1use std::{
  2    borrow::Cow,
  3    cmp::Ordering,
  4    fmt::{self, Debug},
  5    hash::{Hash, Hasher},
  6    sync::Arc,
  7};
  8
  9pub enum ArcCow<'a, T: ?Sized> {
 10    Borrowed(&'a T),
 11    Owned(Arc<T>),
 12}
 13
 14impl<T: ?Sized + PartialEq> PartialEq for ArcCow<'_, T> {
 15    fn eq(&self, other: &Self) -> bool {
 16        let a = self.as_ref();
 17        let b = other.as_ref();
 18        a == b
 19    }
 20}
 21
 22impl<T: ?Sized + PartialOrd> PartialOrd for ArcCow<'_, T> {
 23    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
 24        self.as_ref().partial_cmp(other.as_ref())
 25    }
 26}
 27
 28impl<T: ?Sized + Ord> Ord for ArcCow<'_, T> {
 29    fn cmp(&self, other: &Self) -> Ordering {
 30        self.as_ref().cmp(other.as_ref())
 31    }
 32}
 33
 34impl<T: ?Sized + Eq> Eq for ArcCow<'_, T> {}
 35
 36impl<T: ?Sized + Hash> Hash for ArcCow<'_, T> {
 37    fn hash<H: Hasher>(&self, state: &mut H) {
 38        match self {
 39            Self::Borrowed(borrowed) => Hash::hash(borrowed, state),
 40            Self::Owned(owned) => Hash::hash(&**owned, state),
 41        }
 42    }
 43}
 44
 45impl<T: ?Sized> Clone for ArcCow<'_, T> {
 46    fn clone(&self) -> Self {
 47        match self {
 48            Self::Borrowed(borrowed) => Self::Borrowed(borrowed),
 49            Self::Owned(owned) => Self::Owned(owned.clone()),
 50        }
 51    }
 52}
 53
 54impl<'a, T: ?Sized> From<&'a T> for ArcCow<'a, T> {
 55    fn from(s: &'a T) -> Self {
 56        Self::Borrowed(s)
 57    }
 58}
 59
 60impl<T: ?Sized> From<Arc<T>> for ArcCow<'_, T> {
 61    fn from(s: Arc<T>) -> Self {
 62        Self::Owned(s)
 63    }
 64}
 65
 66impl<T: ?Sized> From<&'_ Arc<T>> for ArcCow<'_, T> {
 67    fn from(s: &'_ Arc<T>) -> Self {
 68        Self::Owned(s.clone())
 69    }
 70}
 71
 72impl From<String> for ArcCow<'_, str> {
 73    fn from(value: String) -> Self {
 74        Self::Owned(value.into())
 75    }
 76}
 77
 78impl From<&String> for ArcCow<'_, str> {
 79    fn from(value: &String) -> Self {
 80        Self::Owned(value.clone().into())
 81    }
 82}
 83
 84impl<'a> From<Cow<'a, str>> for ArcCow<'a, str> {
 85    fn from(value: Cow<'a, str>) -> Self {
 86        match value {
 87            Cow::Borrowed(borrowed) => Self::Borrowed(borrowed),
 88            Cow::Owned(owned) => Self::Owned(owned.into()),
 89        }
 90    }
 91}
 92
 93impl<T> From<Vec<T>> for ArcCow<'_, [T]> {
 94    fn from(vec: Vec<T>) -> Self {
 95        ArcCow::Owned(Arc::from(vec))
 96    }
 97}
 98
 99impl<'a> From<&'a str> for ArcCow<'a, [u8]> {
100    fn from(s: &'a str) -> Self {
101        ArcCow::Borrowed(s.as_bytes())
102    }
103}
104
105impl<T: ?Sized + ToOwned> std::borrow::Borrow<T> for ArcCow<'_, T> {
106    fn borrow(&self) -> &T {
107        match self {
108            ArcCow::Borrowed(borrowed) => borrowed,
109            ArcCow::Owned(owned) => owned.as_ref(),
110        }
111    }
112}
113
114impl<T: ?Sized> std::ops::Deref for ArcCow<'_, T> {
115    type Target = T;
116
117    fn deref(&self) -> &Self::Target {
118        match self {
119            ArcCow::Borrowed(s) => s,
120            ArcCow::Owned(s) => s.as_ref(),
121        }
122    }
123}
124
125impl<T: ?Sized> AsRef<T> for ArcCow<'_, T> {
126    fn as_ref(&self) -> &T {
127        match self {
128            ArcCow::Borrowed(borrowed) => borrowed,
129            ArcCow::Owned(owned) => owned.as_ref(),
130        }
131    }
132}
133
134impl<T: ?Sized + Debug> Debug for ArcCow<'_, T> {
135    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
136        match self {
137            ArcCow::Borrowed(borrowed) => Debug::fmt(borrowed, f),
138            ArcCow::Owned(owned) => Debug::fmt(&**owned, f),
139        }
140    }
141}