use crate::core::*;
use crate::Float;
use image::{RgbImage, Rgb};

/// Contains the necesary values when doing calculations
///
/// This is not the final RGB value
#[derive(Clone)]
pub struct Pixel {
    /// The sum of the collected samples
    rgb: Spectrum,
    /// The amount of samples collected
    samples: u32,
}

pub struct Film {
    size: Vector2i,
    pub frame: Bound2i,

    pixels: Vec<Pixel>,
}

/// FilmTile is a small version of the Film used when rendering
///
/// This means that multiple threads can work on the same area and commit their changed when they
/// are done.
pub struct FilmTile {
    pub bounds: Bound2i,
    pub size: Vector2i,

    pixels: Vec<Pixel>,
}

impl Pixel {
    fn new() -> Pixel {
        Pixel {
            rgb: Default::default(),
            samples: 0,
        }
    }

    fn add(&mut self, c: &Spectrum, weight: Float) {
        self.rgb += &(c * weight);
        self.samples += 1;
    }

    fn finalize_rgb(&self) -> [u8; 3] {
        let (r, g, b) = (&self.rgb / (self.samples as Float)).to_rgb(255.0);
        [
            r as u8,
            g as u8,
            b as u8,
        ]
    }
}

impl std::ops::AddAssign<&Self> for Pixel {
    fn add_assign(&mut self, op: &Self) {
        self.rgb += &op.rgb;
        self.samples += op.samples;
    }
}

impl Film {
    pub fn new(size: Vector2i) -> Film {
        let area = size.x * size.y;
        Film {
            size,
            frame: Bound2i::new(&Vector2i::new(0), &size),
            pixels: vec![Pixel::new(); area as usize],
        }
    }

    /// Creates a new FilmTile from the specified bounds
    ///
    /// This tile can later be commited with the commit_tile function
    pub fn get_tile(&self, bound: &Bound2i) -> FilmTile {
        FilmTile::new(
            bound,
        )

    }

    /// Commit a tile back on the film
    ///
    /// This will lock the Film while the changes from the Tile is written
    pub fn commit_tile(&mut self, tile: &FilmTile) {
        let offset = tile.bounds.min;

        for y in 0 .. tile.size.y {
            let rowindex = (offset.y + y) * self.size.x;
            let prowindex = y * tile.size.x;

            for x in 0 .. tile.size.x {
                let index = offset.x + x + rowindex;
                let pindex: i32 = x + prowindex;

                self.pixels[index as usize] += &tile.pixels[pindex as usize];
            }
        }
    }

    pub fn finalize_image(&self) -> RgbImage {
        let mut img = RgbImage::new(self.size.x as u32, self.size.y as u32);

        for y in 0..self.size.y {
            let index = y * self.size.x;
            for x in 0..self.size.x {
                img.put_pixel(
                    x as u32, 
                    y as u32, 
                    Rgb(self.pixels[(index + x) as usize].finalize_rgb()),
                    );
            }
        }

        img
    }
}

impl FilmTile {
    fn new(bounds: &Bound2i) -> FilmTile {
        FilmTile {
            bounds: bounds.clone(),
            pixels: vec![Pixel::new(); bounds.area() as usize],
            size: bounds.diagonal(),
        }
    }

    /// Add a single sample sampled from the scene
    pub fn add_sample(&mut self, inp: &Vector2f, c: Spectrum) {
        let point = Vector2i::from(inp.floor());
        // Subtract the offset
        let point = point - self.bounds.min;

        let index = point.x + point.y * self.size.x;

        let pixel = self.pixels.get_mut(index as usize).unwrap();
        pixel.add(&c, 1.0);
    }
}