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| mod entity;
fn decode_named_entity(entity: &str) -> Option<char> {
entity::ENTITIES
.binary_search_by_key(&entity, |t| t.0)
.map(|idx| entity::ENTITIES[idx].1)
.ok()
}
fn parse_html_entity(ent_name: &str) -> Option<char> {
let d = decode_named_entity(ent_name);
if d.is_some() {
return d;
}
let num = ent_name.strip_prefix("#")?;
if num.chars().next()? == 'x' {
u32::from_str_radix(&num[1..].to_lowercase(), 16)
} else {
// remaining string may be empty, but that will generate an Err(Empty)
u32::from_str_radix(num, 10)
}
.ok()
.filter(|n| !matches!(n, 9 | 10 | 13 | 32))
.and_then(|n| char::from_u32(n))
}
fn html_entitities_to_text(s: &str) -> String {
let mut out = String::new();
// except for the first part, every part will have started with an ampersand
// thus the start of the remaining parts is a HTML entity
let mut parts = s.split('&');
/*
skip first part. if the string started with an ampersand, the first part
will be an empty string
if the string was empty, the first part will also be an empty string so its
safe to unwrap
*/
out.push_str(parts.next().unwrap());
for part in parts {
let end = part
// entity can be terminated by semicolon or whitespace
.find(|c: char| c.is_whitespace() || c == ';')
// entity can also terminated by end of string or start of
// another entity
.unwrap_or_else(|| part.len());
if let Some(entity) = parse_html_entity(&part[..end]) {
out.push(entity);
// get byte length of the char we did `find` above
let real_end = if let Some(next) = &part[end..].chars().next() {
end + next.len_utf8()
} else {
// invalid html entity that doesn't end with `;`
end
};
out.push_str(&part[real_end..]);
} else {
out.push('&');
out.push_str(part);
}
}
out
}
/// Function to parse and handle the individual tags.
/// Assumes that there was a '<' before the given string
///
/// Returns the generated text and the byte length to skip.
fn handle_tag(s: &str) -> (String, usize) {
let (tag, more) = match s.split_once('>') {
Some((tag, more)) if !tag.is_empty() => (tag, more),
_ => {
// was not actually a tag, so reinsert the '<'
return (String::from("<"), 0);
}
};
let (name, attribs) = if let Some((name, attribs)) = tag.split_once(char::is_whitespace) {
(name, Some(attribs))
} else {
(tag, None)
};
match name.to_lowercase().as_str() {
"a" => {
let href = attribs
.and_then(|attribs| {
Some(
attribs
// check for the href and then discard everything before it
.split_once("href")?
.1
// there might be whitespace between 'href' and '='
.trim_start()
// check for and then discard the equal sign
.strip_prefix('=')?
// remove whitespace after the equal sign
.trim_start(),
)
})
.and_then(|href_value|
// find quoted string
match href_value.chars().next()? {
start @ '\'' | start @ '"' => {
let (end, _) = href_value
.char_indices()
.skip(1)
.find(|(_, c)| *c == start)?;
Some(href_value[1..end].to_string())
}
_ => None,
})
.filter(|href| !href.starts_with("javascript:"))
.map(|href| html_entitities_to_text(&href));
// only use to_ascii_lowercase here so the byte offsets dont get
// messed up from one uppercase symbol becoming two lowercase
// symbols or something like that
let more = more.to_ascii_lowercase();
let end_without_closing = more.find("</a");
let content = end_without_closing.map(|i| more[0..i].trim());
let end = end_without_closing
.map(|i| i + 3)
.and_then(|end_tag| more[end_tag..].find('>').map(|i| end_tag + i + 1))
.unwrap_or_else(|| more.len());
let link = match (content, href) {
(Some(content_value), Some(href_value)) => {
if content_value == href_value {
href_value
} else {
let cleaned_content_value = html2text(content_value);
format!("{} ({})", cleaned_content_value, href_value)
}
}
(None, Some(href_value)) => href_value,
(Some(content_value), None) => content_value.to_string(),
(None, None) => "".to_string(),
};
(link, tag.len() + 1 + end)
}
"br" | "br/" | "li" | "/ol" | "/ul" => (String::from("\r\n"), tag.len() + 1),
"p" | "h1" | "h2" | "h3" | "h4" | "h5" | "h6" | "/h1" | "/h2" | "/h3" | "/h4" | "/h5"
| "/h6" => (String::from("\r\n\r\n"), tag.len() + 1),
name @ "head" | name @ "script" | name @ "style" => {
// silence tags
// only use to_ascii_lowercase here so the byte offsets dont get
// messed up from one uppercase symbol becoming two lowercase
// symbols or something like that
let more = more.to_ascii_lowercase();
let end = more
.find(&format!("</{}", name))
.map(|i| i + 2 + name.len())
.and_then(|end_tag| more[end_tag..].find('>').map(|i| i + end_tag + 1))
.unwrap_or_else(|| more.len());
(String::new(), tag.len() + 1 + end)
}
"!--" => {
// HTML comment
(String::new(), s.find("-->").map_or(s.len(), |n| n + 3))
}
// other/unknown tags are just discarded
_ => (String::new(), tag.len() + 1),
}
}
/// Convert some HTML to plain text. Only some simple HTML tags are handled:
/// - `a` tags are transformed to their href attribute value
/// - paragraph, linebreak, heading, list, and list item tags insert different
/// amounts of line breaks.
/// - HTML comments as well as `head`, `script` and `style` are completely
/// discarded, including their content
/// - unknown tags are skipped, but their content is printed
///
/// HTML named entities will be replaced with the respecive Unicode code point,
/// and whitespace will be collapsed as is usual in HTML.
///
/// The resulting string will have CRLF line endings.
pub fn html2text(html: &str) -> String {
// collapse spaces
let html = html.split_whitespace().collect::<Vec<_>>().join(" ");
let mut out = String::new();
let mut i = 0;
while i < html.len() {
match html[i..].find('<') {
None => {
// no more tags in the input, done
out += &html_entitities_to_text(&html[i..]);
break;
}
Some(text_segment) => {
if text_segment > 0 {
out += &html_entitities_to_text(&html[i..i + text_segment]);
i += text_segment;
}
i += 1; // skip the '<'
let (s, advance) = handle_tag(&html[i..]);
if !s.is_empty() {
if out.ends_with("\r\n\r\n") || out.is_empty() {
out += &s.trim_start();
} else {
out += &s;
}
}
i += advance;
}
}
}
out
}
#[cfg(test)]
mod tests {
use super::*;
macro_rules! test {
($name:ident, $from:literal, $to:literal $(,)?) => {
#[test]
fn $name() {
assert_eq!(&html2text($from), $to);
}
};
($($name:ident: $from:literal to $to:literal,)* $(,)?) => {
$(test!{$name, $from, $to})*
};
}
test! {
plaintext: "blah" to "blah",
tag: "<div></div>" to "",
tag_contents: "<div>simple text</div>" to "simple text",
// links
link:
"click <a href=\"test\">here</a>"
to "click here (test)",
link_href_equal_to_content:
"click <a href=\"test\">test</a>"
to "click test",
links_ignore_attributes:
"click <a class=\"x\" href=\"test\">here</a>"
to "click here (test)",
link_entities_in_url:
"click <a href=\"ents/'x'\">here</a>"
to "click here (ents/'x')",
link_javascript:
"click <a href=\"javascript:void(0)\">here</a>"
to "click here",
link_ignore_content_tags:
"click <a href=\"test\"><span>here</span> or here</a>"
to "click here or here (test)",
link_absolute_url:
"click <a href=\"http://bit.ly/2n4wXRs\">news</a>"
to "click news (http://bit.ly/2n4wXRs)",
link_ignore_attributes_2:
"<a rel=\"mw:WikiLink\" href=\"/wiki/yet#English\" title=\"yet\">yet</a>, <a rel=\"mw:WikiLink\" href=\"/wiki/not_yet#English\" title=\"not yet\">not yet</a>"
to "yet (/wiki/yet#English), not yet (/wiki/not_yet#English)",
// inlines
ignore_inline:
"strong <strong>text</strong>"
to "strong text",
ignore_inline_attributes:
"some <div id=\"a\" class=\"b\">div</div>"
to "some div",
// lines breaks and spaces
collapse_spaces:
"should ignore more spaces" to "should ignore more spaces",
collapse_linebreaks:
"a\nb\nc" to "a b c",
collapse_mixed:
"should \nignore \r\nnew lines" to "should ignore new lines",
br_tag:
"two<br>line<br/>breaks" to "two\r\nline\r\nbreaks",
paragraph:
"<p>two</p><p>paragraphs</p>" to "two\r\n\r\nparagraphs",
// Headers
h1:
"<h1>First</h1>main text" to "First\r\n\r\nmain text",
h2_inline:
"First<h2>Second</h2>next section"
to "First\r\n\r\nSecond\r\n\r\nnext section",
h2:
"<h2>Second</h2>next section" to "Second\r\n\r\nnext section",
h3_inline:
"Second<h3>Third</h3>next section"
to "Second\r\n\r\nThird\r\n\r\nnext section",
h3:
"<h3>Third</h3>next section" to "Third\r\n\r\nnext section",
h4_inline:
"Third<h4>Fourth</h4>next section"
to "Third\r\n\r\nFourth\r\n\r\nnext section",
h4:
"<h4>Fourth</h4>next section" to "Fourth\r\n\r\nnext section",
h5_inline:
"Fourth<h5>Fifth</h5>next section"
to "Fourth\r\n\r\nFifth\r\n\r\nnext section",
h5:
"<h5>Fifth</h5>next section" to "Fifth\r\n\r\nnext section",
h6_inline:
"Fifth<h6>Sixth</h6>next section"
to "Fifth\r\n\r\nSixth\r\n\r\nnext section",
h6:
"<h6>Sixth</h6>next section" to "Sixth\r\n\r\nnext section",
no_h7:
"<h7>Not Header</h7>next section" to "Not Headernext section",
// html entitites
entity_nbsp:
"two spaces" to "two spaces",
entity_copy:
"© 2017 K3A" to "© 2017 K3A",
entity_tag:
"<printtag>" to "<printtag>",
entity_currencies:
"would you pay in ¢, £, ¥ or €?"
to "would you pay in ¢, £, ¥ or €?",
ampersand_not_entity:
"Tom & Jerry is not an entity" to "Tom & Jerry is not an entity",
entity_unknown:
"this &neither; as you see" to "this &neither; as you see",
entity_amp:
"fish & chips" to "fish & chips",
unordered_list:
"list of items<ul><li>One</li><li>Two</li><li>Three</li></ul>"
to "list of items\r\nOne\r\nTwo\r\nThree\r\n",
entity_quot:
""I'm sorry, Dave. I'm afraid I can't do that." – HAL, 2001: A Space Odyssey"
to "\"I'm sorry, Dave. I'm afraid I can't do that.\" – HAL, 2001: A Space Odyssey",
entity_reg:
"Google ®" to "Google ®",
// Large entity
entity_large_unknown:
"&abcdefghij;" to "&abcdefghij;",
// Numeric HTML entities
entity_numeric:
"⁌ decimal and hex entities supported ⁍"
to "⁌ decimal and hex entities supported ⁍",
entity_numeric_2:
"'single quotes' and 츝"
to "'single quotes' and 츝",
// full thml structure
empty: "" to "",
full_html:
"<html><head><title>Good</title></head><body>x</body>" to "x",
ignore_script:
"we are not <script type=\"javascript\"></script>interested in scripts"
to "we are not interested in scripts",
// custom html tags
ignore_unknown_tag:
"<aa>hello</aa>" to "hello",
ignore_unknown_tag_whitespace:
"<aa >hello</aa>" to "hello",
ignore_unknown_tag_attributes:
"<aa x=\"1\">hello</aa>" to "hello",
invalid_html_entity_without_semicolon: "&hellip" to "…",
}
}
|