// Copyright 2015-2016, The Gtk-rs Project Developers.
// See the COPYRIGHT file at the top-level directory of this distribution.
// Licensed under the MIT license, see the LICENSE file or <http://opensource.org/licenses/MIT>

use ffi;
use translate::*;
use std::mem::transmute;
use std::mem;
use ffi as glib_ffi;
use ffi::{gpointer, gboolean};

use MainContext;
use Source;
use SourceId;

use source::Priority;

impl MainContext {
    pub fn prepare(&self) -> (bool, i32) {
        unsafe {
            let mut priority = mem::uninitialized();

            let res = from_glib(ffi::g_main_context_prepare(self.to_glib_none().0, &mut priority));

            (res, priority)
        }
    }

    pub fn find_source_by_id(&self, source_id: &SourceId) -> Option<Source> {
        unsafe {
            from_glib_none(ffi::g_main_context_find_source_by_id(self.to_glib_none().0, source_id.to_glib()))
        }
    }

    /// Invokes `func` on the main context.
    pub fn invoke<F>(&self, func: F)
    where F: FnOnce() + Send + 'static {
        self.invoke_with_priority(::PRIORITY_DEFAULT_IDLE, func);
    }

    /// Invokes `func` on the main context with the given priority.
    pub fn invoke_with_priority<F>(&self, priority: Priority, func: F)
    where F: FnOnce() + Send + 'static {
        unsafe {
            self.invoke_unsafe(priority, func);
        }
    }

    /// Invokes `func` on the main context.
    ///
    /// Different to `invoke()`, this does not require `func` to be
    /// `Send` but can only be called from the thread that owns the main context.
    ///
    /// This function panics if called from a different thread than the one that
    /// owns the main context.
    pub fn invoke_local<F>(&self, func: F)
    where F: FnOnce() + 'static {
        self.invoke_local_with_priority(::PRIORITY_DEFAULT_IDLE, func);
    }

    /// Invokes `func` on the main context with the given priority.
    ///
    /// Different to `invoke_with_priority()`, this does not require `func` to be
    /// `Send` but can only be called from the thread that owns the main context.
    ///
    /// This function panics if called from a different thread than the one that
    /// owns the main context.
    pub fn invoke_local_with_priority<F>(&self, priority: Priority, func: F)
    where F: FnOnce() + 'static {
        unsafe {
            assert!(self.is_owner());
            self.invoke_unsafe(priority, func);
        }
    }

    unsafe fn invoke_unsafe<F>(&self, priority: Priority, func: F)
    where F: FnOnce() + 'static {
        let func = Box::into_raw(Box::new(Some(func)));
        glib_ffi::g_main_context_invoke_full(self.to_glib_none().0, priority.to_glib(), Some(trampoline::<F>),
            func as gpointer, Some(destroy_closure::<F>))
    }

    /// Calls closure with context configured as the thread default one.
    ///
    /// Thread default context is changed in panic-safe manner by calling
    /// [`push_thread_default`][push_thread_default] before calling closure
    /// and [`pop_thread_default`][pop_thread_default] afterwards regardless
    /// of whether closure panicked or not.
    ///
    /// [push_thread_default]: struct.MainContext.html#method.push_thread_default
    /// [pop_thread_default]: struct.MainContext.html#method.pop_thread_default
    pub fn with_thread_default<R, F: Sized>(&self, func: F) -> R
    where F: FnOnce() -> R {
        let _thread_default = ThreadDefaultContext::new(self);
        func()
    }
}

#[cfg_attr(feature = "cargo-clippy", allow(transmute_ptr_to_ref))]
unsafe extern "C" fn trampoline<F: FnOnce() + 'static>(func: gpointer) -> gboolean {
    let func: &mut Option<F> = transmute(func);
    let func = func.take().expect("MainContext::invoke() closure called multiple times");
    func();
    glib_ffi::G_SOURCE_REMOVE
}

unsafe extern "C" fn destroy_closure<F: FnOnce() + 'static>(ptr: gpointer) {
    Box::<Option<F>>::from_raw(ptr as *mut _);
}


struct ThreadDefaultContext<'a>(&'a MainContext);

impl<'a> ThreadDefaultContext<'a> {
    fn new(ctx: &MainContext) -> ThreadDefaultContext {
        ctx.push_thread_default();
        ThreadDefaultContext(ctx)
    }
}

impl<'a> Drop for ThreadDefaultContext<'a> {
    fn drop(&mut self) {
        self.0.pop_thread_default();
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::panic;
    use std::ptr;
    use std::thread;

    #[test]
    fn test_invoke() {
        let c = MainContext::new();
        let l = ::MainLoop::new(&c, false);

        let l_clone = l.clone();
        thread::spawn(move || {
            c.invoke(move || l_clone.quit());
        });

        l.run();
    }

    fn is_same_context(a: &MainContext, b: &MainContext) -> bool {
        ptr::eq(a.to_glib_none().0, b.to_glib_none().0)
    }

    #[test]
    fn test_with_thread_default() {
        let a = MainContext::new();
        let b = MainContext::new();

        assert!(!is_same_context(&a, &b));

        a.with_thread_default(|| {
            let t = MainContext::get_thread_default().unwrap();
            assert!(is_same_context(&a, &t));

            &b.with_thread_default(|| {
                let t = MainContext::get_thread_default().unwrap();
                assert!(is_same_context(&b, &t));
            });

            let t = MainContext::get_thread_default().unwrap();
            assert!(is_same_context(&a, &t));
        });
    }

    #[test]
    fn test_with_thread_default_is_panic_safe() {
        let a = MainContext::new();
        let b = MainContext::new();

        assert!(!is_same_context(&a, &b));

        a.with_thread_default(|| {
            let t = MainContext::get_thread_default().unwrap();
            assert!(is_same_context(&a, &t));

            let result = panic::catch_unwind(|| {
                &b.with_thread_default(|| {
                    panic!();
                });
            });
            assert!(result.is_err());

            let t = MainContext::get_thread_default().unwrap();
            assert!(is_same_context(&a, &t));
        });

    }
}
