Anki/rslib/src/text.rs

// Copyright: Ankitects Pty Ltd and contributors
// License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html

use lazy_static::lazy_static;
use regex::{Captures, Regex};
use std::borrow::Cow;
use std::ptr;
use unicase::eq as uni_eq;
use unicode_normalization::{
    char::is_combining_mark, is_nfc, is_nfkd_quick, IsNormalized, UnicodeNormalization,
};

#[derive(Debug, PartialEq)]
pub enum AVTag {
    SoundOrVideo(String),
    TextToSpeech {
        field_text: String,
        lang: String,
        voices: Vec<String>,
        speed: f32,
        other_args: Vec<String>,
    },
}

lazy_static! {
    static ref HTML: Regex = Regex::new(concat!(
        "(?si)",
        // wrapped text
        r"(<!--.*?-->)|(<style.*?>.*?</style>)|(<script.*?>.*?</script>)",
        // html tags
        r"|(<.*?>)",
    ))
    .unwrap();

    static ref HTML_MEDIA_TAGS: Regex = Regex::new(
        r#"(?xsi)
            # the start of the image, audio, or object tag
            <\b(?:img|audio|object)\b[^>]+\b(?:src|data)\b=
            (?:
                    # 1: double-quoted filename
                    "
                    ([^"]+?)
                    "
                    [^>]*>                    
                |
                    # 2: single-quoted filename
                    '
                    ([^']+?)
                    '
                    [^>]*>
                |
                    # 3: unquoted filename
                    ([^ >]+?)
                    (?:
                        # then either a space and the rest
                        \x20[^>]*>
                        |
                        # or the tag immediately ends
                        >
                    )
            )
            "#
    ).unwrap();

    // videos are also in sound tags
    static ref AV_TAGS: Regex = Regex::new(
        r#"(?xs)
            \[sound:(.+?)\]     # 1 - the filename in a sound tag
            |
            \[anki:tts\]
                \[(.*?)\]       # 2 - arguments to tts call
                (.*?)           # 3 - field text
            \[/anki:tts\]
            "#).unwrap();
}

pub fn strip_html(html: &str) -> Cow<str> {
    let mut out: Cow<str> = html.into();

    if let Cow::Owned(o) = strip_html_preserving_entities(html) {
        out = o.into();
    }

    if let Cow::Owned(o) = decode_entities(out.as_ref()) {
        out = o.into();
    }

    out
}

pub fn strip_html_preserving_entities(html: &str) -> Cow<str> {
    HTML.replace_all(html, "")
}

pub fn decode_entities(html: &str) -> Cow<str> {
    if html.contains('&') {
        match htmlescape::decode_html(html) {
            Ok(text) => text.replace('\u{a0}', " "),
            Err(e) => format!("{:?}", e),
        }
        .into()
    } else {
        // nothing to do
        html.into()
    }
}

pub fn strip_html_for_tts(html: &str) -> Cow<str> {
    match HTML.replace_all(html, " ") {
        Cow::Borrowed(_) => decode_entities(html),
        Cow::Owned(s) => decode_entities(&s).to_string().into(),
    }
}

pub fn strip_av_tags(text: &str) -> Cow<str> {
    AV_TAGS.replace_all(text, "")
}

/// Extract audio tags from string, replacing them with [anki:play] refs
pub fn extract_av_tags<'a>(text: &'a str, question_side: bool) -> (Cow<'a, str>, Vec<AVTag>) {
    let mut tags = vec![];
    let context = if question_side { 'q' } else { 'a' };
    let replaced_text = AV_TAGS.replace_all(text, |caps: &Captures| {
        // extract
        let tag = if let Some(av_file) = caps.get(1) {
            AVTag::SoundOrVideo(decode_entities(av_file.as_str()).into())
        } else {
            let args = caps.get(2).unwrap();
            let field_text = caps.get(3).unwrap();
            tts_tag_from_string(field_text.as_str(), args.as_str())
        };
        tags.push(tag);

        // and replace with reference
        format!("[anki:play:{}:{}]", context, tags.len() - 1)
    });

    (replaced_text, tags)
}

#[derive(Debug)]
pub(crate) struct MediaRef<'a> {
    pub full_ref: &'a str,
    pub fname: &'a str,
    /// audio files may have things like &amp; that need decoding
    pub fname_decoded: Cow<'a, str>,
}

pub(crate) fn extract_media_refs(text: &str) -> Vec<MediaRef> {
    let mut out = vec![];

    for caps in HTML_MEDIA_TAGS.captures_iter(text) {
        let fname = caps
            .get(1)
            .or_else(|| caps.get(2))
            .or_else(|| caps.get(3))
            .unwrap()
            .as_str();
        let fname_decoded = fname.into();
        out.push(MediaRef {
            full_ref: caps.get(0).unwrap().as_str(),
            fname,
            fname_decoded,
        });
    }

    for caps in AV_TAGS.captures_iter(text) {
        if let Some(m) = caps.get(1) {
            let fname = m.as_str();
            let fname_decoded = decode_entities(fname);
            out.push(MediaRef {
                full_ref: caps.get(0).unwrap().as_str(),
                fname,
                fname_decoded,
            });
        }
    }

    out
}

fn tts_tag_from_string<'a>(field_text: &'a str, args: &'a str) -> AVTag {
    let mut other_args = vec![];
    let mut split_args = args.split_ascii_whitespace();
    let lang = split_args.next().unwrap_or("");
    let mut voices = None;
    let mut speed = 1.0;

    for remaining_arg in split_args {
        if remaining_arg.starts_with("voices=") {
            voices = remaining_arg
                .split('=')
                .nth(1)
                .map(|voices| voices.split(',').map(ToOwned::to_owned).collect());
        } else if remaining_arg.starts_with("speed=") {
            speed = remaining_arg
                .split('=')
                .nth(1)
                .unwrap()
                .parse()
                .unwrap_or(1.0);
        } else {
            other_args.push(remaining_arg.to_owned());
        }
    }

    AVTag::TextToSpeech {
        field_text: strip_html_for_tts(field_text).into(),
        lang: lang.into(),
        voices: voices.unwrap_or_else(Vec::new),
        speed,
        other_args,
    }
}

pub fn strip_html_preserving_media_filenames(html: &str) -> Cow<str> {
    let without_fnames = HTML_MEDIA_TAGS.replace_all(html, r" ${1}${2}${3} ");
    let without_html = strip_html(&without_fnames);
    // no changes?
    if let Cow::Borrowed(b) = without_html {
        if ptr::eq(b, html) {
            return Cow::Borrowed(html);
        }
    }
    // make borrow checker happy
    without_html.into_owned().into()
}

#[allow(dead_code)]
pub(crate) fn sanitize_html(html: &str) -> String {
    ammonia::clean(html)
}

pub(crate) fn sanitize_html_no_images(html: &str) -> String {
    ammonia::Builder::default()
        .rm_tags(&["img"])
        .clean(html)
        .to_string()
}

pub(crate) fn normalize_to_nfc(s: &str) -> Cow<str> {
    if !is_nfc(s) {
        s.chars().nfc().collect::<String>().into()
    } else {
        s.into()
    }
}

pub(crate) fn ensure_string_in_nfc(s: &mut String) {
    if !is_nfc(s) {
        *s = s.chars().nfc().collect()
    }
}

/// Convert provided string to NFKD form and strip combining characters.
pub(crate) fn without_combining(s: &str) -> Cow<str> {
    // if the string is already normalized
    if matches!(is_nfkd_quick(s.chars()), IsNormalized::Yes) {
        // and no combining characters found, return unchanged
        if !s.chars().any(is_combining_mark) {
            return s.into();
        }
    }

    // we need to create a new string without the combining marks
    s.chars()
        .nfkd()
        .filter(|c| !is_combining_mark(*c))
        .collect::<String>()
        .into()
}

/// Check if string contains an unescaped wildcard.
pub(crate) fn is_glob(txt: &str) -> bool {
    // even number of \s followed by a wildcard
    lazy_static! {
        static ref RE: Regex = Regex::new(
            r#"(?x)
            (?:^|[^\\])     # not a backslash
            (?:\\\\)*       # even number of backslashes
            [*_]            # wildcard
            "#
        )
        .unwrap();
    }

    RE.is_match(txt)
}

/// Convert to a RegEx respecting Anki wildcards.
pub(crate) fn to_re(txt: &str) -> Cow<str> {
    to_custom_re(txt, ".")
}

/// Convert Anki style to RegEx using the provided wildcard.
pub(crate) fn to_custom_re<'a>(txt: &'a str, wildcard: &str) -> Cow<'a, str> {
    lazy_static! {
        static ref RE: Regex = Regex::new(r"\\?.").unwrap();
    }
    RE.replace_all(&txt, |caps: &Captures| {
        let s = &caps[0];
        match s {
            r"\\" | r"\*" => s.to_string(),
            r"\_" => "_".to_string(),
            "*" => format!("{}*", wildcard),
            "_" => wildcard.to_string(),
            s => regex::escape(s),
        }
    })
}

/// Convert to SQL respecting Anki wildcards.
pub(crate) fn to_sql(txt: &str) -> Cow<str> {
    // escape sequences and unescaped special characters which need conversion
    lazy_static! {
        static ref RE: Regex = Regex::new(r"\\[\\*]|[*%]").unwrap();
    }
    RE.replace_all(&txt, |caps: &Captures| {
        let s = &caps[0];
        match s {
            r"\\" => r"\\",
            r"\*" => "*",
            "*" => "%",
            "%" => r"\%",
            _ => unreachable!(),
        }
    })
}

/// Unescape everything.
pub(crate) fn to_text(txt: &str) -> Cow<str> {
    lazy_static! {
        static ref RE: Regex = Regex::new(r"\\(.)").unwrap();
    }
    RE.replace_all(&txt, "$1")
}

/// Escape Anki wildcards and the backslash for escaping them: \*_
pub(crate) fn escape_anki_wildcards(txt: &str) -> Cow<str> {
    lazy_static! {
        static ref RE: Regex = Regex::new(r"[\\*_]").unwrap();
    }
    RE.replace_all(&txt, r"\$0")
}

/// Compare text with a possible glob, folding case.
pub(crate) fn matches_glob(text: &str, search: &str) -> bool {
    if is_glob(search) {
        let search = format!("^(?i){}$", to_re(search));
        Regex::new(&search).unwrap().is_match(text)
    } else {
        uni_eq(text, &to_text(search))
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use std::borrow::Cow;

    #[test]
    fn stripping() {
        assert_eq!(strip_html("test"), "test");
        assert_eq!(strip_html("t<b>e</b>st"), "test");
        assert_eq!(strip_html("so<SCRIPT>t<b>e</b>st</script>me"), "some");

        assert_eq!(
            strip_html_preserving_media_filenames("<img src=foo.jpg>"),
            " foo.jpg "
        );
        assert_eq!(
            strip_html_preserving_media_filenames("<img src='foo.jpg'><html>"),
            " foo.jpg "
        );
        assert_eq!(strip_html_preserving_media_filenames("<html>"), "");
    }

    #[test]
    fn audio() {
        let s =
            "abc[sound:fo&amp;o.mp3]def[anki:tts][en_US voices=Bob,Jane speed=1.2]foo<br>1&gt;2[/anki:tts]gh";
        assert_eq!(strip_av_tags(s), "abcdefgh");

        let (text, tags) = extract_av_tags(s, true);
        assert_eq!(text, "abc[anki:play:q:0]def[anki:play:q:1]gh");

        assert_eq!(
            tags,
            vec![
                AVTag::SoundOrVideo("fo&o.mp3".into()),
                AVTag::TextToSpeech {
                    field_text: "foo 1>2".into(),
                    lang: "en_US".into(),
                    voices: vec!["Bob".into(), "Jane".into()],
                    other_args: vec![],
                    speed: 1.2
                },
            ]
        );
    }

    #[test]
    fn combining() {
        assert!(matches!(without_combining("test"), Cow::Borrowed(_)));
        assert!(matches!(without_combining("Über"), Cow::Owned(_)));
    }

    #[test]
    fn conversion() {
        assert_eq!(&to_re(r"[te\*st]"), r"\[te\*st\]");
        assert_eq!(&to_custom_re("f_o*", r"\d"), r"f\do\d*");
        assert_eq!(&to_sql("%f_o*"), r"\%f_o%");
        assert_eq!(&to_text(r"\*\_*_"), "*_*_");
        assert!(is_glob(r"\\\\_"));
        assert!(!is_glob(r"\\\_"));
        assert!(matches_glob("foo*bar123", r"foo\*bar*"));
    }
}