package org.kuali.common.util.function;
   
   import static com.google.common.base.Preconditions.checkArgument;
   import static com.google.common.base.Preconditions.checkNotNull;
   
   import org.apache.commons.lang3.StringUtils;
   
   import com.google.common.base.Function;
   import com.google.common.base.Optional;
  
  public final class PrefixFunction implements Function<String, String> {
  
  	private final String prefix;
  	private final Optional<String> separator;
  
  	@Override
  	public String apply(String input) {
  		checkNotNull(input, "'input' cannot be null");
  		StringBuilder sb = new StringBuilder();
  		sb.append(prefix);
  		if (separator.isPresent()) {
  			sb.append(separator.get());
  		}
  		sb.append(input);
  		return sb.toString();
  	}
  
  	private PrefixFunction(Builder builder) {
  		this.prefix = builder.prefix;
  		this.separator = builder.separator;
  	}
  
  	public static PrefixFunction of(String prefix) {
  		return builder(prefix).build();
  	}
  
  	public static PrefixFunction of(String prefix, String separator) {
  		return builder(prefix).separator(separator).build();
  	}
  
  	public static Builder builder(String prefix) {
  		return new Builder(prefix);
  	}
  
  	public static class Builder implements org.apache.commons.lang3.builder.Builder<PrefixFunction> {
  
  		// Required
  		private final String prefix;
  
  		// Optional
  		private Optional<String> separator = Optional.absent();
  
  		public Builder(String prefix) {
  			this.prefix = prefix;
  		}
  
  		public Builder separator(String separator) {
  			this.separator = Optional.of(separator);
  			return this;
  		}
  
  		@Override
  		public PrefixFunction build() {
  			PrefixFunction instance = new PrefixFunction(this);
  			validate(instance);
  			return instance;
  		}
  
  		private static void validate(PrefixFunction instance) {
  			checkArgument(!StringUtils.isBlank(instance.prefix), "'prefix' cannot be blank");
  			checkNotNull(instance.separator, "'separator' cannot be null");
  			if (instance.separator.isPresent()) {
  				checkArgument(!StringUtils.isBlank(instance.separator.get()), "'separator' cannot be blank");
  			}
  		}
  
  		public Optional<String> getSeparator() {
  			return separator;
  		}
  
  		public void setSeparator(Optional<String> separator) {
  			this.separator = separator;
  		}
  
  		public String getPrefix() {
  			return prefix;
  		}
  	}
  
  }