htmd 0.2.2

A turndown.js inspired HTML to Markdown converter.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171

mod anchor;
mod blockquote;
mod br;
mod code;
mod emphasis;
mod headings;
mod hr;
mod img;
mod li;
mod list;
mod table;

use crate::text_util::concat_strings;

use super::{options::Options, Element};
use anchor::AnchorElementHandler;
use blockquote::blockquote_handler;
use br::br_handler;
use code::code_handler;
use emphasis::emphasis_handler;
use headings::headings_handler;
use hr::hr_handler;
use html5ever::Attribute;
use img::img_handler;
use li::list_item_handler;
use list::list_handler;
use markup5ever_rcdom::Node;
use std::{collections::HashSet, rc::Rc};
use table::table_handler;

/// The DOM element handler.
pub trait ElementHandler: Send + Sync {
    fn append(&self) -> Option<String> {
        None
    }

    fn on_visit(
        &self,
        node: &Rc<Node>,
        tag: &str,
        attrs: &[Attribute],
        content: &str,
        options: &Options,
    ) -> Option<String>;
}

pub(crate) struct HandlerRule {
    tags: HashSet<String>,
    pub(crate) handler: Box<dyn ElementHandler>,
}

impl<F> ElementHandler for F
where
    F: (Fn(Element) -> Option<String>) + Send + Sync,
{
    fn on_visit(
        &self,
        node: &Rc<Node>,
        tag: &str,
        attrs: &[Attribute],
        content: &str,
        options: &Options,
    ) -> Option<String> {
        self(Element {
            node,
            tag,
            attrs,
            content,
            options,
        })
    }
}

/// Builtin element handlers
pub(crate) struct ElementHandlers {
    pub(crate) rules: Vec<HandlerRule>,
}

impl ElementHandlers {
    pub fn new() -> Self {
        let mut handlers = Self { rules: Vec::new() };

        // img
        handlers.add_handler(vec!["img"], img_handler);

        // a
        handlers.add_handler(vec!["a"], AnchorElementHandler::new());

        // list
        handlers.add_handler(vec!["ol", "ul"], list_handler);

        // li
        handlers.add_handler(vec!["li"], list_item_handler);

        // quote
        handlers.add_handler(vec!["blockquote"], blockquote_handler);

        // code
        handlers.add_handler(vec!["code"], code_handler);

        // strong
        handlers.add_handler(vec!["strong", "b"], bold_handler);

        // italic
        handlers.add_handler(vec!["i", "em"], italic_handler);

        // headings
        handlers.add_handler(vec!["h1", "h2", "h3", "h4", "h5", "h6"], headings_handler);

        // br
        handlers.add_handler(vec!["br"], br_handler);

        // hr
        handlers.add_handler(vec!["hr"], hr_handler);

        // table
        handlers.add_handler(vec!["table"], table_handler);

        // other block elements
        handlers.add_handler(
            vec![
                "p", "pre", "body", "div", "tr", "td", "th", "thead", "tbody", "tfoot", "header",
                "footer", "nav", "section", "article", "aside", "main", "head", "script", "style",
                "caption",
            ],
            block_handler,
        );

        handlers
    }

    pub fn add_handler<Handler>(&mut self, tags: Vec<&str>, handler: Handler)
    where
        Handler: ElementHandler + 'static,
    {
        assert!(!tags.is_empty(), "tags cannot be empty.");
        let handler = HandlerRule {
            tags: HashSet::from_iter(tags.iter().map(|tag| tag.to_string())),
            handler: Box::new(handler),
        };
        self.rules.push(handler);
    }
}

impl ElementHandler for ElementHandlers {
    fn on_visit(
        &self,
        node: &Rc<Node>,
        tag: &str,
        attrs: &[Attribute],
        content: &str,
        options: &Options,
    ) -> Option<String> {
        match self.rules.iter().rev().find(|rule| rule.tags.contains(tag)) {
            Some(rule) => rule.handler.on_visit(node, tag, attrs, content, options),
            None => Some(content.to_string()),
        }
    }
}

fn block_handler(element: Element) -> Option<String> {
    Some(concat_strings!("\n\n", element.content, "\n\n"))
}

fn bold_handler(element: Element) -> Option<String> {
    emphasis_handler(element, "**")
}

fn italic_handler(element: Element) -> Option<String> {
    emphasis_handler(element, "_")
}