use digest::{Digest, DynDigest};
use std::{fs::File, io::Read, path::Path};

pub const DEFAULT_HASHER: &str = "sha3-512";

pub fn find_hasher(s: &str) -> std::io::Result<Box<dyn DynDigest>> {
    match s {
        "sha3-512" => Ok(Box::new(sha3::Sha3_512::new())),
        _ => Err(std::io::ErrorKind::InvalidInput.into()),
    }
}

pub fn hash_reader<R: Read>(hasher_name: &str, reader: &mut R) -> std::io::Result<String> {
    let mut buf = [0u8; 1024];
    let mut hasher = find_hasher(hasher_name)?;
    loop {
        let n = reader.read(&mut buf)?;
        hasher.update(&buf[..n]);
        if n == 0 {
            break;
        }
    }
    Ok(format!(
        "{hasher_name}:{}",
        const_hex::encode(hasher.finalize()),
    ))
}

pub fn verify_reader<R: Read>(reader: &mut R, expected: &str) -> std::io::Result<bool> {
    let hasher = expected.split(':').next().unwrap();
    let hash = hash_reader(hasher, reader)?;
    Ok(hash == expected)
}

pub fn hash_file<P: AsRef<Path>>(hasher: &str, path: P) -> std::io::Result<String> {
    hash_reader(hasher, &mut File::open(path)?)
}

pub fn verify_file<P: AsRef<Path>>(path: P, expected: &str) -> std::io::Result<bool> {
    verify_reader(&mut File::open(path)?, expected)
}