// Copyright (C) 2017-2018 Baidu, Inc. All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
//  * Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//  * Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in
//    the documentation and/or other materials provided with the
//    distribution.
//  * Neither the name of Baidu, Inc., nor the names of its
//    contributors may be used to endorse or promote products derived
//    from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

use io::prelude::*;
use io::lazy::LazyStatic;
use io::{self, Initializer, BufReader, LineWriter};
use sync::{SgxMutex, SgxMutexGuard, SgxReentrantMutex, SgxReentrantMutexGuard};
use sys::stdio;
use core::cell::RefCell;
use core::fmt;
use alloc::sync::Arc;

/// A handle to a raw instance of the standard input stream of this process.
///
/// This handle is not synchronized or buffered in any fashion. Constructed via
/// the `std::io::stdio::stdin_raw` function.
struct StdinRaw(stdio::Stdin);

/// A handle to a raw instance of the standard output stream of this process.
///
/// This handle is not synchronized or buffered in any fashion. Constructed via
/// the `std::io::stdio::stdout_raw` function.
struct StdoutRaw(stdio::Stdout);

/// A handle to a raw instance of the standard output stream of this process.
///
/// This handle is not synchronized or buffered in any fashion. Constructed via
/// the `std::io::stdio::stderr_raw` function.
struct StderrRaw(stdio::Stderr);

/// Constructs a new raw handle to the standard input of this process.
///
/// The returned handle does not interact with any other handles created nor
/// handles returned by `std::io::stdin`. Data buffered by the `std::io::stdin`
/// handles is **not** available to raw handles returned from this function.
///
/// The returned handle has no external synchronization or buffering.
fn stdin_raw() -> io::Result<StdinRaw> { stdio::Stdin::new().map(StdinRaw) }

/// Constructs a new raw handle to the standard output stream of this process.
///
/// The returned handle does not interact with any other handles created nor
/// handles returned by `std::io::stdout`. Note that data is buffered by the
/// `std::io::stdout` handles so writes which happen via this raw handle may
/// appear before previous writes.
///
/// The returned handle has no external synchronization or buffering layered on
/// top.
fn stdout_raw() -> io::Result<StdoutRaw> { stdio::Stdout::new().map(StdoutRaw) }

/// Constructs a new raw handle to the standard error stream of this process.
///
/// The returned handle does not interact with any other handles created nor
/// handles returned by `std::io::stderr`.
///
/// The returned handle has no external synchronization or buffering layered on
/// top.
fn stderr_raw() -> io::Result<StderrRaw> { stdio::Stderr::new().map(StderrRaw) }

impl Read for StdinRaw {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { self.0.read(buf) }

    #[inline]
    unsafe fn initializer(&self) -> Initializer {
        Initializer::nop()
    }
}
impl Write for StdoutRaw {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
    fn flush(&mut self) -> io::Result<()> { self.0.flush() }
}
impl Write for StderrRaw {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
    fn flush(&mut self) -> io::Result<()> { self.0.flush() }
}

enum Maybe<T> {
    Real(T),
    Fake,
}

impl<W: io::Write> io::Write for Maybe<W> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        match *self {
            Maybe::Real(ref mut w) => handle_ebadf(w.write(buf), buf.len()),
            Maybe::Fake => Ok(buf.len())
        }
    }

    fn flush(&mut self) -> io::Result<()> {
        match *self {
            Maybe::Real(ref mut w) => handle_ebadf(w.flush(), ()),
            Maybe::Fake => Ok(())
        }
    }
}

impl<R: io::Read> io::Read for Maybe<R> {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        match *self {
            Maybe::Real(ref mut r) => handle_ebadf(r.read(buf), 0),
            Maybe::Fake => Ok(0)
        }
    }
}

fn handle_ebadf<T>(r: io::Result<T>, default: T) -> io::Result<T> {
    match r {
        Err(ref e) if stdio::is_ebadf(e) => Ok(default),
        r => r
    }
}

/// A handle to the standard input stream of a process.
///
/// Each handle is a shared reference to a global buffer of input data to this
/// process. A handle can be `lock`'d to gain full access to [`BufRead`] methods
/// (e.g. `.lines()`). Reads to this handle are otherwise locked with respect
/// to other reads.
///
/// This handle implements the `Read` trait, but beware that concurrent reads
/// of `Stdin` must be executed with care.
///
/// Created by the [`io::stdin`] method.
///
/// [`io::stdin`]: fn.stdin.html
/// [`BufRead`]: trait.BufRead.html
pub struct Stdin {
    inner: Arc<SgxMutex<BufReader<Maybe<StdinRaw>>>>,
}

/// A locked reference to the `Stdin` handle.
///
/// This handle implements both the [`Read`] and [`BufRead`] traits, and
/// is constructed via the [`Stdin::lock`] method.
///
/// [`Read`]: trait.Read.html
/// [`BufRead`]: trait.BufRead.html
/// [`Stdin::lock`]: struct.Stdin.html#method.lock
pub struct StdinLock<'a> {
    inner: SgxMutexGuard<'a, BufReader<Maybe<StdinRaw>>>,
}

/// Constructs a new handle to the standard input of the current process.
///
/// Each handle returned is a reference to a shared global buffer whose access
/// is synchronized via a mutex. If you need more explicit control over
/// locking, see the [`lock() method`][lock].
///
/// [lock]: struct.Stdin.html#method.lock
///
pub fn stdin() -> Stdin {
    static INSTANCE: LazyStatic<SgxMutex<BufReader<Maybe<StdinRaw>>>> = LazyStatic::new(stdin_init);
    return Stdin {
        inner: INSTANCE.get().expect("cannot access stdin during shutdown"),
    };

    fn stdin_init() -> Arc<SgxMutex<BufReader<Maybe<StdinRaw>>>> {
        let stdin = match stdin_raw() {
            Ok(stdin) => Maybe::Real(stdin),
            _ => Maybe::Fake
        };

        Arc::new(SgxMutex::new(BufReader::with_capacity(stdio::STDIN_BUF_SIZE, stdin)))
    }
}

impl Stdin {
    /// Locks this handle to the standard input stream, returning a readable
    /// guard.
    ///
    /// The lock is released when the returned lock goes out of scope. The
    /// returned guard also implements the [`Read`] and [`BufRead`] traits for
    /// accessing the underlying data.
    ///
    /// [`Read`]: trait.Read.html
    /// [`BufRead`]: trait.BufRead.html
    ///
    pub fn lock(&self) -> StdinLock {
        StdinLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
    }

    /// Locks this handle and reads a line of input into the specified buffer.
    ///
    /// For detailed semantics of this method, see the documentation on
    /// [`BufRead::read_line`].
    ///
    /// [`BufRead::read_line`]: trait.BufRead.html#method.read_line
    ///
    pub fn read_line(&self, buf: &mut String) -> io::Result<usize> {
        self.lock().read_line(buf)
    }
}

impl fmt::Debug for Stdin {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("Stdin { .. }")
    }
}

impl Read for Stdin {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.lock().read(buf)
    }
    #[inline]
    unsafe fn initializer(&self) -> Initializer {
        Initializer::nop()
    }
    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
        self.lock().read_to_end(buf)
    }
    fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
        self.lock().read_to_string(buf)
    }
    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
        self.lock().read_exact(buf)
    }
}

impl<'a> Read for StdinLock<'a> {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.inner.read(buf)
    }
    #[inline]
    unsafe fn initializer(&self) -> Initializer {
        Initializer::nop()
    }
}

impl<'a> BufRead for StdinLock<'a> {
    fn fill_buf(&mut self) -> io::Result<&[u8]> { self.inner.fill_buf() }
    fn consume(&mut self, n: usize) { self.inner.consume(n) }
}

impl<'a> fmt::Debug for StdinLock<'a> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("StdinLock { .. }")
    }
}

/// A handle to the global standard output stream of the current process.
///
/// Each handle shares a global buffer of data to be written to the standard
/// output stream. Access is also synchronized via a lock and explicit control
/// over locking is available via the [`lock`] method.
///
/// Created by the [`io::stdout`] method.
///
/// [`lock`]: #method.lock
/// [`io::stdout`]: fn.stdout.html
pub struct Stdout {
    // FIXME: this should be LineWriter or BufWriter depending on the state of
    //        stdout (tty or not). Note that if this is not line buffered it
    //        should also flush-on-panic or some form of flush-on-abort.
    inner: Arc<SgxReentrantMutex<RefCell<LineWriter<Maybe<StdoutRaw>>>>>,
}

/// A locked reference to the `Stdout` handle.
///
/// This handle implements the [`Write`] trait, and is constructed via
/// the [`Stdout::lock`] method.
///
/// [`Write`]: trait.Write.html
/// [`Stdout::lock`]: struct.Stdout.html#method.lock
pub struct StdoutLock<'a> {
    inner: SgxReentrantMutexGuard<'a, RefCell<LineWriter<Maybe<StdoutRaw>>>>,
}

/// Constructs a new handle to the standard output of the current process.
///
/// Each handle returned is a reference to a shared global buffer whose access
/// is synchronized via a mutex. If you need more explicit control over
/// locking, see the [Stdout::lock] method.
///
/// [Stdout::lock]: struct.Stdout.html#method.lock
///
pub fn stdout() -> Stdout {
    static INSTANCE: LazyStatic<SgxReentrantMutex<RefCell<LineWriter<Maybe<StdoutRaw>>>>>
        = LazyStatic::new(stdout_init);
    return Stdout {
        inner: INSTANCE.get().expect("cannot access stdout during shutdown"),
    };

    fn stdout_init() -> Arc<SgxReentrantMutex<RefCell<LineWriter<Maybe<StdoutRaw>>>>> {
        let stdout = match stdout_raw() {
            Ok(stdout) => Maybe::Real(stdout),
            _ => Maybe::Fake,
        };
        Arc::new(SgxReentrantMutex::new(RefCell::new(LineWriter::new(stdout))))
    }
}

impl Stdout {
    /// Locks this handle to the standard output stream, returning a writable
    /// guard.
    ///
    /// The lock is released when the returned lock goes out of scope. The
    /// returned guard also implements the `Write` trait for writing data.
    ///
    pub fn lock(&self) -> StdoutLock {
        StdoutLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
    }
}

impl fmt::Debug for Stdout {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("Stdout { .. }")
    }
}

impl Write for Stdout {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.lock().write(buf)
    }
    fn flush(&mut self) -> io::Result<()> {
        self.lock().flush()
    }
    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        self.lock().write_all(buf)
    }
    fn write_fmt(&mut self, args: fmt::Arguments) -> io::Result<()> {
        self.lock().write_fmt(args)
    }
}

impl<'a> Write for StdoutLock<'a> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.inner.borrow_mut().write(buf)
    }
    fn flush(&mut self) -> io::Result<()> {
        self.inner.borrow_mut().flush()
    }
}

impl<'a> fmt::Debug for StdoutLock<'a> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("StdoutLock { .. }")
    }
}

/// A handle to the standard error stream of a process.
///
/// For more information, see the [`io::stderr`] method.
///
/// [`io::stderr`]: fn.stderr.html
pub struct Stderr {
    inner: Arc<SgxReentrantMutex<RefCell<Maybe<StderrRaw>>>>,
}

/// A locked reference to the `Stderr` handle.
///
/// This handle implements the `Write` trait and is constructed via
/// the [`Stderr::lock`] method.
///
/// [`Stderr::lock`]: struct.Stderr.html#method.lock
pub struct StderrLock<'a> {
    inner: SgxReentrantMutexGuard<'a, RefCell<Maybe<StderrRaw>>>,
}

/// Constructs a new handle to the standard error of the current process.
///
/// This handle is not buffered.
///
pub fn stderr() -> Stderr {
    static INSTANCE: LazyStatic<SgxReentrantMutex<RefCell<Maybe<StderrRaw>>>> = LazyStatic::new(stderr_init);
    return Stderr {
        inner: INSTANCE.get().expect("cannot access stderr during shutdown"),
    };

    fn stderr_init() -> Arc<SgxReentrantMutex<RefCell<Maybe<StderrRaw>>>> {
        let stderr = match stderr_raw() {
            Ok(stderr) => Maybe::Real(stderr),
            _ => Maybe::Fake,
        };
        Arc::new(SgxReentrantMutex::new(RefCell::new(stderr)))
    }
}

impl Stderr {
    /// Locks this handle to the standard error stream, returning a writable
    /// guard.
    ///
    /// The lock is released when the returned lock goes out of scope. The
    /// returned guard also implements the `Write` trait for writing data.
    ///
    pub fn lock(&self) -> StderrLock {
        StderrLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
    }
}

impl fmt::Debug for Stderr {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("Stderr { .. }")
    }
}

impl Write for Stderr {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.lock().write(buf)
    }
    fn flush(&mut self) -> io::Result<()> {
        self.lock().flush()
    }
    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        self.lock().write_all(buf)
    }
    fn write_fmt(&mut self, args: fmt::Arguments) -> io::Result<()> {
        self.lock().write_fmt(args)
    }
}

impl<'a> Write for StderrLock<'a> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.inner.borrow_mut().write(buf)
    }
    fn flush(&mut self) -> io::Result<()> {
        self.inner.borrow_mut().flush()
    }
}

impl<'a> fmt::Debug for StderrLock<'a> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("StderrLock { .. }")
    }
}

/// Write `args` to output stream `local_s` if possible, `global_s`
/// otherwise. `label` identifies the stream in a panic message.
///
/// This function is used to print error messages, so it takes extra
/// care to avoid causing a panic when `local_stream` is unusable.
/// For instance, if the TLS key for the local stream is uninitialized
/// or already destroyed, or if the local stream is locked by another
/// thread, it will just fall back to the global stream.
///
/// However, if the actual I/O causes an error, this function does panic.
fn print_to<T>(args: fmt::Arguments,
               global_s: fn() -> T,
               label: &str) where T: Write {

    let result = global_s().write_fmt(args);
    if let Err(e) = result {
        panic!("failed printing to {}: {}", label, e);
    }
}

pub fn _print(args: fmt::Arguments) {
    print_to(args, stdout, "stdout");
}

pub fn _eprint(args: fmt::Arguments) {

    print_to(args, stderr, "stderr");
}