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

use core::hash::Hash;
use std::{borrow::Cow, str::FromStr};

use thiserror::Error;

use crate::rules::matcher::{MatchParser, Rule};

#[derive(Error, Debug, Clone)]
pub enum PathError {
    #[error("{0}")]
    Parse(#[from] Box<pest::error::Error<Rule>>),
}

/// Cross Path allowing to recursively retrieve a [FieldValue](crate::FieldValue)
/// from a structure implementing [FieldGetter](crate::FieldGetter).
///
/// # Example:
///
/// ```rust
/// use ::gene_derive::FieldGetter;
/// use ::gene::{XPath, FieldGetter, FieldValue};
///
/// #[derive(FieldGetter)]
/// struct LogData
/// {
///     a: String,
///     b: i32,
///     c: f64,
/// }
///
/// #[derive(FieldGetter)]
/// struct LogEntry
/// {
///     name: String,
///     data: LogData,
/// }
///
/// let e = LogEntry{
///     name: "SomeEntry".into(),
///     data: LogData{
///         a: "SomeData".into(),
///         b: 42,
///         c: 24.0,
///     }
/// };
///
/// let p = XPath::parse(".name").unwrap();
/// assert_eq!(e.get_from_path(&p), Some("SomeEntry".into()));
///
/// let p = XPath::parse(".data.a").unwrap();
/// assert_eq!(e.get_from_path(&p), Some("SomeData".into()));
///
/// let p = XPath::parse(".data.b").unwrap();
/// assert_eq!(e.get_from_path(&p), Some(42.into()));
///
/// let p = XPath::parse(".data.c").unwrap();
/// assert_eq!(e.get_from_path(&p), Some(24.0.into()));
/// ```
#[derive(Clone, Debug, Eq)]
pub struct XPath {
    path: String,
    segments: Vec<String>,
}

impl Hash for XPath {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.path.hash(state)
    }
}

impl FromStr for XPath {
    type Err = PathError;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Self::parse(s)
    }
}

impl PartialEq for XPath {
    #[inline(always)]
    fn eq(&self, other: &Self) -> bool {
        if self.path.len() != other.path.len() {
            return false;
        }

        let mut o = other.path.as_bytes().iter().rev();
        for b in self.path.as_bytes().iter().rev() {
            if Some(b) != o.next() {
                return false;
            }
        }
        true
    }
}

impl std::fmt::Display for XPath {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.path)
    }
}

impl XPath {
    /// builds an `XPath` from a [str]
    #[inline]
    pub fn parse<S: AsRef<str>>(s: S) -> Result<Self, PathError> {
        Ok(XPath {
            path: String::from(s.as_ref()),
            segments: MatchParser::parse_path(s)?,
        })
    }

    /// getter to the segments of the path. If a path has been
    /// built from `.a.b.c` the segments will be `["a", "b", "c"]` as `.` is the
    /// path segments separator
    #[inline(always)]
    pub fn segments(&self) -> &Vec<String> {
        &self.segments
    }

    /// provides an iterator over the segments of the path
    #[inline(always)]
    pub fn iter_segments(&self) -> core::slice::Iter<'_, std::string::String> {
        self.segments.iter()
    }

    #[inline(always)]
    pub fn to_string_lossy(&self) -> Cow<'_, str> {
        Cow::from(&self.path)
    }
}

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

    use super::XPath;

    #[test]
    fn test_path() {
        let s = r#".data.exe.file."with space"."with .""#;
        let p = XPath::from_str(s).unwrap();
        assert_eq!(p.to_string_lossy(), s);
        assert_eq!(p.segments[0], "data");
        assert_eq!(p.segments[1], "exe");
        assert_eq!(p.segments[2], "file");
        assert_eq!(p.segments[3], "with space");
        assert_eq!(p.segments[4], "with .");
        assert_eq!(p, XPath::from_str(s).unwrap());

        let mut i = p.iter_segments();
        assert_eq!(i.next(), Some(&"data".into()));
        assert_eq!(i.next(), Some(&"exe".into()));
        assert_eq!(i.next(), Some(&"file".into()));
        assert_eq!(i.next(), Some(&"with space".into()));
        assert_eq!(i.next(), Some(&"with .".into()));
    }
}