Move dc_dehtml to dehtml and remove unnecessary is_empty check

src/dehtml.rs

@@ -0,0 +1,192 @@
+//! De-HTML
+//!
+//! A module to remove HTML tags from the email text
+
+use lazy_static::lazy_static;
+use quick_xml;
+use quick_xml::events::{BytesEnd, BytesStart, BytesText};
+
+lazy_static! {
+    static ref LINE_RE: regex::Regex = regex::Regex::new(r"(\r?\n)+").unwrap();
+}
+
+struct Dehtml {
+    strbuilder: String,
+    add_text: AddText,
+    last_href: Option<String>,
+}
+
+#[derive(Debug, PartialEq)]
+enum AddText {
+    No,
+    YesRemoveLineEnds,
+    YesPreserveLineEnds,
+}
+
+// dehtml() returns way too many newlines; however, an optimisation on this issue is not needed as
+// the newlines are typically removed in further processing by the caller
+pub fn dehtml(buf: &str) -> String {
+    let buf = buf.trim();
+
+    let mut dehtml = Dehtml {
+        strbuilder: String::with_capacity(buf.len()),
+        add_text: AddText::YesRemoveLineEnds,
+        last_href: None,
+    };
+
+    let mut reader = quick_xml::Reader::from_str(buf);
+
+    let mut buf = Vec::new();
+
+    loop {
+        match reader.read_event(&mut buf) {
+            Ok(quick_xml::events::Event::Start(ref e)) => {
+                dehtml_starttag_cb(e, &mut dehtml, &reader)
+            }
+            Ok(quick_xml::events::Event::End(ref e)) => dehtml_endtag_cb(e, &mut dehtml),
+            Ok(quick_xml::events::Event::Text(ref e)) => dehtml_text_cb(e, &mut dehtml),
+            Ok(quick_xml::events::Event::CData(ref e)) => dehtml_cdata_cb(e, &mut dehtml),
+            Err(e) => {
+                eprintln!(
+                    "Parse html error: Error at position {}: {:?}",
+                    reader.buffer_position(),
+                    e
+                );
+            }
+            Ok(quick_xml::events::Event::Eof) => break,
+            _ => (),
+        }
+        buf.clear();
+    }
+
+    dehtml.strbuilder
+}
+
+fn dehtml_text_cb(event: &BytesText, dehtml: &mut Dehtml) {
+    if dehtml.add_text == AddText::YesPreserveLineEnds
+        || dehtml.add_text == AddText::YesRemoveLineEnds
+    {
+        let last_added = escaper::decode_html_buf_sloppy(event.escaped()).unwrap_or_default();
+
+        if dehtml.add_text == AddText::YesRemoveLineEnds {
+            dehtml.strbuilder += LINE_RE.replace_all(&last_added, "\r").as_ref();
+        } else {
+            dehtml.strbuilder += &last_added;
+        }
+    }
+}
+
+fn dehtml_cdata_cb(event: &BytesText, dehtml: &mut Dehtml) {
+    if dehtml.add_text == AddText::YesPreserveLineEnds
+        || dehtml.add_text == AddText::YesRemoveLineEnds
+    {
+        let last_added = escaper::decode_html_buf_sloppy(event.escaped()).unwrap_or_default();
+
+        if dehtml.add_text == AddText::YesRemoveLineEnds {
+            dehtml.strbuilder += LINE_RE.replace_all(&last_added, "\r").as_ref();
+        } else {
+            dehtml.strbuilder += &last_added;
+        }
+    }
+}
+
+fn dehtml_endtag_cb(event: &BytesEnd, dehtml: &mut Dehtml) {
+    let tag = String::from_utf8_lossy(event.name()).trim().to_lowercase();
+
+    match tag.as_str() {
+        "p" | "div" | "table" | "td" | "style" | "script" | "title" | "pre" => {
+            dehtml.strbuilder += "\n\n";
+            dehtml.add_text = AddText::YesRemoveLineEnds;
+        }
+        "a" => {
+            if let Some(ref last_href) = dehtml.last_href.take() {
+                dehtml.strbuilder += "](";
+                dehtml.strbuilder += last_href;
+                dehtml.strbuilder += ")";
+            }
+        }
+        "b" | "strong" => {
+            dehtml.strbuilder += "*";
+        }
+        "i" | "em" => {
+            dehtml.strbuilder += "_";
+        }
+        _ => {}
+    }
+}
+
+fn dehtml_starttag_cb<B: std::io::BufRead>(
+    event: &BytesStart,
+    dehtml: &mut Dehtml,
+    reader: &quick_xml::Reader<B>,
+) {
+    let tag = String::from_utf8_lossy(event.name()).trim().to_lowercase();
+
+    match tag.as_str() {
+        "p" | "div" | "table" | "td" => {
+            dehtml.strbuilder += "\n\n";
+            dehtml.add_text = AddText::YesRemoveLineEnds;
+        }
+        "br" => {
+            dehtml.strbuilder += "\n";
+            dehtml.add_text = AddText::YesRemoveLineEnds;
+        }
+        "style" | "script" | "title" => {
+            dehtml.add_text = AddText::No;
+        }
+        "pre" => {
+            dehtml.strbuilder += "\n\n";
+            dehtml.add_text = AddText::YesPreserveLineEnds;
+        }
+        "a" => {
+            if let Some(href) = event.html_attributes().find(|attr| {
+                attr.as_ref()
+                    .map(|a| String::from_utf8_lossy(a.key).trim().to_lowercase() == "href")
+                    .unwrap_or_default()
+            }) {
+                let href = href
+                    .unwrap()
+                    .unescape_and_decode_value(reader)
+                    .unwrap_or_default()
+                    .to_lowercase();
+
+                if !href.is_empty() {
+                    dehtml.last_href = Some(href);
+                    dehtml.strbuilder += "[";
+                }
+            }
+        }
+        "b" | "strong" => {
+            dehtml.strbuilder += "*";
+        }
+        "i" | "em" => {
+            dehtml.strbuilder += "_";
+        }
+        _ => {}
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_dehtml() {
+        let cases = vec![
+            (
+                "<a href='https://example.com'> Foo </a>",
+                "[ Foo ](https://example.com)",
+            ),
+            ("<img href='/foo.png'>", ""),
+            ("<b> bar </b>", "* bar *"),
+            ("<b> bar <i> foo", "* bar _ foo"),
+            ("&amp; bar", "& bar"),
+            // Note missing '
+            ("<a href='/foo.png>Hi</a> ", ""),
+            ("", ""),
+        ];
+        for (input, output) in cases {
+            assert_eq!(dehtml(input), output);
+        }
+    }
+}