package com.nimbusds.jose;


import java.nio.charset.Charset;
import java.text.ParseException;

import net.jcip.annotations.Immutable;

import net.minidev.json.JSONObject;

import com.nimbusds.jwt.SignedJWT;

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


/**
 * Payload of an unsecured (plain), JSON Web Signature (JWS) or JSON Web
 * Encryption (JWE) object. Supports JSON object, string, byte array,
 * Base64URL, JWS object and signed JWT payload representations. This class is
 * immutable.
 *
 * <p>UTF-8 is the character set for all conversions between strings and byte
 * arrays.
 *
 * <p>Conversion relations:
 *
 * <pre>
 * JSONObject <=> String <=> Base64URL
 *                       <=> byte[]
 *                       <=> JWSObject
 *                       <=> SignedJWT
 * </pre>
 *
 * @author Vladimir Dzhuvinov
 * @version 2015-07-23
 */
@Immutable
public final class Payload {


        /**
         * Enumeration of the original data types used to create a 
         * {@link Payload}.
         */
        public enum Origin {


                /**
                 * The payload was created from a JSON object.
                 */
                JSON,


                /**
                 * The payload was created from a string.
                 */
                STRING,


                /**
                 * The payload was created from a byte array.
                 */
                BYTE_ARRAY,


                /**
                 * The payload was created from a Base64URL-encoded object.
                 */
                BASE64URL,


                /**
                 * The payload was created from a JWS object.
                 */
                JWS_OBJECT,


                /**
                 * The payload was created from a signed JSON Web Token (JWT).
                 */
                SIGNED_JWT
        }


        /**
         * UTF-8 is the character set for all conversions between strings and
         * byte arrays.
         */
        private static final Charset CHARSET = Charset.forName("UTF-8");


        /**
         * The original payload data type.
         */
        private Origin origin;


        /**
         * The JSON object representation.
         */
        private final JSONObject jsonObject;


        /**
         * The string representation.
         */
        private final String string;


        /**
         * The byte array representation.
         */
        private final byte[] bytes;


        /**
         * The Base64URL representation.
         */
        private final Base64URL base64URL;


        /**
         * The JWS object representation.
         */
        private final JWSObject jwsObject;


        /**
         * The signed JWT representation.
         */
        private final SignedJWT signedJWT;


        /**
         * Converts a byte array to a string using {@link #CHARSET}.
         *
         * @param bytes The byte array to convert. May be {@code null}.
         *
         * @return The resulting string, {@code null} if conversion failed.
         */
        private static String byteArrayToString(final byte[] bytes) {

                return bytes != null ? new String(bytes, CHARSET) : null;
        }


        /**
         * Converts a string to a byte array using {@link #CHARSET}.
         *
         * @param string The string to convert. May be {@code null}.
         *
         * @return The resulting byte array, {@code null} if conversion failed.
         */
        private static byte[] stringToByteArray(final String string) {

                return string != null ? string.getBytes(CHARSET) : null;
        }


        /**
         * Creates a new payload from the specified JSON object.
         *
         * @param jsonObject The JSON object representing the payload. Must not
         *                   be {@code null}.
         */
        public Payload(final JSONObject jsonObject) {

                if (jsonObject == null) {
                        throw new IllegalArgumentException("The JSON object must not be null");
                }

                this.jsonObject = jsonObject;
                string = null;
                bytes = null;
                base64URL = null;
                jwsObject = null;
                signedJWT = null;

                origin = Origin.JSON;
        }


        /**
         * Creates a new payload from the specified string.
         *
         * @param string The string representing the payload. Must not be 
         *               {@code null}.
         */
        public Payload(final String string) {

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

                jsonObject = null;
                this.string = string;
                bytes = null;
                base64URL = null;
                jwsObject = null;
                signedJWT = null;

                origin = Origin.STRING;
        }


        /**
         * Creates a new payload from the specified byte array.
         *
         * @param bytes The byte array representing the payload. Must not be 
         *              {@code null}.
         */
        public Payload(final byte[] bytes) {

                if (bytes == null) {
                        throw new IllegalArgumentException("The byte array must not be null");
                }

                jsonObject = null;
                string = null;
                this.bytes = bytes;
                base64URL = null;
                jwsObject = null;
                signedJWT = null;

                origin = Origin.BYTE_ARRAY;
        }


        /**
         * Creates a new payload from the specified Base64URL-encoded object.
         *
         * @param base64URL The Base64URL-encoded object representing the 
         *                  payload. Must not be {@code null}.
         */
        public Payload(final Base64URL base64URL) {

                if (base64URL == null) {
                        throw new IllegalArgumentException("The Base64URL-encoded object must not be null");
                }

                jsonObject = null;
                string = null;
                bytes = null;
                this.base64URL = base64URL;
                jwsObject = null;
                signedJWT = null;

                origin = Origin.BASE64URL;
        }


        /**
         * Creates a new payload from the specified JWS object. Intended for
         * signed then encrypted JOSE objects.
         *
         * @param jwsObject The JWS object representing the payload. Must be in
         *                  a signed state and not {@code null}.
         */
        public Payload(final JWSObject jwsObject) {

                if (jwsObject == null) {
                        throw new IllegalArgumentException("The JWS object must not be null");
                }

                if (jwsObject.getState() == JWSObject.State.UNSIGNED) {
                        throw new IllegalArgumentException("The JWS object must be signed");
                }

                jsonObject = null;
                string = null;
                bytes = null;
                base64URL = null;
                this.jwsObject = jwsObject;
                signedJWT = null;

                origin = Origin.JWS_OBJECT;
        }


        /**
         * Creates a new payload from the specified signed JSON Web Token
         * (JWT). Intended for signed then encrypted JWTs.
         *
         * @param signedJWT The signed JWT representing the payload. Must be in
         *                  a signed state and not {@code null}.
         */
        public Payload(final SignedJWT signedJWT) {

                if (signedJWT == null) {
                        throw new IllegalArgumentException("The signed JWT must not be null");
                }

                if (signedJWT.getState() == JWSObject.State.UNSIGNED) {
                        throw new IllegalArgumentException("The JWT must be signed");
                }

                jsonObject = null;
                string = null;
                bytes = null;
                base64URL = null;
                this.signedJWT = signedJWT;
                jwsObject = signedJWT; // The signed JWT is also a JWS

                origin = Origin.SIGNED_JWT;
        }


        /**
         * Gets the original data type used to create this payload.
         *
         * @return The payload origin.
         */
        public Origin getOrigin() {

                return origin;
        }


        /**
         * Returns a JSON object representation of this payload.
         *
         * @return The JSON object representation, {@code null} if the payload
         *         couldn't be converted to a JSON object.
         */
        public JSONObject toJSONObject() {

                if (jsonObject != null) {
                        return jsonObject;
                }

                // Convert

                String s = toString();

                if (s == null) {
                        // to string conversion failed
                        return null;
                }

                try {
                        return JSONObjectUtils.parseJSONObject(s);

                } catch (ParseException e) {
                        // Payload not a JSON object
                        return null;
                }
        }


        /**
         * Returns a string representation of this payload.
         *
         * @return The string representation.
         */
        @Override
        public String toString() {

                if (string != null) {

                        return string;
                }

                // Convert
                if (jwsObject != null) {

                        if (jwsObject.getParsedString() != null) {
                                return jwsObject.getParsedString();
                        } else {
                                return jwsObject.serialize();
                        }

                } else if (jsonObject != null) {

                        return jsonObject.toString();

                } else if (bytes != null) {

                        return byteArrayToString(bytes);

                } else if (base64URL != null) {

                        return base64URL.decodeToString();
                } else {
                        return null; // should never happen
                }
        }


        /**
         * Returns a byte array representation of this payload.
         *
         * @return The byte array representation.
         */
        public byte[] toBytes() {

                if (bytes != null) {
                        return bytes;
                }

                // Convert
                if (base64URL != null) {
                        return base64URL.decode();

                }

                return stringToByteArray(toString());
        }


        /**
         * Returns a Base64URL representation of this payload.
         *
         * @return The Base64URL representation.
         */
        public Base64URL toBase64URL() {

                if (base64URL != null) {
                        return base64URL;
                }

                // Convert
                return Base64URL.encode(toBytes());
        }


        /**
         * Returns a JWS object representation of this payload. Intended for
         * signed then encrypted JOSE objects.
         *
         * @return The JWS object representation, {@code null} if the payload
         *         couldn't be converted to a JWS object.
         */
        public JWSObject toJWSObject() {

                if (jwsObject != null) {
                        return jwsObject;
                }

                try {
                        return JWSObject.parse(toString());

                } catch (ParseException e) {

                        return null;
                }
        }


        /**
         * Returns a signed JSON Web Token (JWT) representation of this
         * payload. Intended for signed then encrypted JWTs.
         *
         * @return The signed JWT representation, {@code null} if the payload
         *         couldn't be converted to a signed JWT.
         */
        public SignedJWT toSignedJWT() {

                if (signedJWT != null) {
                        return signedJWT;
                }

                try {
                        return SignedJWT.parse(toString());

                } catch (ParseException e) {

                        return null;
                }
        }


        /**
         * Returns a transformation of this payload.
         *
         * @param transformer The payload transformer. Must not be
         *                    {@code null}.
         *
         * @return The transformed payload.
         */
        public <T> T toType(final PayloadTransformer<T> transformer) {

                return transformer.transform(this);
        }
}