//! Full Unicode case folding (`CaseFolding.txt` statuses `C` + `F`, Unicode
//! 17.0.0), equivalent to uucode's `case_folding_full` field.
//!
//! The table is generated by `build.rs` from `ucd/CaseFolding.txt`.

include!(concat!(env!("OUT_DIR"), "/case_folding_full.rs"));

/// The full case folding of `cp`, or `None` if it folds to itself.
///
/// The result has 1 to 3 codepoints (unused trailing entries are `0`); use
/// [`fold_full`] for a slice.
#[must_use]
pub fn lookup(cp: u32) -> Option<[u32; 3]> {
    CASE_FOLDING_FULL
        .binary_search_by_key(&cp, |e| e.0)
        .ok()
        .map(|i| CASE_FOLDING_FULL[i].1)
}

/// The full case folding of `cp` as a zero-padded 3-element array. Like
/// uucode's `.with(&buffer, cp)`, a codepoint without a folding folds to
/// itself.
#[must_use]
pub fn fold_full(cp: u32) -> [u32; 3] {
    lookup(cp).unwrap_or([cp, 0, 0])
}

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

    #[test]
    fn simple_and_identity() {
        assert_eq!(fold_full('A' as u32), ['a' as u32, 0, 0]);
        assert_eq!(fold_full('a' as u32), ['a' as u32, 0, 0]);
        assert_eq!(fold_full('1' as u32), ['1' as u32, 0, 0]);
        assert_eq!(fold_full(0x00B5), [0x03BC, 0, 0]);
        assert_eq!(fold_full(0x017F), ['s' as u32, 0, 0]);
        assert_eq!(fold_full(0x03C2), [0x03C3, 0, 0]);
        assert_eq!(fold_full(0x1E9E), [0x73, 0x73, 0]);
    }

    #[test]
    fn multi_codepoint() {
        // U+00DF LATIN SMALL LETTER SHARP S -> "ss"
        assert_eq!(fold_full(0x00DF), [0x73, 0x73, 0]);
        // U+0390 -> 03B9 0308 0301
        assert_eq!(fold_full(0x0390), [0x03B9, 0x0308, 0x0301]);
        // U+FB03 LATIN SMALL LIGATURE FFI -> "ffi"
        assert_eq!(fold_full(0xFB03), [0x66, 0x66, 0x69]);
    }

    #[test]
    fn table_sorted_and_nonempty() {
        assert!(CASE_FOLDING_FULL.len() > 1500);
        assert!(CASE_FOLDING_FULL.windows(2).all(|w| w[0].0 < w[1].0));
    }

    #[test]
    fn dotted_capital_i_uses_full_folding() {
        assert_eq!(fold_full(0x0130), [0x69, 0x307, 0]); // F entry for dotted I
    }
}