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use std::fmt;
/// The content part of a file that fills in a template.
pub struct Templated<'r> {
pub frontmatter: Frontmatter<'r>,
pub content: &'r str,
}
impl<'r> Templated<'r> {
pub fn parse(raw: &'r str) -> Result<Self, TemplateError> {
tracing::trace!("parsing Templated");
let (front, content) = match raw.strip_prefix("---\n") {
None => return Err(TemplateError::MissingFrontmatter),
Some(no_start) => match no_start.split_once("\n---\n") {
None => return Err(TemplateError::MissingFrontmatter),
Some((front, content)) => (front, content),
},
};
tracing::trace!("isolated frontmatter");
Ok(Self {
frontmatter: Frontmatter::parse(front)?,
content,
})
}
}
/// frontmatter from a template
///
/// Frontmatter must always be at the top of the file bounded by `---`
///
/// ```plain
/// ---
/// title=Page Title
/// description=OpenGraph description
/// ---
///
/// Page content
/// ```
pub struct Frontmatter<'r> {
entries: Vec<(&'r str, &'r str)>,
}
impl<'r> Frontmatter<'r> {
pub fn parse(raw: &'r str) -> Result<Self, TemplateError> {
let mut entries = vec![];
for line in raw.lines() {
let trimmed = line.trim();
if trimmed.is_empty() || trimmed.starts_with('#') {
// Skip over blank lines and comments
continue;
}
let (key, value) = match trimmed.split_once('=') {
None => {
return Err(TemplateError::MalformedFrontmatterEntry {
line: trimmed.to_owned(),
});
}
Some(tup) => tup,
};
entries.push((key.trim(), value.trim()));
tracing::trace!("pushed frontmatter entry {} successfully", key.trim());
}
Ok(Self { entries })
}
pub fn get(&self, key: &str) -> Option<&str> {
self.entries
.iter()
.find(|(k, _)| *k == key)
.map(|(_, v)| *v)
}
/// Convenience for `[Frontmatter::get()]` and `to_owned()`
pub fn get_owned(&self, key: &str) -> Option<String> {
self.entries
.iter()
.find(|(k, _)| *k == key)
.map(|(_, v)| (*v).to_owned())
}
pub fn get_many(&self, key: &str) -> Vec<&str> {
// this could probably be a filter_map() but the explicit filter and
// then map seems cleaner
self.entries
.iter()
.filter(|(k, _)| *k == key)
.map(|(_, v)| *v)
.collect()
}
}
#[derive(Debug)]
pub enum TemplateError {
MissingFrontmatter,
MalformedFrontmatterEntry { line: String },
}
impl std::error::Error for TemplateError {}
impl fmt::Display for TemplateError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::MissingFrontmatter => write!(f, "the template does not have frontmatter"),
Self::MalformedFrontmatterEntry { line } => {
write!(f, "this frontmatter is malformed: {line}")
}
}
}
}
#[cfg(test)]
mod test {
use crate::templated::{Frontmatter, Templated};
#[test]
fn frontmatter_parse() {
let frntmtr = "key=value\nkey2=value2";
assert!(Frontmatter::parse(frntmtr).is_ok())
}
#[test]
fn frontmatter_fails_on_invalid_line() {
let front = "key1=value1\nincorrect line";
assert!(Frontmatter::parse(front).is_err())
}
#[test]
fn templated_parse() {
let tempalted = "---\ntitle=Title!\n---\nContent line!";
assert!(Templated::parse(tempalted).is_ok())
}
#[test]
fn templated_doesnt_eat_frontmatter_line() {
let templated = "---\ntitle=Title---\nContent";
assert!(Templated::parse(templated).is_err());
}
#[test]
fn templated_parses_correct() {
let raw = "---\ntitle=Title!\n---\n<p>Paragraph!</p>";
let tmpl = Templated::parse(raw).unwrap();
assert_eq!(tmpl.frontmatter.get("title").unwrap(), "Title!");
assert_eq!(tmpl.content, "<p>Paragraph!</p>")
}
}
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