//! # Depth of Field Example (Étape 26)
//!
//! Demonstrates cinematic DoF: a row of cubes receding into the distance,
//! with the focus plane at a configurable depth. Cubes at the focus distance
//! stay sharp; those closer or farther blur proportionally.
//!
//! ## Pipeline
//! DoF operates in linear HDR space **after** bloom and **before** tone mapping:
//! 1. CoC pass: reads the depth buffer, linearizes to world distance, computes
//!    per-pixel blur radius.
//! 2. Blur pass: 12-tap disc blur with variable radius (from CoC), producing
//!    natural circular bokeh.
//!
//! ## Controls
//! | Key | Action |
//! |-----|--------|
//! | Drag (LMB) | Orbit camera |
//! | Wheel | Zoom |
//! | `1` | Cinematic preset (focus=8m, strong blur) |
//! | `2` | Subtle preset (focus=8m, gentle blur) |
//! | `3` | Focus at 3m (near cubes sharp, far blurred) |
//! | `4` | Focus at 15m (far cubes sharp, near blurred) |
//! | `5` | DoF OFF |
//! | `R` | Reset camera |
//!
//! ## Build & Run
//! ```sh
//! cargo run -p wsg-lib --example dof --features "all-prims"
//! ```

use glam::Vec3;
use winit::event::MouseButton;
use winit::keyboard::KeyCode;
use wsg_lib::app::AppBuilder;
use wsg_lib::camera::CameraController;
use wsg_lib::core::{DoFConfig, ToneMapper, Transform};
use wsg_lib::mesh::{cube, icosphere, plane};
use wsg_lib::AppHandler;
use wsg_lib::utils::WsgError;

struct DoFDemo {
    camera: CameraController,
}

impl AppHandler for DoFDemo {
    fn setup(&mut self, app: &mut wsg_lib::App) {
        app.scene
            .register_shader("standard", wsg_lib::utils::STANDARD_SHADER_PATH)
            .unwrap();

        // Ground plane.
        app.scene
            .create_mesh("ground_mesh", plane(80.0, 80.0, 1, 1), None)
            .unwrap();
        app.scene
            .add_entity_with_transform(
                "ground",
                "ground_mesh",
                Transform::identity(),
            )
            .unwrap();

        // Row of cubes receding along -Z (distance ≈ 2 to 25 from camera at dist=8).
        app.scene
            .create_mesh("cube_mesh", cube(1.0), None)
            .unwrap();

        for i in 0..20 {
            let z = 3.0 - i as f32 * 1.5; // from z=3 (close) to z=-25.5 (far)
            let mut tf = Transform::identity();
            tf.translation = Vec3::new(0.0, 0.5, z);
            app.scene
                .add_entity_with_transform(&format!("cube_{i}"), "cube_mesh", tf)
                .unwrap();
        }

        // A few spheres scattered to the sides for visual interest.
        app.scene
            .create_mesh("sphere_mesh", icosphere(0.7, 3), None)
            .unwrap();
        let sphere_positions = [
            Vec3::new(2.5, 0.7, -2.0),
            Vec3::new(-3.0, 0.7, -6.0),
            Vec3::new(3.5, 0.7, -10.0),
            Vec3::new(-2.0, 0.7, -14.0),
            Vec3::new(2.0, 0.7, -18.0),
        ];
        for (i, pos) in sphere_positions.iter().enumerate() {
            let mut tf = Transform::identity();
            tf.translation = *pos;
            app.scene
                .add_entity_with_transform(&format!("sphere_{i}"), "sphere_mesh", tf)
                .unwrap();
        }

        // Directional light.
        let light_dir = Vec3::new(-0.4, -1.0, -0.3).normalize();
        app.scene
            .add_directional_light(light_dir, [1.0, 0.95, 0.85], 1.2)
            .unwrap();
        app.scene.set_ambient([0.08, 0.08, 0.1]);

        // Camera — positioned to look down the row of cubes.
        self.camera.yaw = 0.0;
        self.camera.pitch = 0.1;
        self.camera.distance = 8.0;
        self.camera.target = Vec3::new(0.0, 0.5, -8.0);
        self.camera.apply_to(app.scene.camera_mut());

        eprintln!("[DoF] Initial: Cinematic (focus=8m, aperture=0.3, max_blur=12)");
        eprintln!("[DoF] Keys: 1=cinematic 2=subtle 3=focus 3m 4=focus 15m 5=off R=reset");
    }

    fn update(&mut self, app: &mut wsg_lib::App) {
        // Orbit camera.
        let (dx, dy) = app.input.mouse_delta();
        if app.input.mouse_button_held(MouseButton::Left) {
            self.camera.orbit(dx, dy);
        }
        let (_, sy) = app.input.scroll_delta();
        self.camera.zoom(sy);

        // DoF presets.
        if app.input.key_pressed(KeyCode::Digit1) {
            app.renderer_mut()
                .set_dof(Some(DoFConfig::cinematic(8.0)));
            eprintln!("[DoF] → Cinematic (focus=8m, aperture=0.3, max_blur=12)");
        }
        if app.input.key_pressed(KeyCode::Digit2) {
            app.renderer_mut()
                .set_dof(Some(DoFConfig::subtle(8.0)));
            eprintln!("[DoF] → Subtle (focus=8m, aperture=0.1, max_blur=8)");
        }
        if app.input.key_pressed(KeyCode::Digit3) {
            app.renderer_mut()
                .set_dof(Some(DoFConfig::new(3.0, 0.3, 12.0)));
            eprintln!("[DoF] → Focus 3m (near sharp, far blurred)");
        }
        if app.input.key_pressed(KeyCode::Digit4) {
            app.renderer_mut()
                .set_dof(Some(DoFConfig::new(15.0, 0.3, 12.0)));
            eprintln!("[DoF] → Focus 15m (far sharp, near blurred)");
        }
        if app.input.key_pressed(KeyCode::Digit5) {
            app.renderer_mut().set_dof(None);
            eprintln!("[DoF] → OFF");
        }
        if app.input.key_pressed(KeyCode::KeyR) {
            self.camera.yaw = 0.0;
            self.camera.pitch = 0.1;
            self.camera.distance = 8.0;
            self.camera.target = Vec3::new(0.0, 0.5, -8.0);
        }

        self.camera.apply_to(app.scene.camera_mut());
    }

    fn render(&mut self, app: &mut wsg_lib::App, frame: &wsg_lib::core::Frame) {
        app.render_scene(frame.view());
    }
}

#[pollster::main]
async fn main() -> Result<(), WsgError> {
    let app = AppBuilder::new()
        .title("WSG — Depth of Field (Étape 26)")
        .size(1280, 720)
        .with_hdr(ToneMapper::Aces)
        .with_dof(DoFConfig::cinematic(8.0))
        .build()
        .await?;
    app.run(DoFDemo {
        camera: CameraController::default(),
    })
}