use owning_ref::{RcRef, OwningHandle};
use std::any::Any;

use std::cell::{RefCell, RefMut};
use std::rc::Rc;
use view::{Selector, View, ViewWrapper};

/// Wrapper around a view to provide interior mutability.
pub struct IdView<V: View> {
    view: Rc<RefCell<V>>,
    id: String,
}

/// Mutable reference to a view.
///
/// This behaves like a [`RefMut`], but without being tied to a lifetime.
///
/// [`RefMut`]: https://doc.rust-lang.org/std/cell/struct.RefMut.html
pub type ViewRef<V> = OwningHandle<RcRef<RefCell<V>>, RefMut<'static, V>>;

impl<V: View> IdView<V> {
    /// Wraps `view` in a new `IdView`.
    pub fn new<S: Into<String>>(id: S, view: V) -> Self {
        IdView {
            view: Rc::new(RefCell::new(view)),
            id: id.into(),
        }
    }

    /// Gets mutable access to the inner view.
    ///
    /// This returns a `ViewRef<V>`, which implement `DerefMut<Target = V>`.
    pub fn get_mut(&mut self) -> ViewRef<V> {
        // TODO: return a standalone item (not tied to our lifetime)
        // that bundles `self.view.clone()` and allow mutable reference to
        // the inner view.
        let cell_ref = RcRef::new(self.view.clone());

        OwningHandle::new(cell_ref,
                          |x| unsafe { x.as_ref() }.unwrap().borrow_mut())
    }
}

impl<T: View + 'static> ViewWrapper for IdView<T> {
    type V = T;

    fn with_view<F, R>(&self, f: F) -> Option<R>
        where F: FnOnce(&Self::V) -> R
    {
        self.view
            .try_borrow()
            .ok()
            .map(|v| f(&*v))
    }

    fn with_view_mut<F, R>(&mut self, f: F) -> Option<R>
        where F: FnOnce(&mut Self::V) -> R
    {
        self.view
            .try_borrow_mut()
            .ok()
            .map(|mut v| f(&mut *v))
    }

    fn wrap_call_on_any<'a>(&mut self, selector: &Selector,
                         mut callback: Box<for<'b> FnMut(&'b mut Any) + 'a>) {
        match selector {
            &Selector::Id(id) if id == self.id => callback(self),
            s => self.view.borrow_mut().call_on_any(s, callback),
        }
    }

    fn wrap_focus_view(&mut self, selector: &Selector) -> Result<(), ()> {
        match selector {
            &Selector::Id(id) if id == self.id => Ok(()),
            s => self.view.borrow_mut().focus_view(s),
        }
    }
}