dmc-parser 0.3.4

//! GitHub-style heading-anchor slug generator. Mirrors npm `github-slugger`
//! (used by `rehype-slug`): punctuation is stripped, NOT replaced, so
//! `0.4.3` -> `043` and `It's` -> `its` (matches velite output).
//!
//! For document-scoped dedupe (`#patch-changes`, `#patch-changes-1`, ...)
//! use [`Slugger`].

use std::collections::HashMap;

/// Compute the GitHub-style slug, ignoring dedupe. For document-wide
/// dedupe, use [`Slugger::slug`].
pub fn github_slugify(input: &str) -> String {
  let lower = input.trim().to_lowercase();
  let mut out = String::with_capacity(lower.len());
  let mut prev_dash = false;
  for ch in lower.chars() {
    if ch.is_control() {
      continue;
    }
    if ch.is_whitespace() {
      if !prev_dash && !out.is_empty() {
        out.push('-');
        prev_dash = true;
      }
      continue;
    }
    // github-slugger "strip, don't replace": drop anything that isn't
    // alphanumeric / `_` / `-`. Existing `-` collapses with whitespace runs.
    if ch.is_alphanumeric() || ch == '_' || ch == '-' {
      if ch == '-' {
        if prev_dash {
          continue;
        }
        out.push('-');
        prev_dash = true;
      } else {
        out.push(ch);
        prev_dash = false;
      }
    }
  }
  while out.ends_with('-') {
    out.pop();
  }
  out
}

/// Document-scoped slugger. Collisions get a `-1`, `-2`, ... suffix.
#[derive(Debug, Default)]
pub struct Slugger {
  seen: HashMap<String, u32>,
}

impl Slugger {
  pub fn new() -> Self {
    Self { seen: HashMap::new() }
  }

  /// Slug for `text`, with `-N` suffix on the N+1th collision. Empty input
  /// -> empty string; dedupe still applies (`""`, then `"-1"`).
  pub fn slug(&mut self, text: &str) -> String {
    let base = github_slugify(text);
    let count = self.seen.entry(base.clone()).or_insert(0);
    let out = if *count == 0 { base.clone() } else { format!("{}-{}", base, *count) };
    *count += 1;
    out
  }
}

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

  #[test]
  fn strips_dots() {
    assert_eq!(github_slugify("0.4.3"), "043");
  }

  #[test]
  fn strips_apostrophes() {
    assert_eq!(github_slugify("How It's Built"), "how-its-built");
  }

  #[test]
  fn replaces_spaces_with_dash() {
    assert_eq!(github_slugify("Patch Changes"), "patch-changes");
  }

  #[test]
  fn collapses_runs() {
    assert_eq!(github_slugify("Hello -- World"), "hello-world");
    assert_eq!(github_slugify("foo   bar"), "foo-bar");
  }

  #[test]
  fn dedupes() {
    let mut s = Slugger::new();
    assert_eq!(s.slug("Patch Changes"), "patch-changes");
    assert_eq!(s.slug("Patch Changes"), "patch-changes-1");
    assert_eq!(s.slug("Patch Changes"), "patch-changes-2");
  }

  #[test]
  fn keeps_underscores_and_existing_dashes() {
    assert_eq!(github_slugify("foo_bar-baz"), "foo_bar-baz");
  }
}