maj/src/gemini.rs

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/// This module implements a simple text/gemini parser based on the description
/// here: https://gemini.circumlunar.space/docs/specification.html
use std::io::Write;
/// Individual nodes of the document. Each node correlates to a line in the file.
#[derive(Debug, PartialEq, Eq)]
pub enum Node {
/// Text lines are the most fundamental line type - any line which does not
/// match the definition of another line type defined below defaults to
/// being a text line. The majority of lines in a typical text/gemini document will be text lines.
Text(String),
/// Lines beginning with the two characters "=>" are link lines, which have the following syntax:
///
/// ```gemini
/// =>[<whitespace>]<URL>[<whitespace><USER-FRIENDLY LINK NAME>]
/// ```
///
/// where:
///
/// * `<whitespace>` is any non-zero number of consecutive spaces or tabs
/// * Square brackets indicate that the enclosed content is optional.
/// * `<URL>` is a URL, which may be absolute or relative. If the URL
/// does not include a scheme, a scheme of `gemini://` is implied.
Link { to: String, name: Option<String> },
/// Any line whose first three characters are "```" (i.e. three consecutive
/// back ticks with no leading whitespace) are preformatted toggle lines.
/// These lines should NOT be included in the rendered output shown to the
/// user. Instead, these lines toggle the parser between preformatted mode
/// being "on" or "off". Preformatted mode should be "off" at the beginning
/// of a document. The current status of preformatted mode is the only
/// internal state a parser is required to maintain. When preformatted mode
/// is "on", the usual rules for identifying line types are suspended, and
/// all lines should be identified as preformatted text lines (see 5.4.4).
///
/// Preformatted text lines should be presented to the user in a "neutral",
/// monowidth font without any alteration to whitespace or stylistic
/// enhancements. Graphical clients should use scrolling mechanisms to present
/// preformatted text lines which are longer than the client viewport, in
/// preference to wrapping. In displaying preformatted text lines, clients
/// should keep in mind applications like ASCII art and computer source
/// code: in particular, source code in languages with significant whitespace
/// (e.g. Python) should be able to be copied and pasted from the client into
/// a file and interpreted/compiled without any problems arising from the
/// client's manner of displaying them.
Preformatted(String),
/// Lines beginning with "#" are heading lines. Heading lines consist of one,
/// two or three consecutive "#" characters, followed by optional whitespace,
/// followed by heading text. The number of # characters indicates the "level"
/// of header; #, ## and ### can be thought of as analogous to `<h1>`, `<h2>`
/// and `<h3>` in HTML.
///
/// Heading text should be presented to the user, and clients MAY use special
/// formatting, e.g. a larger or bold font, to indicate its status as a header
/// (simple clients may simply print the line, including its leading #s,
/// without any styling at all). However, the main motivation for the
/// definition of heading lines is not stylistic but to provide a
/// machine-readable representation of the internal structure of the document.
/// Advanced clients can use this information to, e.g. display an automatically
/// generated and hierarchically formatted "table of contents" for a long
/// document in a side-pane, allowing users to easily jump to specific sections
/// without excessive scrolling. CMS-style tools automatically generating menus
/// or Atom/RSS feeds for a directory of text/gemini files can use first
/// heading in the file as a human-friendly title.
Heading { level: u8, body: String },
/// Lines beginning with "* " are unordered list items. This line type exists
/// purely for stylistic reasons. The * may be replaced in advanced clients by
/// a bullet symbol. Any text after the "* " should be presented to the user as
/// if it were a text line, i.e. wrapped to fit the viewport and formatted
/// "nicely". Advanced clients can take the space of the bullet symbol into
/// account when wrapping long list items to ensure that all lines of text
/// corresponding to the item are offset an equal distance from the left of the screen.
ListItem(String),
/// Lines beginning with ">" are quote lines. This line type exists so that
/// advanced clients may use distinct styling to convey to readers the important
/// semantic information that certain text is being quoted from an external
/// source. For example, when wrapping long lines to the the viewport, each
/// resultant line may have a ">" symbol placed at the front.
Quote(String),
}
pub fn parse(doc: &str) -> Vec<Node> {
let mut result: Vec<Node> = vec![];
let mut collect_preformatted: bool = false;
let mut preformatted_buffer: Vec<u8> = vec![];
for line in doc.lines() {
if line == "```" {
collect_preformatted = !collect_preformatted;
if !collect_preformatted {
result.push(Node::Preformatted(
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String::from_utf8(preformatted_buffer)
.unwrap()
.trim_end()
.to_string(),
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));
preformatted_buffer = vec![];
}
continue;
}
if collect_preformatted && line != "```" {
write!(preformatted_buffer, "{}\n", line).unwrap();
continue;
}
// Quotes
if line.starts_with(">") {
result.push(Node::Quote(line[1..].trim().to_string()));
continue;
}
// List items
if line.starts_with("*") {
result.push(Node::ListItem(line[1..].trim().to_string()));
continue;
}
// Headings
if line.starts_with("###") {
result.push(Node::Heading {
level: 3,
body: line[3..].trim().to_string(),
});
continue;
}
if line.starts_with("##") {
result.push(Node::Heading {
level: 2,
body: line[2..].trim().to_string(),
});
continue;
}
if line.starts_with("#") {
result.push(Node::Heading {
level: 1,
body: line[1..].trim().to_string(),
});
continue;
}
// Links
if line.starts_with("=>") {
let sp = line[2..].split_ascii_whitespace().collect::<Vec<&str>>();
match sp.len() {
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1 => result.push(Node::Link {
to: sp[0].trim().to_string(),
name: None,
}),
_ => result.push(Node::Link {
to: sp[0].trim().to_string(),
name: Some(sp[1..].join(" ").trim().to_string()),
}),
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}
continue;
}
result.push(Node::Text(line.to_string()));
}
result
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn basic() {
let _ = pretty_env_logger::try_init();
let msg = include_str!("../majc/src/help.gmi");
let doc = super::parse(msg);
assert_ne!(doc.len(), 0);
}
#[test]
fn quote() {
let _ = pretty_env_logger::try_init();
let msg = ">hi there";
let expected: Vec<Node> = vec![Node::Quote("hi there".to_string())];
assert_eq!(expected, parse(msg));
}
#[test]
fn list() {
let _ = pretty_env_logger::try_init();
let msg = "*hi there";
let expected: Vec<Node> = vec![Node::ListItem("hi there".to_string())];
assert_eq!(expected, parse(msg));
}
#[test]
fn preformatted() {
let _ = pretty_env_logger::try_init();
let msg = "```\n\
hi there\n\
```\n\
\n\
Test\n";
let expected: Vec<Node> = vec![
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Node::Preformatted("hi there".to_string()),
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Node::Text(String::new()),
Node::Text("Test".to_string()),
];
assert_eq!(expected, parse(msg));
}
#[test]
fn header() {
let _ = pretty_env_logger::try_init();
let msg = "#hi\n##there\n### my friends";
let expected: Vec<Node> = vec![
Node::Heading {
level: 1,
body: "hi".to_string(),
},
Node::Heading {
level: 2,
body: "there".to_string(),
},
Node::Heading {
level: 3,
body: "my friends".to_string(),
},
];
assert_eq!(expected, parse(msg));
}
#[test]
fn link() {
let _ = pretty_env_logger::try_init();
let msg = "=>/\n=> / Go home";
let expected: Vec<Node> = vec![
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Node::Link {
to: "/".to_string(),
name: None,
},
Node::Link {
to: "/".to_string(),
name: Some("Go home".to_string()),
},
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];
assert_eq!(expected, parse(msg));
}
}