Functional console IO

console.php

<?php
function console() : Closure {
    $prompt = function(string $line) : Closure {
        $genericDefault = function(string $default = null) {
            return function(string $answer) use ($default) {
                if (empty($answer)) {
                    return $default;
                } else {
                    return $answer;
                }
            };
        };

        return function(Closure $default = null) use ($genericDefault, $line) {
            if ($default === null) {
                $default = $genericDefault(null);
            }
            $defaultValueFile = sys_get_temp_dir() . DIRECTORY_SEPARATOR . md5($line);
            if (file_exists($defaultValueFile)) {
                $default = $genericDefault(file_get_contents($defaultValueFile));
            }
            print ($default('') ? ' [' . $default('') . ']' : '') . ': ';
            while (true) {
                $answer = $default(Seld\CliPrompt\CliPrompt::prompt());
                if ($answer !== null) {
                    file_put_contents($defaultValueFile, $answer);
                    break;
                }
                print '↳ ';
            }
            return $answer;
        };
    };
    return function(string $line, bool $new_line = true) use ($prompt) : Closure {
        print ($new_line ? PHP_EOL : '') . $line;
        return $prompt($line);
    };
}

$answer = console("Please enter your name")(function(string $answer) {
    if (empty($answer)) {
        return null;
    }
    return $answer;
});