Telegram bot in D

bot.d

import std.stdio;
import std.string;
import requests;
import std.json;
import std.typecons: tuple, Tuple;
import std.conv;
import std.process;

string URL = "";
enum SLEEP = false;

string getUrl(string url)
{
	return getContent(url).toString();
}

auto getJsonFromUrl(string url)
{
	return parseJSON(getUrl(url));
}

auto getUpdates(long lastUpdateId)
{
	string url = URL ~ "getUpdates?timeout=10";
	if (-1 != lastUpdateId) {
		url = url ~ "&offset=" ~ to!string(lastUpdateId);
	}
	return getJsonFromUrl(url);
}

auto getLastChatIdAndText(JSONValue updates)
{
	updates.writeln;
	auto lastUpdate = updates["result"].array.length - 1;
	if ("group_chat_created" in updates["result"][lastUpdate]["message"]) {
		return tuple("", -1L);
	}
	auto text = updates["result"][lastUpdate]["message"]["text"].str;
	auto chat_id = updates["result"][lastUpdate]["message"]["chat"]["id"].integer;
	return tuple(text, chat_id);
}

auto sendMessage(string text, long chat_id)
{
	string url = URL ~ "sendMessage?text=%s&chat_id=%s".format(text, chat_id);
	getUrl(url);
}

void respond(JSONValue update)
{
	if ("message" !in update) return;

	auto chatId = update["message"]["chat"]["id"].integer;

	switch(update["message"]["from"]["first_name"].str) {
		case "Dan":
			sendMessage("Good day to you!", chatId);
			return;
		default:
			if (SLEEP) {
				sendMessage("I am sleeping, leave me alone", chatId);
				return;
			} else {
				sendMessage("Hey there", chatId);
				return;
			}
	}
}

void main()
{
	string TOKEN = environment.get("TOKEN");
	URL = "https://api.telegram.org/bot%s/".format(TOKEN);

	long lastUpdateId = -1;
	while (true) {
		auto updates = getUpdates(lastUpdateId);
		if ("result" !in updates) {
			continue;
		}
		JSONValue result = updates["result"];
		
		foreach (update; result.array) {
			update.writeln;
			lastUpdateId = update["update_id"].integer + 1;
			respond(update);
		}
	}
}