1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
use crate::shared::file_like::FileLike;
use crate::shared::tree_like::{TreeLike, TreeLikeMut};
use crate::shared::SharedResult;
use std::collections::HashSet;
use uuid::Uuid;

pub trait StagedTreeLike: TreeLike {
    type Base: TreeLike<F = Self::F>;
    type Staged: TreeLike<F = Self::F>;

    fn base(&self) -> &Self::Base;
    fn staged(&self) -> &Self::Staged;
}

// todo: make this trait not generic once associated type bounds are stabilized
// https://rust-lang.github.io/rfcs/2289-associated-type-bounds.html
pub trait StagedTreeLikeMut<Base, Staged>:
    StagedTreeLike<Base = Base, Staged = Staged> + TreeLikeMut
where
    Base: TreeLike<F = Self::F>,
    Staged: TreeLikeMut<F = Self::F>,
{
    fn staged_mut(&mut self) -> &mut Self::Staged;

    fn prune(&mut self) -> SharedResult<()> {
        let mut prunable = vec![];
        for id in self.staged().ids() {
            if let Some(staged) = self.staged().maybe_find(id) {
                if let Some(base) = self.base().maybe_find(id) {
                    if staged == base {
                        prunable.push(*id);
                    }
                }
            }
        }

        for id in prunable {
            self.staged_mut().remove(id)?;
        }
        Ok(())
    }

    fn pruned(mut self) -> SharedResult<Self> {
        self.prune()?;
        Ok(self)
    }
}

#[derive(Debug)]
pub struct StagedTree<Base, Staged>
where
    Base: TreeLike,
    Staged: TreeLike<F = Base::F>,
{
    pub base: Base,
    pub staged: Staged,
    pub removed: HashSet<Uuid>,
}

impl<Base, Staged> StagedTree<Base, Staged>
where
    Base: TreeLike,
    Staged: TreeLike<F = Base::F>,
{
    pub fn new(base: Base, staged: Staged) -> Self {
        Self { base, staged, removed: HashSet::new() }
    }
}

impl<Base> StagedTree<Base, Option<Base::F>>
where
    Base: TreeLike,
{
    pub fn removal(base: Base, removed: HashSet<Uuid>) -> Self {
        Self { base, staged: None, removed }
    }
}

impl<Base, Staged> TreeLike for StagedTree<Base, Staged>
where
    Base: TreeLike,
    Staged: TreeLike<F = Base::F>,
{
    type F = Base::F;

    fn ids(&self) -> HashSet<&Uuid> {
        self.base()
            .ids()
            .into_iter()
            .chain(self.staged().ids())
            .filter(|id| !self.removed.contains(id))
            .collect()
    }

    fn maybe_find(&self, id: &Uuid) -> Option<&Self::F> {
        if self.removed.contains(id) {
            None
        } else {
            self.staged()
                .maybe_find(id)
                .or_else(|| self.base().maybe_find(id))
        }
    }
}

impl<Base, Staged> TreeLikeMut for StagedTree<Base, Staged>
where
    Base: TreeLike,
    Staged: TreeLikeMut<F = Base::F>,
{
    fn insert(&mut self, f: Self::F) -> SharedResult<Option<Self::F>> {
        self.removed.remove(f.id());
        if let Some(base) = self.base.maybe_find(f.id()) {
            if *base == f {
                return self.staged.remove(*f.id());
            }
        }

        self.staged.insert(f)
    }

    fn remove(&mut self, id: Uuid) -> SharedResult<Option<Self::F>> {
        self.removed.insert(id);
        if let Some(staged) = self.staged.remove(id)? {
            Ok(Some(staged))
        } else {
            Ok(self.base.maybe_find(&id).cloned())
        }
    }

    fn clear(&mut self) -> SharedResult<()> {
        self.removed.extend(self.owned_ids());
        Ok(())
    }
}

impl<Base, Staged> StagedTreeLike for StagedTree<Base, Staged>
where
    Base: TreeLike,
    Staged: TreeLike<F = Base::F>,
{
    type Base = Base;
    type Staged = Staged;

    fn base(&self) -> &Self::Base {
        &self.base
    }

    fn staged(&self) -> &Self::Staged {
        &self.staged
    }
}

impl<Base, Staged> StagedTreeLikeMut<Base, Staged> for StagedTree<Base, Staged>
where
    Base: TreeLike,
    Staged: TreeLikeMut<F = Base::F>,
{
    fn staged_mut(&mut self) -> &mut Self::Staged {
        &mut self.staged
    }
}