header_config/
lib.rs

1#![deny(missing_docs)]
2
3/*!
4This library parses hierarchic configuration files in a markdown inspired format.
5Therefore the `parse_config` function is provided.
6**/
7
8use header_parsing::parse_header;
9use indexmap::IndexMap;
10use thiserror::Error;
11
12use std::{
13    fs::File,
14    io::{BufRead, BufReader},
15    path::Path,
16};
17
18/// Error if parsing fails.
19#[derive(Debug, Error)]
20pub enum Error {
21    /// Opening file failed.
22    #[error("Failed to open the configuration file")]
23    OpeningFile,
24    /// A subheader doesn't have a header of the right hierarchy level.
25    #[error("Subheader found without a corresponding header")]
26    SubheaderWithoutHeader,
27    /// A key appears multiple times.
28    #[error("Multiple values found for key: {0}")]
29    MultipleKeys(Box<str>),
30    /// Some input issue occured while reading the file.
31    #[error("Input issues")]
32    Input,
33}
34
35impl Error {
36    /// Prints an error message suitable for the specified path.
37    pub fn print_message(&self, path: &Path) {
38        use Error::*;
39        match self {
40            OpeningFile => eprintln!("Opening file \"{}\" failed", path.display()),
41            SubheaderWithoutHeader => {
42                eprintln!(
43                    "File \"{}\" has a subheader without a header",
44                    path.display()
45                )
46            }
47            MultipleKeys(key) => {
48                eprintln!("Path \"{}\" has a duplicate of key {key}", path.display())
49            }
50            Input => eprintln!("Input error while reading \"{}\"", path.display()),
51        }
52    }
53}
54
55/// Parses the configuration file.
56pub fn parse_config(path: &Path) -> Result<IndexMap<Box<str>, Box<str>>, Error> {
57    let Ok(file) = File::open(path) else {
58        return Err(Error::OpeningFile);
59    };
60    let reader = BufReader::new(file);
61
62    let mut map = IndexMap::new();
63
64    let mut key_path = Vec::new();
65    let mut prefix = String::new();
66
67    for line in reader.lines() {
68        let Ok(line) = line else {
69            return Err(Error::Input);
70        };
71        if let Some(success) = parse_header(&mut key_path, &line) {
72            let Ok(changes) = success else {
73                return Err(Error::SubheaderWithoutHeader);
74            };
75
76            changes.apply();
77            prefix.clear();
78            for header in &key_path {
79                prefix.push_str(header);
80                prefix.push(':');
81            }
82            continue;
83        }
84
85        let line = line.trim();
86        if line.is_empty() {
87            continue;
88        }
89
90        let (key, value) = line
91            .split_once(char::is_whitespace)
92            .map_or_else(|| (line, ""), |(key, value)| (key, value.trim_start()));
93
94        let full_key = format!("{prefix}{key}").into();
95        if map.contains_key(&full_key) {
96            return Err(Error::MultipleKeys(full_key));
97        }
98        map.insert(full_key, value.into());
99    }
100
101    Ok(map)
102}
103
104#[cfg(test)]
105mod tests {
106    #![allow(clippy::unwrap_used)]
107
108    use super::{Error, parse_config};
109    use std::fs::write;
110
111    fn parse(name: &str, content: &str) -> Result<super::IndexMap<Box<str>, Box<str>>, Error> {
112        let path = std::env::temp_dir().join(name);
113        write(&path, content).unwrap();
114        let result = parse_config(&path);
115        let _ = std::fs::remove_file(path);
116        result
117    }
118
119    #[test]
120    fn flattens_nested_headers() {
121        let map = parse(
122            "header_config_nested.hc",
123            "root value\n\n# A\n\nkey 1\n\n# B\n\nkey 2\n\n## Sub\n\ndeep 3\nempty\n",
124        )
125        .unwrap();
126
127        assert_eq!(map.get("root").map(AsRef::as_ref), Some("value"));
128        assert_eq!(map.get("A:key").map(AsRef::as_ref), Some("1"));
129        assert_eq!(map.get("B:key").map(AsRef::as_ref), Some("2"));
130        assert_eq!(map.get("B:Sub:deep").map(AsRef::as_ref), Some("3"));
131        assert_eq!(map.get("B:Sub:empty").map(AsRef::as_ref), Some(""));
132    }
133
134    #[test]
135    fn rejects_duplicate_keys() {
136        let result = parse("header_config_dup.hc", "# A\n\nkey 1\nkey 2\n");
137        assert!(matches!(result, Err(Error::MultipleKeys(key)) if &*key == "A:key"));
138    }
139
140    #[test]
141    fn rejects_orphan_subheader() {
142        let result = parse("header_config_orphan.hc", "## Sub\n\nkey 1\n");
143        assert!(matches!(result, Err(Error::SubheaderWithoutHeader)));
144    }
145}
header_config/lib.rs

header_config/
lib.rs
