md2gemtext/src/lib.rs

279 lines
8.9 KiB
Rust

use pulldown_cmark as md;
/// Converts a given string of Markdown to semi-equivalent gemtext.
///
/// # Panics
///
/// Will panic if gemtext::render somehow produces invalid UTF-8.
/// Since gemtext::render only produces valid UTF-8, this should never happen.
pub fn convert(markdown_text: &str) -> String {
let parser = md::Parser::new_ext(markdown_text, md::Options::empty());
let mut state = State::new();
for event in parser {
match event {
md::Event::Start(md::Tag::Paragraph) => (),
md::Event::Start(md::Tag::Heading(level)) => state.start_heading(level),
md::Event::Start(md::Tag::BlockQuote) => state.start_block_quote(),
md::Event::Start(md::Tag::CodeBlock(_)) => state.start_code_block(),
md::Event::Start(md::Tag::List(_)) => (),
md::Event::Start(md::Tag::Item) => state.start_list_item(),
md::Event::Start(md::Tag::FootnoteDefinition(_)) => unimplemented!("footnotes disabled"),
md::Event::Start(md::Tag::Table(_)) => unimplemented!("tables disabled"),
md::Event::Start(md::Tag::TableHead) => unimplemented!("tables disabled"),
md::Event::Start(md::Tag::TableRow) => unimplemented!("tables disabled"),
md::Event::Start(md::Tag::TableCell) => unimplemented!("tables disabled"),
md::Event::Start(md::Tag::Emphasis) => state.toggle_emphasis(),
md::Event::Start(md::Tag::Strong) => state.toggle_strong(),
md::Event::Start(md::Tag::Strikethrough) => unimplemented!("strikethrough disabled"),
md::Event::Start(md::Tag::Link(_, _, _)) => state.start_link(),
md::Event::Start(md::Tag::Image(_, _, _)) => state.start_image(),
md::Event::End(md::Tag::Paragraph) => state.finish_node(),
md::Event::End(md::Tag::Heading(_)) => state.finish_node(),
md::Event::End(md::Tag::BlockQuote) => (),
md::Event::End(md::Tag::CodeBlock(_)) => state.finish_node(),
md::Event::End(md::Tag::List(_)) => state.finish_list(),
md::Event::End(md::Tag::Item) => state.finish_node(),
md::Event::End(md::Tag::FootnoteDefinition(_)) => unimplemented!("footnotes disabled"),
md::Event::End(md::Tag::Table(_)) => unimplemented!("tables disabled"),
md::Event::End(md::Tag::TableHead) => unimplemented!("tables disabled"),
md::Event::End(md::Tag::TableRow) => unimplemented!("tables disabled"),
md::Event::End(md::Tag::TableCell) => unimplemented!("tables disabled"),
md::Event::End(md::Tag::Emphasis) => state.toggle_emphasis(),
md::Event::End(md::Tag::Strong) => state.toggle_strong(),
md::Event::End(md::Tag::Strikethrough) => unimplemented!("strikethrough disabled"),
md::Event::End(md::Tag::Link(_, href, _)) => state.end_link(&href),
md::Event::End(md::Tag::Image(_, src, _)) => state.end_image(&src),
md::Event::Text(text) => state.add_text(&text),
md::Event::Code(code) => state.add_inline_code(&code),
md::Event::Html(html) => state.add_text(&html),
md::Event::FootnoteReference(_) => unimplemented!("footnotes disabled"),
md::Event::SoftBreak => state.add_text(" "),
md::Event::HardBreak => state.finish_node(),
md::Event::Rule => state.add_rule(),
md::Event::TaskListMarker(_) => unimplemented!("task lists disabled"),
}
}
let nodes = state.nodes
.into_iter()
.filter(|cluster| !cluster.is_empty())
.map(condense)
.collect::<Vec<_>>()
.join(&gemtext::Node::blank());
let mut result: Vec<u8> = vec![];
gemtext::render(nodes, &mut result).expect("gemtext::render somehow failed");
String::from_utf8(result).expect("gemtext::render somehow produced invalid UTF-8")
}
type NodeCluster = Vec<gemtext::Node>;
fn condense(original: NodeCluster) -> NodeCluster {
match original.as_slice() {
[gemtext::Node::Text(text), gemtext::Node::Link { name: Some(name), .. }] if text == name => vec![original[1].clone()],
_ => original,
}
}
enum NodeType {
Text,
Preformatted,
Heading { level: u8 },
ListItem,
Quote,
}
impl NodeType {
fn take(&mut self) -> Self {
std::mem::replace(self, NodeType::Text)
}
fn construct(self, body: String) -> gemtext::Node {
use NodeType::*;
match self {
Text => gemtext::Node::Text(body),
Preformatted => gemtext::Node::Preformatted(body),
Heading { level } => gemtext::Node::Heading { level, body },
ListItem => gemtext::Node::ListItem(body),
Quote => gemtext::Node::Quote(body),
}
}
}
struct State {
nodes: Vec<NodeCluster>,
pending_node_content: String,
pending_node_type: NodeType,
pending_other: Vec<gemtext::Node>,
link_text_stack: Vec<String>,
}
impl State {
fn new() -> Self {
State {
nodes: vec![],
pending_node_content: String::new(),
pending_node_type: NodeType::Text,
pending_other: vec![],
link_text_stack: vec![],
}
}
fn start_heading(&mut self, level: u32) {
let level = match level {
1 => 1,
2 => 2,
_ => 3,
};
self.pending_node_type = NodeType::Heading { level };
}
fn start_block_quote(&mut self) {
self.pending_node_type = NodeType::Quote;
}
fn start_code_block(&mut self) {
self.pending_node_type = NodeType::Preformatted;
}
fn start_list_item(&mut self) {
self.pending_node_type = NodeType::ListItem;
}
fn toggle_emphasis(&mut self) {
self.add_text("_");
}
fn toggle_strong(&mut self) {
self.add_text("**");
}
fn start_link(&mut self) {
self.link_text_stack.push(String::new());
}
fn start_image(&mut self) {
self.link_text_stack.push(String::new());
self.pending_node_content += "[image: ";
}
fn finish_list(&mut self) {
self.nodes.push(vec![]);
}
fn end_link(&mut self, href: &str) {
let text = self.link_text_stack.pop().unwrap_or_else(|| href.to_string());
self.pending_other.push(gemtext::Node::Link { to: href.to_string(), name: Some(text) });
}
fn end_image(&mut self, src: &str) {
let text = self.link_text_stack.pop().unwrap_or_else(|| src.to_string());
let text = format!("[image: {}]", text);
self.pending_other.push(gemtext::Node::Link { to: src.to_string(), name: Some(text) });
self.pending_node_content += "]";
}
// will create an empty paragraph if pending_text is empty
fn finish_node(&mut self) {
match (&self.pending_node_type, self.nodes.last().and_then(|cluster| cluster.last())) {
(NodeType::ListItem, Some(gemtext::Node::ListItem(_))) => (),
_ => self.nodes.push(vec![]),
}
let node_text = self.pending_node_content.trim().to_string();
let new_node = self.pending_node_type.take().construct(node_text);
let last_cluster = self.nodes.last_mut().expect("empty cluster list??");
last_cluster.push(new_node);
last_cluster.extend(self.pending_other.drain(..));
self.pending_node_content = String::new();
}
fn add_text(&mut self, text: &str) {
for link_text in &mut self.link_text_stack {
*link_text += text;
}
self.pending_node_content += text;
}
fn add_inline_code(&mut self, code: &str) {
self.pending_node_content += "`";
self.pending_node_content += code;
self.pending_node_content += "`";
}
fn add_rule(&mut self) {
self.add_text("-----");
self.finish_node();
}
}
#[cfg(test)]
#[test]
fn run_tests() {
let markdown_demo = r#"
# h1
## h2
### h3
---
```
sample
text
```
> implying
1. don't pick up the phone
2. don't let him in
3. don't be his friend
some `code` and some `` fancy`code `` and *italics*
and __bold__ and ***semi-overlapping* bold *and* italics**
this [paragraph](http://example.com) has [several links](http://example.org)
and an ![inline image](a://url) in it
![this one's just an image](https://placekitten.com/200/300)
"#;
let gemtext_demo = r#"# h1
## h2
### h3
-----
```
sample
text
```
> implying
* don't pick up the phone
* don't let him in
* don't be his friend
some `code` and some `fancy`code` and _italics_ and **bold** and **_semi-overlapping_ bold _and_ italics**
this paragraph has several links and an [image: inline image] in it
=> http://example.com paragraph
=> http://example.org several links
=> a://url [image: inline image]
=> https://placekitten.com/200/300 [image: this one's just an image]
"#;
assert_eq!(convert(markdown_demo), gemtext_demo);
}
#[cfg(test)]
#[test]
fn test_list_start() {
let markdown = "> hi\n\n1. uh\n2. ah\n";
let gemtext = "> hi\n\n* uh\n* ah\n";
assert_eq!(convert(markdown), gemtext);
}