visi-core 0.2.2

//! A cheaply cloneable, copy-on-write `Vec`.

use serde::{Deserialize, Deserializer, Serialize, Serializer};
use std::ops::{Deref, DerefMut};
use std::sync::Arc;

/// A `Vec` behind an [`Arc`], cheap to clone and copy-on-write to mutate.
///
/// The engine clones whole sheets freely -- to build a compilation context, to
/// snapshot state -- and most of those clones never write. Sharing the backing
/// buffer makes that cheap; the first mutation through [`DerefMut`] calls
/// `Arc::make_mut` and takes a private copy if anyone else still holds one.
///
/// Derefs to `[T]` and `Vec<T>`, so it is used exactly like a `Vec`.
#[derive(Debug, Clone)]
pub struct SharedVec<T>(Arc<Vec<T>>);

impl<T> SharedVec<T> {
    /// An empty `SharedVec`.
    pub fn new() -> Self {
        Self(Arc::new(Vec::new()))
    }
}

impl<T> Default for SharedVec<T> {
    fn default() -> Self {
        Self(Arc::new(Vec::new()))
    }
}

impl<T> Deref for SharedVec<T> {
    type Target = Vec<T>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl<T: Clone> DerefMut for SharedVec<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        Arc::make_mut(&mut self.0)
    }
}

impl<T: Serialize> Serialize for SharedVec<T> {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        self.0.serialize(serializer)
    }
}

impl<'de, T: Deserialize<'de>> Deserialize<'de> for SharedVec<T> {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let vec = Vec::<T>::deserialize(deserializer)?;
        Ok(Self(Arc::new(vec)))
    }
}

impl<T> From<Vec<T>> for SharedVec<T> {
    fn from(v: Vec<T>) -> Self {
        Self(Arc::new(v))
    }
}

impl<T: PartialEq> PartialEq for SharedVec<T> {
    fn eq(&self, other: &Self) -> bool {
        Arc::ptr_eq(&self.0, &other.0) || self.0 == other.0
    }
}

impl<T: Eq> Eq for SharedVec<T> {}

impl<T> std::iter::FromIterator<T> for SharedVec<T> {
    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
        Self(Arc::new(iter.into_iter().collect()))
    }
}

impl<'a, T> IntoIterator for &'a SharedVec<T> {
    type Item = &'a T;
    type IntoIter = std::slice::Iter<'a, T>;

    fn into_iter(self) -> Self::IntoIter {
        self.0.iter()
    }
}

impl<'a, T: Clone> IntoIterator for &'a mut SharedVec<T> {
    type Item = &'a mut T;
    type IntoIter = std::slice::IterMut<'a, T>;

    fn into_iter(self) -> Self::IntoIter {
        Arc::make_mut(&mut self.0).iter_mut()
    }
}