import UIUtil from '../../util/UIUtil';
import UIEvents from '../../../../service/UI/UIEvents';

/**
 * List with supported commands. The keys are the names of the commands and
 * the value is the function that processes the message.
 * @type {{String: function}}
 */
const commands = {
    'topic': processTopic
};

/**
 * Extracts the command from the message.
 * @param message the received message
 * @returns {string} the command
 */
function getCommand(message) {
    if (message) {
        for (const command in commands) {
            if (message.indexOf(`/${command}`) === 0) {
                return command;
            }
        }
    }

    return '';
}

/**
 * Processes the data for topic command.
 * @param commandArguments the arguments of the topic command.
 */
function processTopic(commandArguments, emitter) {
    const topic = UIUtil.escapeHtml(commandArguments);

    emitter.emit(UIEvents.SUBJECT_CHANGED, topic);
}

/**
 * Constructs a new CommandProccessor instance from a message that
 * handles commands received via chat messages.
 * @param message the message
 * @constructor
 */
function CommandsProcessor(message, emitter) {
    const command = getCommand(message);

    this.emitter = emitter;

    /**
     * Returns the name of the command.
     * @returns {String} the command
     */
    this.getCommand = function() {
        return command;
    };


    const messageArgument = message.substr(command.length + 2);

    /**
     * Returns the arguments of the command.
     * @returns {string}
     */
    this.getArgument = function() {
        return messageArgument;
    };
}

/**
 * Checks whether this instance is valid command or not.
 * @returns {boolean}
 */
CommandsProcessor.prototype.isCommand = function() {
    if (this.getCommand()) {
        return true;
    }

    return false;
};

/**
 * Processes the command.
 */
CommandsProcessor.prototype.processCommand = function() {
    if (!this.isCommand()) {
        return;
    }

    commands[this.getCommand()](this.getArgument(), this.emitter);
};

export default CommandsProcessor;