//! This module contains the rendering structs.

use std::cell::Ref;
use std::borrow::Cow;

use image;
use image::{ImageBuffer, Rgba};

use glium::texture::{RawImage2d, SrgbTexture2d, Texture2dDataSink};
use glium::{Frame, Display, Surface, Program, DrawParameters, Depth, VertexBuffer};
use glium::{Rect, BlitTarget};
use glium::framebuffer::SimpleFrameBuffer;
use glium::uniforms::MagnifySamplerFilter;
use glium::draw_parameters::{DepthTest, Blend};
use glium::index::{NoIndices, PrimitiveType};
use glium::glutin::GlWindow;

use scene::Scene;
use camera::RenderCamera;

use model::{Vertex, Part, Model};
use math::vector::Vector3;

/// Image data stored as RGBA.
pub struct RgbaImageData {
    /// The array of colors.
    pub data: Vec<(u8, u8, u8, u8)>,

    /// The width of the image.
    pub width: u32,

    /// The height of the image.
    pub height: u32,
}

impl Texture2dDataSink<(u8, u8, u8, u8)> for RgbaImageData {
    fn from_raw(data: Cow<[(u8, u8, u8, u8)]>, width: u32, height: u32) -> Self {
        RgbaImageData {
            data: data.into_owned(),
            width: width,
            height: height,
        }
    }
}

/// A renderer. It contains a display, shaders, and some rendering parameters.
pub struct Renderer {
    /// The display on which the rendering will be done.
    display: Display,

    /// The shading program.
    program: Program,

    /// The background color.
    clear_color: (f32, f32, f32, f32),

    /// The texture that will be applied to non textured models.
    default_texture: SrgbTexture2d,
}

impl Renderer {
    /// Creates a new renderer from a display.
    ///
    /// Is uses the default shaders and creates an empty vec of models.
    pub fn new(display: Display) -> Renderer {

        let program = Program::from_source(
            &display,
            include_str!("../assets/shaders/shader.vert"),
            include_str!("../assets/shaders/shader.frag"),
            None
        ).unwrap();

        let image = RawImage2d::from_raw_rgba(vec![1.0, 1.0, 1.0, 1.0], (1, 1));
        let texture = SrgbTexture2d::new(&display, image).ok().unwrap();

        Renderer {
            display: display,
            program: program,
            clear_color: (0.0, 0.0, 0.0, 1.0),
            default_texture: texture,
        }

    }

    /// Returns the inner GlWindows.
    pub fn gl_window(&self) -> Ref<GlWindow> {
        self.display.gl_window()
    }

    /// Creates a SrgbTexture from a path to an image.
    pub fn make_texture(&self, path: &str) -> SrgbTexture2d {
        let image = image::open(path).unwrap().to_rgba();
        self.make_texture_from_buffer(image)
    }

    /// Creates a SrgbTexture from an image buffer.
    pub fn make_texture_from_buffer(&self, buffer: ImageBuffer<Rgba<u8>, Vec<u8>>) -> SrgbTexture2d {
        let dimensions = buffer.dimensions();
        let buffer = RawImage2d::from_raw_rgba_reversed(&buffer.into_raw(), dimensions);
        SrgbTexture2d::new(&self.display, buffer).ok().unwrap()
    }

    /// Creates a 1x1 SrgbTexture with the color passed as parameter.
    pub fn make_texture_from_color_channels(&self, r: f32, g: f32, b: f32, a: f32) -> SrgbTexture2d {
        let image = RawImage2d::from_raw_rgba(vec![r, g, b, a], (1, 1));
        SrgbTexture2d::new(&self.display, image).ok().unwrap()
    }

    /// Creates a 1x1 SrgbTexture with the color passed as parameter.
    pub fn make_texture_from_color(&self, c: (f32, f32, f32, f32)) -> SrgbTexture2d {
        let image = RawImage2d::from_raw_rgba(vec![c.0, c.1, c.2, c.3], (1, 1));
        SrgbTexture2d::new(&self.display, image).ok().unwrap()
    }

    /// Creates a frame from the display.
    pub fn draw(&self) -> Frame {
        self.display.draw()
    }

    /// Renders on the display.
    pub fn render<C: RenderCamera>(&self, scene: &Scene, camera: &C) {

        let mut target = self.draw();
        target.clear_color_srgb_and_depth(self.clear_color, 1.0);

        let perspective = camera.get_perspective_matrix();
        let view = camera.get_view_matrix();

        let params = DrawParameters {
            depth: Depth {
                test: DepthTest::IfLess,
                write: true,
                .. Default::default()
            },
            blend: Blend::alpha_blending(),
            .. Default::default()
        };

        for model in scene.iter() {
            let model = &*model.borrow();
            for part in &model.parts {

                if let &Some(ref buffer) = part.vertex_buffer() {

                    let diffuse = if let Some(ref name) = part.material_name {
                        model.materials.get(name).unwrap().diffuse
                    } else {
                        Vector3::new(1.0, 1.0, 1.0)
                    };

                    let texture = self.get_texture_of_part(&model, part);

                    let (texture, size) = if let Some((texture, size)) = texture {
                        (texture, size)
                    } else {
                        (&self.default_texture, Vector3::new(1.0, 1.0, 1.0))
                    };

                    target.draw(
                        buffer,
                        NoIndices(PrimitiveType::TrianglesList),
                        &self.program,
                        &uniform!(
                            diffuse: Into::<[f32; 3]>::into(diffuse),
                            tex: texture,
                            perspective: Into::<[[f32; 4]; 4]>::into(perspective),
                            view: Into::<[[f32; 4]; 4]>::into(view),
                            texture_size: Into::<[f32; 3]>::into(size),
                        ),
                            &params,
                        ).unwrap();
                }
            }
        }

        target.finish().unwrap();
    }

    /// Renders a part of a model.
    fn get_texture_of_part<'a>(&self, model: &'a Model, part: &Part) -> Option<(&'a SrgbTexture2d, Vector3<f32>)> {
        if let Some(ref material_name) = part.material_name {
            if let Some(ref material) = model.materials.get(material_name) {
                if let Some((texture, size)) = material.textures.get("map_Kd") {
                    if let Some(texture) = model.get_texture_by_name(texture) {
                        Some((texture, *size))
                    } else {
                        None
                    }
                } else {
                    None
                }
            } else {
                None
            }
        } else {
            None
        }
    }

    /// Builds a vertex buffer from a vector of vertex.
    pub fn build_vertex_buffer(&self, vertices: &Vec<Vertex>) -> VertexBuffer<Vertex> {
        VertexBuffer::new(&self.display, vertices).unwrap()
    }

    /// Changes the clear color of the renderer.
    pub fn set_clear_color(&mut self, r: f32, g: f32, b: f32, a: f32) {
        self.clear_color = (r, g, b, a);
    }

    /// Shows the window if hidden.
    pub fn show(&mut self) {
        self.gl_window().show();
    }

    /// Returns a DynamicImage of the corresponding frame.
    pub fn capture(&self, dimensions: (u32, u32)) -> image::DynamicImage {
        rgba_image_data_to_image(self.capture_rgba_image_data(dimensions))
    }

    /// Returns a RgbaImageData of the corresponding frame.
    pub fn capture_rgba_image_data(&self, dimensions: (u32, u32)) -> RgbaImageData {

        let rect = Rect {
            left: 0,
            bottom: 0,
            width: dimensions.0,
            height: dimensions.1,
        };

        let blit_target = BlitTarget {
            left: 0,
            bottom: 0,
            width: dimensions.0 as i32,
            height: dimensions.1 as i32,
        };

        // Create temporary texture and blit the front buffer to it
        let texture = SrgbTexture2d::empty(&self.display, dimensions.0, dimensions.1)
            .unwrap();
        let framebuffer = SimpleFrameBuffer::new(&self.display, &texture)
            .unwrap();

        use glium::Surface;
        framebuffer.blit_from_frame(
            &rect,
            &blit_target,
            MagnifySamplerFilter::Nearest
        );

        // Read the texture into new pixel buffer
        let pixel_buffer = texture.read_to_pixel_buffer();
        pixel_buffer.read_as_texture_2d().unwrap()

    }
}

/// Converts a RgbaImamgeData to a DynamicImage.
pub fn rgba_image_data_to_image(image_data: RgbaImageData) -> image::DynamicImage {

    let pixels = {
        let mut v = Vec::with_capacity(image_data.data.len() * 4);
        for (a, b, c, d) in image_data.data {
            v.push(a);
            v.push(b);
            v.push(c);
            v.push(d);
        }
        v
    };


    // Create ImageBuffer
    let image_buffer =
        image::ImageBuffer::from_raw(image_data.width, image_data.height, pixels)
        .unwrap();

    // Save the screenshot to file
    let image = image::DynamicImage::ImageRgba8(image_buffer).flipv();

    image

}