//! Common low-level file operations
use std::fmt::Display;
use std::path::Path;
use std::fs::File;
use std::io::{Read, Write, self};
use std::str::FromStr;

/// Write something to a file.
/// Useful for kernel configuration files.
#[inline]
pub fn write_single<P: AsRef<Path>, D: Display>(path: P, display: D) -> Result<(), io::Error> {
    let mut file = File::create(path)?;
    write!(file, "{}", display)
}

/// read_single error
#[derive(Debug)]
pub enum ReadError<E> {
    /// IO Error
    Io(io::Error),
    /// String parsing error
    Parse(E),
}

impl<E: std::error::Error> std::fmt::Display for ReadError<E> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Io(io) => write!(f, "io: {}", io),
            Self::Parse(e) => write!(f, "parse: {}", e),
        }
    }
}

impl<E: std::error::Error> std::error::Error for ReadError<E> {

}

/// Read something from a file.
/// Useful for kernel configuration files.
#[inline]
pub fn read_single<P: AsRef<Path>, D: FromStr<Err=E>, E>(path: P) -> Result<D, ReadError<E>> {
    let mut file = File::open(path).map_err(ReadError::Io)?;
    let mut string = String::new();
    file.read_to_string(&mut string).map_err(ReadError::Io)?;
    string.trim().parse().map_err(ReadError::Parse)
}