package com.nimbusds.jose.jwk;


import java.net.URI;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.List;
import java.text.ParseException;
import java.util.Set;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import com.nimbusds.jose.JOSEException;
import net.jcip.annotations.Immutable;

import net.minidev.json.JSONObject;

import com.nimbusds.jose.Algorithm;
import com.nimbusds.jose.util.Base64;
import com.nimbusds.jose.util.Base64URL;
import com.nimbusds.jose.util.JSONObjectUtils;


/**
 * {@link KeyType#OCT Octet sequence} JSON Web Key (JWK), used to represent
 * symmetric keys. This class is immutable.
 *
 * <p>Octet sequence JWKs should specify the algorithm intended to be used with
 * the key, unless the application uses other means or convention to determine
 * the algorithm used.
 *
 * <p>Example JSON object representation of an octet sequence JWK:
 *
 * <pre>
 * {
 *   "kty" : "oct",
 *   "alg" : "A128KW",
 *   "k"   : "GawgguFyGrWKav7AX4VKUg"
 * }
 * </pre>
 * 
 * @author Justin Richer
 * @author Vladimir Dzhuvinov
 * @version 2015-09-21
 */
@Immutable
public final class OctetSequenceKey extends JWK {


        /**
         * The key value.
         */
        private final Base64URL k;


        /**
         * Builder for constructing octet sequence JWKs.
         *
         * <p>Example usage:
         *
         * <pre>
         * OctetSequenceKey key = new OctetSequenceKey.Builder(k).
         *                        algorithm(JWSAlgorithm.HS512).
         *                        keyID("123").
         *                        build();
         * </pre>
         */
        public static class Builder {


                /**
                 * The key value.
                 */
                private final Base64URL k;


                /**
                 * The public key use, optional.
                 */
                private KeyUse use;


                /**
                 * The key operations, optional.
                 */
                private Set<KeyOperation> ops;


                /**
                 * The intended JOSE algorithm for the key, optional.
                 */
                private Algorithm alg;


                /**
                 * The key ID, optional.
                 */
                private String kid;


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


                /**
                 * X.509 certificate thumbprint, optional.
                 */
                private Base64URL x5t;


                /**
                 * The X.509 certificate chain, optional.
                 */
                private List<Base64> x5c;


                /**
                 * Creates a new octet sequence JWK builder.
                 *
                 * @param k The key value. It is represented as the Base64URL 
                 *          encoding of value's big endian representation. Must
                 *          not be {@code null}.
                 */
                public Builder(final Base64URL k) {

                        if (k == null) {
                                throw new IllegalArgumentException("The key value must not be null");
                        }

                        this.k = k;
                }


                /**
                 * Creates a new octet sequence JWK builder.
                 *
                 * @param key The key value. Must not be empty byte array or
                 *            {@code null}.
                 */
                public Builder(final byte[] key) {

                        this(Base64URL.encode(key));

                        if (key.length == 0) {
                                throw new IllegalArgumentException("The key must have a positive length");
                        }
                }


                /**
                 * Creates a new octet sequence JWK builder.
                 *
                 * @param secretKey The secret key to represent. Must not be
                 *                  {@code null}.
                 */
                public Builder(final SecretKey secretKey) {

                        this(secretKey.getEncoded());
                }


                /**
                 * Sets the use ({@code use}) of the JWK.
                 *
                 * @param use The key use, {@code null} if not specified or if
                 *            the key is intended for signing as well as
                 *            encryption.
                 *
                 * @return This builder.
                 */
                public Builder keyUse(final KeyUse use) {

                        this.use = use;
                        return this;
                }


                /**
                 * Sets the operations ({@code key_ops}) of the JWK (for a
                 * non-public key).
                 *
                 * @param ops The key operations, {@code null} if not
                 *            specified.
                 *
                 * @return This builder.
                 */
                public Builder keyOperations(final Set<KeyOperation> ops) {

                        this.ops = ops;
                        return this;
                }


                /**
                 * Sets the intended JOSE algorithm ({@code alg}) for the JWK.
                 *
                 * @param alg The intended JOSE algorithm, {@code null} if not 
                 *            specified.
                 *
                 * @return This builder.
                 */
                public Builder algorithm(final Algorithm alg) {

                        this.alg = alg;
                        return this;
                }

                /**
                 * Sets the ID ({@code kid}) of the JWK. The key ID can be used 
                 * to match a specific key. This can be used, for instance, to 
                 * choose a key within a {@link JWKSet} during key rollover. 
                 * The key ID may also correspond to a JWS/JWE {@code kid} 
                 * header parameter value.
                 *
                 * @param kid The key ID, {@code null} if not specified.
                 *
                 * @return This builder.
                 */
                public Builder keyID(final String kid) {

                        this.kid = kid;
                        return this;
                }


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

                        this.x5u = x5u;
                        return this;
                }


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

                        this.x5t = x5t;
                        return this;
                }

                /**
                 * Sets the X.509 certificate chain ({@code x5c}) of the JWK.
                 *
                 * @param x5c The X.509 certificate chain as a unmodifiable 
                 *            list, {@code null} if not specified.
                 *
                 * @return This builder.
                 */
                public Builder x509CertChain(final List<Base64> x5c) {

                        this.x5c = x5c;
                        return this;
                }

                /**
                 * Builds a new octet sequence JWK.
                 *
                 * @return The octet sequence JWK.
                 *
                 * @throws IllegalStateException If the JWK parameters were
                 *                               inconsistently specified.
                 */
                public OctetSequenceKey build() {

                        try {
                                return new OctetSequenceKey(k, use, ops, alg, kid, x5u, x5t, x5c);

                        } catch (IllegalArgumentException e) {

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

        
        /**
         * Creates a new octet sequence JSON Web Key (JWK) with the specified
         * parameters.
         *
         * @param k   The key value. It is represented as the Base64URL 
         *            encoding of the value's big endian representation. Must
         *            not be {@code null}.
         * @param use The key use, {@code null} if not specified or if the key
         *            is intended for signing as well as encryption.
         * @param ops The key operations, {@code null} if not specified.
         * @param alg The intended JOSE algorithm for the key, {@code null} if
         *            not specified.
         * @param kid The key ID. {@code null} if not specified.
         * @param x5u The X.509 certificate URL, {@code null} if not specified.
         * @param x5t The X.509 certificate thumbprint, {@code null} if not
         *            specified.
         * @param x5c The X.509 certificate chain, {@code null} if not 
         *            specified.
         */
        public OctetSequenceKey(final Base64URL k,
                                final KeyUse use, final Set<KeyOperation> ops, final Algorithm alg, final String kid,
                                final URI x5u, final Base64URL x5t, final List<Base64> x5c) {
        
                super(KeyType.OCT, use, ops, alg, kid, x5u, x5t, x5c);

                if (k == null) {
                        throw new IllegalArgumentException("The key value must not be null");
                }

                this.k = k;
        }
    

        /**
         * Returns the value of this octet sequence key. 
         *
         * @return The key value. It is represented as the Base64URL encoding
         *         of the value's big endian representation.
         */
        public Base64URL getKeyValue() {

                return k;
        }
        
        
        /**
         * Returns a copy of this octet sequence key value as a byte array.
         * 
         * @return The key value as a byte array.
         */
        public byte[] toByteArray() {

                return getKeyValue().decode();
        }


        /**
         * Returns a secret key representation of this octet sequence key.
         *
         * @return The secret key representation, with an algorithm set to
         *         {@code NONE}.
         */
        public SecretKey toSecretKey() {

                return toSecretKey("NONE");
        }


        /**
         * Returns a secret key representation of this octet sequence key with
         * the specified Java Cryptography Architecture (JCA) algorithm.
         *
         * @param jcaAlg The JCA algorithm. Must not be {@code null}.
         *
         * @return The secret key representation.
         */
        public SecretKey toSecretKey(final String jcaAlg) {

                return new SecretKeySpec(toByteArray(), jcaAlg);
        }


        @Override
        public Base64URL computeThumbprint(final String hashAlg)
                throws JOSEException {

                JSONObject o = new JSONObject();
                o.put("k", k.toString());
                o.put("kty", getKeyType().toString());
                MessageDigest md;

                try {
                        md = MessageDigest.getInstance(hashAlg);
                } catch (NoSuchAlgorithmException e) {
                        throw new JOSEException("Unsupported hash algorithm: " + e.getMessage(), e);
                }

                md.update(o.toJSONString().getBytes(Charset.forName("UTF-8")));

                return Base64URL.encode(md.digest());
        }


        /**
         * Octet sequence (symmetric) keys are never considered public, this 
         * method always returns {@code true}.
         *
         * @return {@code true}
         */
        @Override
        public boolean isPrivate() {

                return true;
        }


        /**
         * Octet sequence (symmetric) keys are never considered public, this 
         * method always returns {@code null}.
         *
         * @return {@code null}
         */
        @Override
        public OctetSequenceKey toPublicJWK() {

                return null;
        }
        

        @Override
        public JSONObject toJSONObject() {

                JSONObject o = super.toJSONObject();

                // Append key value
                o.put("k", k.toString());
                
                return o;
        }


        /**
         * Parses an octet sequence JWK from the specified JSON object string 
         * representation.
         *
         * @param s The JSON object string to parse. Must not be {@code null}.
         *
         * @return The octet sequence JWK.
         *
         * @throws ParseException If the string couldn't be parsed to an octet
         *                        sequence JWK.
         */
        public static OctetSequenceKey parse(final String s)
                throws ParseException {

                return parse(JSONObjectUtils.parseJSONObject(s));
        }

        
        /**
         * Parses an octet sequence JWK from the specified JSON object 
         * representation.
         *
         * @param jsonObject The JSON object to parse. Must not be 
         *                   @code null}.
         *
         * @return The octet sequence JWK.
         *
         * @throws ParseException If the JSON object couldn't be parsed to an
         *                        octet sequence JWK.
         */
        public static OctetSequenceKey parse(final JSONObject jsonObject) 
                throws ParseException {

                // Parse the mandatory parameters first
                Base64URL k = new Base64URL(JSONObjectUtils.getString(jsonObject, "k"));

                // Check key type
                KeyType kty = JWKMetadata.parseKeyType(jsonObject);

                if (kty != KeyType.OCT) {

                        throw new ParseException("The key type \"kty\" must be oct", 0);
                }

                return new OctetSequenceKey(k,
                        JWKMetadata.parseKeyUse(jsonObject),
                        JWKMetadata.parseKeyOperations(jsonObject),
                        JWKMetadata.parseAlgorithm(jsonObject),
                        JWKMetadata.parseKeyID(jsonObject),
                        JWKMetadata.parseX509CertURL(jsonObject),
                        JWKMetadata.parseX509CertThumbprint(jsonObject),
                        JWKMetadata.parseX509CertChain(jsonObject));
        }
}