package com.nimbusds.oauth2.sdk.auth;


import java.util.Collections;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import net.jcip.annotations.Immutable;

import com.nimbusds.jose.JWSAlgorithm;
import com.nimbusds.jwt.SignedJWT;

import com.nimbusds.oauth2.sdk.ParseException;
import com.nimbusds.oauth2.sdk.id.ClientID;
import com.nimbusds.oauth2.sdk.http.CommonContentTypes;
import com.nimbusds.oauth2.sdk.http.HTTPRequest;
import com.nimbusds.oauth2.sdk.util.URLUtils;


/**
 * Private key JWT authentication at the Token endpoint. Implements
 * {@link ClientAuthenticationMethod#PRIVATE_KEY_JWT}. This class is immutable.
 *
 * <p>Supported signature JSON Web Algorithms (JWAs) by this implementation:
 *
 * <ul>
 *     <li>RS256
 *     <li>RS384
 *     <li>RS512
 *     <li>PS256
 *     <li>PS384
 *     <li>PS512
 *     <li>ES256
 *     <li>ES384
 *     <li>ES512
 * </ul>
 *
 * <p>Example {@link com.nimbusds.oauth2.sdk.TokenRequest} with private key JWT
 * authentication:
 *
 * <pre>
 * POST /token HTTP/1.1
 * Host: server.example.com
 * Content-Type: application/x-www-form-urlencoded
 *
 * grant_type=authorization_code&amp;
 * code=i1WsRn1uB1&amp;
 * client_id=s6BhdRkqt3&amp;
 * client_assertion_type=urn%3Aietf%3Aparams%3Aoauth%3Aclient-assertion-type%3Ajwt-bearer&amp;
 * client_assertion=PHNhbWxwOl...[omitted for brevity]...ZT
 * </pre>
 *
 * <p>Related specifications:
 *
 * <ul>
 *     <li>Assertion Framework for OAuth 2.0 (draft-ietf-oauth-assertions-06)
 *     <li>JSON Web Token (JWT) Bearer Token Profiles for OAuth 2.0 
 *         (draft-ietf-oauth-jwt-bearer-06).
 * </ul>
 *
 * @author Vladimir Dzhuvinov
 */
@Immutable
public final class PrivateKeyJWT extends JWTAuthentication {


        /**
         * Gets the set of supported signature JSON Web Algorithms (JWAs) by 
         * this implementation of private key JSON Web Token (JWT) 
         * authentication.
         *
         * @return The set of supported JSON Web Algorithms (JWAs).
         */
        public static Set<JWSAlgorithm> getSupportedJWAs() {
        
                Set<JWSAlgorithm> supported = new HashSet<JWSAlgorithm>();
                
                supported.add(JWSAlgorithm.RS256);
                supported.add(JWSAlgorithm.RS384);
                supported.add(JWSAlgorithm.RS512);

                supported.add(JWSAlgorithm.PS256);
                supported.add(JWSAlgorithm.PS384);
                supported.add(JWSAlgorithm.PS512);
                
                supported.add(JWSAlgorithm.ES256);
                supported.add(JWSAlgorithm.ES384);
                supported.add(JWSAlgorithm.ES512);
                
                return Collections.unmodifiableSet(supported);
        }
        
        
        /**
         * Creates a private key JWT authentication.
         *
         * @param clientAssertion The client assertion, corresponding to the
         *                        {@code client_assertion} parameter, as a
         *                        supported RSA or ECDSA-signed JWT. Must be
         *                        signed and not {@code null}.
         */
        public PrivateKeyJWT(final SignedJWT clientAssertion) {
        
                super(ClientAuthenticationMethod.PRIVATE_KEY_JWT, clientAssertion);

                if (! getSupportedJWAs().contains(clientAssertion.getHeader().getAlgorithm()))
                        throw new IllegalArgumentException("The client assertion JWT must be RSA or ECDSA-signed (RS256, RS384, RS512, PS256, PS384, PS512, ES256, ES384 or ES512)");
        }
        
        
        /**
         * Parses the specified parameters map for a private key JSON Web Token
         * (JWT) authentication. Note that the parameters must not be
         * {@code application/x-www-form-urlencoded} encoded.
         *
         * @param params The parameters map to parse. The private key JSON
         *               Web Token (JWT) parameters must be keyed under 
         *               "client_assertion" and "client_assertion_type". The 
         *               map must not be {@code null}.
         *
         * @return The private key JSON Web Token (JWT) authentication.
         *
         * @throws ParseException If the parameters map couldn't be parsed to a 
         *                        private key JSON Web Token (JWT) 
         *                        authentication.
         */
        public static PrivateKeyJWT parse(final Map<String,String> params)
                throws ParseException {
        
                JWTAuthentication.ensureClientAssertionType(params);
                
                SignedJWT clientAssertion = JWTAuthentication.parseClientAssertion(params);

                PrivateKeyJWT privateKeyJWT;

                try {
                        privateKeyJWT = new PrivateKeyJWT(clientAssertion);

                }catch (IllegalArgumentException e) {

                        throw new ParseException(e.getMessage(), e);
                }

                // Check that the top level client_id matches the assertion subject + issuer

                ClientID clientID = JWTAuthentication.parseClientID(params);

                if (clientID != null) {

                        if (! clientID.equals(privateKeyJWT.getClientID()))
                                throw new ParseException("The client identifier doesn't match the client assertion subject / issuer");
                }

                return privateKeyJWT;
        }
        
        
        /**
         * Parses a private key JSON Web Token (JWT) authentication from the 
         * specified {@code application/x-www-form-urlencoded} encoded 
         * parameters string.
         *
         * @param paramsString The parameters string to parse. The private key
         *                     JSON Web Token (JWT) parameters must be keyed 
         *                     under "client_assertion" and 
         *                     "client_assertion_type". The string must not be 
         *                     {@code null}.
         *
         * @return The private key JSON Web Token (JWT) authentication.
         *
         * @throws ParseException If the parameters string couldn't be parsed 
         *                        to a private key JSON Web Token (JWT) 
         *                        authentication.
         */
        public static PrivateKeyJWT parse(final String paramsString)
                throws ParseException {
                
                Map<String,String> params = URLUtils.parseParameters(paramsString);
                
                return parse(params);
        }
        
        
        /**
         * Parses the specified HTTP POST request for a private key JSON Web 
         * Token (JWT) authentication.
         *
         * @param httpRequest The HTTP POST request to parse. Must not be 
         *                    {@code null} and must contain a valid 
         *                    {@code application/x-www-form-urlencoded} encoded 
         *                    parameters string in the entity body. The private 
         *                    key JSON Web Token (JWT) parameters must be 
         *                    keyed under "client_assertion" and 
         *                    "client_assertion_type".
         *
         * @return The private key JSON Web Token (JWT) authentication.
         *
         * @throws ParseException If the HTTP request header couldn't be parsed
         *                        to a private key JSON Web Token (JWT) 
         *                        authentication.
         */
        public static PrivateKeyJWT parse(final HTTPRequest httpRequest)
                throws ParseException {
                
                httpRequest.ensureMethod(HTTPRequest.Method.POST);
                httpRequest.ensureContentType(CommonContentTypes.APPLICATION_URLENCODED);
                
                return parse(httpRequest.getQueryParameters());
        }
}