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package javax.xml.xpath;

import javax.xml.namespace.QName;

import org.xml.sax.InputSource;

/**

 * {@code XPathExpression} provides access to compiled XPath expressions.

 * The XPath evaluation is affected by the factors described in the following table.

 *

 * <a id="XPathExpression-evaluation"></a>

 * <table class="striped">

 *    <caption>Evaluation of XPath Expressions</caption>

 *    <thead>

 *      <tr>

 *        <th scope="col">Factor</th>

 *        <th scope="col">Behavior</th>

 *      </tr>

 *    </thead>

 *    <tbody>

 *    <tr>

 *      <th scope="row">context</th>

 *      <td>

 *        The type of the context is implementation-dependent. If the value is

 *        null, the operation must have no dependency on the context, otherwise

 *        an XPathExpressionException will be thrown.

 *

 *        For the purposes of evaluating XPath expressions, a DocumentFragment

 *        is treated like a Document node.

 *      </td>

 *    </tr>

 *    <tr>

 *      <th scope="row">variables</th>

 *      <td>

 *        If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}.

 *        An {@link XPathExpressionException} is raised if the variable resolver is undefined or

 *        the resolver returns {@code null} for the variable.

 *        The value of a variable must be immutable through the course of any single evaluation.

 *      </td>

 *    </tr>

 *    <tr>

 *      <th scope="row">functions</th>

 *      <td>

 *        If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver}.

 *        An {@link XPathExpressionException} is raised if the function resolver is undefined or

 *        the function resolver returns {@code null} for the function.

 *      </td>

 *    </tr>

 *    <tr>

 *      <th scope="row">QNames</th>

 *      <td>

 *        QNames in the expression are resolved against the XPath namespace context.

 *      </td>

 *    </tr>

 *    <tr>

 *      <th scope="row">result</th>

 *      <td>

 *        This result of evaluating an expression is converted to an instance of the desired return type.

 *        Valid return types are defined in {@link XPathConstants}.

 *        Conversion to the return type follows XPath conversion rules.

 *      </td>

 *    </tr>

 *   </tbody>

 * </table>

 *

 * <p>An XPath expression is not thread-safe and not reentrant.

 * In other words, it is the application's responsibility to make

 * sure that one {@link XPathExpression} object is not used from

 * more than one thread at any given time, and while the {@code evaluate}

 * method is invoked, applications may not recursively call

 * the {@code evaluate} method.

 *

 * @see <a href="http://www.w3.org/TR/xpath#section-Expressions">XML Path Language (XPath) Version 1.0, Expressions</a>

 * @since 1.5

 */

public interface XPathExpression {

    /**

     * Evaluate the compiled XPath expression in the specified context and return the result as the specified type.

     *

     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,

     * variable, function and QName resolution and return type conversion.

     *

     * <p>

     * The parameter {@code item} represents the context the XPath expression

     * will be operated on. The type of the context is implementation-dependent.

     * If the value is {@code null}, the operation must have no dependency on

     * the context, otherwise an XPathExpressionException will be thrown.

     *

     * @implNote

     * The type of the context is usually {@link org.w3c.dom.Node}.

     *

     * @param item The context the XPath expression will be evaluated in.

     * @param returnType The result type expected to be returned by the XPath expression.

     *

     * @return The {@code Object} that is the result of evaluating the expression and converting the result to

     *   {@code returnType}.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants}.

     * @throws NullPointerException If {@code returnType} is {@code null}.

     */

    public Object evaluate(Object item, QName returnType)

        throws XPathExpressionException;

    /**

     * Evaluate the compiled XPath expression in the specified context and return the result as a {@code String}.

     *

     * <p>This method calls {@link #evaluate(Object item, QName returnType)} with a {@code returnType} of

     * {@link XPathConstants#STRING}.

     *

     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,

     * variable, function and QName resolution and return type conversion.

     *

     * <p>

     * The parameter {@code item} represents the context the XPath expression

     * will be operated on. The type of the context is implementation-dependent.

     * If the value is {@code null}, the operation must have no dependency on

     * the context, otherwise an XPathExpressionException will be thrown.

     *

     * @implNote

     * The type of the context is usually {@link org.w3c.dom.Node}.

     *

     * @param item The context the XPath expression will be evaluated in.

     *

     * @return The result of evaluating an XPath expression as a {@code String}.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     */

    public String evaluate(Object item)

        throws XPathExpressionException;

    /**

     * Evaluate the compiled XPath expression in the context

     * of the specified {@code InputSource} and return the result as the

     * specified type.

     *

     * <p>This method builds a data model for the {@link InputSource} and calls

     * {@link #evaluate(Object item, QName returnType)} on the resulting document object.

     *

     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,

     * variable, function and QName resolution and return type conversion.

     *

     * <p>If {@code returnType} is not one of the types defined in {@link XPathConstants},

     * then an {@code IllegalArgumentException} is thrown.

     *

     * <p>If {@code source} or {@code returnType} is {@code null},

     * then a {@code NullPointerException} is thrown.

     *

     * @param source The {@code InputSource} of the document to evaluate over.

     * @param returnType The desired return type.

     *

     * @return The {@code Object} that is the result of evaluating the expression and converting the result to

     *   {@code returnType}.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants}.

     * @throws NullPointerException If {@code source or returnType} is {@code null}.

     */

    public Object evaluate(InputSource source, QName returnType)

        throws XPathExpressionException;

    /**

     * Evaluate the compiled XPath expression in the context

     * of the specified {@code InputSource} and return the result as a

     * {@code String}.

     *

     * <p>This method calls {@link #evaluate(InputSource source, QName returnType)} with a {@code returnType} of

     * {@link XPathConstants#STRING}.

     *

     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,

     * variable, function and QName resolution and return type conversion.

     *

     * <p>If {@code source} is {@code null}, then a {@code NullPointerException} is thrown.

     *

     * @param source The {@code InputSource} of the document to evaluate over.

     *

     * @return The {@code String} that is the result of evaluating the expression and converting the result to a

     *   {@code String}.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws NullPointerException If {@code source} is {@code null}.

     */

    public String evaluate(InputSource source)

        throws XPathExpressionException;

    /**

     * Evaluate the compiled XPath expression in the specified context, and return

     * the result with the type specified through the {@code class type}.

     *

     * <p>

     * The parameter {@code item} represents the context the XPath expression

     * will be operated on. The type of the context is implementation-dependent.

     * If the value is {@code null}, the operation must have no dependency on

     * the context, otherwise an XPathExpressionException will be thrown.

     *

     * @implNote

     * The type of the context is usually {@link org.w3c.dom.Node}.

     *

     * @implSpec

     * The default implementation in the XPath API is equivalent to:

     * <pre> {@code

     *     (T)evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type));

     * }</pre>

     *

     * Since the {@code evaluate} method does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying

     * XPathEvaluationResult as the type will result in IllegalArgumentException.

     * Any implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override

     * this method.

     *

     * @param <T> The class type that will be returned by the XPath expression.

     * @param item The context the XPath expression will be evaluated in.

     * @param type The class type expected to be returned by the XPath expression.

     *

     * @return The result of evaluating the expression.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If {@code type} is not of the types

     * corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType

     * XPathResultType}, or XPathEvaluationResult is specified as the type but an

     * implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type is not available.

     * @throws NullPointerException If {@code type} is {@code null}.

     *

     * @since 9

     */

    default <T>T evaluateExpression(Object item, Class<T> type)

        throws XPathExpressionException

    {

        return type.cast(evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type)));

    }

    /**

     * Evaluate the compiled XPath expression in the specified context. This is

     * equivalent to calling {@link #evaluateExpression(Object item, Class type)}

     * with type {@link XPathEvaluationResult}:

     * <pre> {@code

     *     evaluateExpression(item, XPathEvaluationResult.class);

     * }</pre>

     * <p>

     * The parameter {@code item} represents the context the XPath expression

     * will be operated on. The type of the context is implementation-dependent.

     * If the value is {@code null}, the operation must have no dependency on

     * the context, otherwise an XPathExpressionException will be thrown.

     *

     * @implNote

     * The type of the context is usually {@link org.w3c.dom.Node}.

     *

     * @implSpec

     * The default implementation in the XPath API is equivalent to:

     * <pre> {@code

     *     evaluateExpression(item, XPathEvaluationResult.class);

     * }</pre>

     *

     * Since the {@code evaluate} method does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY}

     * type, the default implementation of this method will always throw an

     * IllegalArgumentException. Any implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore

     * override this method.

     *

     * @param item The context the XPath expression will be evaluated in.

     *

     * @return The result of evaluating the expression.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If the implementation of this method

     * does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.

     *

     * @since 9

     */

    default XPathEvaluationResult<?> evaluateExpression(Object item)

        throws XPathExpressionException

    {

        return evaluateExpression(item, XPathEvaluationResult.class);

    }

    /**

     * Evaluate the compiled XPath expression in the specified context,

     * and return the result with the type specified through the {@code class type}

     * <p>

     * This method builds a data model for the {@link InputSource} and calls

     * {@link #evaluateExpression(Object item, Class type)} on the resulting

     * document object.

     * <P>

     * By default, the JDK's data model is {@link org.w3c.dom.Document}.

     *

     * @implSpec

     * The default implementation in the XPath API is equivalent to:

     * <pre> {@code

           (T)evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type));

     * }</pre>

     *

     * Since the {@code evaluate} method does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying

     * XPathEvaluationResult as the type will result in IllegalArgumentException.

     * Any implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override

     * this method.

     *

     * @param <T> The class type that will be returned by the XPath expression.

     * @param source The {@code InputSource} of the document to evaluate over.

     * @param type The class type expected to be returned by the XPath expression.

     *

     * @return The result of evaluating the expression.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If {@code type} is not of the types

     * corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType

     * XPathResultType}, or XPathEvaluationResult is specified as the type but an

     * implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type

     * is not available.

     * @throws NullPointerException If {@code source or type} is {@code null}.

     *

     * @since 9

     */

    default <T>T evaluateExpression(InputSource source, Class<T> type)

        throws XPathExpressionException

    {

        return type.cast(evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type)));

    }

    /**

     * Evaluate the compiled XPath expression in the specified context. This is

     * equivalent to calling {@link #evaluateExpression(InputSource source, Class type)}

     * with type {@link XPathEvaluationResult}:

     * <pre> {@code

     *     evaluateExpression(source, XPathEvaluationResult.class);

     * }</pre>

     *

     * @implSpec

     * The default implementation in the XPath API is equivalent to:

     * <pre> {@code

     *     (XPathEvaluationResult)evaluateExpression(source, XPathEvaluationResult.class);

     * }</pre>

     *

     * Since the {@code evaluate} method does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY}

     * type, the default implementation of this method will always throw an

     * IllegalArgumentException. Any implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore

     * override this method.

     *

     * @param source The {@code InputSource} of the document to evaluate over.

     *

     * @return The result of evaluating the expression.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If the implementation of this method

     * does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.

     * @throws NullPointerException If {@code source} is {@code null}.

     *

     * @since 9

     */

    default XPathEvaluationResult<?> evaluateExpression(InputSource source)

        throws XPathExpressionException

    {

        return evaluateExpression(source, XPathEvaluationResult.class);

    }

}