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Gadgetbridge/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/KoreanLanguageUtils.java
2021-01-10 23:38:13 +01:00

343 lines
16 KiB
Java

/* Copyright (C) 2020-2021 Ted Stein
This file is part of Gadgetbridge.
Gadgetbridge is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published
by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Gadgetbridge is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
package nodomain.freeyourgadget.gadgetbridge.util;
import java.util.Optional;
import java.text.Normalizer;
import java.text.Normalizer.Form;
// Implements Revised Romanization of Korean as well as we can without understanding any grammar.
//
// https://en.wikipedia.org/wiki/Revised_Romanization_of_Korean
public class KoreanLanguageUtils {
// https://en.wikipedia.org/wiki/Hangul_Jamo_%28Unicode_block%29
private static final char JAMO_BLOCK_START = 0x1100;
private static final char JAMO_BLOCK_END = 0x11FF;
// https://en.wikipedia.org/wiki/Hangul_Syllables
private static final char SYLLABLES_BLOCK_START = 0xAC00;
private static final char SYLLABLES_BLOCK_END = 0xD7A3;
// https://en.wikipedia.org/wiki/Hangul_Compatibility_Jamo
private static final char COMPAT_JAMO_BLOCK_START = 0x3131;
private static final char COMPAT_JAMO_BLOCK_END = 0x318E;
// Returns whether a char is in the given block. Both bounds are inclusive.
private static boolean inRange(char c, char start, char end) {
return c >= start && c <= end;
}
// User input consisting of isolated jamo is usually mapped to the KS X 1001 compatibility
// block, but jamo resulting from decomposed syllables are mapped to the modern one. This
// function maps compat jamo to modern ones where possible and returns all other characters
// unmodified.
//
// https://en.wikipedia.org/wiki/Hangul_Compatibility_Jamo
// https://en.wikipedia.org/wiki/Hangul_Jamo_%28Unicode_block%29
private static char decompatJamo(char jamo) {
// KS X 1001 Hangul filler, not used in modern Unicode. A useful landmark in the
// compatibility jamo block.
// https://en.wikipedia.org/wiki/KS_X_1001#Hangul_Filler
final char HANGUL_FILLER = 0x3164;
// Don't do anything to characters outside the compatibility jamo block.
if (!inRange(jamo, COMPAT_JAMO_BLOCK_START, COMPAT_JAMO_BLOCK_END)) { return jamo; }
// Vowels are contiguous, in the same order, and unambiguous, so it's a simple offset.
if (jamo >= 0x314F && jamo < HANGUL_FILLER) {
return (char)(jamo - 0x1FEE);
}
// Consonants are organized differently. No clean way to do this.
//
// The compatibility jamo block doesn't distinguish between Choseong (leading) and Jongseong
// (final) positions, but the modern block does. We map to Choseong here.
switch (jamo) {
case 0x3131: return 0x1100; // ㄱ
case 0x3132: return 0x1101; // ㄲ
case 0x3134: return 0x1102; // ㄴ
case 0x3137: return 0x1103; // ㄷ
case 0x3138: return 0x1104; // ㄸ
case 0x3139: return 0x1105; // ㄹ
case 0x3141: return 0x1106; // ㅁ
case 0x3142: return 0x1107; // ㅂ
case 0x3143: return 0x1108; // ㅃ
case 0x3145: return 0x1109; // ㅅ
case 0x3146: return 0x110A; // ㅆ
case 0x3147: return 0x110B; // ㅇ
case 0x3148: return 0x110C; // ㅈ
case 0x3149: return 0x110D; // ㅉ
case 0x314A: return 0x110E; // ㅊ
case 0x314B: return 0x110F; // ㅋ
case 0x314C: return 0x1110; // ㅌ
case 0x314D: return 0x1111; // ㅍ
case 0x314E: return 0x1112; // ㅎ
}
// The rest of the compatibility block consists of archaic compounds that are unlikely to be
// encountered in modern systems. Just leave them alone.
return jamo;
}
// Transliterates jamo one at a time. Returns its input if it isn't in the modern jamo block.
private static String transliterateSingleJamo(char jamo) {
jamo = decompatJamo(jamo);
switch (jamo) {
// Choseong (leading position consonants)
case 0x1100: return "g"; // ㄱ
case 0x1101: return "kk"; // ㄲ
case 0x1102: return "n"; // ㄴ
case 0x1103: return "d"; // ㄷ
case 0x1104: return "tt"; // ㄸ
case 0x1105: return "r"; // ㄹ
case 0x1106: return "m"; // ㅁ
case 0x1107: return "b"; // ㅂ
case 0x1108: return "pp"; // ㅃ
case 0x1109: return "s"; // ㅅ
case 0x110A: return "ss"; // ㅆ
case 0x110B: return ""; // ㅇ
case 0x110C: return "j"; // ㅈ
case 0x110D: return "jj"; // ㅉ
case 0x110E: return "ch"; // ㅊ
case 0x110F: return "k"; // ㅋ
case 0x1110: return "t"; // ㅌ
case 0x1111: return "p"; // ㅍ
case 0x1112: return "h"; // ㅎ
// Jungseong (vowels)
case 0x1161: return "a"; // ㅏ
case 0x1162: return "ae"; // ㅐ
case 0x1163: return "ya"; // ㅑ
case 0x1164: return "yae"; // ㅒ
case 0x1165: return "eo"; // ㅓ
case 0x1166: return "e"; // ㅔ
case 0x1167: return "yeo"; // ㅕ
case 0x1168: return "ye"; // ㅖ
case 0x1169: return "o"; // ㅗ
case 0x116A: return "wa"; // ㅘ
case 0x116B: return "wae"; // ㅙ
case 0x116C: return "oe"; // ㅚ
case 0x116D: return "yo"; // ㅛ
case 0x116E: return "u"; // ㅜ
case 0x116F: return "wo"; // ㅝ
case 0x1170: return "we"; // ㅞ
case 0x1171: return "wi"; // ㅟ
case 0x1172: return "yu"; // ㅠ
case 0x1173: return "eu"; // ㅡ
case 0x1174: return "ui"; // ㅢ
case 0x1175: return "i"; // ㅣ
// Jongseong (final position consonants)
case 0x11A8: return "k"; // ㄱ
case 0x11A9: return "k"; // ㄲ
case 0x11AB: return "n"; // ㄴ
case 0x11AE: return "t"; // ㄷ
case 0x11AF: return "l"; // ㄹ
case 0x11B7: return "m"; // ㅁ
case 0x11B8: return "p"; // ㅂ
case 0x11BA: return "t"; // ㅅ
case 0x11BB: return "t"; // ㅆ
case 0x11BC: return "ng"; // ㅇ
case 0x11BD: return "t"; // ㅈ
case 0x11BE: return "t"; // ㅊ
case 0x11BF: return "k"; // ㅋ
case 0x11C0: return "t"; // ㅌ
case 0x11C1: return "p"; // ㅍ
case 0x11C2: return "t"; // ㅎ
}
// Input was not jamo.
return String.valueOf(jamo);
}
// Some combinations of ending jamo in one syllable and initial jamo in the next are romanized
// irregularly. These exceptions are called "special provisions". In cases where multiple
// romanizations are permitted, we use the one that's least commonly used elsewhere.
//
// Returns no value if either character is not in the modern jamo block, or if there is no
// special provision for that pair of jamo.
public static Optional<String> transliterateSpecialProvisions(char previousEnding, char nextInitial) {
// Special provisions only apply if both characters are in the modern jamo block.
if (!inRange(previousEnding, JAMO_BLOCK_START, JAMO_BLOCK_END)) { return Optional.empty(); }
if (!inRange(nextInitial, JAMO_BLOCK_START, JAMO_BLOCK_END)) { return Optional.empty(); }
// Jongseong (final position) ㅎ has a number of special provisions.
if (previousEnding == 0x11C2) { // ㅎ
switch (nextInitial) {
case 0x110B: return Optional.of("h"); // ㅇ
case 0x1100: return Optional.of("k"); // ㄱ
case 0x1102: return Optional.of("nn"); // ㄴ
case 0x1103: return Optional.of("t"); // ㄷ
case 0x1105: return Optional.of("nn"); // ㄹ
case 0x1106: return Optional.of("nm"); // ㅁ
case 0x1107: return Optional.of("p"); // ㅂ
case 0x1109: return Optional.of("hs"); // ㅅ
case 0x110C: return Optional.of("ch"); // ㅈ
case 0x1112: return Optional.of("t"); // ㅎ
default: return Optional.empty();
}
}
// Otherwise, special provisions are denser when grouped by the second jamo.
switch (nextInitial) {
case 0x1100: // ㄱ
switch (previousEnding) {
case 0x11AB: return Optional.of("n-g"); // ㄴ
default: return Optional.empty();
}
case 0x1102: // ㄴ
switch (previousEnding) {
case 0x11A8: return Optional.of("ngn"); // ㄱ
case 0x11AE: // ㄷ
case 0x11BA: // ㅅ
case 0x11BD: // ㅈ
case 0x11BE: // ㅊ
case 0x11C0: // ㅌ
return Optional.of("nn");
case 0x11AF: return Optional.of("ll"); // ㄹ
case 0x11B8: return Optional.of("mn"); // ㅂ
default: return Optional.empty();
}
case 0x1105: // ㄹ
switch (previousEnding) {
case 0x11A8: // ㄱ
case 0x11AB: // ㄴ
case 0x11AF: // ㄹ
return Optional.of("ll");
case 0x11AE: // ㄷ
case 0x11BA: // ㅅ
case 0x11BD: // ㅈ
case 0x11BE: // ㅊ
case 0x11C0: // ㅌ
return Optional.of("nn");
case 0x11B7: // ㅁ
case 0x11B8: // ㅂ
return Optional.of("mn");
case 0x11BC: return Optional.of("ngn"); // ㅇ
default: return Optional.empty();
}
case 0x1106: // ㅁ
switch (previousEnding) {
case 0x11A8: return Optional.of("ngm"); // ㄱ
case 0x11AE: // ㄷ
case 0x11BA: // ㅅ
case 0x11BD: // ㅈ
case 0x11BE: // ㅊ
case 0x11C0: // ㅌ
return Optional.of("nm");
case 0x11B8: return Optional.of("mm"); // ㅂ
default: return Optional.empty();
}
case 0x110B: // ㅇ
switch (previousEnding) {
case 0x11A8: return Optional.of("g"); // ㄱ
case 0x11AE: return Optional.of("d"); // ㄷ
case 0x11AF: return Optional.of("r"); // ㄹ
case 0x11B8: return Optional.of("b"); // ㅂ
case 0x11BA: return Optional.of("s"); // ㅅ
case 0x11BC: return Optional.of("ng-"); // ㅇ
case 0x11BD: return Optional.of("j"); // ㅈ
case 0x11BE: return Optional.of("ch"); // ㅊ
default: return Optional.empty();
}
case 0x110F: // ㅋ
switch (previousEnding) {
case 0x11A8: return Optional.of("k-k"); // ㄱ
default: return Optional.empty();
}
case 0x1110: // ㅌ
switch (previousEnding) {
case 0x11AE: // ㄷ
case 0x11BA: // ㅅ
case 0x11BD: // ㅈ
case 0x11BE: // ㅊ
case 0x11C0: // ㅌ
return Optional.of("t-t");
default: return Optional.empty();
}
case 0x1111: // ㅍ
switch (previousEnding) {
case 0x11B8: return Optional.of("p-p"); // ㅂ
default: return Optional.empty();
}
default: return Optional.empty();
}
}
// Decompose a syllable into several jamo. Returns its input if that isn't possible.
public static char[] decompose(char syllable) {
String normalized = Normalizer.normalize(String.valueOf(syllable), Normalizer.Form.NFD);
return normalized.toCharArray();
}
// Transliterate any Hangul in the given string. Leaves any non-Hangul characters unmodified.
public static String transliterate(String txt) {
if (txt == null || txt.isEmpty()) {
return txt;
}
// Most of the bulk of these loops is for handling special provisions - situations where the
// last jamo of one syllable and the first of the next need to be romanized as a pair in an
// irregular way.
StringBuilder builder = new StringBuilder();
boolean nextInitialJamoConsumed = false;
char[] syllables = txt.toCharArray();
for (int i = 0; i < syllables.length; i++) {
char thisSyllable = syllables[i];
// If this isn't in any of the Hangul blocks we know about, emit it as-is.
if (!inRange(thisSyllable, JAMO_BLOCK_START, JAMO_BLOCK_END)
&& !inRange(thisSyllable, SYLLABLES_BLOCK_START, SYLLABLES_BLOCK_END)
&& !inRange(thisSyllable, COMPAT_JAMO_BLOCK_START, COMPAT_JAMO_BLOCK_END)) {
builder.append(thisSyllable);
continue;
}
char[] theseJamo = decompose(thisSyllable);
for (int j = 0; j < theseJamo.length; j++) {
char thisJamo = theseJamo[j];
// If we already transliterated the first jamo of this syllable as part of a special
// provision, skip it. Otherwise, handle it in the unconditional else branch.
if (j == 0 && nextInitialJamoConsumed) {
nextInitialJamoConsumed = false;
continue;
}
// If this is the last jamo of this syllable and not the last syllable of the
// string, check for special provisions. If the next char is whitespace or not
// Hangul, it's the responsibility of transliterateSpecialProvisions() to return no
// value.
if (j == theseJamo.length - 1 && i < syllables.length - 1) {
char nextSyllable = syllables[i + 1];
char nextJamo = decompose(nextSyllable)[0];
Optional<String> specialProvision = transliterateSpecialProvisions(thisJamo, nextJamo);
if (specialProvision.isPresent()) {
builder.append(specialProvision.get());
nextInitialJamoConsumed = true;
} else {
// No special provision applies. Transliterate in isolation.
builder.append(transliterateSingleJamo(thisJamo));
}
continue;
}
// Everything else is transliterated in isolation.
builder.append(transliterateSingleJamo(thisJamo));
}
}
return builder.toString();
}
}