//! The pointcloud Renderer for persistant pointcloud.
//! It uses OpenGL.shader for fast computation.
use kiss3d::camera::Camera;
use kiss3d::context::Context;
use kiss3d::renderer::Renderer;
use kiss3d::resource::{Effect, GPUVec, ShaderAttribute, ShaderUniform};
use na::{Matrix4, Point3};
use nalgebra as na;

/// Structure which manages the display of persistant Pointcloud.
pub struct PointCloudRenderer {
    shader: Effect,
    pos: ShaderAttribute<Point3<f32>>,
    color: ShaderAttribute<Point3<f32>>,
    proj: ShaderUniform<Matrix4<f32>>,
    view: ShaderUniform<Matrix4<f32>>,
    colored_points: GPUVec<Point3<f32>>,
    point_size: f32,
}

impl PointCloudRenderer {
    /// Creates a new points renderer.
    pub fn new(point_size: f32, point_cloud_data: GPUVec<Point3<f32>>) -> PointCloudRenderer {
        let mut shader = Effect::new_from_str(VERTEX_SHADER_SRC, FRAGMENT_SHADER_SRC);

        shader.use_program();

        PointCloudRenderer {
            colored_points: point_cloud_data,
            pos: shader.get_attrib::<Point3<f32>>("position").unwrap(),
            color: shader.get_attrib::<Point3<f32>>("color").unwrap(),
            proj: shader.get_uniform::<Matrix4<f32>>("proj").unwrap(),
            view: shader.get_uniform::<Matrix4<f32>>("view").unwrap(),
            shader,
            point_size,
        }
    }
    /// Compute the number of points in the PointCloud.
    pub fn num_points(&self) -> usize {
        self.colored_points.len() / 2
    }
}

impl Renderer for PointCloudRenderer {
    /// Actually draws the points.
    fn render(&mut self, pass: usize, camera: &mut dyn Camera) {
        if self.colored_points.len() == 0 {
            return;
        }

        self.shader.use_program();
        self.pos.enable();
        self.color.enable();

        camera.upload(pass, &mut self.proj, &mut self.view);

        self.color.bind_sub_buffer(&mut self.colored_points, 1, 1);
        self.pos.bind_sub_buffer(&mut self.colored_points, 1, 0);

        let ctxt = Context::get();
        ctxt.point_size(self.point_size);
        ctxt.draw_arrays(Context::POINTS, 0, (self.colored_points.len() - 10) as i32);
        self.pos.disable();
        self.color.disable();
    }
}

const VERTEX_SHADER_SRC: &str = "#version 100
    attribute vec3 position;
    attribute vec3 color;
    varying   vec3 Color;
    uniform   mat4 proj;
    uniform   mat4 view;
    void main() {
        gl_Position = proj * view * vec4(position, 1.0);
        Color = color;
    }";

const FRAGMENT_SHADER_SRC: &str = "#version 100
#ifdef GL_FRAGMENT_PRECISION_HIGH
   precision highp float;
#else
   precision mediump float;
#endif
    varying vec3 Color;
    void main() {
        gl_FragColor = vec4(Color, 1.0);
    }";