use {
    digest::{Digest, FixedOutput, HashMarker},
    md5::Md5,
    sha1::Sha1,
    sha2::{Sha224, Sha256, Sha384, Sha512},
    std::{
        error::Error,
        fmt::Write,
        fs::File,
        io::{self, BufRead, BufReader, Read},
    },
};

pub enum HashType {
    Md5,
    Sha1,
    Sha224,
    Sha256,
    Sha384,
    Sha512,
}

pub fn compute_hash<T>(file: &str, mut hasher: T) -> Result<String, Box<dyn Error>>
where
    T: Default + FixedOutput + HashMarker,
{
    let mut buf = vec![];
    if file == "-" {
        let _s = io::stdin().read_to_end(&mut buf)?;
    } else {
        let mut fd = File::open(file)?;
        let _s = fd.read_to_end(&mut buf)?;
    }
    let mut s = String::new();
    hasher.update(&buf);
    let res = hasher.finalize();
    for c in res {
        write!(s, "{c:02x}")?;
    }
    Ok(s)
}

pub fn check_sums(file: &str, hashtype: HashType, erred: &mut usize) -> Result<(), Box<dyn Error>> {
    let fd = File::open(file)?;
    let reader = BufReader::new(fd);
    for line in reader.lines() {
        let line = line?;
        let mut split = line.split_whitespace();
        let sum = split.next().ok_or::<io::Error>(
            io::Error::new(io::ErrorKind::Other, "invalid checksum file"),
        )?;
        let file = split.next().ok_or::<io::Error>(
            io::Error::new(io::ErrorKind::Other, "invalid checksum file"),
        )?;
        let s = match hashtype {
            HashType::Md5 => compute_hash(file, Md5::new())?,
            HashType::Sha1 => compute_hash(file, Sha1::new())?,
            HashType::Sha224 => compute_hash(file, Sha224::new())?,
            HashType::Sha256 => compute_hash(file, Sha256::new())?,
            HashType::Sha384 => compute_hash(file, Sha384::new())?,
            HashType::Sha512 => compute_hash(file, Sha512::new())?,
        };
        if s.as_str() == sum {
            println!("{file}: OK");
        } else {
            println!("{file}: FAILED");
            *erred += 1;
        }
    }
    Ok(())
}