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|
use anyhow::Result;
use quick_xml::events::{BytesStart, Event};
use quick_xml::{Reader, Writer};
use relative_path::{RelativePath, RelativePathBuf};
use std::collections::HashMap;
use std::io::Cursor;
use crate::models::{Chapter, EpubResponse};
/// Checks if a tag is a standard HTML void element that shouldn't have a closing tag.
fn is_html_void_tag(name: &[u8]) -> bool {
matches!(
name,
b"area"
| b"base"
| b"br"
| b"col"
| b"embed"
| b"hr"
| b"img"
| b"input"
| b"link"
| b"meta"
| b"param"
| b"source"
| b"track"
| b"wbr"
)
}
/// Processes the fragment and outputs a complete, EPUB-ready XHTML document.
pub fn build_epub_chapter(
epub_data: &EpubResponse,
chapter: &Chapter,
chapter_dir: &RelativePath,
fragment: &str,
stylesheet_path: &str,
url_path_to_local: &HashMap<&str, &RelativePathBuf>,
) -> Result<String> {
// Setup the XML Reader and Writer.
let mut reader = Reader::from_str(fragment);
// Preserve spacing for EPUB text formatting.
reader.config_mut().trim_text(false);
// Fragments could have unmatched tags - tell the parser not to panic if so.
reader.config_mut().check_end_names = false;
let mut writer = Writer::new(Cursor::new(Vec::new()));
// Loop through the XML events and rewrite tags.
loop {
match reader.read_event() {
Ok(Event::Start(tag_data)) => {
// If it is a void tag, convert it to a self-closing XML tag.
let tag_type = if is_html_void_tag(tag_data.name().as_ref()) {
Event::Empty
} else {
Event::Start
};
writer.write_event(tag_type(rewrite_attributes(
&tag_data,
url_path_to_local,
chapter_dir,
)))?;
}
Ok(Event::Empty(tag_data)) => {
// If tags are already empty, leave them as-is.
writer.write_event(Event::Empty(rewrite_attributes(
&tag_data,
url_path_to_local,
chapter_dir,
)))?;
}
Ok(Event::End(tag_data)) => {
// Silently drop closing tags for void elements if they exist (e.g. <img></img>).
if !is_html_void_tag(tag_data.name().as_ref()) {
writer.write_event(Event::End(tag_data))?;
}
}
Ok(Event::Eof) => break,
Ok(tag_data) => writer.write_event(tag_data)?, // Pass through text, comments, etc. unmodified.
Err(e) => anyhow::bail!(e),
}
}
// Extract the modified fragment
let processed_fragment = String::from_utf8(writer.into_inner().into_inner())?;
// Wrap in EPUB XHTML Boilerplate.
// EPUBs strictly require the w3 and idpf namespaces to validate properly.
let full_xhtml = format!(
r#"<?xml version="1.0" encoding="utf-8"?>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" lang="{lang}" xml:lang="{lang}">
<head>
<title>{title}</title>
{css}
</head>
<body>
{content}
</body>
</html>"#,
lang = epub_data.language,
title = chapter.title,
css = stylesheet_path,
content = processed_fragment,
);
Ok(full_xhtml)
}
/// Helper function to inspect tags and rewrite the elements' attributes.
fn rewrite_attributes<'a>(
tag_data: &BytesStart<'a>,
url_path_to_local: &HashMap<&str, &RelativePathBuf>,
chapter_dir: &RelativePath,
) -> BytesStart<'static> {
let name = String::from_utf8_lossy(tag_data.name().as_ref()).into_owned();
let mut new_elem = BytesStart::new(name);
for attr in tag_data.attributes().filter_map(Result::ok) {
let key = attr.key.as_ref();
// Intercept <img> tags with a "src" attribute.
if tag_data.name().as_ref() == b"img" && key == b"src" {
let url = String::from_utf8_lossy(&attr.value);
// If we have a local path, inject it instead of the absolute URL.
if let Some(local_path) = url_path_to_local.get(url.as_ref()) {
new_elem.push_attribute(("src", chapter_dir.relative(local_path).as_str()));
continue;
}
}
// Keep all other attributes intact.
new_elem.push_attribute(attr);
}
new_elem
}
|
