r/org.eclipse.statet.r.core/src/org/eclipse/statet/r/core/RSymbolComparator.java

/*=============================================================================#
 # Copyright (c) 2007, 2021 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.r.core;

import java.util.Comparator;
import java.util.Locale;

import com.ibm.icu.text.Collator;
import com.ibm.icu.text.RuleBasedCollator;

import org.eclipse.statet.jcommons.lang.NonNullByDefault;
import org.eclipse.statet.jcommons.lang.Nullable;


/**
 * 
 */
@NonNullByDefault
public class RSymbolComparator implements Comparator<String> {
	
	
	public static final class PrefixPattern {
		
		private final char[] prefix;
		
		
		public PrefixPattern(final String namePrefix) {
			this.prefix= namePrefix.toLowerCase().toCharArray();
		}
		
		
		/**
		 * Tolerant string comparison
		 * 
		 * @param candidate string to test against prefix
		 * @param prefix char array of lowercase prefix
		 * @return if candidate starts with prefix
		 */
		public boolean matches(final @Nullable String candidate) {
			if (candidate == null || candidate.isEmpty()) {
				return false;
			}
			if (this.prefix.length == 0) {
				return (candidate.charAt(0) != '.');
			}
			int pC= this.prefix[0];
			int cC= Character.toLowerCase(candidate.charAt(0));
			if (cC != pC) {
				return false;
			}
			int pIdx= 0;
			int cIdx= 0;
			while (true) {
				if (pC == cC) {
					if (++pIdx >= this.prefix.length) {
						return true;
					}
					if (++cIdx >= candidate.length()) {
						return false;
					}
					pC= this.prefix[pIdx];
					cC= Character.toLowerCase(candidate.charAt(cIdx));
					continue;
				}
				if (pC == '.' || pC == '_') {
					if (++pIdx >= this.prefix.length) {
						return true;
					}
					pC= this.prefix[pIdx];
					continue;
				}
				if (cC == '.' || cC == '_') {
					if (++cIdx >= candidate.length()) {
						return false;
					}
					cC= Character.toLowerCase(candidate.charAt(cIdx));
					continue;
				}
				return false;
			}
		}
	}
	
	
	public static final Collator R_NAMES_COLLATOR= Collator.getInstance(Locale.ENGLISH);
	static {
		((RuleBasedCollator) R_NAMES_COLLATOR).setUpperCaseFirst(true);
	}
	
	
	@Override
	public int compare(final String name1, final String name2) {
		return R_NAMES_COLLATOR.compare(check(name1), check(name2));
	}
	
	private String check(final String name) {
		if (name.length() > 0 && name.charAt(0) == '`') {
			return name.substring(1);
		}
		return name;
	}
	
}