//! This example provides a 2D benchmark.
//!
//! Usage: spawn more entities by clicking on the screen.

use bevy::{
    diagnostic::{Diagnostics, FrameTimeDiagnosticsPlugin, LogDiagnosticsPlugin},
    prelude::*,
    window::{PresentMode, WindowResolution},
};
use rand::{rngs::StdRng, thread_rng, Rng, SeedableRng};

const BIRDS_PER_SECOND: u32 = 10000;
const GRAVITY: f32 = -9.8 * 100.0;
const MAX_VELOCITY: f32 = 750.;
const BIRD_SCALE: f32 = 0.15;
const HALF_BIRD_SIZE: f32 = 256. * BIRD_SCALE * 0.5;

#[derive(Resource)]
struct BevyCounter {
    pub count: usize,
    pub color: Color,
}

#[derive(Component)]
struct Bird {
    velocity: Vec3,
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins.set(WindowPlugin {
            primary_window: Some(Window {
                title: "BevyMark".into(),
                resolution: (800., 600.).into(),
                present_mode: PresentMode::AutoNoVsync,
                ..default()
            }),
            ..default()
        }))
        .add_plugin(FrameTimeDiagnosticsPlugin)
        .add_plugin(LogDiagnosticsPlugin::default())
        .insert_resource(BevyCounter {
            count: 0,
            color: Color::WHITE,
        })
        .add_systems(Startup, setup)
        .add_systems(FixedUpdate, scheduled_spawner)
        .add_systems(
            Update,
            (
                mouse_handler,
                movement_system,
                collision_system,
                counter_system,
            ),
        )
        .insert_resource(FixedTime::new_from_secs(0.2))
        .run();
}

#[derive(Resource)]
struct BirdScheduled {
    wave: usize,
    per_wave: usize,
}

fn scheduled_spawner(
    mut commands: Commands,
    windows: Query<&Window>,
    mut scheduled: ResMut<BirdScheduled>,
    mut counter: ResMut<BevyCounter>,
    bird_texture: Res<BirdTexture>,
) {
    let window = windows.single();

    if scheduled.wave > 0 {
        spawn_birds(
            &mut commands,
            &window.resolution,
            &mut counter,
            scheduled.per_wave,
            bird_texture.clone_weak(),
        );

        let mut rng = thread_rng();
        counter.color = Color::rgb_linear(rng.gen(), rng.gen(), rng.gen());
        scheduled.wave -= 1;
    }
}

#[derive(Resource, Deref)]
struct BirdTexture(Handle<Image>);

#[derive(Component)]
struct StatsText;

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    warn!(include_str!("warning_string.txt"));

    let texture = asset_server.load("branding/icon.png");

    let text_section = move |color, value: &str| {
        TextSection::new(
            value,
            TextStyle {
                font_size: 40.0,
                color,
                ..default()
            },
        )
    };

    commands.spawn(Camera2dBundle::default());
    commands.spawn((
        TextBundle::from_sections([
            text_section(Color::GREEN, "Bird Count"),
            text_section(Color::CYAN, ""),
            text_section(Color::GREEN, "\nFPS (raw): "),
            text_section(Color::CYAN, ""),
            text_section(Color::GREEN, "\nFPS (SMA): "),
            text_section(Color::CYAN, ""),
            text_section(Color::GREEN, "\nFPS (EMA): "),
            text_section(Color::CYAN, ""),
        ])
        .with_style(Style {
            position_type: PositionType::Absolute,
            top: Val::Px(5.0),
            left: Val::Px(5.0),
            ..default()
        }),
        StatsText,
    ));

    commands.insert_resource(BirdTexture(texture));
    commands.insert_resource(BirdScheduled {
        per_wave: std::env::args()
            .nth(1)
            .and_then(|arg| arg.parse::<usize>().ok())
            .unwrap_or_default(),
        wave: std::env::args()
            .nth(2)
            .and_then(|arg| arg.parse::<usize>().ok())
            .unwrap_or(1),
    });
}

fn mouse_handler(
    mut commands: Commands,
    time: Res<Time>,
    mouse_button_input: Res<Input<MouseButton>>,
    windows: Query<&Window>,
    bird_texture: Res<BirdTexture>,
    mut counter: ResMut<BevyCounter>,
) {
    let window = windows.single();

    if mouse_button_input.just_released(MouseButton::Left) {
        let mut rng = thread_rng();
        counter.color = Color::rgb_linear(rng.gen(), rng.gen(), rng.gen());
    }

    if mouse_button_input.pressed(MouseButton::Left) {
        let spawn_count = (BIRDS_PER_SECOND as f64 * time.delta_seconds_f64()) as usize;
        spawn_birds(
            &mut commands,
            &window.resolution,
            &mut counter,
            spawn_count,
            bird_texture.clone_weak(),
        );
    }
}

fn spawn_birds(
    commands: &mut Commands,
    primary_window_resolution: &WindowResolution,
    counter: &mut BevyCounter,
    spawn_count: usize,
    texture: Handle<Image>,
) {
    let bird_x = (primary_window_resolution.width() / -2.) + HALF_BIRD_SIZE;
    let bird_y = (primary_window_resolution.height() / 2.) - HALF_BIRD_SIZE;

    let mut rng = StdRng::from_entropy();

    let color = counter.color;
    let current_count = counter.count;

    commands.spawn_batch((0..spawn_count).map(move |count| {
        let velocity_x = rng.gen::<f32>() * MAX_VELOCITY - (MAX_VELOCITY * 0.5);
        let bird_z = (current_count + count) as f32 * 0.00001;
        (
            SpriteBundle {
                texture: texture.clone(),
                transform: Transform {
                    translation: Vec3::new(bird_x, bird_y, bird_z),
                    scale: Vec3::splat(BIRD_SCALE),
                    ..default()
                },
                sprite: Sprite { color, ..default() },
                ..default()
            },
            Bird {
                velocity: Vec3::new(velocity_x, 0., 0.),
            },
        )
    }));

    counter.count += spawn_count;
}

fn movement_system(time: Res<Time>, mut bird_query: Query<(&mut Bird, &mut Transform)>) {
    for (mut bird, mut transform) in &mut bird_query {
        transform.translation.x += bird.velocity.x * time.delta_seconds();
        transform.translation.y += bird.velocity.y * time.delta_seconds();
        bird.velocity.y += GRAVITY * time.delta_seconds();
    }
}

fn collision_system(windows: Query<&Window>, mut bird_query: Query<(&mut Bird, &Transform)>) {
    let window = windows.single();

    let half_width = window.width() * 0.5;
    let half_height = window.height() * 0.5;

    for (mut bird, transform) in &mut bird_query {
        let x_vel = bird.velocity.x;
        let y_vel = bird.velocity.y;
        let x_pos = transform.translation.x;
        let y_pos = transform.translation.y;

        if (x_vel > 0. && x_pos + HALF_BIRD_SIZE > half_width)
            || (x_vel <= 0. && x_pos - HALF_BIRD_SIZE < -(half_width))
        {
            bird.velocity.x = -x_vel;
        }
        if y_vel < 0. && y_pos - HALF_BIRD_SIZE < -half_height {
            bird.velocity.y = -y_vel;
        }
        if y_pos + HALF_BIRD_SIZE > half_height && y_vel > 0.0 {
            bird.velocity.y = 0.0;
        }
    }
}

fn counter_system(
    diagnostics: Res<Diagnostics>,
    counter: Res<BevyCounter>,
    mut query: Query<&mut Text, With<StatsText>>,
) {
    let mut text = query.single_mut();

    if counter.is_changed() {
        text.sections[1].value = counter.count.to_string();
    }

    if let Some(fps) = diagnostics.get(FrameTimeDiagnosticsPlugin::FPS) {
        if let Some(raw) = fps.value() {
            text.sections[3].value = format!("{raw:.2}");
        }
        if let Some(sma) = fps.average() {
            text.sections[5].value = format!("{sma:.2}");
        }
        if let Some(ema) = fps.smoothed() {
            text.sections[7].value = format!("{ema:.2}");
        }
    };
}