use comrak::nodes::{AstNode, NodeValue, NodeHtmlBlock}; use comrak::{Arena, parse_document, format_html, ComrakOptions}; use lazy_static::lazy_static; use std::env; use std::ffi::OsStr; use std::io::BufRead; use std::io::Read; use std::io; use std::path::Path; use syntect::dumps::from_binary; use syntect::easy::HighlightLines; use syntect::highlighting::ThemeSet; use syntect::parsing::{SyntaxSet, SyntaxReference}; use syntect::util::LinesWithEndings; use syntect::html::{ IncludeBackground, append_highlighted_html_for_styled_line, start_highlighted_html_snippet, }; lazy_static! { // Load syntaxes & themes lazily. Initialisation might not be // required in the case of Markdown rendering (if there's no code // blocks within the document). static ref SYNTAXES: SyntaxSet = from_binary(include_bytes!(env!("BAT_SYNTAXES"))); static ref THEMES: ThemeSet = ThemeSet::load_defaults(); // Configure Comrak's Markdown rendering with all the bells & // whistles! static ref MD_OPTS: ComrakOptions = ComrakOptions{ ext_strikethrough: true, ext_tagfilter: true, ext_table: true, ext_autolink: true, ext_tasklist: true, ext_header_ids: Some(String::new()), // yyeeesss! ext_footnotes: true, ext_description_lists: true, unsafe_: true, // required for tagfilter ..ComrakOptions::default() }; } // HTML fragment used when rendering inline blocks in Markdown documents. // Emulates the GitHub style (subtle background hue and padding). const BLOCK_PRE: &str = "
\n";

fn args_extension() -> Option {
    // The name of the file to be formatted is usually passed in as
    // the first argument and can be used to determine a syntax set.
    let args = env::args().collect::>();
    if args.len() != 2 {
        return None
    }

    Path::new(&args[1]).extension()
        .and_then(OsStr::to_str)
        .map(|s| s.to_string())
}

fn should_continue(res: &io::Result) -> bool {
    match *res {
        Ok(n) => n > 0,
        Err(_) => false,
    }
}

// This function is taken from the Comrak documentation.
fn iter_nodes<'a, F>(node: &'a AstNode<'a>, f: &F) where F : Fn(&'a AstNode<'a>) {
    f(node);
    for c in node.children() {
        iter_nodes(c, f);
    }
}

// Many of the syntaxes in the syntax list have random capitalisations, which
// means that name matching for the block info of a code block in HTML fails.
//
// Instead, try finding a syntax match by comparing case insensitively (for
// ASCII characters, anyways).
fn find_syntax_case_insensitive(info: &str) -> Option<&'static SyntaxReference> {
    SYNTAXES.syntaxes().iter().rev().find(|&s| info.eq_ignore_ascii_case(&s.name))
}

fn format_markdown() {
    let document = {
        let mut buffer = String::new();
        let stdin = io::stdin();
        let mut stdin = stdin.lock();
        stdin.read_to_string(&mut buffer).expect("failed to read stdin");
        buffer
    };

    let arena = Arena::new();
    let root = parse_document(&arena, &document, &MD_OPTS);

    // Syntax highlighting is implemented by traversing the arena and
    // replacing all code blocks with HTML blocks rendered by syntect.
    iter_nodes(root, &|node| {
        let mut ast = node.data.borrow_mut();
        match &ast.value {
            NodeValue::CodeBlock(code_block) => {
                let theme = &THEMES.themes["InspiredGitHub"];
                let info = String::from_utf8_lossy(&code_block.info);

                let syntax = find_syntax_case_insensitive(&info)
                    .or_else(|| SYNTAXES.find_syntax_by_extension(&info))
                    .unwrap_or_else(|| SYNTAXES.find_syntax_plain_text());

                let code = String::from_utf8_lossy(&code_block.literal);

                let rendered = {
                    // Write the block preamble manually to get exactly the
                    // desired layout:
                    let mut hl = HighlightLines::new(syntax, theme);
                    let mut buf = BLOCK_PRE.to_string();

                    for line in LinesWithEndings::from(&code) {
                        let regions = hl.highlight(line, &SYNTAXES);
                        append_highlighted_html_for_styled_line(
                            ®ions[..], IncludeBackground::No, &mut buf,
                        );
                    }

                    buf.push_str("
"); buf }; let block = NodeHtmlBlock { block_type: 1, // It's unclear what behaviour is toggled by this literal: rendered.into_bytes(), }; ast.value = NodeValue::HtmlBlock(block); }, _ => (), }; }); format_html(root, &MD_OPTS, &mut io::stdout()) .expect("Markdown rendering failed"); } fn format_code(extension: String) { let stdin = io::stdin(); let mut stdin = stdin.lock(); let mut linebuf = String::new(); // Get the first line, we might need it for syntax identification. let mut read_result = stdin.read_line(&mut linebuf); // Set up the highlighter let theme = &THEMES.themes["InspiredGitHub"]; let syntax = SYNTAXES.find_syntax_by_extension(&extension) .or_else(|| SYNTAXES.find_syntax_by_first_line(&linebuf)) .unwrap_or_else(|| SYNTAXES.find_syntax_plain_text()); let mut hl = HighlightLines::new(syntax, theme); let (mut outbuf, bg) = start_highlighted_html_snippet(theme); // Rather than using the `lines` iterator, read each line manually // and maintain buffer state. // // This is done because the syntax highlighter requires trailing // newlines to be efficient, and those are stripped in the lines // iterator. while should_continue(&read_result) { let regions = hl.highlight(&linebuf, &SYNTAXES); append_highlighted_html_for_styled_line( ®ions[..], IncludeBackground::IfDifferent(bg), &mut outbuf, ); // immediately output the current state to avoid keeping // things in memory print!("{}", outbuf); // merry go round again linebuf.clear(); outbuf.clear(); read_result = stdin.read_line(&mut linebuf); } println!(""); } fn main() { let extension = args_extension() .expect("cheddar should be invoked with a filename!"); if extension == "md" { format_markdown(); } else { format_code(extension); } }