/* Copyright (C) 2022-2024 José Rebelo
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This file is part of Gadgetbridge.
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Gadgetbridge is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as published
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by the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Gadgetbridge is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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package nodomain.freeyourgadget.gadgetbridge.util.language.impl;
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import java.text.Normalizer;
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import java.util.Optional;
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import nodomain.freeyourgadget.gadgetbridge.util.language.Transliterator;
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// Implements Revised Romanization of Korean as well as we can without understanding any grammar.
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//
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// https://en.wikipedia.org/wiki/Revised_Romanization_of_Korean
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public class KoreanTransliterator implements Transliterator {
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// https://en.wikipedia.org/wiki/Hangul_Jamo_%28Unicode_block%29
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private static final char JAMO_BLOCK_START = 0x1100;
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private static final char JAMO_BLOCK_END = 0x11FF;
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// https://en.wikipedia.org/wiki/Hangul_Syllables
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private static final char SYLLABLES_BLOCK_START = 0xAC00;
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private static final char SYLLABLES_BLOCK_END = 0xD7A3;
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// https://en.wikipedia.org/wiki/Hangul_Compatibility_Jamo
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private static final char COMPAT_JAMO_BLOCK_START = 0x3131;
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private static final char COMPAT_JAMO_BLOCK_END = 0x318E;
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// Returns whether a char is in the given block. Both bounds are inclusive.
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private static boolean inRange(char c, char start, char end) {
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return c >= start && c <= end;
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}
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// User input consisting of isolated jamo is usually mapped to the KS X 1001 compatibility
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// block, but jamo resulting from decomposed syllables are mapped to the modern one. This
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// function maps compat jamo to modern ones where possible and returns all other characters
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// unmodified.
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//
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// https://en.wikipedia.org/wiki/Hangul_Compatibility_Jamo
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// https://en.wikipedia.org/wiki/Hangul_Jamo_%28Unicode_block%29
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private static char decompatJamo(char jamo) {
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// KS X 1001 Hangul filler, not used in modern Unicode. A useful landmark in the
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// compatibility jamo block.
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// https://en.wikipedia.org/wiki/KS_X_1001#Hangul_Filler
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final char HANGUL_FILLER = 0x3164;
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// Don't do anything to characters outside the compatibility jamo block.
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if (!inRange(jamo, COMPAT_JAMO_BLOCK_START, COMPAT_JAMO_BLOCK_END)) { return jamo; }
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// Vowels are contiguous, in the same order, and unambiguous, so it's a simple offset.
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if (jamo >= 0x314F && jamo < HANGUL_FILLER) {
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return (char)(jamo - 0x1FEE);
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}
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// Consonants are organized differently. No clean way to do this.
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//
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// The compatibility jamo block doesn't distinguish between Choseong (leading) and Jongseong
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// (final) positions, but the modern block does. We map to Choseong here.
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switch (jamo) {
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case 0x3131: return 0x1100; // ㄱ
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case 0x3132: return 0x1101; // ㄲ
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case 0x3134: return 0x1102; // ㄴ
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case 0x3137: return 0x1103; // ㄷ
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case 0x3138: return 0x1104; // ㄸ
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case 0x3139: return 0x1105; // ㄹ
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case 0x3141: return 0x1106; // ㅁ
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case 0x3142: return 0x1107; // ㅂ
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case 0x3143: return 0x1108; // ㅃ
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case 0x3145: return 0x1109; // ㅅ
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case 0x3146: return 0x110A; // ㅆ
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case 0x3147: return 0x110B; // ㅇ
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case 0x3148: return 0x110C; // ㅈ
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case 0x3149: return 0x110D; // ㅉ
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case 0x314A: return 0x110E; // ㅊ
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case 0x314B: return 0x110F; // ㅋ
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case 0x314C: return 0x1110; // ㅌ
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case 0x314D: return 0x1111; // ㅍ
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case 0x314E: return 0x1112; // ㅎ
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}
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// The rest of the compatibility block consists of archaic compounds that are unlikely to be
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// encountered in modern systems. Just leave them alone.
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return jamo;
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}
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// Transliterates jamo one at a time. Returns its input if it isn't in the modern jamo block.
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private static String transliterateSingleJamo(char jamo) {
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jamo = decompatJamo(jamo);
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switch (jamo) {
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// Choseong (leading position consonants)
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case 0x1100: return "g"; // ㄱ
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case 0x1101: return "kk"; // ㄲ
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case 0x1102: return "n"; // ㄴ
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case 0x1103: return "d"; // ㄷ
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case 0x1104: return "tt"; // ㄸ
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case 0x1105: return "r"; // ㄹ
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case 0x1106: return "m"; // ㅁ
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case 0x1107: return "b"; // ㅂ
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case 0x1108: return "pp"; // ㅃ
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case 0x1109: return "s"; // ㅅ
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case 0x110A: return "ss"; // ㅆ
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case 0x110B: return ""; // ㅇ
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case 0x110C: return "j"; // ㅈ
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case 0x110D: return "jj"; // ㅉ
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case 0x110E: return "ch"; // ㅊ
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case 0x110F: return "k"; // ㅋ
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case 0x1110: return "t"; // ㅌ
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case 0x1111: return "p"; // ㅍ
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case 0x1112: return "h"; // ㅎ
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// Jungseong (vowels)
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case 0x1161: return "a"; // ㅏ
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case 0x1162: return "ae"; // ㅐ
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case 0x1163: return "ya"; // ㅑ
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case 0x1164: return "yae"; // ㅒ
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case 0x1165: return "eo"; // ㅓ
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case 0x1166: return "e"; // ㅔ
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case 0x1167: return "yeo"; // ㅕ
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case 0x1168: return "ye"; // ㅖ
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case 0x1169: return "o"; // ㅗ
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case 0x116A: return "wa"; // ㅘ
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case 0x116B: return "wae"; // ㅙ
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case 0x116C: return "oe"; // ㅚ
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case 0x116D: return "yo"; // ㅛ
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case 0x116E: return "u"; // ㅜ
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case 0x116F: return "wo"; // ㅝ
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case 0x1170: return "we"; // ㅞ
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case 0x1171: return "wi"; // ㅟ
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case 0x1172: return "yu"; // ㅠ
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case 0x1173: return "eu"; // ㅡ
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case 0x1174: return "ui"; // ㅢ
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case 0x1175: return "i"; // ㅣ
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// Jongseong (final position consonants)
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case 0x11A8: return "k"; // ㄱ
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case 0x11A9: return "k"; // ㄲ
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case 0x11AB: return "n"; // ㄴ
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case 0x11AE: return "t"; // ㄷ
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case 0x11AF: return "l"; // ㄹ
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case 0x11B7: return "m"; // ㅁ
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case 0x11B8: return "p"; // ㅂ
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case 0x11BA: return "t"; // ㅅ
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case 0x11BB: return "t"; // ㅆ
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case 0x11BC: return "ng"; // ㅇ
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case 0x11BD: return "t"; // ㅈ
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case 0x11BE: return "t"; // ㅊ
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case 0x11BF: return "k"; // ㅋ
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case 0x11C0: return "t"; // ㅌ
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case 0x11C1: return "p"; // ㅍ
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case 0x11C2: return "t"; // ㅎ
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}
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// Input was not jamo.
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return String.valueOf(jamo);
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}
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// Some combinations of ending jamo in one syllable and initial jamo in the next are romanized
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// irregularly. These exceptions are called "special provisions". In cases where multiple
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// romanizations are permitted, we use the one that's least commonly used elsewhere.
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//
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// Returns no value if either character is not in the modern jamo block, or if there is no
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// special provision for that pair of jamo.
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public static Optional<String> transliterateSpecialProvisions(char previousEnding, char nextInitial) {
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// Special provisions only apply if both characters are in the modern jamo block.
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if (!inRange(previousEnding, JAMO_BLOCK_START, JAMO_BLOCK_END)) { return Optional.empty(); }
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if (!inRange(nextInitial, JAMO_BLOCK_START, JAMO_BLOCK_END)) { return Optional.empty(); }
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// Jongseong (final position) ㅎ has a number of special provisions.
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if (previousEnding == 0x11C2) { // ㅎ
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switch (nextInitial) {
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case 0x110B: return Optional.of("h"); // ㅇ
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case 0x1100: return Optional.of("k"); // ㄱ
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case 0x1102: return Optional.of("nn"); // ㄴ
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case 0x1103: return Optional.of("t"); // ㄷ
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case 0x1105: return Optional.of("nn"); // ㄹ
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case 0x1106: return Optional.of("nm"); // ㅁ
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case 0x1107: return Optional.of("p"); // ㅂ
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case 0x1109: return Optional.of("hs"); // ㅅ
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case 0x110C: return Optional.of("ch"); // ㅈ
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case 0x1112: return Optional.of("t"); // ㅎ
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default: return Optional.empty();
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}
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}
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// Otherwise, special provisions are denser when grouped by the second jamo.
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switch (nextInitial) {
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case 0x1100: // ㄱ
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switch (previousEnding) {
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case 0x11AB: return Optional.of("n-g"); // ㄴ
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default: return Optional.empty();
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}
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case 0x1102: // ㄴ
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switch (previousEnding) {
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case 0x11A8: return Optional.of("ngn"); // ㄱ
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case 0x11AE: // ㄷ
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case 0x11BA: // ㅅ
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case 0x11BD: // ㅈ
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case 0x11BE: // ㅊ
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case 0x11C0: // ㅌ
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return Optional.of("nn");
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case 0x11AF: return Optional.of("ll"); // ㄹ
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case 0x11B8: return Optional.of("mn"); // ㅂ
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default: return Optional.empty();
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}
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case 0x1105: // ㄹ
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switch (previousEnding) {
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case 0x11A8: // ㄱ
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case 0x11AB: // ㄴ
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case 0x11AF: // ㄹ
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return Optional.of("ll");
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case 0x11AE: // ㄷ
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case 0x11BA: // ㅅ
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case 0x11BD: // ㅈ
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case 0x11BE: // ㅊ
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case 0x11C0: // ㅌ
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return Optional.of("nn");
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case 0x11B7: // ㅁ
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case 0x11B8: // ㅂ
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return Optional.of("mn");
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case 0x11BC: return Optional.of("ngn"); // ㅇ
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default: return Optional.empty();
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}
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case 0x1106: // ㅁ
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switch (previousEnding) {
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case 0x11A8: return Optional.of("ngm"); // ㄱ
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case 0x11AE: // ㄷ
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case 0x11BA: // ㅅ
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case 0x11BD: // ㅈ
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case 0x11BE: // ㅊ
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case 0x11C0: // ㅌ
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return Optional.of("nm");
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case 0x11B8: return Optional.of("mm"); // ㅂ
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default: return Optional.empty();
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}
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case 0x110B: // ㅇ
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switch (previousEnding) {
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case 0x11A8: return Optional.of("g"); // ㄱ
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case 0x11AE: return Optional.of("d"); // ㄷ
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case 0x11AF: return Optional.of("r"); // ㄹ
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case 0x11B8: return Optional.of("b"); // ㅂ
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case 0x11BA: return Optional.of("s"); // ㅅ
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case 0x11BC: return Optional.of("ng-"); // ㅇ
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case 0x11BD: return Optional.of("j"); // ㅈ
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case 0x11BE: return Optional.of("ch"); // ㅊ
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default: return Optional.empty();
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}
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case 0x110F: // ㅋ
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switch (previousEnding) {
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case 0x11A8: return Optional.of("k-k"); // ㄱ
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default: return Optional.empty();
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}
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case 0x1110: // ㅌ
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switch (previousEnding) {
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case 0x11AE: // ㄷ
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case 0x11BA: // ㅅ
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case 0x11BD: // ㅈ
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case 0x11BE: // ㅊ
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case 0x11C0: // ㅌ
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return Optional.of("t-t");
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default: return Optional.empty();
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}
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case 0x1111: // ㅍ
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switch (previousEnding) {
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case 0x11B8: return Optional.of("p-p"); // ㅂ
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default: return Optional.empty();
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}
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default: return Optional.empty();
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}
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}
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// Decompose a syllable into several jamo. Returns its input if that isn't possible.
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public static char[] decompose(char syllable) {
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String normalized = Normalizer.normalize(String.valueOf(syllable), Normalizer.Form.NFD);
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return normalized.toCharArray();
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}
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// Transliterate any Hangul in the given string. Leaves any non-Hangul characters unmodified.
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@Override
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public String transliterate(String txt) {
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if (txt == null || txt.isEmpty()) {
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return txt;
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}
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// Most of the bulk of these loops is for handling special provisions - situations where the
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// last jamo of one syllable and the first of the next need to be romanized as a pair in an
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// irregular way.
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StringBuilder builder = new StringBuilder();
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boolean nextInitialJamoConsumed = false;
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char[] syllables = txt.toCharArray();
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for (int i = 0; i < syllables.length; i++) {
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char thisSyllable = syllables[i];
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// If this isn't in any of the Hangul blocks we know about, emit it as-is.
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if (!inRange(thisSyllable, JAMO_BLOCK_START, JAMO_BLOCK_END)
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&& !inRange(thisSyllable, SYLLABLES_BLOCK_START, SYLLABLES_BLOCK_END)
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&& !inRange(thisSyllable, COMPAT_JAMO_BLOCK_START, COMPAT_JAMO_BLOCK_END)) {
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builder.append(thisSyllable);
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continue;
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}
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char[] theseJamo = decompose(thisSyllable);
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for (int j = 0; j < theseJamo.length; j++) {
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char thisJamo = theseJamo[j];
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// If we already transliterated the first jamo of this syllable as part of a special
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// provision, skip it. Otherwise, handle it in the unconditional else branch.
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if (j == 0 && nextInitialJamoConsumed) {
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nextInitialJamoConsumed = false;
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continue;
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}
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// If this is the last jamo of this syllable and not the last syllable of the
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// string, check for special provisions. If the next char is whitespace or not
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// Hangul, it's the responsibility of transliterateSpecialProvisions() to return no
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// value.
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if (j == theseJamo.length - 1 && i < syllables.length - 1) {
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char nextSyllable = syllables[i + 1];
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char nextJamo = decompose(nextSyllable)[0];
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Optional<String> specialProvision = transliterateSpecialProvisions(thisJamo, nextJamo);
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if (specialProvision.isPresent()) {
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builder.append(specialProvision.get());
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nextInitialJamoConsumed = true;
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} else {
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// No special provision applies. Transliterate in isolation.
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builder.append(transliterateSingleJamo(thisJamo));
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}
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continue;
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}
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// Everything else is transliterated in isolation.
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builder.append(transliterateSingleJamo(thisJamo));
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}
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}
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return builder.toString();
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}
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}
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