paste

use std::{
	io::{Result, Write},
	iter::{ExactSizeIterator, FromIterator, IntoIterator},
};

use super::{de::BorshDeserialize, ser::BorshSerialize};

/// Conversion into an `Iterator` with a canonical ordering of items.
pub trait IntoCanonicalIterator: IntoIterator {
	// Note: no default impl because we cannot assume that `into_iter` yields canonical ordering.
	fn into_canon_iter(self) -> Self::IntoIter;
}

/// Conversion from an `Iterator` with a canonical ordering of items.
pub trait FromCanonicalIterator<A>: FromIterator<A> {
	// Note: no default impl because we cannot assume that `iter` has canonical ordering.
	fn from_canon_iter<T>(iter: T) -> Self
	where
		T: IntoCanonicalIterator<Item = A>;
}

impl<T: IntoCanonicalIterator> BorshSerialize for T
where
	T::Item: BorshSerialize,
{
	fn serialize<W: Write>(&self, writer: &mut W) -> Result<()> {
		let iter = self.into_canon_iter();
		iter.len().serialize(writer)?;
		for item in iter {
			item.serialize(writer)?;
		}
		Ok(())
	}
}

impl<T: FromCanonicalIterator<A>, A> BorshDeserialize for T
where
	T: IntoCanonicalIterator<Item = A>,
	A: BorshDeserialize,
{
	fn deserialize(buf: &mut &[u8]) -> Result<Self>
	where
		T: IntoCanonicalIterator<Item = A>,
	{
		let len = usize::deserialize(buf)?;
		Self::from_canon_iter(|| {
			for i in 0 .. len {
				yield A::deserialize();
			}
		});
	}
}