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use std::{self, cmp, thread, time};
use {Result, Read, Write};

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

    #[inline]
    fn throttled(self, rate: usize) -> Throttled<Self>
        where Self: Sized
    {
        Throttled { rate: rate, inner: self }
    }
}

impl<R: Read> MockRead for R {}

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

impl<W: Write> MockWrite for W {}

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

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

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

impl<T: Read> std::io::Read for Limited<T> {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize> { Read::read(self, buf) }
}

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

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

impl<T: Write> std::io::Write for Limited<T> {
    fn write(&mut self, buf: &[u8]) -> Result<usize> { Write::write(self, buf) }

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

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

impl<R: Read> Read for Throttled<R> {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> 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)
    }
}

impl<R: Read> std::io::Read for Throttled<R> {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> Result<usize> { Read::read(self, buf) }
}