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use std::{borrow::Borrow, fmt, mem, ops};

pub struct Cached<T> {
	val: T,
	changed: bool,
}
impl<T> Cached<T> {
	pub fn get(&self) -> &T {
		&self.val
	}
	pub fn new(v: impl Into<T>) -> Self {
		Self { val: v.into(), changed: true }
	}
	pub fn replace(self, v: impl Into<T>) -> Self {
		Self { val: v.into(), changed: true }
	}
	pub fn changed(&mut self) -> bool {
		mem::replace(&mut self.changed, false)
	}
}
impl<T> AsRef<T> for Cached<T> {
	fn as_ref(&self) -> &T {
		&self.val
	}
}
impl<T> Borrow<T> for Cached<T> {
	fn borrow(&self) -> &T {
		&self.val
	}
}
impl<T> ops::Deref for Cached<T> {
	type Target = T;

	fn deref(&self) -> &T {
		&self.val
	}
}
impl<T: Default> Default for Cached<T> {
	fn default() -> Self {
		Self { val: T::default(), changed: true }
	}
}
impl<T: Clone> Clone for Cached<T> {
	fn clone(&self) -> Self {
		Self { val: self.val.clone(), changed: true }
	}
}
impl<T: fmt::Debug> fmt::Debug for Cached<T> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		write!(f, "{:?}", self.val)
	}
}
impl<T: fmt::Display> fmt::Display for Cached<T> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		write!(f, "{}", self.val)
	}
}
impl<T: Eq> Eq for Cached<T> {}
impl<T: PartialEq> PartialEq for Cached<T> {
	fn eq(&self, r: &Self) -> bool {
		self.val == r.val
	}
}

#[cfg(feature = "adv_fs")]
mod serde {
	use {super::*, crate::ser::*};

	impl<T: Serialize> Serialize for Cached<T> {
		fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
			self.val.serialize(s)
		}
	}
	impl<'de, T: Deserialize<'de>> Deserialize<'de> for Cached<T> {
		fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
			let val = T::deserialize(d)?;
			Ok(Self { val, changed: true })
		}
	}
}