minecraft-src/net/minecraft/util/StringDecomposer.java

package net.minecraft.util;

import java.util.Optional;
import net.minecraft.ChatFormatting;
import net.minecraft.network.chat.FormattedText;
import net.minecraft.network.chat.Style;

public class StringDecomposer {
	private static final char REPLACEMENT_CHAR = '<27>';
	private static final Optional<Object> STOP_ITERATION = Optional.of(Unit.INSTANCE);

	private static boolean feedChar(Style style, FormattedCharSink sink, int position, char character) {
		return Character.isSurrogate(character) ? sink.accept(position, style, 65533) : sink.accept(position, style, character);
	}

	public static boolean iterate(String text, Style style, FormattedCharSink sink) {
		int i = text.length();

		for (int j = 0; j < i; j++) {
			char c = text.charAt(j);
			if (Character.isHighSurrogate(c)) {
				if (j + 1 >= i) {
					if (!sink.accept(j, style, 65533)) {
						return false;
					}
					break;
				}

				char d = text.charAt(j + 1);
				if (Character.isLowSurrogate(d)) {
					if (!sink.accept(j, style, Character.toCodePoint(c, d))) {
						return false;
					}

					j++;
				} else if (!sink.accept(j, style, 65533)) {
					return false;
				}
			} else if (!feedChar(style, sink, j, c)) {
				return false;
			}
		}

		return true;
	}

	public static boolean iterateBackwards(String text, Style style, FormattedCharSink sink) {
		int i = text.length();

		for (int j = i - 1; j >= 0; j--) {
			char c = text.charAt(j);
			if (Character.isLowSurrogate(c)) {
				if (j - 1 < 0) {
					if (!sink.accept(0, style, 65533)) {
						return false;
					}
					break;
				}

				char d = text.charAt(j - 1);
				if (Character.isHighSurrogate(d)) {
					if (!sink.accept(--j, style, Character.toCodePoint(d, c))) {
						return false;
					}
				} else if (!sink.accept(j, style, 65533)) {
					return false;
				}
			} else if (!feedChar(style, sink, j, c)) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Iterate a String while applying legacy formatting codes starting with a {@code §} sign.
	 */
	public static boolean iterateFormatted(String text, Style style, FormattedCharSink sink) {
		return iterateFormatted(text, 0, style, sink);
	}

	/**
	 * Iterate a String while applying legacy formatting codes starting with a {@code §} sign.
	 * 
	 * @param skip The amount of characters to skip from the beginning.
	 */
	public static boolean iterateFormatted(String text, int skip, Style style, FormattedCharSink sink) {
		return iterateFormatted(text, skip, style, style, sink);
	}

	/**
	 * Iterate a String while applying legacy formatting codes starting with a {@code §} sign.
	 * 
	 * @param skip The amount of character to skip from the beginning.
	 * @param currentStyle The current style at the starting position after the skip.
	 * @param defaultStyle The default style for the sequence that should be applied after a reset format code ({@code §r})
	 */
	public static boolean iterateFormatted(String text, int skip, Style currentStyle, Style defaultStyle, FormattedCharSink sink) {
		int i = text.length();
		Style style = currentStyle;

		for (int j = skip; j < i; j++) {
			char c = text.charAt(j);
			if (c == 167) {
				if (j + 1 >= i) {
					break;
				}

				char d = text.charAt(j + 1);
				ChatFormatting chatFormatting = ChatFormatting.getByCode(d);
				if (chatFormatting != null) {
					style = chatFormatting == ChatFormatting.RESET ? defaultStyle : style.applyLegacyFormat(chatFormatting);
				}

				j++;
			} else if (Character.isHighSurrogate(c)) {
				if (j + 1 >= i) {
					if (!sink.accept(j, style, 65533)) {
						return false;
					}
					break;
				}

				char d = text.charAt(j + 1);
				if (Character.isLowSurrogate(d)) {
					if (!sink.accept(j, style, Character.toCodePoint(c, d))) {
						return false;
					}

					j++;
				} else if (!sink.accept(j, style, 65533)) {
					return false;
				}
			} else if (!feedChar(style, sink, j, c)) {
				return false;
			}
		}

		return true;
	}

	public static boolean iterateFormatted(FormattedText text, Style style, FormattedCharSink sink) {
		return text.visit((stylex, string) -> iterateFormatted(string, 0, stylex, sink) ? Optional.empty() : STOP_ITERATION, style).isEmpty();
	}

	public static String filterBrokenSurrogates(String text) {
		StringBuilder stringBuilder = new StringBuilder();
		iterate(text, Style.EMPTY, (i, style, j) -> {
			stringBuilder.appendCodePoint(j);
			return true;
		});
		return stringBuilder.toString();
	}

	public static String getPlainText(FormattedText text) {
		StringBuilder stringBuilder = new StringBuilder();
		iterateFormatted(text, Style.EMPTY, (i, style, j) -> {
			stringBuilder.appendCodePoint(j);
			return true;
		});
		return stringBuilder.toString();
	}
}