var readline = require("readline");
var util = require("util");

require("colors");
var espree = require("espree");

var complete = line => {
    var tokens = line.split(/ /).filter(i => i);

    if (!tokens.length) return [[], line];

    var targetToken = tokens[tokens.length - 1];

    var namespace = global;
    var filterPrefix = targetToken;

    var targetObject;
    if (targetToken.includes(".")) {

        targetObject = targetToken.split('.');
        filterPrefix = targetObject.pop();
        targetObject = targetObject.join(".");

        if (!targetObject) return [[], line];

        try {
            namespace = eval(targetObject);
        } catch (e) {
            return [[], line];
        };
    };

    var completions = Object
        .getOwnPropertyNames(namespace)
        .filter(i => i.startsWith(filterPrefix));

    if (targetObject) {
        completions = completions.map(i => targetObject + "." + i);
    };
    return [completions, line];
};

module.exports = async function () {
    console.log("interactive mode".yellow);

    var rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout,
        completer: complete,
    });

    var origGlobals = {};
    var isFinished = false;

    while (!isFinished) {
        isFinished = await new Promise((resolve, reject) => {
            rl.question("> ".red, answer => {

                if (answer === "exit") {
                    console.log("emergency exit".red)
                    process.exit(1);
                };

                if (answer === "go") {
                    console.log("continue execution".green);
                    resolve(true);
                    return;
                };

                if (["help", "h"].includes(answer)) {
                    console.log(("In interactive mode you may execute any nodejs code.\n" +
                                 "Also next commands are available:\n" +
                                 "- h, help - show interactive mode help;\n" +
                                 "- go - continue code execution;\n" +
                                 "- exit - finish current nodejs process;").white);
                    resolve(false);
                    return;
                };

                var ast, varName;

                try {
                    ast = espree.parse(answer, { ecmaVersion: 9 });
                    varName = ast.body[0].expression.left.name;
                } catch (e) {
                    try {
                        varName = ast.body[0].declarations[0].id.name;
                    } catch (e) {};
                };

                Promise
                    .resolve()
                    .then(() => {
                        var result = eval(answer);
                        if (varName) {
                            if (!Object.keys(origGlobals).includes(varName)) {
                                origGlobals[varName] = global[varName];
                            };
                            global[varName] = eval(varName);
                        };
                        return result;
                    })
                    .then(result => console.log(util.format(result).yellow))
                    .catch(e => console.log(util.format(e).red))
                    .then(() => resolve(false));
            });
        });
    };

    for (var [k, v] of Object.entries(origGlobals)) {
        global[k] = v;
    };
};