Pattern.java

package com.firefly.utils.pattern;

import com.firefly.utils.StringUtils;

public abstract class Pattern {
	
	private static final AllMatch ALL_MATCH = new AllMatch();
	
	/**
	 * Matches a string according to the specified pattern
	 * @param str Target string
	 * @return If it returns null, that represents matching failure, 
	 * else it returns an array contains all strings are matched.
	 */
	abstract public String[] match(String str);
	
	public static Pattern compile(String pattern, String wildcard) {
		final boolean startWith = pattern.startsWith(wildcard);
		final boolean endWith = pattern.endsWith(wildcard);
		final String[] array = StringUtils.split(pattern, wildcard);
		
		switch (array.length) {
		case 0:
			return ALL_MATCH;
		case 1:
			if (startWith && endWith)
				return new HeadAndTailMatch(array[0]);
			
			if (startWith)
				return new HeadMatch(array[0]);
			
			if (endWith)
				return new TailMatch(array[0]);
			
			return new EqualsMatch(pattern);
		default:
			return new MultipartMatch(startWith, endWith, array);
		}
	}
	
	
	
	private static class MultipartMatch extends Pattern {
		
		private final boolean startWith, endWith;
		private final String[] parts;
		private int num;

		public MultipartMatch(boolean startWith, boolean endWith, String[] parts) {
			super();
			this.startWith = startWith;
			this.endWith = endWith;
			this.parts = parts;
			num = parts.length - 1;
			if(startWith)
				num++;
			if(endWith)
				num++;
		}

		@Override
		public String[] match(String str) {
			int currentIndex = -1;
			int lastIndex = -1;
			String[] ret = new String[num];
			
			for (int i = 0; i < parts.length; i++) {
				String part = parts[i];
				int j = startWith ? i : i - 1;
				currentIndex = str.indexOf(part, lastIndex + 1);
				
				if (currentIndex > lastIndex) {
					if(i != 0 || startWith)
						ret[j] = str.substring(lastIndex + 1, currentIndex);
					
					lastIndex = currentIndex + part.length() - 1;
					continue;
				}
				return null;
			}
			
			if(endWith)
				ret[num - 1] = str.substring(lastIndex + 1);
			
			return ret;
		}
		
	}
	
	private static class TailMatch extends Pattern {
		private final String part;

		public TailMatch(String part) {
			this.part = part;
		}

		@Override
		public String[] match(String str) {
			int currentIndex = str.indexOf(part);
			if(currentIndex == 0) {
				return new String[] { str.substring(part.length()) };
			}
			return null;
		}
	}
	
	private static class HeadMatch extends Pattern {
		private final String part;

		public HeadMatch(String part) {
			this.part = part;
		}

		@Override
		public String[] match(String str) {
			int currentIndex = str.indexOf(part);
			if(currentIndex + part.length() == str.length()) {
				return new String[] { str.substring(0, currentIndex) };
			}
			return null;
		}
		
		
	}
	
	private static class HeadAndTailMatch extends Pattern {
		private final String part;

		public HeadAndTailMatch(String part) {
			this.part = part;
		}

		@Override
		public String[] match(String str) {
			int currentIndex = str.indexOf(part);
			if(currentIndex >= 0) {
				String[] ret = new String[]{str.substring(0, currentIndex),
						str.substring(currentIndex + part.length(), str.length()) };
				return ret;
			}
			return null;
		}
		
		
	}
	
	private static class EqualsMatch extends Pattern {
		private final String pattern;
		
		public EqualsMatch(String pattern) {
			this.pattern = pattern;
		}

		@Override
		public String[] match(String str) {
			return pattern.equals(str) ? new String[0] : null;
		}
	}
	
	private static class AllMatch extends Pattern {

		@Override
		public String[] match(String str) {
			return new String[]{str};
		}
	}
}