/* gpgme.js - Javascript integration for gpgme
 * Copyright (C) 2018 Bundesamt für Sicherheit in der Informationstechnik
 *
 * This file is part of GPGME.
 *
 * GPGME is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * GPGME is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, see <http://www.gnu.org/licenses/>.
 * SPDX-License-Identifier: LGPL-2.1+
 *
 * Author(s):
 *     Maximilian Krambach <mkrambach@intevation.de>
 */

import { permittedOperations } from './permittedOperations';
import { gpgme_error } from './Errors';
import { Connection } from './Connection';

/**
 * Initializes a message for gnupg, validating the message's purpose with
 *   {@link permittedOperations} first
 * @param {String} operation
 * @returns {GPGME_Message|GPGME_Error} The Message object
 */
export function createMessage(operation){
    if (typeof(operation) !== 'string'){
        return gpgme_error('PARAM_WRONG');
    }
    if (permittedOperations.hasOwnProperty(operation)){
        return Object.freeze(new GPGME_Message(operation));
    } else {
        return gpgme_error('MSG_WRONG_OP');
    }
}

/**
 * A Message collects, validates and handles all information required to
 * successfully establish a meaningful communication with gpgme-json via
 * {@link Connection.post}. The definition on which communication is available
 * can be found in {@link permittedOperations}.
 * @class
 */
export class GPGME_Message {

    constructor(operation){
        let _msg = {
            op: operation,
            chunksize: 1023* 1024
        };
        let expected = null;

        this.getOperation = function(){
            return _msg.op;
        };

        this.setExpect = function(value){
            if (value === 'base64'){
                expected = value;
            }
        };
        this.getExpect = function(){
            return expected;
        };

        /**
         * The maximum size of responses from gpgme in bytes. As of July 2018,
         * most browsers will only accept answers up to 1 MB of size.
         * Everything above that threshold will not pass through
         * nativeMessaging; answers that are larger need to be sent in parts.
         * The lower limit is set to 10 KB. Messages smaller than the threshold
         * will not encounter problems, larger messages will be received in
         * chunks. If the value is not explicitly specified, 1023 KB is used.
         */
        this.setChunksize = function (value){
            if (
                Number.isInteger(value) &&
                value > 10 * 1024 &&
                value <= 1024 * 1024
            ){
                _msg.chunksize = value;
            }
        };

        this.getMsg = function(){
            return _msg;
        };

        this.getChunksize= function() {
            return _msg.chunksize;
        };

        /**
         * Sets a parameter for the message. It validates with
         *      {@link permittedOperations}
         * @param {String} param Parameter to set
         * @param {any} value Value to set
         * @returns {Boolean} If the parameter was set successfully
         */
        this.setParameter = function ( param,value ){
            if (!param || typeof(param) !== 'string'){
                return gpgme_error('PARAM_WRONG');
            }
            let po = permittedOperations[_msg.op];
            if (!po){
                return gpgme_error('MSG_WRONG_OP');
            }
            let poparam = null;
            if (po.required.hasOwnProperty(param)){
                poparam = po.required[param];
            } else if (po.optional.hasOwnProperty(param)){
                poparam = po.optional[param];
            } else {
                return gpgme_error('PARAM_WRONG');
            }
            // check incoming value for correctness
            let checktype = function(val){
                switch(typeof(val)){
                case 'string':
                    if (poparam.allowed.indexOf(typeof(val)) >= 0
                            && val.length > 0) {
                        return true;
                    }
                    return gpgme_error('PARAM_WRONG');
                case 'number':
                    if (
                        poparam.allowed.indexOf('number') >= 0
                            && isNaN(value) === false){
                        return true;
                    }
                    return gpgme_error('PARAM_WRONG');

                case 'boolean':
                    if (poparam.allowed.indexOf('boolean') >= 0){
                        return true;
                    }
                    return gpgme_error('PARAM_WRONG');
                case 'object':
                    if (Array.isArray(val)){
                        if (poparam.array_allowed !== true){
                            return gpgme_error('PARAM_WRONG');
                        }
                        for (let i=0; i < val.length; i++){
                            let res = checktype(val[i]);
                            if (res !== true){
                                return res;
                            }
                        }
                        if (val.length > 0) {
                            return true;
                        }
                    } else if (val instanceof Uint8Array){
                        if (poparam.allowed.indexOf('Uint8Array') >= 0){
                            return true;
                        }
                        return gpgme_error('PARAM_WRONG');
                    } else {
                        return gpgme_error('PARAM_WRONG');
                    }
                    break;
                default:
                    return gpgme_error('PARAM_WRONG');
                }
            };
            let typechecked = checktype(value);
            if (typechecked !== true){
                return typechecked;
            }
            if (poparam.hasOwnProperty('allowed_data')){
                if (poparam.allowed_data.indexOf(value) < 0){
                    return gpgme_error('PARAM_WRONG');
                }
            }
            _msg[param] = value;
            return true;
        };



        /**
         * Check if the message has the minimum requirements to be sent, that is
         * all 'required' parameters according to {@link permittedOperations}.
         * @returns {Boolean} true if message is complete.
         */
        this.isComplete = function(){
            if (!_msg.op){
                return false;
            }
            let reqParams = Object.keys(
                permittedOperations[_msg.op].required);
            let msg_params = Object.keys(_msg);
            for (let i=0; i < reqParams.length; i++){
                if (msg_params.indexOf(reqParams[i]) < 0){
                    return false;
                }
            }
            return true;
        };
        /**
         * Sends the Message via nativeMessaging and resolves with the answer.
         * @returns {Promise<Object|GPGME_Error>}
         * @async
         */
        this.post = function(){
            let me = this;
            return new Promise(function(resolve, reject) {
                if (me.isComplete() === true) {

                    let conn  = Object.freeze(new Connection);
                    conn.post(me).then(function(response) {
                        resolve(response);
                    }, function(reason) {
                        reject(reason);
                    });
                }
                else {
                    reject(gpgme_error('MSG_INCOMPLETE'));
                }
            });
        };
    }

    /**
     * Returns the prepared message with parameters and completeness checked
     * @returns {Object|null} Object to be posted to gnupg, or null if
     * incomplete
     */
    get message(){
        if (this.isComplete() === true){
            return this.getMsg();
        }
        else {
            return null;
        }
    }
    get operation(){
        return this.getOperation();
    }
    get chunksize(){
        return this.getChunksize();
    }
}