conversations-classic/src/main/java/eu/siacs/conversations/utils/Emoticons.java

package eu.siacs.conversations.utils;

import java.util.ArrayList;
import java.util.List;

public class Emoticons {

	private static final UnicodeRange MISC_SYMBOLS_AND_PICTOGRAPHS = new UnicodeRange(0x1F300,0x1F5FF);
	private static final UnicodeRange SUPPLEMENTAL_SYMBOLS = new UnicodeRange(0x1F900,0x1F9FF);
	private static final UnicodeRange EMOTICONS = new UnicodeRange(0x1F600,0x1F64F);
	private static final UnicodeRange TRANSPORT_SYMBOLS = new UnicodeRange(0x1F680,0x1F6FF);
	private static final UnicodeRange MISC_SYMBOLS = new UnicodeRange(0x2600,0x26FF);
	private static final UnicodeRange DINGBATS = new UnicodeRange(0x2700,0x27BF);
	private static final UnicodeRange REGIONAL_INDICATORS = new UnicodeRange(0x1F1E6,0x1F1FF);
	private static final UnicodeBlocks EMOJIS = new UnicodeBlocks(MISC_SYMBOLS_AND_PICTOGRAPHS,SUPPLEMENTAL_SYMBOLS,EMOTICONS,TRANSPORT_SYMBOLS,MISC_SYMBOLS,DINGBATS);
	private static final int ZWJ = 0x200D;
	private static final int VARIATION_16 = 0xFE0F;
	private static final UnicodeRange FITZPATRICK = new UnicodeRange(0x1F3FB,0x1F3FF);

	private static List<Symbol> parse(String input) {
		List<Symbol> symbols = new ArrayList<>();
		Builder builder = new Builder();
		boolean needsFinalBuild = false;
		for (int cp, i = 0; i < input.length(); i += Character.charCount(cp)) {
			cp = input.codePointAt(i);
			if (builder.offer(cp)) {
				needsFinalBuild = true;
			} else {
				symbols.add(builder.build());
				builder = new Builder();
				if (builder.offer(cp)) {
					needsFinalBuild = true;
				}
			}
		}
		if (needsFinalBuild) {
			symbols.add(builder.build());
		}
		return symbols;
	}

	public static boolean isEmoji(String input) {
		List<Symbol> symbols = parse(input);
		return symbols.size() == 1 && symbols.get(0) == Symbol.EMOJI;
	}

	public static boolean isOnlyEmoji(String input) {
		List<Symbol> symbols = parse(input);
		for(Symbol symbol : symbols) {
			if (symbol == Symbol.NON_EMOJI) {
				return false;
			}
		}
		return symbols.size() > 0;
	}

	private enum Symbol {
		EMOJI, NON_EMOJI
	}


	private static class Builder {
		private final List<Integer> codepoints = new ArrayList<>();


		public boolean offer(int codepoint) {
			boolean add = false;
			if (this.codepoints.size() == 0) {
				if (REGIONAL_INDICATORS.contains(codepoint)) {
					add = true;
				} else if (EMOJIS.contains(codepoint) && !FITZPATRICK.contains(codepoint) && codepoint != ZWJ) {
					add = true;
				}
			} else {
				int previous = codepoints.get(codepoints.size() -1);
				if (REGIONAL_INDICATORS.contains(previous) && REGIONAL_INDICATORS.contains(codepoint)) {
					if (codepoints.size() == 1) {
						add = true;
					}
				} else if (previous == VARIATION_16) {
					if (isMerger(codepoint)) {
						add = true;
					}
				} else if (FITZPATRICK.contains(previous)) {
					if (codepoint == ZWJ || EMOJIS.contains(codepoint)) {
						add = true;
					}
				} else if (ZWJ == previous) {
					if (EMOJIS.contains(codepoint) || FITZPATRICK.contains(codepoint)) {
						add = true;
					}
				} else if (isMerger(codepoint)) {
					add = true;
				} else if (codepoint == VARIATION_16 && EMOJIS.contains(previous)) {
					add = true;
				}
			}
			if (add) {
				codepoints.add(codepoint);
				return true;
			} else {
				return false;
			}
		}

		private static boolean isMerger(int codepoint) {
			return codepoint == ZWJ || FITZPATRICK.contains(codepoint);
		}

		public Symbol build() {
			return codepoints.size() == 0 ? Symbol.NON_EMOJI : Symbol.EMOJI;
		}
	}

	public static class UnicodeBlocks {
		final UnicodeRange[] ranges;

		public UnicodeBlocks(UnicodeRange... ranges) {
			this.ranges = ranges;
		}

		public boolean contains(int codepoint) {
			for(UnicodeRange range : ranges) {
				if (range.contains(codepoint)) {
					return true;
				}
			}
			return false;
		}
	}


	public static class UnicodeRange {

		private final int lower;
		private final int upper;

		UnicodeRange(int lower, int upper) {
			this.lower = lower;
			this.upper = upper;
		}

		public boolean contains(int codePoint) {
			return codePoint >= lower && codePoint <= upper;
		}
	}
}