collected/
from_unique_ord.rs

1use crate::common::*;
2
3/// A wrapper around a collection `U` that can only be collected or extended from an unique-valued iterator.
4///
5/// The wrapper maintains a [BTreeSet](BTreeSet) internally. If an incoming value `A` is duplicated,
6/// it clears the internal collections and ignores future values.
7pub struct FromUniqueOrd<U, A>(Option<State<U, A>>)
8where
9    A: Ord + Clone;
10
11struct State<U, A>
12where
13    A: Ord + Clone,
14{
15    inner: U,
16    set: BTreeSet<A>,
17}
18
19impl<U, A> FromUniqueOrd<U, A>
20where
21    A: Ord + Clone,
22{
23    pub fn get(&self) -> Option<&U> {
24        self.0.as_ref().map(|state| &state.inner)
25    }
26
27    pub fn into_inner(self) -> Option<U> {
28        self.0.map(|state| state.inner)
29    }
30}
31
32impl<U, A> FromIterator<A> for FromUniqueOrd<U, A>
33where
34    U: FromIterator<A>,
35    A: Ord + Clone,
36{
37    fn from_iter<T: IntoIterator<Item = A>>(iter: T) -> Self {
38        let mut set = Some(BTreeSet::new());
39        let inner: U = iter
40            .into_iter()
41            .map(|item| {
42                let ok = set.as_mut().unwrap().insert(item.clone());
43
44                if ok {
45                    Some(item)
46                } else {
47                    set = None;
48                    None
49                }
50            })
51            .fuse()
52            .flatten()
53            .collect();
54
55        let state = set.map(|set| State { inner, set });
56
57        Self(state)
58    }
59}
60
61impl<U, A> Extend<A> for FromUniqueOrd<U, A>
62where
63    U: Extend<A>,
64    A: Ord + Clone,
65{
66    fn extend<T: IntoIterator<Item = A>>(&mut self, iter: T) {
67        if let Some(state) = &mut self.0 {
68            let State { inner, set } = state;
69            let mut ok = true;
70
71            let iter = iter
72                .into_iter()
73                .map(|item| {
74                    ok &= set.insert(item.clone());
75                    ok.then(|| item)
76                })
77                .fuse()
78                .flatten();
79            inner.extend(iter);
80
81            if !ok {
82                self.0 = None;
83            }
84        }
85    }
86}
87
88#[cfg(test)]
89mod tests {
90    use super::*;
91
92    #[test]
93    fn unique_ord_test() {
94        let unique: FromUniqueOrd<Vec<_>, _> = vec![1, 2, 3].into_iter().collect();
95        assert_eq!(unique.into_inner(), Some(vec![1, 2, 3]));
96
97        let unique: FromUniqueOrd<Vec<_>, _> = vec![1, 2, 3, 3].into_iter().collect();
98        assert_eq!(unique.into_inner(), None);
99
100        let mut unique: FromUniqueOrd<Vec<_>, _> = vec![1, 2, 3].into_iter().collect();
101        unique.extend(vec![4]);
102        assert_eq!(unique.get(), Some(&vec![1, 2, 3, 4]));
103        unique.extend(vec![4]);
104        assert_eq!(unique.get(), None);
105    }
106}
collected/from_unique_ord.rs

collected/
from_unique_ord.rs
