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

// Copyright 2024 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use super::{super::Room, Filter};

/// An enum to represent whether a room is about “people” (strictly 2 users) or
/// “group” (1 or more than 2 users).
///
/// Ideally, we would only want to rely on the
/// [`matrix_sdk::BaseRoom::is_direct`] method, but the rules are a little bit
/// different for this high-level UI API.
///
/// This is implemented this way so that it's impossible to filter by “group”
/// and by “people” at the same time: these criteria are mutually
/// exclusive by design per filter.
#[derive(Copy, Clone, PartialEq)]
pub enum RoomCategory {
    Group,
    People,
}

type DirectTargetsLength = usize;

struct CategoryRoomMatcher<F>
where
    F: Fn(&Room) -> Option<DirectTargetsLength>,
{
    /// _Direct targets_ mean the number of users in a direct room, except us.
    /// So if it returns 1, it means there are 2 users in the direct room.
    number_of_direct_targets: F,
}

impl<F> CategoryRoomMatcher<F>
where
    F: Fn(&Room) -> Option<DirectTargetsLength>,
{
    fn matches(&self, room: &Room, expected_kind: RoomCategory) -> bool {
        let kind = match (self.number_of_direct_targets)(room) {
            // If 1, we are sure it's a direct room between two users. It's the strict
            // definition of the `People` category, all good.
            Some(1) => RoomCategory::People,

            // If smaller than 1, we are not sure it's a direct room, it's then a `Group`.
            // If greater than 1, we are sure it's a direct room but not between
            // two users, so it's a `Group` based on our expectation.
            Some(_) => RoomCategory::Group,

            // Don't know.
            None => return false,
        };

        kind == expected_kind
    }
}

/// Create a new filter that will accept all rooms that fit in the
/// `expected_category`. The category is defined by [`RoomCategory`], see this
/// type to learn more.
pub fn new_filter(expected_category: RoomCategory) -> impl Filter {
    let matcher = CategoryRoomMatcher {
        number_of_direct_targets: move |room| Some(room.direct_targets_length()),
    };

    move |room| -> bool { matcher.matches(room, expected_category) }
}

#[cfg(test)]
mod tests {
    use std::ops::Not;

    use matrix_sdk_test::async_test;
    use ruma::room_id;

    use super::{
        super::{client_and_server_prelude, new_rooms},
        *,
    };

    #[async_test]
    async fn test_kind_is_group() {
        let (client, server, sliding_sync) = client_and_server_prelude().await;
        let [room] = new_rooms([room_id!("!a:b.c")], &client, &server, &sliding_sync).await;

        let matcher = CategoryRoomMatcher { number_of_direct_targets: |_| Some(42) };

        // Expect `People`.
        {
            let expected_kind = RoomCategory::People;

            assert!(matcher.matches(&room, expected_kind).not());
        }

        // Expect `Group`.
        {
            let expected_kind = RoomCategory::Group;

            assert!(matcher.matches(&room, expected_kind));
        }
    }

    #[async_test]
    async fn test_kind_is_people() {
        let (client, server, sliding_sync) = client_and_server_prelude().await;
        let [room] = new_rooms([room_id!("!a:b.c")], &client, &server, &sliding_sync).await;

        let matcher = CategoryRoomMatcher { number_of_direct_targets: |_| Some(1) };

        // Expect `People`.
        {
            let expected_kind = RoomCategory::People;

            assert!(matcher.matches(&room, expected_kind));
        }

        // Expect `Group`.
        {
            let expected_kind = RoomCategory::Group;

            assert!(matcher.matches(&room, expected_kind).not());
        }
    }

    #[async_test]
    async fn test_room_kind_cannot_be_found() {
        let (client, server, sliding_sync) = client_and_server_prelude().await;
        let [room] = new_rooms([room_id!("!a:b.c")], &client, &server, &sliding_sync).await;

        let matcher = CategoryRoomMatcher { number_of_direct_targets: |_| None };

        assert!(matcher.matches(&room, RoomCategory::Group).not());
    }
}