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|
use std::fmt::Write;
use typst_library::diag::{bail, At, SourceResult, StrResult};
use typst_library::foundations::Repr;
use typst_syntax::Span;
use crate::{
attr, charsets, tag, HtmlDocument, HtmlElement, HtmlFrame, HtmlNode, HtmlTag,
};
/// Encodes an HTML document into a string.
pub fn html(document: &HtmlDocument) -> SourceResult<String> {
let mut w = Writer { pretty: true, ..Writer::default() };
w.buf.push_str("<!DOCTYPE html>");
write_indent(&mut w);
write_element(&mut w, &document.root)?;
if w.pretty {
w.buf.push('\n');
}
Ok(w.buf)
}
#[derive(Default)]
struct Writer {
/// The output buffer.
buf: String,
/// The current indentation level
level: usize,
/// Whether pretty printing is enabled.
pretty: bool,
}
/// Writes a newline and indent, if pretty printing is enabled.
fn write_indent(w: &mut Writer) {
if w.pretty {
w.buf.push('\n');
for _ in 0..w.level {
w.buf.push_str(" ");
}
}
}
/// Encodes an HTML node into the writer.
fn write_node(w: &mut Writer, node: &HtmlNode) -> SourceResult<()> {
match node {
HtmlNode::Tag(_) => {}
HtmlNode::Text(text, span) => write_text(w, text, *span)?,
HtmlNode::Element(element) => write_element(w, element)?,
HtmlNode::Frame(frame) => write_frame(w, frame),
}
Ok(())
}
/// Encodes plain text into the writer.
fn write_text(w: &mut Writer, text: &str, span: Span) -> SourceResult<()> {
for c in text.chars() {
if charsets::is_valid_in_normal_element_text(c) {
w.buf.push(c);
} else {
write_escape(w, c).at(span)?;
}
}
Ok(())
}
/// Encodes one element into the writer.
fn write_element(w: &mut Writer, element: &HtmlElement) -> SourceResult<()> {
w.buf.push('<');
w.buf.push_str(&element.tag.resolve());
for (attr, value) in &element.attrs.0 {
w.buf.push(' ');
w.buf.push_str(&attr.resolve());
// If the string is empty, we can use shorthand syntax.
// `<elem attr="">..</div` is equivalent to `<elem attr>..</div>`
if !value.is_empty() {
w.buf.push('=');
w.buf.push('"');
for c in value.chars() {
if charsets::is_valid_in_attribute_value(c) {
w.buf.push(c);
} else {
write_escape(w, c).at(element.span)?;
}
}
w.buf.push('"');
}
}
w.buf.push('>');
if tag::is_void(element.tag) {
if !element.children.is_empty() {
bail!(element.span, "HTML void elements must not have children");
}
return Ok(());
}
if tag::is_raw(element.tag) {
write_raw(w, element)?;
} else if !element.children.is_empty() {
write_children(w, element)?;
}
w.buf.push_str("</");
w.buf.push_str(&element.tag.resolve());
w.buf.push('>');
Ok(())
}
/// Encodes the children of an element.
fn write_children(w: &mut Writer, element: &HtmlElement) -> SourceResult<()> {
// See HTML spec § 13.1.2.5.
if matches!(element.tag, tag::pre | tag::textarea) && starts_with_newline(element) {
w.buf.push('\n');
}
let pretty = w.pretty;
let pretty_inside = allows_pretty_inside(element.tag)
&& element.children.iter().any(|node| match node {
HtmlNode::Element(child) => wants_pretty_around(child.tag),
_ => false,
});
w.pretty &= pretty_inside;
let mut indent = w.pretty;
w.level += 1;
for c in &element.children {
let pretty_around = match c {
HtmlNode::Tag(_) => continue,
HtmlNode::Element(child) => w.pretty && wants_pretty_around(child.tag),
HtmlNode::Text(..) | HtmlNode::Frame(_) => false,
};
if core::mem::take(&mut indent) || pretty_around {
write_indent(w);
}
write_node(w, c)?;
indent = pretty_around;
}
w.level -= 1;
write_indent(w);
w.pretty = pretty;
Ok(())
}
/// Whether the first character in the element is a newline.
fn starts_with_newline(element: &HtmlElement) -> bool {
for child in &element.children {
match child {
HtmlNode::Tag(_) => {}
HtmlNode::Text(text, _) => return text.starts_with(['\n', '\r']),
_ => return false,
}
}
false
}
/// Encodes the contents of a raw text element.
fn write_raw(w: &mut Writer, element: &HtmlElement) -> SourceResult<()> {
let text = collect_raw_text(element)?;
if let Some(closing) = find_closing_tag(&text, element.tag) {
bail!(
element.span,
"HTML raw text element cannot contain its own closing tag";
hint: "the sequence `{closing}` appears in the raw text",
)
}
let mode = if w.pretty { RawMode::of(element, &text) } else { RawMode::Keep };
match mode {
RawMode::Keep => {
w.buf.push_str(&text);
}
RawMode::Wrap => {
w.buf.push('\n');
w.buf.push_str(&text);
write_indent(w);
}
RawMode::Indent => {
w.level += 1;
for line in text.lines() {
write_indent(w);
w.buf.push_str(line);
}
w.level -= 1;
write_indent(w);
}
}
Ok(())
}
/// Collects the textual contents of a raw text element.
fn collect_raw_text(element: &HtmlElement) -> SourceResult<String> {
let mut output = String::new();
for c in &element.children {
match c {
HtmlNode::Tag(_) => continue,
HtmlNode::Text(text, _) => output.push_str(text),
HtmlNode::Element(_) | HtmlNode::Frame(_) => {
let span = match c {
HtmlNode::Element(child) => child.span,
_ => element.span,
};
bail!(span, "HTML raw text element cannot have non-text children")
}
};
}
Ok(output)
}
/// Finds a closing sequence for the given tag in the text, if it exists.
///
/// See HTML spec § 13.1.2.6.
fn find_closing_tag(text: &str, tag: HtmlTag) -> Option<&str> {
let s = tag.resolve();
let len = s.len();
text.match_indices("</").find_map(|(i, _)| {
let rest = &text[i + 2..];
let disallowed = rest.len() >= len
&& rest[..len].eq_ignore_ascii_case(&s)
&& rest[len..].starts_with(['\t', '\n', '\u{c}', '\r', ' ', '>', '/']);
disallowed.then(|| &text[i..i + 2 + len])
})
}
/// How to format the contents of a raw text element.
enum RawMode {
/// Just don't touch it.
Keep,
/// Newline after the opening and newline + indent before the closing tag.
Wrap,
/// Newlines after opening and before closing tag and each line indented.
Indent,
}
impl RawMode {
fn of(element: &HtmlElement, text: &str) -> Self {
match element.tag {
tag::script
if !element.attrs.0.iter().any(|(attr, value)| {
*attr == attr::r#type && value != "text/javascript"
}) =>
{
// Template literals can be multi-line, so indent may change
// the semantics of the JavaScript.
if text.contains('`') {
Self::Wrap
} else {
Self::Indent
}
}
tag::style => Self::Indent,
_ => Self::Keep,
}
}
}
/// Whether we are allowed to add an extra newline at the start and end of the
/// element's contents.
///
/// Technically, users can change CSS `display` properties such that the
/// insertion of whitespace may actually impact the visual output. For example,
/// <https://www.w3.org/TR/css-text-3/#example-af2745cd> shows how adding CSS
/// rules to `<p>` can make it sensitive to whitespace. For this reason, we
/// should also respect the `style` tag in the future.
fn allows_pretty_inside(tag: HtmlTag) -> bool {
(tag::is_block_by_default(tag) && tag != tag::pre)
|| tag::is_tabular_by_default(tag)
|| tag == tag::li
}
/// Whether newlines should be added before and after the element if the parent
/// allows it.
///
/// In contrast to `allows_pretty_inside`, which is purely spec-driven, this is
/// more subjective and depends on preference.
fn wants_pretty_around(tag: HtmlTag) -> bool {
allows_pretty_inside(tag) || tag::is_metadata(tag) || tag == tag::pre
}
/// Escape a character.
fn write_escape(w: &mut Writer, c: char) -> StrResult<()> {
// See <https://html.spec.whatwg.org/multipage/syntax.html#syntax-charref>
match c {
'&' => w.buf.push_str("&"),
'<' => w.buf.push_str("<"),
'>' => w.buf.push_str(">"),
'"' => w.buf.push_str("""),
'\'' => w.buf.push_str("'"),
c if charsets::is_w3c_text_char(c) && c != '\r' => {
write!(w.buf, "&#x{:x};", c as u32).unwrap()
}
_ => bail!("the character `{}` cannot be encoded in HTML", c.repr()),
}
Ok(())
}
/// Encode a laid out frame into the writer.
fn write_frame(w: &mut Writer, frame: &HtmlFrame) {
// FIXME: This string replacement is obviously a hack.
let svg = typst_svg::svg_frame(&frame.inner).replace(
"<svg class",
&format!(
"<svg style=\"overflow: visible; width: {}em; height: {}em;\" class",
frame.inner.width() / frame.text_size,
frame.inner.height() / frame.text_size,
),
);
w.buf.push_str(&svg);
}
|
