use bevy::{
    asset::LoadState,
    window::{
        Window,
        WindowMode,
        PrimaryWindow,
    },
    core_pipeline::Skybox,
    prelude::*,
    render::{
        render_resource::{TextureViewDescriptor, TextureViewDimension},
        renderer::RenderDevice,
        texture::CompressedImageFormats,
    },
};

fn main() {
    App::new()
        .add_systems(Startup, setup)
        .add_systems(Update, (
                asset_loaded.after(load_cubemap_asset),
                handle_input
        ))
        .add_plugins(DefaultPlugins.set(ImagePlugin::default_nearest()))
        .add_plugins(CameraControllerPlugin)
        .run();
}

#[derive(Resource)]
struct Cubemap {
    is_loaded: bool,
    index: usize,
    image_handle: Handle<Image>,
}

const CUBEMAPS: &[(&str, CompressedImageFormats)] = &[
    (
        "textures/stars_cubemap.png",
        CompressedImageFormats::NONE,
    ),
];

fn setup(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    mut windows: Query<&mut Window, With<PrimaryWindow>>
) {
    let skybox_handle = asset_server.load(CUBEMAPS[0].0);
    for mut window in &mut windows {
        window.cursor.grab_mode = CursorGrabMode::Locked;
        window.cursor.visible = false;
        window.mode = WindowMode::Fullscreen;
    }
    // camera
    commands.spawn((
        Camera3dBundle {
            transform: Transform::from_xyz(0.0, 0.0, 8.0).looking_at(Vec3::ZERO, Vec3::Y),
            ..default()
        },
        CameraController::default(),
        Skybox {
            image: skybox_handle.clone(),
            brightness: 150.0,
        },
    ));
    commands.insert_resource(Cubemap {
        is_loaded: false,
        index: 0,
        image_handle: skybox_handle,
    });
}

fn load_cubemap_asset(
    mut cubemap: ResMut<Cubemap>,
    asset_server: Res<AssetServer>,
    render_device: Res<RenderDevice>,
) {
    let supported_compressed_formats =
        CompressedImageFormats::from_features(render_device.features());

    let mut new_index = cubemap.index;
    for _ in 0..CUBEMAPS.len() {
        new_index = (new_index + 1) % CUBEMAPS.len();
        if supported_compressed_formats.contains(CUBEMAPS[new_index].1) {
            break;
        }
        info!("Skipping unsupported format: {:?}", CUBEMAPS[new_index]);
    }

    // Skip swapping to the same texture. Useful for when ktx2, zstd, or compressed texture support
    // is missing
    if new_index == cubemap.index {
        return;
    }

    cubemap.index = new_index;
    cubemap.image_handle = asset_server.load(CUBEMAPS[cubemap.index].0);
    cubemap.is_loaded = false;
}

fn asset_loaded(
    asset_server: Res<AssetServer>,
    mut images: ResMut<Assets<Image>>,
    mut cubemap: ResMut<Cubemap>,
    mut skyboxes: Query<&mut Skybox>,
) {
    if !cubemap.is_loaded && asset_server.load_state(&cubemap.image_handle) == LoadState::Loaded {
        info!("Swapping to {}...", CUBEMAPS[cubemap.index].0);
        let image = images.get_mut(&cubemap.image_handle).unwrap();
        // NOTE: PNGs do not have any metadata that could indicate they contain a cubemap texture,
        // so they appear as one texture. The following code reconfigures the texture as necessary.
        if image.texture_descriptor.array_layer_count() == 1 {
            image.reinterpret_stacked_2d_as_array(image.height() / image.width());
            image.texture_view_descriptor = Some(TextureViewDescriptor {
                dimension: Some(TextureViewDimension::Cube),
                ..default()
            });
        }

        for mut skybox in &mut skyboxes {
            skybox.image = cubemap.image_handle.clone();
        }

        cubemap.is_loaded = true;
    }
}

fn handle_input(
    keyboard_input: Res<ButtonInput<KeyCode>>,
    mut app_exit_events: ResMut<Events<bevy::app::AppExit>>
) {
    if keyboard_input.pressed(KeyCode::KeyQ) {
        app_exit_events.send(bevy::app::AppExit);
    }
}


// ------------------------------------------------------------------------------
// --------- copy&pasted from bevy's helpers/camera_controller.rs ---------------
// ------------------------------------------------------------------------------
use bevy::input::mouse::MouseMotion;
use bevy::window::CursorGrabMode;
use std::{f32::consts::*, fmt};

pub struct CameraControllerPlugin;

impl Plugin for CameraControllerPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Update, run_camera_controller);
    }
}

/// Based on Valorant's default sensitivity, not entirely sure why it is exactly 1.0 / 180.0,
/// but I'm guessing it is a misunderstanding between degrees/radians and then sticking with
/// it because it felt nice.
pub const RADIANS_PER_DOT: f32 = 1.0 / 180.0 * 0.5;

#[derive(Component)]
pub struct CameraController {
    pub enabled: bool,
    pub initialized: bool,
    pub sensitivity: f32,
    pub key_forward: KeyCode,
    pub key_back: KeyCode,
    pub key_left: KeyCode,
    pub key_right: KeyCode,
    pub key_up: KeyCode,
    pub key_down: KeyCode,
    pub key_run: KeyCode,
    pub mouse_key_cursor_grab: MouseButton,
    pub keyboard_key_toggle_cursor_grab: KeyCode,
    pub walk_speed: f32,
    pub run_speed: f32,
    pub friction: f32,
    pub pitch: f32,
    pub yaw: f32,
    pub velocity: Vec3,
}

impl Default for CameraController {
    fn default() -> Self {
        Self {
            enabled: true,
            initialized: false,
            sensitivity: 1.0,
            key_forward: KeyCode::KeyW,
            key_back: KeyCode::KeyS,
            key_left: KeyCode::KeyA,
            key_right: KeyCode::KeyD,
            key_up: KeyCode::KeyE,
            key_down: KeyCode::KeyQ,
            key_run: KeyCode::ShiftLeft,
            mouse_key_cursor_grab: MouseButton::Left,
            keyboard_key_toggle_cursor_grab: KeyCode::KeyM,
            walk_speed: 5.0,
            run_speed: 15.0,
            friction: 0.5,
            pitch: 0.0,
            yaw: 0.0,
            velocity: Vec3::ZERO,
        }
    }
}

impl fmt::Display for CameraController {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "
Freecam Controls:
    Mouse\t- Move camera orientation
    {:?}\t- Hold to grab cursor
    {:?}\t- Toggle cursor grab
    {:?} & {:?}\t- Fly forward & backwards
    {:?} & {:?}\t- Fly sideways left & right
    {:?} & {:?}\t- Fly up & down
    {:?}\t- Fly faster while held",
            self.mouse_key_cursor_grab,
            self.keyboard_key_toggle_cursor_grab,
            self.key_forward,
            self.key_back,
            self.key_left,
            self.key_right,
            self.key_up,
            self.key_down,
            self.key_run,
        )
    }
}

#[allow(clippy::too_many_arguments)]
fn run_camera_controller(
    time: Res<Time>,
    mut windows: Query<&mut Window>,
    mut mouse_events: EventReader<MouseMotion>,
    mouse_button_input: Res<ButtonInput<MouseButton>>,
    key_input: Res<ButtonInput<KeyCode>>,
    mut toggle_cursor_grab: Local<bool>,
    mut mouse_cursor_grab: Local<bool>,
    mut query: Query<(&mut Transform, &mut CameraController), With<Camera>>,
) {
    let dt = time.delta_seconds();

    if let Ok((mut transform, mut controller)) = query.get_single_mut() {
        if !controller.initialized {
            let (yaw, pitch, _roll) = transform.rotation.to_euler(EulerRot::YXZ);
            controller.yaw = yaw;
            controller.pitch = pitch;
            controller.initialized = true;
            *toggle_cursor_grab = true;
            info!("{}", *controller);
        }
        if !controller.enabled {
            mouse_events.clear();
            return;
        }

        // Handle key input
        let mut axis_input = Vec3::ZERO;
        if key_input.pressed(controller.key_forward) {
            axis_input.z += 1.0;
        }
        if key_input.pressed(controller.key_back) {
            axis_input.z -= 1.0;
        }
        if key_input.pressed(controller.key_right) {
            axis_input.x += 1.0;
        }
        if key_input.pressed(controller.key_left) {
            axis_input.x -= 1.0;
        }
        if key_input.pressed(controller.key_up) {
            axis_input.y += 1.0;
        }
        if key_input.pressed(controller.key_down) {
            axis_input.y -= 1.0;
        }

        let mut cursor_grab_change = false;
        if key_input.just_pressed(controller.keyboard_key_toggle_cursor_grab) {
            *toggle_cursor_grab = !*toggle_cursor_grab;
            cursor_grab_change = true;
        }
        if mouse_button_input.just_pressed(controller.mouse_key_cursor_grab) {
            *mouse_cursor_grab = true;
            cursor_grab_change = true;
        }
        if mouse_button_input.just_released(controller.mouse_key_cursor_grab) {
            *mouse_cursor_grab = false;
            cursor_grab_change = true;
        }
        let cursor_grab = *mouse_cursor_grab || *toggle_cursor_grab;

        // Apply movement update
        if axis_input != Vec3::ZERO {
            let max_speed = if key_input.pressed(controller.key_run) {
                controller.run_speed
            } else {
                controller.walk_speed
            };
            controller.velocity = axis_input.normalize() * max_speed;
        } else {
            let friction = controller.friction.clamp(0.0, 1.0);
            controller.velocity *= 1.0 - friction;
            if controller.velocity.length_squared() < 1e-6 {
                controller.velocity = Vec3::ZERO;
            }
        }
        let forward = *transform.forward();
        let right = *transform.right();
        transform.translation += controller.velocity.x * dt * right
            + controller.velocity.y * dt * Vec3::Y
            + controller.velocity.z * dt * forward;

        // Handle cursor grab
        if cursor_grab_change {
            if cursor_grab {
                for mut window in &mut windows {
                    if !window.focused {
                        continue;
                    }

                    window.cursor.grab_mode = CursorGrabMode::Locked;
                    window.cursor.visible = false;
                }
            } else {
                for mut window in &mut windows {
                    window.cursor.grab_mode = CursorGrabMode::None;
                    window.cursor.visible = true;
                }
            }
        }

        // Handle mouse input
        let mut mouse_delta = Vec2::ZERO;
        if cursor_grab {
            for mouse_event in mouse_events.read() {
                mouse_delta += mouse_event.delta;
            }
        } else {
            mouse_events.clear();
        }

        if mouse_delta != Vec2::ZERO {
            // Apply look update
            controller.pitch = (controller.pitch
                - mouse_delta.y * RADIANS_PER_DOT * controller.sensitivity)
                .clamp(-PI / 2., PI / 2.);
            controller.yaw -= mouse_delta.x * RADIANS_PER_DOT * controller.sensitivity;
            transform.rotation =
                Quat::from_euler(EulerRot::ZYX, 0.0, controller.yaw, controller.pitch);
        }
    }
}