veryl 0.20.1

A modern hardware description language
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// This file is based on:
//
// https://github.com/badboy/mdbook-mermaid
// Released under the MPL-2.0 license

use crate::doc::utils::escape_html;
use mdbook_driver::book::{Book, BookItem, Chapter};
use mdbook_driver::errors::Result;
use mdbook_preprocessor::{Preprocessor, PreprocessorContext};
use pulldown_cmark::{CodeBlockKind::*, Event, Options, Parser, Tag, TagEnd};

pub struct Mermaid;

impl Preprocessor for Mermaid {
    fn name(&self) -> &str {
        "mermaid"
    }

    fn run(&self, _ctx: &PreprocessorContext, mut book: Book) -> Result<Book> {
        let mut res = None;
        book.for_each_mut(|item: &mut BookItem| {
            if let Some(Err(_)) = res {
                return;
            }

            if let BookItem::Chapter(ref mut chapter) = *item {
                res = Some(Mermaid::add_mermaid(chapter).map(|md| {
                    chapter.content = md;
                }));
            }
        });

        res.unwrap_or(Ok(())).map(|_| book)
    }

    fn supports_renderer(&self, renderer: &str) -> Result<bool> {
        Ok(renderer == "html")
    }
}

impl Mermaid {
    fn add_mermaid(chapter: &mut Chapter) -> Result<String> {
        let content = &chapter.content;
        let mut mermaid_content = String::new();
        let mut in_mermaid_block = false;

        let mut opts = Options::empty();
        opts.insert(Options::ENABLE_TABLES);
        opts.insert(Options::ENABLE_FOOTNOTES);
        opts.insert(Options::ENABLE_STRIKETHROUGH);
        opts.insert(Options::ENABLE_TASKLISTS);

        let mut code_span = 0..0;
        let mut start_new_code_span = true;

        let mut mermaid_blocks = vec![];

        let events = Parser::new_ext(content, opts);
        for (e, span) in events.into_offset_iter() {
            if let Event::Start(Tag::CodeBlock(Fenced(code))) = e.clone() {
                if &*code == "mermaid" {
                    in_mermaid_block = true;
                    mermaid_content.clear();
                }
                continue;
            }

            if !in_mermaid_block {
                continue;
            }

            // We're in the code block. The text is what we want.
            // Code blocks can come in multiple text events.

            if let Event::Text(_) = e {
                if start_new_code_span {
                    code_span = span;
                    start_new_code_span = false;
                } else {
                    code_span = code_span.start..span.end;
                }

                continue;
            }

            if let Event::End(TagEnd::CodeBlock) = e {
                in_mermaid_block = false;

                let mermaid_content = &content[code_span.clone()];
                let mermaid_content = escape_html(mermaid_content);
                let mermaid_content = mermaid_content.replace("\r\n", "\n");
                let mermaid_code = format!("<pre class=\"mermaid\">{mermaid_content}</pre>\n\n");
                mermaid_blocks.push((span, mermaid_code));

                start_new_code_span = true;
            }
        }

        let mut content = content.to_string();
        for (span, block) in mermaid_blocks.iter().rev() {
            let pre_content = &content[0..span.start];
            let post_content = &content[span.end..];

            content = format!("{pre_content}\n{block}{post_content}");
        }
        Ok(content)
    }
}