/*
 * nimbus-jose-jwt
 *
 * Copyright 2012-2016, Connect2id Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use
 * this file except in compliance with the License. You may obtain a copy of the
 * License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed
 * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */

package com.nimbusds.jose;


import java.net.URI;
import java.text.ParseException;
import java.util.*;

import net.jcip.annotations.Immutable;

import net.minidev.json.JSONObject;

import com.nimbusds.jose.jwk.JWK;
import com.nimbusds.jose.util.Base64;
import com.nimbusds.jose.util.Base64URL;
import com.nimbusds.jose.util.JSONObjectUtils;
import com.nimbusds.jose.util.X509CertChainUtils;


/**
 * JSON Web Encryption (JWE) header. This class is immutable.
 *
 * <p>Supports all {@link #getRegisteredParameterNames registered header
 * parameters} of the JWE specification:
 *
 * <ul>
 *     <li>alg
 *     <li>enc
 *     <li>epk
 *     <li>zip
 *     <li>jku
 *     <li>jwk
 *     <li>x5u
 *     <li>x5t
 *     <li>x5t#S256
 *     <li>x5c
 *     <li>kid
 *     <li>typ
 *     <li>cty
 *     <li>crit
 *     <li>apu
 *     <li>apv
 *     <li>p2s
 *     <li>p2c
 *     <li>iv
 *     <li>authTag
 * </ul>
 *
 * <p>The header may also include {@link #getCustomParams custom
 * parameters}; these will be serialised and parsed along the registered ones.
 *
 * <p>Example header:
 *
 * <pre>
 * { 
 *   "alg" : "RSA1_5",
 *   "enc" : "A128CBC-HS256"
 * }
 * </pre>
 *
 * @author Vladimir Dzhuvinov
 * @version 2017-04-09
 */
@Immutable
public final class JWEHeader extends CommonSEHeader {


        private static final long serialVersionUID = 1L;


        /**
         * The registered parameter names.
         */
        private static final Set<String> REGISTERED_PARAMETER_NAMES;


        /**
         * Initialises the registered parameter name set.
         */
        static {
                Set<String> p = new HashSet<>();

                p.add("alg");
                p.add("enc");
                p.add("epk");
                p.add("zip");
                p.add("jku");
                p.add("jwk");
                p.add("x5u");
                p.add("x5t");
                p.add("x5t#S256");
                p.add("x5c");
                p.add("kid");
                p.add("typ");
                p.add("cty");
                p.add("crit");
                p.add("apu");
                p.add("apv");
                p.add("p2s");
                p.add("p2c");
                p.add("iv");
                p.add("authTag");

                REGISTERED_PARAMETER_NAMES = Collections.unmodifiableSet(p);
        }


        /**
         * Builder for constructing JSON Web Encryption (JWE) headers.
         *
         * <p>Example usage:
         *
         * <pre>
         * JWEHeader header = new JWEHeader.Builder(JWEAlgorithm.RSA1_5, EncryptionMethod.A128GCM).
         *                    contentType("text/plain").
         *                    customParam("exp", new Date().getTime()).
         *                    build();
         * </pre>
         */
        public static class Builder {


                /**
                 * The JWE algorithm.
                 */
                private final JWEAlgorithm alg;


                /**
                 * The encryption method.
                 */
                private final EncryptionMethod enc;


                /**
                 * The JOSE object type.
                 */
                private JOSEObjectType typ;


                /**
                 * The content type.
                 */
                private String cty;


                /**
                 * The critical headers.
                 */
                private Set<String> crit;


                /**
                 * JWK Set URL.
                 */
                private URI jku;


                /**
                 * JWK.
                 */
                private JWK jwk;


                /**
                 * X.509 certificate URL.
                 */
                private URI x5u;


                /**
                 * X.509 certificate SHA-1 thumbprint.
                 */
                @Deprecated
                private Base64URL x5t;


                /**
                 * X.509 certificate SHA-256 thumbprint.
                 */
                private Base64URL x5t256;


                /**
                 * The X.509 certificate chain corresponding to the key used to
                 * sign the JWS object.
                 */
                private List<Base64> x5c;


                /**
                 * Key ID.
                 */
                private String kid;


                /**
                 * The ephemeral public key.
                 */
                private JWK epk;


                /**
                 * The compression algorithm.
                 */
                private CompressionAlgorithm zip;


                /**
                 * The agreement PartyUInfo.
                 */
                private Base64URL apu;


                /**
                 * The agreement PartyVInfo.
                 */
                private Base64URL apv;


                /**
                 * The PBES2 salt.
                 */
                private Base64URL p2s;


                /**
                 * The PBES2 count.
                 */
                private int p2c;


                /**
                 * The initialisation vector.
                 */
                private Base64URL iv;


                /**
                 * The authentication authTag.
                 */
                private Base64URL tag;


                /**
                 * Custom header parameters.
                 */
                private Map<String,Object> customParams;


                /**
                 * The parsed Base64URL.
                 */
                private Base64URL parsedBase64URL;


                /**
                 * Creates a new JWE header builder.
                 *
                 * @param alg The JWE algorithm ({@code alg}) parameter. Must
                 *            not be "none" or {@code null}.
                 * @param enc The encryption method. Must not be {@code null}.
                 */
                public Builder(final JWEAlgorithm alg, final EncryptionMethod enc) {

                        if (alg.getName().equals(Algorithm.NONE.getName())) {
                                throw new IllegalArgumentException("The JWE algorithm \"alg\" cannot be \"none\"");
                        }

                        this.alg = alg;

                        if (enc == null) {
                                throw new IllegalArgumentException("The encryption method \"enc\" parameter must not be null");
                        }

                        this.enc = enc;
                }


                /**
                 * Creates a new JWE header builder with the parameters from
                 * the specified header.
                 *
                 * @param jweHeader The JWE header to use. Must not not be 
                 *                  {@code null}.              
                 */
                public Builder(final JWEHeader jweHeader) {

                        this(jweHeader.getAlgorithm(), jweHeader.getEncryptionMethod());

                        typ = jweHeader.getType();
                        cty = jweHeader.getContentType();
                        crit = jweHeader.getCriticalParams();
                        customParams = jweHeader.getCustomParams();

                        jku = jweHeader.getJWKURL();
                        jwk = jweHeader.getJWK();
                        x5u = jweHeader.getX509CertURL();
                        x5t = jweHeader.getX509CertThumbprint();
                        x5t256 = jweHeader.getX509CertSHA256Thumbprint();
                        x5c = jweHeader.getX509CertChain();
                        kid = jweHeader.getKeyID();

                        epk = jweHeader.getEphemeralPublicKey();
                        zip = jweHeader.getCompressionAlgorithm();
                        apu = jweHeader.getAgreementPartyUInfo();
                        apv = jweHeader.getAgreementPartyVInfo();
                        p2s = jweHeader.getPBES2Salt();
                        p2c = jweHeader.getPBES2Count();
                        iv = jweHeader.getIV();
                        tag = jweHeader.getAuthTag();

                        customParams = jweHeader.getCustomParams();
                }


                /**
                 * Sets the type ({@code typ}) parameter.
                 *
                 * @param typ The type parameter, {@code null} if not
                 *            specified.
                 *
                 * @return This builder.
                 */
                public Builder type(final JOSEObjectType typ) {

                        this.typ = typ;
                        return this;
                }


                /**
                 * Sets the content type ({@code cty}) parameter.
                 *
                 * @param cty The content type parameter, {@code null} if not
                 *            specified.
                 *
                 * @return This builder.
                 */
                public Builder contentType(final String cty) {

                        this.cty = cty;
                        return this;
                }


                /**
                 * Sets the critical header parameters ({@code crit})
                 * parameter.
                 *
                 * @param crit The names of the critical header parameters,
                 *             empty set or {@code null} if none.
                 *
                 * @return This builder.
                 */
                public Builder criticalParams(final Set<String> crit) {

                        this.crit = crit;
                        return this;
                }


                /**
                 * Sets the JSON Web Key (JWK) Set URL ({@code jku}) parameter.
                 *
                 * @param jku The JSON Web Key (JWK) Set URL parameter,
                 *            {@code null} if not specified.
                 *
                 * @return This builder.
                 */
                public Builder jwkURL(final URI jku) {

                        this.jku = jku;
                        return this;
                }


                /**
                 * Sets the JSON Web Key (JWK) ({@code jwk}) parameter.
                 *
                 * @param jwk The JSON Web Key (JWK) ({@code jwk}) parameter,
                 *            {@code null} if not specified.
                 *
                 * @return This builder.
                 */
                public Builder jwk(final JWK jwk) {

                        this.jwk = jwk;
                        return this;
                }


                /**
                 * Sets the X.509 certificate URL ({@code x5u}) parameter.
                 *
                 * @param x5u The X.509 certificate URL parameter, {@code null}
                 *            if not specified.
                 *
                 * @return This builder.
                 */
                public Builder x509CertURL(final URI x5u) {

                        this.x5u = x5u;
                        return this;
                }


                /**
                 * Sets the X.509 certificate SHA-1 thumbprint ({@code x5t})
                 * parameter.
                 *
                 * @param x5t The X.509 certificate SHA-1 thumbprint parameter,
                 *            {@code null} if not specified.
                 *
                 * @return This builder.
                 */
                @Deprecated
                public Builder x509CertThumbprint(final Base64URL x5t) {

                        this.x5t = x5t;
                        return this;
                }


                /**
                 * Sets the X.509 certificate SHA-256 thumbprint
                 * ({@code x5t#s256}) parameter.
                 *
                 * @param x5t256 The X.509 certificate SHA-256 thumbprint
                 *               parameter, {@code null} if not specified.
                 *
                 * @return This builder.
                 */
                public Builder x509CertSHA256Thumbprint(final Base64URL x5t256) {

                        this.x5t256 = x5t256;
                        return this;
                }


                /**
                 * Sets the X.509 certificate chain parameter ({@code x5c})
                 * corresponding to the key used to sign the JWS object.
                 *
                 * @param x5c The X.509 certificate chain parameter,
                 *            {@code null} if not specified.
                 *
                 * @return This builder.
                 */
                public Builder x509CertChain(final List<Base64> x5c) {

                        this.x5c = x5c;
                        return this;
                }


                /**
                 * Sets the key ID ({@code kid}) parameter.
                 *
                 * @param kid The key ID parameter, {@code null} if not
                 *            specified.
                 *
                 * @return This builder.
                 */
                public Builder keyID(final String kid) {

                        this.kid = kid;
                        return this;
                }


                /**
                 * Sets the Ephemeral Public Key ({@code epk}) parameter.
                 *
                 * @param epk The Ephemeral Public Key parameter, {@code null}
                 *            if not specified.
                 *
                 * @return This builder.
                 */
                public Builder ephemeralPublicKey(final JWK epk) {

                        this.epk = epk;
                        return this;
                }


                /**
                 * Sets the compression algorithm ({@code zip}) parameter.
                 *
                 * @param zip The compression algorithm parameter, {@code null}
                 *            if not specified.
                 *
                 * @return This builder.
                 */
                public Builder compressionAlgorithm(final CompressionAlgorithm zip) {

                        this.zip = zip;
                        return this;
                }


                /**
                 * Sets the agreement PartyUInfo ({@code apu}) parameter.
                 *
                 * @param apu The agreement PartyUInfo parameter, {@code null}
                 *            if not specified.
                 *
                 * @return This builder.
                 */
                public Builder agreementPartyUInfo(final Base64URL apu) {

                        this.apu = apu;
                        return this;
                }


                /**
                 * Sets the agreement PartyVInfo ({@code apv}) parameter.
                 *
                 * @param apv The agreement PartyVInfo parameter, {@code null}
                 *            if not specified.
                 *
                 * @return This builder.
                 */
                public Builder agreementPartyVInfo(final Base64URL apv) {

                        this.apv = apv;
                        return this;
                }


                /**
                 * Sets the PBES2 salt ({@code p2s}) parameter.
                 *
                 * @param p2s The PBES2 salt parameter, {@code null} if not
                 *            specified.
                 *
                 * @return This builder.
                 */
                public Builder pbes2Salt(final Base64URL p2s) {

                        this.p2s = p2s;
                        return this;
                }


                /**
                 * Sets the PBES2 count ({@code p2c}) parameter.
                 *
                 * @param p2c The PBES2 count parameter, zero if not specified.
                 *            Must not be negative.
                 *
                 * @return This builder.
                 */
                public Builder pbes2Count(final int p2c) {

                        if (p2c < 0)
                                throw new IllegalArgumentException("The PBES2 count parameter must not be negative");

                        this.p2c = p2c;
                        return this;
                }


                /**
                 * Sets the initialisation vector ({@code iv}) parameter.
                 *
                 * @param iv The initialisation vector, {@code null} if not
                 *           specified.
                 *
                 * @return This builder.
                 */
                public Builder iv(final Base64URL iv) {

                        this.iv = iv;
                        return this;
                }


                /**
                 * Sets the authentication tag ({@code tag}) parameter.
                 *
                 * @param tag The authentication tag, {@code null} if not
                 *            specified.
                 *
                 * @return This builder.
                 */
                public Builder authTag(final Base64URL tag) {

                        this.tag = tag;
                        return this;
                }


                /**
                 * Sets a custom (non-registered) parameter.
                 *
                 * @param name  The name of the custom parameter. Must not
                 *              match a registered parameter name and must not
                 *              be {@code null}.
                 * @param value The value of the custom parameter, should map
                 *              to a valid JSON entity, {@code null} if not
                 *              specified.
                 *
                 * @return This builder.
                 *
                 * @throws IllegalArgumentException If the specified parameter
                 *                                  name matches a registered
                 *                                  parameter name.
                 */
                public Builder customParam(final String name, final Object value) {

                        if (getRegisteredParameterNames().contains(name)) {
                                throw new IllegalArgumentException("The parameter name \"" + name + "\" matches a registered name");
                        }

                        if (customParams == null) {
                                customParams = new HashMap<>();
                        }

                        customParams.put(name, value);

                        return this;
                }


                /**
                 * Sets the custom (non-registered) parameters. The values must
                 * be serialisable to a JSON entity, otherwise will be ignored.
                 *
                 * @param customParameters The custom parameters, empty map or
                 *                         {@code null} if none.
                 *
                 * @return This builder.
                 */
                public Builder customParams(final Map<String, Object> customParameters) {

                        this.customParams = customParameters;
                        return this;
                }


                /**
                 * Sets the parsed Base64URL.
                 *
                 * @param base64URL The parsed Base64URL, {@code null} if the
                 *                  header is created from scratch.
                 *
                 * @return This builder.
                 */
                public Builder parsedBase64URL(final Base64URL base64URL) {

                        this.parsedBase64URL = base64URL;
                        return this;
                }


                /**
                 * Builds a new JWE header.
                 *
                 * @return The JWE header.
                 */
                public JWEHeader build() {

                        return new JWEHeader(
                                alg, enc, typ, cty, crit,
                                jku, jwk, x5u, x5t, x5t256, x5c, kid,
                                epk, zip, apu, apv, p2s, p2c,
                                iv, tag,
                                customParams, parsedBase64URL);
                }
        }


        /**
         * The encryption method ({@code enc}) parameter.
         */
        private final EncryptionMethod enc;


        /**
         * The ephemeral public key ({@code epk}) parameter.
         */
        private final JWK epk;


        /**
         * The compression algorithm ({@code zip}) parameter.
         */
        private final CompressionAlgorithm zip;


        /**
         * The agreement PartyUInfo ({@code apu}) parameter.
         */
        private final Base64URL apu;
        
        
        /**
         * The agreement PartyVInfo ({@code apv}) parameter.
         */
        private final Base64URL apv;


        /**
         * The PBES2 salt ({@code p2s}) parameter.
         */
        private final Base64URL p2s;


        /**
         * The PBES2 count ({@code p2c}) parameter.
         */
        private final int p2c;


        /**
         * The initialisation vector ({@code iv}) parameter.
         */
        private final Base64URL iv;


        /**
         * The authentication tag ({@code tag}) parameter.
         */
        private final Base64URL tag;


        /**
         * Creates a new minimal JSON Web Encryption (JWE) header.
         *
         * <p>Note: Use {@link PlainHeader} to create a header with algorithm
         * {@link Algorithm#NONE none}.
         *
         * @param alg The JWE algorithm parameter. Must not be "none" or
         *            {@code null}.
         * @param enc The encryption method parameter. Must not be 
         *            {@code null}.
         */
        public JWEHeader(final JWEAlgorithm alg, final EncryptionMethod enc) {

                this(
                        alg, enc,
                        null, null, null, null, null, null, null, null, null, null,
                        null, null, null, null, null, 0,
                        null, null,
                        null, null);
        }


        /**
         * Creates a new JSON Web Encryption (JWE) header.
         *
         * <p>Note: Use {@link PlainHeader} to create a header with algorithm
         * {@link Algorithm#NONE none}.
         *
         * @param alg             The JWE algorithm ({@code alg}) parameter.
         *                        Must not be "none" or {@code null}.
         * @param enc             The encryption method parameter. Must not be
         *                        {@code null}.
         * @param typ             The type ({@code typ}) parameter,
         *                        {@code null} if not specified.
         * @param cty             The content type ({@code cty}) parameter,
         *                        {@code null} if not specified.
         * @param crit            The names of the critical header
         *                        ({@code crit}) parameters, empty set or
         *                        {@code null} if none.
         * @param jku             The JSON Web Key (JWK) Set URL ({@code jku})
         *                        parameter, {@code null} if not specified.
         * @param jwk             The X.509 certificate URL ({@code jwk})
         *                        parameter, {@code null} if not specified.
         * @param x5u             The X.509 certificate URL parameter
         *                        ({@code x5u}), {@code null} if not specified.
         * @param x5t             The X.509 certificate SHA-1 thumbprint
         *                        ({@code x5t}) parameter, {@code null} if not
         *                        specified.
         * @param x5t256          The X.509 certificate SHA-256 thumbprint
         *                        ({@code x5t#S256}) parameter, {@code null} if
         *                        not specified.
         * @param x5c             The X.509 certificate chain ({@code x5c})
         *                        parameter, {@code null} if not specified.
         * @param kid             The key ID ({@code kid}) parameter,
         *                        {@code null} if not specified.
         * @param epk             The Ephemeral Public Key ({@code epk})
         *                        parameter, {@code null} if not specified.
         * @param zip             The compression algorithm ({@code zip})
         *                        parameter, {@code null} if not specified.
         * @param apu             The agreement PartyUInfo ({@code apu})
         *                        parameter, {@code null} if not specified.
         * @param apv             The agreement PartyVInfo ({@code apv})
         *                        parameter, {@code null} if not specified.
         * @param p2s             The PBES2 salt ({@code p2s}) parameter,
         *                        {@code null} if not specified.
         * @param p2c             The PBES2 count ({@code p2c}) parameter, zero
         *                        if not specified. Must not be negative.
         * @param iv              The initialisation vector ({@code iv})
         *                        parameter, {@code null} if not specified.
         * @param tag             The authentication tag ({@code tag})
         *                        parameter, {@code null} if not specified.
         * @param customParams    The custom parameters, empty map or
         *                        {@code null} if none.
         * @param parsedBase64URL The parsed Base64URL, {@code null} if the
         *                        header is created from scratch.
         */
        public JWEHeader(final Algorithm alg,
                         final EncryptionMethod enc,
                         final JOSEObjectType typ,
                         final String cty,
                         final Set<String> crit,
                         final URI jku,
                         final JWK jwk,
                         final URI x5u,
                         final Base64URL x5t,
                         final Base64URL x5t256,
                         final List<Base64> x5c,
                         final String kid,
                         final JWK epk,
                         final CompressionAlgorithm zip,
                         final Base64URL apu,
                         final Base64URL apv,
                         final Base64URL p2s,
                         final int p2c,
                         final Base64URL iv,
                         final Base64URL tag,
                         final Map<String,Object> customParams,
                         final Base64URL parsedBase64URL) {

                super(alg, typ, cty, crit, jku, jwk, x5u, x5t, x5t256, x5c, kid, customParams, parsedBase64URL);

                if (alg.getName().equals(Algorithm.NONE.getName())) {
                        throw new IllegalArgumentException("The JWE algorithm cannot be \"none\"");
                }

                if (enc == null) {
                        throw new IllegalArgumentException("The encryption method \"enc\" parameter must not be null");
                }

                if (epk != null && epk.isPrivate()) {
                        throw new IllegalArgumentException("Ephemeral public key should not be a private key");
                }

                this.enc = enc;

                this.epk = epk;
                this.zip = zip;
                this.apu = apu;
                this.apv = apv;
                this.p2s = p2s;
                this.p2c = p2c;
                this.iv = iv;
                this.tag = tag;
        }


        /**
         * Deep copy constructor.
         *
         * @param jweHeader The JWE header to copy. Must not be {@code null}.
         */
        public JWEHeader(final JWEHeader jweHeader) {

                this(
                        jweHeader.getAlgorithm(),
                        jweHeader.getEncryptionMethod(),
                        jweHeader.getType(),
                        jweHeader.getContentType(),
                        jweHeader.getCriticalParams(),
                        jweHeader.getJWKURL(),
                        jweHeader.getJWK(),
                        jweHeader.getX509CertURL(),
                        jweHeader.getX509CertThumbprint(),
                        jweHeader.getX509CertSHA256Thumbprint(),
                        jweHeader.getX509CertChain(),
                        jweHeader.getKeyID(),
                        jweHeader.getEphemeralPublicKey(),
                        jweHeader.getCompressionAlgorithm(),
                        jweHeader.getAgreementPartyUInfo(),
                        jweHeader.getAgreementPartyVInfo(),
                        jweHeader.getPBES2Salt(),
                        jweHeader.getPBES2Count(),
                        jweHeader.getIV(),
                        jweHeader.getAuthTag(),
                        jweHeader.getCustomParams(),
                        jweHeader.getParsedBase64URL()
                );
        }


        /**
         * Gets the registered parameter names for JWE headers.
         *
         * @return The registered parameter names, as an unmodifiable set.
         */
        public static Set<String> getRegisteredParameterNames() {

                return REGISTERED_PARAMETER_NAMES;
        }


        /**
         * Gets the algorithm ({@code alg}) parameter.
         *
         * @return The algorithm parameter.
         */
        public JWEAlgorithm getAlgorithm() {

                return (JWEAlgorithm)super.getAlgorithm();
        }


        /**
         * Gets the encryption method ({@code enc}) parameter.
         *
         * @return The encryption method parameter.
         */
        public EncryptionMethod getEncryptionMethod() {

                return enc;
        }


        /**
         * Gets the Ephemeral Public Key ({@code epk}) parameter.
         *
         * @return The Ephemeral Public Key parameter, {@code null} if not
         *         specified.
         */
        public JWK getEphemeralPublicKey() {

                return epk;
        }


        /**
         * Gets the compression algorithm ({@code zip}) parameter.
         *
         * @return The compression algorithm parameter, {@code null} if not
         *         specified.
         */
        public CompressionAlgorithm getCompressionAlgorithm() {

                return zip;
        }


        /**
         * Gets the agreement PartyUInfo ({@code apu}) parameter.
         *
         * @return The agreement PartyUInfo parameter, {@code null} if not
         *         specified.
         */
        public Base64URL getAgreementPartyUInfo() {

                return apu;
        }


        /**
         * Gets the agreement PartyVInfo ({@code apv}) parameter.
         *
         * @return The agreement PartyVInfo parameter, {@code null} if not
         *         specified.
         */
        public Base64URL getAgreementPartyVInfo() {

                return apv;
        }


        /**
         * Gets the PBES2 salt ({@code p2s}) parameter.
         *
         * @return The PBES2 salt parameter, {@code null} if not specified.
         */
        public Base64URL getPBES2Salt() {

                return p2s;
        }


        /**
         * Gets the PBES2 count ({@code p2c}) parameter.
         *
         * @return The PBES2 count parameter, zero if not specified.
         */
        public int getPBES2Count() {

                return p2c;
        }


        /**
         * Gets the initialisation vector ({@code iv}) parameter.
         *
         * @return The initialisation vector, {@code null} if not specified.
         */
        public Base64URL getIV() {

                return iv;
        }


        /**
         * Gets the authentication tag ({@code tag}) parameter.
         *
         * @return The authentication tag, {@code null} if not specified.
         */
        public Base64URL getAuthTag() {

                return tag;
        }


        @Override
        public Set<String> getIncludedParams() {

                Set<String> includedParameters = super.getIncludedParams();

                if (enc != null) {
                        includedParameters.add("enc");
                }

                if (epk != null) {
                        includedParameters.add("epk");
                }

                if (zip != null) {
                        includedParameters.add("zip");
                }

                if (apu != null) {
                        includedParameters.add("apu");
                }
                
                if (apv != null) {
                        includedParameters.add("apv");
                }

                if (p2s != null) {
                        includedParameters.add("p2s");
                }

                if (p2c > 0) {
                        includedParameters.add("p2c");
                }

                if (iv != null) {
                        includedParameters.add("iv");
                }

                if (tag != null) {
                        includedParameters.add("tag");
                }

                return includedParameters;
        }


        @Override
        public JSONObject toJSONObject() {

                JSONObject o = super.toJSONObject();

                if (enc != null) {
                        o.put("enc", enc.toString());
                }

                if (epk != null) {
                        o.put("epk", epk.toJSONObject());
                }

                if (zip != null) {
                        o.put("zip", zip.toString());
                }

                if (apu != null) {
                        o.put("apu", apu.toString());
                }
                
                if (apv != null) {
                        o.put("apv", apv.toString());
                }

                if (p2s != null) {
                        o.put("p2s", p2s.toString());
                }

                if (p2c > 0) {
                        o.put("p2c", p2c);
                }

                if (iv != null) {
                        o.put("iv", iv.toString());
                }

                if (tag != null) {
                        o.put("tag", tag.toString());
                }

                return o;
        }


        /**
         * Parses an encryption method ({@code enc}) parameter from the 
         * specified JWE header JSON object.
         *
         * @param json The JSON object to parse. Must not be {@code null}.
         *
         * @return The encryption method.
         *
         * @throws ParseException If the {@code enc} parameter couldn't be 
         *                        parsed.
         */
        private static EncryptionMethod parseEncryptionMethod(final JSONObject json)
                throws ParseException {

                return EncryptionMethod.parse(JSONObjectUtils.getString(json, "enc"));
        }


        /**
         * Parses a JWE header from the specified JSON object.
         *
         * @param jsonObject The JSON object to parse. Must not be
         *                   {@code null}.
         *
         * @return The JWE header.
         *
         * @throws ParseException If the specified JSON object doesn't
         *                        represent a valid JWE header.
         */
        public static JWEHeader parse(final JSONObject jsonObject)
                throws ParseException {

                return parse(jsonObject, null);
        }


        /**
         * Parses a JWE header from the specified JSON object.
         *
         * @param jsonObject      The JSON object to parse. Must not be
         *                        {@code null}.
         * @param parsedBase64URL The original parsed Base64URL, {@code null}
         *                        if not applicable.
         *
         * @return The JWE header.
         *
         * @throws ParseException If the specified JSON object doesn't 
         *                        represent a valid JWE header.
         */
        public static JWEHeader parse(final JSONObject jsonObject,
                                      final Base64URL parsedBase64URL)
                throws ParseException {

                // Get the "alg" parameter
                Algorithm alg = Header.parseAlgorithm(jsonObject);

                if (! (alg instanceof JWEAlgorithm)) {
                        throw new ParseException("The algorithm \"alg\" header parameter must be for encryption", 0);
                }

                // Get the "enc" parameter
                EncryptionMethod enc = parseEncryptionMethod(jsonObject);

                JWEHeader.Builder header = new Builder((JWEAlgorithm)alg, enc).parsedBase64URL(parsedBase64URL);

                // Parse optional + custom parameters
                for(final String name: jsonObject.keySet()) {

                        if("alg".equals(name)) {
                                // skip
                        } else if("enc".equals(name)) {
                                // skip
                        } else if("typ".equals(name)) {
                                header = header.type(new JOSEObjectType(JSONObjectUtils.getString(jsonObject, name)));
                        } else if("cty".equals(name)) {
                                header = header.contentType(JSONObjectUtils.getString(jsonObject, name));
                        } else if("crit".equals(name)) {
                                header = header.criticalParams(new HashSet<>(JSONObjectUtils.getStringList(jsonObject, name)));
                        } else if("jku".equals(name)) {
                                header = header.jwkURL(JSONObjectUtils.getURI(jsonObject, name));
                        } else if("jwk".equals(name)) {
                                header = header.jwk(JWK.parse(JSONObjectUtils.getJSONObject(jsonObject, name)));
                        } else if("x5u".equals(name)) {
                                header = header.x509CertURL(JSONObjectUtils.getURI(jsonObject, name));
                        } else if("x5t".equals(name)) {
                                header = header.x509CertThumbprint(new Base64URL(JSONObjectUtils.getString(jsonObject, name)));
                        } else if("x5t#S256".equals(name)) {
                                header = header.x509CertSHA256Thumbprint(new Base64URL(JSONObjectUtils.getString(jsonObject, name)));
                        } else if("x5c".equals(name)) {
                                header = header.x509CertChain(X509CertChainUtils.toBase64List(JSONObjectUtils.getJSONArray(jsonObject, name)));
                        } else if("kid".equals(name)) {
                                header = header.keyID(JSONObjectUtils.getString(jsonObject, name));
                        } else if("epk".equals(name)) {
                                header = header.ephemeralPublicKey(JWK.parse(JSONObjectUtils.getJSONObject(jsonObject, name)));
                        } else if("zip".equals(name)) {
                                header = header.compressionAlgorithm(new CompressionAlgorithm(JSONObjectUtils.getString(jsonObject, name)));
                        } else if("apu".equals(name)) {
                                header = header.agreementPartyUInfo(new Base64URL(JSONObjectUtils.getString(jsonObject, name)));
                        } else if("apv".equals(name)) {
                                header = header.agreementPartyVInfo(new Base64URL(JSONObjectUtils.getString(jsonObject, name)));
                        } else if("p2s".equals(name)) {
                                header = header.pbes2Salt(new Base64URL(JSONObjectUtils.getString(jsonObject, name)));
                        } else if("p2c".equals(name)) {
                                header = header.pbes2Count(JSONObjectUtils.getInt(jsonObject, name));
                        } else if("iv".equals(name)) {
                                header = header.iv(new Base64URL(JSONObjectUtils.getString(jsonObject, name)));
                        } else if("tag".equals(name)) {
                                header = header.authTag(new Base64URL(JSONObjectUtils.getString(jsonObject, name)));
                        } else {
                                header = header.customParam(name, jsonObject.get(name));
                        }
                }

                return header.build();
        }


        /**
         * Parses a JWE header from the specified JSON object string.
         *
         * @param jsonString The JSON object string to parse. Must not be {@code null}.
         *
         * @return The JWE header.
         *
         * @throws ParseException If the specified JSON object string doesn't 
         *                        represent a valid JWE header.
         */
        public static JWEHeader parse(final String jsonString)
                throws ParseException {

                return parse(JSONObjectUtils.parse(jsonString), null);
        }


        /**
         * Parses a JWE header from the specified JSON object string.
         *
         * @param jsonString      The JSON string to parse. Must not be
         *                        {@code null}.
         * @param parsedBase64URL The original parsed Base64URL, {@code null}
         *                        if not applicable.
         *
         * @return The JWE header.
         *
         * @throws ParseException If the specified JSON object string doesn't
         *                        represent a valid JWE header.
         */
        public static JWEHeader parse(final String jsonString,
                                      final Base64URL parsedBase64URL)
                throws ParseException {

                return parse(JSONObjectUtils.parse(jsonString), parsedBase64URL);
        }


        /**
         * Parses a JWE header from the specified Base64URL.
         *
         * @param base64URL The Base64URL to parse. Must not be {@code null}.
         *
         * @return The JWE header.
         *
         * @throws ParseException If the specified Base64URL doesn't represent
         *                        a valid JWE header.
         */
        public static JWEHeader parse(final Base64URL base64URL)
                throws ParseException {

                return parse(base64URL.decodeToString(), base64URL);
        }
}