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use super::VecMap;
use core::fmt;
use core::marker::PhantomData;
use serde::de::{self, value::MapDeserializer};
use serde::ser;

impl<K, V> ser::Serialize for VecMap<K, V>
where
    K: ser::Serialize + Eq,
    V: ser::Serialize,
{
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: ser::Serializer,
    {
        serializer.collect_map(self)
    }
}

impl<'de, K, V> de::Deserialize<'de> for VecMap<K, V>
where
    K: de::Deserialize<'de> + Eq,
    V: de::Deserialize<'de>,
{
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: de::Deserializer<'de>,
    {
        struct VecMapVisitor<K, V>(PhantomData<(K, V)>);

        impl<'de, K, V> de::Visitor<'de> for VecMapVisitor<K, V>
        where
            K: de::Deserialize<'de> + Eq,
            V: de::Deserialize<'de>,
        {
            type Value = VecMap<K, V>;

            fn expecting(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
                fmt.write_str("a map")
            }

            fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
            where
                A: de::MapAccess<'de>,
            {
                let mut values = VecMap::with_capacity(map.size_hint().unwrap_or(0));

                while let Some((key, value)) = map.next_entry()? {
                    values.insert(key, value);
                }

                Ok(values)
            }
        }

        deserializer.deserialize_map(VecMapVisitor(PhantomData))
    }
}

impl<'de, K, V, E> de::IntoDeserializer<'de, E> for VecMap<K, V>
where
    K: de::IntoDeserializer<'de, E> + Eq,
    V: de::IntoDeserializer<'de, E>,
    E: de::Error,
{
    type Deserializer = MapDeserializer<'de, <Self as IntoIterator>::IntoIter, E>;

    fn into_deserializer(self) -> Self::Deserializer {
        MapDeserializer::new(self.into_iter())
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use serde_test::{assert_tokens, Token};

    #[test]
    fn ser_de_empty() {
        let map = VecMap::<u8, &str>::new();
        assert_tokens(&map, &[Token::Map { len: Some(0) }, Token::MapEnd]);
    }

    #[test]
    fn ser_de() {
        let map = VecMap::from([("a", 1), ("b", 2), ("c", 3)]);
        assert_tokens(
            &map,
            &[
                Token::Map { len: Some(3) },
                Token::BorrowedStr("a"),
                Token::I32(1),
                Token::BorrowedStr("b"),
                Token::I32(2),
                Token::BorrowedStr("c"),
                Token::I32(3),
                Token::MapEnd,
            ],
        );
    }
}