mdream 1.5.0

Fastest HTML-to-Markdown converter. Zero dependencies, streaming support.
Documentation 
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//! Tailwind utility-class to Markdown-emphasis mapping.

#[inline]
fn extract_base_class(class: &str) -> (&str, &str) {
  let breakpoints = ["sm:", "md:", "lg:", "xl:", "2xl:"];
  for bp in breakpoints {
    if let Some(rest) = class.strip_prefix(bp) {
      return (rest, bp);
    }
  }
  (class, "")
}

pub(crate) fn process_tailwind_classes(
  classes_attr: &str,
) -> (Option<String>, Option<String>, bool) {
  let mut classes: Vec<&str> = classes_attr.split_whitespace().collect();
  let bp_weight = |bp| match bp {
    "" => 0,
    "sm:" => 1,
    "md:" => 2,
    "lg:" => 3,
    "xl:" => 4,
    "2xl:" => 5,
    _ => 6,
  };
  classes.sort_by_key(|c| bp_weight(extract_base_class(c).1));

  let mut prefix = String::new();
  let mut suffix = String::new();
  let mut hidden = false;

  let mut weight = None;
  let mut emphasis = None;
  let mut decoration = None;
  let mut display_hidden = false;
  let mut position_hidden = false;

  for cls in classes {
    let base = extract_base_class(cls).0;
    if base == "italic" {
      emphasis = Some(("*", "*"));
    } else if base == "not-italic" {
      emphasis = None;
    } else if base == "font-bold"
      || base == "font-semibold"
      || base == "font-black"
      || base == "font-extrabold"
      || base == "font-medium"
      || base == "bold"
    {
      weight = Some(("**", "**"));
    } else if base.contains("font-") {
      weight = None;
    } else if base.contains("line-through") || base.contains("underline") {
      decoration = Some(("~~", "~~"));
    } else if base == "hidden" || base.contains("invisible") {
      display_hidden = true;
    } else if base == "block" || base == "flex" || base == "inline" {
      display_hidden = false;
    } else if base == "absolute" || base == "fixed" || base == "sticky" {
      position_hidden = true;
    } else if base == "static" || base == "relative" {
      position_hidden = false;
    }
  }

  if display_hidden || position_hidden {
    hidden = true;
  }

  if let Some((p, s)) = weight {
    prefix.push_str(p);
    suffix.insert_str(0, s);
  }
  if let Some((p, s)) = emphasis {
    prefix.push_str(p);
    suffix.insert_str(0, s);
  }
  if let Some((p, s)) = decoration {
    prefix.push_str(p);
    suffix.insert_str(0, s);
  }

  (
    if prefix.is_empty() {
      None
    } else {
      Some(prefix)
    },
    if suffix.is_empty() {
      None
    } else {
      Some(suffix)
    },
    hidden,
  )
}

#[cfg(test)]
mod tests {
  use super::*;

  #[test]
  fn font_weight_maps_to_bold() {
    let (p, s, hidden) = process_tailwind_classes("font-bold");
    assert_eq!(p.as_deref(), Some("**"));
    assert_eq!(s.as_deref(), Some("**"));
    assert!(!hidden);
  }

  #[test]
  fn italic_maps_to_emphasis() {
    let (p, s, _) = process_tailwind_classes("italic");
    assert_eq!(p.as_deref(), Some("*"));
    assert_eq!(s.as_deref(), Some("*"));
  }

  #[test]
  fn strikethrough_and_underline() {
    let (p, _, _) = process_tailwind_classes("line-through");
    assert_eq!(p.as_deref(), Some("~~"));
    let (p, _, _) = process_tailwind_classes("underline");
    assert_eq!(p.as_deref(), Some("~~"));
  }

  #[test]
  fn hidden_display_flags_hidden() {
    assert!(process_tailwind_classes("hidden").2);
    assert!(process_tailwind_classes("invisible").2);
    assert!(process_tailwind_classes("absolute").2);
    // a later display class overrides hidden
    assert!(!process_tailwind_classes("hidden block").2);
    assert!(!process_tailwind_classes("absolute relative").2);
  }

  #[test]
  fn responsive_prefix_sorting() {
    // base class (no breakpoint) wins over later breakpoint variants
    let (_, _, hidden) = process_tailwind_classes("md:block hidden");
    // "hidden" (weight 0) sorts before "md:block" (weight 2): block wins last
    assert!(!hidden);
  }

  #[test]
  fn combined_classes_nest_delimiters() {
    let (p, s, _) = process_tailwind_classes("font-bold italic");
    assert_eq!(p.as_deref(), Some("***"));
    assert_eq!(s.as_deref(), Some("***"));
  }

  #[test]
  fn no_recognised_classes_yields_none() {
    let (p, s, hidden) = process_tailwind_classes("text-lg p-4");
    assert!(p.is_none());
    assert!(s.is_none());
    assert!(!hidden);
  }

  #[test]
  fn not_italic_does_not_emphasise() {
    // `not-italic` must not match like `italic`
    let (p, s, _) = process_tailwind_classes("not-italic");
    assert!(p.is_none());
    assert!(s.is_none());
  }
}