/*
 * oauth2-oidc-sdk
 *
 * Copyright 2012-2016, Connect2id Ltd and contributors.
 *
 * 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.oauth2.sdk.client;


import java.net.URI;
import java.net.URISyntaxException;
import java.util.*;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;

import com.nimbusds.jose.JWSAlgorithm;
import com.nimbusds.jose.jwk.JWKSet;
import com.nimbusds.langtag.LangTag;
import com.nimbusds.langtag.LangTagUtils;
import com.nimbusds.oauth2.sdk.GrantType;
import com.nimbusds.oauth2.sdk.ParseException;
import com.nimbusds.oauth2.sdk.ResponseType;
import com.nimbusds.oauth2.sdk.Scope;
import com.nimbusds.oauth2.sdk.auth.ClientAuthenticationMethod;
import com.nimbusds.oauth2.sdk.id.SoftwareID;
import com.nimbusds.oauth2.sdk.id.SoftwareVersion;
import com.nimbusds.oauth2.sdk.util.JSONObjectUtils;
import net.minidev.json.JSONArray;
import net.minidev.json.JSONObject;


/**
 * Client metadata.
 * 
 * <p>Example client metadata, serialised to a JSON object:
 * 
 * <pre>
 * {
 *  "redirect_uris"              : ["https://client.example.org/callback",
 *                                  "https://client.example.org/callback2"],
 *  "client_name"                : "My Example Client",
 *  "client_name#ja-Jpan-JP"     : "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D",
 *  "token_endpoint_auth_method" : "client_secret_basic",
 *  "scope"                      : "read write dolphin",
 *  "logo_uri"                   : "https://client.example.org/logo.png",
 *  "jwks_uri"                   : "https://client.example.org/my_public_keys.jwks"
 * }
 * </pre>
 * 
 * <p>Related specifications:
 *
 * <ul>
 *     <li>OAuth 2.0 Dynamic Client Registration Protocol (RFC 7591), section
 *         2.
 * </ul>
 */
public class ClientMetadata {


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


        static {
                Set<String> p = new HashSet<>();

                p.add("redirect_uris");
                p.add("scope");
                p.add("response_types");
                p.add("grant_types");
                p.add("contacts");
                p.add("client_name");
                p.add("logo_uri");
                p.add("client_uri");
                p.add("policy_uri");
                p.add("tos_uri");
                p.add("token_endpoint_auth_method");
                p.add("token_endpoint_auth_signing_alg");
                p.add("jwks_uri");
                p.add("jwks");
                p.add("software_id");
                p.add("software_version");

                REGISTERED_PARAMETER_NAMES = Collections.unmodifiableSet(p);
        }
        
        
        /**
         * Redirect URIs.
         */
        private Set<URI> redirectURIs;


        /**
         * The client OAuth 2.0 scope.
         */
        private Scope scope;


        /**
         * The expected OAuth 2.0 response types.
         */
        private Set<ResponseType> responseTypes;


        /**
         * The expected OAuth 2.0 grant types.
         */
        private Set<GrantType> grantTypes;


        /**
         * Administrator email contacts for the client.
         */
        private List<String> contacts;


        /**
         * The client name.
         */
        private final Map<LangTag,String> nameEntries;


        /**
         * The client application logo.
         */
        private final Map<LangTag,URI> logoURIEntries;


        /**
         * The client URI entries.
         */
        private final Map<LangTag,URI> uriEntries;


        /**
         * The client policy for use of end-user data.
         */
        private Map<LangTag,URI> policyURIEntries;


        /**
         * The client terms of service.
         */
        private final Map<LangTag,URI> tosURIEntries;


        /**
         * Token endpoint authentication method.
         */
        private ClientAuthenticationMethod authMethod;


        /**
         * The JSON Web Signature (JWS) algorithm required for
         * {@code private_key_jwt} and {@code client_secret_jwt}
         * authentication at the Token endpoint.
         */
        private JWSAlgorithm authJWSAlg;


        /**
         * URI for this client's JSON Web Key (JWK) set containing key(s) that
         * are used in signing requests to the server and key(s) for encrypting
         * responses.
         */
        private URI jwkSetURI;


        /**
         * Client's JSON Web Key (JWK) set containing key(s) that are used in
         * signing requests to the server and key(s) for encrypting responses.
         * Intended as an alternative to {@link #jwkSetURI} for native clients.
         */
        private JWKSet jwkSet;


        /**
         * Identifier for the OAuth 2.0 client software.
         */
        private SoftwareID softwareID;


        /**
         * Version identifier for the OAuth 2.0 client software.
         */
        private SoftwareVersion softwareVersion;


        /**
         * The custom metadata fields.
         */
        private JSONObject customFields;


        /**
         * Creates a new OAuth 2.0 client metadata instance.
         */
        public ClientMetadata() {

                nameEntries = new HashMap<>();
                logoURIEntries = new HashMap<>();
                uriEntries = new HashMap<>();
                policyURIEntries = new HashMap<>();
                policyURIEntries = new HashMap<>();
                tosURIEntries = new HashMap<>();
                customFields = new JSONObject();
        }


        /**
         * Creates a shallow copy of the specified OAuth 2.0 client metadata
         * instance.
         *
         * @param metadata The client metadata to copy. Must not be
         *                 {@code null}.
         */
        public ClientMetadata(final ClientMetadata metadata) {

                redirectURIs = metadata.redirectURIs;
                scope = metadata.scope;
                responseTypes = metadata.responseTypes;
                grantTypes = metadata.grantTypes;
                contacts = metadata.contacts;
                nameEntries = metadata.nameEntries;
                logoURIEntries = metadata.logoURIEntries;
                uriEntries = metadata.uriEntries;
                policyURIEntries = metadata.policyURIEntries;
                tosURIEntries = metadata.tosURIEntries;
                authMethod = metadata.authMethod;
                authJWSAlg = metadata.authJWSAlg;
                jwkSetURI = metadata.jwkSetURI;
                jwkSet = metadata.getJWKSet();
                softwareID = metadata.softwareID;
                softwareVersion = metadata.softwareVersion;
                customFields = metadata.customFields;
        }


        /**
         * Gets the registered (standard) OAuth 2.0 client metadata parameter
         * names.
         *
         * @return The registered parameter names, as an unmodifiable set.
         */
        public static Set<String> getRegisteredParameterNames() {

                return REGISTERED_PARAMETER_NAMES;
        }


        /**
         * Gets the redirection URIs for this client. Corresponds to the
         * {@code redirect_uris} client metadata field.
         *
         * @return The redirection URIs, {@code null} if not specified.
         */
        public Set<URI> getRedirectionURIs() {

                return redirectURIs;
        }


        /**
         * Gets the redirection URIs for this client as strings. Corresponds to
         * the {@code redirect_uris} client metadata field.
         *
         * <p>This short-hand method is intended to enable string-based URI
         * comparison.
         *
         * @return The redirection URIs as strings, {@code null} if not
         *         specified.
         */
        public Set<String> getRedirectionURIStrings() {

                if (redirectURIs == null)
                        return null;

                Set<String> uriStrings = new HashSet<>();

                for (URI uri: redirectURIs)
                        uriStrings.add(uri.toString());

                return uriStrings;
        }


        /**
         * Sets the redirection URIs for this client. Corresponds to the
         * {@code redirect_uris} client metadata field.
         *
         * @param redirectURIs The redirection URIs, {@code null} if not
         *                     specified. Valid redirection URIs must not
         *                     contain a fragment.
         */
        public void setRedirectionURIs(final Set<URI> redirectURIs) {

                if (redirectURIs != null) {
                        // check URIs
                        for (URI uri: redirectURIs) {
                                if (uri == null) {
                                        throw new IllegalArgumentException("The redirect_uri must not be null");
                                }
                                if (uri.getFragment() != null) {
                                        throw new IllegalArgumentException("The redirect_uri must not contain fragment");
                                }
                        }
                        this.redirectURIs = redirectURIs;
                } else {
                        this.redirectURIs = null;
                }
        }


        /**
         * Sets a single redirection URI for this client. Corresponds to the
         * {@code redirect_uris} client metadata field.
         *
         * @param redirectURI The redirection URIs, {@code null} if not
         *                    specified. A valid redirection URI must not
         *                    contain a fragment.
         */
        public void setRedirectionURI(final URI redirectURI) {

                setRedirectionURIs(redirectURI != null ? Collections.singleton(redirectURI) : null);
        }


        /**
         * Gets the scope values that the client can use when requesting access
         * tokens. Corresponds to the {@code scope} client metadata field.
         *
         * @return The scope, {@code null} if not specified.
         */
        public Scope getScope() {

                return scope;
        }


        /**
         * Checks if the scope matadata field is set and contains the specified
         * scope value.
         *
         * @param scopeValue The scope value. Must not be {@code null}.
         *
         * @return {@code true} if the scope value is contained, else
         *         {@code false}.
         */
        public boolean hasScopeValue(final Scope.Value scopeValue) {

                return scope != null && scope.contains(scopeValue);
        }


        /**
         * Sets the scope values that the client can use when requesting access
         * tokens. Corresponds to the {@code scope} client metadata field.
         *
         * @param scope The scope, {@code null} if not specified.
         */
        public void setScope(final Scope scope) {

                this.scope = scope;
        }


        /**
         * Gets the expected OAuth 2.0 response types. Corresponds to the
         * {@code response_types} client metadata field.
         *
         * @return The response types, {@code null} if not specified.
         */
        public Set<ResponseType> getResponseTypes() {

                return responseTypes;
        }


        /**
         * Sets the expected OAuth 2.0 response types. Corresponds to the
         * {@code response_types} client metadata field.
         *
         * @param responseTypes The response types, {@code null} if not
         *                      specified.
         */
        public void setResponseTypes(final Set<ResponseType> responseTypes) {

                this.responseTypes = responseTypes;
        }


        /**
         * Gets the expected OAuth 2.0 grant types. Corresponds to the
         * {@code grant_types} client metadata field.
         *
         * @return The grant types, {@code null} if not specified.
         */
        public Set<GrantType> getGrantTypes() {

                return grantTypes;
        }


        /**
         * Sets the expected OAuth 2.0 grant types. Corresponds to the
         * {@code grant_types} client metadata field.
         *
         * @param grantTypes The grant types, {@code null} if not specified.
         */
        public void setGrantTypes(final Set<GrantType> grantTypes) {

                this.grantTypes = grantTypes;
        }


        /**
         * Gets the administrator email contacts for the client. Corresponds to
         * the {@code contacts} client metadata field.
         *
         * <p>Use {@link #getEmailContacts()} instead.
         *
         * @return The administrator email contacts, {@code null} if not
         *         specified.
         */
        @Deprecated
        public List<InternetAddress> getContacts() {

                if (contacts == null)
                        return null;
                
                List<InternetAddress> addresses = new LinkedList<>();
                for (String s: contacts) {
                        if (s == null) continue;
                        try {
                                addresses.add(new InternetAddress(s, false));
                        } catch (AddressException e) {
                                // ignore
                        }
                }
                return addresses;
        }


        /**
         * Sets the administrator email contacts for the client. Corresponds to
         * the {@code contacts} client metadata field.
         *
         * <p>Use {@link #setEmailContacts(List)} instead.
         *
         * @param contacts The administrator email contacts, {@code null} if
         *                 not specified.
         */
        @Deprecated
        public void setContacts(final List<InternetAddress> contacts) {

                if (contacts == null) {
                        this.contacts = null;
                        return;
                }
                
                List<String> addresses = new LinkedList<>();
                for (InternetAddress a: contacts) {
                        if (a != null) {
                                addresses.add(a.toString());
                        }
                }
                this.contacts = addresses;
        }


        /**
         * Gets the administrator email contacts for the client. Corresponds to
         * the {@code contacts} client metadata field.
         *
         * @return The administrator email contacts, {@code null} if not
         *         specified.
         */
        public List<String> getEmailContacts() {

                return contacts;
        }


        /**
         * Sets the administrator email contacts for the client. Corresponds to
         * the {@code contacts} client metadata field.
         *
         * @param contacts The administrator email contacts, {@code null} if
         *                 not specified.
         */
        public void setEmailContacts(final List<String> contacts) {

                this.contacts = contacts;
        }


        /**
         * Gets the client name. Corresponds to the {@code client_name} client
         * metadata field, with no language tag.
         *
         * @return The client name, {@code null} if not specified.
         */
        public String getName() {

                return getName(null);
        }


        /**
         * Gets the client name. Corresponds to the {@code client_name} client
         * metadata field, with an optional language tag.
         *
         * @param langTag The language tag of the entry, {@code null} to get
         *                the non-tagged entry.
         *
         * @return The client name, {@code null} if not specified.
         */
        public String getName(final LangTag langTag) {

                return nameEntries.get(langTag);
        }


        /**
         * Gets the client name entries. Corresponds to the {@code client_name}
         * client metadata field.
         *
         * @return The client name entries, empty map if none.
         */
        public Map<LangTag,String> getNameEntries() {

                return nameEntries;
        }


        /**
         * Sets the client name. Corresponds to the {@code client_name} client
         * metadata field, with no language tag.
         *
         * @param name The client name, {@code null} if not specified.
         */
        public void setName(final String name) {

                nameEntries.put(null, name);
        }


        /**
         * Sets the client name. Corresponds to the {@code client_name} client
         * metadata field, with an optional language tag.
         *
         * @param name    The client name. Must not be {@code null}.
         * @param langTag The language tag, {@code null} if not specified.
         */
        public void setName(final String name, final LangTag langTag) {

                nameEntries.put(langTag, name);
        }


        /**
         * Gets the client application logo. Corresponds to the
         * {@code logo_uri} client metadata field, with no language
         * tag.
         *
         * @return The logo URI, {@code null} if not specified.
         */
        public URI getLogoURI() {

                return getLogoURI(null);
        }


        /**
         * Gets the client application logo. Corresponds to the
         * {@code logo_uri} client metadata field, with an optional
         * language tag.
         *
         * @return The logo URI, {@code null} if not specified.
         */
        public URI getLogoURI(final LangTag langTag) {

                return logoURIEntries.get(langTag);
        }


        /**
         * Gets the client application logo entries. Corresponds to the
         * {@code logo_uri} client metadata field.
         *
         * @return The logo URI entries, empty map if none.
         */
        public Map<LangTag,URI> getLogoURIEntries() {

                return logoURIEntries;
        }


        /**
         * Sets the client application logo. Corresponds to the
         * {@code logo_uri} client metadata field, with no language
         * tag.
         *
         * @param logoURI The logo URI, {@code null} if not specified.
         */
        public void setLogoURI(final URI logoURI) {

                logoURIEntries.put(null, logoURI);
        }


        /**
         * Sets the client application logo. Corresponds to the
         * {@code logo_uri} client metadata field, with an optional
         * language tag.
         *
         * @param logoURI The logo URI. Must not be {@code null}.
         * @param langTag The language tag, {@code null} if not specified.
         */
        public void setLogoURI(final URI logoURI, final LangTag langTag) {

                logoURIEntries.put(langTag, logoURI);
        }


        /**
         * Gets the client home page. Corresponds to the {@code client_uri}
         * client metadata field, with no language tag.
         *
         * @return The client URI, {@code null} if not specified.
         */
        public URI getURI() {

                return getURI(null);
        }


        /**
         * Gets the client home page. Corresponds to the {@code client_uri}
         * client metadata field, with an optional language tag.
         *
         * @return The client URI, {@code null} if not specified.
         */
        public URI getURI(final LangTag langTag) {

                return uriEntries.get(langTag);
        }


        /**
         * Gets the client home page entries. Corresponds to the
         * {@code client_uri} client metadata field.
         *
         * @return The client URI entries, empty map if none.
         */
        public Map<LangTag,URI> getURIEntries() {

                return uriEntries;
        }


        /**
         * Sets the client home page. Corresponds to the {@code client_uri}
         * client metadata field, with no language tag.
         *
         * @param uri The client URI, {@code null} if not specified.
         */
        public void setURI(final URI uri) {

                uriEntries.put(null, uri);
        }


        /**
         * Sets the client home page. Corresponds to the {@code client_uri}
         * client metadata field, with an optional language tag.
         *
         * @param uri     The URI. Must not be {@code null}.
         * @param langTag The language tag, {@code null} if not specified.
         */
        public void setURI(final URI uri, final LangTag langTag) {

                uriEntries.put(langTag, uri);
        }


        /**
         * Gets the client policy for use of end-user data. Corresponds to the
         * {@code policy_uri} client metadata field, with no language
         * tag.
         *
         * @return The policy URI, {@code null} if not specified.
         */
        public URI getPolicyURI() {

                return getPolicyURI(null);
        }


        /**
         * Gets the client policy for use of end-user data. Corresponds to the
         * {@code policy_uri} client metadata field, with an optional
         * language tag.
         *
         * @return The policy URI, {@code null} if not specified.
         */
        public URI getPolicyURI(final LangTag langTag) {

                return policyURIEntries.get(langTag);
        }


        /**
         * Gets the client policy entries for use of end-user data.
         * Corresponds to the {@code policy_uri} client metadata field.
         *
         * @return The policy URI entries, empty map if none.
         */
        public Map<LangTag,URI> getPolicyURIEntries() {

                return policyURIEntries;
        }


        /**
         * Sets the client policy for use of end-user data. Corresponds to the
         * {@code policy_uri} client metadata field, with no language
         * tag.
         *
         * @param policyURI The policy URI, {@code null} if not specified.
         */
        public void setPolicyURI(final URI policyURI) {

                policyURIEntries.put(null, policyURI);
        }


        /**
         * Sets the client policy for use of end-user data. Corresponds to the
         * {@code policy_uri} client metadata field, with an optional
         * language tag.
         *
         * @param policyURI The policy URI. Must not be {@code null}.
         * @param langTag   The language tag, {@code null} if not specified.
         */
        public void setPolicyURI(final URI policyURI, final LangTag langTag) {

                policyURIEntries.put(langTag, policyURI);
        }


        /**
         * Gets the client's terms of service. Corresponds to the
         * {@code tos_uri} client metadata field, with no language
         * tag.
         *
         * @return The terms of service URI, {@code null} if not specified.
         */
        public URI getTermsOfServiceURI() {

                return getTermsOfServiceURI(null);
        }


        /**
         * Gets the client's terms of service. Corresponds to the
         * {@code tos_uri} client metadata field, with an optional
         * language tag.
         *
         * @return The terms of service URI, {@code null} if not specified.
         */
        public URI getTermsOfServiceURI(final LangTag langTag) {

                return tosURIEntries.get(langTag);
        }


        /**
         * Gets the client's terms of service entries. Corresponds to the
         * {@code tos_uri} client metadata field.
         *
         * @return The terms of service URI entries, empty map if none.
         */
        public Map<LangTag,URI> getTermsOfServiceURIEntries() {

                return tosURIEntries;
        }


        /**
         * Sets the client's terms of service. Corresponds to the
         * {@code tos_uri} client metadata field, with no language
         * tag.
         *
         * @param tosURI The terms of service URI, {@code null} if not
         *               specified.
         */
        public void setTermsOfServiceURI(final URI tosURI) {

                tosURIEntries.put(null, tosURI);
        }


        /**
         * Sets the client's terms of service. Corresponds to the
         * {@code tos_uri} client metadata field, with an optional
         * language tag.
         *
         * @param tosURI  The terms of service URI. Must not be {@code null}.
         * @param langTag The language tag, {@code null} if not specified.
         */
        public void setTermsOfServiceURI(final URI tosURI, final LangTag langTag) {

                tosURIEntries.put(langTag, tosURI);
        }


        /**
         * Gets the Token endpoint authentication method. Corresponds to the
         * {@code token_endpoint_auth_method} client metadata field.
         *
         * @return The Token endpoint authentication method, {@code null} if
         *         not specified.
         */
        public ClientAuthenticationMethod getTokenEndpointAuthMethod() {

                return authMethod;
        }


        /**
         * Sets the Token endpoint authentication method. Corresponds to the
         * {@code token_endpoint_auth_method} client metadata field.
         *
         * @param authMethod The Token endpoint authentication  method,
         *                   {@code null} if not specified.
         */
        public void setTokenEndpointAuthMethod(final ClientAuthenticationMethod authMethod) {

                this.authMethod = authMethod;
        }


        /**
         * Gets the JSON Web Signature (JWS) algorithm required for
         * {@code private_key_jwt} and {@code client_secret_jwt}
         * authentication at the Token endpoint. Corresponds to the
         * {@code token_endpoint_auth_signing_alg} client metadata field.
         *
         * @return The JWS algorithm, {@code null} if not specified.
         */
        public JWSAlgorithm getTokenEndpointAuthJWSAlg() {

                return authJWSAlg;
        }


        /**
         * Sets the JSON Web Signature (JWS) algorithm required for
         * {@code private_key_jwt} and {@code client_secret_jwt}
         * authentication at the Token endpoint. Corresponds to the
         * {@code token_endpoint_auth_signing_alg} client metadata field.
         *
         * @param authJWSAlg The JWS algorithm, {@code null} if not specified.
         */
        public void setTokenEndpointAuthJWSAlg(final JWSAlgorithm authJWSAlg) {

                this.authJWSAlg = authJWSAlg;
        }


        /**
         * Gets the URI for this client's JSON Web Key (JWK) set containing
         * key(s) that are used in signing requests to the server and key(s)
         * for encrypting responses. Corresponds to the {@code jwks_uri} client
         * metadata field.
         *
         * @return The JWK set URI, {@code null} if not specified.
         */
        public URI getJWKSetURI() {

                return jwkSetURI;
        }


        /**
         * Sets the URI for this client's JSON Web Key (JWK) set containing
         * key(s) that are used in signing requests to the server and key(s)
         * for encrypting responses. Corresponds to the {@code jwks_uri} client
         * metadata field.
         *
         * @param jwkSetURI The JWK set URI, {@code null} if not specified.
         */
        public void setJWKSetURI(final URI jwkSetURI) {

                this.jwkSetURI = jwkSetURI;
        }


        /**
         * Gets this client's JSON Web Key (JWK) set containing key(s) that are
         * used in signing requests to the server and key(s) for encrypting
         * responses. Intended as an alternative to {@link #getJWKSetURI} for
         * native clients. Corresponds to the {@code jwks} client metadata
         * field.
         *
         * @return The JWK set, {@code null} if not specified.
         */
        public JWKSet getJWKSet() {

                return jwkSet;
        }


        /**
         * Sets this client's JSON Web Key (JWK) set containing key(s) that are
         * used in signing requests to the server and key(s) for encrypting
         * responses. Intended as an alternative to {@link #getJWKSetURI} for
         * native clients. Corresponds to the {@code jwks} client metadata
         * field.
         *
         * @param jwkSet The JWK set, {@code null} if not specified.
         */
        public void setJWKSet(final JWKSet jwkSet) {

                this.jwkSet = jwkSet;
        }


        /**
         * Gets the identifier for the OAuth 2.0 client software. Corresponds
         * to the {@code software_id} client metadata field.
         *
         * @return The software identifier, {@code null} if not specified.
         */
        public SoftwareID getSoftwareID() {

                return softwareID;
        }


        /**
         * Sets the identifier for the OAuth 2.0 client software. Corresponds
         * to the {@code software_id} client metadata field.
         *
         * @param softwareID The software identifier, {@code null} if not
         *                   specified.
         */
        public void setSoftwareID(final SoftwareID softwareID) {

                this.softwareID = softwareID;
        }


        /**
         * Gets the version identifier for the OAuth 2.0 client software.
         * Corresponds to the {@code software_version} client metadata field.
         *
         * @return The version identifier, {@code null} if not specified.
         */
        public SoftwareVersion getSoftwareVersion() {

                return softwareVersion;
        }


        /**
         * Sets the version identifier for the OAuth 2.0 client software.
         * Corresponds to the {@code software_version} client metadata field.
         *
         * @param softwareVersion The version identifier, {@code null} if not
         *                        specified.
         */
        public void setSoftwareVersion(final SoftwareVersion softwareVersion) {

                this.softwareVersion = softwareVersion;
        }


        /**
         * Gets the specified custom metadata field.
         *
         * @param name The field name. Must not be {@code null}.
         *
         * @return The field value, typically serialisable to a JSON entity,
         *         {@code null} if none.
         */
        public Object getCustomField(final String name) {

                return customFields.get(name);
        }


        /**
         * Gets the custom metadata fields.
         *
         * @return The custom metadata fields, as a JSON object, empty object
         *         if none.
         */
        public JSONObject getCustomFields() {

                return customFields;
        }


        /**
         * Sets the specified custom metadata field.
         *
         * @param name  The field name. Must not be {@code null}.
         * @param value The field value. Should serialise to a JSON entity.
         */
        public void setCustomField(final String name, final Object value) {

                customFields.put(name, value);
        }


        /**
         * Sets the custom metadata fields.
         *
         * @param customFields The custom metadata fields, as a JSON object,
         *                     empty object if none. Must not be {@code null}.
         */
        public void setCustomFields(final JSONObject customFields) {

                if (customFields == null)
                        throw new IllegalArgumentException("The custom fields JSON object must not be null");

                this.customFields = customFields;
        }


        /**
         * Applies the client metadata defaults where no values have been
         * specified.
         *
         * <ul>
         *     <li>The response types default to {@code ["code"]}.
         *     <li>The grant types default to {@code ["authorization_code"]}.
         *     <li>The client authentication method defaults to
         *         "client_secret_basic", unless the grant type is "implicit"
         *         only.
         * </ul>
         */
        public void applyDefaults() {

                if (responseTypes == null) {
                        responseTypes = new HashSet<>();
                        responseTypes.add(ResponseType.getDefault());
                }

                if (grantTypes == null) {
                        grantTypes = new HashSet<>();
                        grantTypes.add(GrantType.AUTHORIZATION_CODE);
                }

                if (authMethod == null) {

                        if (grantTypes.contains(GrantType.IMPLICIT) && grantTypes.size() == 1) {
                                authMethod = ClientAuthenticationMethod.NONE;
                        } else {
                                authMethod = ClientAuthenticationMethod.getDefault();
                        }
                }
        }


        /**
         * Returns the JSON object representation of this client metadata,
         * including any custom fields.
         *
         * @return The JSON object.
         */
        public JSONObject toJSONObject() {

                return toJSONObject(true);
        }


        /**
         * Returns the JSON object representation of this client metadata.
         *
         * @param includeCustomFields {@code true} to include any custom
         *                            metadata fields, {@code false} to omit
         *                            them.
         *
         * @return The JSON object.
         */
        public JSONObject toJSONObject(final boolean includeCustomFields) {

                JSONObject o;

                if (includeCustomFields)
                        o = new JSONObject(customFields);
                else
                        o = new JSONObject();


                if (redirectURIs != null) {

                        JSONArray uriList = new JSONArray();

                        for (URI uri: redirectURIs)
                                uriList.add(uri.toString());

                        o.put("redirect_uris", uriList);
                }


                if (scope != null)
                        o.put("scope", scope.toString());


                if (responseTypes != null) {

                        JSONArray rtList = new JSONArray();

                        for (ResponseType rt: responseTypes)
                                rtList.add(rt.toString());

                        o.put("response_types", rtList);
                }


                if (grantTypes != null) {

                        JSONArray grantList = new JSONArray();

                        for (GrantType grant: grantTypes)
                                grantList.add(grant.toString());

                        o.put("grant_types", grantList);
                }


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


                if (! nameEntries.isEmpty()) {

                        for (Map.Entry<LangTag,String> entry: nameEntries.entrySet()) {

                                LangTag langTag = entry.getKey();
                                String name = entry.getValue();

                                if (name == null)
                                        continue;

                                if (langTag == null)
                                        o.put("client_name", entry.getValue());
                                else
                                        o.put("client_name#" + langTag, entry.getValue());
                        }
                }


                if (! logoURIEntries.isEmpty()) {

                        for (Map.Entry<LangTag,URI> entry: logoURIEntries.entrySet()) {

                                LangTag langTag = entry.getKey();
                                URI uri = entry.getValue();

                                if (uri == null)
                                        continue;

                                if (langTag == null)
                                        o.put("logo_uri", entry.getValue().toString());
                                else
                                        o.put("logo_uri#" + langTag, entry.getValue().toString());
                        }
                }


                if (! uriEntries.isEmpty()) {

                        for (Map.Entry<LangTag,URI> entry: uriEntries.entrySet()) {

                                LangTag langTag = entry.getKey();
                                URI uri = entry.getValue();

                                if (uri == null)
                                        continue;

                                if (langTag == null)
                                        o.put("client_uri", entry.getValue().toString());
                                else
                                        o.put("client_uri#" + langTag, entry.getValue().toString());
                        }
                }


                if (! policyURIEntries.isEmpty()) {

                        for (Map.Entry<LangTag,URI> entry: policyURIEntries.entrySet()) {

                                LangTag langTag = entry.getKey();
                                URI uri = entry.getValue();

                                if (uri == null)
                                        continue;

                                if (langTag == null)
                                        o.put("policy_uri", entry.getValue().toString());
                                else
                                        o.put("policy_uri#" + langTag, entry.getValue().toString());
                        }
                }


                if (! tosURIEntries.isEmpty()) {

                        for (Map.Entry<LangTag,URI> entry: tosURIEntries.entrySet()) {

                                LangTag langTag = entry.getKey();
                                URI uri = entry.getValue();

                                if (uri == null)
                                        continue;

                                if (langTag == null)
                                        o.put("tos_uri", entry.getValue().toString());
                                else
                                        o.put("tos_uri#" + langTag, entry.getValue().toString());
                        }
                }


                if (authMethod != null)
                        o.put("token_endpoint_auth_method", authMethod.toString());


                if (authJWSAlg != null)
                        o.put("token_endpoint_auth_signing_alg", authJWSAlg.getName());


                if (jwkSetURI != null)
                        o.put("jwks_uri", jwkSetURI.toString());


                if (jwkSet != null)
                        o.put("jwks", jwkSet.toJSONObject(true)); // prevent private keys from leaking


                if (softwareID != null)
                        o.put("software_id", softwareID.getValue());

                if (softwareVersion != null)
                        o.put("software_version", softwareVersion.getValue());

                return o;
        }


        /**
         * Parses an client metadata instance from the specified JSON object.
         *
         * @param jsonObject The JSON object to parse. Must not be
         *                   {@code null}.
         *
         * @return The client metadata.
         *
         * @throws ParseException If the JSON object couldn't be parsed to a
         *                        client metadata instance.
         */
        public static ClientMetadata parse(final JSONObject jsonObject)
                throws ParseException {

                // Copy JSON object, then parse
                return parseFromModifiableJSONObject(new JSONObject(jsonObject));
        }


        /**
         * Parses an client metadata instance from the specified JSON object.
         *
         * @param jsonObject The JSON object to parse, will be modified by
         *                   the parse routine. Must not be {@code null}.
         *
         * @return The client metadata.
         *
         * @throws ParseException If the JSON object couldn't be parsed to a
         *                        client metadata instance.
         */
        private static ClientMetadata parseFromModifiableJSONObject(final JSONObject jsonObject)
                throws ParseException {

                ClientMetadata metadata = new ClientMetadata();

                if (jsonObject.get("redirect_uris") != null) {

                        Set<URI> redirectURIs = new LinkedHashSet<>();

                        for (String uriString: JSONObjectUtils.getStringArray(jsonObject, "redirect_uris")) {
                                URI uri;
                                try {
                                        uri = new URI(uriString);
                                } catch (URISyntaxException e) {
                                        throw new ParseException("Invalid \"redirect_uris\" parameter: " + e.getMessage(), RegistrationError.INVALID_REDIRECT_URI.appendDescription(": " + e.getMessage()));
                                }

                                if (uri.getFragment() != null) {
                                        String detail = "URI must not contain fragment";
                                        throw new ParseException("Invalid \"redirect_uris\" parameter: " + detail, RegistrationError.INVALID_REDIRECT_URI.appendDescription(": " + detail));
                                }

                                redirectURIs.add(uri);
                        }

                        metadata.setRedirectionURIs(redirectURIs);
                        jsonObject.remove("redirect_uris");
                }

                try {

                        if (jsonObject.get("scope") != null) {
                                metadata.setScope(Scope.parse(JSONObjectUtils.getString(jsonObject, "scope")));
                                jsonObject.remove("scope");
                        }


                        if (jsonObject.get("response_types") != null) {

                                Set<ResponseType> responseTypes = new LinkedHashSet<>();

                                for (String rt : JSONObjectUtils.getStringArray(jsonObject, "response_types")) {

                                        responseTypes.add(ResponseType.parse(rt));
                                }

                                metadata.setResponseTypes(responseTypes);
                                jsonObject.remove("response_types");
                        }


                        if (jsonObject.get("grant_types") != null) {

                                Set<GrantType> grantTypes = new LinkedHashSet<>();

                                for (String grant : JSONObjectUtils.getStringArray(jsonObject, "grant_types")) {

                                        grantTypes.add(GrantType.parse(grant));
                                }

                                metadata.setGrantTypes(grantTypes);
                                jsonObject.remove("grant_types");
                        }


                        if (jsonObject.get("contacts") != null) {
                                metadata.setEmailContacts(JSONObjectUtils.getStringList(jsonObject, "contacts"));
                                jsonObject.remove("contacts");
                        }


                        // Find lang-tagged client_name params
                        Map<LangTag, Object> matches = LangTagUtils.find("client_name", jsonObject);

                        for (Map.Entry<LangTag, Object> entry : matches.entrySet()) {

                                try {
                                        metadata.setName((String) entry.getValue(), entry.getKey());

                                } catch (ClassCastException e) {

                                        throw new ParseException("Invalid \"client_name\" (language tag) parameter");
                                }

                                removeMember(jsonObject, "client_name", entry.getKey());
                        }


                        matches = LangTagUtils.find("logo_uri", jsonObject);

                        for (Map.Entry<LangTag, Object> entry : matches.entrySet()) {

                                if (entry.getValue() == null) continue;
                                
                                try {
                                        metadata.setLogoURI(new URI((String) entry.getValue()), entry.getKey());

                                } catch (Exception e) {

                                        throw new ParseException("Invalid \"logo_uri\" (language tag) parameter");
                                }

                                removeMember(jsonObject, "logo_uri", entry.getKey());
                        }


                        matches = LangTagUtils.find("client_uri", jsonObject);

                        for (Map.Entry<LangTag, Object> entry : matches.entrySet()) {
                                
                                if (entry.getValue() == null) continue;

                                try {
                                        metadata.setURI(new URI((String) entry.getValue()), entry.getKey());


                                } catch (Exception e) {

                                        throw new ParseException("Invalid \"client_uri\" (language tag) parameter");
                                }

                                removeMember(jsonObject, "client_uri", entry.getKey());
                        }


                        matches = LangTagUtils.find("policy_uri", jsonObject);

                        for (Map.Entry<LangTag, Object> entry : matches.entrySet()) {
                                
                                if (entry.getValue() == null) continue;

                                try {
                                        metadata.setPolicyURI(new URI((String) entry.getValue()), entry.getKey());

                                } catch (Exception e) {

                                        throw new ParseException("Invalid \"policy_uri\" (language tag) parameter");
                                }

                                removeMember(jsonObject, "policy_uri", entry.getKey());
                        }


                        matches = LangTagUtils.find("tos_uri", jsonObject);

                        for (Map.Entry<LangTag, Object> entry : matches.entrySet()) {
                                
                                if (entry.getValue() == null) continue;

                                try {
                                        metadata.setTermsOfServiceURI(new URI((String) entry.getValue()), entry.getKey());

                                } catch (Exception e) {

                                        throw new ParseException("Invalid \"tos_uri\" (language tag) parameter");
                                }

                                removeMember(jsonObject, "tos_uri", entry.getKey());
                        }


                        if (jsonObject.get("token_endpoint_auth_method") != null) {
                                metadata.setTokenEndpointAuthMethod(ClientAuthenticationMethod.parse(
                                        JSONObjectUtils.getString(jsonObject, "token_endpoint_auth_method")));

                                jsonObject.remove("token_endpoint_auth_method");
                        }


                        if (jsonObject.get("token_endpoint_auth_signing_alg") != null) {
                                metadata.setTokenEndpointAuthJWSAlg(JWSAlgorithm.parse(
                                        JSONObjectUtils.getString(jsonObject, "token_endpoint_auth_signing_alg")));

                                jsonObject.remove("token_endpoint_auth_signing_alg");
                        }


                        if (jsonObject.get("jwks_uri") != null) {
                                metadata.setJWKSetURI(JSONObjectUtils.getURI(jsonObject, "jwks_uri"));
                                jsonObject.remove("jwks_uri");
                        }

                        if (jsonObject.get("jwks") != null) {

                                try {
                                        metadata.setJWKSet(JWKSet.parse(JSONObjectUtils.getJSONObject(jsonObject, "jwks")));

                                } catch (java.text.ParseException e) {
                                        throw new ParseException(e.getMessage(), e);
                                }

                                jsonObject.remove("jwks");
                        }

                        if (jsonObject.get("software_id") != null) {
                                metadata.setSoftwareID(new SoftwareID(JSONObjectUtils.getString(jsonObject, "software_id")));
                                jsonObject.remove("software_id");
                        }

                        if (jsonObject.get("software_version") != null) {
                                metadata.setSoftwareVersion(new SoftwareVersion(JSONObjectUtils.getString(jsonObject, "software_version")));
                                jsonObject.remove("software_version");
                        }

                } catch (ParseException e) {
                        // Insert client_client_metadata error code so that it
                        // can be reported back to the client if we have a
                        // registration event
                        throw new ParseException(e.getMessage(), RegistrationError.INVALID_CLIENT_METADATA.appendDescription(": " + e.getMessage()), e.getCause());
                }

                // The remaining fields are custom
                metadata.customFields = jsonObject;

                return metadata;
        }


        /**
         * Removes a JSON object member with the specified base name and
         * optional language tag.
         *
         * @param jsonObject The JSON object. Must not be {@code null}.
         * @param name       The base member name. Must not be {@code null}.
         * @param langTag    The language tag, {@code null} if none.
         */
        private static void removeMember(final JSONObject jsonObject, final String name, final LangTag langTag) {

                if (langTag == null)
                        jsonObject.remove(name);
                else
                        jsonObject.remove(name + "#" + langTag);
        }
}