use std::{
    fmt, error,
};
#[derive(Debug)]
pub struct ReadBytesError(String);

impl error::Error for ReadBytesError{}
impl fmt::Display for ReadBytesError
{
    #[inline] fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	write!(f, "{:?} is not a valid integer of bytes", self.0)
    }
}

/// Parse bytes from a string
pub fn bytes(string: impl AsRef<str>) -> Result<u64, ReadBytesError>
{
    let string = string.as_ref();
    let string = string.trim();
    
    let last = string.chars().last().ok_or_else(move || ReadBytesError(string.to_owned()))?;
    
    let (sl, mul) = match last {
	'k' | 'K' => (1, 1024),
	'm' | 'M' => (1, 1024 * 1024),
	'g' | 'G' => (1, 1024 * 1024 * 1024),
	_ if last.is_numeric() => (0, 1),
	_ => return Err(ReadBytesError(string.to_owned())),
    };
    string[..(string.len()-sl)].parse()
	.map(|x: u64| x * mul)
	.map_err(move |_| ReadBytesError(string.to_owned()))
}