Keywords.java

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 * Copyright (C) Codehaus.org                                                *
 * ------------------------------------------------------------------------- *
 * Licensed under the Apache License, Version 2.0 (the "License");           *
 * you may not use this file except in compliance with the License.          *
 * You may obtain a copy of the License at                                   *
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 * http://www.apache.org/licenses/LICENSE-2.0                                *
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 * Unless required by applicable law or agreed to in writing, software       *
 * distributed under the License is distributed on an "AS IS" BASIS,         *
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 * See the License for the specific language governing permissions and       *
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package net.ion.rosetta;

import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.TreeSet;

import net.ion.rosetta.annotations.Private;
import net.ion.rosetta.functors.Map;
import net.ion.rosetta.functors.Maps;

/**
 * Helper class for creating lexers and parsers for keywords.
 * 
 * @author Ben Yu
 */
final class Keywords {

	private interface StringCase {
		Comparator<String> comparator();

		String toKey(String k);

		<T> net.ion.rosetta.functors.Map<String, T> toMap(java.util.Map<String, T> m);
	}

	private static final StringCase CASE_SENSITIVE = new CaseSensitive();
	private static final StringCase CASE_INSENSITIVE = new CaseInsensitive();

	private static class CaseSensitive implements StringCase {
		private static Comparator<String> COMPARATOR = new Comparator<String>() {
			public int compare(String a, String b) {
				if (a == b)
					return 0;
				else if (a == null)
					return -1;
				else if (b == null)
					return 1;
				else
					return a.compareTo(b);
			}
		};

		public Comparator<String> comparator() {
			return COMPARATOR;
		}

		public String toKey(String k) {
			return k;
		}

		public <T> net.ion.rosetta.functors.Map<String, T> toMap(java.util.Map<String, T> m) {
			return Maps.map(m);
		}
	}

	private static class CaseInsensitive implements StringCase {
		private static Comparator<String> COMPARATOR = new Comparator<String>() {
			public int compare(String a, String b) {
				if (a == b)
					return 0;
				else if (a == null)
					return -1;
				else if (b == null)
					return 1;
				else
					return a.compareToIgnoreCase(b);
			}
		};

		public Comparator<String> comparator() {
			return COMPARATOR;
		}

		public String toKey(String k) {
			return k.toLowerCase();
		}

		public <T> net.ion.rosetta.functors.Map<String, T> toMap(final java.util.Map<String, T> m) {
			return new net.ion.rosetta.functors.Map<String, T>() {
				public T map(String key) {
					return m.get(key.toLowerCase());
				}
			};
		}
	}

	private static StringCase getStringCase(boolean caseSensitive) {
		return caseSensitive ? CASE_SENSITIVE : CASE_INSENSITIVE;
	}

	@Private
	static String[] unique(Comparator<String> c, String... names) {
		TreeSet<String> set = new TreeSet<String>(c);
		set.addAll(Arrays.asList(names));
		return set.toArray(new String[set.size()]);
	}

	@SuppressWarnings("unchecked")
	static <T> Lexicon lexicon(Parser<String> wordScanner, String[] keywordNames, boolean caseSensitive, final Map<String, ?> defaultMap) {
		StringCase scase = getStringCase(caseSensitive);
		HashMap<String, Object> map = new HashMap<String, Object>();
		for (String n : unique(scase.comparator(), keywordNames)) {
			Object value = Tokens.reserved(n);
			map.put(scase.toKey(n), value);
		}
		final Map<String, Object> fmap = scase.toMap(map);
		Map<String, Object> tokenizerMap = new Map<String, Object>() {
			public Object map(String text) {
				Object val = fmap.map(text);
				if (val != null)
					return val;
				else
					return defaultMap.map(text);
			}
		};
		return new Lexicon(fmap, wordScanner.map(tokenizerMap));
	}
}