LibUnicode: Add decomposition mappings and Unicode normalization

The mappings are exposed via `Unicode::code_point_decomposition(u32)`
and `Unicode::code_point_decompositions()`, the latter being useful for
reverse searching a code point from its decomposition.

The normalization code does not make use of `Quick_Check` props (https://www.unicode.org/reports/tr44/#Decompositions_and_Normalization),
meaning no quick check optimizations.

Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateUnicodeData.cpp

@@ -44,6 +44,14 @@ struct SpecialCasing {
     String condition;
 };
 
+// Field descriptions: https://www.unicode.org/reports/tr44/#Character_Decomposition_Mappings
+struct CodePointDecomposition {
+    // `tag` is a string since it's used for codegen as an enum value.
+    String tag { "Canonical"sv };
+    size_t decomposition_index { 0 };
+    size_t decomposition_size { 0 };
+};
+
 // PropList source: https://www.unicode.org/Public/13.0.0/ucd/PropList.txt
 // Property descriptions: https://www.unicode.org/reports/tr44/tr44-13.html#PropList.txt
 using PropList = HashMap<String, Vector<CodePointRange>>;
@@ -78,7 +86,7 @@ struct CodePointData {
     Optional<StringIndexType> abbreviation;
     u8 canonical_combining_class { 0 };
     String bidi_class;
-    String decomposition_type;
+    Optional<CodePointDecomposition> decomposition_mapping;
     Optional<i8> numeric_value_decimal;
     Optional<i8> numeric_value_digit;
     Optional<i8> numeric_value_numeric;
@@ -101,6 +109,10 @@ struct UnicodeData {
 
     u32 code_points_with_non_zero_combining_class { 0 };
 
+    u32 code_points_with_decomposition_mapping { 0 };
+    Vector<u32> decomposition_mappings;
+    Vector<String> compatibility_tags;
+
     u32 simple_uppercase_mapping_size { 0 };
     u32 simple_lowercase_mapping_size { 0 };
 
@@ -534,6 +546,35 @@ static void add_canonical_code_point_name(CodePointRange range, StringView name,
     unicode_data.code_point_display_names.append({ range, index });
 }
 
+static Optional<CodePointDecomposition> parse_decomposition_mapping(StringView string, UnicodeData& unicode_data)
+{
+    if (string.is_empty())
+        return {};
+
+    CodePointDecomposition mapping;
+
+    auto parts = string.split_view(' ');
+
+    VERIFY(parts.size() > 0);
+
+    if (parts.first().starts_with('<')) {
+        auto const tag = parts.take_first().trim("<>"sv);
+
+        mapping.tag = String::formatted("{:c}{}", to_ascii_uppercase(tag[0]), tag.substring_view(1));
+
+        if (!unicode_data.compatibility_tags.contains_slow(mapping.tag))
+            unicode_data.compatibility_tags.append(mapping.tag);
+    }
+
+    mapping.decomposition_index = unicode_data.decomposition_mappings.size();
+    mapping.decomposition_size = parts.size();
+    for (auto part : parts) {
+        unicode_data.decomposition_mappings.append(AK::StringUtils::convert_to_uint_from_hex<u32>(part).value());
+    }
+
+    return mapping;
+}
+
 static ErrorOr<void> parse_block_display_names(Core::Stream::BufferedFile& file, UnicodeData& unicode_data)
 {
     Array<u8, 1024> buffer;
@@ -581,7 +622,7 @@ static ErrorOr<void> parse_unicode_data(Core::Stream::BufferedFile& file, Unicod
         data.name = segments[1];
         data.canonical_combining_class = AK::StringUtils::convert_to_uint<u8>(segments[3]).value();
         data.bidi_class = segments[4];
-        data.decomposition_type = segments[5];
+        data.decomposition_mapping = parse_decomposition_mapping(segments[5], unicode_data);
         data.numeric_value_decimal = AK::StringUtils::convert_to_int<i8>(segments[6]);
         data.numeric_value_digit = AK::StringUtils::convert_to_int<i8>(segments[7]);
         data.numeric_value_numeric = AK::StringUtils::convert_to_int<i8>(segments[8]);
@@ -639,6 +680,7 @@ static ErrorOr<void> parse_unicode_data(Core::Stream::BufferedFile& file, Unicod
         unicode_data.code_points_with_non_zero_combining_class += data.canonical_combining_class != 0;
         unicode_data.simple_uppercase_mapping_size += data.simple_uppercase_mapping.has_value();
         unicode_data.simple_lowercase_mapping_size += data.simple_lowercase_mapping.has_value();
+        unicode_data.code_points_with_decomposition_mapping += data.decomposition_mapping.has_value();
 
         unicode_data.code_points_with_special_casing += has_special_casing;
         unicode_data.largest_special_casing_size = max(unicode_data.largest_special_casing_size, data.special_casing_indices.size());
@@ -714,6 +756,7 @@ namespace Unicode {
     generate_enum("GraphemeBreakProperty"sv, {}, unicode_data.grapheme_break_props.keys());
     generate_enum("WordBreakProperty"sv, {}, unicode_data.word_break_props.keys());
     generate_enum("SentenceBreakProperty"sv, {}, unicode_data.sentence_break_props.keys());
+    generate_enum("CompatibilityFormattingTag"sv, "Canonical"sv, unicode_data.compatibility_tags);
 
     generator.append(R"~~~(
 struct SpecialCasing {
@@ -732,6 +775,12 @@ struct SpecialCasing {
     Condition condition { Condition::None };
 };
 
+struct CodePointDecomposition {
+    u32 code_point { 0 };
+    CompatibilityFormattingTag tag { CompatibilityFormattingTag::Canonical };
+    Span<u32 const> decomposition;
+};
+
 Optional<Locale> locale_from_string(StringView locale);
 
 }
@@ -760,6 +809,7 @@ static ErrorOr<void> generate_unicode_data_implementation(Core::Stream::Buffered
 #include <AK/StringView.h>
 #include <LibUnicode/CharacterTypes.h>
 #include <LibUnicode/UnicodeData.h>
+#include <LibUnicode/Normalize.h>
 
 namespace Unicode {
 )~~~");
@@ -863,6 +913,11 @@ struct CodePointNameComparator : public CodePointRangeComparator {
 };
 )~~~");
 
+    generator.set("decomposition_mappings_size", String::number(unicode_data.decomposition_mappings.size()));
+    generator.append("\nstatic constexpr Array<u32, @decomposition_mappings_size@> s_decomposition_mappings_data { ");
+    generator.append(String::join(", "sv, unicode_data.decomposition_mappings, "{:#x}"sv));
+    generator.append(" };\n");
+
     auto append_code_point_mappings = [&](StringView name, StringView mapping_type, u32 size, auto mapping_getter) {
         generator.set("name", name);
         generator.set("mapping_type", mapping_type);
@@ -895,6 +950,11 @@ static constexpr Array<@mapping_type@, @size@> s_@name@_mappings { {
             if constexpr (IsSame<decltype(mapping), Optional<u32>> || IsSame<decltype(mapping), Optional<StringIndexType>>) {
                 generator.set("mapping", String::formatted("{:#x}", *mapping));
                 generator.append(", @mapping@ },");
+            } else if constexpr (IsSame<decltype(mapping), Optional<CodePointDecomposition>>) {
+                generator.set("tag", mapping->tag);
+                generator.set("start", String::number(mapping->decomposition_index));
+                generator.set("size", String::number(mapping->decomposition_size));
+                generator.append(", CompatibilityFormattingTag::@tag@, Span<u32 const> { s_decomposition_mappings_data.data() + @start@, @size@ } },");
             } else {
                 append_list_and_size(data.special_casing_indices, "&s_special_casing[{}]"sv);
                 generator.append(" },");
@@ -921,6 +981,11 @@ static constexpr Array<@mapping_type@, @size@> s_@name@_mappings { {
     append_code_point_mappings("special_case"sv, "SpecialCaseMapping"sv, unicode_data.code_points_with_special_casing, [](auto const& data) { return data.special_casing_indices; });
     append_code_point_mappings("abbreviation"sv, "CodePointAbbreviation"sv, unicode_data.code_point_abbreviations.size(), [](auto const& data) { return data.abbreviation; });
 
+    append_code_point_mappings("decomposition"sv, "CodePointDecomposition"sv, unicode_data.code_points_with_decomposition_mapping,
+        [](auto const& data) {
+            return data.decomposition_mapping;
+        });
+
     auto append_code_point_range_list = [&](String name, Vector<CodePointRange> const& ranges) {
         generator.set("name", name);
         generator.set("size", String::number(ranges.size()));
@@ -1094,6 +1159,19 @@ Optional<StringView> code_point_abbreviation(u32 code_point)
 
     return decode_string(mapping->abbreviation);
 }
+
+Optional<CodePointDecomposition const&> code_point_decomposition(u32 code_point)
+{
+    auto const* mapping = binary_search(s_decomposition_mappings, code_point, nullptr, CodePointComparator<CodePointDecomposition> {});
+    if (mapping == nullptr)
+        return {};
+    return *mapping;
+}
+
+Span<CodePointDecomposition const> code_point_decompositions()
+{
+    return s_decomposition_mappings;
+}
 )~~~");
 
     auto append_prop_search = [&](StringView enum_title, StringView enum_snake, StringView collection_name) {

Userland/Libraries/LibUnicode/CMakeLists.txt

@@ -4,6 +4,7 @@ set(SOURCES
     CharacterTypes.cpp
     CurrencyCode.cpp
     Emoji.cpp
+    Normalize.cpp
     ${UNICODE_DATA_SOURCES}
 )
 

Userland/Libraries/LibUnicode/Forward.h

@@ -19,6 +19,7 @@ enum class Script : u8;
 enum class SentenceBreakProperty : u8;
 enum class WordBreakProperty : u8;
 
+struct CodePointDecomposition;
 struct CurrencyCode;
 struct Emoji;
 struct SpecialCasing;

Userland/Libraries/LibUnicode/Normalize.cpp

@@ -0,0 +1,280 @@
+/*
+ * Copyright (c) 2022, mat
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Find.h>
+#include <AK/QuickSort.h>
+#include <AK/Utf8View.h>
+#include <AK/Vector.h>
+#include <LibUnicode/CharacterTypes.h>
+#include <LibUnicode/Normalize.h>
+#include <LibUnicode/UnicodeData.h>
+
+namespace Unicode {
+
+Optional<CodePointDecomposition const&> __attribute__((weak)) code_point_decomposition(u32) { return {}; }
+Span<CodePointDecomposition const> __attribute__((weak)) code_point_decompositions() { return {}; }
+
+ALWAYS_INLINE static bool is_starter(u32 code_point)
+{
+    return Unicode::canonical_combining_class(code_point) == 0;
+}
+
+// From https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G56669
+static constexpr u32 HANGUL_SYLLABLE_BASE = 0xAC00;
+static constexpr u32 HANGUL_LEADING_BASE = 0x1100;
+static constexpr u32 HANGUL_VOWEL_BASE = 0x1161;
+static constexpr u32 HANGUL_TRAILING_BASE = 0x11A7;
+static constexpr u32 HANGUL_LEADING_COUNT = 19;
+static constexpr u32 HANGUL_VOWEL_COUNT = 21;
+static constexpr u32 HANGUL_TRAILING_COUNT = 28;
+// NCount in the standard.
+static constexpr u32 HANGUL_BLOCK_COUNT = HANGUL_VOWEL_COUNT * HANGUL_TRAILING_COUNT;
+static constexpr u32 HANGUL_SYLLABLE_COUNT = HANGUL_LEADING_COUNT * HANGUL_BLOCK_COUNT;
+
+ALWAYS_INLINE static bool is_hangul_code_point(u32 code_point)
+{
+    return code_point >= HANGUL_SYLLABLE_BASE && code_point < HANGUL_SYLLABLE_BASE + HANGUL_SYLLABLE_COUNT;
+}
+
+ALWAYS_INLINE static bool is_hangul_leading(u32 code_point)
+{
+    return code_point >= HANGUL_LEADING_BASE && code_point < HANGUL_LEADING_BASE + HANGUL_LEADING_COUNT;
+}
+
+ALWAYS_INLINE static bool is_hangul_vowel(u32 code_point)
+{
+    return code_point >= HANGUL_VOWEL_BASE && code_point < HANGUL_VOWEL_BASE + HANGUL_VOWEL_COUNT;
+}
+
+ALWAYS_INLINE static bool is_hangul_trailing(u32 code_point)
+{
+    return code_point >= HANGUL_TRAILING_BASE && code_point < HANGUL_TRAILING_BASE + HANGUL_TRAILING_COUNT;
+}
+
+// https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G56669
+static void decompose_hangul_code_point(u32 code_point, Vector<u32>& code_points_output)
+{
+    auto const index = code_point - HANGUL_SYLLABLE_BASE;
+
+    auto const leading_index = index / HANGUL_BLOCK_COUNT;
+    auto const vowel_index = (index % HANGUL_BLOCK_COUNT) / HANGUL_TRAILING_COUNT;
+    auto const trailing_index = index % HANGUL_TRAILING_COUNT;
+
+    auto const leading_part = HANGUL_LEADING_BASE + leading_index;
+    auto const vowel_part = HANGUL_VOWEL_BASE + vowel_index;
+    auto const trailing_part = HANGUL_TRAILING_BASE + trailing_index;
+
+    code_points_output.append(leading_part);
+    code_points_output.append(vowel_part);
+    if (trailing_index != 0)
+        code_points_output.append(trailing_part);
+}
+
+// L, V and LV, T Hangul Syllable Composition
+// https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G59688
+static u32 combine_hangul_code_points(u32 a, u32 b)
+{
+    if (is_hangul_leading(a) && is_hangul_vowel(b)) {
+        auto const leading_index = a - HANGUL_LEADING_BASE;
+        auto const vowel_index = b - HANGUL_VOWEL_BASE;
+        auto const leading_vowel_index = leading_index * HANGUL_BLOCK_COUNT + vowel_index * HANGUL_TRAILING_COUNT;
+        return HANGUL_SYLLABLE_BASE + leading_vowel_index;
+    }
+    if (is_hangul_code_point(a) && is_hangul_trailing(b)) {
+        return a + b - HANGUL_TRAILING_BASE;
+    }
+    return 0;
+}
+
+static u32 combine_code_points(u32 a, u32 b)
+{
+    Array<u32, 2> const points { a, b };
+    // FIXME: Do something better than linear search to find reverse mappings.
+    for (auto const& mapping : Unicode::code_point_decompositions()) {
+        if (mapping.tag == CompatibilityFormattingTag::Canonical && mapping.decomposition == points) {
+            if (code_point_has_property(mapping.code_point, Property::Full_Composition_Exclusion))
+                continue;
+            return mapping.code_point;
+        }
+    }
+    return 0;
+}
+
+enum class UseCompatibility {
+    Yes,
+    No
+};
+
+static void decompose_code_point(u32 code_point, Vector<u32>& code_points_output, UseCompatibility use_compatibility)
+{
+    if (is_hangul_code_point(code_point)) {
+        decompose_hangul_code_point(code_point, code_points_output);
+        return;
+    }
+    auto const mapping = Unicode::code_point_decomposition(code_point);
+    if (mapping.has_value() && (mapping->tag == CompatibilityFormattingTag::Canonical || use_compatibility == UseCompatibility::Yes)) {
+        for (auto code_point : mapping->decomposition) {
+            decompose_code_point(code_point, code_points_output, use_compatibility);
+        }
+    } else {
+        code_points_output.append(code_point);
+    }
+}
+
+// This can be any sorting algorithm that maintains order (like std::stable_sort),
+// however bubble sort is easier to implement, so go with it (for now).
+template<typename T, typename LessThan>
+void bubble_sort(Span<T> span, LessThan less_than)
+{
+    for (size_t i = 0; i < span.size() - 1; ++i) {
+        for (size_t j = 0; j < span.size() - 1 - i; ++j) {
+            if (!less_than(span[j], span[j + 1]))
+                swap(span[j], span[j + 1]);
+        }
+    }
+}
+
+// The Canonical Ordering Algorithm, as specified in Version 15.0.0 of the Unicode Standard.
+// See Section 3.11, D109; and UAX #15 https://unicode.org/reports/tr15
+// https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G49591
+static void canonical_ordering_algorithm(Span<u32> code_points)
+{
+    for (size_t i = 0; i < code_points.size(); ++i) {
+        if (!is_starter(code_points[i])) {
+            auto starter = find_if(code_points.begin() + i, code_points.end(), is_starter);
+            auto const span_size = static_cast<size_t>(starter - (code_points.begin() + i));
+            // Nothing to reorder, so continue.
+            if (span_size <= 1)
+                continue;
+            Span<u32> const span { code_points.data() + i, span_size };
+
+            bubble_sort(span, [](u32 a, u32 b) {
+                // Use <= to keep ordering.
+                return Unicode::canonical_combining_class(a) <= Unicode::canonical_combining_class(b);
+            });
+
+            // Skip over span we just sorted.
+            i += span_size - 1;
+        }
+    }
+}
+
+// See Section 3.11, D115 of Version 15.0.0 of the Unicode Standard.
+static bool is_blocked(Span<u32> code_points, size_t a, size_t c)
+{
+    if (!is_starter(code_points[a]) || a == c - 1)
+        return false;
+    auto const c_combining_class = Unicode::canonical_combining_class(code_points[c]);
+    auto const b_combining_class = Unicode::canonical_combining_class(code_points[c - 1]);
+    return b_combining_class == 0 || b_combining_class >= c_combining_class;
+}
+
+// The Canonical Composition Algorithm, as specified in Version 15.0.0 of the Unicode Standard.
+// See Section 3.11, D117; and UAX #15 https://unicode.org/reports/tr15
+// https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G50628
+static void canonical_composition_algorithm(Vector<u32>& code_points)
+{
+    for (size_t i = 1; i < code_points.size(); ++i) {
+        auto const current_character = code_points[i];
+        // R1. Seek back (left) to find the last Starter L preceding C in the character sequence
+        for (ssize_t j = i - 1; j >= 0; --j) {
+            if (!is_starter(code_points[j]))
+                continue;
+            // R2. If there is such an L, and C is not blocked from L,
+            //     and there exists a Primary Composite P which is canonically equivalent to <L, C>,
+            //     then replace L by P in the sequence and delete C from the sequence.
+            if (is_blocked(code_points.span(), j, i))
+                continue;
+
+            auto composite = combine_hangul_code_points(code_points[j], current_character);
+
+            if (composite == 0)
+                composite = combine_code_points(code_points[j], current_character);
+
+            if (composite != 0) {
+                code_points[j] = composite;
+                code_points.remove(i);
+                --i;
+                break;
+            }
+        }
+    }
+}
+
+static Vector<u32> normalize_nfd(Utf8View string)
+{
+    Vector<u32> result;
+
+    for (auto const code_point : string) {
+        decompose_code_point(code_point, result, UseCompatibility::No);
+    }
+
+    canonical_ordering_algorithm(result);
+
+    return result;
+}
+
+static Vector<u32> normalize_nfc(Utf8View string)
+{
+    auto result = normalize_nfd(string);
+
+    canonical_composition_algorithm(result);
+
+    return result;
+}
+
+static Vector<u32> normalize_nfkd(Utf8View string)
+{
+    Vector<u32> result;
+
+    for (auto const code_point : string) {
+        decompose_code_point(code_point, result, UseCompatibility::Yes);
+    }
+
+    canonical_ordering_algorithm(result);
+
+    return result;
+}
+
+static Vector<u32> normalize_nfkc(Utf8View string)
+{
+    auto result = normalize_nfkd(string);
+
+    canonical_composition_algorithm(result);
+
+    return result;
+}
+
+static Vector<u32> normalize_implementation(Utf8View string, NormalizationForm form)
+{
+    switch (form) {
+    case NormalizationForm::NFD:
+        return normalize_nfd(string);
+    case NormalizationForm::NFC:
+        return normalize_nfc(string);
+    case NormalizationForm::NFKD:
+        return normalize_nfkd(string);
+    case NormalizationForm::NFKC:
+        return normalize_nfkc(string);
+    }
+    VERIFY_NOT_REACHED();
+}
+
+String normalize(StringView string, NormalizationForm form)
+{
+    Utf8View const view { string };
+
+    auto const code_points = normalize_implementation(view, form);
+
+    StringBuilder builder;
+    for (auto code_point : code_points) {
+        builder.append_code_point(code_point);
+    }
+
+    return builder.to_string();
+}
+
+}

Userland/Libraries/LibUnicode/Normalize.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2022, mat
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <AK/Optional.h>
+#include <AK/Span.h>
+#include <AK/String.h>
+#include <AK/StringView.h>
+#include <LibUnicode/Forward.h>
+
+namespace Unicode {
+
+Optional<CodePointDecomposition const&> code_point_decomposition(u32 code_point);
+Span<CodePointDecomposition const> code_point_decompositions();
+
+enum class NormalizationForm {
+    NFD,
+    NFC,
+    NFKD,
+    NFKC
+};
+
+[[nodiscard]] String normalize(StringView string, NormalizationForm form);
+
+}