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

use std::{future, pin::Pin, ptr};

use glib::{GString, translate::*};

use crate::{Drop, ffi, prelude::*};

impl Drop {
    #[doc(alias = "gdk_drop_read_async")]
    pub fn read_async<Q: FnOnce(Result<(gio::InputStream, GString), glib::Error>) + 'static>(
        &self,
        mime_types: &[&str],
        io_priority: glib::Priority,
        cancellable: Option<&impl IsA<gio::Cancellable>>,
        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 user_data: Box<glib::thread_guard::ThreadGuard<Q>> =
            Box::new(glib::thread_guard::ThreadGuard::new(callback));
        unsafe extern "C" fn read_async_trampoline<
            Q: FnOnce(Result<(gio::InputStream, GString), glib::Error>) + 'static,
        >(
            _source_object: *mut glib::gobject_ffi::GObject,
            res: *mut gio::ffi::GAsyncResult,
            user_data: glib::ffi::gpointer,
        ) {
            unsafe {
                let mut error = ptr::null_mut();
                let mut out_mime_type = ptr::null();
                let ret = ffi::gdk_drop_read_finish(
                    _source_object as *mut _,
                    res,
                    &mut out_mime_type,
                    &mut error,
                );
                let result = if error.is_null() {
                    Ok((from_glib_full(ret), from_glib_none(out_mime_type)))
                } else {
                    Err(from_glib_full(error))
                };
                let callback: Box<glib::thread_guard::ThreadGuard<Q>> =
                    Box::from_raw(user_data as *mut _);
                let callback = callback.into_inner();
                callback(result);
            }
        }
        let callback = read_async_trampoline::<Q>;
        unsafe {
            ffi::gdk_drop_read_async(
                self.to_glib_none().0,
                mime_types.to_glib_none().0,
                io_priority.into_glib(),
                cancellable.map(|p| p.as_ref()).to_glib_none().0,
                Some(callback),
                Box::into_raw(user_data) as *mut _,
            );
        }
    }

    #[allow(clippy::type_complexity)]
    pub fn read_future(
        &self,
        mime_types: &[&str],
        io_priority: glib::Priority,
    ) -> Pin<
        Box<
            dyn future::Future<Output = Result<(gio::InputStream, GString), glib::Error>> + 'static,
        >,
    > {
        let mime_types = mime_types
            .iter()
            .copied()
            .map(String::from)
            .collect::<Vec<_>>();
        Box::pin(gio::GioFuture::new(self, move |obj, cancellable, send| {
            let mime_types = mime_types.iter().map(|s| s.as_str()).collect::<Vec<_>>();
            obj.read_async(&mime_types, io_priority, Some(cancellable), move |res| {
                send.resolve(res);
            });
        }))
    }
}
