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

use crate::stream::Stream;

#[derive(Debug)]
pub enum ReadVersion {
    Origin,
    Version(u64),
}

/// The `ExpectedVersion` used to define optimistic concurrency
#[derive(Debug, PartialEq)]
pub enum ExpectedVersion {
    /// Define that we expect a stream in any version
    AnyVersion,
    /// Define that we expect a non existing stream
    NoStream,
    /// Define that we expect an existing stream
    StreamExists,
    /// Define that we expect a stream in a particular version
    Version(u64),
}

impl ExpectedVersion {
    #[must_use]
    pub const fn verify(stream: &Stream, expected: &Self) -> ExpectedVersionResult {
        match expected {
            _ if stream.is_persisted() && stream.deleted_at.is_some() => {
                ExpectedVersionResult::StreamDeleted
            }
            Self::NoStream | Self::Version(0) | Self::AnyVersion if !stream.is_persisted() => {
                ExpectedVersionResult::NeedCreation
            }

            Self::StreamExists if !stream.is_persisted() => {
                ExpectedVersionResult::StreamDoesntExists
            }

            Self::AnyVersion | Self::StreamExists if stream.is_persisted() => {
                ExpectedVersionResult::Ok
            }

            Self::Version(version)
                if stream.is_persisted() && stream.stream_version == *version =>
            {
                ExpectedVersionResult::Ok
            }

            Self::NoStream if stream.is_persisted() && stream.stream_version != 0 => {
                ExpectedVersionResult::StreamAlreadyExists
            }

            Self::NoStream if stream.is_persisted() && stream.stream_version == 0 => {
                ExpectedVersionResult::Ok
            }
            _ => ExpectedVersionResult::WrongExpectedVersion,
        }
    }
}

#[derive(Debug, PartialEq)]
pub enum ExpectedVersionResult {
    NeedCreation,
    Ok,
    StreamAlreadyExists,
    StreamDeleted,
    StreamDoesntExists,
    WrongExpectedVersion,
}

#[cfg(test)]
mod test {
    use super::*;
    use chrono::Utc;
    use std::str::FromStr;

    #[test]
    fn test_that_an_unexisting_stream_with_any_is_created() {
        let stream = Stream::from_str("stream_1").unwrap();

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::AnyVersion),
            ExpectedVersionResult::NeedCreation
        );
    }

    #[test]
    fn test_validation_result_need_creation() {
        let mut stream = Stream::from_str("stream_1").unwrap();
        stream.stream_id = 1;
        stream.deleted_at = Some(Utc::now());

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::AnyVersion),
            ExpectedVersionResult::StreamDeleted
        );

        stream.stream_id = 0;
        stream.deleted_at = None;

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::NoStream),
            ExpectedVersionResult::NeedCreation
        );

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::Version(0)),
            ExpectedVersionResult::NeedCreation
        );

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::AnyVersion),
            ExpectedVersionResult::NeedCreation
        );

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::StreamExists),
            ExpectedVersionResult::StreamDoesntExists
        );

        stream.stream_id = 1;
        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::AnyVersion),
            ExpectedVersionResult::Ok
        );

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::StreamExists),
            ExpectedVersionResult::Ok
        );

        stream.stream_version = 1;

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::Version(1)),
            ExpectedVersionResult::Ok
        );

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::NoStream),
            ExpectedVersionResult::StreamAlreadyExists
        );

        stream.stream_version = 0;

        assert_eq!(
            ExpectedVersion::verify(&stream, &ExpectedVersion::NoStream),
            ExpectedVersionResult::Ok
        );
    }
}