date_time_formatter 0.3.0

date-time-formatter-rs is a Rust crate that provides a simple and efficient way to parse and format date and time values. It is a rewrite of a subset of the Java time library, and aims to match its behaviour.
Documentation 
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

// Copyright (C) 2025 Palantir
// 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 2 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, write to the Free Software Foundation, Inc., 59
// Temple Place, Suite 330, Boston, MA 02111-1307 USA
// sbhatia@palantir.com
// "CLASSPATH" EXCEPTION TO THE GPL
// Certain source files distributed by Oracle America and/or its affiliates are
// subject to the following clarification and special exception to the GPL, but
// only where Oracle has expressly included in the particular source file's header
// the words "Oracle designates this particular file as subject to the "Classpath"
// exception as provided by Oracle in the LICENSE file that accompanied this code."
// Linking this library statically or dynamically with other modules is making
// a combined work based on this library.  Thus, the terms and conditions of
// the GNU General Public License cover the whole combination.
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules,
// and to copy and distribute the resulting executable under terms of your
// choice, provided that you also meet, for each linked independent module,
// the terms and conditions of the license of that module.  An independent
// module is a module which is not derived from or based on this library.  If
// you modify this library, you may extend this exception to your version of
// the library, but you are not obligated to do so.  If you do not wish to do
// so, delete this exception statement from your version. "

use std::collections::HashSet;

use crate::{
    date_time_formatter::DateTimeFormatter, decimal_style::DecimalStyle, parsed::Parsed,
    resolver_style::ResolverStyle, temporal_field::TemporalField,
};

pub struct DateTimeParseContext<'a> {
    formatter: &'a DateTimeFormatter,
    case_sensitive: bool,
    strict: bool,
    parsed: Vec<Parsed>,
}

impl<'a> DateTimeParseContext<'a> {
    pub fn new(formatter: &'a DateTimeFormatter) -> Self {
        DateTimeParseContext {
            formatter,
            // We set case sensitive to false by default
            case_sensitive: false,
            strict: true,
            parsed: vec![Parsed::new()],
        }
    }

    pub fn get_decimal_style(&self) -> &DecimalStyle {
        self.formatter.get_decimal_style()
    }

    pub fn sub_sequence_equals(
        &self,
        cs1: &str,
        offset1: usize,
        cs2: &str,
        offset2: usize,
        length: usize,
    ) -> bool {
        if offset1 + length > cs1.len() || offset2 + length > cs2.len() {
            return false;
        }

        let slice1 = &cs1[offset1..offset1 + length];
        let slice2 = &cs2[offset2..offset2 + length];

        if self.case_sensitive {
            slice1 == slice2
        } else {
            slice1.eq_ignore_ascii_case(slice2)
        }
    }

    pub fn char_equals(&self, ch1: char, ch2: char) -> bool {
        if self.case_sensitive {
            return ch1 == ch2;
        }
        DateTimeParseContext::char_equals_ignore_case(ch1, ch2)
    }

    fn char_equals_ignore_case(c1: char, c2: char) -> bool {
        c1 == c2 || c1.eq_ignore_ascii_case(&c2)
    }

    pub fn start_optional(&mut self) -> Result<(), String> {
        let cloned_current_parsed = self.current_parsed()?.clone();
        self.parsed.push(cloned_current_parsed);
        Ok(())
    }

    pub fn end_optional(&mut self, successful: bool) {
        if successful {
            self.parsed.remove(self.parsed.len() - 2);
        } else {
            self.parsed.remove(self.parsed.len() - 1);
        }
    }

    pub fn current_parsed(&mut self) -> Result<&mut Parsed, String> {
        if let Some(parsed) = self.parsed.last_mut() {
            return Ok(parsed);
        }
        Err("Parsed should always have at least one element".to_owned())
    }

    pub fn resolve_to_parsed(
        &mut self,
        resolver_style: &ResolverStyle,
        resolver_fields: &HashSet<TemporalField>,
    ) -> Result<Parsed, String> {
        self.current_parsed()?
            .resolve(resolver_style, resolver_fields)
    }

    pub fn set_parsed_field(
        &mut self,
        field: TemporalField,
        value: i64,
        error_pos: isize,
        success_pos: isize,
    ) -> Result<isize, String> {
        match self.current_parsed()?.field_values.insert(field, value) {
            Some(old) => {
                if old != value {
                    return Ok(!error_pos);
                }
                Ok(success_pos)
            }
            None => Ok(success_pos),
        }
    }

    pub fn is_strict(&self) -> bool {
        self.strict
    }

    pub fn is_case_sensitive(&self) -> bool {
        self.case_sensitive
    }
}