package org.xmlunit.matchers;

import org.hamcrest.BaseMatcher;
import org.hamcrest.Description;
import org.hamcrest.Factory;
import org.hamcrest.Matcher;
import org.w3c.dom.Node;
import org.xmlunit.builder.Input;
import org.xmlunit.util.Convert;
import org.xmlunit.xpath.JAXPXPathEngine;

import javax.xml.transform.Source;
import java.util.Map;

/**
 * This Hamcrest {@link Matcher} verifies whether the provided XPath expression corresponds to at least
 * one element in the provided object.
 *
 * <p>All types which are supported by {@link Input#from(Object)}  can be used as input for the object
 * against the matcher is evaluated.</p>
 *
 * <p><b>Simple Example</b></p>
 *
 * <pre>
 * final String xml = "<a><b attr=\"abc\"></b></a>";
 *
 * assertThat(xml, hasXPath("//a/b/@attr"));
 * assertThat(xml, not(hasXPath("//a/b/c")));
 * </pre>
 *
 * <p><b>Example with namespace mapping</b></p>
 *
 * <pre>
 *    String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
 *          "<feed xmlns=\"http://www.w3.org/2005/Atom\">" +
 *          "   <title>title</title>" +
 *          "   <entry>" +
 *          "       <title>title1</title>" +
 *          "       <id>id1</id>" +
 *          "   </entry>" +
 *          "</feed>";
 *
 *    HashMap<String, String> prefix2Uri = new HashMap<String, String>();
 *    prefix2Uri.put("atom", "http://www.w3.org/2005/Atom");
 *    assertThat(xmlRootElement,
 *          hasXPath("//atom:feed/atom:entry/atom:id").withNamespaceContext(prefix2Uri));
 * </pre>
 *
 * @since XMLUnit 2.1.0
 */
public class HasXPathMatcher extends BaseMatcher<Object> {

    private String xPath;

    private Map<String, String> prefix2Uri;

    /**
     * Creates a {@link HasXPathMatcher} instance with the associated XPath expression.
     *
     * @param xPath xPath expression
     */
    public HasXPathMatcher(String xPath) {
        this.xPath = xPath;
    }

    @Override
    public boolean matches(Object object) {
        JAXPXPathEngine engine = new JAXPXPathEngine();
        if (prefix2Uri != null) {
            engine.setNamespaceContext(prefix2Uri);
        }

        Source s = Input.from(object).build();
        Node n = Convert.toNode(s);
        Iterable<Node> nodes = engine.selectNodes(xPath, n);

        return nodes.iterator().hasNext();
    }

    @Override
    public void describeTo(Description description) {
        description.appendText("XML with XPath ").appendText(xPath);
    }

    @Override
    public void describeMismatch(Object item, Description mismatchDescription) {
        mismatchDescription.appendText("XPath returned no results.");
    }

    /**
     * Creates a matcher that matches when the examined XML input has at least one node
     * corresponding to the specified <code>xPath</code>.
     * 
     * <p>For example:</p>
     * <pre>assertThat(xml, hasXPath("/root/cars[0]/audi"))</pre>
     *
     * @param xPath the target xpath
     * @return the xpath matcher
     */
    @Factory
    public static HasXPathMatcher hasXPath(String xPath) {
        return new HasXPathMatcher(xPath);
    }

    /**
     * Utility method used for creating a namespace context mapping to be used in XPath matching.
     *
     * @param prefix2Uri prefix2Uri maps from prefix to namespace URI. It is used to resolve
     *                   XML namespace prefixes in the XPath expression
     */
    public HasXPathMatcher withNamespaceContext(Map<String, String> prefix2Uri) {
        this.prefix2Uri = prefix2Uri;
        return this;
    }
}