use std::rc::{self, Rc};
use std::sync::{self, Arc};

/// Trait for generalizing downgrading a strong reference to a weak reference.
pub trait Downgrade
where
    Self: Sized,
{
    /// Weak reference type.
    type Weak;

    /// Downgrade to a weak reference.
    fn downgrade(&self) -> Self::Weak;
}

/// Trait for generalizing upgrading a weak reference to a strong reference.
pub trait Upgrade
where
    Self: Sized,
{
    /// Strong reference type.
    type Strong;

    /// Try upgrading a weak reference to a strong reference.
    fn upgrade(&self) -> Option<Self::Strong>;
}

impl<T: Downgrade + crate::ObjectType> Upgrade for crate::WeakRef<T> {
    type Strong = T;

    fn upgrade(&self) -> Option<Self::Strong> {
        self.upgrade()
    }
}

impl<T: Downgrade> Downgrade for &T {
    type Weak = T::Weak;

    fn downgrade(&self) -> Self::Weak {
        T::downgrade(*self)
    }
}

impl<T> Downgrade for Arc<T> {
    type Weak = sync::Weak<T>;

    fn downgrade(&self) -> Self::Weak {
        Arc::downgrade(self)
    }
}

impl<T> Upgrade for sync::Weak<T> {
    type Strong = Arc<T>;

    fn upgrade(&self) -> Option<Self::Strong> {
        self.upgrade()
    }
}

impl<T> Downgrade for Rc<T> {
    type Weak = rc::Weak<T>;

    fn downgrade(&self) -> Self::Weak {
        Rc::downgrade(self)
    }
}

impl<T> Upgrade for rc::Weak<T> {
    type Strong = Rc<T>;

    fn upgrade(&self) -> Option<Self::Strong> {
        self.upgrade()
    }
}

#[doc(hidden)]
#[macro_export]
macro_rules! to_type_before {
    (_) => ();
    ($($variable:ident).+ $(as $rename:ident)?) => (
        compile_error!("You need to specify if this is a weak or a strong clone.");
    );
    (@strong $variable:ident) => (
        let $variable = $variable.clone();
    );
    (@weak $variable:ident) => (
        let $variable = $crate::clone::Downgrade::downgrade(&$variable);
    );
    (@strong $($variable:ident).+ as $rename:ident) => (
        let $rename = $($variable).+.clone();
    );
    (@weak $($variable:ident).+ as $rename:ident) => (
        let $rename = $crate::clone::Downgrade::downgrade(&$($variable).+);
    );
    (@ $keyword:ident $($variable:ident).+ $(as $rename:ident)?) => (
        compile_error!("Unknown keyword, only `weak` and `strong` are allowed");
    );
}

#[doc(hidden)]
#[macro_export]
macro_rules! to_type_after {
    (@default-panic, @weak $variable:ident) => {
        let $variable = match $crate::clone::Upgrade::upgrade(&$variable) {
            Some(val) => val,
            None => panic!("failed to upgrade {}", stringify!($variable)),
        };
    };
    (as $rename:ident @default-panic, @weak $($variable:ident).+) => {
        let $rename = match $crate::clone::Upgrade::upgrade(&$rename) {
            Some(val) => val,
            None => panic!("failed to upgrade {}", stringify!($rename)),
        };
    };
    ($(as $rename:ident)? @default-panic, @strong $($variable:ident).+) => {};
    (@weak $variable:ident , $return_value:expr) => {
        let $variable = match $crate::clone::Upgrade::upgrade(&$variable) {
            Some(val) => val,
            None => return ($return_value)(),
        };
    };
    (as $rename:ident @weak $($variable:ident).+ , $return_value:expr) => {
        let $rename = match $crate::clone::Upgrade::upgrade(&$rename) {
            Some(val) => val,
            None => return ($return_value)(),
        };
    };
    ($(as $rename:ident)? @strong $($variable:ident).+ , $return_value:expr) => {};
    ($(as $rename:ident)? @ $keyword:ident $($variable:ident).+, $return_value:expr) => {};
}

#[doc(hidden)]
#[macro_export]
macro_rules! to_return_value {
    () => {
        ()
    };
    ($value:expr) => {
        $value
    };
}

/// Macro for passing variables as strong or weak references into a closure.
///
/// This macro can be useful in combination with closures, e.g. signal handlers, to reduce the
/// boilerplate required for passing strong or weak references into the closure. It will
/// automatically create the new reference and pass it with the same name into the closure.
///
/// If upgrading the weak reference to a strong reference inside the closure is failing, the
/// closure is immediately returning an optional default return value. If none is provided, `()` is
/// returned.
///
/// ### Passing a strong reference
///
/// ```
/// use glib::clone;
/// use std::rc::Rc;
///
/// let v = Rc::new(1);
/// let closure = clone!(@strong v => move |x| {
///     println!("v: {}, x: {}", v, x);
/// });
///
/// closure(2);
/// ```
///
/// ### Passing a strong and weak reference
///
/// ```
/// use glib::clone;
/// use std::rc::Rc;
///
/// let v = Rc::new(1);
/// let u = Rc::new(2);
/// let closure = clone!(@strong v, @weak u => move |x| {
///     println!("v: {}, u: {}, x: {}", v, u, x);
/// });
///
/// closure(3);
/// ```
///
/// ### Renaming variables
///
/// ```
/// use glib::clone;
/// use std::rc::Rc;
///
/// let v = Rc::new(1);
/// let u = Rc::new(2);
/// let closure = clone!(@strong v as y, @weak u => move |x| {
///     println!("v as y: {}, u: {}, x: {}", y, u, x);
/// });
///
/// closure(3);
/// ```
///
/// ### Providing a default return value if upgrading a weak reference fails
///
/// You can do it in two different ways:
///
/// Either by providing the value yourself using `@default-return`:
///
/// ```
/// use glib::clone;
/// use std::rc::Rc;
///
/// let v = Rc::new(1);
/// let closure = clone!(@weak v => @default-return false, move |x| {
///     println!("v: {}, x: {}", v, x);
///     true
/// });
///
/// // Drop value so that the weak reference can't be upgraded.
/// drop(v);
///
/// assert_eq!(closure(2), false);
/// ```
///
/// Or by using `@default-panic` (if the value fails to get upgraded, it'll panic):
///
/// ```run_fail
/// # use glib::clone;
/// # use std::rc::Rc;
/// # let v = Rc::new(1);
/// let closure = clone!(@weak v => @default-panic, move |x| {
///     println!("v: {}, x: {}", v, x);
///     true
/// });
/// # drop(v);
/// # assert_eq!(closure(2), false);
/// ```
///
/// ### Errors
///
/// Here is a list of errors you might encounter:
///
/// **Missing `@weak` or `@strong`**:
///
/// ```compile_fail
/// # use glib::clone;
/// # use std::rc::Rc;
/// let v = Rc::new(1);
///
/// let closure = clone!(v => move |x| {
///     println!("v: {}, x: {}", v, x);
/// });
/// # drop(v);
/// # closure(2);
/// ```
///
/// **Passing `self` as an argument**:
///
/// ```compile_fail
/// # use glib::clone;
/// # use std::rc::Rc;
/// #[derive(Debug)]
/// struct Foo;
///
/// impl Foo {
///     fn foo(&self) {
///         let v = Rc::new(1);
///
///         let closure = clone!(@strong self => move |x| {
///             println!("v: {:?}", self);
///         });
///         # drop(v);
///         # closure(2);
///     }
/// }
/// ```
///
/// If you want to use `self` directly, you'll need to rename it:
///
/// ```
/// # use glib::clone;
/// # use std::rc::Rc;
/// #[derive(Debug)]
/// struct Foo;
///
/// impl Foo {
///     fn foo(&self) {
///         let v = Rc::new(1);
///
///         let closure = clone!(@strong self as this => move |x| {
///             println!("v: {:?}", this);
///         });
///         # drop(v);
///         # closure(2);
///     }
/// }
/// ```
///
/// **Passing fields directly**
///
/// ```compile_fail
/// # use glib::clone;
/// # use std::rc::Rc;
/// #[derive(Debug)]
/// struct Foo {
///     v: Rc<usize>,
/// }
///
/// impl Foo {
///     fn foo(&self) {
///         let closure = clone!(@strong self.v => move |x| {
///             println!("v: {:?}", v);
///         });
///         # closure(2);
///     }
/// }
/// ```
///
/// You can do it by renaming it:
///
/// ```
/// # use glib::clone;
/// # use std::rc::Rc;
/// # struct Foo {
/// #     v: Rc<usize>,
/// # }
///
/// impl Foo {
///     fn foo(&self) {
///         let closure = clone!(@strong self.v as v => move |x| {
///             println!("v: {}", v);
///         });
///         # closure(2);
///     }
/// }
#[macro_export]
macro_rules! clone {
    ($($(@ $strength:ident)? self),+ => $($_:tt)* ) => (
        compile_error!("Can't use `self` as variable name. Try storing it in a temporary variable or rename it.");
    );
    ($($(@ $strength:ident)? $up:ident.$($variables:ident).+),+ => $($_:tt)* ) => (
        compile_error!("Field accesses are not allowed as is, you must rename it!");
    );
    ($($(@ $strength:ident)? $($variables:ident).+ $(as $rename:ident)?),+ => @default-panic, move || $body:block ) => (
        {
            $( $crate::to_type_before!($(@ $strength)? $($variables).+ $(as $rename)?); )*
            move || {
                $( $crate::to_type_after!($(as $rename)? @default-panic, $(@ $strength)? $($variables).+);)*
                $body
            }
        }
    );
    ($($(@ $strength:ident)? $($variables:ident).+ $(as $rename:ident)?),+ => $(@default-return $return_value:expr,)? move || $body:block ) => (
        {
            $( $crate::to_type_before!($(@ $strength)? $($variables).+ $(as $rename)?); )*
            move || {
                let return_value = || $crate::to_return_value!($($return_value)?);
                $( $crate::to_type_after!($(as $rename)? $(@ $strength)? $($variables).+, return_value );)*
                $body
            }
        }
    );
    ($($(@ $strength:ident)? $($variables:ident).+ $(as $rename:ident)?),+ => @default-panic, move | $($pattern:pat),* | $body:block ) => (
        {
            $( $crate::to_type_before!($(@ $strength)? $($variables).+ $(as $rename)?); )*
            move |$($pattern),*| {
                $( $crate::to_type_after!($(as $rename)? @default-panic, $(@ $strength)? $($variables).+);)*
                $body
            }
        }
    );
    ($($(@ $strength:ident)? $($variables:ident).+ $(as $rename:ident)?),+ => $(@default-return $return_value:expr,)? move | $($pattern:pat),* | $body:block ) => (
        {
            $( $crate::to_type_before!($(@ $strength)? $($variables).+ $(as $rename)?); )*
            move |$($pattern),*| {
                let return_value = || $crate::to_return_value!($($return_value)?);
                $( $crate::to_type_after!($(as $rename)? $(@ $strength)? $($variables).+, return_value);)*
                $body
            }
        }
    );
    ($($(@ $strength:ident)? $variables:expr),+ => $($_:tt)* ) => (
        compile_error!("Variables need to be valid identifiers, e.g. field accesses are not allowed");
    );
}