html.rs

// Copyright 2015 Google Inc. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

//! HTML renderer that takes an iterator of events as input.

use std::collections::HashMap;
use std::fmt;
use std::io;

use crate::strings::CowStr;
use crate::Event::*;
use crate::{Alignment, BlockQuoteKind, CodeBlockKind, Event, LinkType, Tag, TagEnd};
use pulldown_cmark_escape::{EscapedHref, EscapedHtml, EscapedHtmlBodyText};

/// Trait that enables [`HtmlWriter`] to be generic over fmt/io writers.
trait StrWrite {
    type Error;

    fn write_str(&mut self, s: &str) -> Result<(), Self::Error>;
    fn write_fmt(&mut self, args: fmt::Arguments) -> Result<(), Self::Error>;
}

#[derive(Debug)]
struct IoWriter<W>(pub W);

impl<W> StrWrite for IoWriter<W>
where
    W: io::Write,
{
    type Error = io::Error;

    #[inline]
    fn write_str(&mut self, s: &str) -> io::Result<()> {
        self.0.write_all(s.as_bytes())
    }

    #[inline]
    fn write_fmt(&mut self, args: fmt::Arguments) -> io::Result<()> {
        self.0.write_fmt(args)
    }
}

#[derive(Debug)]
struct FmtWriter<W>(pub W);

impl<W> StrWrite for FmtWriter<W>
where
    W: fmt::Write,
{
    type Error = fmt::Error;

    #[inline]
    fn write_str(&mut self, s: &str) -> fmt::Result {
        self.0.write_str(s)
    }

    #[inline]
    fn write_fmt(&mut self, args: fmt::Arguments) -> fmt::Result {
        self.0.write_fmt(args)
    }
}

enum TableState {
    Head,
    Body,
}

struct HtmlWriter<'a, I, W> {
    /// Iterator supplying events.
    iter: I,

    /// Writer to write to.
    writer: W,

    /// Whether or not the last write wrote a newline.
    end_newline: bool,

    /// Whether if inside a metadata block (text should not be written)
    in_non_writing_block: bool,

    table_state: TableState,
    table_alignments: Vec<Alignment>,
    table_cell_index: usize,
    numbers: HashMap<CowStr<'a>, usize>,
}

impl<'a, I, W> HtmlWriter<'a, I, W>
where
    I: Iterator<Item = Event<'a>>,
    W: StrWrite,
{
    fn new(iter: I, writer: W) -> Self {
        Self {
            iter,
            writer,
            end_newline: true,
            in_non_writing_block: false,
            table_state: TableState::Head,
            table_alignments: vec![],
            table_cell_index: 0,
            numbers: HashMap::new(),
        }
    }

    /// Writes a new line.
    #[inline]
    fn write_newline(&mut self) -> Result<(), W::Error> {
        self.end_newline = true;
        self.writer.write_str("\n")
    }

    /// Writes a buffer, and tracks whether or not a newline was written.
    #[inline]
    fn write(&mut self, s: &str) -> Result<(), W::Error> {
        self.writer.write_str(s)?;

        if !s.is_empty() {
            self.end_newline = s.ends_with('\n');
        }
        Ok(())
    }

    fn run(mut self) -> Result<(), W::Error> {
        while let Some(event) = self.iter.next() {
            match event {
                Start(tag) => {
                    self.start_tag(tag)?;
                }
                End(tag) => {
                    self.end_tag(tag)?;
                }
                Text(text) => {
                    if !self.in_non_writing_block {
                        write!(self.writer, "{}", EscapedHtmlBodyText(&text))?;
                        self.end_newline = text.ends_with('\n');
                    }
                }
                Code(text) => {
                    write!(self.writer, "<code>{}</code>", EscapedHtmlBodyText(&text))?;
                }
                InlineMath(text) => {
                    write!(
                        self.writer,
                        r#"<span class="math math-inline">{}</span>"#,
                        EscapedHtmlBodyText(&text)
                    )?;
                }
                DisplayMath(text) => {
                    write!(
                        self.writer,
                        r#"<span class="math math-display">{}</span>"#,
                        EscapedHtmlBodyText(&text)
                    )?;
                }
                Html(html) | InlineHtml(html) => {
                    self.write(&html)?;
                }
                SoftBreak => {
                    self.write_newline()?;
                }
                HardBreak => {
                    self.write("<br />\n")?;
                }
                Rule => {
                    if self.end_newline {
                        self.write("<hr />\n")?;
                    } else {
                        self.write("\n<hr />\n")?;
                    }
                }
                FootnoteReference(name) => {
                    let len = self.numbers.len() + 1;
                    write!(
                        self.writer,
                        "<sup class=\"footnote-reference\"><a href=\"#{}\">",
                        EscapedHtml(&name)
                    )?;
                    let number = *self.numbers.entry(name).or_insert(len);
                    write!(self.writer, "{}", number)?;
                    self.write("</a></sup>")?;
                }
                TaskListMarker(true) => {
                    self.write("<input disabled=\"\" type=\"checkbox\" checked=\"\"/>\n")?;
                }
                TaskListMarker(false) => {
                    self.write("<input disabled=\"\" type=\"checkbox\"/>\n")?;
                }
            }
        }
        Ok(())
    }

    /// Writes the start of an HTML tag.
    fn start_tag(&mut self, tag: Tag<'a>) -> Result<(), W::Error> {
        match tag {
            Tag::HtmlBlock => Ok(()),
            Tag::Paragraph => {
                if self.end_newline {
                    self.write("<p>")
                } else {
                    self.write("\n<p>")
                }
            }
            Tag::Heading {
                level,
                id,
                classes,
                attrs,
            } => {
                if self.end_newline {
                    self.end_newline = false;
                    self.write("<")?;
                } else {
                    self.write("\n<")?;
                }
                write!(self.writer, "{}", level)?;
                if let Some(id) = id {
                    write!(self.writer, " id=\"{}\"", EscapedHtml(&id))?;
                }
                let mut classes = classes.iter();
                if let Some(class) = classes.next() {
                    write!(self.writer, " class=\"{}", EscapedHtml(class))?;
                    for class in classes {
                        write!(self.writer, " {}", EscapedHtml(class))?;
                    }
                    self.write("\"")?;
                }
                for (attr, value) in attrs {
                    write!(self.writer, " {}", EscapedHtml(&attr))?;
                    if let Some(val) = value {
                        write!(self.writer, "=\"{}\"", EscapedHtml(&val))?;
                    } else {
                        self.write("=\"\"")?;
                    }
                }
                self.write(">")
            }
            Tag::Table(alignments) => {
                self.table_alignments = alignments;
                self.write("<table>")
            }
            Tag::TableHead => {
                self.table_state = TableState::Head;
                self.table_cell_index = 0;
                self.write("<thead><tr>")
            }
            Tag::TableRow => {
                self.table_cell_index = 0;
                self.write("<tr>")
            }
            Tag::TableCell => {
                match self.table_state {
                    TableState::Head => {
                        self.write("<th")?;
                    }
                    TableState::Body => {
                        self.write("<td")?;
                    }
                }
                match self.table_alignments.get(self.table_cell_index) {
                    Some(&Alignment::Left) => self.write(" style=\"text-align: left\">"),
                    Some(&Alignment::Center) => self.write(" style=\"text-align: center\">"),
                    Some(&Alignment::Right) => self.write(" style=\"text-align: right\">"),
                    _ => self.write(">"),
                }
            }
            Tag::BlockQuote(kind) => {
                let class_str = match kind {
                    None => "",
                    Some(kind) => match kind {
                        BlockQuoteKind::Note => " class=\"markdown-alert-note\"",
                        BlockQuoteKind::Tip => " class=\"markdown-alert-tip\"",
                        BlockQuoteKind::Important => " class=\"markdown-alert-important\"",
                        BlockQuoteKind::Warning => " class=\"markdown-alert-warning\"",
                        BlockQuoteKind::Caution => " class=\"markdown-alert-caution\"",
                    },
                };
                if self.end_newline {
                    self.write(&format!("<blockquote{}>\n", class_str))
                } else {
                    self.write(&format!("\n<blockquote{}>\n", class_str))
                }
            }
            Tag::CodeBlock(info) => {
                if !self.end_newline {
                    self.write_newline()?;
                }
                match info {
                    CodeBlockKind::Fenced(info) => {
                        let lang = info.split(' ').next().unwrap();
                        if lang.is_empty() {
                            self.write("<pre><code>")
                        } else {
                            write!(
                                self.writer,
                                "<pre><code class=\"language-{}\">",
                                EscapedHtml(lang)
                            )
                        }
                    }
                    CodeBlockKind::Indented => self.write("<pre><code>"),
                }
            }
            Tag::List(Some(1)) => {
                if self.end_newline {
                    self.write("<ol>\n")
                } else {
                    self.write("\n<ol>\n")
                }
            }
            Tag::List(Some(start)) => {
                if self.end_newline {
                    self.write("<ol start=\"")?;
                } else {
                    self.write("\n<ol start=\"")?;
                }
                write!(self.writer, "{}", start)?;
                self.write("\">\n")
            }
            Tag::List(None) => {
                if self.end_newline {
                    self.write("<ul>\n")
                } else {
                    self.write("\n<ul>\n")
                }
            }
            Tag::Item => {
                if self.end_newline {
                    self.write("<li>")
                } else {
                    self.write("\n<li>")
                }
            }
            Tag::Emphasis => self.write("<em>"),
            Tag::Strong => self.write("<strong>"),
            Tag::Strikethrough => self.write("<del>"),
            Tag::Link {
                link_type: LinkType::Email,
                dest_url,
                title,
                id: _,
            } => {
                write!(self.writer, "<a href=\"mailto:{}", EscapedHref(&dest_url))?;
                if !title.is_empty() {
                    write!(self.writer, "\" title=\"{}", EscapedHtml(&title))?;
                }
                self.write("\">")
            }
            Tag::Link {
                link_type: _,
                dest_url,
                title,
                id: _,
            } => {
                write!(self.writer, "<a href=\"{}", EscapedHref(&dest_url))?;
                if !title.is_empty() {
                    write!(self.writer, "\" title=\"{}", EscapedHtml(&title))?;
                }
                self.write("\">")
            }
            Tag::Image {
                link_type: _,
                dest_url,
                title,
                id: _,
            } => {
                write!(
                    self.writer,
                    "<img src=\"{}\" alt=\"",
                    EscapedHref(&dest_url)
                )?;
                self.raw_text()?;
                if !title.is_empty() {
                    write!(self.writer, "\" title=\"{}", EscapedHtml(&title))?;
                }
                self.write("\" />")
            }
            Tag::FootnoteDefinition(name) => {
                if self.end_newline {
                    self.write("<div class=\"footnote-definition\" id=\"")?;
                } else {
                    self.write("\n<div class=\"footnote-definition\" id=\"")?;
                }
                write!(
                    self.writer,
                    "{}\"><sup class=\"footnote-definition-label\">",
                    EscapedHtml(&name)
                )?;
                let len = self.numbers.len() + 1;
                let number = *self.numbers.entry(name).or_insert(len);
                write!(self.writer, "{}", number)?;
                self.write("</sup>")
            }
            Tag::MetadataBlock(_) => {
                self.in_non_writing_block = true;
                Ok(())
            }
        }
    }

    fn end_tag(&mut self, tag: TagEnd) -> Result<(), W::Error> {
        match tag {
            TagEnd::HtmlBlock => {}
            TagEnd::Paragraph => {
                self.write("</p>\n")?;
            }
            TagEnd::Heading(level) => {
                self.write("</")?;
                write!(self.writer, "{}", level)?;
                self.write(">\n")?;
            }
            TagEnd::Table => {
                self.write("</tbody></table>\n")?;
            }
            TagEnd::TableHead => {
                self.write("</tr></thead><tbody>\n")?;
                self.table_state = TableState::Body;
            }
            TagEnd::TableRow => {
                self.write("</tr>\n")?;
            }
            TagEnd::TableCell => {
                match self.table_state {
                    TableState::Head => {
                        self.write("</th>")?;
                    }
                    TableState::Body => {
                        self.write("</td>")?;
                    }
                }
                self.table_cell_index += 1;
            }
            TagEnd::BlockQuote => {
                self.write("</blockquote>\n")?;
            }
            TagEnd::CodeBlock => {
                self.write("</code></pre>\n")?;
            }
            TagEnd::List(true) => {
                self.write("</ol>\n")?;
            }
            TagEnd::List(false) => {
                self.write("</ul>\n")?;
            }
            TagEnd::Item => {
                self.write("</li>\n")?;
            }
            TagEnd::Emphasis => {
                self.write("</em>")?;
            }
            TagEnd::Strong => {
                self.write("</strong>")?;
            }
            TagEnd::Strikethrough => {
                self.write("</del>")?;
            }
            TagEnd::Link => {
                self.write("</a>")?;
            }
            TagEnd::Image => (), // shouldn't happen, handled in start
            TagEnd::FootnoteDefinition => {
                self.write("</div>\n")?;
            }
            TagEnd::MetadataBlock(_) => {
                self.in_non_writing_block = false;
            }
        }
        Ok(())
    }

    // run raw text, consuming end tag
    fn raw_text(&mut self) -> Result<(), W::Error> {
        let mut nest = 0;
        while let Some(event) = self.iter.next() {
            match event {
                Start(_) => nest += 1,
                End(_) => {
                    if nest == 0 {
                        break;
                    }
                    nest -= 1;
                }
                Html(_) => {}
                InlineHtml(text) | Code(text) | Text(text) => {
                    // Don't use EscapedHtmlBodyText here.
                    // The output of this function is used in the `alt` attribute.
                    write!(self.writer, "{}", EscapedHtml(&text))?;
                    self.end_newline = text.ends_with('\n');
                }
                InlineMath(text) => {
                    self.write("$")?;
                    write!(self.writer, "{}", EscapedHtml(&text))?;
                    self.write("$")?;
                }
                DisplayMath(text) => {
                    self.write("$$")?;
                    write!(self.writer, "{}", EscapedHtml(&text))?;
                    self.write("$$")?;
                }
                SoftBreak | HardBreak | Rule => {
                    self.write(" ")?;
                }
                FootnoteReference(name) => {
                    let len = self.numbers.len() + 1;
                    let number = *self.numbers.entry(name).or_insert(len);
                    write!(self.writer, "[{}]", number)?;
                }
                TaskListMarker(true) => self.write("[x]")?,
                TaskListMarker(false) => self.write("[ ]")?,
            }
        }
        Ok(())
    }
}

/// Iterate over an `Iterator` of `Event`s, generate HTML for each `Event`, and
/// push it to a `String`.
///
/// # Examples
///
/// ```
/// use pulldown_cmark::{html, Parser};
///
/// let markdown_str = r#"
/// hello
/// =====
///
/// * alpha
/// * beta
/// "#;
/// let parser = Parser::new(markdown_str);
///
/// let mut html_buf = String::new();
/// html::push_html(&mut html_buf, parser);
///
/// assert_eq!(html_buf, r#"<h1>hello</h1>
/// <ul>
/// <li>alpha</li>
/// <li>beta</li>
/// </ul>
/// "#);
/// ```
pub fn push_html<'a, I>(s: &mut String, iter: I)
where
    I: Iterator<Item = Event<'a>>,
{
    write_html_fmt(s, iter).unwrap()
}

/// Iterate over an `Iterator` of `Event`s, generate HTML for each `Event`, and
/// write it out to an I/O stream.
///
/// **Note**: using this function with an unbuffered writer like a file or socket
/// will result in poor performance. Wrap these in a
/// [`BufWriter`](https://doc.rust-lang.org/std/io/struct.BufWriter.html) to
/// prevent unnecessary slowdowns.
///
/// # Examples
///
/// ```
/// use pulldown_cmark::{html, Parser};
/// use std::io::Cursor;
///
/// let markdown_str = r#"
/// hello
/// =====
///
/// * alpha
/// * beta
/// "#;
/// let mut bytes = Vec::new();
/// let parser = Parser::new(markdown_str);
///
/// html::write_html_io(Cursor::new(&mut bytes), parser);
///
/// assert_eq!(&String::from_utf8_lossy(&bytes)[..], r#"<h1>hello</h1>
/// <ul>
/// <li>alpha</li>
/// <li>beta</li>
/// </ul>
/// "#);
/// ```
pub fn write_html_io<'a, I, W>(writer: W, iter: I) -> std::io::Result<()>
where
    I: Iterator<Item = Event<'a>>,
    W: std::io::Write,
{
    HtmlWriter::new(iter, IoWriter(writer)).run()
}

/// Iterate over an `Iterator` of `Event`s, generate HTML for each `Event`, and
/// write it into Unicode-accepting buffer or stream.
///
/// # Examples
///
/// ```
/// use pulldown_cmark::{html, Parser};
///
/// let markdown_str = r#"
/// hello
/// =====
///
/// * alpha
/// * beta
/// "#;
/// let mut buf = String::new();
/// let parser = Parser::new(markdown_str);
///
/// html::write_html_fmt(&mut buf, parser);
///
/// assert_eq!(buf, r#"<h1>hello</h1>
/// <ul>
/// <li>alpha</li>
/// <li>beta</li>
/// </ul>
/// "#);
/// ```
pub fn write_html_fmt<'a, I, W>(writer: W, iter: I) -> std::fmt::Result
where
    I: Iterator<Item = Event<'a>>,
    W: std::fmt::Write,
{
    HtmlWriter::new(iter, FmtWriter(writer)).run()
}