use std::fs::File;

use memmap2::Mmap;
use rayon::prelude::*;

fn main() -> anyhow::Result<()> {
    let file = File::open("wikipedia.dat")?;

    let data = unsafe {
        Mmap::map(&file)?
    };

    let res = data
        .par_chunks(1024)
        .map(|chunk| {
            let mut freq = [0; 128];

            for byte in chunk.iter().filter(|b| b <= &&0x7F) {
                freq[*byte as usize] += 1;
            }

            freq
        })
        .reduce(|| [0_usize; 128], |mut acc, freq| {
            acc.iter_mut().zip(freq).for_each(|(a, n)| *a += n);
            acc
        });

    for (i, c) in res.iter().enumerate() {
        println!(
            "{} ({}) {}",
            i as u8 as char,
            i,
            c
        )
    }

    Ok(())
}