use sha2::{Digest, Sha256};
use std::{
    fs::File,
    io::{self, Read, Write},
    path::Path,
};
use walkdir::WalkDir;

pub fn hash_reader(name: &str, reader: &mut dyn Read) -> io::Result<String> {
    let mut hasher = Sha256::new();
    io::copy(reader, &mut hasher)?;
    Ok(format!("{}  {}\n", hex::encode(hasher.finalize()), name))
}

fn hash_file(fname: &Path, name: &Path) -> io::Result<String> {
    let mut fin = File::open(name)?;
    hash_reader(fname.as_os_str().to_str().unwrap(), &mut fin)
}

pub fn hash_dir(name: &str) -> io::Result<String> {
    let mut result = String::new();

    for entry in WalkDir::new(name)
        .into_iter()
        .filter(Result::is_ok)
        .map(Result::unwrap)
        .filter(|dir_entry| !dir_entry.file_type().is_dir())
        .map(|de| de.into_path())
        .map(|de| hash_file(&de.strip_prefix(name).unwrap(), &de))
    {
        result.push_str(&entry?);
    }

    let mut hasher = Sha256::new();
    hasher.write_all(&result.as_bytes())?;
    Ok(format!("h1:{}", base64::encode(hasher.finalize())))
}

#[cfg(test)]
mod tests {
    use std::process::Command;

    #[test]
    fn hash_dir() {
        let hash = super::hash_dir("./testdata").unwrap();
        assert_eq!("h1:nJxVO77692drULxxVJvOrMJE8fl8vG1NLjoDDv9e7+E=", &hash);
    }

    #[test]
    fn test_compare_go() {
        let rust_hash = super::hash_dir("./testdata").unwrap();
        let go_output = Command::new("go")
            .arg("run")
            .arg("./go_cmp")
            .output()
            .expect("go to run");
        let go_hash: String = String::from_utf8(go_output.stdout).expect("go output to be utf-8");
        assert_eq!(go_hash, rust_hash);
    }
}