// Copyright 2020 Sergiusz 'q3k' Bazanski <q3k@q3k.org>
//
// This file is part of Abrasion.
//
// Abrasion is free software: you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation, version 3.
//
// Abrasion is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
// details.
//
// You should have received a copy of the GNU General Public License along with
// Abrasion.  If not, see <https://www.gnu.org/licenses/>.

use std::time;

use cgmath as cgm;

use crate::physics::color;
use crate::render::vulkan::data;

/// An Omni point light, with position in 3d space, and 'color' defined in lumens per CIE XYZ
/// color channel.
pub struct Omni {
    pub position: cgm::Vector3<f32>,
    /// Luminour power/flux defined as lumens per XYZ color channel.
    pub color: color::XYZ,

    pub id: u64,
}

impl Omni {
    /// Make a test light. This has... a color. It's kinda yellow. And something close to 650
    /// lumens of luminous power. 
    // TODO(q3k): implement [Kry85] (eq. 68) somewhere in //engine/src/physics for generation
    // of nice lights colours from color temperature.
    //
    // [Kry85]
    // M. Krystek. 1985. "An algorithm to calculate correlated color temperature"
    // Color Research & Application, 10 (1), 38–40.
    pub fn test(position: cgm::Vector3<f32>) -> Self {
        Self {
            position,
            color: color::XYZ::new(234.7, 214.1, 207.9),
            // TODO: use a better method
            id: time::SystemTime::now().duration_since(time::UNIX_EPOCH).unwrap().as_nanos() as u64,
        }
    }

    pub fn vulkan_uniform(&self) -> data::OmniLight {
        // TODO: cache this?
        data::OmniLight {
            pos: [self.position.x, self.position.y, self.position.z, 1.0],
            color: [self.color.x, self.color.y, self.color.z, 0.0],
        }
    }
}