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

// This file is part of Gear.

// Copyright (C) 2022-2024 Gear Technologies Inc.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

//! Module for map's iterator primitives.
//!
//! Map's iterators primitives declares the ability
//! to iter through defined generic `Item` over the map
//! with specified (associated) types of iterators
//! for drain or just iter elements.
//!
//! `DrainIter` used for element's removal
//! on each iteration, while `Iter` used for
//! just checking them.

use super::TransposeCallback;
use core::marker::PhantomData;

/// Represents iterable logic for double key maps
/// (Key1 -> Key2 -> Value).
///
/// Returns the iterators over specified (associated)
/// type of the first key's items.
pub trait IterableByKeyMap<Item> {
    /// Map's first key type.
    type Key;
    /// Removal iterator type.
    type DrainIter: Iterator<Item = Item>;
    /// Getting iterator type.
    type Iter: Iterator<Item = Item>;

    /// Creates the removal iterator over double map Items.
    fn drain_key(key: Self::Key) -> Self::DrainIter;
    /// Creates the getting iterator over double map Items.
    fn iter_key(key: Self::Key) -> Self::Iter;
}

/// Represents iterable logic for single key maps
/// (Key -> Value).
pub trait IterableMap<Item> {
    /// Removal iterator type.
    type DrainIter: Iterator<Item = Item>;
    /// Getting iterator type.
    type Iter: Iterator<Item = Item>;

    /// Creates the removal iterator over map Items.
    fn drain() -> Self::DrainIter;
    /// Creates the getting iterator over map Items.
    fn iter() -> Self::Iter;
}

/// Represents iterable over second keys logic for double key maps
/// (Key1 -> Key2 -> Value).
///
/// Returns the iterators over specified (associated)
/// type of the second map keys by given first key.
pub trait KeyIterableByKeyMap {
    /// Map's first key type.
    type Key1;
    /// Map's second key type.
    type Key2;
    /// Removal iterator type.
    type DrainIter: Iterator<Item = Self::Key2>;
    /// Getting iterator type.
    type Iter: Iterator<Item = Self::Key2>;

    /// Creates the removal iterator over double map Items.
    fn drain_prefix_keys(key: Self::Key1) -> Self::DrainIter;
    /// Creates the getting iterator over double map Items.
    fn iter_prefix_keys(key: Self::Key1) -> Self::Iter;
}

/// Transpose callback for getting first element of tuple.
pub struct GetFirstPos;

// `TransposeCallback` implementation for tuple with two elements.
impl<K, V> TransposeCallback<(K, V), K> for GetFirstPos {
    fn call(arg: (K, V)) -> K {
        arg.0
    }
}

// `TransposeCallback` implementation for tuple with three elements.
impl<K1, K2, V> TransposeCallback<(K1, K2, V), K1> for GetFirstPos {
    fn call(arg: (K1, K2, V)) -> K1 {
        arg.0
    }
}

/// Transpose callback for getting second element of tuple.
pub struct GetSecondPos;

// `TransposeCallback` implementation for tuple with two elements.
impl<K, V> TransposeCallback<(K, V), V> for GetSecondPos {
    fn call(arg: (K, V)) -> V {
        arg.1
    }
}

// `TransposeCallback` implementation for tuple with three elements.
impl<K1, K2, V> TransposeCallback<(K1, K2, V), K2> for GetSecondPos {
    fn call(arg: (K1, K2, V)) -> K2 {
        arg.1
    }
}

/// Transpose callback for getting third element of tuple.
pub struct GetThirdPos;

// `TransposeCallback` implementation for tuple with three elements.
impl<K1, K2, V> TransposeCallback<(K1, K2, V), V> for GetThirdPos {
    fn call(arg: (K1, K2, V)) -> V {
        arg.2
    }
}

/// Represents wrapper for any iterator with ability
/// to transpose `.next()` result.
pub struct IteratorWrap<I, Item = <I as Iterator>::Item, TC = ()>(I, PhantomData<(Item, TC)>)
where
    I: Iterator,
    TC: TransposeCallback<I::Item, Item>;

// Implementation of `From` for any iterator.
impl<I, Item, TC> From<I> for IteratorWrap<I, Item, TC>
where
    I: Iterator,
    TC: TransposeCallback<I::Item, Item>,
{
    fn from(iterator: I) -> Self {
        Self(iterator, PhantomData)
    }
}

// Implementation of `Iterator` itself for the wrapper
// based on inner iterator and transpose callback.
impl<I, Item, TC> Iterator for IteratorWrap<I, Item, TC>
where
    I: Iterator,
    TC: TransposeCallback<I::Item, Item>,
{
    type Item = Item;

    fn next(&mut self) -> Option<Self::Item> {
        self.0.next().map(TC::call)
    }
}