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package java.security.cert;

import java.util.Iterator;

import java.util.Set;

/**

 * An immutable valid policy tree node as defined by the PKIX certification

 * path validation algorithm.

 *

 * <p>One of the outputs of the PKIX certification path validation

 * algorithm is a valid policy tree, which includes the policies that

 * were determined to be valid, how this determination was reached,

 * and any policy qualifiers encountered. This tree is of depth

 * <i>n</i>, where <i>n</i> is the length of the certification

 * path that has been validated.

 *

 * <p>Most applications will not need to examine the valid policy tree.

 * They can achieve their policy processing goals by setting the

 * policy-related parameters in {@code PKIXParameters}. However,

 * the valid policy tree is available for more sophisticated applications,

 * especially those that process policy qualifiers.

 *

 * <p>{@link PKIXCertPathValidatorResult#getPolicyTree()

 * PKIXCertPathValidatorResult.getPolicyTree} returns the root node of the

 * valid policy tree. The tree can be traversed using the

 * {@link #getChildren getChildren} and {@link #getParent getParent} methods.

 * Data about a particular node can be retrieved using other methods of

 * {@code PolicyNode}.

 *

 * <p><b>Concurrent Access</b>

 * <p>All {@code PolicyNode} objects must be immutable and

 * thread-safe. Multiple threads may concurrently invoke the methods defined

 * in this class on a single {@code PolicyNode} object (or more than one)

 * with no ill effects. This stipulation applies to all public fields and

 * methods of this class and any added or overridden by subclasses.

 *

 * @since       1.4

 * @author      Sean Mullan

 */

public interface PolicyNode {

    /**

     * Returns the parent of this node, or {@code null} if this is the

     * root node.

     *

     * @return the parent of this node, or {@code null} if this is the

     * root node

     */

    PolicyNode getParent();

    /**

     * Returns an iterator over the children of this node. Any attempts to

     * modify the children of this node through the

     * {@code Iterator}'s remove method must throw an

     * {@code UnsupportedOperationException}.

     *

     * @return an iterator over the children of this node

     */

    Iterator<? extends PolicyNode> getChildren();

    /**

     * Returns the depth of this node in the valid policy tree.

     *

     * @return the depth of this node (0 for the root node, 1 for its

     * children, and so on)

     */

    int getDepth();

    /**

     * Returns the valid policy represented by this node.

     *

     * @return the {@code String} OID of the valid policy

     * represented by this node. For the root node, this method always returns

     * the special anyPolicy OID: "2.5.29.32.0".

     */

    String getValidPolicy();

    /**

     * Returns the set of policy qualifiers associated with the

     * valid policy represented by this node.

     *

     * @return an immutable {@code Set} of

     * {@code PolicyQualifierInfo}s. For the root node, this

     * is always an empty {@code Set}.

     */

    Set<? extends PolicyQualifierInfo> getPolicyQualifiers();

    /**

     * Returns the set of expected policies that would satisfy this

     * node's valid policy in the next certificate to be processed.

     *

     * @return an immutable {@code Set} of expected policy

     * {@code String} OIDs. For the root node, this method

     * always returns a {@code Set} with one element, the

     * special anyPolicy OID: "2.5.29.32.0".

     */

    Set<String> getExpectedPolicies();

    /**

     * Returns the criticality indicator of the certificate policy extension

     * in the most recently processed certificate.

     *

     * @return {@code true} if extension marked critical,

     * {@code false} otherwise. For the root node, {@code false}

     * is always returned.

     */

    boolean isCritical();

}