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

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("todo")]
    ToDo,
}

#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct DocumentId(String);

impl std::convert::AsRef<str> for DocumentId {
    fn as_ref(&self) -> &str {
        self.0.as_ref()
    }
}

impl std::convert::TryFrom<&str> for DocumentId {
    type Error = Error;

    fn try_from(s: &str) -> Result<Self, Self::Error> {
        Self::try_from(s.to_string())
    }
}

impl std::convert::TryFrom<String> for DocumentId {
    type Error = Error;

    fn try_from(s: String) -> Result<Self, Self::Error> {
        // <https://firebase.google.com/docs/firestore/quotas#collections_documents_and_fields>
        if s.len() > 1_500 {
            return Err(Error::ToDo);
        }

        if s.contains('/') {
            return Err(Error::ToDo);
        }

        if s == "." || s == ".." {
            return Err(Error::ToDo);
        }

        if s.starts_with("__") && s.ends_with("__") {
            return Err(Error::ToDo);
        }

        // TODO: Datastore entities

        Ok(Self(s))
    }
}

impl std::fmt::Display for DocumentId {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.0.fmt(f)
    }
}

impl std::str::FromStr for DocumentId {
    type Err = Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Self::try_from(s)
    }
}

#[cfg(test)]
mod tests {
    use std::str::FromStr;

    use super::*;

    #[test]
    fn test() -> anyhow::Result<()> {
        let s = "chatroom1";
        let document_id = DocumentId::from_str(s)?;
        assert_eq!(document_id.to_string(), s);

        assert_eq!(document_id.as_ref(), s);
        Ok(())
    }

    #[test]
    fn test_impl_from_str_and_impl_try_from_string() -> anyhow::Result<()> {
        for (s, expected) in [
            ("chatroom1", true),
            ("x".repeat(1501).as_ref(), false),
            ("x".repeat(1500).as_ref(), true),
            ("chat/room1", false),
            (".", false),
            (".x", true),
            ("..", false),
            ("..x", true),
            ("__x__", false),
            ("__x", true),
            ("x__", true),
        ] {
            assert_eq!(DocumentId::from_str(s).is_ok(), expected);
            assert_eq!(DocumentId::try_from(s.to_string()).is_ok(), expected);
            if expected {
                assert_eq!(
                    DocumentId::from_str(s)?,
                    DocumentId::try_from(s.to_string())?
                );
                assert_eq!(DocumentId::from_str(s)?.to_string(), s);
            }
        }
        Ok(())
    }
}