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// Copyright (c) 2022, Mysten Labs, Inc.
// SPDX-License-Identifier: Apache-2.0
use serde::{de::DeserializeOwned, Serialize};
use std::{borrow::Borrow, error::Error};

pub trait Map<'a, K, V>
where
    K: Serialize + DeserializeOwned + ?Sized,
    V: Serialize + DeserializeOwned,
{
    type Error: Error;
    type Iterator: Iterator<Item = (K, V)>;
    type Keys: Iterator<Item = K>;
    type Values: Iterator<Item = V>;

    /// Returns true if the map contains a value for the specified key.
    fn contains_key(&self, key: &K) -> Result<bool, Self::Error>;

    /// Returns the value for the given key from the map, if it exists.
    fn get(&self, key: &K) -> Result<Option<V>, Self::Error>;

    /// Returns the value for the given key from the map, if it exists
    /// or the given default value if it does not.
    fn get_or_insert<F: FnOnce() -> V>(&self, key: &K, default: F) -> Result<V, Self::Error> {
        self.get(key).and_then(|optv| match optv {
            Some(v) => Ok(v),
            None => {
                self.insert(key, &default())?;
                self.get(key).transpose().expect("default just inserted")
            }
        })
    }

    /// Inserts the given key-value pair into the map.
    fn insert(&self, key: &K, value: &V) -> Result<(), Self::Error>;

    /// Removes the entry for the given key from the map.
    fn remove(&self, key: &K) -> Result<(), Self::Error>;

    /// Removes every key-value pair from the map.
    fn clear(&self) -> Result<(), Self::Error>;

    /// Returns true if the map is empty, otherwise false.
    fn is_empty(&self) -> bool;

    /// Returns an iterator visiting each key-value pair in the map.
    fn iter(&'a self) -> Self::Iterator;

    /// Returns an iterator over each key in the map.
    fn keys(&'a self) -> Self::Keys;

    /// Returns an iterator over each value in the map.
    fn values(&'a self) -> Self::Values;

    /// Returns a vector of values corresponding to the keys provided.
    fn multi_get<J>(
        &self,
        keys: impl IntoIterator<Item = J>,
    ) -> Result<Vec<Option<V>>, Self::Error>
    where
        J: Borrow<K>;

    /// Inserts key-value pairs.
    fn multi_insert<J, U>(
        &self,
        key_val_pairs: impl IntoIterator<Item = (J, U)>,
    ) -> Result<(), Self::Error>
    where
        J: Borrow<K>,
        U: Borrow<V>;

    /// Removes keys.
    fn multi_remove<J>(&self, keys: impl IntoIterator<Item = J>) -> Result<(), Self::Error>
    where
        J: Borrow<K>;
}