import CMarkGFM
import Foundation
enum MobileHtmlRenderer {
static func render(markdown: String, title: String?, fontSize: Int = 17) -> String {
let body = markdownToHTML(markdown)
let hero = heroTitleHTML(noteTitle: title, markdown: markdown)
// Critical: the dynamic --font-size override MUST come after
// bundledCSS, not before. mobile-reader.css declares its own default
// `--font-size: 17px` on :root; same selector + same property means
// whichever rule appears later wins. Putting the inline override
// before bundledCSS silently lost the font-size selection — tap
// Small/Medium/Large produced no visible change.
return """
\(hero)\(body)
"""
}
private static func markdownToHTML(_ markdown: String) -> String {
_ = ensureExtensionsRegistered
guard let parser = cmark_parser_new(CMARK_OPT_FOOTNOTES) else { return "" }
defer { cmark_parser_free(parser) }
for extName in ["table", "footnotes", "strikethrough", "tasklist"] {
if let ext = cmark_find_syntax_extension(extName) {
cmark_parser_attach_syntax_extension(parser, ext)
}
}
cmark_parser_feed(parser, markdown, markdown.utf8.count)
guard let node = cmark_parser_finish(parser) else { return "" }
defer { cmark_node_free(node) }
guard let cString = cmark_render_html(node, CMARK_OPT_UNSAFE | CMARK_OPT_HARDBREAKS, nil) else { return "" }
let html = String(cString: cString)
free(cString)
return html
}
// MARK: - Hero title
/// Decide whether to inject a large hero title at the top of the reader.
/// Returns either an empty string or a `…
` block.
///
/// Rules (see plan): only inject when we have a non-empty filename AND the
/// document does not already begin with an H1. If the document opens with
/// an H1 we always defer to the author, regardless of whether the H1 text
/// matches the filename — same-text means redundant; different-text means
/// the author is making an intentional editorial choice.
private static func heroTitleHTML(noteTitle: String?, markdown: String) -> String {
guard let raw = noteTitle else { return "" }
let trimmedTitle = raw.trimmingCharacters(in: .whitespacesAndNewlines)
guard !trimmedTitle.isEmpty else { return "" }
if firstTopLevelH1Text(markdown) != nil {
return ""
}
return "\(escapeHTML(trimmedTitle))
\n"
}
/// Returns the text content of the first top-level H1 (`# X`) in the
/// document, skipping a YAML-style frontmatter block at the very top.
/// Returns nil when the first non-blank, non-frontmatter line is not an H1.
/// `hasPrefix("# ")` already excludes `## `, `### `, etc., because those
/// have `#` (not space) at index 1.
private static func firstTopLevelH1Text(_ markdown: String) -> String? {
let stripped = stripFrontmatter(markdown)
for line in stripped.split(omittingEmptySubsequences: false, whereSeparator: \.isNewline) {
let trimmed = line.trimmingCharacters(in: .whitespaces)
if trimmed.isEmpty { continue }
guard trimmed.hasPrefix("# ") else { return nil }
let text = trimmed.dropFirst(2).trimmingCharacters(in: .whitespaces)
return text.isEmpty ? nil : text
}
return nil
}
/// Strip a leading YAML-style frontmatter block (`---\n…\n---`).
/// If the document doesn't start with `---` followed by a newline, return
/// the original markdown unchanged — three dashes alone are a horizontal
/// rule in CommonMark and we don't want to swallow them.
private static func stripFrontmatter(_ markdown: String) -> Substring {
guard markdown.hasPrefix("---\n") || markdown.hasPrefix("---\r\n") else {
return Substring(markdown)
}
let afterOpening = markdown.index(markdown.startIndex, offsetBy: markdown.hasPrefix("---\r\n") ? 5 : 4)
guard let closingRange = markdown.range(of: "\n---", range: afterOpening.. String {
var out = ""
out.reserveCapacity(s.count)
for ch in s {
switch ch {
case "&": out.append("&")
case "<": out.append("<")
case ">": out.append(">")
case "\"": out.append(""")
case "'": out.append("'")
default: out.append(ch)
}
}
return out
}
private static let ensureExtensionsRegistered: Void = {
cmark_gfm_core_extensions_ensure_registered()
}()
private static let bundledCSS = loadCSS()
private static func loadCSS() -> String {
guard let url = Bundle.main.url(forResource: "mobile-reader", withExtension: "css"),
let css = try? String(contentsOf: url, encoding: .utf8)
else {
return fallbackCSS
}
return css
}
private static let fallbackCSS = """
body {
font-family: -apple-system, sans-serif;
font-size: var(--font-size, 17px);
line-height: 1.7;
max-width: 680px;
margin: 0 auto;
padding: 20px;
color: #262626;
background: #f9f6f0;
}
@media (prefers-color-scheme: dark) {
body { background: #121312; color: #e5e5ea; }
}
"""
}