extern crate futures;
#[macro_use]
extern crate log;
extern crate tokio_io;
extern crate tokio_process;

use std::io;
use std::process::{Stdio, ExitStatus, Command};

use futures::future::Future;
use futures::stream::{self, Stream};
use tokio_io::io::{read_until, write_all, read_to_end};
use tokio_process::{CommandExt, Child};

mod support;

fn cat() -> Command {
    let mut cmd = support::cmd("cat");
    cmd.stdin(Stdio::piped())
       .stdout(Stdio::piped());
    cmd
}

fn feed_cat(mut cat: Child, n: usize) -> Box<Future<Item = ExitStatus, Error = io::Error>> {
    let stdin = cat.stdin().take().unwrap();
    let stdout = cat.stdout().take().unwrap();

    debug!("starting to feed");
    // Produce n lines on the child's stdout.
    let numbers = stream::iter_ok(0..n);
    let write = numbers.fold(stdin, |stdin, i| {
        debug!("sending line {} to child", i);
        write_all(stdin, format!("line {}\n", i).into_bytes()).map(|p| p.0)
    }).map(|_| ());

    // Try to read `n + 1` lines, ensuring the last one is empty
    // (i.e. EOF is reached after `n` lines.
    let reader = io::BufReader::new(stdout);
    let expected_numbers = stream::iter_ok(0..=n);
    let read = expected_numbers.fold((reader, 0), move |(reader, i), _| {
        let done = i >= n;
        debug!("starting read from child");
        read_until(reader, b'\n', Vec::new()).and_then(move |(reader, vec)| {
            debug!("read line {} from child ({} bytes, done: {})",
                   i, vec.len(), done);
            match (done, vec.len()) {
                (false, 0) => {
                    Err(io::Error::new(io::ErrorKind::BrokenPipe, "broken pipe"))
                },
                (true, n) if n != 0 => {
                    Err(io::Error::new(io::ErrorKind::Other, "extraneous data"))
                },
                _ => {
                    let s = std::str::from_utf8(&vec).unwrap();
                    let expected = format!("line {}\n", i);
                    if done || s == expected {
                        Ok((reader, i + 1))
                    } else {
                        Err(io::Error::new(io::ErrorKind::Other, "unexpected data"))
                    }
                }
            }
        })
    });

    // Compose reading and writing concurrently.
    Box::new(write.join(read).and_then(|_| cat))
}

/// Check for the following properties when feeding stdin and
/// consuming stdout of a cat-like process:
///
/// - A number of lines that amounts to a number of bytes exceeding a
///   typical OS buffer size can be fed to the child without
///   deadlock. This tests that we also consume the stdout
///   concurrently; otherwise this would deadlock.
///
/// - We read the same lines from the child that we fed it.
///
/// - The child does produce EOF on stdout after the last line.
#[test]
fn feed_a_lot() {
    let child = cat().spawn_async().unwrap();
    let status = support::run_with_timeout(feed_cat(child, 10000)).unwrap();
    assert_eq!(status.code(), Some(0));
}

// FIXME: delete this test once we have a resolution for #51
// This test's setup is flaky, and setting up a consistent test is nearly
// impossible: right now we invoke `cat` and immediately kill it, expecting
// that it didn't write anything, but if there's something wrong with the
// command itself (e.g. redirection issues, it doesn't actually print anything
// out, etc.) this test can falsely pass. Attempting a solution which writes
// some data, *then* kill the child, write more data, and assert that only the
// first write is echoed back seems like a good approach, however, due to the
// ordering of context switches or how the kernel buffers data we can get
// inconsistent results. We can keep this test around for now, but as soon as
// we have a solution for #51, we may have a better avenue for testing this
// functionality.
#[test]
fn drop_kills() {
    let mut child = cat().spawn_async().unwrap();
    let stdin = child.stdin().take().unwrap();
    let stdout = child.stdout().take().unwrap();
    drop(child);

    // Ignore all write errors since we expect a broken pipe here
    let writer = write_all(stdin, b"1234").then(|_| Ok(()));
    let reader = read_to_end(stdout, Vec::new());

    let (_, output) = support::CurrentThreadRuntime::new()
        .expect("failed to get rt")
        .spawn(writer)
        .block_on(support::with_timeout(reader))
        .expect("failed to get output");

    assert_eq!(output.len(), 0);
}

#[test]
fn wait_with_output_captures() {
    let mut child = cat().spawn_async().unwrap();
    let stdin = child.stdin().take().unwrap();
    let out = child.wait_with_output();

    let future = write_all(stdin, b"1234").map(|p| p.1).join(out);
    let ret = support::run_with_timeout(future).unwrap();
    let (written, output) = ret;

    assert!(output.status.success());
    assert_eq!(output.stdout, written);
    assert_eq!(output.stderr.len(), 0);
}

#[test]
fn status_closes_any_pipes() {
    // Cat will open a pipe between the parent and child.
    // If `status_async` doesn't ensure the handles are closed,
    // we would end up blocking forever (and time out).
    let child = cat().status_async().expect("failed to spawn child");

    support::run_with_timeout(child)
        .expect("time out exceeded! did we get stuck waiting on the child?");
}
