mdBook/src/renderer/html_handlebars/hbs_renderer.rs

use renderer::html_handlebars::helpers;
use renderer::Renderer;
use book::MDBook;
use book::bookitem::BookItem;
use {utils, theme};
use regex::{Regex, Captures};

use std::ascii::AsciiExt;
use std::path::{Path, PathBuf};
use std::fs::{self, File};
use std::error::Error;
use std::io::{self, Read};
use std::collections::BTreeMap;
use std::collections::HashMap;

use handlebars::Handlebars;

use serde_json;


#[derive(Default)]
pub struct HtmlHandlebars;

impl HtmlHandlebars {
    pub fn new() -> Self {
        HtmlHandlebars
    }
}

impl Renderer for HtmlHandlebars {
    fn render(&self, book: &MDBook) -> Result<(), Box<Error>> {
        debug!("[fn]: render");
        let mut handlebars = Handlebars::new();

        // Load theme
        let theme = theme::Theme::new(book.get_theme_path());

        // Register template
        debug!("[*]: Register handlebars template");
        handlebars
            .register_template_string("index", String::from_utf8(theme.index)?)?;

        // Register helpers
        debug!("[*]: Register handlebars helpers");
        handlebars.register_helper("toc", Box::new(helpers::toc::RenderToc));
        handlebars.register_helper("previous", Box::new(helpers::navigation::previous));
        handlebars.register_helper("next", Box::new(helpers::navigation::next));

        let mut data = make_data(book)?;

        // Print version
        let mut print_content: String = String::new();

        // Check if dest directory exists
        debug!("[*]: Check if destination directory exists");
        if fs::create_dir_all(book.get_dest()).is_err() {
            return Err(Box::new(io::Error::new(io::ErrorKind::Other,
                                               "Unexpected error when constructing destination path")));
        }

        // Render a file for every entry in the book
        let mut index = true;
        for item in book.iter() {

            match *item {
                BookItem::Chapter(_, ref ch) |
                BookItem::Affix(ref ch) => {
                    if ch.path != PathBuf::new() {

                        let path = book.get_src().join(&ch.path);

                        debug!("[*]: Opening file: {:?}", path);
                        let mut f = File::open(&path)?;
                        let mut content: String = String::new();

                        debug!("[*]: Reading file");
                        f.read_to_string(&mut content)?;

                        // Parse for playpen links
                        if let Some(p) = path.parent() {
                            content = helpers::playpen::render_playpen(&content, p);
                        }

                        // Render markdown using the pulldown-cmark crate
                        content = utils::render_markdown(&content);
                        print_content.push_str(&content);

                        // Update the context with data for this file
                        let path =
                            ch.path
                                .to_str()
                                .ok_or_else(|| io::Error::new(io::ErrorKind::Other, "Could not convert path to str"))?;
                        data.insert("path".to_owned(), json!(path));
                        data.insert("content".to_owned(), json!(content));
                        data.insert("chapter_title".to_owned(), json!(ch.name));
                        data.insert("path_to_root".to_owned(), json!(utils::fs::path_to_root(&ch.path)));

                        // Render the handlebars template with the data
                        debug!("[*]: Render template");
                        let rendered = handlebars.render("index", &data)?;

                        let filename = Path::new(&ch.path).with_extension("html");

                        // Do several kinds of post-processing
                        let rendered = build_header_links(rendered, filename.to_str().unwrap_or(""));
                        let rendered = fix_anchor_links(rendered, filename.to_str().unwrap_or(""));
                        let rendered = fix_code_blocks(rendered);
                        let rendered = add_playpen_pre(rendered);

                        // Write to file
                        info!("[*] Creating {:?} ✓", filename.display());
                        book.write_file(filename, &rendered.into_bytes())?;

                        // Create an index.html from the first element in SUMMARY.md
                        if index {
                            debug!("[*]: index.html");

                            let mut content = String::new();
                            let _source = File::open(book.get_dest().join(&ch.path.with_extension("html")))?
                                .read_to_string(&mut content);

                            // This could cause a problem when someone displays
                            // code containing <base href=...>
                            // on the front page, however this case should be very very rare...
                            content = content
                                .lines()
                                .filter(|line| !line.contains("<base href="))
                                .collect::<Vec<&str>>()
                                .join("\n");

                            book.write_file("index.html", content.as_bytes())?;

                            info!("[*] Creating index.html from {:?} ✓",
                                  book.get_dest().join(&ch.path.with_extension("html")));
                            index = false;
                        }
                    }
                },
                _ => {},
            }
        }

        // Print version

        // Update the context with data for this file
        data.insert("path".to_owned(), json!("print.md"));
        data.insert("content".to_owned(), json!(print_content));
        data.insert("path_to_root".to_owned(), json!(utils::fs::path_to_root(Path::new("print.md"))));

        // Render the handlebars template with the data
        debug!("[*]: Render template");

        let rendered = handlebars.render("index", &data)?;

        // do several kinds of post-processing
        let rendered = build_header_links(rendered, "print.html");
        let rendered = fix_anchor_links(rendered, "print.html");
        let rendered = fix_code_blocks(rendered);
        let rendered = add_playpen_pre(rendered);

        book.write_file(Path::new("print").with_extension("html"), &rendered.into_bytes())?;
        info!("[*] Creating print.html ✓");

        // Copy static files (js, css, images, ...)

        debug!("[*] Copy static files");
        book.write_file("book.js", &theme.js)?;
        book.write_file("book.css", &theme.css)?;
        book.write_file("favicon.png", &theme.favicon)?;
        book.write_file("jquery.js", &theme.jquery)?;
        book.write_file("highlight.css", &theme.highlight_css)?;
        book.write_file("tomorrow-night.css", &theme.tomorrow_night_css)?;
        book.write_file("highlight.js", &theme.highlight_js)?;
        book.write_file("clipboard.min.js", &theme.clipboard_js)?;
        book.write_file("_FontAwesome/css/font-awesome.css", theme::FONT_AWESOME)?;
        book.write_file("_FontAwesome/fonts/fontawesome-webfont.eot", theme::FONT_AWESOME_EOT)?;
        book.write_file("_FontAwesome/fonts/fontawesome-webfont.svg", theme::FONT_AWESOME_SVG)?;
        book.write_file("_FontAwesome/fonts/fontawesome-webfont.ttf", theme::FONT_AWESOME_TTF)?;
        book.write_file("_FontAwesome/fonts/fontawesome-webfont.woff", theme::FONT_AWESOME_WOFF)?;
        book.write_file("_FontAwesome/fonts/fontawesome-webfont.woff2", theme::FONT_AWESOME_WOFF2)?;
        book.write_file("_FontAwesome/fonts/FontAwesome.ttf", theme::FONT_AWESOME_TTF)?;

        // Copy all remaining files
        utils::fs::copy_files_except_ext(book.get_src(), book.get_dest(), true, &["md"])?;

        Ok(())
    }
}

fn make_data(book: &MDBook) -> Result<serde_json::Map<String, serde_json::Value>, Box<Error>> {
    debug!("[fn]: make_data");

    let mut data = serde_json::Map::new();
    data.insert("language".to_owned(), json!("en"));
    data.insert("title".to_owned(), json!(book.get_title()));
    data.insert("description".to_owned(), json!(book.get_description()));
    data.insert("favicon".to_owned(), json!("favicon.png"));
    if let Some(livereload) = book.get_livereload() {
        data.insert("livereload".to_owned(), json!(livereload));
    }

    // Add google analytics tag
    if let Some(ref ga) = book.google_analytics {
        data.insert("google_analytics".to_owned(), json!(ga));
    }

    let mut chapters = vec![];

    for item in book.iter() {
        // Create the data to inject in the template
        let mut chapter = BTreeMap::new();

        match *item {
            BookItem::Affix(ref ch) => {
                chapter.insert("name".to_owned(), json!(ch.name));
                let path = ch.path
                    .to_str()
                    .ok_or_else(|| io::Error::new(io::ErrorKind::Other, "Could not convert path to str"))?;
                chapter.insert("path".to_owned(), json!(path));
            },
            BookItem::Chapter(ref s, ref ch) => {
                chapter.insert("section".to_owned(), json!(s));
                chapter.insert("name".to_owned(), json!(ch.name));
                let path = ch.path
                    .to_str()
                    .ok_or_else(|| io::Error::new(io::ErrorKind::Other, "Could not convert path to str"))?;
                chapter.insert("path".to_owned(), json!(path));
            },
            BookItem::Spacer => {
                chapter.insert("spacer".to_owned(), json!("_spacer_"));
            },

        }

        chapters.push(chapter);
    }

    data.insert("chapters".to_owned(), json!(chapters));

    debug!("[*]: JSON constructed");
    Ok(data)
}

fn build_header_links(html: String, filename: &str) -> String {
    let regex = Regex::new(r"<h(\d)>(.*?)</h\d>").unwrap();
    let mut id_counter = HashMap::new();

    regex
        .replace_all(&html, |caps: &Captures| {
            let level = &caps[1];
            let text = &caps[2];
            let mut id = text.to_string();
            let repl_sub = vec!["<em>",
                                "</em>",
                                "<code>",
                                "</code>",
                                "<strong>",
                                "</strong>",
                                "&lt;",
                                "&gt;",
                                "&amp;",
                                "&#39;",
                                "&quot;"];
            for sub in repl_sub {
                id = id.replace(sub, "");
            }
            let id = id.chars()
                .filter_map(|c| if c.is_alphanumeric() || c == '-' || c == '_' {
                                if c.is_ascii() {
                                    Some(c.to_ascii_lowercase())
                                } else {
                                    Some(c)
                                }
                            } else if c.is_whitespace() && c.is_ascii() {
                                Some('-')
                            } else {
                                None
                            })
                .collect::<String>();

            let id_count = *id_counter.get(&id).unwrap_or(&0);
            id_counter.insert(id.clone(), id_count + 1);

            let id = if id_count > 0 {
                format!("{}-{}", id, id_count)
            } else {
                id
            };

            format!("<a class=\"header\" href=\"{filename}#{id}\" id=\"{id}\"><h{level}>{text}</h{level}></a>",
                    level = level,
                    id = id,
                    text = text,
                    filename = filename)
        })
        .into_owned()
}

// anchors to the same page (href="#anchor") do not work because of
// <base href="../"> pointing to the root folder. This function *fixes*
// that in a very inelegant way
fn fix_anchor_links(html: String, filename: &str) -> String {
    let regex = Regex::new(r##"<a([^>]+)href="#([^"]+)"([^>]*)>"##).unwrap();
    regex
        .replace_all(&html, |caps: &Captures| {
            let before = &caps[1];
            let anchor = &caps[2];
            let after = &caps[3];

            format!("<a{before}href=\"{filename}#{anchor}\"{after}>",
                    before = before,
                    filename = filename,
                    anchor = anchor,
                    after = after)
        })
        .into_owned()
}


// The rust book uses annotations for rustdoc to test code snippets,
// like the following:
// ```rust,should_panic
// fn main() {
//     // Code here
// }
// ```
// This function replaces all commas by spaces in the code block classes
fn fix_code_blocks(html: String) -> String {
    let regex = Regex::new(r##"<code([^>]+)class="([^"]+)"([^>]*)>"##).unwrap();
    regex
        .replace_all(&html, |caps: &Captures| {
            let before = &caps[1];
            let classes = &caps[2].replace(",", " ");
            let after = &caps[3];

            format!("<code{before}class=\"{classes}\"{after}>", before = before, classes = classes, after = after)
        })
        .into_owned()
}

fn add_playpen_pre(html: String) -> String {
    let regex = Regex::new(r##"((?s)<code[^>]?class="([^"]+)".*?>(.*?)</code>)"##).unwrap();
    regex
        .replace_all(&html, |caps: &Captures| {
            let text = &caps[1];
            let classes = &caps[2];
            let code = &caps[3];

            if classes.contains("language-rust") && !classes.contains("ignore") {
                // wrap the contents in an external pre block

                if text.contains("fn main") || text.contains("quick_main!") {
                    format!("<pre class=\"playpen\">{}</pre>", text)
                } else {
                    // we need to inject our own main
                    let (attrs, code) = partition_source(code);
                    format!("<pre class=\"playpen\"><code class=\"{}\"># #![allow(unused_variables)]
{}#fn main() {{
\
                             {}
#}}</code></pre>",
                            classes,
                            attrs,
                            code)
                }
            } else {
                // not language-rust, so no-op
                format!("{}", text)
            }
        })
        .into_owned()
}

fn partition_source(s: &str) -> (String, String) {
    let mut after_header = false;
    let mut before = String::new();
    let mut after = String::new();

    for line in s.lines() {
        let trimline = line.trim();
        let header = trimline.chars().all(|c| c.is_whitespace()) || trimline.starts_with("#![");
        if !header || after_header {
            after_header = true;
            after.push_str(line);
            after.push_str("\n");
        } else {
            before.push_str(line);
            before.push_str("\n");
        }
    }

    (before, after)
}