focaccia 2.0.0

no_std implementation of Unicode case folding comparisons
Documentation 
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use core::cmp::Ordering;

use crate::folding::mapping::{lookup, Mode};

/// Compare two strings with Full Unicode case folding for Turkic languages.
///
/// This function is implemented with a lookup table generated from Unicode case
/// folding tables.
///
/// # Examples
///
/// ```
/// # use core::cmp::Ordering;
/// # use focaccia::unicode_full_turkic_casecmp;
/// assert_eq!(unicode_full_turkic_casecmp("İstanbul", "istanbul"), Ordering::Equal);
/// assert_ne!(unicode_full_turkic_casecmp("İstanbul", "Istanbul"), Ordering::Equal);
/// ```
///
/// # Examples – Full
///
/// Turkic case folding is largely compatible with full Unicode case folding.
///
/// ```
/// # use core::cmp::Ordering;
/// # use focaccia::unicode_full_turkic_casecmp;
/// assert_eq!(unicode_full_turkic_casecmp("MASSE", "Maße"), Ordering::Equal);
/// assert_eq!(unicode_full_turkic_casecmp("São Paulo", "Sao Paulo"), Ordering::Greater);
/// ```
#[inline]
#[must_use]
pub fn casecmp(left: &str, right: &str) -> Ordering {
    let left = left.chars().flat_map(|c| lookup(c, Mode::Turkic));
    let right = right.chars().flat_map(|c| lookup(c, Mode::Turkic));
    left.cmp(right)
}

/// Check two strings for equality with Full Unicode case folding for Turkic
/// languages.
///
/// This function is implemented with a lookup table generated from Unicode case
/// folding tables.
///
/// # Examples
///
/// ```
/// # use focaccia::unicode_full_turkic_case_eq;
/// assert!(unicode_full_turkic_case_eq("İstanbul", "istanbul"));
/// assert!(!unicode_full_turkic_case_eq("İstanbul", "Istanbul"));
/// ```
///
/// # Examples – Full
///
/// Turkic case folding is largely compatible with full Unicode case folding.
///
/// ```
/// # use focaccia::unicode_full_turkic_case_eq;
/// assert!(unicode_full_turkic_case_eq("MASSE", "Maße"));
/// assert!(!unicode_full_turkic_case_eq("São Paulo", "Sao Paulo"));
/// ```
#[inline]
#[must_use]
pub fn case_eq(left: &str, right: &str) -> bool {
    let left = left.chars().flat_map(|c| lookup(c, Mode::Turkic));
    let right = right.chars().flat_map(|c| lookup(c, Mode::Turkic));
    left.eq(right)
}

#[cfg(test)]
mod tests {
    use core::cmp::Ordering;

    use super::{case_eq, casecmp};

    #[test]
    fn empty_string() {
        assert!(case_eq("", ""));
        assert_eq!(casecmp("", ""), Ordering::Equal);

        assert!(!case_eq("", "rake"));
        assert_eq!(casecmp("", "rake"), Ordering::Less);

        assert!(!case_eq("rake", ""));
        assert_eq!(casecmp("rake", ""), Ordering::Greater);

        assert!(!case_eq("", "São Paulo"));
        assert_eq!(casecmp("", "São Paulo"), Ordering::Less);

        assert!(!case_eq("São Paulo", ""));
        assert_eq!(casecmp("São Paulo", ""), Ordering::Greater);

        assert!(!case_eq("", "İstanbul"));
        assert_eq!(casecmp("", "İstanbul"), Ordering::Less);

        assert!(!case_eq("İstanbul", ""));
        assert_eq!(casecmp("İstanbul", ""), Ordering::Greater);
    }

    #[test]
    fn unicode_replacement_character() {
        assert!(case_eq("\u{FFFD}", "\u{FFFD}"));
        assert_eq!(casecmp("\u{FFFD}", "\u{FFFD}"), Ordering::Equal);

        assert_eq!(casecmp("\u{FFFD}", "\u{FFFD}yam"), Ordering::Less);
        assert_eq!(casecmp("\u{FFFD}yam", "\u{FFFD}"), Ordering::Greater);
    }

    #[test]
    fn compares_symbols_without_regard_to_case() {
        assert!(!case_eq("abcdef", "abcde"));
        assert!(case_eq("aBcDeF", "abcdef"));
        assert!(!case_eq("abcdef", "abcdefg"));
        assert!(case_eq("abcdef", "ABCDEF"));

        assert_eq!(casecmp("abcdef", "abcde"), Ordering::Greater);
        assert_eq!(casecmp("aBcDeF", "abcdef"), Ordering::Equal);
        assert_eq!(casecmp("abcdef", "abcdefg"), Ordering::Less);
        assert_eq!(casecmp("abcdef", "ABCDEF"), Ordering::Equal);

        assert_eq!(casecmp("abcdef", "abcde") as i32, 1);
        assert_eq!(casecmp("aBcDeF", "abcdef") as i32, 0);
        assert_eq!(casecmp("abcdef", "abcdefg") as i32, -1);
        assert_eq!(casecmp("abcdef", "ABCDEF") as i32, 0);
        assert_eq!(casecmp("abcdef", "abcde") as i32, 1);
    }

    #[test]
    fn non_ascii_chars_that_are_not_fold_eq_are_not_eq() {
        // -- UTF-8 --
        let upper_a_tilde = "Ã";
        let lower_a_tilde = "ã";
        let upper_a_umlaut = "Ä";
        let lower_a_umlaut = "ä";

        // From `spec/core/symbol/casecmp_spec.rb`:
        //
        // ```ruby
        // lower_a_tilde.casecmp?(lower_a_umlaut).should_not == true
        // lower_a_umlaut.casecmp?(lower_a_tilde).should_not == true
        // upper_a_tilde.casecmp?(upper_a_umlaut).should_not == true
        // upper_a_umlaut.casecmp?(upper_a_tilde).should_not == true
        // ```
        assert!(!case_eq(lower_a_tilde, lower_a_umlaut));
        assert!(!case_eq(lower_a_umlaut, lower_a_tilde));
        assert!(!case_eq(upper_a_tilde, upper_a_umlaut));
        assert!(!case_eq(upper_a_umlaut, upper_a_tilde));

        assert_ne!(casecmp(lower_a_tilde, lower_a_umlaut), Ordering::Equal);
        assert_ne!(casecmp(lower_a_umlaut, lower_a_tilde), Ordering::Equal);
        assert_ne!(casecmp(upper_a_tilde, upper_a_umlaut), Ordering::Equal);
        assert_ne!(casecmp(upper_a_umlaut, upper_a_tilde), Ordering::Equal);
    }

    #[test]
    fn does_case_mapping_for_unicode_chars() {
        // -- UTF-8 --
        let upper_a_tilde = "Ã";
        let lower_a_tilde = "ã";
        let upper_a_umlaut = "Ä";
        let lower_a_umlaut = "ä";

        // From `spec/core/symbol/casecmp_spec.rb`:
        //
        // ```ruby
        // upper_a_tilde.casecmp?(lower_a_tilde).should == true
        // upper_a_umlaut.casecmp?(lower_a_umlaut).should == true
        // lower_a_tilde.casecmp?(upper_a_tilde).should == true
        // lower_a_umlaut.casecmp?(upper_a_umlaut).should == true
        // ```
        assert!(case_eq(upper_a_tilde, lower_a_tilde));
        assert!(case_eq(upper_a_umlaut, lower_a_umlaut));
        assert!(case_eq(lower_a_tilde, upper_a_tilde));
        assert!(case_eq(lower_a_umlaut, upper_a_umlaut));

        assert_eq!(casecmp(upper_a_tilde, lower_a_tilde), Ordering::Equal);
        assert_eq!(casecmp(upper_a_umlaut, lower_a_umlaut), Ordering::Equal);
        assert_eq!(casecmp(lower_a_tilde, upper_a_tilde), Ordering::Equal);
        assert_eq!(casecmp(lower_a_umlaut, upper_a_umlaut), Ordering::Equal);
    }

    #[test]
    fn does_case_mapping_for_turkic_unicode_chars() {
        // -- UTF-8 --
        let upper_dotless_i = "I";
        let lower_dotless_i = "ı";
        let upper_dotted_i = "İ";
        let lower_dotted_i = "i";

        assert!(case_eq(upper_dotless_i, lower_dotless_i));
        assert!(case_eq(upper_dotted_i, lower_dotted_i));
        assert!(case_eq(lower_dotless_i, upper_dotless_i));
        assert!(case_eq(lower_dotted_i, upper_dotted_i));

        assert_eq!(casecmp(upper_dotless_i, lower_dotless_i), Ordering::Equal);
        assert_eq!(casecmp(upper_dotted_i, lower_dotted_i), Ordering::Equal);
        assert_eq!(casecmp(lower_dotless_i, upper_dotless_i), Ordering::Equal);
        assert_eq!(casecmp(lower_dotted_i, upper_dotted_i), Ordering::Equal);

        assert!(!case_eq(upper_dotless_i, upper_dotted_i));
        assert!(!case_eq(upper_dotless_i, lower_dotted_i));
        assert!(!case_eq(lower_dotless_i, upper_dotted_i));
        assert!(!case_eq(lower_dotless_i, lower_dotted_i));
        assert!(!case_eq(upper_dotted_i, upper_dotless_i));
        assert!(!case_eq(upper_dotted_i, lower_dotless_i));
        assert!(!case_eq(lower_dotted_i, upper_dotless_i));
        assert!(!case_eq(lower_dotted_i, lower_dotless_i));

        assert_ne!(casecmp(upper_dotless_i, upper_dotted_i), Ordering::Equal);
        assert_ne!(casecmp(upper_dotless_i, lower_dotted_i), Ordering::Equal);
        assert_ne!(casecmp(lower_dotless_i, upper_dotted_i), Ordering::Equal);
        assert_ne!(casecmp(lower_dotless_i, lower_dotted_i), Ordering::Equal);
        assert_ne!(casecmp(upper_dotted_i, upper_dotless_i), Ordering::Equal);
        assert_ne!(casecmp(upper_dotted_i, lower_dotless_i), Ordering::Equal);
        assert_ne!(casecmp(lower_dotted_i, upper_dotless_i), Ordering::Equal);
        assert_ne!(casecmp(lower_dotted_i, lower_dotless_i), Ordering::Equal);
    }
}