matcher_rs 0.15.5

//! Unicode normalization replacement via page-table lookup + fused streaming
//! scan.
//!
//! Data sourced from `unicodedata.normalize("NFKC", ch).casefold()`. All 8,633
//! keys are single Unicode codepoints (verified at build time). Cannot use
//! [`skip_ascii_simd`](super::simd::skip_ascii_simd) because A–Z have casefold
//! mappings; ASCII bytes are checked inline instead.
//!
//! Provides two consumption modes: materialized
//! [`replace`](NormalizeMatcher::replace) (allocates a `String`) and streaming
//! [`filter_bytes`](NormalizeMatcher::filter_bytes) (yields bytes one at a time
//! for fused normalize-scan without allocation).

use std::borrow::Cow;

use super::{
    filter::{CodepointFilter, FilterAction, FilterIterator},
    page_table::{
        StrReplaceFindIter, decode_page_table, page_table_lookup, replace_spans, unpack_str_ref,
    },
};

// ---------------------------------------------------------------------------
// Streaming filter (for fused normalize-scan)
// ---------------------------------------------------------------------------

/// [`CodepointFilter`] for Unicode normalization.
///
/// Replaces uppercase ASCII letters and mapped non-ASCII codepoints with
/// their NFKC-casefolded forms via page-table lookup.
pub(crate) struct NormalizeFilter<'a> {
    l1: &'a [u16],
    l2: &'a [u32],
    strings: &'a str,
}

impl<'a> CodepointFilter<'a> for NormalizeFilter<'a> {
    #[inline(always)]
    fn filter_ascii(&self, byte: u8) -> FilterAction<'a> {
        if byte.is_ascii_uppercase()
            && let Some(value) = page_table_lookup(byte as u32, self.l1, self.l2)
            && let Some(s) = unpack_str_ref(value, self.strings)
        {
            FilterAction::ReplaceBytes(s.as_bytes())
        } else {
            FilterAction::Keep
        }
    }

    #[inline(always)]
    fn filter_codepoint(&self, cp: u32) -> FilterAction<'a> {
        if let Some(value) = page_table_lookup(cp, self.l1, self.l2)
            && let Some(s) = unpack_str_ref(value, self.strings)
        {
            FilterAction::ReplaceBytes(s.as_bytes())
        } else {
            FilterAction::Keep
        }
    }
}

// ---------------------------------------------------------------------------
// Matcher
// ---------------------------------------------------------------------------

/// Two-stage page-table matcher for Unicode normalization replacement.
///
/// L2 entries encode `(byte_offset << 8) | byte_length` into a shared string
/// buffer, same layout as [`super::romanize::RomanizeMatcher`].
#[derive(Clone)]
pub(crate) struct NormalizeMatcher {
    l1: Box<[u16]>,
    l2: Box<[u32]>,
    strings: Cow<'static, str>,
}

impl NormalizeMatcher {
    /// Returns a find iterator over normalizable codepoints in `text`.
    ///
    /// Uses `CHECK_ASCII = true` — uppercase A–Z have casefold mappings,
    /// so ASCII bytes must be checked individually (no SIMD skip).
    #[inline(always)]
    fn iter<'a>(&'a self, text: &'a str) -> StrReplaceFindIter<'a, true> {
        StrReplaceFindIter {
            l1: &self.l1,
            l2: &self.l2,
            strings: self.strings.as_ref(),
            text,
            byte_offset: 0,
        }
    }

    /// Replaces normalizable codepoints (including ASCII uppercase A–Z).
    ///
    /// Returns `None` when `text` contains no normalizable characters. The
    /// `bool` in the return tuple indicates whether the output is entirely
    /// ASCII.
    ///
    /// ```ignore
    /// let matcher = NormalizeMatcher::new(NORMALIZE_L1_BYTES, NORMALIZE_L2_BYTES, NORMALIZE_STR_BYTES);
    /// let result = matcher.replace("Hello WORLD").unwrap();
    /// assert_eq!(result, "hello world"); // casefold
    /// ```
    pub(crate) fn replace(&self, text: &str) -> Option<String> {
        replace_spans(text, self.iter(text))
    }

    /// Decodes L1/L2 page tables from build-time binary artifacts.
    pub(crate) fn new(l1: &'static [u8], l2: &'static [u8], strings: &'static str) -> Self {
        let (l1, l2) = decode_page_table(l1, l2);
        Self {
            l1,
            l2,
            strings: Cow::Borrowed(strings),
        }
    }

    /// Returns a streaming byte iterator over the normalized form of `text`.
    ///
    /// Used by the fused normalize-scan path to feed normalized bytes directly
    /// into the Aho-Corasick automaton without materializing the full string.
    #[inline(always)]
    pub(crate) fn filter_bytes<'a>(
        &'a self,
        text: &'a str,
    ) -> FilterIterator<'a, NormalizeFilter<'a>> {
        FilterIterator::new(
            text,
            NormalizeFilter {
                l1: &self.l1,
                l2: &self.l2,
                strings: self.strings.as_ref(),
            },
        )
    }
}