markdown_it/plugins/cmark/block/
heading.rs

1//! ATX heading
2//!
3//! `# h1`, `## h2`, etc.
4//!
5//! <https://spec.commonmark.org/0.30/#atx-heading>
6use crate::parser::block::{BlockRule, BlockState};
7use crate::parser::inline::InlineRoot;
8use crate::{MarkdownIt, Node, NodeValue, Renderer};
9
10#[derive(Debug)]
11pub struct ATXHeading {
12    pub level: u8,
13}
14
15impl NodeValue for ATXHeading {
16    fn render(&self, node: &Node, fmt: &mut dyn Renderer) {
17        static TAG : [&str; 6] = [ "h1", "h2", "h3", "h4", "h5", "h6" ];
18        debug_assert!(self.level >= 1 && self.level <= 6);
19
20        fmt.cr();
21        fmt.open(TAG[self.level as usize - 1], &node.attrs);
22        fmt.contents(&node.children);
23        fmt.close(TAG[self.level as usize - 1]);
24        fmt.cr();
25    }
26}
27
28pub fn add(md: &mut MarkdownIt) {
29    md.block.add_rule::<HeadingScanner>();
30}
31
32#[doc(hidden)]
33pub struct HeadingScanner;
34impl BlockRule for HeadingScanner {
35    fn run(state: &mut BlockState) -> Option<(Node, usize)> {
36
37        if state.line_indent(state.line) >= state.md.max_indent { return None; }
38
39        let line = state.get_line(state.line);
40        let Some('#') = line.chars().next() else { return None; };
41
42        let text_pos;
43
44        // count heading level
45        let mut level = 0u8;
46        let mut chars = line.char_indices();
47        loop {
48            match chars.next() {
49                Some((_, '#')) => {
50                    level += 1;
51                    if level > 6 { return None; }
52                }
53                Some((x, ' ' | '\t')) => {
54                    text_pos = x;
55                    break;
56                }
57                None => {
58                    text_pos = level as usize;
59                    break;
60                }
61                Some(_) => return None,
62            }
63        }
64
65        // Let's cut tails like '    ###  ' from the end of string
66
67        let mut chars_back = chars.rev().peekable();
68        while let Some((_, ' ' | '\t')) = chars_back.peek() { chars_back.next(); }
69        while let Some((_, '#'))        = chars_back.peek() { chars_back.next(); }
70
71        let text_max = match chars_back.next() {
72            // ## foo ##
73            Some((last_pos, ' ' | '\t')) => last_pos + 1,
74            // ## foo##
75            Some(_) => line.len(),
76            // ## ## (already consumed the space)
77            None => text_pos,
78        };
79
80        let content = line[text_pos..text_max].to_owned();
81        let mapping = vec![(0, state.line_offsets[state.line].first_nonspace + text_pos)];
82
83        let mut node = Node::new(ATXHeading { level });
84        node.children.push(Node::new(InlineRoot::new(content, mapping)));
85        Some((node, 1))
86    }
87}
markdown_it/plugins/cmark/block/heading.rs

markdown_it/plugins/cmark/block/
heading.rs
