//! Payload stream
use bytes::{Bytes, BytesMut};
use futures::task::Task;
#[cfg(not(test))]
use futures::task::current as current_task;
use futures::{Async, Poll, Stream};
use std::cell::RefCell;
use std::cmp;
use std::collections::VecDeque;
use std::rc::{Rc, Weak};

use error::PayloadError;

/// max buffer size 32k
pub(crate) const MAX_BUFFER_SIZE: usize = 32_768;

#[derive(Debug, PartialEq)]
pub(crate) enum PayloadStatus {
    Read,
    Pause,
    Dropped,
}

/// Buffered stream of bytes chunks
///
/// Payload stores chunks in a vector. First chunk can be received with
/// `.readany()` method. Payload stream is not thread safe. Payload does not
/// notify current task when new data is available.
///
/// Payload stream can be used as `HttpResponse` body stream.
#[derive(Debug)]
pub struct Payload {
    inner: Rc<RefCell<Inner>>,
}

impl Payload {
    /// Create payload stream.
    ///
    /// This method construct two objects responsible for bytes stream
    /// generation.
    ///
    /// * `PayloadSender` - *Sender* side of the stream
    ///
    /// * `Payload` - *Receiver* side of the stream
    pub fn new(eof: bool) -> (PayloadSender, Payload) {
        let shared = Rc::new(RefCell::new(Inner::new(eof)));

        (
            PayloadSender {
                inner: Rc::downgrade(&shared),
            },
            Payload { inner: shared },
        )
    }

    /// Create empty payload
    #[doc(hidden)]
    pub fn empty() -> Payload {
        Payload {
            inner: Rc::new(RefCell::new(Inner::new(true))),
        }
    }

    /// Length of the data in this payload
    #[cfg(test)]
    pub fn len(&self) -> usize {
        self.inner.borrow().len()
    }

    /// Is payload empty
    #[cfg(test)]
    pub fn is_empty(&self) -> bool {
        self.inner.borrow().len() == 0
    }

    /// Put unused data back to payload
    #[inline]
    pub fn unread_data(&mut self, data: Bytes) {
        self.inner.borrow_mut().unread_data(data);
    }

    #[cfg(test)]
    pub(crate) fn readall(&self) -> Option<Bytes> {
        self.inner.borrow_mut().readall()
    }

    #[inline]
    /// Set read buffer capacity
    ///
    /// Default buffer capacity is 32Kb.
    pub fn set_read_buffer_capacity(&mut self, cap: usize) {
        self.inner.borrow_mut().capacity = cap;
    }
}

impl Stream for Payload {
    type Item = Bytes;
    type Error = PayloadError;

    #[inline]
    fn poll(&mut self) -> Poll<Option<Bytes>, PayloadError> {
        self.inner.borrow_mut().readany()
    }
}

impl Clone for Payload {
    fn clone(&self) -> Payload {
        Payload {
            inner: Rc::clone(&self.inner),
        }
    }
}

/// Payload writer interface.
pub(crate) trait PayloadWriter {
    /// Set stream error.
    fn set_error(&mut self, err: PayloadError);

    /// Write eof into a stream which closes reading side of a stream.
    fn feed_eof(&mut self);

    /// Feed bytes into a payload stream
    fn feed_data(&mut self, data: Bytes);

    /// Need read data
    fn need_read(&self) -> PayloadStatus;
}

/// Sender part of the payload stream
pub struct PayloadSender {
    inner: Weak<RefCell<Inner>>,
}

impl PayloadWriter for PayloadSender {
    #[inline]
    fn set_error(&mut self, err: PayloadError) {
        if let Some(shared) = self.inner.upgrade() {
            shared.borrow_mut().set_error(err)
        }
    }

    #[inline]
    fn feed_eof(&mut self) {
        if let Some(shared) = self.inner.upgrade() {
            shared.borrow_mut().feed_eof()
        }
    }

    #[inline]
    fn feed_data(&mut self, data: Bytes) {
        if let Some(shared) = self.inner.upgrade() {
            shared.borrow_mut().feed_data(data)
        }
    }

    #[inline]
    fn need_read(&self) -> PayloadStatus {
        // we check need_read only if Payload (other side) is alive,
        // otherwise always return true (consume payload)
        if let Some(shared) = self.inner.upgrade() {
            if shared.borrow().need_read {
                PayloadStatus::Read
            } else {
                #[cfg(not(test))]
                {
                    if shared.borrow_mut().io_task.is_none() {
                        shared.borrow_mut().io_task = Some(current_task());
                    }
                }
                PayloadStatus::Pause
            }
        } else {
            PayloadStatus::Dropped
        }
    }
}

#[derive(Debug)]
struct Inner {
    len: usize,
    eof: bool,
    err: Option<PayloadError>,
    need_read: bool,
    items: VecDeque<Bytes>,
    capacity: usize,
    task: Option<Task>,
    io_task: Option<Task>,
}

impl Inner {
    fn new(eof: bool) -> Self {
        Inner {
            eof,
            len: 0,
            err: None,
            items: VecDeque::new(),
            need_read: true,
            capacity: MAX_BUFFER_SIZE,
            task: None,
            io_task: None,
        }
    }

    #[inline]
    fn set_error(&mut self, err: PayloadError) {
        self.err = Some(err);
    }

    #[inline]
    fn feed_eof(&mut self) {
        self.eof = true;
    }

    #[inline]
    fn feed_data(&mut self, data: Bytes) {
        self.len += data.len();
        self.items.push_back(data);
        self.need_read = self.len < self.capacity;
        if let Some(task) = self.task.take() {
            task.notify()
        }
    }

    #[cfg(test)]
    fn len(&self) -> usize {
        self.len
    }

    #[cfg(test)]
    pub(crate) fn readall(&mut self) -> Option<Bytes> {
        let len = self.items.iter().map(|b| b.len()).sum();
        if len > 0 {
            let mut buf = BytesMut::with_capacity(len);
            for item in &self.items {
                buf.extend_from_slice(item);
            }
            self.items = VecDeque::new();
            self.len = 0;
            Some(buf.take().freeze())
        } else {
            self.need_read = true;
            None
        }
    }

    fn readany(&mut self) -> Poll<Option<Bytes>, PayloadError> {
        if let Some(data) = self.items.pop_front() {
            self.len -= data.len();
            self.need_read = self.len < self.capacity;
            #[cfg(not(test))]
            {
                if self.need_read && self.task.is_none() {
                    self.task = Some(current_task());
                }
                if let Some(task) = self.io_task.take() {
                    task.notify()
                }
            }
            Ok(Async::Ready(Some(data)))
        } else if let Some(err) = self.err.take() {
            Err(err)
        } else if self.eof {
            Ok(Async::Ready(None))
        } else {
            self.need_read = true;
            #[cfg(not(test))]
            {
                if self.task.is_none() {
                    self.task = Some(current_task());
                }
                if let Some(task) = self.io_task.take() {
                    task.notify()
                }
            }
            Ok(Async::NotReady)
        }
    }

    fn unread_data(&mut self, data: Bytes) {
        self.len += data.len();
        self.items.push_front(data);
    }
}

/// Payload buffer
pub struct PayloadBuffer<S> {
    len: usize,
    items: VecDeque<Bytes>,
    stream: S,
}

impl<S> PayloadBuffer<S>
where
    S: Stream<Item = Bytes, Error = PayloadError>,
{
    /// Create new `PayloadBuffer` instance
    pub fn new(stream: S) -> Self {
        PayloadBuffer {
            len: 0,
            items: VecDeque::new(),
            stream,
        }
    }

    /// Get mutable reference to an inner stream.
    pub fn get_mut(&mut self) -> &mut S {
        &mut self.stream
    }

    #[inline]
    fn poll_stream(&mut self) -> Poll<bool, PayloadError> {
        self.stream.poll().map(|res| match res {
            Async::Ready(Some(data)) => {
                self.len += data.len();
                self.items.push_back(data);
                Async::Ready(true)
            }
            Async::Ready(None) => Async::Ready(false),
            Async::NotReady => Async::NotReady,
        })
    }

    /// Read first available chunk of bytes
    #[inline]
    pub fn readany(&mut self) -> Poll<Option<Bytes>, PayloadError> {
        if let Some(data) = self.items.pop_front() {
            self.len -= data.len();
            Ok(Async::Ready(Some(data)))
        } else {
            match self.poll_stream()? {
                Async::Ready(true) => self.readany(),
                Async::Ready(false) => Ok(Async::Ready(None)),
                Async::NotReady => Ok(Async::NotReady),
            }
        }
    }

    /// Check if buffer contains enough bytes
    #[inline]
    pub fn can_read(&mut self, size: usize) -> Poll<Option<bool>, PayloadError> {
        if size <= self.len {
            Ok(Async::Ready(Some(true)))
        } else {
            match self.poll_stream()? {
                Async::Ready(true) => self.can_read(size),
                Async::Ready(false) => Ok(Async::Ready(None)),
                Async::NotReady => Ok(Async::NotReady),
            }
        }
    }

    /// Return reference to the first chunk of data
    #[inline]
    pub fn get_chunk(&mut self) -> Poll<Option<&[u8]>, PayloadError> {
        if self.items.is_empty() {
            match self.poll_stream()? {
                Async::Ready(true) => (),
                Async::Ready(false) => return Ok(Async::Ready(None)),
                Async::NotReady => return Ok(Async::NotReady),
            }
        }
        match self.items.front().map(|c| c.as_ref()) {
            Some(chunk) => Ok(Async::Ready(Some(chunk))),
            None => Ok(Async::NotReady),
        }
    }

    /// Read exact number of bytes
    #[inline]
    pub fn read_exact(&mut self, size: usize) -> Poll<Option<Bytes>, PayloadError> {
        if size <= self.len {
            self.len -= size;
            let mut chunk = self.items.pop_front().unwrap();
            if size < chunk.len() {
                let buf = chunk.split_to(size);
                self.items.push_front(chunk);
                Ok(Async::Ready(Some(buf)))
            } else if size == chunk.len() {
                Ok(Async::Ready(Some(chunk)))
            } else {
                let mut buf = BytesMut::with_capacity(size);
                buf.extend_from_slice(&chunk);

                while buf.len() < size {
                    let mut chunk = self.items.pop_front().unwrap();
                    let rem = cmp::min(size - buf.len(), chunk.len());
                    buf.extend_from_slice(&chunk.split_to(rem));
                    if !chunk.is_empty() {
                        self.items.push_front(chunk);
                    }
                }
                Ok(Async::Ready(Some(buf.freeze())))
            }
        } else {
            match self.poll_stream()? {
                Async::Ready(true) => self.read_exact(size),
                Async::Ready(false) => Ok(Async::Ready(None)),
                Async::NotReady => Ok(Async::NotReady),
            }
        }
    }

    /// Remove specified amount if bytes from buffer
    #[inline]
    pub fn drop_bytes(&mut self, size: usize) {
        if size <= self.len {
            self.len -= size;

            let mut len = 0;
            while len < size {
                let mut chunk = self.items.pop_front().unwrap();
                let rem = cmp::min(size - len, chunk.len());
                len += rem;
                if rem < chunk.len() {
                    chunk.split_to(rem);
                    self.items.push_front(chunk);
                }
            }
        }
    }

    /// Copy buffered data
    pub fn copy(&mut self, size: usize) -> Poll<Option<BytesMut>, PayloadError> {
        if size <= self.len {
            let mut buf = BytesMut::with_capacity(size);
            for chunk in &self.items {
                if buf.len() < size {
                    let rem = cmp::min(size - buf.len(), chunk.len());
                    buf.extend_from_slice(&chunk[..rem]);
                }
                if buf.len() == size {
                    return Ok(Async::Ready(Some(buf)));
                }
            }
        }

        match self.poll_stream()? {
            Async::Ready(true) => self.copy(size),
            Async::Ready(false) => Ok(Async::Ready(None)),
            Async::NotReady => Ok(Async::NotReady),
        }
    }

    /// Read until specified ending
    pub fn read_until(&mut self, line: &[u8]) -> Poll<Option<Bytes>, PayloadError> {
        let mut idx = 0;
        let mut num = 0;
        let mut offset = 0;
        let mut found = false;
        let mut length = 0;

        for no in 0..self.items.len() {
            {
                let chunk = &self.items[no];
                for (pos, ch) in chunk.iter().enumerate() {
                    if *ch == line[idx] {
                        idx += 1;
                        if idx == line.len() {
                            num = no;
                            offset = pos + 1;
                            length += pos + 1;
                            found = true;
                            break;
                        }
                    } else {
                        idx = 0
                    }
                }
                if !found {
                    length += chunk.len()
                }
            }

            if found {
                let mut buf = BytesMut::with_capacity(length);
                if num > 0 {
                    for _ in 0..num {
                        buf.extend_from_slice(&self.items.pop_front().unwrap());
                    }
                }
                if offset > 0 {
                    let mut chunk = self.items.pop_front().unwrap();
                    buf.extend_from_slice(&chunk.split_to(offset));
                    if !chunk.is_empty() {
                        self.items.push_front(chunk)
                    }
                }
                self.len -= length;
                return Ok(Async::Ready(Some(buf.freeze())));
            }
        }

        match self.poll_stream()? {
            Async::Ready(true) => self.read_until(line),
            Async::Ready(false) => Ok(Async::Ready(None)),
            Async::NotReady => Ok(Async::NotReady),
        }
    }

    /// Read bytes until new line delimiter
    pub fn readline(&mut self) -> Poll<Option<Bytes>, PayloadError> {
        self.read_until(b"\n")
    }

    /// Put unprocessed data back to the buffer
    pub fn unprocessed(&mut self, data: Bytes) {
        self.len += data.len();
        self.items.push_front(data);
    }

    /// Get remaining data from the buffer
    pub fn remaining(&mut self) -> Bytes {
        self.items
            .iter_mut()
            .fold(BytesMut::new(), |mut b, c| {
                b.extend_from_slice(c);
                b
            }).freeze()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use failure::Fail;
    use futures::future::{lazy, result};
    use std::io;
    use tokio::runtime::current_thread::Runtime;

    #[test]
    fn test_error() {
        let err: PayloadError =
            io::Error::new(io::ErrorKind::Other, "ParseError").into();
        assert_eq!(format!("{}", err), "ParseError");
        assert_eq!(format!("{}", err.cause().unwrap()), "ParseError");

        let err = PayloadError::Incomplete;
        assert_eq!(
            format!("{}", err),
            "A payload reached EOF, but is not complete."
        );
    }

    #[test]
    fn test_basic() {
        Runtime::new()
            .unwrap()
            .block_on(lazy(|| {
                let (_, payload) = Payload::new(false);
                let mut payload = PayloadBuffer::new(payload);

                assert_eq!(payload.len, 0);
                assert_eq!(Async::NotReady, payload.readany().ok().unwrap());

                let res: Result<(), ()> = Ok(());
                result(res)
            })).unwrap();
    }

    #[test]
    fn test_eof() {
        Runtime::new()
            .unwrap()
            .block_on(lazy(|| {
                let (mut sender, payload) = Payload::new(false);
                let mut payload = PayloadBuffer::new(payload);

                assert_eq!(Async::NotReady, payload.readany().ok().unwrap());
                sender.feed_data(Bytes::from("data"));
                sender.feed_eof();

                assert_eq!(
                    Async::Ready(Some(Bytes::from("data"))),
                    payload.readany().ok().unwrap()
                );
                assert_eq!(payload.len, 0);
                assert_eq!(Async::Ready(None), payload.readany().ok().unwrap());

                let res: Result<(), ()> = Ok(());
                result(res)
            })).unwrap();
    }

    #[test]
    fn test_err() {
        Runtime::new()
            .unwrap()
            .block_on(lazy(|| {
                let (mut sender, payload) = Payload::new(false);
                let mut payload = PayloadBuffer::new(payload);

                assert_eq!(Async::NotReady, payload.readany().ok().unwrap());

                sender.set_error(PayloadError::Incomplete);
                payload.readany().err().unwrap();
                let res: Result<(), ()> = Ok(());
                result(res)
            })).unwrap();
    }

    #[test]
    fn test_readany() {
        Runtime::new()
            .unwrap()
            .block_on(lazy(|| {
                let (mut sender, payload) = Payload::new(false);
                let mut payload = PayloadBuffer::new(payload);

                sender.feed_data(Bytes::from("line1"));
                sender.feed_data(Bytes::from("line2"));

                assert_eq!(
                    Async::Ready(Some(Bytes::from("line1"))),
                    payload.readany().ok().unwrap()
                );
                assert_eq!(payload.len, 0);

                assert_eq!(
                    Async::Ready(Some(Bytes::from("line2"))),
                    payload.readany().ok().unwrap()
                );
                assert_eq!(payload.len, 0);

                let res: Result<(), ()> = Ok(());
                result(res)
            })).unwrap();
    }

    #[test]
    fn test_readexactly() {
        Runtime::new()
            .unwrap()
            .block_on(lazy(|| {
                let (mut sender, payload) = Payload::new(false);
                let mut payload = PayloadBuffer::new(payload);

                assert_eq!(Async::NotReady, payload.read_exact(2).ok().unwrap());

                sender.feed_data(Bytes::from("line1"));
                sender.feed_data(Bytes::from("line2"));

                assert_eq!(
                    Async::Ready(Some(Bytes::from_static(b"li"))),
                    payload.read_exact(2).ok().unwrap()
                );
                assert_eq!(payload.len, 3);

                assert_eq!(
                    Async::Ready(Some(Bytes::from_static(b"ne1l"))),
                    payload.read_exact(4).ok().unwrap()
                );
                assert_eq!(payload.len, 4);

                sender.set_error(PayloadError::Incomplete);
                payload.read_exact(10).err().unwrap();

                let res: Result<(), ()> = Ok(());
                result(res)
            })).unwrap();
    }

    #[test]
    fn test_readuntil() {
        Runtime::new()
            .unwrap()
            .block_on(lazy(|| {
                let (mut sender, payload) = Payload::new(false);
                let mut payload = PayloadBuffer::new(payload);

                assert_eq!(Async::NotReady, payload.read_until(b"ne").ok().unwrap());

                sender.feed_data(Bytes::from("line1"));
                sender.feed_data(Bytes::from("line2"));

                assert_eq!(
                    Async::Ready(Some(Bytes::from("line"))),
                    payload.read_until(b"ne").ok().unwrap()
                );
                assert_eq!(payload.len, 1);

                assert_eq!(
                    Async::Ready(Some(Bytes::from("1line2"))),
                    payload.read_until(b"2").ok().unwrap()
                );
                assert_eq!(payload.len, 0);

                sender.set_error(PayloadError::Incomplete);
                payload.read_until(b"b").err().unwrap();

                let res: Result<(), ()> = Ok(());
                result(res)
            })).unwrap();
    }

    #[test]
    fn test_unread_data() {
        Runtime::new()
            .unwrap()
            .block_on(lazy(|| {
                let (_, mut payload) = Payload::new(false);

                payload.unread_data(Bytes::from("data"));
                assert!(!payload.is_empty());
                assert_eq!(payload.len(), 4);

                assert_eq!(
                    Async::Ready(Some(Bytes::from("data"))),
                    payload.poll().ok().unwrap()
                );

                let res: Result<(), ()> = Ok(());
                result(res)
            })).unwrap();
    }
}