mod camera;
mod config;
mod sim;
mod ui;

use egui::Id;
use egui_wgpu::{RendererOptions, ScreenDescriptor};
use egui_winit::egui::{self, Context};
use futures::executor;
use rand::random_range;
use std::{collections::VecDeque, sync::Arc, time::Instant};
use wgpu::Origin3d;
use winit::{
    application::ApplicationHandler,
    event::{
        ElementState, KeyEvent, MouseButton,
        WindowEvent::{self},
    },
    event_loop::{ActiveEventLoop, ControlFlow, EventLoop},
    keyboard::{KeyCode, PhysicalKey},
    window::Window,
};

use crate::{
    camera::Camera,
    config::{CELLS_IN_CHUNK, CHUNK_SIZE, WINDOW_TITLE},
    sim::{cell::Cell, materials::MaterialId, sim::sim_tick, world::World},
    ui::draw_egui,
};

pub type Error = Box<dyn std::error::Error>;
pub type Result<T> = std::result::Result<T, Error>;

struct Config {
    fps: u16,
    brush_radius: u8,
    brush_material: MaterialId,
    use_threading: bool,
}

struct Input {
    last_mouse_pos_on_screen: Option<(f64, f64)>,
    last_mouse_pos_on_board: Option<(i32, i32)>,
    is_lmb_pressed: bool,

    // keybindings
    is_up_pressed: bool,
    is_left_pressed: bool,
    is_down_pressed: bool,
    is_right_pressed: bool,
}

struct Diagnostics {
    frame_times: VecDeque<f32>,
    fps: f32,
}

struct RendererChunk {
    texture: wgpu::Texture,
    bind_group: wgpu::BindGroup,
}

#[repr(C)]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct ChunkData {
    origin: [i32; 2],
}

struct RendererState {
    window: Arc<Window>,
    surface: wgpu::Surface<'static>,
    device: wgpu::Device,
    queue: wgpu::Queue,
    config: wgpu::SurfaceConfiguration,
    is_surface_configured: bool,

    // egui
    egui_context: egui::Context,
    egui_state: egui_winit::State,
    egui_renderer: egui_wgpu::Renderer,

    // world pixels
    renderer_chunks: Vec<RendererChunk>,
    pixels_pipeline: wgpu::RenderPipeline,
    camera_uniform_buffer: wgpu::Buffer,
    camera_uniform_bind_group: wgpu::BindGroup,
}

impl RendererState {
    // https://sotrh.github.io/learn-wgpu/beginner/tutorial1-window
    pub async fn new(window: Arc<Window>) -> Self {
        let size = window.inner_size();
        println!("Got window! ({}x{})", size.width, size.height);

        let instance = wgpu::Instance::default();
        let surface = instance.create_surface(window.clone()).unwrap();

        let adapter = instance
            .request_adapter(&wgpu::RequestAdapterOptions {
                compatible_surface: Some(&surface),
                ..wgpu::RequestAdapterOptions::default()
            })
            .await
            .unwrap();

        println!(
            "Initialized adapter, using GPU '{}'",
            adapter.get_info().name
        );

        let (device, queue) = adapter
            .request_device(&wgpu::DeviceDescriptor {
                required_features: wgpu::Features::default() | wgpu::Features::IMMEDIATES,
                required_limits: wgpu::Limits {
                    max_immediate_size: 16,
                    ..wgpu::Limits::defaults()
                },
                ..wgpu::DeviceDescriptor::default()
            })
            .await
            .unwrap();

        device.on_uncaptured_error(Arc::new(|err| panic!("{err}")));

        let surface_caps = surface.get_capabilities(&adapter);
        let surface_format = surface_caps
            .formats
            .iter()
            .find(|f| f.is_srgb())
            .copied()
            .unwrap_or(surface_caps.formats[0]);

        let config = wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: surface_format,
            width: size.width,
            height: size.height,
            present_mode: wgpu::PresentMode::AutoNoVsync,
            alpha_mode: surface_caps.alpha_modes[0],
            view_formats: vec![],
            desired_maximum_frame_latency: 2,
        };

        let egui_context = Context::default();
        let egui_state = egui_winit::State::new(
            egui_context.clone(),
            egui_context.viewport_id(),
            &window,
            None,
            None,
            None,
        );
        let egui_renderer = egui_wgpu::Renderer::new(&device, surface_format, {
            RendererOptions {
                msaa_samples: 1,
                ..RendererOptions::default()
            }
        });

        let camera_uniform_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                label: None,
                entries: &[wgpu::BindGroupLayoutEntry {
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: None,
                    },
                    binding: 0,
                    count: None,
                    visibility: wgpu::ShaderStages::VERTEX,
                }],
            });

        let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            label: None,
            entries: &[wgpu::BindGroupLayoutEntry {
                ty: wgpu::BindingType::Texture {
                    sample_type: wgpu::TextureSampleType::Float { filterable: true },
                    view_dimension: wgpu::TextureViewDimension::D2,
                    multisampled: false,
                },
                binding: 0,
                count: None,
                visibility: wgpu::ShaderStages::FRAGMENT,
            }],
        });

        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: Some("Shader"),
            source: wgpu::ShaderSource::Wgsl(include_str!("shader.wgsl").into()),
        });

        let pixels_pipeline_layout =
            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                label: None,
                immediate_size: 16,
                bind_group_layouts: &[
                    Some(&camera_uniform_bind_group_layout),
                    Some(&bind_group_layout),
                ],
            });

        let pixels_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: None,
            layout: Some(&pixels_pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: Some("vs_main"),
                buffers: &[],
                compilation_options: wgpu::PipelineCompilationOptions::default(),
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: Some("fs_main"),
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: Some(wgpu::BlendState::REPLACE),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
                compilation_options: wgpu::PipelineCompilationOptions::default(),
            }),
            primitive: wgpu::PrimitiveState {
                topology: wgpu::PrimitiveTopology::TriangleStrip,
                strip_index_format: None,
                front_face: wgpu::FrontFace::Ccw,
                cull_mode: None,
                polygon_mode: wgpu::PolygonMode::Fill,
                unclipped_depth: false,
                conservative: false,
            },
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview_mask: None,
            cache: None,
        });

        let camera_uniform_buffer = device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("Camera uniform buffer"),
            size: 16,
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
            mapped_at_creation: false,
        });

        let camera_uniform_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: None,
            layout: &camera_uniform_bind_group_layout,
            entries: &[wgpu::BindGroupEntry {
                binding: 0,
                resource: camera_uniform_buffer.as_entire_binding(),
            }],
        });

        let mut renderer_chunks: Vec<RendererChunk> = Vec::new();
        // match number of world chunks
        // TODO refactor so that this implicit
        for _ in -10..10 {
            for _ in -10..10 {
                let texture = device.create_texture(&wgpu::TextureDescriptor {
                    label: None,
                    mip_level_count: 1,
                    sample_count: 1,
                    usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
                    format: wgpu_types::TextureFormat::Rgba8UnormSrgb,
                    size: wgpu::Extent3d {
                        width: size.width,
                        height: size.height,
                        depth_or_array_layers: 1,
                    },
                    dimension: wgpu::TextureDimension::D2,
                    view_formats: &[],
                });

                let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
                    label: None,
                    layout: &bind_group_layout,
                    entries: &[wgpu::BindGroupEntry {
                        binding: 0,
                        resource: wgpu::BindingResource::TextureView(&texture.create_view(
                            &wgpu::TextureViewDescriptor {
                                dimension: Some(wgpu::TextureViewDimension::D2),
                                usage: Some(
                                    wgpu::TextureUsages::TEXTURE_BINDING
                                        | wgpu::TextureUsages::COPY_DST,
                                ),
                                ..wgpu::TextureViewDescriptor::default()
                            },
                        )),
                    }],
                });

                renderer_chunks.push(RendererChunk {
                    texture,
                    bind_group,
                })
            }
        }

        RendererState {
            window,
            surface,
            device,
            queue,
            config,
            is_surface_configured: false,

            egui_context,
            egui_state,
            egui_renderer,

            renderer_chunks,
            pixels_pipeline,
            camera_uniform_bind_group,
            camera_uniform_buffer,
        }
    }

    pub fn resize(&mut self, width: u32, height: u32) {
        if width > 0 && height > 0 {
            self.config.width = width;
            self.config.height = height;
            self.surface.configure(&self.device, &self.config);
            self.is_surface_configured = true;
        }
    }

    pub fn render(
        &mut self,
        world: &mut World,
        camera: &mut Camera,
        config: &mut Config,
        diagnostics: &Diagnostics,
        input: &Input,
    ) {
        puffin::profile_function!();

        self.window.request_redraw();

        if !self.is_surface_configured {
            return;
        }

        let output = {
            puffin::profile_scope!("Get current surface texture");
            match self.surface.get_current_texture() {
                wgpu::CurrentSurfaceTexture::Success(surface_texture) => surface_texture,
                wgpu::CurrentSurfaceTexture::Suboptimal(surface_texture) => surface_texture,
                wgpu::CurrentSurfaceTexture::Timeout
                | wgpu::CurrentSurfaceTexture::Occluded
                | wgpu::CurrentSurfaceTexture::Validation => {
                    // Skip this frame
                    return;
                }
                wgpu::CurrentSurfaceTexture::Outdated => {
                    self.surface.configure(&self.device, &self.config);
                    return;
                }
                wgpu::CurrentSurfaceTexture::Lost => {
                    panic!("Lost device?");
                }
            }
        };

        let view = output
            .texture
            .create_view(&wgpu::TextureViewDescriptor::default());

        let mut encoder = self
            .device
            .create_command_encoder(&wgpu::CommandEncoderDescriptor {
                label: Some("Render Encoder"),
            });

        let raw_input = self.egui_state.take_egui_input(&self.window);
        let full_output = self.egui_context.run_ui(raw_input, |ui| {
            let right_panel = egui::Panel::right(Id::new("right_panel"));
            right_panel
                .resizable(false)
                // TODO collapse button
                .show_collapsible(ui, &mut true, |panel_ui| {
                    draw_egui(panel_ui, config, camera, diagnostics, input)
                });
        });

        self.egui_state
            .handle_platform_output(&self.window, full_output.platform_output);

        let clipped_primitives = self
            .egui_context
            .tessellate(full_output.shapes, full_output.pixels_per_point);

        let pixels_per_point = full_output.pixels_per_point;

        let size = self.window.inner_size();
        let screen_descriptor = ScreenDescriptor {
            size_in_pixels: [size.width, size.height],
            pixels_per_point,
        };

        for (id, delta) in &full_output.textures_delta.set {
            self.egui_renderer
                .update_texture(&self.device, &self.queue, *id, delta);
        }

        self.egui_renderer.update_buffers(
            &self.device,
            &self.queue,
            &mut encoder,
            &clipped_primitives,
            &screen_descriptor,
        );

        // write the camera buffer
        self.queue.write_buffer(
            &self.camera_uniform_buffer,
            0,
            bytemuck::bytes_of(&camera.to_uniform()),
        );

        // write the chunk textures
        let mut chunk_buffer: [u8; (CELLS_IN_CHUNK * 4) as usize] =
            [0; (CELLS_IN_CHUNK * 4) as usize];

        {
            puffin::profile_scope!("Upload chunk textures");
            for &idx in world.chunk_position_to_chunk_idx.values() {
                let chunk = &mut world.chunks[idx];
                if !chunk.needs_texture_update {
                    continue;
                }
                chunk.needs_texture_update = false;

                // TODO use material palette to improve bandwidth of upload
                for i in 0..CELLS_IN_CHUNK {
                    let material = chunk.cells[i].material.def();
                    chunk_buffer[i * 4] = material.color.0;
                    chunk_buffer[i * 4 + 1] = material.color.1;
                    chunk_buffer[i * 4 + 2] = material.color.2;
                    chunk_buffer[i * 4 + 3] = material.color.3;
                }

                let render_chunk = &self.renderer_chunks[idx];
                self.queue.write_texture(
                    wgpu::TexelCopyTextureInfo {
                        texture: &render_chunk.texture,
                        aspect: wgpu::TextureAspect::All,
                        mip_level: 0,
                        origin: Origin3d::ZERO,
                    },
                    &chunk_buffer,
                    wgpu::TexelCopyBufferLayout {
                        bytes_per_row: Some(CHUNK_SIZE as u32 * 4),
                        offset: 0,
                        rows_per_image: Some(CHUNK_SIZE as u32),
                    },
                    wgpu::Extent3d {
                        width: CHUNK_SIZE as u32,
                        height: CHUNK_SIZE as u32,
                        depth_or_array_layers: 1,
                    },
                );
            }
        }

        {
            puffin::profile_scope!("Main render pass");
            let mut render_pass: wgpu::RenderPass<'_> =
                encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                    label: Some("Render Pass"),
                    color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                        view: &view,
                        resolve_target: None,
                        depth_slice: None,
                        ops: wgpu::Operations {
                            load: wgpu::LoadOp::Clear(wgpu::Color {
                                r: 0.0,
                                g: 0.0,
                                b: 0.0,
                                a: 1.0,
                            }),
                            store: wgpu::StoreOp::Store,
                        },
                    })],
                    depth_stencil_attachment: None,
                    occlusion_query_set: None,
                    timestamp_writes: None,
                    multiview_mask: None,
                });

            render_pass.set_pipeline(&self.pixels_pipeline);

            render_pass.set_bind_group(0, &self.camera_uniform_bind_group, &[]);

            // TODO only visible chunks
            for cx in -10..10 {
                for cy in -10..10 {
                    if let Some(idx) = world.chunk_position_to_chunk_idx.get(&(cx, cy)) {
                        let render_chunk = &self.renderer_chunks[*idx];
                        render_pass.set_bind_group(1, &render_chunk.bind_group, &[]);
                        render_pass
                            .set_immediates(0, bytemuck::bytes_of(&ChunkData { origin: [cx, cy] }));
                        render_pass.draw(0..4, 0..1);
                    }
                }
            }
        }

        {
            puffin::profile_scope!("Egui render pass");
            let mut egui_pass = encoder
                .begin_render_pass(&wgpu::RenderPassDescriptor {
                    label: Some("egui pass"),
                    color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                        view: &view,
                        resolve_target: None,
                        depth_slice: None,
                        ops: wgpu::Operations {
                            load: wgpu::LoadOp::Load,
                            store: wgpu::StoreOp::Store,
                        },
                    })],
                    depth_stencil_attachment: None,
                    timestamp_writes: None,
                    occlusion_query_set: None,
                    multiview_mask: None,
                })
                .forget_lifetime();

            self.egui_renderer
                .render(&mut egui_pass, &clipped_primitives, &screen_descriptor);
        }

        {
            puffin::profile_scope!("Submit queue and present");
            self.queue.submit(std::iter::once(encoder.finish()));
            output.present();
        }
    }
}

struct App {
    window: Option<Arc<Window>>,
    renderer_state: Option<RendererState>,

    input: Input,

    camera: Option<Camera>,

    world: Option<World>,

    // sim state
    // the last/current (not yet completed) seqno
    sim_seqno: u64,
    sim_paused: bool,
    ignore_pause_next_tick: bool,

    // used to compute delta_time
    last_frame_real: Instant,

    config: Config,
    diagnostics: Diagnostics,
}

impl Default for App {
    fn default() -> Self {
        Self {
            window: None,
            renderer_state: None,

            input: Input {
                last_mouse_pos_on_screen: None,
                last_mouse_pos_on_board: None,

                is_lmb_pressed: false,
                is_up_pressed: false,
                is_left_pressed: false,
                is_down_pressed: false,
                is_right_pressed: false,
            },

            camera: None,

            world: Some(World::from_default_size()),

            sim_seqno: 0,
            sim_paused: false,
            ignore_pause_next_tick: false,

            last_frame_real: Instant::now(),

            config: Config {
                fps: 120,
                use_threading: true,
                brush_radius: 10,
                brush_material: MaterialId::Sand,
            },
            diagnostics: Diagnostics {
                fps: 0.0,
                frame_times: VecDeque::new(),
            },
        }
    }
}

impl ApplicationHandler for App {
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        let window = Arc::new(
            event_loop
                .create_window(Window::default_attributes().with_title(WINDOW_TITLE))
                .unwrap(),
        );

        self.window = Some(window.clone());
        self.renderer_state = Some(executor::block_on(RendererState::new(window.clone())));

        let size = window.inner_size();
        self.camera = Some(Camera::new((size.width as i32, size.height as i32)));

        // let surface = SurfaceTexture::new(size.width, size.height, window_ref);

        // let mut pixels = Pixels::new(PIXEL_BUFFER_WIDTH, PIXEL_BUFFER_HEIGHT, surface).unwrap();

        // pixels.set_scaling_mode(ScalingMode::Fill);
    }

    fn window_event(
        &mut self,
        event_loop: &ActiveEventLoop,
        _: winit::window::WindowId,
        event: WindowEvent,
    ) {
        if let Some(window) = &self.window
            && let Some(renderer_state) = &mut self.renderer_state
            && let Some(world) = &mut self.world
            && let Some(camera) = &mut self.camera
        {
            let egui_response = renderer_state.egui_state.on_window_event(window, &event);
            // if egui consumed the event, it means we shouldn't treat any e.g., mouse clicks
            if egui_response.consumed {
                return;
            }

            match event {
                WindowEvent::KeyboardInput {
                    event:
                        KeyEvent {
                            physical_key: PhysicalKey::Code(code),
                            state,
                            ..
                        },
                    ..
                } => {
                    let pressed = state.is_pressed();
                    match code {
                        KeyCode::KeyW => self.input.is_up_pressed = pressed,
                        KeyCode::KeyA => self.input.is_left_pressed = pressed,
                        KeyCode::KeyS => self.input.is_down_pressed = pressed,
                        KeyCode::KeyD => self.input.is_right_pressed = pressed,
                        KeyCode::KeyC => self.world = Some(World::from_default_size()),
                        KeyCode::Space => {
                            if pressed {
                                self.sim_paused = !self.sim_paused
                            }
                        }
                        KeyCode::KeyX => {
                            if pressed {
                                self.ignore_pause_next_tick = true
                            }
                        }
                        _ => {}
                    }
                }
                WindowEvent::CursorMoved { position, .. } => {
                    self.input.last_mouse_pos_on_screen = Some((position.x, position.y));
                    let world_pos =
                        camera.screen_position_to_world(position.x as f32, position.y as f32);
                    self.input.last_mouse_pos_on_board =
                        Some((world_pos.0 as i32, world_pos.1 as i32))
                }
                WindowEvent::MouseInput { state, button, .. } => {
                    if button == MouseButton::Left {
                        self.input.is_lmb_pressed = state == ElementState::Pressed
                    }
                }
                WindowEvent::Resized(size) => {
                    renderer_state.resize(size.width, size.height);
                    camera.resize((size.width as i32, size.height as i32));
                }
                WindowEvent::CloseRequested => {
                    event_loop.exit();
                }
                WindowEvent::RedrawRequested => {
                    #[cfg(feature = "profiler")]
                    puffin::GlobalProfiler::lock().new_frame();

                    puffin::profile_scope!("redraw_requested");
                    // compute frame delta
                    let now = Instant::now();
                    let secs_since_last_frame = (now - self.last_frame_real).as_secs_f32();
                    let delta_time = secs_since_last_frame / (1.0 / 60.0);
                    self.last_frame_real = now;

                    self.diagnostics
                        .frame_times
                        .push_back(secs_since_last_frame);

                    if self.diagnostics.frame_times.len() > 30 {
                        self.diagnostics.frame_times.pop_front();
                    }

                    let average_frame_time = self.diagnostics.frame_times.iter().sum::<f32>()
                        / self.diagnostics.frame_times.len() as f32;

                    self.diagnostics.fps = 1.0 / average_frame_time;

                    // apply inputs
                    camera.handle_camera_input(&self.input, delta_time);

                    // // --TEST DRAWING--
                    if self.input.is_lmb_pressed
                        && let Some(lm) = self.input.last_mouse_pos_on_board
                    {
                        // start with the bounding box of the drawing brush circle + some margin
                        // clamp the bounding box to the board sie
                        let bb_xl = lm.0 - self.config.brush_radius as i32;
                        let bb_xu = lm.0 + self.config.brush_radius as i32;
                        let bb_yl = lm.1 - self.config.brush_radius as i32;
                        let bb_yu = lm.1 + self.config.brush_radius as i32;

                        // for each point, check if the distance is less than the brush size and write the pixel
                        for x in bb_xl..bb_xu {
                            for y in bb_yl..bb_yu {
                                let r = random_range(0.0..1.0);
                                if ((x - lm.0).pow(2) + (y - lm.1).pow(2))
                                    < (self.config.brush_radius as i32).pow(2)
                                    && r > 0.9
                                {
                                    let mut cell = Cell::from_material(self.config.brush_material);
                                    cell.flags = (self.sim_seqno as u8) & 0b1;
                                    world.set_cell_from_game_position(
                                        x, y, cell, // wake the chunk
                                        false,
                                    );
                                }
                            }
                        }
                    }

                    // TODO check if we need to run another sim tick given the sim speed + delta_time
                    // SIM logic
                    if !self.sim_paused || self.ignore_pause_next_tick {
                        sim_tick(world, self.sim_seqno, self.config.use_threading);
                        self.sim_seqno += 1;
                        self.ignore_pause_next_tick = false;
                    }

                    renderer_state.render(
                        world,
                        camera,
                        &mut self.config,
                        &self.diagnostics,
                        &mut self.input,
                    );
                }
                _ => {}
            }
        }
    }

    fn about_to_wait(&mut self, _: &ActiveEventLoop) {
        // let frame_duration: Duration = Duration::from_micros(1_000_000 / self.config.fps as u64);
        // limit our internal redraw requests to (fps)
        if let Some(window) = &self.window {
            window.request_redraw();
        } else {
            panic!("No window!")
        }
    }
}

#[cfg(feature = "profiler")]
fn start_profiler() {
    let _server = puffin_http::Server::new("127.0.0.1:8585").unwrap();
    puffin::set_scopes_on(true);
    std::mem::forget(_server); // keep serving for the process lifetime

    std::process::Command::new("puffin_viewer")
        .args(["--url", "127.0.0.1:8585"])
        .spawn()
        .ok(); // don't die if it isn't installed
}

fn main() -> Result<()> {
    #[cfg(feature = "profiler")]
    start_profiler();

    let event_loop = EventLoop::new()?;
    event_loop.set_control_flow(ControlFlow::Poll);

    let mut app = App::default();
    event_loop.run_app(&mut app)?;

    Ok(())
}