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|
const KNOWN_TAGS: &[&str] = &[
"info",
"comment",
"error",
"question",
"highlight",
"warning",
];
#[derive(Debug, Clone, PartialEq)]
pub enum Segment {
Plain(String),
Tagged { tag: String, content: String },
}
pub fn parse_format_string(input: &str) -> Result<Vec<Segment>, String> {
let mut segments: Vec<Segment> = Vec::new();
let mut chars = input.char_indices().peekable();
let mut plain_buf = String::new();
while let Some(&(i, ch)) = chars.peek() {
if ch == '<' {
// Try to match an opening tag
if let Some((tag, after_tag)) = try_parse_open_tag(input, i) {
// Flush plain buffer
if !plain_buf.is_empty() {
segments.push(Segment::Plain(std::mem::take(&mut plain_buf)));
}
// Advance past the opening tag
while chars.peek().is_some_and(|&(j, _)| j < after_tag) {
chars.next();
}
// Collect content until closing tag
let closing = format!("</{tag}>");
let content_start = after_tag;
let Some(close_pos) = input[content_start..].find(&closing) else {
return Err(format!("unclosed <{tag}> tag"));
};
let content_end = content_start + close_pos;
let content = &input[content_start..content_end];
// Check for nested tags
if contains_known_tag(content) {
return Err(format!("nested tags are not supported inside <{tag}>"));
}
segments.push(Segment::Tagged {
tag: tag.to_string(),
content: content.to_string(),
});
// Advance past the closing tag
let after_close = content_end + closing.len();
while chars.peek().is_some_and(|&(j, _)| j < after_close) {
chars.next();
}
} else {
// Not a known tag, treat as literal
plain_buf.push(ch);
chars.next();
}
} else {
plain_buf.push(ch);
chars.next();
}
}
if !plain_buf.is_empty() {
segments.push(Segment::Plain(plain_buf));
}
Ok(segments)
}
/// Try to parse an opening tag like `<info>` at position `pos`.
/// Returns `(tag_name, byte_index_after_closing_angle)` on success.
fn try_parse_open_tag(input: &str, pos: usize) -> Option<(&str, usize)> {
let rest = &input[pos + 1..]; // skip '<'
// Must not start with '/'
if rest.starts_with('/') {
return None;
}
let end = rest.find('>')?;
let tag_name = &rest[..end];
if KNOWN_TAGS.contains(&tag_name) {
Some((tag_name, pos + 1 + end + 1))
} else {
None
}
}
/// Check if a string contains any known opening tag (for nesting detection).
fn contains_known_tag(s: &str) -> bool {
for tag in KNOWN_TAGS {
if s.contains(&format!("<{tag}>")) {
return true;
}
}
false
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn plain_text_only() {
let result = parse_format_string("hello world").unwrap();
assert_eq!(result, vec![Segment::Plain("hello world".into())]);
}
#[test]
fn single_tag() {
let result = parse_format_string("<info>hello</info>").unwrap();
assert_eq!(
result,
vec![Segment::Tagged {
tag: "info".into(),
content: "hello".into()
}]
);
}
#[test]
fn tag_with_placeholder() {
let result = parse_format_string("<info>Removing {name}</info>").unwrap();
assert_eq!(
result,
vec![Segment::Tagged {
tag: "info".into(),
content: "Removing {name}".into()
}]
);
}
#[test]
fn multiple_tags() {
let result = parse_format_string("<info>{}</info> : <comment>{}</comment>").unwrap();
assert_eq!(
result,
vec![
Segment::Tagged {
tag: "info".into(),
content: "{}".into()
},
Segment::Plain(" : ".into()),
Segment::Tagged {
tag: "comment".into(),
content: "{}".into()
},
]
);
}
#[test]
fn all_tag_types() {
for tag in KNOWN_TAGS {
let input = format!("<{tag}>text</{tag}>");
let result = parse_format_string(&input).unwrap();
assert_eq!(
result,
vec![Segment::Tagged {
tag: tag.to_string(),
content: "text".into()
}]
);
}
}
#[test]
fn unknown_tag_treated_as_literal() {
let result = parse_format_string("<bold>text</bold>").unwrap();
assert_eq!(result, vec![Segment::Plain("<bold>text</bold>".into())]);
}
#[test]
fn unclosed_tag_error() {
let result = parse_format_string("<info>text");
assert!(result.is_err());
assert!(result.unwrap_err().contains("unclosed"));
}
#[test]
fn nested_tag_error() {
let result = parse_format_string("<info><comment>text</comment></info>");
assert!(result.is_err());
assert!(result.unwrap_err().contains("nested"));
}
#[test]
fn escaped_braces() {
let result = parse_format_string("<info>{{literal}}</info>").unwrap();
assert_eq!(
result,
vec![Segment::Tagged {
tag: "info".into(),
content: "{{literal}}".into()
}]
);
}
#[test]
fn adjacent_tags() {
let result = parse_format_string("<info>a</info><comment>b</comment>").unwrap();
assert_eq!(
result,
vec![
Segment::Tagged {
tag: "info".into(),
content: "a".into()
},
Segment::Tagged {
tag: "comment".into(),
content: "b".into()
},
]
);
}
#[test]
fn plain_before_and_after_tag() {
let result = parse_format_string("before <info>middle</info> after").unwrap();
assert_eq!(
result,
vec![
Segment::Plain("before ".into()),
Segment::Tagged {
tag: "info".into(),
content: "middle".into()
},
Segment::Plain(" after".into()),
]
);
}
#[test]
fn empty_content_tag() {
let result = parse_format_string("<info></info>").unwrap();
assert_eq!(
result,
vec![Segment::Tagged {
tag: "info".into(),
content: String::new()
}]
);
}
}
|
