#![feature(random, string_remove_matches)]
use ab_glyph::{FontRef, PxScale};
use anyhow::Result;
use image::{DynamicImage, ImageBuffer, ImageEncoder, Rgba, codecs::qoi::QoiEncoder};
use imageproc::drawing::{draw_text_mut, text_size};
use std::{
    hash::{Hash, Hasher},
    io::Write,
};

pub fn generate_fallback(name: &str, output: &mut dyn Write) -> Result<()> {
    let width = 1024;
    let height = (width * 1000) / 707;

    let mut image = ImageBuffer::<Rgba<f32>, Vec<f32>>::new(width, height);

    let text = name;
    let bg = random_accent(text, 0.4);
    image.pixels_mut().for_each(|p| *p = bg);

    let font = FontRef::try_from_slice(include_bytes!(
        "/usr/share/fonts/cantarell/Cantarell-VF.otf"
    ))
    .unwrap();
    let font_bold = FontRef::try_from_slice(include_bytes!(
        "/usr/share/fonts/TTF/OpenSans-CondensedExtraBold.ttf"
    ))
    .unwrap();

    let mut bgtext = text.to_string();
    bgtext.remove_matches(&[',', ' ']);
    let bgtext = bgtext.repeat(3);
    let scale = PxScale { x: 1000., y: 1000. };
    let (w, h) = text_size(scale, &font, &bgtext);
    for i in -1..4 {
        draw_text_mut(
            &mut image,
            random_accent(&text, 0.6),
            width as i32 / 2 - w as i32 / 2 + i * h as i32,
            i * h as i32 * 2 / 3,
            scale,
            &font_bold,
            &bgtext,
        );
    }

    image.enumerate_pixels_mut().for_each(|(_x, y, p)| {
        let f = 1. - (y as f32 / height as f32) * 0.5;
        p.0[0] *= f;
        p.0[1] *= f;
        p.0[2] *= f;
    });

    let scale = PxScale { x: 200., y: 200. };
    let (w, _h) = text_size(scale, &font, text);
    draw_text_mut(
        &mut image,
        Rgba([1., 1., 1., 1.]),
        width as i32 / 2 - w as i32 / 2,
        height as i32 * 3 / 4,
        scale,
        &font,
        text,
    );

    let image = DynamicImage::from(image).to_rgb8();

    QoiEncoder::new(output).write_image(
        image.as_raw(),
        image.width(),
        image.height(),
        image::ExtendedColorType::Rgb8,
    )?;
    Ok(())
}

struct XorshiftHasher(u64);
impl Hasher for XorshiftHasher {
    fn finish(&self) -> u64 {
        self.0
    }
    fn write(&mut self, bytes: &[u8]) {
        for b in bytes {
            self.0 = self
                .0
                .wrapping_add((*b as u64).wrapping_shl(24) + (*b as u64).wrapping_shl(56));
            self.0 ^= self.0.wrapping_shl(13);
            self.0 ^= self.0.wrapping_shr(7);
            self.0 ^= self.0.wrapping_shl(17);
        }
    }
}

fn random_accent(text: &str, y: f32) -> Rgba<f32> {
    let mut hasher = XorshiftHasher(0);
    text.hash(&mut hasher);
    let h = hasher.finish();
    let mut u = (h >> 32) as u32 as f32 / u32::MAX as f32;
    let mut v = (h) as u32 as f32 / u32::MAX as f32;
    u *= 0.2;
    v *= 0.2;
    Rgba([y - u * 0.5 - v * 0.5, y + v, y + u, 1.])
}