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//! Functions for (de)serializing to and from BTreeMaps.
//!
//! See the crate-level documentation for more information.

use std::{
    collections::HashMap,
    hash::Hash,
};
use serde::{
    de::{Deserialize, Deserializer},
    ser::{Serialize, Serializer},
};
use super::Key;

/// Serialize a HashMap.
///
/// See the crate-level documentation for more information.
pub fn serialize<'a, S: Serializer, T: Serialize, U: Eq + Hash>(
    map: &HashMap<U, T>,
    serializer: S,
) -> Result<S::Ok, S::Error> {
    serializer.collect_seq(map.values())
}

/// Deserialize a HashMap.
///
/// See the crate-level documentation for more information.
pub fn deserialize<'a, D, T, U>(
    deserializer: D,
) -> Result<HashMap<U, T>, D::Error>
    where D: Deserializer<'a>,
          T: Key<'a, U> + Deserialize<'a>,
          U: Deserialize<'a> + Eq + Hash + Serialize {
    let items = Vec::<T>::deserialize(deserializer)?;
    let mut map = HashMap::with_capacity(items.len());

    for item in items {
        map.insert(item.key(), item);
    }

    Ok(map)
}

#[cfg(test)]
mod tests {
    use serde_derive::{Deserialize, Serialize};
    use serde_test::Token;
    use std::collections::HashMap;
    use super::Key;

    #[derive(Debug, Deserialize, Eq, PartialEq, Serialize)]
    struct Item {
        id: u8,
        name: String,
    }

    impl Key<'_, u8> for Item {
        fn key(&self) -> u8 {
            self.id
        }
    }

    #[derive(Debug, Deserialize, Eq, PartialEq, Serialize)]
    struct Items {
        #[serde(with = "crate")]
        items: HashMap<u8, Item>,
    }

    #[test]
    fn test_de() {
        let mut item_map = HashMap::new();
        item_map.insert(1, Item {
            id: 1,
            name: "foo".to_owned(),
        });

        let items = Items {
            items: item_map,
        };

        serde_test::assert_tokens(&items, &[
            Token::Struct { name: "Items", len: 1 },
            Token::Str("items"),
            Token::Seq { len: Some(1) },
            Token::Struct { name: "Item", len: 2 },
            Token::Str("id"),
            Token::U8(1),
            Token::Str("name"),
            Token::Str("foo"),
            Token::StructEnd,
            Token::SeqEnd,
            Token::StructEnd,
        ]);
    }
}