//! IO
//!
//! This module contains a number of functions for working with
//! `AsyncRead` and `AsyncWrite` types, including the
//! `AsyncReadExt` and `AsyncWriteExt` traits which add methods
//! to the `AsyncRead` and `AsyncWrite` types.

use std::vec::Vec;

pub use futures_io::{AsyncRead, AsyncWrite, IoVec};

#[cfg(feature = "io-compat")] use crate::compat::Compat;

// Temporarily removed until AsyncBufRead is implemented
// pub use io::lines::{lines, Lines};
// pub use io::read_until::{read_until, ReadUntil};
// mod lines;
// mod read_until;

mod allow_std;
pub use self::allow_std::AllowStdIo;

mod copy_into;
pub use self::copy_into::CopyInto;

mod flush;
pub use self::flush::Flush;

mod read;
pub use self::read::Read;

mod read_exact;
pub use self::read_exact::ReadExact;

mod read_to_end;
pub use self::read_to_end::ReadToEnd;

mod close;
pub use self::close::Close;

mod split;
pub use self::split::{ReadHalf, WriteHalf};

mod window;
pub use self::window::Window;

mod write_all;
pub use self::write_all::WriteAll;

/// An extension trait which adds utility methods to `AsyncRead` types.
pub trait AsyncReadExt: AsyncRead {
    /// Creates a future which copies all the bytes from one object to another.
    ///
    /// The returned future will copy all the bytes read from this `AsyncRead` into the
    /// `writer` specified. This future will only complete once the `reader` has hit
    /// EOF and all bytes have been written to and flushed from the `writer`
    /// provided.
    ///
    /// On success the number of bytes is returned.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(async_await, await_macro, futures_api)]
    /// # futures::executor::block_on(async {
    /// use futures::io::AsyncReadExt;
    /// use std::io::Cursor;
    ///
    /// let mut reader = Cursor::new([1, 2, 3, 4]);
    /// let mut writer = Cursor::new([0u8; 5]);
    ///
    /// let bytes = await!(reader.copy_into(&mut writer))?;
    ///
    /// assert_eq!(bytes, 4);
    /// assert_eq!(writer.into_inner(), [1, 2, 3, 4, 0]);
    /// # Ok::<(), Box<std::error::Error>>(()) }).unwrap();
    /// ```
    fn copy_into<'a, W>(
        &'a mut self,
        writer: &'a mut W,
    ) -> CopyInto<'a, Self, W>
        where W: AsyncWrite,
    {
        CopyInto::new(self, writer)
    }

    /// Tries to read some bytes directly into the given `buf` in asynchronous
    /// manner, returning a future type.
    ///
    /// The returned future will resolve to the number of bytes read once the read
    /// operation is completed.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(async_await, await_macro, futures_api)]
    /// # futures::executor::block_on(async {
    /// use futures::io::AsyncReadExt;
    /// use std::io::Cursor;
    ///
    /// let mut reader = Cursor::new([1, 2, 3, 4]);
    /// let mut output = [0u8; 5];
    ///
    /// let bytes = await!(reader.read(&mut output[..]))?;
    ///
    /// // This is only guaranteed to be 4 because `&[u8]` is a synchronous
    /// // reader. In a real system you could get anywhere from 1 to
    /// // `output.len()` bytes in a single read.
    /// assert_eq!(bytes, 4);
    /// assert_eq!(output, [1, 2, 3, 4, 0]);
    /// # Ok::<(), Box<std::error::Error>>(()) }).unwrap();
    /// ```
    fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Read<'a, Self> {
        Read::new(self, buf)
    }

    /// Creates a future which will read exactly enough bytes to fill `buf`,
    /// returning an error if end of file (EOF) is hit sooner.
    ///
    /// The returned future will resolve once the read operation is completed.
    ///
    /// In the case of an error the buffer and the object will be discarded, with
    /// the error yielded.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(async_await, await_macro, futures_api)]
    /// # futures::executor::block_on(async {
    /// use futures::io::AsyncReadExt;
    /// use std::io::Cursor;
    ///
    /// let mut reader = Cursor::new([1, 2, 3, 4]);
    /// let mut output = [0u8; 4];
    ///
    /// await!(reader.read_exact(&mut output))?;
    ///
    /// assert_eq!(output, [1, 2, 3, 4]);
    /// # Ok::<(), Box<std::error::Error>>(()) }).unwrap();
    /// ```
    ///
    /// ## EOF is hit before `buf` is filled
    ///
    /// ```
    /// #![feature(async_await, await_macro, futures_api)]
    /// # futures::executor::block_on(async {
    /// use futures::io::AsyncReadExt;
    /// use std::io::{self, Cursor};
    ///
    /// let mut reader = Cursor::new([1, 2, 3, 4]);
    /// let mut output = [0u8; 5];
    ///
    /// let result = await!(reader.read_exact(&mut output));
    ///
    /// assert_eq!(result.unwrap_err().kind(), io::ErrorKind::UnexpectedEof);
    /// # });
    /// ```
    fn read_exact<'a>(
        &'a mut self,
        buf: &'a mut [u8],
    ) -> ReadExact<'a, Self> {
        ReadExact::new(self, buf)
    }

    /// Creates a future which will read all the bytes from this `AsyncRead`.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(async_await, await_macro, futures_api)]
    /// # futures::executor::block_on(async {
    /// use futures::io::AsyncReadExt;
    /// use std::io::Cursor;
    ///
    /// let mut reader = Cursor::new([1, 2, 3, 4]);
    /// let mut output = Vec::with_capacity(4);
    ///
    /// await!(reader.read_to_end(&mut output))?;
    ///
    /// assert_eq!(output, vec![1, 2, 3, 4]);
    /// # Ok::<(), Box<std::error::Error>>(()) }).unwrap();
    /// ```
    fn read_to_end<'a>(
        &'a mut self,
        buf: &'a mut Vec<u8>,
    ) -> ReadToEnd<'a, Self> {
        ReadToEnd::new(self, buf)
    }

    /// Helper method for splitting this read/write object into two halves.
    ///
    /// The two halves returned implement the `AsyncRead` and `AsyncWrite`
    /// traits, respectively.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(async_await, await_macro, futures_api)]
    /// # futures::executor::block_on(async {
    /// use futures::io::AsyncReadExt;
    /// use std::io::Cursor;
    ///
    /// // Note that for `Cursor` the read and write halves share a single
    /// // seek position. This may or may not be true for other types that
    /// // implement both `AsyncRead` and `AsyncWrite`.
    ///
    /// let mut reader = Cursor::new([1, 2, 3, 4]);
    /// let mut buffer = Cursor::new([0, 0, 0, 0, 5, 6, 7, 8]);
    /// let mut writer = Cursor::new([0u8; 5]);
    ///
    /// {
    ///     let (mut buffer_reader, mut buffer_writer) = (&mut buffer).split();
    ///     await!(reader.copy_into(&mut buffer_writer))?;
    ///     await!(buffer_reader.copy_into(&mut writer))?;
    /// }
    ///
    /// assert_eq!(buffer.into_inner(), [1, 2, 3, 4, 5, 6, 7, 8]);
    /// assert_eq!(writer.into_inner(), [5, 6, 7, 8, 0]);
    /// # Ok::<(), Box<std::error::Error>>(()) }).unwrap();
    /// ```
    fn split(self) -> (ReadHalf<Self>, WriteHalf<Self>)
        where Self: AsyncWrite + Sized,
    {
        split::split(self)
    }

    /// Wraps an [`AsyncRead`] in a compatibility wrapper that allows it to be
    /// used as a futures 0.1 / tokio-io 0.1 `AsyncRead`. If the wrapped type
    /// implements [`AsyncWrite`] as well, the result will also implement the
    /// futures 0.1 / tokio 0.1 `AsyncWrite` trait.
    ///
    /// Requires the `io-compat` feature to enable.
    #[cfg(feature = "io-compat")]
    fn compat(self) -> Compat<Self>
        where Self: Sized,
    {
        Compat::new(self)
    }
}

impl<R: AsyncRead + ?Sized> AsyncReadExt for R {}

/// An extension trait which adds utility methods to `AsyncWrite` types.
pub trait AsyncWriteExt: AsyncWrite {
    /// Creates a future which will entirely flush this `AsyncWrite`.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(async_await, await_macro, futures_api)]
    /// # futures::executor::block_on(async {
    /// use futures::io::{AllowStdIo, AsyncWriteExt};
    /// use std::io::{BufWriter, Cursor};
    ///
    /// let mut output = [0u8; 5];
    ///
    /// {
    ///     let mut writer = Cursor::new(&mut output[..]);
    ///     let mut buffered = AllowStdIo::new(BufWriter::new(writer));
    ///     await!(buffered.write_all(&[1, 2]))?;
    ///     await!(buffered.write_all(&[3, 4]))?;
    ///     await!(buffered.flush())?;
    /// }
    ///
    /// assert_eq!(output, [1, 2, 3, 4, 0]);
    /// # Ok::<(), Box<std::error::Error>>(()) }).unwrap();
    /// ```
    fn flush(&mut self) -> Flush<'_, Self> {
        Flush::new(self)
    }

    /// Creates a future which will entirely close this `AsyncWrite`.
    fn close(&mut self) -> Close<'_, Self> {
        Close::new(self)
    }

    /// Write data into this object.
    ///
    /// Creates a future that will write the entire contents of the buffer `buf` into
    /// this `AsyncWrite`.
    ///
    /// The returned future will not complete until all the data has been written.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(async_await, await_macro, futures_api)]
    /// # futures::executor::block_on(async {
    /// use futures::io::AsyncWriteExt;
    /// use std::io::Cursor;
    ///
    /// let mut writer = Cursor::new([0u8; 5]);
    ///
    /// await!(writer.write_all(&[1, 2, 3, 4]))?;
    ///
    /// assert_eq!(writer.into_inner(), [1, 2, 3, 4, 0]);
    /// # Ok::<(), Box<std::error::Error>>(()) }).unwrap();
    /// ```
    fn write_all<'a>(&'a mut self, buf: &'a [u8]) -> WriteAll<'a, Self> {
        WriteAll::new(self, buf)
    }

    /// Wraps an [`AsyncWrite`] in a compatibility wrapper that allows it to be
    /// used as a futures 0.1 / tokio-io 0.1 `AsyncWrite`.
    /// Requires the `io-compat` feature to enable.
    #[cfg(feature = "io-compat")]
    fn compat_write(self) -> Compat<Self>
        where Self: Sized,
    {
        Compat::new(self)
    }
}

impl<W: AsyncWrite + ?Sized> AsyncWriteExt for W {}