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// std
use std::cell::Cell;
use std::f32::consts::PI;
use std::sync::RwLock;
// pbrt
use crate::core::geometry::vec3_coordinate_system;
use crate::core::geometry::{Bounds3f, Normal3f, Point2f, Point3f, Ray, Vector3f};
use crate::core::interaction::{Interaction, InteractionCommon};
use crate::core::light::{LightFlags, VisibilityTester};
use crate::core::medium::MediumInterface;
use crate::core::pbrt::{Float, Spectrum};
use crate::core::sampling::concentric_sample_disk;
use crate::core::scene::Scene;
use crate::core::transform::Transform;

// see distant.h

pub struct DistantLight {
    // private data (see distant.h)
    pub l: Spectrum,
    pub w_light: Vector3f,
    pub world_center: RwLock<Point3f>,
    pub world_radius: RwLock<Float>,
    // inherited from class Light (see light.h)
    pub flags: u8,
    pub n_samples: i32,
    pub medium_interface: MediumInterface,
    pub light_to_world: Transform,
    pub world_to_light: Transform,
}

impl DistantLight {
    pub fn new(light_to_world: &Transform, l: &Spectrum, w_light: &Vector3f) -> Self {
        DistantLight {
            l: *l,
            w_light: light_to_world.transform_vector(&*w_light).normalize(),
            world_center: RwLock::new(Point3f::default()),
            world_radius: RwLock::new(0.0),
            flags: LightFlags::DeltaDirection as u8,
            n_samples: 1_i32,
            medium_interface: MediumInterface::default(),
            light_to_world: Transform::default(),
            world_to_light: Transform::default(),
        }
    }
    // Light
    pub fn sample_li<'a, 'b>(
        &'b self,
        iref: &'a InteractionCommon,
        light_intr: &'b mut InteractionCommon,
        _u: Point2f,
        wi: &mut Vector3f,
        pdf: &mut Float,
        vis: &mut VisibilityTester<'a, 'b>,
    ) -> Spectrum {
        // TODO: ProfilePhase _(Prof::LightSample);
        *wi = self.w_light;
        *pdf = 1.0 as Float;
        let p_outside: Point3f =
            iref.p + self.w_light * (2.0 as Float * *self.world_radius.read().unwrap());
        light_intr.p = p_outside;
        light_intr.time = iref.time;
        vis.p0 = Some(&iref);
        vis.p1 = Some(light_intr);
        self.l
    }
    pub fn power(&self) -> Spectrum {
        let world_radius: Float = *self.world_radius.read().unwrap();
        self.l * PI * world_radius * world_radius
    }
    /// Some of the **DistanceLight** methods need to know the bounds
    /// of the scene. Because lights are created before the scene
    /// geometry, these bounds aren't available when the
    /// **DistanceLight** constructor runs. Therefore,
    /// **DistanceLight** implements the optional *preprocess()*
    /// method to get the bound. This method is called at the end of
    /// the **Scene** constructor.
    pub fn preprocess(&self, scene: &Scene) {
        let mut world_center_ref = self.world_center.write().unwrap();
        let mut world_radius_ref = self.world_radius.write().unwrap();
        Bounds3f::bounding_sphere(
            &scene.world_bound(),
            &mut world_center_ref,
            &mut world_radius_ref,
        );
    }
    /// Default implementation returns no emitted radiance for a ray
    /// that escapes the scene bounds.
    pub fn le(&self, _ray: &Ray) -> Spectrum {
        Spectrum::new(0.0 as Float)
    }
    pub fn pdf_li(&self, _iref: &dyn Interaction, _wi: &Vector3f) -> Float {
        0.0 as Float
    }
    pub fn sample_le(
        &self,
        u1: Point2f,
        _u2: Point2f,
        time: Float,
        ray: &mut Ray,
        n_light: &mut Normal3f,
        pdf_pos: &mut Float,
        pdf_dir: &mut Float,
    ) -> Spectrum {
        // TODO: ProfilePhase _(Prof::LightSample);

        // choose point on disk oriented toward infinite light direction
        let mut v1: Vector3f = Vector3f::default();
        let mut v2: Vector3f = Vector3f::default();
        vec3_coordinate_system(&self.w_light, &mut v1, &mut v2);
        let cd: Point2f = concentric_sample_disk(&u1);
        let world_center: Point3f = *self.world_center.read().unwrap();
        let world_radius: Float = *self.world_radius.read().unwrap();
        let p_disk: Point3f = world_center + (v1 * cd.x + v2 * cd.y) * world_radius;
        // set ray origin and direction for infinite light ray
        *ray = Ray {
            o: p_disk + self.w_light * world_radius,
            d: -self.w_light,
            t_max: Cell::new(std::f32::INFINITY),
            time,
            differential: None,
            medium: None,
        };
        *n_light = Normal3f::from(ray.d);
        *pdf_pos = 1.0 as Float / (PI * world_radius * world_radius);
        *pdf_dir = 1.0 as Float;
        self.l
    }
    pub fn pdf_le(
        &self,
        _ray: &Ray,
        _n_light: &Normal3f,
        pdf_pos: &mut Float,
        pdf_dir: &mut Float,
    ) {
        let world_radius: Float = *self.world_radius.read().unwrap();
        *pdf_pos = 1.0 as Float / (PI * world_radius * world_radius);
        *pdf_dir = 0.0 as Float;
    }
    pub fn get_flags(&self) -> u8 {
        self.flags
    }
    pub fn get_n_samples(&self) -> i32 {
        self.n_samples
    }
}