use std::collections::HashSet;
use std::io::Write;
//use std::os::unix::io::FromRawFd;
use std::path::{Path, PathBuf};
use std::pin::Pin;
use std::sync::{Arc, Mutex};
use std::task::{Context, Poll};
use std::thread;

use anyhow::{format_err, Error};
use futures::stream::Stream;

use nix::fcntl::OFlag;
use nix::sys::stat::Mode;
use nix::dir::Dir;

use crate::pxar;
use crate::backup::CatalogWriter;

/// Stream implementation to encode and upload .pxar archives.
///
/// The hyper client needs an async Stream for file upload, so we
/// spawn an extra thread to encode the .pxar data and pipe it to the
/// consumer.
pub struct PxarBackupStream {
    rx: Option<std::sync::mpsc::Receiver<Result<Vec<u8>, Error>>>,
    child: Option<thread::JoinHandle<()>>,
    error: Arc<Mutex<Option<String>>>,
}

impl Drop for PxarBackupStream {

    fn drop(&mut self) {
        self.rx = None;
        self.child.take().unwrap().join().unwrap();
    }
}

impl PxarBackupStream {

    pub fn new<W: Write + Send + 'static>(
        mut dir: Dir,
        path: PathBuf,
        device_set: Option<HashSet<u64>>,
        verbose: bool,
        skip_lost_and_found: bool,
        catalog: Arc<Mutex<CatalogWriter<W>>>,
        exclude_pattern: Vec<pxar::MatchPattern>,
        entries_max: usize,
    ) -> Result<Self, Error> {

        let (tx, rx) = std::sync::mpsc::sync_channel(10);

        let buffer_size = 256*1024;

        let error = Arc::new(Mutex::new(None));
        let error2 = error.clone();

        let catalog = catalog.clone();
        let child = std::thread::Builder::new().name("PxarBackupStream".to_string()).spawn(move || {
            let mut guard = catalog.lock().unwrap();
            let mut writer = std::io::BufWriter::with_capacity(buffer_size, crate::tools::StdChannelWriter::new(tx));

            if let Err(err) = pxar::Encoder::encode(
                path,
                &mut dir,
                &mut writer,
                Some(&mut *guard),
                device_set,
                verbose,
                skip_lost_and_found,
                pxar::flags::DEFAULT,
                exclude_pattern,
                entries_max,
            ) {
                let mut error = error2.lock().unwrap();
                *error = Some(err.to_string());
            }
        })?;

        Ok(Self {
            rx: Some(rx),
            child: Some(child),
            error,
        })
    }

    pub fn open<W: Write + Send + 'static>(
        dirname: &Path,
        device_set: Option<HashSet<u64>>,
        verbose: bool,
        skip_lost_and_found: bool,
        catalog: Arc<Mutex<CatalogWriter<W>>>,
        exclude_pattern: Vec<pxar::MatchPattern>,
        entries_max: usize,
    ) -> Result<Self, Error> {

        let dir = nix::dir::Dir::open(dirname, OFlag::O_DIRECTORY, Mode::empty())?;
        let path = std::path::PathBuf::from(dirname);

        Self::new(dir, path, device_set, verbose, skip_lost_and_found, catalog, exclude_pattern, entries_max)
    }
}

impl Stream for PxarBackupStream {

    type Item = Result<Vec<u8>, Error>;

    fn poll_next(self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Option<Self::Item>> {
        { // limit lock scope
            let error = self.error.lock().unwrap();
            if let Some(ref msg) = *error {
                return Poll::Ready(Some(Err(format_err!("{}", msg))));
            }
        }

        match crate::tools::runtime::block_in_place(|| self.rx.as_ref().unwrap().recv()) {
            Ok(data) => Poll::Ready(Some(data)),
            Err(_) => {
                let error = self.error.lock().unwrap();
                if let Some(ref msg) = *error {
                    return Poll::Ready(Some(Err(format_err!("{}", msg))));
                }
                Poll::Ready(None) // channel closed, no error
            }
        }
    }
}