#
mdman/format/
man.rs

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    //! Man-page formatter.

    use crate::util::{header_text, parse_name_and_section};
    use crate::EventIter;
    use anyhow::{bail, Error};
    use pulldown_cmark::{Alignment, Event, HeadingLevel, LinkType, Tag, TagEnd};
    use std::fmt::Write;
    use url::Url;

    pub struct ManFormatter {
        url: Option<Url>,
    }

    impl ManFormatter {
        pub fn new(url: Option<Url>) -> ManFormatter {
            ManFormatter { url }
        }
    }

    impl super::Formatter for ManFormatter {
        fn render(&self, input: &str) -> Result<String, Error> {
            ManRenderer::render(input, self.url.clone())
        }

        fn render_options_start(&self) -> &'static str {
            // Tell pulldown_cmark to ignore this.
            // This will be stripped out later.
            "<![CDATA["
        }

        fn render_options_end(&self) -> &'static str {
            "]]>"
        }

        fn render_option(
            &self,
            params: &[&str],
            block: &str,
            _man_name: &str,
        ) -> Result<String, Error> {
            let rendered_options = params
                .iter()
                .map(|param| {
                    let r = self.render(param)?;
                    Ok(r.trim().trim_start_matches(".sp").to_string())
                })
                .collect::<Result<Vec<_>, Error>>()?;
            let rendered_block = self.render(block)?;
            let rendered_block = rendered_block.trim().trim_start_matches(".sp").trim();
            // .RS = move left margin to right 4.
            // .RE = move margin back one level.
            Ok(format!(
                "\n.sp\n{}\n.RS 4\n{}\n.RE\n",
                rendered_options.join(", "),
                rendered_block
            ))
        }

        fn linkify_man_to_md(&self, name: &str, section: u8) -> Result<String, Error> {
            Ok(format!("`{}`({})", name, section))
        }
    }

    #[derive(Copy, Clone)]
    enum Font {
        Bold,
        Italic,
    }

    impl Font {
        fn str_from_stack(font_stack: &[Font]) -> &'static str {
            let has_bold = font_stack.iter().any(|font| matches!(font, Font::Bold));
            let has_italic = font_stack.iter().any(|font| matches!(font, Font::Italic));
            match (has_bold, has_italic) {
                (false, false) => "\\fR", // roman (normal)
                (false, true) => "\\fI",  // italic
                (true, false) => "\\fB",  // bold
                (true, true) => "\\f(BI", // bold italic
            }
        }
    }

    struct ManRenderer<'e> {
        output: String,
        parser: EventIter<'e>,
        font_stack: Vec<Font>,
    }

    impl<'e> ManRenderer<'e> {
        fn render(input: &str, url: Option<Url>) -> Result<String, Error> {
            let parser = crate::md_parser(input, url);
            let output = String::with_capacity(input.len() * 3 / 2);
            let mut mr = ManRenderer {
                parser,
                output,
                font_stack: Vec::new(),
            };
            mr.push_man()?;
            Ok(mr.output)
        }

        fn push_man(&mut self) -> Result<(), Error> {
            // If this is true, this is inside a cdata block used for hiding
            // content from pulldown_cmark.
            let mut in_cdata = false;
            // The current list stack. None if unordered, Some if ordered with the
            // given number as the current index.
            let mut list: Vec<Option<u64>> = Vec::new();
            // Used in some cases where spacing isn't desired.
            let mut suppress_paragraph = false;
            let mut table_cell_index = 0;

            let mut last_seen_link_data = None;
            while let Some((event, range)) = self.parser.next() {
                let this_suppress_paragraph = suppress_paragraph;
                suppress_paragraph = false;
                match event {
                    Event::Start(tag) => {
                        match tag {
                            Tag::Paragraph => {
                                if !this_suppress_paragraph {
                                    self.flush();
                                    self.output.push_str(".sp\n");
                                }
                            }
                            Tag::Heading { level, .. } => {
                                if level == HeadingLevel::H1 {
                                    self.push_top_header()?;
                                } else if level == HeadingLevel::H2 {
                                    // Section header
                                    let text = header_text(&mut self.parser)?;
                                    self.flush();
                                    write!(self.output, ".SH \"{}\"\n", text)?;
                                    suppress_paragraph = true;
                                } else {
                                    // Subsection header
                                    let text = header_text(&mut self.parser)?;
                                    self.flush();
                                    write!(self.output, ".SS \"{}\"\n", text)?;
                                    suppress_paragraph = true;
                                }
                            }
                            Tag::BlockQuote(_kind) => {
                                self.flush();
                                // .RS = move left margin over 3
                                // .ll = shrink line length
                                self.output.push_str(".RS 3\n.ll -5\n.sp\n");
                                suppress_paragraph = true;
                            }
                            Tag::CodeBlock(_kind) => {
                                // space down, indent 4, no-fill mode
                                self.flush();
                                self.output.push_str(".sp\n.RS 4\n.nf\n");
                            }
                            Tag::List(start) => list.push(start),
                            Tag::Item => {
                                // Note: This uses explicit movement instead of .IP
                                // because the spacing on .IP looks weird to me.
                                // space down, indent 4
                                self.flush();
                                self.output.push_str(".sp\n.RS 4\n");
                                match list.last_mut().expect("item must have list start") {
                                    // Ordered list.
                                    Some(n) => {
                                        // move left 4, output the list index number, move right 1.
                                        write!(self.output, "\\h'-04' {}.\\h'+01'", n)?;
                                        *n += 1;
                                    }
                                    // Unordered list.
                                    None => self.output.push_str("\\h'-04'\\(bu\\h'+02'"),
                                }
                                suppress_paragraph = true;
                            }
                            Tag::FootnoteDefinition(_label) => unimplemented!(),
                            Tag::Table(alignment) => {
                                // Table start
                                // allbox = draw a box around all the cells
                                // tab(:) = Use `:` to separate cell data (instead of tab)
                                // ; = end of options
                                self.output.push_str(
                                    "\n.TS\n\
                                    allbox tab(:);\n",
                                );
                                let alignments: Vec<_> = alignment
                                    .iter()
                                    .map(|a| match a {
                                        Alignment::Left | Alignment::None => "lt",
                                        Alignment::Center => "ct",
                                        Alignment::Right => "rt",
                                    })
                                    .collect();
                                self.output.push_str(&alignments.join(" "));
                                self.output.push_str(".\n");
                                table_cell_index = 0;
                            }
                            Tag::TableHead => {
                                table_cell_index = 0;
                            }
                            Tag::TableRow => {
                                table_cell_index = 0;
                                self.output.push('\n');
                            }
                            Tag::TableCell => {
                                if table_cell_index != 0 {
                                    // Separator between columns.
                                    self.output.push(':');
                                }
                                // Start a text block.
                                self.output.push_str("T{\n");
                                table_cell_index += 1
                            }
                            Tag::Emphasis => self.push_font(Font::Italic),
                            Tag::Strong => self.push_font(Font::Bold),
                            // Strikethrough isn't usually supported for TTY.
                            Tag::Strikethrough => self.output.push_str("~~"),
                            Tag::Link {
                                link_type,
                                dest_url,
                                ..
                            } => {
                                last_seen_link_data = Some((link_type.clone(), dest_url.to_owned()));
                                if dest_url.starts_with('#') {
                                    // In a man page, page-relative anchors don't
                                    // have much meaning.
                                    continue;
                                }
                                match link_type {
                                    LinkType::Autolink | LinkType::Email => {
                                        // The text is a copy of the URL, which is not needed.
                                        match self.parser.next() {
                                            Some((Event::Text(_), _range)) => {}
                                            _ => bail!("expected text after autolink"),
                                        }
                                    }
                                    LinkType::Inline
                                    | LinkType::Reference
                                    | LinkType::Collapsed
                                    | LinkType::Shortcut => {
                                        self.push_font(Font::Italic);
                                    }
                                    // This is currently unused. This is only
                                    // emitted with a broken link callback, but I
                                    // felt it is too annoying to escape `[` in
                                    // option descriptions.
                                    LinkType::ReferenceUnknown
                                    | LinkType::CollapsedUnknown
                                    | LinkType::ShortcutUnknown => {
                                        bail!(
                                            "link with missing reference `{}` located at offset {}",
                                            dest_url,
                                            range.start
                                        );
                                    }
                                }
                            }
                            Tag::Image { .. } => {
                                bail!("images are not currently supported")
                            }
                            Tag::HtmlBlock { .. } | Tag::MetadataBlock { .. } => {}
                        }
                    }
                    Event::End(tag_end) => {
                        match &tag_end {
                            TagEnd::Paragraph => self.flush(),
                            TagEnd::Heading(..) => {}
                            TagEnd::BlockQuote => {
                                self.flush();
                                // restore left margin, restore line length
                                self.output.push_str(".br\n.RE\n.ll\n");
                            }
                            TagEnd::CodeBlock => {
                                self.flush();
                                // Restore fill mode, move margin back one level.
                                self.output.push_str(".fi\n.RE\n");
                            }
                            TagEnd::List(_) => {
                                list.pop();
                            }
                            TagEnd::Item => {
                                self.flush();
                                // Move margin back one level.
                                self.output.push_str(".RE\n");
                            }
                            TagEnd::FootnoteDefinition => {}
                            TagEnd::Table => {
                                // Table end
                                // I don't know why, but the .sp is needed to provide
                                // space with the following content.
                                self.output.push_str("\n.TE\n.sp\n");
                            }
                            TagEnd::TableHead => {}
                            TagEnd::TableRow => {}
                            TagEnd::TableCell => {
                                // End text block.
                                self.output.push_str("\nT}");
                            }
                            TagEnd::Emphasis | TagEnd::Strong => self.pop_font(),
                            TagEnd::Strikethrough => self.output.push_str("~~"),
                            TagEnd::Link => {
                                if let Some((link_type, ref dest_url)) = last_seen_link_data {
                                    if dest_url.starts_with('#') {
                                        continue;
                                    }
                                    match link_type {
                                        LinkType::Autolink | LinkType::Email => {}
                                        LinkType::Inline
                                        | LinkType::Reference
                                        | LinkType::Collapsed
                                        | LinkType::Shortcut => {
                                            self.pop_font();
                                            self.output.push(' ');
                                        }
                                        _ => {
                                            panic!("unexpected tag {:?}", tag_end);
                                        }
                                    }
                                    write!(self.output, "<{}>", escape(&dest_url)?)?;
                                }
                            }
                            TagEnd::Image | TagEnd::HtmlBlock | TagEnd::MetadataBlock(..) => {}
                        }
                    }
                    Event::Text(t) => {
                        self.output.push_str(&escape(&t)?);
                    }
                    Event::Code(t) => {
                        self.push_font(Font::Bold);
                        self.output.push_str(&escape(&t)?);
                        self.pop_font();
                    }
                    Event::Html(t) => {
                        if t.starts_with("<![CDATA[") {
                            // CDATA is a special marker used for handling options.
                            in_cdata = true;
                        } else if in_cdata {
                            if t.trim().ends_with("]]>") {
                                in_cdata = false;
                            } else if !t.trim().is_empty() {
                                self.output.push_str(&t);
                            }
                        } else {
                            self.output.push_str(&escape(&t)?);
                        }
                    }
                    Event::FootnoteReference(_t) => {}
                    Event::SoftBreak => self.output.push('\n'),
                    Event::HardBreak => {
                        self.flush();
                        self.output.push_str(".br\n");
                    }
                    Event::Rule => {
                        self.flush();
                        // \l' **length** '   Draw horizontal line (default underscore).
                        // \n(.lu  Gets value from register "lu" (current line length)
                        self.output.push_str("\\l'\\n(.lu'\n");
                    }
                    Event::TaskListMarker(_b) => unimplemented!(),
                    Event::InlineHtml(..) => unimplemented!(),
                    Event::InlineMath(..) => unimplemented!(),
                    Event::DisplayMath(..) => unimplemented!(),
                }
            }
            Ok(())
        }

        fn flush(&mut self) {
            if !self.output.ends_with('\n') {
                self.output.push('\n');
            }
        }

        /// Switch to the given font.
        ///
        /// Because the troff sequence `\fP` for switching to the "previous" font
        /// doesn't support nesting, this needs to emulate it here. This is needed
        /// for situations like **hi _there_**.
        fn push_font(&mut self, font: Font) {
            self.font_stack.push(font);
            self.output.push_str(Font::str_from_stack(&self.font_stack));
        }

        fn pop_font(&mut self) {
            self.font_stack.pop();
            self.output.push_str(Font::str_from_stack(&self.font_stack));
        }

        /// Parse and render the first top-level header of the document.
        fn push_top_header(&mut self) -> Result<(), Error> {
            // This enables the tbl preprocessor for tables.
            // This seems to be enabled by default on every modern system I could
            // find, but it doesn't seem to hurt to enable this.
            self.output.push_str("'\\\" t\n");
            // Extract the name of the man page.
            let text = header_text(&mut self.parser)?;
            let (name, section) = parse_name_and_section(&text)?;
            // .TH = Table header
            // .nh = disable hyphenation
            // .ad l = Left-adjust mode (disable justified).
            // .ss sets sentence_space_size to 0 (prevents double spaces after .
            //     if . is last on the line)
            write!(
                self.output,
                ".TH \"{}\" \"{}\"\n\
                .nh\n\
                .ad l\n\
                .ss \\n[.ss] 0\n",
                escape(&name.to_uppercase())?,
                section
            )?;
            Ok(())
        }
    }

    fn escape(s: &str) -> Result<String, Error> {
        // Note: Possible source on output escape sequences: https://man7.org/linux/man-pages/man7/groff_char.7.html.
        //       Otherwise, use generic escaping in the form `\[u1EE7]` or `\[u1F994]`.

        let mut replaced = s
            .replace('\\', "\\(rs")
            .replace('-', "\\-")
            .replace('\u{00A0}', "\\ ") // non-breaking space (non-stretchable)
            .replace('–', "\\[en]") // \u{2013} en-dash
            .replace('—', "\\[em]") // \u{2014} em-dash
            .replace('‘', "\\[oq]") // \u{2018} left single quote
            .replace('’', "\\[cq]") // \u{2019} right single quote or apostrophe
            .replace('“', "\\[lq]") // \u{201C} left double quote
            .replace('”', "\\[rq]") // \u{201D} right double quote
            .replace('…', "\\[u2026]") // \u{2026} ellipsis
            .replace('│', "|") // \u{2502} box drawing light vertical (could use \[br])
            .replace('├', "|") // \u{251C} box drawings light vertical and right
            .replace('└', "`") // \u{2514} box drawings light up and right
            .replace('─', "\\-") // \u{2500} box drawing light horizontal
        ;
        if replaced.starts_with('.') {
            replaced = format!("\\&.{}", &replaced[1..]);
        }

        if let Some(ch) = replaced.chars().find(|ch| {
            !matches!(ch, '\n' | ' ' | '!'..='/' | '0'..='9'
                | ':'..='@' | 'A'..='Z' | '['..='`' | 'a'..='z' | '{'..='~')
        }) {
            bail!(
                "character {:?} is not allowed (update the translation table if needed)",
                ch
            );
        }
        Ok(replaced)
    }