1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130

use crate::{
    observer::{ObserverInternalFns, ObserverList},
    static_state,
};
use std::{
    cell::{Ref, RefCell, RefMut},
    ops::{Deref, DerefMut},
    rc::{Rc, Weak},
};

pub(crate) trait ObservableInternalFns {
    fn add_observer(&self, observer: Weak<dyn ObserverInternalFns>);
    fn remove_observer(&self, observer: &Weak<dyn ObserverInternalFns>);
    fn get_unique_data_address(&self) -> *const ();
}

#[repr(C)]
struct ObservableData<T: ?Sized> {
    observers: ObserverList,
    value: RefCell<T>,
}

impl<T: ?Sized> ObservableData<T> {
    fn after_modified(&self) {
        self.observers.broadcast_stale();
        self.observers.broadcast_ready(true);
    }
}

impl<T> ObservableInternalFns for ObservableData<T> {
    fn add_observer(&self, observer: Weak<dyn ObserverInternalFns>) {
        self.observers.add(observer);
    }

    fn remove_observer(&self, observer: &Weak<dyn ObserverInternalFns>) {
        self.observers.remove(observer);
    }

    fn get_unique_data_address(&self) -> *const () {
        self.value.as_ptr() as _
    }
}

pub struct ObservablePtr<T: ?Sized + 'static> {
    ptr: Rc<ObservableData<T>>,
}

impl<T: ?Sized + 'static> Clone for ObservablePtr<T> {
    fn clone(&self) -> Self {
        Self {
            ptr: Rc::clone(&self.ptr),
        }
    }
}

pub struct ObservableRef<'a, T: ?Sized + 'a> {
    raw: Ref<'a, T>,
}

impl<'a, T: ?Sized + 'a> From<Ref<'a, T>> for ObservableRef<'a, T> {
    fn from(raw: Ref<'a, T>) -> Self {
        Self { raw }
    }
}

impl<'a, T: ?Sized + 'a> Deref for ObservableRef<'a, T> {
    type Target = T;
    fn deref(&self) -> &T {
        &*self.raw
    }
}

pub struct ObservableRefMut<'a, T: ?Sized + 'a> {
    data: Rc<ObservableData<T>>,
    raw: Option<RefMut<'a, T>>,
}

impl<'a, T: ?Sized + 'a> Deref for ObservableRefMut<'a, T> {
    type Target = T;
    fn deref(&self) -> &T {
        self.raw.as_deref().unwrap()
    }
}

impl<'a, T: ?Sized + 'a> DerefMut for ObservableRefMut<'a, T> {
    fn deref_mut(&mut self) -> &mut T {
        self.raw.as_deref_mut().unwrap()
    }
}
impl<'a, T: ?Sized + 'a> Drop for ObservableRefMut<'a, T> {
    fn drop(&mut self) {
        // Drop the reference so that observers notified of the changes can read the new data.
        self.raw = None;
        self.data.after_modified();
    }
}

impl<T: 'static> ObservablePtr<T> {
    pub fn new(value: T) -> Self {
        let bx = ObservableData {
            observers: Default::default(),
            value: RefCell::new(value),
        };
        let ptr = Rc::new(bx);
        Self { ptr }
    }

    pub fn borrow(&self) -> ObservableRef<T> {
        static_state::note_observed(Rc::clone(&self.ptr) as _);
        From::from(self.ptr.value.borrow())
    }

    pub fn borrow_untracked(&self) -> ObservableRef<T> {
        From::from(self.ptr.value.borrow())
    }

    pub fn borrow_mut(&self) -> ObservableRefMut<T> {
        ObservableRefMut {
            data: Rc::clone(&self.ptr),
            raw: Some(self.ptr.value.borrow_mut()),
        }
    }

    pub fn set(&self, new_value: T) {
        let mut value_storage = self.ptr.value.borrow_mut();
        *value_storage = new_value;
        drop(value_storage);
        self.ptr.after_modified();
    }
}