package com.nimbusds.jose;


import java.io.Serializable;
import java.text.ParseException;

import net.minidev.json.JSONObject;

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


/**
 * The base abstract class for unsecured (plain / {@code alg=none}), JSON Web
 * Signature (JWS) secured and JSON Web Encryption (JWE) secured objects.
 *
 * @author Vladimir Dzhuvinov
 * @version 2015-06-10
 */
public abstract class JOSEObject implements Serializable {
        
        
        private static final long serialVersionUID = 1L;


        /**
         * The MIME type of JOSE objects serialised to a compact form:
         * {@code application/jose; charset=UTF-8}
         */
        public static final String MIME_TYPE_COMPACT = "application/jose; charset=UTF-8";


        /**
         * The MIME type of JOSE objects serialised to a JSON object form:
         * {@code application/jose+json; charset=UTF-8}
         */
        public static final String MIME_TYPE_JS = "application/jose+json; charset=UTF-8";


        /**
         * The payload (message), {@code null} if not specified.
         */
        private Payload payload;


        /**
         * The original parsed Base64URL parts, {@code null} if the JOSE object 
         * was created from scratch. The individual parts may be empty or 
         * {@code null} to indicate a missing part.
         */
        private Base64URL[] parsedParts;


        /**
         * Creates a new JOSE object. The payload and the original parsed 
         * Base64URL parts are not defined.
         */
        protected JOSEObject() {

                payload = null;
                parsedParts = null;
        }


        /**
         * Creates a new JOSE object with the specified payload.
         *
         * @param payload The payload, {@code null} if not available (e.g for 
         *                an encrypted JWE object).
         */
        protected JOSEObject(final Payload payload) {

                this.payload = payload;
        }


        /**
         * Returns the header of this JOSE object.
         *
         * @return The header.
         */
        public abstract Header getHeader();


        /**
         * Sets the payload of this JOSE object.
         *
         * @param payload The payload, {@code null} if not available (e.g. for 
         *                an encrypted JWE object).
         */
        protected void setPayload(final Payload payload) {

                this.payload = payload;
        }


        /**
         * Returns the payload of this JOSE object.
         *
         * @return The payload, {@code null} if not available (for an encrypted
         *         JWE object that hasn't been decrypted).
         */
        public Payload getPayload() {

                return payload;
        }


        /**
         * Sets the original parsed Base64URL parts used to create this JOSE 
         * object.
         *
         * @param parts The original Base64URL parts used to creates this JOSE
         *              object, {@code null} if the object was created from
         *              scratch. The individual parts may be empty or 
         *              {@code null} to indicate a missing part.
         */
        protected void setParsedParts(final Base64URL... parts) {

                parsedParts = parts;
        }


        /**
         * Returns the original parsed Base64URL parts used to create this JOSE
         * object.
         *
         * @return The original Base64URL parts used to creates this JOSE 
         *         object, {@code null} if the object was created from scratch. 
         *         The individual parts may be empty or {@code null} to 
         *         indicate a missing part.
         */
        public Base64URL[] getParsedParts() {

                return parsedParts;
        }


        /**
         * Returns the original parsed string used to create this JOSE object.
         *
         * @see #getParsedParts
         * 
         * @return The parsed string used to create this JOSE object, 
         *         {@code null} if the object was creates from scratch.
         */
        public String getParsedString() {

                if (parsedParts == null) {
                        return null;
                }

                StringBuilder sb = new StringBuilder();

                for (Base64URL part: parsedParts) {

                        if (sb.length() > 0) {
                                sb.append('.');
                        }

                        if (part != null) {
                                sb.append(part.toString());
                        }
                }

                return sb.toString();
        }


        /**
         * Serialises this JOSE object to its compact format consisting of 
         * Base64URL-encoded parts delimited by period ('.') characters.
         *
         * @return The serialised JOSE object.
         *
         * @throws IllegalStateException If the JOSE object is not in a state 
         *                               that permits serialisation.
         */
        public abstract String serialize();


        /**
         * Splits a compact serialised JOSE object into its Base64URL-encoded
         * parts.
         *
         * @param s The compact serialised JOSE object to split. Must not be
         *          {@code null}.
         *
         * @return The JOSE Base64URL-encoded parts (three for unsecured and
         *         JWS objects, five for JWE objects).
         *
         * @throws ParseException If the specified string couldn't be split 
         *                        into three or five Base64URL-encoded parts.
         */
        public static Base64URL[] split(final String s)
                throws ParseException {

                // We must have 2 (JWS) or 4 dots (JWE)

                // String.split() cannot handle empty parts
                final int dot1 = s.indexOf(".");

                if (dot1 == -1) {
                        throw new ParseException("Invalid serialized unsecured/JWS/JWE object: Missing part delimiters", 0);
                }

                final int dot2 = s.indexOf(".", dot1 + 1);

                if (dot2 == -1) {
                        throw new ParseException("Invalid serialized unsecured/JWS/JWE object: Missing second delimiter", 0);
                }

                // Third dot for JWE only
                final int dot3 = s.indexOf(".", dot2 + 1);

                if (dot3 == -1) {

                        // Two dots only? -> We have a JWS
                        Base64URL[] parts = new Base64URL[3];
                        parts[0] = new Base64URL(s.substring(0, dot1));
                        parts[1] = new Base64URL(s.substring(dot1 + 1, dot2));
                        parts[2] = new Base64URL(s.substring(dot2 + 1));
                        return parts;
                }

                // Fourth final dot for JWE
                final int dot4 = s.indexOf(".", dot3 + 1);

                if (dot4 == -1) {
                        throw new ParseException("Invalid serialized JWE object: Missing fourth delimiter", 0);
                }

                if (dot4 != -1 && s.indexOf(".", dot4 + 1) != -1) {
                        throw new ParseException("Invalid serialized unsecured/JWS/JWE object: Too many part delimiters", 0);
                }

                // Four dots -> five parts
                Base64URL[] parts = new Base64URL[5];
                parts[0] = new Base64URL(s.substring(0, dot1));
                parts[1] = new Base64URL(s.substring(dot1 + 1, dot2));
                parts[2] = new Base64URL(s.substring(dot2 + 1, dot3));
                parts[3] = new Base64URL(s.substring(dot3 + 1, dot4));
                parts[4] = new Base64URL(s.substring(dot4 + 1));
                return parts;
        }


        /**
         * Parses a JOSE object from the specified string in compact format.
         *
         * @param s The string to parse. Must not be {@code null}.
         *
         * @return The corresponding {@link PlainObject}, {@link JWSObject} or
         *         {@link JWEObject} instance.
         *
         * @throws ParseException If the string couldn't be parsed to a valid 
         *                        unsecured, JWS or JWE object.
         */
        public static JOSEObject parse(final String s) 
                throws ParseException {

                Base64URL[] parts = split(s);

                JSONObject jsonObject;

                try {
                        jsonObject = JSONObjectUtils.parse(parts[0].decodeToString());

                } catch (ParseException e) {

                        throw new ParseException("Invalid unsecured/JWS/JWE header: " + e.getMessage(), 0);
                }

                Algorithm alg = Header.parseAlgorithm(jsonObject);

                if (alg.equals(Algorithm.NONE)) {
                        return PlainObject.parse(s);
                } else if (alg instanceof JWSAlgorithm) {
                        return JWSObject.parse(s);
                } else if (alg instanceof JWEAlgorithm) {
                        return JWEObject.parse(s);
                } else {
                        throw new AssertionError("Unexpected algorithm type: " + alg);
                }
        }
}