readfeed 0.2.2

Feed parsing utilities
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

//! HTML reader to find feed URLs within the document.

use maybe_xml::{
    token::{
        self,
        prop::{Attributes, TagName},
    },
    Reader,
};

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Elem<'a> {
    FeedUrl(&'a str),
    BaseUrl(&'a str),
}

#[must_use]
fn is_link_tag_name(name: TagName<'_>) -> bool {
    name.as_str().eq_ignore_ascii_case("link")
}

fn eval_link_tag_attributes<'a>(attributes: Attributes<'a>) -> Option<&'a str> {
    let mut href: Option<&'a str> = None;
    let mut rel: Option<&'a str> = None;
    let mut ty: Option<&'a str> = None;

    for attr in attributes {
        let name = attr.name().as_str();

        if name.eq_ignore_ascii_case("href") {
            if let Some(val) = attr.value() {
                href = Some(val.as_str());
            }
        }

        if name.eq_ignore_ascii_case("rel") {
            if let Some(val) = attr.value() {
                rel = Some(val.as_str());
            }
        }

        if name.eq_ignore_ascii_case("type") {
            if let Some(val) = attr.value() {
                ty = Some(val.as_str());
            }
        }
    }

    let href = href?;

    let is_feed_link = rel
        .map(str::trim)
        .map(|rel| rel.eq_ignore_ascii_case("alternate") || rel.eq_ignore_ascii_case("feed"))
        .unwrap_or_default()
        || ty
            .map(str::trim)
            .map(|ty| {
                ty.eq_ignore_ascii_case("application/rss+xml")
                    || ty.eq_ignore_ascii_case("application/atom+xml")
            })
            .unwrap_or_default();
    is_feed_link.then_some(href)
}

#[must_use]
fn is_base_tag_name(name: TagName<'_>) -> bool {
    name.as_str().eq_ignore_ascii_case("base")
}

fn eval_base_tag_attributes(attributes: Attributes<'_>) -> Option<&str> {
    attributes.into_iter().find_map(|attr| {
        if attr.name().as_str().eq_ignore_ascii_case("href") {
            return attr.value().map(|val| val.as_str());
        }
        None
    })
}

#[derive(Debug)]
pub struct Iter<'a> {
    iter: maybe_xml::IntoIter<'a>,
}

impl<'a> Iter<'a> {
    #[inline]
    #[must_use]
    pub fn new(input: &'a str) -> Self {
        Self {
            iter: Reader::new(input).into_iter(),
        }
    }
}

impl<'a> Iterator for Iter<'a> {
    type Item = Elem<'a>;

    fn next(&mut self) -> Option<Self::Item> {
        eval(&mut self.iter)
    }
}

#[must_use]
fn eval<'a>(iter: &mut maybe_xml::IntoIter<'a>) -> Option<Elem<'a>> {
    loop {
        let token = iter.next()?;

        match token.ty() {
            token::Ty::StartTag(tag) => {
                let tag_name = tag.name();
                if is_link_tag_name(tag_name) {
                    if let Some(feed_url) = tag.attributes().and_then(eval_link_tag_attributes) {
                        return Some(Elem::FeedUrl(feed_url));
                    }
                }

                if is_base_tag_name(tag_name) {
                    if let Some(base_url) = tag.attributes().and_then(eval_base_tag_attributes) {
                        return Some(Elem::BaseUrl(base_url));
                    }
                }
            }
            token::Ty::EmptyElementTag(tag) => {
                let tag_name = tag.name();
                if is_link_tag_name(tag_name) {
                    if let Some(feed_url) = tag.attributes().and_then(eval_link_tag_attributes) {
                        return Some(Elem::FeedUrl(feed_url));
                    }
                }

                if is_base_tag_name(tag_name) {
                    if let Some(base_url) = tag.attributes().and_then(eval_base_tag_attributes) {
                        return Some(Elem::BaseUrl(base_url));
                    }
                }
            }
            token::Ty::EndTag(_)
            | token::Ty::Characters(_)
            | token::Ty::ProcessingInstruction(_)
            | token::Ty::Declaration(_)
            | token::Ty::Comment(_)
            | token::Ty::Cdata(_) => {
                // skip
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn eval_html_1() {
        let input: &str = include_str!("../tests/resources/html-1.html");
        let mut iter = Iter::new(input);

        assert_eq!(Some(Elem::FeedUrl("/feed.xml")), iter.next());
        // There are 2 "/feed.xml" links
        assert_eq!(Some(Elem::FeedUrl("/feed.xml")), iter.next());
        assert_eq!(None, iter.next());
    }
}