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


/**
 * Payload with JSON object, string, byte array and Base64URL views. Represents
 * the original object that was signed with JWS or encrypted with JWE. This 
 * class is immutable.
 *
 * <p>Non-initial views are created on demand to conserve resources.
 *
 * <p>UTF-8 is the character set for all conversions between strings and byte
 * arrays.
 *
 * <p>Conversion relations:
 *
 * <pre>
 * JSONObject <=> String <=> Base64URL
 *                       <=> byte[]
 * </pre>
 *
 * @author Vladimir Dzhuvinov
 * @version $version$ (2013-05-16)
 */
@Immutable
public class Payload {


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


        /**
         * 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 view.
         */
        private JSONObject jsonView = null;


        /**
         * The string view.
         */
        private String stringView = null;


        /**
         * The byte array view.
         */
        private byte[] bytesView = null;


        /**
         * The Base64URL view.
         */
        private Base64URL base64URLView = null;


        /**
         * 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) {

                if (bytes == null) {

                        return null;
                }

                return new String(bytes, CHARSET);
        }


        /**
         * 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) {

                if (string == null) {

                        return null;
                }

                return string.getBytes(CHARSET);
        }


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

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

                jsonView = json;

                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");
                }

                stringView = string;

                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");
                }

                bytesView = bytes;

                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");
                }

                base64URLView = base64URL;

                origin = Origin.BASE64URL;
        }


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

                return origin;
        }


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

                if (jsonView != null) {

                        return jsonView;
                }

                // Convert
                if (stringView != null) {

                        try {
                                jsonView = JSONObjectUtils.parseJSONObject(stringView);

                        } catch (ParseException e) {

                                // jsonView remains null
                        }

                } else if (bytesView != null) {

                        stringView = byteArrayToString(bytesView);

                        try {
                                jsonView = JSONObjectUtils.parseJSONObject(stringView);

                        } catch (ParseException e) {

                                // jsonView remains null
                        }

                } else if (base64URLView != null) {

                        stringView = base64URLView.decodeToString();

                        try {
                                jsonView = JSONObjectUtils.parseJSONObject(stringView);

                        } catch (ParseException e) {

                                // jsonView remains null
                        }
                }

                return jsonView;
        }


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

                if (stringView != null) {

                        return stringView;
                }

                // Convert
                if (jsonView != null) {

                        stringView = jsonView.toString();

                } else if (bytesView != null) {

                        stringView = byteArrayToString(bytesView);

                } else if (base64URLView != null) {

                        stringView = base64URLView.decodeToString();
                }

                return stringView;
        }


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

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

                // Convert
                if (stringView != null) {

                        bytesView = stringToByteArray(stringView);

                } else if (jsonView != null) {

                        stringView = jsonView.toString();
                        bytesView = stringToByteArray(stringView);

                } else if (base64URLView != null) {

                        bytesView = base64URLView.decode();
                }

                return bytesView;       
        }


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

                if (base64URLView != null) {

                        return base64URLView;
                }

                // Convert

                if (stringView != null) {

                        base64URLView = Base64URL.encode(stringView);

                } else if (bytesView != null) {

                        base64URLView = Base64URL.encode(bytesView);

                } else if (jsonView != null) {

                        stringView = jsonView.toString();
                        base64URLView = Base64URL.encode(stringView);
                }

                return base64URLView;
        }
}