our shader program ready
    let shader_program = ready_program(VERT_SRC, FRAG_SRC).map_err(|s| eprintln!("{}", s)).unwrap();
    shader_program.use_program();

    let vertices: [f32; 12] = [-1.0, -1.0, -1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, -1.0, -1.0, -1.0];

    // Vertex Array Object
    let mut vao = 0;
    gl::GenVertexArrays(1, &mut vao);
    gl::BindVertexArray(vao);

    // Vertex buffer object
    let mut vbo = 0;
    gl::GenBuffers(1, &mut vbo);
    gl::BindBuffer(gl::ARRAY_BUFFER, vbo);
    gl::BufferData(
      gl::ARRAY_BUFFER,
      size_of_val(&vertices) as GLsizeiptr,
      vertices.as_ptr() as *const _,
      gl::STATIC_DRAW,
    );

    // Position attribute
    #[allow(non_snake_case)]
    let vPositionNDC: GLuint = 0;
    let vertex_stride: GLint = (size_of::<GLfloat>() * 2) as GLint;
    gl::VertexAttribPointer(vPositionNDC, 2, gl::FLOAT, gl::FALSE, vertex_stride, null());
    gl::EnableVertexAttribArray(vPositionNDC);

    // The Palette Texture
    let mut nes_palette_texture = 0;
    gl::GenTextures(1, &mut nes_palette_texture);
    gl::ActiveTexture(gl::TEXTURE0);
    let palette_texture_loc = shader_program.get_uniform_location("palette_texture").unwrap();
    gl::Uniform1i(palette_texture_loc, 0);
    gl::BindTexture(gl::TEXTURE_1D, nes_palette_texture);
    gl::TexParameteri(gl::TEXTURE_1D, gl::TEXTURE_WRAP_S, gl::REPEAT as i32);
    gl::TexParameteri(gl::TEXTURE_1D, gl::TEXTURE_WRAP_T, gl::REPEAT as i32);
    gl::TexParameteri(gl::TEXTURE_1D, gl::TEXTURE_MIN_FILTER, gl::NEAREST as i32);
    gl::TexParameteri(gl::TEXTURE_1D, gl::TEXTURE_MAG_FILTER, gl::NEAREST as i32);
    // immediately upload the NES palette texture, it never changes.
    gl::TexImage1D(
      gl::TEXTURE_1D,
      0,
      gl::RGBA as i32,
      NES_PALETTE.len() as i32,
      0,
      gl::RGBA,
      gl::UNSIGNED_BYTE,
      NES_PALETTE.as_ptr() as *const _,
    );
    gl::GenerateMipmap(gl::TEXTURE_1D);

    // The Indexmap Texture
    let mut indexmap_texture = 0;
    gl::GenTextures(1, &mut indexmap_texture);
    gl::ActiveTexture(gl::TEXTURE1);
    shader_program
      .get_uniform_location("indexmap_texture")
      .map(|loc| gl::Uniform1i(loc, 1))
      .ok();
    gl::BindTexture(gl::TEXTURE_2D, indexmap_texture);
    gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_WRAP_S, gl::CLAMP_TO_EDGE as i32);
    gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_WRAP_T, gl::CLAMP_TO_EDGE as i32);
    gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MIN_FILTER, gl::NEAREST as i32);
    gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MAG_FILTER, gl::NEAREST as i32);
    // hold off on uploading the indexmap texture, it changes from frame to frame.

    // Main loop
    let mut alien = load_alien_data();
    let mut indexmap = VecImage::new(nes_width as usize, nes_height as usize);
    let mut alien_position: (isize, isize) = (0, 0);
    let mut held_keys = HashSet::new();
    let mut running = true;
    while running {
      // Handle Input
      events_loop.poll_events(|event| match event {
        Event::WindowEvent { event: win_event, .. } => match win_event {
          WindowEvent::Resized(_, _) => {
            window.get_inner_size().map(|(px, py)| {
              println!("RESIZING: ({},{})", px, py);
              gl::Viewport(0, 0, px as i32, py as i32);
            });
          }
          WindowEvent::CloseRequested
          | WindowEvent::KeyboardInput {
            input:
              KeyboardInput {
                state: ElementState::Pressed,
                virtual_keycode: Some(VirtualKeyCode::Escape),
                ..
              },
            ..
          } => {
            running = false;
          }
          WindowEvent::KeyboardInput {
            input:
              KeyboardInput {
                state: ElementState::Pressed,
                virtual_keycode: Some(key),
                ..
              },
            ..
          } => {
            held_keys.insert(key);
            match key {
              VirtualKeyCode::F1 => {
                window.set_inner_size(nes_width, nes_height);
              }
              VirtualKeyCode::F2 => {
                window.set_inner_size(nes_width * 2, nes_height * 2);
              }
              VirtualKeyCode::F3 => {
                window.set_inner_size(nes_width * 3, nes_height * 3);
              }
              VirtualKeyCode::F4 => {
                window.set_inner_size(nes_width * 4, nes_height * 4);
              }
              VirtualKeyCode::Return => {
                println!("Start");
              }
              VirtualKeyCode::RShift => {
                println!("Select");
              }
              _ => {}
            }
          }
          WindowEvent::KeyboardInput {
            input:
              KeyboardInput {
                state: ElementState::Released,
                virtual_keycode: Some(key),
                ..
              },
            ..
          } => {
            held_keys.remove(&key);
          }
          _ => {}
        },
        _ => {}
      });
      for &key in held_keys.iter() {
        match key {
          VirtualKeyCode::Up => alien_position.1 += 1,
          VirtualKeyCode::Down => alien_position.1 -= 1,
          VirtualKeyCode::Left => alien_position.0 -= 1,
          VirtualKeyCode::Right => alien_position.0 += 1,
          VirtualKeyCode::X => {
            alien.inplace_counterclockwise90_square();
            alien.inplace_counterclockwise90_square();
            alien.inplace_counterclockwise90_square();
          }
          VirtualKeyCode::Z => {
            alien.inplace_counterclockwise90_square();
          }
          _ => {}
        }
      }

      // indexmap rendering
      indexmap.set_all(0x30);
      indexmap.direct_copy(&alien, alien_position);
      indexmap[(8, 8)] = 0x1D;

      // upload the latest texture data, we pretend it's all red
      gl::PixelStorei(gl::UNPACK_ALIGNMENT, 1);
      gl::TexImage2D(
        gl::TEXTURE_2D,
        0,
        gl::RED as i32,
        indexmap.width() as i32,
        indexmap.height() as i32,
        0,
        gl::RED,
        gl::UNSIGNED_BYTE,
        indexmap.as_ptr() as *const _,
      );
      gl::GenerateMipmap(gl::TEXTURE_2D);

      // Draw
      gl::Clear(gl::COLOR_BUFFER_BIT);
      gl::DrawArrays(gl::TRIANGLES, 0, 6);

      // Flip
      window.swap_buffers().unwrap();

      // Error check
      loop {
        match gl::GetError() {
          gl::NO_ERROR => break,
          gl::INVALID_ENUM => eprintln!("ERR: InvalidEnum"),
          gl::INVALID_VALUE => eprintln!("ERR: InvalidValue"),
          gl::INVALID_OPERATION => eprintln!("ERR: InvalidOperation"),
          gl::INVALID_FRAMEBUFFER_OPERATION => eprintln!("ERR: InvalidFramebufferOperation"),
          gl::OUT_OF_MEMORY => eprintln!("ERR: OutOfMemory"),
          gl::STACK_UNDERFLOW => eprintln!("ERR: StackUnderflow"),
          gl::STACK_OVERFLOW => eprintln!("ERR: StackOverflow"),
          e => eprintln!("ERR: Unknown: {}", e),
        };
        let _break_point = 5;
      }
    }
  }
}

fn load_alien_data() -> VecImage<u8> {
  let mut im = VecImage::new(8, 8);
  let (white, red, green, blue, other_blue) = (0x30, 0x05, 0x1A, 0x02, 0x2C);
  im.set_all(white);
  // Some eyes
  im[(3, 5)] = blue;
  im[(4, 5)] = other_blue;
  im[(5, 5)] = blue;
  // a body
  for &p in [
    (1, 4),
    (1, 5),
    (2, 4),
    (2, 5),
    (2, 6),
    (3, 3),
    (3, 4),
    (3, 6),
    (4, 4),
    (4, 6),
    (5, 3),
    (5, 4),
    (5, 6),
    (6, 4),
    (6, 5),
    (6, 6),
  ].iter()
  {
    im[p] = green;
  }
  // some feet
  im[(2, 1)] = red;
  im[(2, 2)] = red;
  im[(5, 1)] = red;
  im[(5, 2)] = red;

  im.upscale(2)
}

//
// SHADER STUFF
//

static VERT_SRC: &'static str = "#version 330 core
layout (location = 0) in vec2 vPositionNDC;

out vec2 screen_pixel_position;

void main()
{
  gl_Position = vec4(vPositionNDC, 1.0, 1.0);
  screen_pixel_position = vPositionNDC;
}";

static FRAG_SRC: &'static str = "#version 330 core
in vec2 screen_pixel_position;

uniform sampler2D indexmap_texture;
uniform sampler1D palette_texture;

out vec4 FragColor;

void main()
{
  vec2 indexmap_position = (screen_pixel_position + 1.0) / 2.0;
  
  // the texture upload turns 0-255 into 0.0 to 1.0, so reverse that
  float index_value = texture(indexmap_texture, indexmap_position).r * 255.0;

  // turn the Xth index (out of 64 NES colors) into a 0.0-1.0 texture position
  float index_pixel = index_value / 64.0;

  FragColor = texture(palette_texture, index_pixel);
}";

//
// SUPPORT CODE BEGINS HERE
//

/// Makes ready a program from two source strings.
///
/// Will attempt to make a complete shader program using the two source strings
/// provided as the vertex shader source and fragment shader source. If there's
/// an error at any point in the process you get that error message back
/// instead.
pub fn ready_program<VS, FS>(vert: VS, frag: FS) -> Result<ManagedProgram, String>
where
  VS: AsRef<str>,
  FS: AsRef<str>,
{
  // Load the vertex shader
  let mut vertex_shader = ManagedShader::create_shader(gl::VERTEX_SHADER)?;
  vertex_shader.shader_source(vert)?;
  vertex_shader.compile_shader();
  if !vertex_shader.get_compile_status() {
    return Err(format!(">>Vertex Shader Error:\n{}", vertex_shader.get_shader_info_log()));
  }

  // Load the fragment shader
  let mut fragment_shader = ManagedShader::create_shader(gl::FRAGMENT_SHADER)?;
  fragment_shader.shader_source(frag)?;
  fragment_shader.compile_shader();
  if !fragment_shader.get_compile_status() {
    return Err(format!(">>Fragment Shader Error:\n{}", fragment_shader.get_shader_info_log()));
  }

  // Link the program together
  let mut shader_program = ManagedProgram::create_program()?;
  shader_program.attach_shader(&vertex_shader);
  shader_program.attach_shader(&fragment_shader);
  shader_program.link_program();
  if !shader_program.get_link_status() {
    return Err(format!(">>Program Link Error:\n{}", shader_program.get_program_info_log()));
  }

  Ok(shader_program)
}

/// A newtype around a program name that deletes itself when dropped.
#[derive(Debug, PartialEq, Eq)]
pub struct ManagedProgram(GLuint);

impl ManagedProgram {
  /// Attempts to creates a new `ManagedProgram`.
  ///
  /// See [glCreateProgram](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glCreateProgram.xhtml)
  pub fn create_program() -> Result<ManagedProgram, String> {
    unsafe {
      let name = gl::CreateProgram();
      if name > 0 {
        Ok(ManagedProgram(name))
      } else {
        Err("Problem creating the program.".to_string())
      }
    }
  }

  /// Returns the program name held by this `ManagedShader`, in case you want
  /// to do something with it that this library doesn't cover.
  pub fn get_program_name(&self) -> GLuint {
    self.0
  }

  /// Attaches the given `ManagedShader` to this program.
  ///
  /// See [glAttachShader](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glAttachShader.xhtml)
  pub fn attach_shader(&mut self, shader: &ManagedShader) {
    unsafe {
      gl::AttachShader(self.0, shader.0);
    }
  }

  /// Links the program shader stages together.
  ///
  /// See [glLinkProgram](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glLinkProgram.xhtml)
  pub fn link_program(&mut self) {
    unsafe {
      gl::LinkProgram(self.0);
    }
  }

  /// Returns `true` if the last link operation of this program was successful, and `false` otherwise.
  ///
  /// See [glGetProgramiv](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGetProgram.xhtml)
  pub fn get_link_status(&self) -> bool {
    unsafe {
      let mut param = 0;
      gl::GetProgramiv(self.0, gl::LINK_STATUS, &mut param);
      param == GLint::from(gl::TRUE)
    }
  }

  /// Gets the info log of this program.
  ///
  /// See [glGetProgramInfoLog](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGetProgramInfoLog.xhtml)
  pub fn get_program_info_log(&self) -> String {
    unsafe {
      // How many bytes will the info log be? Including the null byte.
      let mut info_log_length: GLint = 0;
      gl::GetProgramiv(self.0, gl::INFO_LOG_LENGTH, &mut info_log_length);
      if info_log_length > 0 {
        // If there is an info log, get it.
        let mut info_log: Vec<u8> = Vec::with_capacity(info_log_length as usize);
        let mut info_log_char_count: GLsizei = 0;
        gl::GetProgramInfoLog(
          self.0,
          info_log_length as GLsizei,
          &mut info_log_char_count as *mut GLsizei,
          info_log.as_mut_ptr() as *mut GLchar,
        );
        info_log.set_len(info_log_char_count as usize);
        debug_assert!(info_log_char_count == info_log_length - 1);
        String::from_utf8_lossy(&info_log).to_string()
      } else {
        // If there's no info log, return the empty string.
        "".to_string()
      }
    }
  }

  /// Installs the program object as part of the current rendering state.
  ///
  /// See [glUseProgram](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glUseProgram.xhtml)
  pub fn use_program(&self) {
    // This is an IO/Global Affecting operation, but conceptually we're not
    // affecting the `ManagedProgram` _itself_, so we'll only require &T not
    // &mut T.
    unsafe {
      gl::UseProgram(self.0);
    }
  }

  /// Obtains the location of the uniform named within this program. The
  /// location returned remains valid until you re-link the program.
  ///
  /// See
  /// [glGetUniformLocation](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGetUniformLocation.xhtml)
  pub fn get_uniform_location<S: AsRef<str>>(&self, name: S) -> Result<GLint, String> {
    unsafe {
      match CString::new(name.as_ref()) {
        Ok(name_c) => match gl::GetUniformLocation(self.0, name_c.as_ptr()) {
          -1 => Err(format!("Could not find the specified location: {:?}", name.as_ref())),
          out => Ok(out),
        },
        Err(_) => Err("get_uniform_location: Could not convert the input to a CString.".to_string()),
      }
    }
  }
}

impl Drop for ManagedProgram {
  /// A `ManagedShader` calls
  /// [glDeleteProgram](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glDeleteProgram.xhtml)
  /// on itself when dropped.
  fn drop(&mut self) {
    unsafe {
      if gl::IsProgram(self.0) == gl::TRUE {
        gl::DeleteProgram(self.0);
      }
    }
  }
}

/// A newtype around a shader name that will mark itself for deletion when
/// dropped.
#[derive(Debug, PartialEq, Eq)]
pub struct ManagedShader(GLuint);

impl ManagedShader {
  /// Makes a new `ManagedShader` value of the `ShaderType` specified. This can
  /// potentially fail.
  ///
  /// The `String` returned in the `Err` case always simply reports that the
  /// attempt to create the shader (and the attempted type) failed, not anything
  /// more useful than that. It's only a `String` so that this function's `Result`
  /// type matches up with the `Result` type of the other functions related to
  /// shader program creation.
  ///
  /// See
  /// [glCreateShader](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glCreateShader.xhtml)
  pub fn create_shader(kind: GLenum) -> Result<ManagedShader, String> {
    unsafe {
      let shader_id = gl::CreateShader(kind);
      if shader_id > 0 {
        Ok(ManagedShader(shader_id))
      } else {
        Err("create_shader: could not create shader".to_string())
      }
    }
  }

  /// Gets the shader name held, in case you need to do something with a
  /// shader that isn't covered by this library.
  pub fn get_shader_name(&self) -> GLuint {
    self.0
  }

  /// Assigns the given string to be the shader's source, replacing the
  /// existing source, if any. This requires that the input string be
  /// converted into a `CString`, and so it fails if the input contains a null
  /// byte anywhere within it.
  ///
  /// See
  /// [glShaderSource](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glShaderSource.xhtml)
  pub fn shader_source<S: AsRef<str>>(&mut self, source: S) -> Result<(), String> {
    let source_c = CString::new(source.as_ref()).map_err(|_| "shader_source: Null byte found in source string.".to_string())?;
    unsafe { Ok(gl::ShaderSource(self.0, 1, &source_c.as_ptr(), null())) }
  }

  /// Instructs OpenGL to compile the shader.
  ///
  /// See
  /// [glCompileShader](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glCompileShader.xhtml)
  pub fn compile_shader(&mut self) {
    unsafe { gl::CompileShader(self.0) }
  }

  /// Returns `true` if the last compile on this shader was successful,
  /// `false` otherwise.
  ///
  /// See
  /// [glGetShaderiv](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGetShader.xhtml)
  pub fn get_compile_status(&self) -> bool {
    unsafe {
      let mut param = 0;
      gl::GetShaderiv(self.0, gl::COMPILE_STATUS, &mut param);
      param == GLint::from(gl::TRUE)
    }
  }

  /// Obtains the info log of this shader.
  ///
  /// See [glGetShaderInfoLog](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGetShaderInfoLog.xhtml)
  pub fn get_shader_info_log(&self) -> String {
    unsafe {
      // How many bytes will the info log be? Including the null byte.
      let mut info_log_length: GLint = 0;
      gl::GetShaderiv(self.0, gl::INFO_LOG_LENGTH, &mut info_log_length);
      if info_log_length > 0 {
        // If there is an info log, get it.
        let mut info_log: Vec<u8> = Vec::with_capacity(info_log_length as usize);
        let mut info_log_char_count: GLsizei = 0;
        gl::GetShaderInfoLog(
          self.0,
          info_log_length as GLsizei,
          &mut info_log_char_count as *mut GLsizei,
          info_log.as_mut_ptr() as *mut GLchar,
        );
        // This SHOULD trim away the null byte from the length of the
        // vector, assuming that OpenGL is behaving.
        info_log.set_len(info_log_length as usize);
        debug_assert!(info_log_char_count == info_log_length - 1);
        String::from_utf8_lossy(&info_log).to_string()
      } else {
        // If there's no info log, return the empty string.
        "".to_string()
      }
    }
  }
}

impl Drop for ManagedShader {
  /// Uses
  /// [glDeleteShader](https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glDeleteShader.xhtml)
  /// if the shader name held is a shader at the time of the drop.
  fn drop(&mut self) {
    unsafe {
      if gl::IsShader(self.0) == gl::TRUE {
        gl::DeleteShader(self.0)
      }
    }
  }
}