package com.nimbusds.jose;


import net.jcip.annotations.Immutable;


/**
 * Encryption method name, represents the {@code enc} header parameter in JSON
 * Web Encryption (JWE) objects. This class is immutable.
 *
 * <p>Includes constants for the following standard encryption method names:
 *
 * <ul>
 *     <li>{@link #A128CBC_HS256 A128CBC-HS256}
 *     <li>{@link #A192CBC_HS384 A192CBC-HS384}
 *     <li>{@link #A256CBC_HS512 A256CBC-HS512}
 *     <li>{@link #A128GCM}
 *     <li>{@link #A192GCM}
 *     <li>{@link #A256GCM}
 *     <li>{@link #A128CBC_HS256_DEPRECATED A128CBC+HS256 (deprecated)}
 *     <li>{@link #A256CBC_HS512_DEPRECATED A256CBC+HS512 (deprecated)}
 * </ul>
 *
 * <p>Additional encryption method names can be defined using the constructors.
 *
 * @author Vladimir Dzhuvinov
 * @version 2015-10-14
 */
@Immutable
public final class EncryptionMethod extends Algorithm {


        private static final long serialVersionUID = 1L;


        /**
         * The Content Encryption Key (CEK) bit length, zero if not specified.
         */
        private final int cekBitLength;


        /**
         * AES_128_CBC_HMAC_SHA_256 authenticated encryption using a 256 bit 
         * key (required).
         */
        public static final EncryptionMethod A128CBC_HS256 = 
                new EncryptionMethod("A128CBC-HS256", Requirement.REQUIRED, 256);


        /**
         * AES_192_CBC_HMAC_SHA_384 authenticated encryption using a 384 bit
         * key (optional).
         */
        public static final EncryptionMethod A192CBC_HS384 =
                new EncryptionMethod("A192CBC-HS384", Requirement.OPTIONAL, 384);


        /**
         * AES_256_CBC_HMAC_SHA_512 authenticated encryption using a 512 bit
         * key (required).
         */
        public static final EncryptionMethod A256CBC_HS512 = 
                new EncryptionMethod("A256CBC-HS512", Requirement.REQUIRED, 512);


        /**
         * AES_128_CBC_HMAC_SHA_256 authenticated encryption using a 256 bit
         * key, deprecated in JOSE draft suite version 09.
         */
        public static final EncryptionMethod A128CBC_HS256_DEPRECATED =
                new EncryptionMethod("A128CBC+HS256", Requirement.OPTIONAL, 256);


        /**
         * AES_256_CBC_HMAC_SHA_512 authenticated encryption using a 512 bit
         * key, deprecated in JOSE draft suite version 09.
         */
        public static final EncryptionMethod A256CBC_HS512_DEPRECATED =
                new EncryptionMethod("A256CBC+HS512", Requirement.OPTIONAL, 512);


        /**
         * AES in Galois/Counter Mode (GCM) (NIST.800-38D) using a 128 bit key 
         * (recommended).
         */
        public static final EncryptionMethod A128GCM = 
                new EncryptionMethod("A128GCM", Requirement.RECOMMENDED, 128);


        /**
         * AES in Galois/Counter Mode (GCM) (NIST.800-38D) using a 192 bit key
         * (optional).
         */
        public static final EncryptionMethod A192GCM =
                new EncryptionMethod("A192GCM", Requirement.OPTIONAL, 192);


        /**
         * AES in Galois/Counter Mode (GCM) (NIST.800-38D) using a 256 bit key 
         * (recommended).
         */
        public static final EncryptionMethod A256GCM = 
                new EncryptionMethod("A256GCM", Requirement.RECOMMENDED, 256);


        /**
         * Encryption method family.
         */
        public static final class Family extends AlgorithmFamily<EncryptionMethod> {


                private static final long serialVersionUID = 1L;


                /**
                 * AES/CBC/HMAC with SHA-2.
                 */
                public static final Family AES_CBC_HMAC_SHA = new Family(A128CBC_HS256, A192CBC_HS384, A256CBC_HS512);


                /**
                 * AES/GCM.
                 */
                public static final Family AES_GCM = new Family(A128GCM, A192GCM, A256GCM);


                /***
                 * Creates a new encryption method family.
                 *
                 * @param encs The encryption methods of the family. Must not
                 *             be {@code null}.
                 */
                public Family(final EncryptionMethod ... encs) {
                        super(encs);
                }
        }


        /**
         * Creates a new encryption method.
         *
         * @param name         The encryption method name. Must not be 
         *                     {@code null}.
         * @param req          The implementation requirement, {@code null} if 
         *                     not known.
         * @param cekBitLength The Content Encryption Key (CEK) bit length, 
         *                     zero if not specified.
         */
        public EncryptionMethod(final String name, final Requirement req, final int cekBitLength) {

                super(name, req);

                this.cekBitLength = cekBitLength;
        }


        /**
         * Creates a new encryption method. The Content Encryption Key (CEK)
         * bit length is not specified.
         *
         * @param name The encryption method name. Must not be {@code null}.
         * @param req  The implementation requirement, {@code null} if not 
         *             known.
         */
        public EncryptionMethod(final String name, final Requirement req) {

                this(name, req, 0);
        }


        /**
         * Creates a new encryption method. The implementation requirement and
         * the Content Encryption Key (CEK) bit length are not specified.
         *
         * @param name The encryption method name. Must not be {@code null}.
         */
        public EncryptionMethod(final String name) {

                this(name, null, 0);
        }


        /**
         * Gets the length of the associated Content Encryption Key (CEK).
         *
         * @return The Content Encryption Key (CEK) bit length, zero if not 
         *         specified.
         */
        public int cekBitLength() {

                return cekBitLength;
        }


        /**
         * Parses an encryption method from the specified string.
         *
         * @param s The string to parse. Must not be {@code null}.
         *
         * @return The encryption method  (matching standard algorithm
         *         constant, else a newly created algorithm).
         */
        public static EncryptionMethod parse(final String s) {

                if (s.equals(A128CBC_HS256.getName())) {

                        return A128CBC_HS256;

                } else if (s.equals(A192CBC_HS384.getName())) {

                        return A192CBC_HS384;

                } else if (s.equals(A256CBC_HS512.getName())) {

                        return A256CBC_HS512;

                } else if (s.equals(A128GCM.getName())) {

                        return A128GCM;

                } else if (s.equals(A192GCM.getName())) {

                        return A192GCM;

                } else if (s.equals(A256GCM.getName())) {

                        return A256GCM;

                } else if (s.equals(A128CBC_HS256_DEPRECATED.getName())) {

                        return A128CBC_HS256_DEPRECATED;

                } else if (s.equals(A256CBC_HS512_DEPRECATED.getName())) {

                        return A256CBC_HS512_DEPRECATED;

                } else {

                        return new EncryptionMethod(s);
                }
        }
}