use image::{GenericImageView, DynamicImage};
use luminance::pixel::{NormRGB8UI, NormRGBA8UI};
use luminance::texture::{Dim2, Flat, Sampler, Texture, GenMipmaps};
use luminance_glfw::surface::GlfwSurface;
use std::fs::File;
use std::io::{BufReader, Read};
use std::path::Path;

pub fn load_file_into_vec(filename: &Path) -> Vec<u8> {
    let file = File::open(filename).unwrap();
    let mut file = BufReader::new(file);
    let mut buf = vec![];
    file.read_to_end(&mut buf).unwrap();
    buf
}

pub enum LoadedTexture {
    Rgba(Texture<Flat, Dim2, NormRGBA8UI>),
    Rgb(Texture<Flat, Dim2, NormRGB8UI>),
}

pub fn load_rgb_png(surface: &mut GlfwSurface, path: &Path) -> Option<LoadedTexture> {
    // load the texture into memory as a whole bloc (i.e. no streaming)
    match image::open(&path) {
        Ok(img) => {
            let (width, height) = img.dimensions();
            let texels = img
                .pixels()
                .map(|(_x, _y, rgb)| (rgb[0], rgb[1], rgb[2]))
                .collect::<Vec<_>>();

            // create the luminance texture; the third argument is the number of mipmaps we want (leave it
            // to 0 for now) and the latest is a the sampler to use when sampling the texels in the
            // shader (we’ll just use the default one)
            let tex =
                Texture::new(surface, [width, height], 0, &Sampler::default()).expect("luminance texture creation");

            // the first argument disables mipmap generation (we don’t care so far)
            tex.upload(GenMipmaps::No, &texels);

            Some(LoadedTexture::Rgb(tex))
        }

        Err(e) => {
            eprintln!("cannot open image {}: {}", path.display(), e);
            None
        }
    }
}

pub fn load_rgb_a_pngs(surface: &mut GlfwSurface, rgb: &Path, alpha: &Path) -> Option<LoadedTexture> {
    // load the texture into memory as a whole bloc (i.e. no streaming)
    match image::open(&alpha) {
        Ok(img) => {
            let (width, height) = img.dimensions();
            let alpha = match img.grayscale() {
                DynamicImage::ImageLuma8(img) => img,
                _ => {
                    eprintln!("cannot convert alpha image {} to grayscale", alpha.display());
                    return None;
                }
            };
            let img = match image::open(&rgb) {
                Ok(img) => img,
                Err(e) => {
                    eprintln!("cannot open rgb image {}: {}", rgb.display(), e);
                    return None;
                },
            };
            let texels = img
                .pixels()
                .zip(alpha.pixels())
                .map(|((_x, _y, rgb), luma)| (rgb[0], rgb[1], rgb[1], luma[0]))
                .collect::<Vec<_>>();

            // create the luminance texture; the third argument is the number of mipmaps we want (leave it
            // to 0 for now) and the latest is a the sampler to use when sampling the texels in the
            // shader (we’ll just use the default one)
            let tex =
                Texture::new(surface, [width, height], 0, &Sampler::default()).expect("luminance texture creation");

            // the first argument disables mipmap generation (we don’t care so far)
            tex.upload(GenMipmaps::No, &texels);

            Some(LoadedTexture::Rgba(tex))
        }

        Err(e) => {
            eprintln!("cannot open alpha image {}: {}", alpha.display(), e);
            None
        }
    }
}