package com.nimbusds.jose.proc;


import java.io.IOException;
import java.security.Key;
import java.text.ParseException;
import java.util.List;
import java.util.ListIterator;

import com.nimbusds.jose.*;
import com.nimbusds.jose.crypto.factories.DefaultJWEDecrypterFactory;
import com.nimbusds.jose.crypto.factories.DefaultJWSVerifierFactory;
import net.jcip.annotations.ThreadSafe;


/**
 * Default processor of {@link com.nimbusds.jose.PlainObject unsecured}
 * (plain), {@link com.nimbusds.jose.JWSObject JWS} and
 * {@link com.nimbusds.jose.JWEObject JWE} objects.
 *
 * <p>Must be configured with the following:
 *
 * <ol>
 *     <li>To verify JWS objects: A {@link JWSKeySelector JWS key selector} to
 *     determine the key candidate(s) for the signature verification. The key
 *     selection procedure is application-specific and may involve key ID
 *     lookup, a certificate check and / or other information supplied in the
 *     message {@link SecurityContext context}.</li>
 *
 *     <li>To decrypt JWE objects: A {@link JWEKeySelector JWE key selector} to
 *     determine the key candidate(s) for decryption. The key selection
 *     procedure is application-specific and may involve key ID lookup, a
 *     certificate check and / or other information supplied in the message
 *     {@link SecurityContext context}.</li>
 * </ol>
 *
 * <p>An optional context parameter is available to facilitate passing of
 * additional data between the caller and the underlying selector of key
 * candidates (in both directions).
 *
 * <p>See sections 6 of RFC 7515 (JWS) and RFC 7516 (JWE) for guidelines on key
 * selection.
 *
 * <p>This processor comes with the default {@link DefaultJWSVerifierFactory
 * JWS verifier factory} and the default {@link DefaultJWEDecrypterFactory
 * JWE decrypter factory}; they can construct verifiers / decrypters for all
 * standard JOSE algorithms implemented by the library.
 *
 * <p>Note that for security reasons this processor is hardwired to reject
 * unsecured (plain) JOSE objects. Override the {@link #process(PlainObject,
 * SecurityContext)} method if you need to handle unsecured JOSE objects as
 * well.
 *
 * <p>To process JSON Web Tokens (JWTs) use the
 * {@link com.nimbusds.jwt.proc.DefaultJWTProcessor} class.
 *
 * @author Vladimir Dzhuvinov
 * @version 2016-06-15
 */
@ThreadSafe
public class DefaultJOSEProcessor<C extends SecurityContext> implements ConfigurableJOSEProcessor<C>{

        // Cache exceptions
        private static final BadJOSEException PLAIN_JOSE_REJECTED_EXCEPTION =
                new BadJOSEException("Unsecured (plain) JOSE objects are rejected, extend class to handle");
        private static final BadJOSEException NO_JWS_KEY_SELECTOR_EXCEPTION =
                new BadJOSEException("JWS object rejected: No JWS key selector is configured");
        private static final BadJOSEException NO_JWE_KEY_SELECTOR_EXCEPTION =
                new BadJOSEException("JWE object rejected: No JWE key selector is configured");
        private static final JOSEException NO_JWS_VERIFIER_FACTORY_EXCEPTION =
                new JOSEException("No JWS verifier is configured");
        private static final JOSEException NO_JWE_DECRYPTER_FACTORY_EXCEPTION =
                new JOSEException("No JWE decrypter is configured");
        private static final BadJOSEException NO_JWS_KEY_CANDIDATES_EXCEPTION =
                new BadJOSEException("JWS object rejected: No matching key(s) found");
        private static final BadJOSEException NO_JWE_KEY_CANDIDATES_EXCEPTION =
                new BadJOSEException("JWE object rejected: No matching key(s) found");
        private static final BadJOSEException INVALID_SIGNATURE =
                new BadJWSException("JWS object rejected: Invalid signature");
        private static final BadJOSEException NO_MATCHING_VERIFIERS_EXCEPTION =
                new BadJOSEException("JWS object rejected: No matching verifier(s) found");
        private static final BadJOSEException NO_MATCHING_DECRYPTERS_EXCEPTION =
                new BadJOSEException("JWE object rejected: No matching decrypter(s) found");


        /**
         * The JWS key selector.
         */
        private JWSKeySelector<C> jwsKeySelector;


        /**
         * The JWE key selector.
         */
        private JWEKeySelector<C> jweKeySelector;


        /**
         * The JWS verifier factory.
         */
        private JWSVerifierFactory jwsVerifierFactory = new DefaultJWSVerifierFactory();


        /**
         * The JWE decrypter factory.
         */
        private JWEDecrypterFactory jweDecrypterFactory = new DefaultJWEDecrypterFactory();


        @Override
        public JWSKeySelector<C> getJWSKeySelector() {

                return jwsKeySelector;
        }


        @Override
        public void setJWSKeySelector(final JWSKeySelector<C> jwsKeySelector) {

                this.jwsKeySelector = jwsKeySelector;
        }


        @Override
        public JWEKeySelector<C> getJWEKeySelector() {

                return jweKeySelector;
        }


        @Override
        public void setJWEKeySelector(final JWEKeySelector<C> jweKeySelector) {

                this.jweKeySelector = jweKeySelector;
        }


        @Override
        public JWSVerifierFactory getJWSVerifierFactory() {

                return jwsVerifierFactory;
        }


        @Override
        public void setJWSVerifierFactory(final JWSVerifierFactory factory) {

                jwsVerifierFactory = factory;
        }


        @Override
        public JWEDecrypterFactory getJWEDecrypterFactory() {

                return jweDecrypterFactory;
        }


        @Override
        public void setJWEDecrypterFactory(final JWEDecrypterFactory factory) {

                jweDecrypterFactory = factory;
        }


        @Override
        public Payload process(final String compactJOSE, final C context)
                throws ParseException, BadJOSEException, JOSEException {

                return process(JOSEObject.parse(compactJOSE), context);
        }


        @Override
        public Payload process(final JOSEObject joseObject, final C context)
                throws BadJOSEException, JOSEException {

                if (joseObject instanceof JWSObject) {
                        return process((JWSObject)joseObject, context);
                }

                if (joseObject instanceof JWEObject) {
                        return process((JWEObject)joseObject, context);
                }

                if (joseObject instanceof PlainObject) {
                        return process((PlainObject)joseObject, context);
                }

                // Should never happen
                throw new JOSEException("Unexpected JOSE object type: " + joseObject.getClass());
        }


        @Override
        public Payload process(final PlainObject plainObject, C context)
                throws BadJOSEException {

                throw PLAIN_JOSE_REJECTED_EXCEPTION;
        }


        @Override
        public Payload process(final JWSObject jwsObject, C context)
                throws BadJOSEException, JOSEException {

                if (getJWSKeySelector() == null) {
                        // JWS key selector may have been deliberately omitted
                        throw NO_JWS_KEY_SELECTOR_EXCEPTION;
                }

                if (getJWSVerifierFactory() == null) {
                        throw NO_JWS_VERIFIER_FACTORY_EXCEPTION;
                }

                List<? extends Key> keyCandidates = getJWSKeySelector().selectJWSKeys(jwsObject.getHeader(), context);

                if (keyCandidates == null || keyCandidates.isEmpty()) {
                        throw NO_JWS_KEY_CANDIDATES_EXCEPTION;
                }

                ListIterator<? extends Key> it = keyCandidates.listIterator();

                while (it.hasNext()) {

                        JWSVerifier verifier = getJWSVerifierFactory().createJWSVerifier(jwsObject.getHeader(), it.next());

                        if (verifier == null) {
                                continue;
                        }

                        final boolean validSignature = jwsObject.verify(verifier);

                        if (validSignature) {
                                return jwsObject.getPayload();
                        }

                        if (! it.hasNext()) {
                                // No more keys to try out
                                throw INVALID_SIGNATURE;
                        }
                }

                throw NO_MATCHING_VERIFIERS_EXCEPTION;
        }


        @Override
        public Payload process(final JWEObject jweObject, C context)
                throws BadJOSEException, JOSEException {

                if (getJWEKeySelector() == null) {
                        // JWE key selector may have been deliberately omitted
                        throw NO_JWE_KEY_SELECTOR_EXCEPTION;
                }

                if (getJWEDecrypterFactory() == null) {
                        throw NO_JWE_DECRYPTER_FACTORY_EXCEPTION;
                }

                List<? extends Key> keyCandidates = getJWEKeySelector().selectJWEKeys(jweObject.getHeader(), context);

                if (keyCandidates == null || keyCandidates.isEmpty()) {
                        throw NO_JWE_KEY_CANDIDATES_EXCEPTION;
                }

                ListIterator<? extends Key> it = keyCandidates.listIterator();

                while (it.hasNext()) {

                        JWEDecrypter decrypter = getJWEDecrypterFactory().createJWEDecrypter(jweObject.getHeader(), it.next());

                        if (decrypter == null) {
                                continue;
                        }

                        try {
                                jweObject.decrypt(decrypter);

                        } catch (JOSEException e) {

                                if (it.hasNext()) {
                                        // Try next key
                                        continue;
                                }

                                // No more keys to try
                                throw new BadJWEException("JWE object rejected: " + e.getMessage(), e);
                        }

                        if ("JWT".equalsIgnoreCase(jweObject.getHeader().getContentType())) {

                                // Handle nested signed JWT, see http://tools.ietf.org/html/rfc7519#section-5.2
                                JWSObject nestedJWS = jweObject.getPayload().toJWSObject();

                                if (nestedJWS == null) {
                                        // Cannot parse payload to JWS object, return original form
                                        return jweObject.getPayload();
                                }

                                return process(nestedJWS, context);
                        }

                        return jweObject.getPayload();
                }

                throw NO_MATCHING_DECRYPTERS_EXCEPTION;
        }
}