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extern crate bytes;
extern crate futures;
extern crate tokio_io;

use std::io::{self, Read, Write};

use bytes::BytesMut;
use futures::{Async, Poll};
use tokio_io::{AsyncRead, AsyncWrite};

#[derive(Debug)]
pub struct FakeStream {
    buf: BytesMut,
}

impl FakeStream {
    pub fn new() -> FakeStream {
        FakeStream {
            buf: BytesMut::new(),
        }
    }
}

impl Read for FakeStream {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let len = if buf.len() > self.buf.len() {
            self.buf.len()
        } else {
            buf.len()
        };

        let slice = self.buf.split_to(len).freeze();
        &buf[0..slice.len()].copy_from_slice(&slice);

        Ok(len)
    }
}

impl Write for FakeStream {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.buf.extend_from_slice(buf);

        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

impl AsyncRead for FakeStream {}

impl AsyncWrite for FakeStream {
    fn shutdown(&mut self) -> Poll<(), io::Error> {
        Ok(Async::Ready(()))
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_fake_stream() {
        let mut fake = FakeStream::new();

        let wl = fake.write(b"something").unwrap();

        assert_eq!(9, wl);

        let mut buf = [0; 5];

        let rl = fake.read(&mut buf).unwrap();

        assert_eq!(5, rl);

        assert_eq!(buf, *b"somet");

        let mut buf = *b"       ";

        let rl = fake.read(&mut buf).unwrap();

        assert_eq!(4, rl);

        assert_eq!(buf, *b"hing   ");
    }
}