package org.hamcrest.text;

import org.hamcrest.Description;
import org.hamcrest.Matcher;
import org.hamcrest.TypeSafeMatcher;

import java.util.regex.Pattern;

import static org.hamcrest.core.AnyOf.anyOf;
import static org.hamcrest.core.IsNull.nullValue;

/**
 
* Matches blank Strings (and null).
 
*/

public final class IsBlankString extends TypeSafeMatcher<String> {
    
private static final IsBlankString BLANK_INSTANCE = new IsBlankString();
    
@SuppressWarnings("unchecked")
    
private static final Matcher<String> NULL_OR_BLANK_INSTANCE = anyOf(nullValue(), BLANK_INSTANCE);

    
private static final Pattern REGEX_WHITESPACE = Pattern.compile("\\s*");

    
private IsBlankString() { }

    
@Override
    
public boolean matchesSafely(String item) {
        
return REGEX_WHITESPACE.matcher(item).matches();
    
}

    
@Override
    
public void describeTo(Description description) {
        
description.appendText("a blank string");
    
}

    
/**
     
* Creates a matcher of {@link String} that matches when the examined string contains
     
* zero or more whitespace characters and nothing else.
     
* For example:
     
* <pre>assertThat("
  
", is(blankString()))</pre>
     
*/

    
public static Matcher<String> blankString() {
        
return BLANK_INSTANCE;
    
}

    
/**
     
* Creates a matcher of {@link String} that matches when the examined string is <code>null</code>, or
     
* contains zero or more whitespace characters and nothing else.
     
* For example:
     
* <pre>assertThat(((String)null), is(blankOrNullString()))</pre>
     
*
 

     
*/

    
public static Matcher<String> blankOrNullString() {
        
return NULL_OR_BLANK_INSTANCE;
    
}
}