ask-cli/lib/view/cli-repl-view.js

const repl = require('repl');
const SpinnerView = require('@src/view/spinner-view');
const Messenger = require('@src/view/messenger');
const stringUtils = require('@src/utils/string-utils');

module.exports = class CliReplView {
    /**
     * Constructor for CLI REPL View
     * @param {String} prompt What string to display as the prompt for the REPL.
     * @throws {Error} throws error if an undefined configuration is passed.
     * @throws {Error} throws error if prompt is not a non-empty string.
     */
    constructor(configuration) {
        if (!configuration) {
            throw 'Cannot have an undefined configuration.';
        }
        const { prompt, evalFunc, header, footer, prettifyHeaderFooter, inputStream } = configuration;
        this.prompt = prompt || '> ';
        this.eval = evalFunc;
        this.header = header;
        this.footer = footer;
        this.prettifyHeaderFooter = prettifyHeaderFooter || (arg => arg);
        this.inputStream = inputStream || process.stdin;
        this.progressSpinner = new SpinnerView();
        if (!stringUtils.isNonEmptyString(this.prompt)) {
            throw 'Prompt must be a non-empty string.';
        }
        this.printHeaderFooter(this.header);
        // Initialize custom REPL server.
        const replConfig = {
            prompt: this.prompt,
            eval: (cmd, context, filename, callback) => {
                this.eval(cmd, callback);
            },
            ignoreUndefined: true,
            input: this.inputStream,
            output: process.stdout
        };
        this.replServer = repl.start(replConfig);
        this.replServer.removeAllListeners('SIGINT');
        this.clearSpecialCommands();
        this.registerQuitCommand(() => {});
    }

    /**
     * Function to print a header or footer line.
     * @param {String} data the string that contains the information the caller whats to embed into header/footer.
     */
    printHeaderFooter(data) {
        if (stringUtils.isNonEmptyString(data)) {
            Messenger.getInstance().info(this.prettifyHeaderFooter(data));
        }
    }

    /**
     * Register a special command to the repl
     * @param {String} name name of new special command.
     * @param {String} name name of new special command.
     * @param {String} helpMessage description of special command
     * @param {Function} func function to execute when special command received
     * @param {Boolean} displayPrompt specify whether or not to display the prompt after the special command executes. Default: true
     */
    registerSpecialCommand(name, helpMessage, func, displayPrompt) {
        const shouldDisplayPrompt = displayPrompt === undefined ? true : displayPrompt;
        this.replServer.defineCommand(name, {
            help: helpMessage || this.replServer.commands[name].help,
            action: (args) => {
                func(args);
                if (shouldDisplayPrompt) this.replServer.displayPrompt();
            }
        });
    }

    /**
     * Register a special exit command to the repl
     * @param {Function} func function to execute when special command received
     */
    registerQuitCommand(func) {
        this.replServer.removeAllListeners('close');
        this.registerSpecialCommand(
            'quit',
            'Quit repl session.',
            () => {
                this.close();
            },
            false
        );
        this.replServer.on('close', () => {
            func();
            this.progressSpinner.terminate();
            this.printHeaderFooter(this.footer);
        });
    }

    /**
     * Remove all special commands from REPL server
     * Remove close event listeners to remove all quit handlers.
     */
    clearSpecialCommands() {
        this.replServer.commands = { help: this.replServer.commands.help };
        this.replServer.removeAllListeners('close');
    }

    /**
     * Wrapper to close instance. This involves terminating the SpinnerView, disposing the Messenger View, and closing the REPL Server.
     */
    close() {
        this.replServer.close();
    }

    // SpinnerView wrapper functions

    /**
     * Wrapper for starting the SpinnerView with a specified message.
     * @param {String} text text to display when the spinner starts.
     */
    startProgressSpinner(text) {
        this.progressSpinner.start(text);
    }

    /**
     * Wrapper for updating the text of the SpinnerView
     * @param {String} text text to replace current message of spinner.
     */
    updateProgressSpinner(text) {
        this.progressSpinner.update(text);
    }

    /**
     * Wrapper for terminating the SpinnerView, clearing it from the console
     */
    terminateProgressSpinner() {
        this.progressSpinner.terminate();
    }
};