package civitas.util;
   
   import java.io.IOException;
   import java.io.Reader;
   import java.util.Comparator;
   import java.util.Map;
   import java.util.Map.Entry;
   
   import org.mockito.invocation.InvocationOnMock;
  import org.mockito.stubbing.Answer;
  
  public class ReaderAnswer<T> implements Answer<T> {
  
  	private final Map<String, T> mockingMap;
  
  	public ReaderAnswer(final Map<String, T> mockingMap) {
  		this.mockingMap = mockingMap;
  	}
  
  	@Override
  	public T answer(final InvocationOnMock invocation) throws IOException {
  		Reader reader = (Reader) invocation.getArguments()[0];
  		for (Entry<String, T> entry : mockingMap.entrySet().stream()
  				.sorted(Comparator.comparingInt(o -> o.getKey().length()))
  				.toList()) {
  			T value = mockValueFromStream(reader, entry.getKey(), entry.getValue());
  			if (null != value) {
  				return value;
  			}
  		}
  		return null;
  	}
  
  	T mockValueFromStream(final Reader reader, final String theString, final T theValue) throws IOException {
  		int len = theString.length();
  		reader.mark(len + 1);
  		char[] buf = new char[len];
  		reader.read(buf);
  		if (new String(buf).equals(theString)) {
  			return theValue;
  		} else {
  			reader.reset();
  			return null;
  		}
  	}
  }