perl-lexer 0.13.1

//! Unicode-aware identifier classification utilities.
//!
//! The lexer uses this module to decide whether characters may start or
//! continue Perl identifiers, combining Unicode XID checks with
//! Perl-specific allowances such as apostrophe package separators and emoji.
//! It also exposes lightweight counters used for profiling Unicode-heavy
//! corpora in tests and debugging.
use std::sync::atomic::{AtomicU64, Ordering};
use unicode_ident::{is_xid_continue, is_xid_start};

// Performance tracking for Unicode operations
static UNICODE_CHAR_CHECKS: AtomicU64 = AtomicU64::new(0);
static UNICODE_EMOJI_HITS: AtomicU64 = AtomicU64::new(0);

/// Get Unicode processing statistics for debugging
#[allow(dead_code)]
pub fn get_unicode_stats() -> (u64, u64) {
    (UNICODE_CHAR_CHECKS.load(Ordering::Relaxed), UNICODE_EMOJI_HITS.load(Ordering::Relaxed))
}

/// Reset Unicode processing statistics
#[allow(dead_code)]
pub fn reset_unicode_stats() {
    UNICODE_CHAR_CHECKS.store(0, Ordering::Relaxed);
    UNICODE_EMOJI_HITS.store(0, Ordering::Relaxed);
}

fn is_emoji_codepoint(ch_u32: u32) -> bool {
    matches!(ch_u32,
        0x1F000..=0x1F02F |  // Mahjong Tiles
        0x1F0A0..=0x1F0FF |  // Playing Cards
        0x1F100..=0x1F1FF |  // Enclosed Alphanumeric Supplement
        0x1F200..=0x1F2FF |  // Enclosed Ideographic Supplement
        0x1F300..=0x1F6FF |  // Miscellaneous Symbols and Pictographs (includes 🚀)
        0x1F700..=0x1F77F |  // Alchemical Symbols
        0x1F780..=0x1F7FF |  // Geometric Shapes Extended
        0x1F800..=0x1F8FF |  // Supplemental Arrows-C
        0x1F900..=0x1F9FF |  // Supplemental Symbols and Pictographs
        0x1FA00..=0x1FA6F |  // Chess Symbols
        0x1FA70..=0x1FAFF |  // Symbols and Pictographs Extended-A
        0x2600..=0x26FF |    // Miscellaneous Symbols (includes ♥)
        0x2700..=0x27BF      // Dingbats
    )
}

/// Check if a character can start a Perl identifier
pub fn is_perl_identifier_start(ch: char) -> bool {
    UNICODE_CHAR_CHECKS.fetch_add(1, Ordering::Relaxed);

    // Use unicode-ident for standard Unicode identifier characters
    // This covers most scripts and languages automatically
    if ch == '_' || is_xid_start(ch) {
        return true;
    }

    // Check additional Unicode blocks that Perl allows
    // but aren't included in XID_Start (primarily emoji)
    let is_emoji = is_emoji_codepoint(ch as u32);

    if is_emoji {
        UNICODE_EMOJI_HITS.fetch_add(1, Ordering::Relaxed);
    }

    is_emoji
}

/// Check if a character can continue a Perl identifier
pub fn is_perl_identifier_continue(ch: char) -> bool {
    // For continuation, we accept identifier start chars, XID_Continue chars,
    // the single quote (for old-style package separators like Foo'Bar),
    // and emoji continuation code points used by ZWJ grapheme sequences.
    is_perl_identifier_start(ch)
        || is_xid_continue(ch)
        || ch == '\''
        || matches!(
            ch as u32,
            // Unicode join controls used in emoji and script shaping.
            0x200C | 0x200D |
            // Standard variation selectors (e.g. U+FE0F) used to keep emoji presentation.
            0xFE00..=0xFE0F |
            // Fitzpatrick skin-tone modifiers.
            0x1F3FB..=0x1F3FF
        )
}

/// Validate Unicode string complexity for performance monitoring
/// Returns (`char_count`, `emoji_count`, `complex_char_count`)
#[allow(dead_code)]
pub fn analyze_unicode_complexity(text: &str) -> (usize, usize, usize) {
    let mut char_count = 0;
    let mut emoji_count = 0;
    let mut complex_char_count = 0;

    for ch in text.chars() {
        char_count += 1;

        // Count emojis and complex Unicode
        let ch_u32 = ch as u32;
        if is_emoji_codepoint(ch_u32) {
            emoji_count += 1;
        }

        // Count complex characters (surrogate pairs, combining marks, etc.)
        if ch_u32 > 0xFFFF || ch.len_utf8() > 2 {
            complex_char_count += 1;
        }
    }

    (char_count, emoji_count, complex_char_count)
}

#[cfg(test)]
mod tests {
    use super::{
        analyze_unicode_complexity, get_unicode_stats, is_perl_identifier_continue,
        is_perl_identifier_start, reset_unicode_stats,
    };

    #[test]
    fn identifier_start_accepts_ascii_xid_and_emoji() {
        reset_unicode_stats();

        assert!(is_perl_identifier_start('_'));
        assert!(is_perl_identifier_start('A'));
        assert!(is_perl_identifier_start('λ'));
        assert!(is_perl_identifier_start('🚀'));
        assert!(!is_perl_identifier_start('1'));

        let (checks, emoji_hits) = get_unicode_stats();
        assert_eq!(checks, 5);
        assert_eq!(emoji_hits, 1);
    }

    #[test]
    fn identifier_start_rejects_punctuation() {
        assert!(!is_perl_identifier_start('-'));
    }

    #[test]
    fn identifier_continue_accepts_joiners_selectors_and_modifiers() {
        assert!(is_perl_identifier_continue('\''));
        assert!(is_perl_identifier_continue('\u{200C}'));
        assert!(is_perl_identifier_continue('\u{200D}'));
        assert!(is_perl_identifier_continue('\u{FE0F}'));
        assert!(is_perl_identifier_continue('\u{1F3FB}'));
        assert!(is_perl_identifier_continue('\u{1F3FD}'));
        assert!(!is_perl_identifier_continue(' '));
        assert!(!is_perl_identifier_continue('-'));
    }

    #[test]
    fn analyze_complexity_counts_chars_emoji_and_non_bmp() {
        // a + lambda + rocket + FE0F variation selector
        let (char_count, emoji_count, complex_char_count) =
            analyze_unicode_complexity("aλ🚀\u{FE0F}");

        assert_eq!(char_count, 4);
        assert_eq!(emoji_count, 1);
        assert_eq!(complex_char_count, 2);
    }
}