// 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>

//! `IMPL` Boxed wrapper implementation.

use std::ops::{Deref, DerefMut};
use std::fmt;
use std::marker::PhantomData;
use std::mem;
use translate::*;

/// Wrapper implementations for Boxed types. See `glib_wrapper!`.
#[macro_export]
macro_rules! glib_boxed_wrapper {
    ([$($attr:meta)*] $name:ident, $ffi_name:path, @copy $copy_arg:ident $copy_expr:expr,
     @free $free_arg:ident $free_expr:expr) => {
        $(#[$attr])*
        #[derive(Clone, Debug)]
        pub struct $name($crate::boxed::Boxed<$ffi_name, MemoryManager>);

        #[doc(hidden)]
        pub struct MemoryManager;

        impl $crate::boxed::BoxedMemoryManager<$ffi_name> for MemoryManager {
            #[inline]
            unsafe fn copy($copy_arg: *const $ffi_name) -> *mut $ffi_name {
                $copy_expr
            }

            #[inline]
            unsafe fn free($free_arg: *mut $ffi_name) {
                $free_expr
            }
        }

        #[doc(hidden)]
        impl $crate::translate::Uninitialized for $name {
            #[inline]
            unsafe fn uninitialized() -> Self {
                $name($crate::boxed::Boxed::uninitialized())
            }
        }

        #[doc(hidden)]
        impl $crate::translate::GlibPtrDefault for $name {
            type GlibType = *mut $ffi_name;
        }

        #[doc(hidden)]
        impl<'a> $crate::translate::ToGlibPtr<'a, *const $ffi_name> for $name {
            type Storage = &'a $crate::boxed::Boxed<$ffi_name, MemoryManager>;

            #[inline]
            fn to_glib_none(&'a self) -> $crate::translate::Stash<'a, *const $ffi_name, Self> {
                let stash = self.0.to_glib_none();
                $crate::translate::Stash(stash.0, stash.1)
            }
        }

        #[doc(hidden)]
        impl<'a> $crate::translate::ToGlibPtrMut<'a, *mut $ffi_name> for $name {
            type Storage = &'a mut $crate::boxed::Boxed<$ffi_name, MemoryManager>;

            #[inline]
            fn to_glib_none_mut(&'a mut self) -> $crate::translate::StashMut<'a, *mut $ffi_name, Self> {
                let stash = self.0.to_glib_none_mut();
                $crate::translate::StashMut(stash.0, stash.1)
            }
        }

        #[doc(hidden)]
        impl $crate::translate::FromGlibPtrNone<*mut $ffi_name> for $name {
            #[inline]
            unsafe fn from_glib_none(ptr: *mut $ffi_name) -> Self {
                $name($crate::translate::from_glib_none(ptr))
            }
        }

        #[doc(hidden)]
        impl $crate::translate::FromGlibPtrFull<*mut $ffi_name> for $name {
            #[inline]
            unsafe fn from_glib_full(ptr: *mut $ffi_name) -> Self {
                $name($crate::translate::from_glib_full(ptr))
            }
        }

        #[doc(hidden)]
        impl $crate::translate::FromGlibPtrBorrow<*mut $ffi_name> for $name {
            #[inline]
            unsafe fn from_glib_borrow(ptr: *mut $ffi_name) -> Self {
                $name($crate::translate::from_glib_borrow(ptr))
            }
        }
    }
}

enum AnyBox<T> {
    Native(Box<T>),
    ForeignOwned(*mut T),
    ForeignBorrowed(*mut T),
}

impl<T> fmt::Debug for AnyBox<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use self::AnyBox::*;
        match *self {
            Native(ref b) => write!(f, "Native({:?})", &**b as *const T),
            ForeignOwned(ptr) => write!(f, "ForeignOwned({:?})", ptr),
            ForeignBorrowed(ptr) => write!(f, "ForeignBorrowed({:?})", ptr),
        }
    }
}

/// Memory management functions for a boxed type.
pub trait BoxedMemoryManager<T>: 'static {
    /// Makes a copy.
    unsafe fn copy(ptr: *const T) -> *mut T;
    /// Frees the object.
    unsafe fn free(ptr: *mut T);
}

/// Encapsulates memory management logic for boxed types.
pub struct Boxed<T: 'static, MM: BoxedMemoryManager<T>> {
    inner: AnyBox<T>,
    _dummy: PhantomData<MM>,
}

impl<T: 'static, MM: BoxedMemoryManager<T>> Boxed<T, MM> {
    #[inline]
    pub unsafe fn uninitialized() -> Self {
        Boxed {
            inner: AnyBox::Native(Box::new(mem::uninitialized())),
            _dummy: PhantomData,
        }
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> Uninitialized for Boxed<T, MM> {
    #[inline]
    unsafe fn uninitialized() -> Self {
        Boxed {
            inner: AnyBox::Native(Box::new(mem::uninitialized())),
            _dummy: PhantomData,
        }
    }
}

impl<'a, T: 'static, MM: BoxedMemoryManager<T>> ToGlibPtr<'a, *const T> for Boxed<T, MM> {
    type Storage = &'a Self;

    #[inline]
    fn to_glib_none(&'a self) -> Stash<'a, *const T, Self> {
        use self::AnyBox::*;
        let ptr = match self.inner {
            Native(ref b) => &**b as *const T,
            ForeignOwned(p) | ForeignBorrowed(p) => p as *const T,
        };
        Stash(ptr, self)
    }
}

impl<'a, T: 'static, MM: BoxedMemoryManager<T>> ToGlibPtrMut<'a, *mut T> for Boxed<T, MM> {
    type Storage = &'a mut Self;

    #[inline]
    fn to_glib_none_mut(&'a mut self) -> StashMut<'a, *mut T, Self> {
        use self::AnyBox::*;
        let ptr = match self.inner {
            Native(ref mut b) => &mut **b as *mut T,
            ForeignOwned(p) | ForeignBorrowed(p) => p,
        };
        StashMut(ptr, self)
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> FromGlibPtrNone<*mut T> for Boxed<T, MM> {
    #[inline]
    unsafe fn from_glib_none(ptr: *mut T) -> Self {
        assert!(!ptr.is_null());
        let ptr = MM::copy(ptr);
        from_glib_full(ptr)
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> FromGlibPtrFull<*mut T> for Boxed<T, MM> {
    #[inline]
    unsafe fn from_glib_full(ptr: *mut T) -> Self {
        assert!(!ptr.is_null());
        Boxed {
            inner: AnyBox::ForeignOwned(ptr),
            _dummy: PhantomData,
        }
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> FromGlibPtrBorrow<*mut T> for Boxed<T, MM> {
    #[inline]
    unsafe fn from_glib_borrow(ptr: *mut T) -> Self {
        assert!(!ptr.is_null());
        Boxed {
            inner: AnyBox::ForeignBorrowed(ptr),
            _dummy: PhantomData,
        }
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> Drop for Boxed<T, MM> {
    #[inline]
    fn drop(&mut self) {
        unsafe {
            if let AnyBox::ForeignOwned(ptr) = self.inner {
                MM::free(ptr);
            }
        }
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> fmt::Debug for Boxed<T, MM> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Boxed {{ inner: {:?} }}", self.inner)
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> Clone for Boxed<T, MM> {
    #[inline]
    fn clone(&self) -> Self {
        unsafe {
            from_glib_none(self.to_glib_none().0 as *mut T)
        }
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> Deref for Boxed<T, MM> {
    type Target = T;

    fn deref(&self) -> &T {
        unsafe {
            // This is safe because the pointer will remain valid while self is borrowed
            mem::transmute(self.to_glib_none().0)
        }
    }
}

impl<T: 'static, MM: BoxedMemoryManager<T>> DerefMut for Boxed<T, MM> {
    fn deref_mut(&mut self) -> &mut T {
        unsafe {
            // This is safe because the pointer will remain valid while self is borrowed
            mem::transmute(self.to_glib_none_mut().0)
        }
    }
}