//! Example of glyph_brush usage with raw OpenGL.
//!
//! Uses instanced rendering with 1 vertex per glyph referencing a 1 byte per pixel texture.
//!
//! Controls
//! * Scroll to size text.
//! * Type to modify text.
//! * Resize window.
//!
//! The main operating structure is as follows:
//! * Load a font
//! * Initialize the brush
//! * Set up the glyph cache texture
//!
//! Per frame:
//! * Queue up Sections of text, containing per-glyph colors and layout information
//! * Process the text into vertices, increasing glyph cache size if necessary
//! * Upload the vertices to the GPU if they've changed, and draw to the screen
use gl::types::*;
use glutin::{
    context::PossiblyCurrentContext,
    display::GetGlDisplay,
    prelude::{GlConfig, GlDisplay, NotCurrentGlContext},
    surface::{GlSurface, Surface, WindowSurface},
};
use glutin_winit::GlWindow;
use glyph_brush::{ab_glyph::*, *};
use raw_window_handle::HasWindowHandle;
use std::{
    env,
    ffi::CString,
    io::{self, Write},
    mem, ptr, str,
    time::Duration,
};
use winit::{
    dpi::PhysicalSize,
    event::{ElementState, KeyEvent, MouseScrollDelta, WindowEvent},
    event_loop::{ActiveEventLoop, ControlFlow, EventLoop},
    keyboard::{Key, NamedKey},
    window::Window,
};

const TITLE: &str = "glyph_brush opengl example - scroll to size, type to modify";

pub type Res<T> = Result<T, Box<dyn std::error::Error>>;
/// `[left_top * 3, right_bottom * 2, tex_left_top * 2, tex_right_bottom * 2, color * 4]`
pub type Vertex = [GLfloat; 13];

macro_rules! gl_assert_ok {
    () => {{
        let err = gl::GetError();
        assert_eq!(err, gl::NO_ERROR, "{}", gl_err_to_str(err));
    }};
}

#[allow(unused)] // it _is_ used
fn main() -> Res<()> {
    env_logger::init();

    // disables vsync maybe
    if env::var_os("vblank_mode").is_none() {
        env::set_var("vblank_mode", "0");
    }

    EventLoop::new()?.run_app(&mut WinitApp::None)?;
    Ok(())
}

enum WinitApp {
    None,
    Resumed(App),
}

impl winit::application::ApplicationHandler for WinitApp {
    fn resumed(&mut self, events: &ActiveEventLoop) {
        events.set_control_flow(ControlFlow::Poll);
        *self = Self::Resumed(App::new(events));
    }

    fn window_event(
        &mut self,
        events: &ActiveEventLoop,
        _: winit::window::WindowId,
        event: WindowEvent,
    ) {
        if let Self::Resumed(app) = self {
            app.window_event(events, event);
        }
    }

    fn about_to_wait(&mut self, _events: &ActiveEventLoop) {
        if let Self::Resumed(App { window, .. }) = self {
            window.request_redraw();
        };
    }
}

struct App {
    glyph_brush: GlyphBrush<Vertex, Extra, FontRef<'static>>,
    texture: GlGlyphTexture,
    text_pipe: GlTextPipe,
    text: String,
    font_size: f32,
    interval: spin_sleep_util::Interval,
    reporter: spin_sleep_util::RateReporter,
    max_image_dimension: u32,
    dimensions: PhysicalSize<u32>,
    gl_surface: Surface<WindowSurface>,
    gl_ctx: PossiblyCurrentContext,
    window: Window,
}

impl App {
    fn new(events: &ActiveEventLoop) -> Self {
        let (window, gl_config) = glutin_winit::DisplayBuilder::new()
            .with_window_attributes(Some(
                winit::window::Window::default_attributes()
                    .with_inner_size(winit::dpi::PhysicalSize::new(1024, 576))
                    .with_title(TITLE),
            ))
            .build(events, <_>::default(), |mut configs| {
                configs
                    .find(|c| c.srgb_capable() && c.num_samples() == 0)
                    .unwrap()
            })
            .unwrap();

        let window = window.unwrap(); // set in display builder
        let window_handle = window.window_handle().unwrap();
        let gl_display = gl_config.display();

        let context_attributes = glutin::context::ContextAttributesBuilder::new()
            .with_profile(glutin::context::GlProfile::Core)
            .with_context_api(glutin::context::ContextApi::OpenGl(Some(
                glutin::context::Version::new(3, 2),
            )))
            .build(Some(window_handle.as_raw()));

        let dimensions = window.inner_size();

        let (gl_surface, gl_ctx) = {
            let attrs = window.build_surface_attributes(<_>::default()).unwrap();
            let surface = unsafe {
                gl_display
                    .create_window_surface(&gl_config, &attrs)
                    .unwrap()
            };
            let context = unsafe {
                gl_display
                    .create_context(&gl_config, &context_attributes)
                    .unwrap()
            }
            .make_current(&surface)
            .unwrap();
            (surface, context)
        };

        // Load the OpenGL function pointers
        gl::load_with(|symbol| gl_display.get_proc_address(&CString::new(symbol).unwrap()) as _);

        let max_image_dimension = {
            let mut value = 0;
            unsafe { gl::GetIntegerv(gl::MAX_TEXTURE_SIZE, &mut value) };
            value as u32
        };

        let sans =
            FontRef::try_from_slice(include_bytes!("../../fonts/OpenSans-Light.ttf")).unwrap();
        let glyph_brush = GlyphBrushBuilder::using_font(sans).build();

        let texture = GlGlyphTexture::new(glyph_brush.texture_dimensions());

        let text_pipe = GlTextPipe::new(dimensions).unwrap();

        Self {
            window,
            gl_surface,
            gl_ctx,
            glyph_brush,
            texture,
            text_pipe,
            text: include_str!("text/lipsum.txt").into(),
            font_size: 18.0,
            interval: spin_sleep_util::interval(Duration::from_secs(1) / 250),
            reporter: spin_sleep_util::RateReporter::new(Duration::from_secs(1)),
            max_image_dimension,
            dimensions,
        }
    }

    fn window_event(&mut self, events: &ActiveEventLoop, event: WindowEvent) {
        match event {
            WindowEvent::CloseRequested => events.exit(),
            WindowEvent::KeyboardInput {
                event:
                    KeyEvent {
                        logical_key,
                        state: ElementState::Pressed,
                        ..
                    },
                ..
            } => match logical_key {
                Key::Named(NamedKey::Escape) => events.exit(),
                Key::Named(NamedKey::Backspace) => {
                    self.text.pop();
                }
                key => {
                    if let Some(str) = key.to_text() {
                        self.text.push_str(str);
                    }
                }
            },
            WindowEvent::MouseWheel {
                delta: MouseScrollDelta::LineDelta(_, y),
                ..
            } => {
                // increase/decrease font size
                let old_size = self.font_size;
                let mut size = self.font_size;
                if y > 0.0 {
                    size += (size / 4.0).max(2.0)
                } else {
                    size *= 4.0 / 5.0
                };
                self.font_size = size.clamp(1.0, 2000.0);
                if (self.font_size - old_size).abs() > 1e-2 {
                    eprint!("\r                            \r");
                    eprint!("font-size -> {:.1}", self.font_size);
                    let _ = io::stderr().flush();
                }
            }
            WindowEvent::RedrawRequested => self.draw(),
            _ => (),
        }
    }

    fn draw(&mut self) {
        let Self {
            window,
            gl_surface,
            gl_ctx,
            glyph_brush,
            texture,
            text_pipe,
            text,
            font_size,
            interval,
            reporter,
            max_image_dimension,
            dimensions,
        } = self;

        // handle window size changes
        let window_size = window.inner_size();
        if *dimensions != window_size {
            *dimensions = window_size;
            window.resize_surface(gl_surface, gl_ctx);
            unsafe {
                gl::Viewport(0, 0, dimensions.width as _, dimensions.height as _);
            }
            text_pipe.update_geometry(window_size);
        }

        let width = dimensions.width as f32;
        let height = dimensions.height as _;
        let scale = (*font_size * window.scale_factor() as f32).round();
        let base_text = Text::new(text).with_scale(scale);

        // Queue up all sections of text to be drawn
        glyph_brush.queue(
            Section::default()
                .add_text(base_text.with_color([0.9, 0.3, 0.3, 1.0]))
                .with_bounds((width / 3.15, height)),
        );

        glyph_brush.queue(
            Section::default()
                .add_text(base_text.with_color([0.3, 0.9, 0.3, 1.0]))
                .with_screen_position((width / 2.0, height / 2.0))
                .with_bounds((width / 3.15, height))
                .with_layout(
                    Layout::default()
                        .h_align(HorizontalAlign::Center)
                        .v_align(VerticalAlign::Center),
                ),
        );

        glyph_brush.queue(
            Section::default()
                .add_text(base_text.with_color([0.3, 0.3, 0.9, 1.0]))
                .with_screen_position((width, height))
                .with_bounds((width / 3.15, height))
                .with_layout(
                    Layout::default()
                        .h_align(HorizontalAlign::Right)
                        .v_align(VerticalAlign::Bottom),
                ),
        );

        // Tell glyph_brush to process the queued text
        let mut brush_action;
        loop {
            brush_action = glyph_brush.process_queued(
                |rect, tex_data| unsafe {
                    // Update part of gpu texture with new glyph alpha values
                    gl::BindTexture(gl::TEXTURE_2D, texture.name);
                    gl::TexSubImage2D(
                        gl::TEXTURE_2D,
                        0,
                        rect.min[0] as _,
                        rect.min[1] as _,
                        rect.width() as _,
                        rect.height() as _,
                        gl::RED,
                        gl::UNSIGNED_BYTE,
                        tex_data.as_ptr() as _,
                    );
                    gl_assert_ok!();
                },
                to_vertex,
            );

            // If the cache texture is too small to fit all the glyphs, resize and try again
            match brush_action {
                Ok(_) => break,
                Err(BrushError::TextureTooSmall { suggested, .. }) => {
                    let (new_width, new_height) = if (suggested.0 > *max_image_dimension
                        || suggested.1 > *max_image_dimension)
                        && (glyph_brush.texture_dimensions().0 < *max_image_dimension
                            || glyph_brush.texture_dimensions().1 < *max_image_dimension)
                    {
                        (*max_image_dimension, *max_image_dimension)
                    } else {
                        suggested
                    };
                    eprint!("\r                            \r");
                    eprintln!("Resizing glyph texture -> {new_width}x{new_height}");

                    // Recreate texture as a larger size to fit more
                    *texture = GlGlyphTexture::new((new_width, new_height));

                    glyph_brush.resize_texture(new_width, new_height);
                }
            }
        }
        // If the text has changed from what was last drawn, upload the new vertices to GPU
        match brush_action.unwrap() {
            BrushAction::Draw(vertices) => text_pipe.upload_vertices(&vertices),
            BrushAction::ReDraw => {}
        }

        // Draw the text to the screen
        unsafe {
            gl::ClearColor(0.02, 0.02, 0.02, 1.0);
            gl::Clear(gl::COLOR_BUFFER_BIT);
        }
        text_pipe.draw();

        gl_surface.swap_buffers(gl_ctx).unwrap();

        if let Some(rate) = reporter.increment_and_report() {
            window.set_title(&format!("{TITLE} {rate:.0} FPS"));
        }
        interval.tick();
    }
}

pub fn gl_err_to_str(err: u32) -> &'static str {
    match err {
        gl::INVALID_ENUM => "INVALID_ENUM",
        gl::INVALID_VALUE => "INVALID_VALUE",
        gl::INVALID_OPERATION => "INVALID_OPERATION",
        gl::INVALID_FRAMEBUFFER_OPERATION => "INVALID_FRAMEBUFFER_OPERATION",
        gl::OUT_OF_MEMORY => "OUT_OF_MEMORY",
        gl::STACK_UNDERFLOW => "STACK_UNDERFLOW",
        gl::STACK_OVERFLOW => "STACK_OVERFLOW",
        _ => "Unknown error",
    }
}

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

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

        // Fail on error
        if status != GLint::from(gl::TRUE) {
            let mut len = 0;
            gl::GetShaderiv(shader, gl::INFO_LOG_LENGTH, &mut len);
            let mut buf = vec![0; len as usize - 1]; // -1 to skip the trailing null character
            gl::GetShaderInfoLog(
                shader,
                len,
                ptr::null_mut(),
                buf.as_mut_ptr() as *mut GLchar,
            );
            return Err(str::from_utf8(&buf)?.into());
        }
    }
    Ok(shader)
}

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

        // Fail on error
        if status != GLint::from(gl::TRUE) {
            let mut len: GLint = 0;
            gl::GetProgramiv(program, gl::INFO_LOG_LENGTH, &mut len);
            let mut buf = vec![0; len as usize - 1]; // -1 to skip the trailing null character
            gl::GetProgramInfoLog(
                program,
                len,
                ptr::null_mut(),
                buf.as_mut_ptr() as *mut GLchar,
            );
            return Err(str::from_utf8(&buf)?.into());
        }
        Ok(program)
    }
}

#[inline]
pub fn to_vertex(
    glyph_brush::GlyphVertex {
        mut tex_coords,
        pixel_coords,
        bounds,
        extra,
    }: glyph_brush::GlyphVertex,
) -> Vertex {
    let gl_bounds = bounds;

    let mut gl_rect = Rect {
        min: point(pixel_coords.min.x, pixel_coords.min.y),
        max: point(pixel_coords.max.x, pixel_coords.max.y),
    };

    // handle overlapping bounds, modify uv_rect to preserve texture aspect
    if gl_rect.max.x > gl_bounds.max.x {
        let old_width = gl_rect.width();
        gl_rect.max.x = gl_bounds.max.x;
        tex_coords.max.x = tex_coords.min.x + tex_coords.width() * gl_rect.width() / old_width;
    }
    if gl_rect.min.x < gl_bounds.min.x {
        let old_width = gl_rect.width();
        gl_rect.min.x = gl_bounds.min.x;
        tex_coords.min.x = tex_coords.max.x - tex_coords.width() * gl_rect.width() / old_width;
    }
    if gl_rect.max.y > gl_bounds.max.y {
        let old_height = gl_rect.height();
        gl_rect.max.y = gl_bounds.max.y;
        tex_coords.max.y = tex_coords.min.y + tex_coords.height() * gl_rect.height() / old_height;
    }
    if gl_rect.min.y < gl_bounds.min.y {
        let old_height = gl_rect.height();
        gl_rect.min.y = gl_bounds.min.y;
        tex_coords.min.y = tex_coords.max.y - tex_coords.height() * gl_rect.height() / old_height;
    }

    [
        gl_rect.min.x,
        gl_rect.max.y,
        extra.z,
        gl_rect.max.x,
        gl_rect.min.y,
        tex_coords.min.x,
        tex_coords.max.y,
        tex_coords.max.x,
        tex_coords.min.y,
        extra.color[0],
        extra.color[1],
        extra.color[2],
        extra.color[3],
    ]
}

#[rustfmt::skip]
pub fn ortho(left: f32, right: f32, bottom: f32, top: f32, near: f32, far: f32) -> [f32; 16] {
    let tx = -(right + left) / (right - left);
    let ty = -(top + bottom) / (top - bottom);
    let tz = -(far + near) / (far - near);
    [
        2.0 / (right - left), 0.0, 0.0, 0.0,
        0.0, 2.0 / (top - bottom), 0.0, 0.0,
        0.0, 0.0, -2.0 / (far - near), 0.0,
        tx, ty, tz, 1.0,
    ]
}

/// The texture used to cache drawn glyphs
pub struct GlGlyphTexture {
    pub name: GLuint,
}

impl GlGlyphTexture {
    pub fn new((width, height): (u32, u32)) -> Self {
        let mut name = 0;
        unsafe {
            // Create a texture for the glyphs
            // The texture holds 1 byte per pixel as alpha data
            gl::PixelStorei(gl::UNPACK_ALIGNMENT, 1);
            gl::GenTextures(1, &mut name);
            gl::BindTexture(gl::TEXTURE_2D, name);
            gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_WRAP_S, gl::CLAMP_TO_EDGE as _);
            gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_WRAP_T, gl::CLAMP_TO_EDGE as _);
            gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MIN_FILTER, gl::LINEAR as _);
            gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MAG_FILTER, gl::LINEAR as _);
            gl::TexImage2D(
                gl::TEXTURE_2D,
                0,
                gl::RED as _,
                width as _,
                height as _,
                0,
                gl::RED,
                gl::UNSIGNED_BYTE,
                ptr::null(),
            );
            gl_assert_ok!();

            Self { name }
        }
    }

    pub fn clear(&self) {
        unsafe {
            gl::BindTexture(gl::TEXTURE_2D, self.name);
            gl::ClearTexImage(
                self.name,
                0,
                gl::RED,
                gl::UNSIGNED_BYTE,
                [12_u8].as_ptr() as _,
            );
            gl_assert_ok!();
        }
    }
}

impl Drop for GlGlyphTexture {
    fn drop(&mut self) {
        unsafe {
            gl::DeleteTextures(1, &self.name);
        }
    }
}

pub struct GlTextPipe {
    shaders: [GLuint; 2],
    program: GLuint,
    vao: GLuint,
    vbo: GLuint,
    transform_uniform: GLint,
    vertex_count: usize,
    vertex_buffer_len: usize,
}

impl GlTextPipe {
    pub fn new(window_size: winit::dpi::PhysicalSize<u32>) -> Res<Self> {
        let (w, h) = (window_size.width as f32, window_size.height as f32);

        let vs = compile_shader(include_str!("shader/text.vs"), gl::VERTEX_SHADER)?;
        let fs = compile_shader(include_str!("shader/text.fs"), gl::FRAGMENT_SHADER)?;
        let program = link_program(vs, fs)?;

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

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

            // Create a Vertex Buffer Object
            gl::GenBuffers(1, &mut vbo);
            gl::BindBuffer(gl::ARRAY_BUFFER, vbo);

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

            // Specify the layout of the vertex data
            let uniform = gl::GetUniformLocation(program, CString::new("transform")?.as_ptr());
            if uniform < 0 {
                return Err(format!("GetUniformLocation(\"transform\") -> {uniform}").into());
            }
            let transform = ortho(0.0, w, 0.0, h, 1.0, -1.0);
            gl::UniformMatrix4fv(uniform, 1, 0, transform.as_ptr());

            let mut offset = 0;
            for (v_field, float_count) in &[
                ("left_top", 3),
                ("right_bottom", 2),
                ("tex_left_top", 2),
                ("tex_right_bottom", 2),
                ("color", 4),
            ] {
                let attr = gl::GetAttribLocation(program, CString::new(*v_field)?.as_ptr());
                if attr < 0 {
                    return Err(format!("{v_field} GetAttribLocation -> {attr}").into());
                }
                gl::VertexAttribPointer(
                    attr as _,
                    *float_count,
                    gl::FLOAT,
                    gl::FALSE as _,
                    mem::size_of::<Vertex>() as _,
                    offset as _,
                );
                gl::EnableVertexAttribArray(attr as _);
                gl::VertexAttribDivisor(attr as _, 1); // Important for use with DrawArraysInstanced

                offset += float_count * 4;
            }
            gl_assert_ok!();

            uniform
        };

        Ok(Self {
            shaders: [vs, fs],
            program,
            vao,
            vbo,
            transform_uniform,
            vertex_count: 0,
            vertex_buffer_len: 0,
        })
    }

    pub fn upload_vertices(&mut self, vertices: &[Vertex]) {
        // Draw new vertices
        self.vertex_count = vertices.len();

        unsafe {
            gl::BindVertexArray(self.vao);
            gl::BindBuffer(gl::ARRAY_BUFFER, self.vbo);
            if self.vertex_buffer_len < self.vertex_count {
                gl::BufferData(
                    gl::ARRAY_BUFFER,
                    (self.vertex_count * mem::size_of::<Vertex>()) as GLsizeiptr,
                    vertices.as_ptr() as _,
                    gl::DYNAMIC_DRAW,
                );
                self.vertex_buffer_len = self.vertex_count;
            } else {
                gl::BufferSubData(
                    gl::ARRAY_BUFFER,
                    0,
                    (self.vertex_count * mem::size_of::<Vertex>()) as GLsizeiptr,
                    vertices.as_ptr() as _,
                );
            }
            gl_assert_ok!();
        }
    }

    pub fn update_geometry(&self, window_size: winit::dpi::PhysicalSize<u32>) {
        let (w, h) = (window_size.width as f32, window_size.height as f32);
        let transform = ortho(0.0, w, 0.0, h, 1.0, -1.0);

        unsafe {
            gl::UseProgram(self.program);
            gl::UniformMatrix4fv(self.transform_uniform, 1, 0, transform.as_ptr());
            gl_assert_ok!();
        }
    }

    pub fn draw(&self) {
        unsafe {
            // Enabled alpha blending
            gl::Enable(gl::BLEND);
            gl::BlendFunc(gl::SRC_ALPHA, gl::ONE);
            // Use srgb for consistency with other examples
            gl::Enable(gl::FRAMEBUFFER_SRGB);

            gl::UseProgram(self.program);
            gl::BindVertexArray(self.vao);
            // If implementing this yourself, make sure to set VertexAttribDivisor as well
            gl::DrawArraysInstanced(gl::TRIANGLE_STRIP, 0, 4, self.vertex_count as _);
            gl_assert_ok!();
        }
    }
}

impl Drop for GlTextPipe {
    fn drop(&mut self) {
        unsafe {
            gl::DeleteProgram(self.program);
            self.shaders.iter().for_each(|s| gl::DeleteShader(*s));
            gl::DeleteBuffers(1, &self.vbo);
            gl::DeleteVertexArrays(1, &self.vao);
        }
    }
}