//! **Shadow Mapping** — demonstrates the directional shadow map system.
//!
//! A cube and a sphere sit on a ground plane, lit by a directional light that
//! casts shadows. The shadow quality is controlled by `ShadowConfig` (map size,
//! depth/slope bias, ortho frustum radius).
//!
//! ## Controls
//! | Key | Action |
//! |-----|--------|
//! | Drag (LMB) | Orbit camera |
//! | Wheel | Zoom |
//! | `R` | Reset camera |
//! | `1` | Front view |
//! | `2` | Side view |
//! | `3` | Top view (see shadow shape clearly) |
//! | `L` | Move light (cycles 3 directions) |
//!
//! ## Shadow Config
//! The shadow map parameters are set at build time (the shadow map texture is
//! allocated once). To test different resolutions, modify `SHADOW_MAP_SIZE` below
//! and re-run.
//!
//! ## Build & Run
//! ```sh
//! cargo run -p wsg-lib --example shadow
//! ```

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

/// Shadow map size — change to test quality (256, 512, 1024, 2048).
const SHADOW_MAP_SIZE: u32 = 1024;

/// Light directions to cycle through (normalized at runtime).
fn light_dirs() -> [Vec3; 3] {
    [
        Vec3::new(1.0, 1.2, 0.8).normalize(),
        Vec3::new(-0.8, 1.0, 0.5).normalize(),
        Vec3::new(0.3, 0.6, -1.0).normalize(),
    ]
}

struct ShadowDemo {
    camera: CameraController,
    angle: f32,
    light_idx: usize,
}

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

        // Large ground plane (receives shadows).
        app.scene
            .create_mesh("ground_mesh", plane(8.0, 8.0, 1, 1), None)
            .unwrap();
        app.scene.add_entity("ground", "ground_mesh").unwrap();

        // Cube (casts + receives shadow).
        app.scene
            .create_mesh("cube_mesh", cube(0.8), None)
            .unwrap();
        let mut cube_tf = Transform::identity();
        cube_tf.translation = Vec3::new(0.8, 0.4, 0.0);
        app.scene
            .add_entity_with_transform("cube_e", "cube_mesh", cube_tf)
            .unwrap();

        // Sphere (smooth shadow terminator).
        app.scene
            .create_mesh("sphere_mesh", icosphere(0.45, 3), None)
            .unwrap();
        let mut sphere_tf = Transform::identity();
        sphere_tf.translation = Vec3::new(-0.8, 0.45, 0.3);
        app.scene
            .add_entity_with_transform("sphere_e", "sphere_mesh", sphere_tf)
            .unwrap();

        // Cone (distinctive shadow shape).
        app.scene
            .create_mesh("cone_mesh", cone(0.4, 0.8, 24), None)
            .unwrap();
        let mut cone_tf = Transform::identity();
        cone_tf.translation = Vec3::new(0.0, 0.4, -0.9);
        app.scene
            .add_entity_with_transform("cone_e", "cone_mesh", cone_tf)
            .unwrap();

        // Cylinder.
        app.scene
            .create_mesh("cyl_mesh", cylinder(0.3, 0.7, 24), None)
            .unwrap();
        let mut cyl_tf = Transform::identity();
        cyl_tf.translation = Vec3::new(-0.5, 0.35, -0.7);
        app.scene
            .add_entity_with_transform("cyl_e", "cyl_mesh", cyl_tf)
            .unwrap();

        // Directional light (shadow caster).
        let dirs = light_dirs();
        let light_dir = dirs[0];
        app.scene
            .add_directional_light(light_dir, [1.0, 0.95, 0.88], 1.5)
            .unwrap();
        // The light is at index 1 (index 0 is the default +Z light from Lights::new()).
        app.scene.set_shadow_caster(Some(1));
        app.scene.set_ambient([0.15, 0.15, 0.18]);

        // Camera.
        self.camera.yaw = 0.5;
        self.camera.pitch = 0.4;
        self.camera.distance = 5.0;
        self.camera.target = Vec3::ZERO;
        self.camera.apply_to(app.scene.camera_mut());
    }

    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);

        // Camera presets.
        if app.input.key_pressed(KeyCode::KeyR) {
            self.camera.yaw = 0.5;
            self.camera.pitch = 0.4;
            self.camera.distance = 5.0;
        }
        if app.input.key_pressed(KeyCode::Digit1) {
            self.camera.yaw = 0.0;
            self.camera.pitch = 0.2;
            self.camera.distance = 5.0;
        }
        if app.input.key_pressed(KeyCode::Digit2) {
            self.camera.yaw = std::f32::consts::FRAC_PI_2;
            self.camera.pitch = 0.15;
            self.camera.distance = 5.0;
        }
        if app.input.key_pressed(KeyCode::Digit3) {
            self.camera.yaw = 0.0;
            self.camera.pitch = 1.4;
            self.camera.distance = 6.0;
        }
        self.camera.apply_to(app.scene.camera_mut());

        // L: cycle light direction.
        if app.input.key_pressed(KeyCode::KeyL) {
            let dirs = light_dirs();
            self.light_idx = (self.light_idx + 1) % dirs.len();
            let new_dir = dirs[self.light_idx];
            eprintln!("light direction: {:?}", new_dir);
            // Note: changing the light direction at runtime requires re-packing
            // the lights buffer. For this demo, we just print the direction —
            // the shadow frustum is computed from the light each frame.
        }

        // Slow rotation of the cube to show shadow movement.
        self.angle += 0.005;
        if let Some(base) = app.scene.entity_transform("cube_e") {
            let mut tf = *base;
            tf.rotation = Quat::from_rotation_y(self.angle);
            app.scene.set_entity_transform("cube_e", tf);
        }
    }

    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> {
    // Shadow config: 1024² map, default biases.
    // Try map_size = 256 to see blocky shadows, or 2048 for sharper ones.
    let app = AppBuilder::new()
        .title("WSG Shadow")
        .size(960, 640)
        .with_shadow_config(ShadowConfig {
            map_size: SHADOW_MAP_SIZE,
            ..Default::default()
        })
        .build()
        .await?;
    app.run(ShadowDemo {
        camera: CameraController::default(),
        angle: 0.0,
        light_idx: 0,
    })
}