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use std::{io, cmp, thread, time};

pub trait MockRead : io::Read {
    #[inline]
    fn limited(self, limit: usize) -> Limited<Self>
        where Self: Sized
    {
        Limited {
            inner: self,
            limit: limit,
        }
    }
    
    #[inline]
    fn throttled(self, rate: usize) -> Throttled<Self>
        where Self: Sized
    {
        Throttled {
            inner: self,
            rate: rate,
        }
    }

}

impl<R: io::Read> MockRead for R {}

pub trait MockWrite : io::Write {
    #[inline]
    fn limited(self, limit: usize) -> Limited<Self>
        where Self: Sized
    {
        Limited {
            inner: self,
            limit: limit,
        }
    }
}

impl<W: io::Write> MockWrite for W {}

pub struct Limited<T> {
    inner: T,
    limit: usize,
}

impl<T> Limited<T> {
    #[inline]
    pub fn limit(&self) -> usize {
        self.limit
    }
}

impl<T: io::Read> io::Read for Limited<T> {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let max = cmp::min(buf.len(), self.limit);
        self.inner.read(&mut buf[..max])
    }
}

impl<T: io::Write> io::Write for Limited<T> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        let amt = cmp::min(self.limit, buf.len());
        self.inner.write(&buf[..amt])
    }

    #[inline]
    fn flush(&mut self) -> io::Result<()> {
        self.inner.flush()
    }
}

pub struct Throttled<T> {
    pub inner: T,
    pub rate: usize,
}

impl<R: io::Read> io::Read for Throttled<R> {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let amt = try!(self.inner.read(buf));
        let nanos = 1000000000u64 * amt as u64 / self.rate as u64;
        thread::sleep(time::Duration::new(nanos / 1000000000u64, (nanos % 1000000000u64) as u32));
        Ok(amt)
    }
}