// Take a look at the license at the top of the repository in the LICENSE file.

use std::{io, mem, pin::Pin, ptr};

use glib::{prelude::*, translate::*, Priority};

#[cfg(any(feature = "v2_60", feature = "dox"))]
use crate::OutputVector;
use crate::{error::to_std_io_result, prelude::*, Cancellable, OutputStream, Seekable};

pub trait OutputStreamExtManual: Sized + OutputStreamExt {
    /// Request an asynchronous write of `count` bytes from `buffer` into
    /// the stream. When the operation is finished `callback` will be called.
    /// You can then call `g_output_stream_write_finish()` to get the result of the
    /// operation.
    ///
    /// During an async request no other sync and async calls are allowed,
    /// and will result in [`IOErrorEnum::Pending`][crate::IOErrorEnum::Pending] errors.
    ///
    /// A value of `count` larger than `G_MAXSSIZE` will cause a
    /// [`IOErrorEnum::InvalidArgument`][crate::IOErrorEnum::InvalidArgument] error.
    ///
    /// On success, the number of bytes written will be passed to the
    /// `callback`. It is not an error if this is not the same as the
    /// requested size, as it can happen e.g. on a partial I/O error,
    /// but generally we try to write as many bytes as requested.
    ///
    /// You are guaranteed that this method will never fail with
    /// [`IOErrorEnum::WouldBlock`][crate::IOErrorEnum::WouldBlock] - if `self` can't accept more data, the
    /// method will just wait until this changes.
    ///
    /// Any outstanding I/O request with higher priority (lower numerical
    /// value) will be executed before an outstanding request with lower
    /// priority. Default priority is `G_PRIORITY_DEFAULT`.
    ///
    /// The asynchronous methods have a default fallback that uses threads
    /// to implement asynchronicity, so they are optional for inheriting
    /// classes. However, if you override one you must override all.
    ///
    /// For the synchronous, blocking version of this function, see
    /// [`OutputStreamExt::write()`][crate::prelude::OutputStreamExt::write()].
    ///
    /// Note that no copy of `buffer` will be made, so it must stay valid
    /// until `callback` is called. See [`OutputStreamExt::write_bytes_async()`][crate::prelude::OutputStreamExt::write_bytes_async()]
    /// for a [`glib::Bytes`][crate::glib::Bytes] version that will automatically hold a reference to
    /// the contents (without copying) for the duration of the call.
    /// ## `buffer`
    /// the buffer containing the data to write.
    /// ## `io_priority`
    /// the io priority of the request.
    /// ## `cancellable`
    /// optional [`Cancellable`][crate::Cancellable] object, [`None`] to ignore.
    /// ## `callback`
    /// callback to call when the request is satisfied
    #[doc(alias = "g_output_stream_write_async")]
    fn write_async<
        B: AsRef<[u8]> + Send + 'static,
        Q: FnOnce(Result<(B, usize), (B, glib::Error)>) + 'static,
        C: IsA<Cancellable>,
    >(
        &self,
        buffer: B,
        io_priority: Priority,
        cancellable: Option<&C>,
        callback: Q,
    );

    /// Tries to write `count` bytes from `buffer` into the stream. Will block
    /// during the operation.
    ///
    /// This function is similar to [`OutputStreamExt::write()`][crate::prelude::OutputStreamExt::write()], except it tries to
    /// write as many bytes as requested, only stopping on an error.
    ///
    /// On a successful write of `count` bytes, [`true`] is returned, and `bytes_written`
    /// is set to `count`.
    ///
    /// If there is an error during the operation [`false`] is returned and `error`
    /// is set to indicate the error status.
    ///
    /// As a special exception to the normal conventions for functions that
    /// use [`glib::Error`][crate::glib::Error], if this function returns [`false`] (and sets `error`) then
    /// `bytes_written` will be set to the number of bytes that were
    /// successfully written before the error was encountered. This
    /// functionality is only available from C. If you need it from another
    /// language then you must write your own loop around
    /// [`OutputStreamExt::write()`][crate::prelude::OutputStreamExt::write()].
    /// ## `buffer`
    /// the buffer containing the data to write.
    /// ## `cancellable`
    /// optional [`Cancellable`][crate::Cancellable] object, [`None`] to ignore.
    ///
    /// # Returns
    ///
    /// [`true`] on success, [`false`] if there was an error
    ///
    /// ## `bytes_written`
    /// location to store the number of bytes that was
    ///  written to the stream
    #[doc(alias = "g_output_stream_write_all")]
    fn write_all<C: IsA<Cancellable>>(
        &self,
        buffer: &[u8],
        cancellable: Option<&C>,
    ) -> Result<(usize, Option<glib::Error>), glib::Error>;

    /// Request an asynchronous write of `count` bytes from `buffer` into
    /// the stream. When the operation is finished `callback` will be called.
    /// You can then call `g_output_stream_write_all_finish()` to get the result of the
    /// operation.
    ///
    /// This is the asynchronous version of [`OutputStreamExtManual::write_all()`][crate::prelude::OutputStreamExtManual::write_all()].
    ///
    /// Call `g_output_stream_write_all_finish()` to collect the result.
    ///
    /// Any outstanding I/O request with higher priority (lower numerical
    /// value) will be executed before an outstanding request with lower
    /// priority. Default priority is `G_PRIORITY_DEFAULT`.
    ///
    /// Note that no copy of `buffer` will be made, so it must stay valid
    /// until `callback` is called.
    /// ## `buffer`
    /// the buffer containing the data to write
    /// ## `io_priority`
    /// the io priority of the request
    /// ## `cancellable`
    /// optional [`Cancellable`][crate::Cancellable] object, [`None`] to ignore
    /// ## `callback`
    /// callback to call when the request is satisfied
    #[doc(alias = "g_output_stream_write_all_async")]
    fn write_all_async<
        B: AsRef<[u8]> + Send + 'static,
        Q: FnOnce(Result<(B, usize, Option<glib::Error>), (B, glib::Error)>) + 'static,
        C: IsA<Cancellable>,
    >(
        &self,
        buffer: B,
        io_priority: Priority,
        cancellable: Option<&C>,
        callback: Q,
    );

    fn write_future<B: AsRef<[u8]> + Send + 'static>(
        &self,
        buffer: B,
        io_priority: Priority,
    ) -> Pin<Box<dyn std::future::Future<Output = Result<(B, usize), (B, glib::Error)>> + 'static>>;

    fn write_all_future<B: AsRef<[u8]> + Send + 'static>(
        &self,
        buffer: B,
        io_priority: Priority,
    ) -> Pin<
        Box<
            dyn std::future::Future<
                    Output = Result<(B, usize, Option<glib::Error>), (B, glib::Error)>,
                > + 'static,
        >,
    >;

    /// Tries to write the bytes contained in the `n_vectors` `vectors` into the
    /// stream. Will block during the operation.
    ///
    /// If `n_vectors` is 0 or the sum of all bytes in `vectors` is 0, returns 0 and
    /// does nothing.
    ///
    /// On success, the number of bytes written to the stream is returned.
    /// It is not an error if this is not the same as the requested size, as it
    /// can happen e.g. on a partial I/O error, or if there is not enough
    /// storage in the stream. All writes block until at least one byte
    /// is written or an error occurs; 0 is never returned (unless
    /// `n_vectors` is 0 or the sum of all bytes in `vectors` is 0).
    ///
    /// If `cancellable` is not [`None`], then the operation can be cancelled by
    /// triggering the cancellable object from another thread. If the operation
    /// was cancelled, the error [`IOErrorEnum::Cancelled`][crate::IOErrorEnum::Cancelled] will be returned. If an
    /// operation was partially finished when the operation was cancelled the
    /// partial result will be returned, without an error.
    ///
    /// Some implementations of [`OutputStreamExtManual::writev()`][crate::prelude::OutputStreamExtManual::writev()] may have limitations on the
    /// aggregate buffer size, and will return [`IOErrorEnum::InvalidArgument`][crate::IOErrorEnum::InvalidArgument] if these
    /// are exceeded. For example, when writing to a local file on UNIX platforms,
    /// the aggregate buffer size must not exceed `G_MAXSSIZE` bytes.
    /// ## `vectors`
    /// the buffer containing the `GOutputVectors` to write.
    /// ## `cancellable`
    /// optional cancellable object
    ///
    /// # Returns
    ///
    /// [`true`] on success, [`false`] if there was an error
    ///
    /// ## `bytes_written`
    /// location to store the number of bytes that were
    ///  written to the stream
    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    #[doc(alias = "g_output_stream_writev")]
    fn writev(
        &self,
        vectors: &[OutputVector],
        cancellable: Option<&impl IsA<Cancellable>>,
    ) -> Result<usize, glib::Error>;

    /// Request an asynchronous write of the bytes contained in `n_vectors` `vectors` into
    /// the stream. When the operation is finished `callback` will be called.
    /// You can then call `g_output_stream_writev_finish()` to get the result of the
    /// operation.
    ///
    /// During an async request no other sync and async calls are allowed,
    /// and will result in [`IOErrorEnum::Pending`][crate::IOErrorEnum::Pending] errors.
    ///
    /// On success, the number of bytes written will be passed to the
    /// `callback`. It is not an error if this is not the same as the
    /// requested size, as it can happen e.g. on a partial I/O error,
    /// but generally we try to write as many bytes as requested.
    ///
    /// You are guaranteed that this method will never fail with
    /// [`IOErrorEnum::WouldBlock`][crate::IOErrorEnum::WouldBlock] — if `self` can't accept more data, the
    /// method will just wait until this changes.
    ///
    /// Any outstanding I/O request with higher priority (lower numerical
    /// value) will be executed before an outstanding request with lower
    /// priority. Default priority is `G_PRIORITY_DEFAULT`.
    ///
    /// The asynchronous methods have a default fallback that uses threads
    /// to implement asynchronicity, so they are optional for inheriting
    /// classes. However, if you override one you must override all.
    ///
    /// For the synchronous, blocking version of this function, see
    /// [`OutputStreamExtManual::writev()`][crate::prelude::OutputStreamExtManual::writev()].
    ///
    /// Note that no copy of `vectors` will be made, so it must stay valid
    /// until `callback` is called.
    /// ## `vectors`
    /// the buffer containing the `GOutputVectors` to write.
    /// ## `io_priority`
    /// the I/O priority of the request.
    /// ## `cancellable`
    /// optional [`Cancellable`][crate::Cancellable] object, [`None`] to ignore.
    /// ## `callback`
    /// callback to call when the request is satisfied
    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    #[doc(alias = "g_output_stream_writev_async")]
    fn writev_async<
        B: AsRef<[u8]> + Send + 'static,
        P: FnOnce(Result<(Vec<B>, usize), (Vec<B>, glib::Error)>) + 'static,
    >(
        &self,
        vectors: impl IntoIterator<Item = B> + 'static,
        io_priority: glib::Priority,
        cancellable: Option<&impl IsA<Cancellable>>,
        callback: P,
    );

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn writev_future<B: AsRef<[u8]> + Send + 'static>(
        &self,
        vectors: impl IntoIterator<Item = B> + 'static,
        io_priority: glib::Priority,
    ) -> Pin<
        Box<
            dyn std::future::Future<Output = Result<(Vec<B>, usize), (Vec<B>, glib::Error)>>
                + 'static,
        >,
    >;

    /// Tries to write the bytes contained in the `n_vectors` `vectors` into the
    /// stream. Will block during the operation.
    ///
    /// This function is similar to [`OutputStreamExtManual::writev()`][crate::prelude::OutputStreamExtManual::writev()], except it tries to
    /// write as many bytes as requested, only stopping on an error.
    ///
    /// On a successful write of all `n_vectors` vectors, [`true`] is returned, and
    /// `bytes_written` is set to the sum of all the sizes of `vectors`.
    ///
    /// If there is an error during the operation [`false`] is returned and `error`
    /// is set to indicate the error status.
    ///
    /// As a special exception to the normal conventions for functions that
    /// use [`glib::Error`][crate::glib::Error], if this function returns [`false`] (and sets `error`) then
    /// `bytes_written` will be set to the number of bytes that were
    /// successfully written before the error was encountered. This
    /// functionality is only available from C. If you need it from another
    /// language then you must write your own loop around
    /// [`OutputStreamExt::write()`][crate::prelude::OutputStreamExt::write()].
    ///
    /// The content of the individual elements of `vectors` might be changed by this
    /// function.
    /// ## `vectors`
    /// the buffer containing the `GOutputVectors` to write.
    /// ## `cancellable`
    /// optional [`Cancellable`][crate::Cancellable] object, [`None`] to ignore.
    ///
    /// # Returns
    ///
    /// [`true`] on success, [`false`] if there was an error
    ///
    /// ## `bytes_written`
    /// location to store the number of bytes that were
    ///  written to the stream
    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    #[doc(alias = "g_output_stream_writev_all")]
    fn writev_all(
        &self,
        vectors: &[OutputVector],
        cancellable: Option<&impl IsA<Cancellable>>,
    ) -> Result<(usize, Option<glib::Error>), glib::Error>;

    /// Request an asynchronous write of the bytes contained in the `n_vectors` `vectors` into
    /// the stream. When the operation is finished `callback` will be called.
    /// You can then call `g_output_stream_writev_all_finish()` to get the result of the
    /// operation.
    ///
    /// This is the asynchronous version of [`OutputStreamExtManual::writev_all()`][crate::prelude::OutputStreamExtManual::writev_all()].
    ///
    /// Call `g_output_stream_writev_all_finish()` to collect the result.
    ///
    /// Any outstanding I/O request with higher priority (lower numerical
    /// value) will be executed before an outstanding request with lower
    /// priority. Default priority is `G_PRIORITY_DEFAULT`.
    ///
    /// Note that no copy of `vectors` will be made, so it must stay valid
    /// until `callback` is called. The content of the individual elements
    /// of `vectors` might be changed by this function.
    /// ## `vectors`
    /// the buffer containing the `GOutputVectors` to write.
    /// ## `io_priority`
    /// the I/O priority of the request
    /// ## `cancellable`
    /// optional [`Cancellable`][crate::Cancellable] object, [`None`] to ignore
    /// ## `callback`
    /// callback to call when the request is satisfied
    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    #[doc(alias = "g_output_stream_writev_all_async")]
    fn writev_all_async<
        B: AsRef<[u8]> + Send + 'static,
        P: FnOnce(Result<(Vec<B>, usize, Option<glib::Error>), (Vec<B>, glib::Error)>) + 'static,
    >(
        &self,
        vectors: impl IntoIterator<Item = B> + 'static,
        io_priority: glib::Priority,
        cancellable: Option<&impl IsA<Cancellable>>,
        callback: P,
    );

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn writev_all_future<B: AsRef<[u8]> + Send + 'static>(
        &self,
        vectors: impl IntoIterator<Item = B> + 'static,
        io_priority: glib::Priority,
    ) -> Pin<
        Box<
            dyn std::future::Future<
                    Output = Result<(Vec<B>, usize, Option<glib::Error>), (Vec<B>, glib::Error)>,
                > + 'static,
        >,
    >;

    fn into_write(self) -> OutputStreamWrite<Self>
    where
        Self: IsA<OutputStream>,
    {
        OutputStreamWrite(self)
    }
}

impl<O: IsA<OutputStream>> OutputStreamExtManual for O {
    fn write_async<
        B: AsRef<[u8]> + Send + 'static,
        Q: FnOnce(Result<(B, usize), (B, glib::Error)>) + 'static,
        C: IsA<Cancellable>,
    >(
        &self,
        buffer: B,
        io_priority: Priority,
        cancellable: Option<&C>,
        callback: Q,
    ) {
        let main_context = glib::MainContext::ref_thread_default();
        let is_main_context_owner = main_context.is_owner();
        let has_acquired_main_context = (!is_main_context_owner)
            .then(|| main_context.acquire().ok())
            .flatten();
        assert!(
            is_main_context_owner || has_acquired_main_context.is_some(),
            "Async operations only allowed if the thread is owning the MainContext"
        );

        let cancellable = cancellable.map(|c| c.as_ref());
        let gcancellable = cancellable.to_glib_none();
        let user_data: Box<(glib::thread_guard::ThreadGuard<Q>, B)> =
            Box::new((glib::thread_guard::ThreadGuard::new(callback), buffer));
        // Need to do this after boxing as the contents pointer might change by moving into the box
        let (count, buffer_ptr) = {
            let buffer = &user_data.1;
            let slice = buffer.as_ref();
            (slice.len(), slice.as_ptr())
        };
        unsafe extern "C" fn write_async_trampoline<
            B: AsRef<[u8]> + Send + 'static,
            Q: FnOnce(Result<(B, usize), (B, glib::Error)>) + 'static,
        >(
            _source_object: *mut glib::gobject_ffi::GObject,
            res: *mut ffi::GAsyncResult,
            user_data: glib::ffi::gpointer,
        ) {
            let user_data: Box<(glib::thread_guard::ThreadGuard<Q>, B)> =
                Box::from_raw(user_data as *mut _);
            let (callback, buffer) = *user_data;
            let callback = callback.into_inner();

            let mut error = ptr::null_mut();
            let ret = ffi::g_output_stream_write_finish(_source_object as *mut _, res, &mut error);
            let result = if error.is_null() {
                Ok((buffer, ret as usize))
            } else {
                Err((buffer, from_glib_full(error)))
            };
            callback(result);
        }
        let callback = write_async_trampoline::<B, Q>;
        unsafe {
            ffi::g_output_stream_write_async(
                self.as_ref().to_glib_none().0,
                mut_override(buffer_ptr),
                count,
                io_priority.into_glib(),
                gcancellable.0,
                Some(callback),
                Box::into_raw(user_data) as *mut _,
            );
        }
    }

    fn write_all<C: IsA<Cancellable>>(
        &self,
        buffer: &[u8],
        cancellable: Option<&C>,
    ) -> Result<(usize, Option<glib::Error>), glib::Error> {
        let cancellable = cancellable.map(|c| c.as_ref());
        let gcancellable = cancellable.to_glib_none();
        let count = buffer.len();
        unsafe {
            let mut bytes_written = mem::MaybeUninit::uninit();
            let mut error = ptr::null_mut();
            let _ = ffi::g_output_stream_write_all(
                self.as_ref().to_glib_none().0,
                buffer.to_glib_none().0,
                count,
                bytes_written.as_mut_ptr(),
                gcancellable.0,
                &mut error,
            );

            let bytes_written = bytes_written.assume_init();
            if error.is_null() {
                Ok((bytes_written, None))
            } else if bytes_written != 0 {
                Ok((bytes_written, Some(from_glib_full(error))))
            } else {
                Err(from_glib_full(error))
            }
        }
    }

    fn write_all_async<
        B: AsRef<[u8]> + Send + 'static,
        Q: FnOnce(Result<(B, usize, Option<glib::Error>), (B, glib::Error)>) + 'static,
        C: IsA<Cancellable>,
    >(
        &self,
        buffer: B,
        io_priority: Priority,
        cancellable: Option<&C>,
        callback: Q,
    ) {
        let main_context = glib::MainContext::ref_thread_default();
        let is_main_context_owner = main_context.is_owner();
        let has_acquired_main_context = (!is_main_context_owner)
            .then(|| main_context.acquire().ok())
            .flatten();
        assert!(
            is_main_context_owner || has_acquired_main_context.is_some(),
            "Async operations only allowed if the thread is owning the MainContext"
        );

        let cancellable = cancellable.map(|c| c.as_ref());
        let gcancellable = cancellable.to_glib_none();
        let user_data: Box<(glib::thread_guard::ThreadGuard<Q>, B)> =
            Box::new((glib::thread_guard::ThreadGuard::new(callback), buffer));
        // Need to do this after boxing as the contents pointer might change by moving into the box
        let (count, buffer_ptr) = {
            let buffer = &user_data.1;
            let slice = buffer.as_ref();
            (slice.len(), slice.as_ptr())
        };
        unsafe extern "C" fn write_all_async_trampoline<
            B: AsRef<[u8]> + Send + 'static,
            Q: FnOnce(Result<(B, usize, Option<glib::Error>), (B, glib::Error)>) + 'static,
        >(
            _source_object: *mut glib::gobject_ffi::GObject,
            res: *mut ffi::GAsyncResult,
            user_data: glib::ffi::gpointer,
        ) {
            let user_data: Box<(glib::thread_guard::ThreadGuard<Q>, B)> =
                Box::from_raw(user_data as *mut _);
            let (callback, buffer) = *user_data;
            let callback = callback.into_inner();

            let mut error = ptr::null_mut();
            let mut bytes_written = mem::MaybeUninit::uninit();
            let _ = ffi::g_output_stream_write_all_finish(
                _source_object as *mut _,
                res,
                bytes_written.as_mut_ptr(),
                &mut error,
            );
            let bytes_written = bytes_written.assume_init();
            let result = if error.is_null() {
                Ok((buffer, bytes_written, None))
            } else if bytes_written != 0 {
                Ok((buffer, bytes_written, from_glib_full(error)))
            } else {
                Err((buffer, from_glib_full(error)))
            };
            callback(result);
        }
        let callback = write_all_async_trampoline::<B, Q>;
        unsafe {
            ffi::g_output_stream_write_all_async(
                self.as_ref().to_glib_none().0,
                mut_override(buffer_ptr),
                count,
                io_priority.into_glib(),
                gcancellable.0,
                Some(callback),
                Box::into_raw(user_data) as *mut _,
            );
        }
    }

    fn write_future<'a, B: AsRef<[u8]> + Send + 'static>(
        &self,
        buffer: B,
        io_priority: Priority,
    ) -> Pin<Box<dyn std::future::Future<Output = Result<(B, usize), (B, glib::Error)>> + 'static>>
    {
        Box::pin(crate::GioFuture::new(
            self,
            move |obj, cancellable, send| {
                obj.write_async(buffer, io_priority, Some(cancellable), move |res| {
                    send.resolve(res);
                });
            },
        ))
    }

    fn write_all_future<'a, B: AsRef<[u8]> + Send + 'static>(
        &self,
        buffer: B,
        io_priority: Priority,
    ) -> Pin<
        Box<
            dyn std::future::Future<
                    Output = Result<(B, usize, Option<glib::Error>), (B, glib::Error)>,
                > + 'static,
        >,
    > {
        Box::pin(crate::GioFuture::new(
            self,
            move |obj, cancellable, send| {
                obj.write_all_async(buffer, io_priority, Some(cancellable), move |res| {
                    send.resolve(res);
                });
            },
        ))
    }

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn writev(
        &self,
        vectors: &[OutputVector],
        cancellable: Option<&impl IsA<Cancellable>>,
    ) -> Result<usize, glib::Error> {
        unsafe {
            let mut error = ptr::null_mut();
            let mut bytes_written = mem::MaybeUninit::uninit();

            ffi::g_output_stream_writev(
                self.as_ref().to_glib_none().0,
                vectors.as_ptr() as *const _,
                vectors.len(),
                bytes_written.as_mut_ptr(),
                cancellable.map(|p| p.as_ref()).to_glib_none().0,
                &mut error,
            );
            if error.is_null() {
                Ok(bytes_written.assume_init())
            } else {
                Err(from_glib_full(error))
            }
        }
    }

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn writev_async<
        B: AsRef<[u8]> + Send + 'static,
        P: FnOnce(Result<(Vec<B>, usize), (Vec<B>, glib::Error)>) + 'static,
    >(
        &self,
        vectors: impl IntoIterator<Item = B> + 'static,
        io_priority: glib::Priority,
        cancellable: Option<&impl IsA<Cancellable>>,
        callback: P,
    ) {
        let main_context = glib::MainContext::ref_thread_default();
        let is_main_context_owner = main_context.is_owner();
        let has_acquired_main_context = (!is_main_context_owner)
            .then(|| main_context.acquire().ok())
            .flatten();
        assert!(
            is_main_context_owner || has_acquired_main_context.is_some(),
            "Async operations only allowed if the thread is owning the MainContext"
        );

        let cancellable = cancellable.map(|c| c.as_ref());
        let gcancellable = cancellable.to_glib_none();
        let buffers = vectors.into_iter().collect::<Vec<_>>();
        let vectors = buffers
            .iter()
            .map(|v| ffi::GOutputVector {
                buffer: v.as_ref().as_ptr() as *const _,
                size: v.as_ref().len(),
            })
            .collect::<Vec<_>>();
        let vectors_ptr = vectors.as_ptr();
        let num_vectors = vectors.len();
        let user_data: Box<(
            glib::thread_guard::ThreadGuard<P>,
            Vec<B>,
            Vec<ffi::GOutputVector>,
        )> = Box::new((
            glib::thread_guard::ThreadGuard::new(callback),
            buffers,
            vectors,
        ));

        unsafe extern "C" fn writev_async_trampoline<
            B: AsRef<[u8]> + Send + 'static,
            P: FnOnce(Result<(Vec<B>, usize), (Vec<B>, glib::Error)>) + 'static,
        >(
            _source_object: *mut glib::gobject_ffi::GObject,
            res: *mut ffi::GAsyncResult,
            user_data: glib::ffi::gpointer,
        ) {
            let user_data: Box<(
                glib::thread_guard::ThreadGuard<P>,
                Vec<B>,
                Vec<ffi::GOutputVector>,
            )> = Box::from_raw(user_data as *mut _);
            let (callback, buffers, _) = *user_data;
            let callback = callback.into_inner();

            let mut error = ptr::null_mut();
            let mut bytes_written = mem::MaybeUninit::uninit();
            ffi::g_output_stream_writev_finish(
                _source_object as *mut _,
                res,
                bytes_written.as_mut_ptr(),
                &mut error,
            );
            let bytes_written = bytes_written.assume_init();
            let result = if error.is_null() {
                Ok((buffers, bytes_written))
            } else {
                Err((buffers, from_glib_full(error)))
            };
            callback(result);
        }
        let callback = writev_async_trampoline::<B, P>;
        unsafe {
            ffi::g_output_stream_writev_async(
                self.as_ref().to_glib_none().0,
                vectors_ptr,
                num_vectors,
                io_priority.into_glib(),
                gcancellable.0,
                Some(callback),
                Box::into_raw(user_data) as *mut _,
            );
        }
    }

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn writev_future<B: AsRef<[u8]> + Send + 'static>(
        &self,
        vectors: impl IntoIterator<Item = B> + 'static,
        io_priority: glib::Priority,
    ) -> Pin<
        Box<
            dyn std::future::Future<Output = Result<(Vec<B>, usize), (Vec<B>, glib::Error)>>
                + 'static,
        >,
    > {
        Box::pin(crate::GioFuture::new(
            self,
            move |obj, cancellable, send| {
                obj.writev_async(vectors, io_priority, Some(cancellable), move |res| {
                    send.resolve(res);
                });
            },
        ))
    }

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn writev_all(
        &self,
        vectors: &[OutputVector],
        cancellable: Option<&impl IsA<Cancellable>>,
    ) -> Result<(usize, Option<glib::Error>), glib::Error> {
        unsafe {
            let mut error = ptr::null_mut();
            let mut bytes_written = mem::MaybeUninit::uninit();

            ffi::g_output_stream_writev_all(
                self.as_ref().to_glib_none().0,
                mut_override(vectors.as_ptr() as *const _),
                vectors.len(),
                bytes_written.as_mut_ptr(),
                cancellable.map(|p| p.as_ref()).to_glib_none().0,
                &mut error,
            );
            let bytes_written = bytes_written.assume_init();
            if error.is_null() {
                Ok((bytes_written, None))
            } else if bytes_written != 0 {
                Ok((bytes_written, Some(from_glib_full(error))))
            } else {
                Err(from_glib_full(error))
            }
        }
    }

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn writev_all_async<
        B: AsRef<[u8]> + Send + 'static,
        P: FnOnce(Result<(Vec<B>, usize, Option<glib::Error>), (Vec<B>, glib::Error)>) + 'static,
    >(
        &self,
        vectors: impl IntoIterator<Item = B> + 'static,
        io_priority: glib::Priority,
        cancellable: Option<&impl IsA<Cancellable>>,
        callback: P,
    ) {
        let main_context = glib::MainContext::ref_thread_default();
        let is_main_context_owner = main_context.is_owner();
        let has_acquired_main_context = (!is_main_context_owner)
            .then(|| main_context.acquire().ok())
            .flatten();
        assert!(
            is_main_context_owner || has_acquired_main_context.is_some(),
            "Async operations only allowed if the thread is owning the MainContext"
        );

        let cancellable = cancellable.map(|c| c.as_ref());
        let gcancellable = cancellable.to_glib_none();
        let buffers = vectors.into_iter().collect::<Vec<_>>();
        let vectors = buffers
            .iter()
            .map(|v| ffi::GOutputVector {
                buffer: v.as_ref().as_ptr() as *const _,
                size: v.as_ref().len(),
            })
            .collect::<Vec<_>>();
        let vectors_ptr = vectors.as_ptr();
        let num_vectors = vectors.len();
        let user_data: Box<(
            glib::thread_guard::ThreadGuard<P>,
            Vec<B>,
            Vec<ffi::GOutputVector>,
        )> = Box::new((
            glib::thread_guard::ThreadGuard::new(callback),
            buffers,
            vectors,
        ));

        unsafe extern "C" fn writev_all_async_trampoline<
            B: AsRef<[u8]> + Send + 'static,
            P: FnOnce(Result<(Vec<B>, usize, Option<glib::Error>), (Vec<B>, glib::Error)>) + 'static,
        >(
            _source_object: *mut glib::gobject_ffi::GObject,
            res: *mut ffi::GAsyncResult,
            user_data: glib::ffi::gpointer,
        ) {
            let user_data: Box<(
                glib::thread_guard::ThreadGuard<P>,
                Vec<B>,
                Vec<ffi::GOutputVector>,
            )> = Box::from_raw(user_data as *mut _);
            let (callback, buffers, _) = *user_data;
            let callback = callback.into_inner();

            let mut error = ptr::null_mut();
            let mut bytes_written = mem::MaybeUninit::uninit();
            ffi::g_output_stream_writev_all_finish(
                _source_object as *mut _,
                res,
                bytes_written.as_mut_ptr(),
                &mut error,
            );
            let bytes_written = bytes_written.assume_init();
            let result = if error.is_null() {
                Ok((buffers, bytes_written, None))
            } else if bytes_written != 0 {
                Ok((buffers, bytes_written, from_glib_full(error)))
            } else {
                Err((buffers, from_glib_full(error)))
            };
            callback(result);
        }
        let callback = writev_all_async_trampoline::<B, P>;
        unsafe {
            ffi::g_output_stream_writev_all_async(
                self.as_ref().to_glib_none().0,
                mut_override(vectors_ptr),
                num_vectors,
                io_priority.into_glib(),
                gcancellable.0,
                Some(callback),
                Box::into_raw(user_data) as *mut _,
            );
        }
    }

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn writev_all_future<B: AsRef<[u8]> + Send + 'static>(
        &self,
        vectors: impl IntoIterator<Item = B> + 'static,
        io_priority: glib::Priority,
    ) -> Pin<
        Box<
            dyn std::future::Future<
                    Output = Result<(Vec<B>, usize, Option<glib::Error>), (Vec<B>, glib::Error)>,
                > + 'static,
        >,
    > {
        Box::pin(crate::GioFuture::new(
            self,
            move |obj, cancellable, send| {
                obj.writev_all_async(vectors, io_priority, Some(cancellable), move |res| {
                    send.resolve(res);
                });
            },
        ))
    }
}

#[derive(Debug)]
pub struct OutputStreamWrite<T: IsA<OutputStream>>(T);

impl<T: IsA<OutputStream>> OutputStreamWrite<T> {
    pub fn into_output_stream(self) -> T {
        self.0
    }

    pub fn output_stream(&self) -> &T {
        &self.0
    }
}

impl<T: IsA<OutputStream>> io::Write for OutputStreamWrite<T> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        let result = self
            .0
            .as_ref()
            .write(buf, crate::Cancellable::NONE)
            .map(|size| size as usize);
        to_std_io_result(result)
    }

    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        let result = self
            .0
            .as_ref()
            .write_all(buf, crate::Cancellable::NONE)
            .and_then(|(_, e)| e.map(Err).unwrap_or(Ok(())));
        to_std_io_result(result)
    }

    #[cfg(any(feature = "v2_60", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2_60")))]
    fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize> {
        let vectors = bufs
            .iter()
            .map(|v| OutputVector::new(v))
            .collect::<smallvec::SmallVec<[_; 2]>>();
        let result = self.0.as_ref().writev(&vectors, crate::Cancellable::NONE);
        to_std_io_result(result)
    }

    fn flush(&mut self) -> io::Result<()> {
        let gio_result = self.0.as_ref().flush(crate::Cancellable::NONE);
        to_std_io_result(gio_result)
    }
}

impl<T: IsA<OutputStream> + IsA<Seekable>> io::Seek for OutputStreamWrite<T> {
    fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
        let (pos, type_) = match pos {
            io::SeekFrom::Start(pos) => (pos as i64, glib::SeekType::Set),
            io::SeekFrom::End(pos) => (pos, glib::SeekType::End),
            io::SeekFrom::Current(pos) => (pos, glib::SeekType::Cur),
        };
        let seekable: &Seekable = self.0.as_ref();
        let gio_result = seekable
            .seek(pos, type_, crate::Cancellable::NONE)
            .map(|_| seekable.tell() as u64);
        to_std_io_result(gio_result)
    }
}

#[cfg(test)]
mod tests {
    use std::io::Write;

    use glib::Bytes;

    #[cfg(feature = "v2_60")]
    use crate::OutputVector;
    use crate::{prelude::*, test_util::run_async, MemoryInputStream, MemoryOutputStream};

    #[test]
    fn splice_async() {
        let ret = run_async(|tx, l| {
            let input = MemoryInputStream::new();
            let b = Bytes::from_owned(vec![1, 2, 3]);
            input.add_bytes(&b);

            let strm = MemoryOutputStream::new_resizable();
            strm.splice_async(
                &input,
                crate::OutputStreamSpliceFlags::CLOSE_SOURCE,
                glib::PRIORITY_DEFAULT_IDLE,
                crate::Cancellable::NONE,
                move |ret| {
                    tx.send(ret).unwrap();
                    l.quit();
                },
            );
        });

        assert_eq!(ret.unwrap(), 3);
    }

    #[test]
    fn write_async() {
        let ret = run_async(|tx, l| {
            let strm = MemoryOutputStream::new_resizable();

            let buf = vec![1, 2, 3];
            strm.write_async(
                buf,
                glib::PRIORITY_DEFAULT_IDLE,
                crate::Cancellable::NONE,
                move |ret| {
                    tx.send(ret).unwrap();
                    l.quit();
                },
            );
        });

        let (buf, size) = ret.unwrap();
        assert_eq!(buf, vec![1, 2, 3]);
        assert_eq!(size, 3);
    }

    #[test]
    fn write_all_async() {
        let ret = run_async(|tx, l| {
            let strm = MemoryOutputStream::new_resizable();

            let buf = vec![1, 2, 3];
            strm.write_all_async(
                buf,
                glib::PRIORITY_DEFAULT_IDLE,
                crate::Cancellable::NONE,
                move |ret| {
                    tx.send(ret).unwrap();
                    l.quit();
                },
            );
        });

        let (buf, size, err) = ret.unwrap();
        assert_eq!(buf, vec![1, 2, 3]);
        assert_eq!(size, 3);
        assert!(err.is_none());
    }

    #[test]
    fn write_bytes_async() {
        let ret = run_async(|tx, l| {
            let strm = MemoryOutputStream::new_resizable();

            let b = Bytes::from_owned(vec![1, 2, 3]);
            strm.write_bytes_async(
                &b,
                glib::PRIORITY_DEFAULT_IDLE,
                crate::Cancellable::NONE,
                move |ret| {
                    tx.send(ret).unwrap();
                    l.quit();
                },
            );
        });

        assert_eq!(ret.unwrap(), 3);
    }

    #[test]
    fn std_io_write() {
        let b = Bytes::from_owned(vec![1, 2, 3]);
        let mut write = MemoryOutputStream::new_resizable().into_write();

        let ret = write.write(&b);

        let stream = write.into_output_stream();
        stream.close(crate::Cancellable::NONE).unwrap();
        assert_eq!(ret.unwrap(), 3);
        assert_eq!(stream.steal_as_bytes(), [1, 2, 3].as_ref());
    }

    #[test]
    fn into_output_stream() {
        let stream = MemoryOutputStream::new_resizable();
        let stream_clone = stream.clone();
        let stream = stream.into_write().into_output_stream();

        assert_eq!(stream, stream_clone);
    }

    #[test]
    #[cfg(feature = "v2_60")]
    fn writev() {
        let stream = MemoryOutputStream::new_resizable();

        let ret = stream.writev(
            &[OutputVector::new(&[1, 2, 3]), OutputVector::new(&[4, 5, 6])],
            crate::Cancellable::NONE,
        );
        assert_eq!(ret.unwrap(), 6);
        stream.close(crate::Cancellable::NONE).unwrap();
        assert_eq!(stream.steal_as_bytes(), [1, 2, 3, 4, 5, 6].as_ref());
    }

    #[test]
    #[cfg(feature = "v2_60")]
    fn writev_async() {
        let ret = run_async(|tx, l| {
            let strm = MemoryOutputStream::new_resizable();

            let strm_clone = strm.clone();
            strm.writev_async(
                [vec![1, 2, 3], vec![4, 5, 6]],
                glib::PRIORITY_DEFAULT_IDLE,
                crate::Cancellable::NONE,
                move |ret| {
                    tx.send(ret).unwrap();
                    strm_clone.close(crate::Cancellable::NONE).unwrap();
                    assert_eq!(strm_clone.steal_as_bytes(), [1, 2, 3, 4, 5, 6].as_ref());
                    l.quit();
                },
            );
        });

        let (buf, size) = ret.unwrap();
        assert_eq!(buf, [[1, 2, 3], [4, 5, 6]]);
        assert_eq!(size, 6);
    }

    #[test]
    #[cfg(feature = "v2_60")]
    fn writev_all_async() {
        let ret = run_async(|tx, l| {
            let strm = MemoryOutputStream::new_resizable();

            let strm_clone = strm.clone();
            strm.writev_all_async(
                [vec![1, 2, 3], vec![4, 5, 6]],
                glib::PRIORITY_DEFAULT_IDLE,
                crate::Cancellable::NONE,
                move |ret| {
                    tx.send(ret).unwrap();
                    strm_clone.close(crate::Cancellable::NONE).unwrap();
                    assert_eq!(strm_clone.steal_as_bytes(), [1, 2, 3, 4, 5, 6].as_ref());
                    l.quit();
                },
            );
        });

        let (buf, size, err) = ret.unwrap();
        assert_eq!(buf, [[1, 2, 3], [4, 5, 6]]);
        assert_eq!(size, 6);
        assert!(err.is_none());
    }
}