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

use std::ptr;

use glib::{prelude::*, subclass::prelude::*, translate::*, Cast, Error};
use once_cell::sync::Lazy;

use crate::{Cancellable, IOStream, InputStream, OutputStream};

pub trait IOStreamImpl: ObjectImpl + IOStreamImplExt + Send {
    /// Gets the input stream for this object. This is used
    /// for reading.
    ///
    /// # Returns
    ///
    /// a [`InputStream`][crate::InputStream], owned by the [`IOStream`][crate::IOStream].
    /// Do not free.
    fn input_stream(&self) -> InputStream {
        self.parent_input_stream()
    }

    /// Gets the output stream for this object. This is used for
    /// writing.
    ///
    /// # Returns
    ///
    /// a [`OutputStream`][crate::OutputStream], owned by the [`IOStream`][crate::IOStream].
    /// Do not free.
    fn output_stream(&self) -> OutputStream {
        self.parent_output_stream()
    }

    fn close(&self, cancellable: Option<&Cancellable>) -> Result<(), Error> {
        self.parent_close(cancellable)
    }
}

mod sealed {
    pub trait Sealed {}
    impl<T: super::IOStreamImplExt> Sealed for T {}
}

pub trait IOStreamImplExt: sealed::Sealed + ObjectSubclass {
    fn parent_input_stream(&self) -> InputStream {
        unsafe {
            let data = Self::type_data();
            let parent_class = data.as_ref().parent_class() as *mut ffi::GIOStreamClass;
            let f = (*parent_class)
                .get_input_stream
                .expect("No parent class implementation for \"input_stream\"");
            from_glib_none(f(self.obj().unsafe_cast_ref::<IOStream>().to_glib_none().0))
        }
    }

    fn parent_output_stream(&self) -> OutputStream {
        unsafe {
            let data = Self::type_data();
            let parent_class = data.as_ref().parent_class() as *mut ffi::GIOStreamClass;
            let f = (*parent_class)
                .get_output_stream
                .expect("No parent class implementation for \"output_stream\"");
            from_glib_none(f(self.obj().unsafe_cast_ref::<IOStream>().to_glib_none().0))
        }
    }

    fn parent_close(&self, cancellable: Option<&Cancellable>) -> Result<(), Error> {
        unsafe {
            let data = Self::type_data();
            let parent_class = data.as_ref().parent_class() as *mut ffi::GIOStreamClass;
            let mut err = ptr::null_mut();
            if let Some(f) = (*parent_class).close_fn {
                if from_glib(f(
                    self.obj().unsafe_cast_ref::<IOStream>().to_glib_none().0,
                    cancellable.to_glib_none().0,
                    &mut err,
                )) {
                    Ok(())
                } else {
                    Err(from_glib_full(err))
                }
            } else {
                Ok(())
            }
        }
    }
}

impl<T: IOStreamImpl> IOStreamImplExt for T {}

unsafe impl<T: IOStreamImpl> IsSubclassable<T> for IOStream {
    fn class_init(class: &mut ::glib::Class<Self>) {
        Self::parent_class_init::<T>(class);

        let klass = class.as_mut();
        klass.get_input_stream = Some(stream_get_input_stream::<T>);
        klass.get_output_stream = Some(stream_get_output_stream::<T>);
        klass.close_fn = Some(stream_close::<T>);
    }
}

static OUTPUT_STREAM_QUARK: Lazy<glib::Quark> =
    Lazy::new(|| glib::Quark::from_str("gtk-rs-subclass-output-stream"));
static INPUT_STREAM_QUARK: Lazy<glib::Quark> =
    Lazy::new(|| glib::Quark::from_str("gtk-rs-subclass-input-stream"));

unsafe extern "C" fn stream_get_input_stream<T: IOStreamImpl>(
    ptr: *mut ffi::GIOStream,
) -> *mut ffi::GInputStream {
    let instance = &*(ptr as *mut T::Instance);
    let imp = instance.imp();

    let ret = imp.input_stream();

    let instance = imp.obj();
    // Ensure that a) the stream stays alive as long as the IO stream instance and
    // b) that the same stream is returned every time. This is a requirement by the
    // IO stream API.
    if let Some(old_stream) = instance.qdata::<InputStream>(*INPUT_STREAM_QUARK) {
        assert_eq!(
            old_stream.as_ref(),
            &ret,
            "Did not return same input stream again"
        );
    }
    instance.set_qdata(*INPUT_STREAM_QUARK, ret.clone());
    ret.to_glib_none().0
}

unsafe extern "C" fn stream_get_output_stream<T: IOStreamImpl>(
    ptr: *mut ffi::GIOStream,
) -> *mut ffi::GOutputStream {
    let instance = &*(ptr as *mut T::Instance);
    let imp = instance.imp();

    let ret = imp.output_stream();

    let instance = imp.obj();
    // Ensure that a) the stream stays alive as long as the IO stream instance and
    // b) that the same stream is returned every time. This is a requirement by the
    // IO stream API.
    if let Some(old_stream) = instance.qdata::<OutputStream>(*OUTPUT_STREAM_QUARK) {
        assert_eq!(
            old_stream.as_ref(),
            &ret,
            "Did not return same output stream again"
        );
    }
    instance.set_qdata(*OUTPUT_STREAM_QUARK, ret.clone());
    ret.to_glib_none().0
}

unsafe extern "C" fn stream_close<T: IOStreamImpl>(
    ptr: *mut ffi::GIOStream,
    cancellable: *mut ffi::GCancellable,
    err: *mut *mut glib::ffi::GError,
) -> glib::ffi::gboolean {
    let instance = &*(ptr as *mut T::Instance);
    let imp = instance.imp();

    match imp.close(
        Option::<Cancellable>::from_glib_borrow(cancellable)
            .as_ref()
            .as_ref(),
    ) {
        Ok(_) => glib::ffi::GTRUE,
        Err(e) => {
            if !err.is_null() {
                *err = e.into_glib_ptr();
            }
            glib::ffi::GFALSE
        }
    }
}