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//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
//
use std::fmt::Debug;
use std::hash::Hash;
use std::iter::FromIterator;
use std::iter::IntoIterator;
use std::collections::HashMap;
#[derive(Debug, thiserror::Error)]
pub enum Error<K>
where K: Debug,
{
#[error("duplicated key in iterator: {:?}", _0)]
DuplicatedKey(K),
#[error("unknown error")]
Unknown,
}
/// An iterator adapter to collect into a HashMap or error if the iterator yields a key twice
///
/// # Note
///
/// The FromIterator implementation for this type preallocates a hashmap using the
/// Iterator::size_hint() function for the size of the hashmap.
///
/// For an adaptor that does not preallocate, have a look at `CollectOnceHashMapNoPrealloc`.
pub struct CollectOnceHashMap<K, V, S = std::collections::hash_map::RandomState>
where K: Eq + Hash + Debug
{
inner: std::result::Result<HashMap<K, V, S>, Error<K>>
}
impl<K, V, S> CollectOnceHashMap<K, V, S>
where K: Eq + Hash + Debug
{
pub fn into_inner(self) -> std::result::Result<HashMap<K, V, S>, Error<K>> {
self.inner
}
}
impl<K, V> FromIterator<(K, V)> for CollectOnceHashMap<K, V, std::collections::hash_map::RandomState>
where K: Eq + Hash + Debug
{
fn from_iter<T>(iter: T) -> Self
where T: IntoIterator<Item = (K, V)>
{
let iter = iter.into_iter();
let iter_size = {
let iter_size = iter.size_hint();
if let Some(s) = iter_size.1 {
s
} else {
iter_size.0
}
};
let mut hm = HashMap::with_capacity(iter_size);
for (element_key, element_value) in iter.into_iter() {
if hm.contains_key(&element_key) {
return CollectOnceHashMap {
inner: Err(Error::DuplicatedKey(element_key))
}
} else {
hm.insert(element_key, element_value);
}
}
CollectOnceHashMap {
inner: Ok(hm)
}
}
}
/// See `CollectOnceHashMap`
pub struct CollectOnceHashMapNoPrealloc<K, V, S = std::collections::hash_map::RandomState>
where K: Eq + Hash + Debug
{
inner: std::result::Result<HashMap<K, V, S>, Error<K>>
}
impl<K, V, S> From<CollectOnceHashMapNoPrealloc<K, V, S>> for CollectOnceHashMap<K, V, S>
where K: Eq + Hash + Debug
{
fn from(cohm: CollectOnceHashMapNoPrealloc<K, V, S>) -> Self {
CollectOnceHashMap { inner: cohm.inner }
}
}
impl<K, V> FromIterator<(K, V)> for CollectOnceHashMapNoPrealloc<K, V, std::collections::hash_map::RandomState>
where K: Eq + Hash + Debug
{
fn from_iter<T>(iter: T) -> Self
where T: IntoIterator<Item = (K, V)>
{
let mut hm = HashMap::new();
for (element_key, element_value) in iter.into_iter() {
if hm.contains_key(&element_key) {
return CollectOnceHashMapNoPrealloc {
inner: Err(Error::DuplicatedKey(element_key))
}
} else {
hm.insert(element_key, element_value);
}
}
CollectOnceHashMapNoPrealloc {
inner: Ok(hm)
}
}
}
#[cfg(test)]
mod tests {
use super::CollectOnceHashMap;
use super::Error;
#[test]
fn test_empty() {
let hm = vec![]
.into_iter()
.collect::<CollectOnceHashMap<u8, u8>>()
.into_inner()
.unwrap();
assert_eq!(0, hm.keys().count());
}
#[test]
fn test_simple() {
let hm = vec![(1, 1)]
.into_iter()
.collect::<CollectOnceHashMap<u8, u8>>()
.into_inner()
.unwrap();
assert_eq!(1, hm.keys().count());
assert!(hm.contains_key(&1));
assert!(hm.keys().all(|k| *k == 1));
assert!(hm.values().all(|k| *k == 1));
}
#[test]
fn test_duplicate() {
let hm = vec![(1, 1), (1, 2)]
.into_iter()
.collect::<CollectOnceHashMap<u8, u8>>()
.into_inner();
assert!(hm.is_err());
assert!(std::matches!(hm, Err(Error::DuplicatedKey(1))));
}
}
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