using System.Reflection;
using Telegram.Bot;
using Telegram.Bot.Types;
using Telegram.Bot.Types.Enums;

var token = Environment.GetEnvironmentVariable("TELEGRAM_BOT_TOKEN")!;
var version = ((AssemblyInformationalVersionAttribute)Assembly.GetEntryAssembly()!.GetCustomAttributes(typeof(AssemblyInformationalVersionAttribute), false)[0])
	.InformationalVersion[6..];

using var cts = new CancellationTokenSource();

var bot = new TelegramBotClient(token);
var me  = await bot.GetMeAsync();

await bot.SetMyCommandsAsync(new[] {
	new BotCommand { Command = "coinflip", Description     = "Flips a coin" },
	new BotCommand { Command = "shouldi", Description      = "Tells you if you should or shouldn't do something" },
	new BotCommand { Command = "yesno", Description        = "Answes binary questions" },
	new BotCommand { Command = "makedecision", Description = "Makes a decision. Expects a list of comma separated options." },
	new BotCommand { Command = "choose", Description       = "Chooses an item. Expects a list of comma separated options." },
	new BotCommand { Command = "spinbottle", Description   = "Spins a bottle (for truth or dare). Expects a list of users participating separated by a space." },
	new BotCommand { Command = "help", Description         = "Lists all commands" },
});

var iBotCommands = new List<string> {
	"coinflip",
	"shouldi",
	"yesno",
	"makedecision",
	"choose",
	"spinbottle",
	"help",
	"start"
};

bot.StartReceiving(HandleUpdateAsync, PollingErrorHandler, null, cts.Token);
Console.WriteLine($"Start listening for @{me.Username}");

var exitEvent = new ManualResetEvent(false);
Console.CancelKeyPress += (sender, eventArgs) => {
	eventArgs.Cancel = true;
	exitEvent.Set();
};
exitEvent.WaitOne();

cts.Cancel();

Task PollingErrorHandler(ITelegramBotClient ibot, Exception ex, CancellationToken ct) {
	Console.WriteLine($"Exception while polling for updates: {ex}");
	return Task.CompletedTask;
}

async Task HandleUpdateAsync(ITelegramBotClient ibot, Update update, CancellationToken ct) {
	try {
		if (update.Type != UpdateType.Message)
			return;

		await BotOnMessageReceived(ibot, update.Message!);
	}
	catch (Exception ex) {
		Console.WriteLine($"Exception while handling {update.Type}: {ex}");
	}
}

async Task BotOnMessageReceived(ITelegramBotClient botClient, Message message) {
	var command = "";
	var query   = "";
	try {
		// if we didn't receive any text, return
		if (string.IsNullOrWhiteSpace(message.Text))
			return;

		// we need to figure out which way of sending commands is being used
		// let's get the first word of the message
		var firstword = message.Text!.Split(" ")[0];

		// is it a slash command?
		if (firstword.StartsWith("/")) {
			// trim explicit username mention
			command = firstword.Replace($"@{me.Username}", "").TrimStart('/');
			// remove command (and optional username) from message text
			query = message.Text?[firstword.Length..];
			// ignore unknown slash commands in groups not explicitly directed at us
			if (!iBotCommands.Contains(command) && message.Chat.Type != ChatType.Private && !firstword.Contains($"@{me.Username}"))
				return;
		}
		else {
			// are we sure the bot is being asked?
			if (message.Chat.Type == ChatType.Private || message.Text!.Contains($"@{me.Username}")) {
				var iquery = message.Text.Replace($"@{me.Username}", "").Trim();
				if (string.IsNullOrWhiteSpace(iquery))
					return;

				// is the first word a command?
				firstword = iquery.Split(" ")[0];
				if (iBotCommands.Contains(firstword)) {
					command = firstword;
					query   = iquery[firstword.Length..];
				}
				else {
					// try to guess what was meant
					if (iquery.ToLowerInvariant().Contains(" or ") && !iquery.Contains(',')) {
						command = "makedecision";
						query   = iquery.Replace(" or ", ",").TrimEnd('?');
					}
					else if (iquery.EndsWith("?")) {
						command = "yesno";
					}
					else if (iquery.ToLowerInvariant().Contains("flip") && iquery.ToLowerInvariant().Contains("coin")) {
						command = "coinflip";
					}
				}
			}
			else {
				// likely not a message meant for us
				return;
			}
		}

		switch (command) {
			case "coinflip":
				await botClient.SendTextMessageAsync(message.Chat.Id, RandomOption(new[] { "Heads", "Tails" }), replyToMessageId: message.MessageId);
				break;
			case "shouldi":
				await botClient.SendTextMessageAsync(message.Chat.Id, RandomOption(new[] { "Go for it!", "Can't hurt to try!", "Probably not.", "I wouldn't recommend it." }),
													 replyToMessageId: message.MessageId);
				break;
			case "yesno":
				await botClient.SendTextMessageAsync(message.Chat.Id, RandomOption(new[] { "Yeah!", "Nah..." }), replyToMessageId: message.MessageId);
				break;
			case "makedecision":
			case "choose":
				var options = query?.Split(",").Where(p => !string.IsNullOrWhiteSpace(p)).ToList();
				if (options == null || !options.Any())
					options = new List<string> { "Syntax error. (Can't select from zero options)" };
				await botClient.SendTextMessageAsync(message.Chat.Id, RandomOption(options).Trim(), replyToMessageId: message.MessageId);
				break;
			case "spinbottle":
				var people = query?.Split(" ").Where(p => !string.IsNullOrWhiteSpace(p)).ToList();
				if (people == null || !people.Any()) {
					await botClient.SendTextMessageAsync(message.Chat.Id, "Syntax error. (Can't select from zero options)", replyToMessageId: message.MessageId);
					break;
				}

				await botClient.SendTextMessageAsync(message.Chat.Id, RandomOption(people).Trim().TrimEnd(',') + ", truth or dare?", replyToMessageId: message.MessageId);
				break;
			case "help":
			case "start":
				await botClient.SendTextMessageAsync(message.Chat.Id, $"""
				Heya, I am a bot that can help you make decisions! Here's a list of things I can do:

				/coinflip - flips a coin
				/shouldi - when you are unsure if you should do something
				/yesno - answers more generic yes/no questions
				/makedecision - helps you make a decision (chooses from a comma separated list of options; aliased to /choose)

				Feel free to add me to your group chats!
				Be aware that in those contexts, I can't read (and therefore not respond to) any messages unless they use the syntax `/<command>@{me.Username}` except when I'm the only bot in the chat, in which case `/<command>` is enough.

				In direct messages, commands also work without the / at the start.

				If your message doesn't start with a recognized command, I'll do my best to figure out what you are asking.

				This currently works with the following queries:
				- `thing1 or thing2 or thing3` gets translated into `/makedecision thing1,thing2,thing3`
				- `flip a coin` gets translated into `/coinflip`
				- `this is a question?` gets translated to `/yesno this is a question`

				If there is an error, please forward the stacktrace message to @zotan (my creator). You can also DM them for feature requests.

				Enjoy!

				I'm powered by [~zotan](https://zotan.pw)'s [Telegram.Bot.DecisionMaker](https://git.ztn.sh/zotan/Telegram.Bot.DecisionMaker) rev. [{version}](https://git.ztn.sh/zotan/Telegram.Bot.DecisionMaker/commit/{version.Replace("-dirty", "")})
				""", replyToMessageId: message.MessageId, parseMode: ParseMode.Markdown, disableWebPagePreview: true);
				break;
			default:
				await botClient.SendTextMessageAsync(message.Chat.Id, $"""
				Apologies, I can't figure out what you want me to do >w<

				Message received: `{message.Text}`
				Parsed command: `{command}`
				Parsed query: `{query}`

				Try /help for examples on how to help me understand your query!
				""", replyToMessageId: message.MessageId, parseMode: ParseMode.Markdown);
				break;
		}
	}
	catch (Exception e) {
		await botClient.SendTextMessageAsync(message.Chat.Id, $"""
			Error processing message.

			Message content: `{message.Text}`
			Parsed command: `{command}`
			Parsed query: `{query}`

			Exception: `{e.Message.Replace("`", "'")}`
			Stacktrace: `{e.StackTrace?.Replace("`", "'")}`
			""", replyToMessageId: message.MessageId, parseMode: ParseMode.Markdown);
		throw;
	}
}

static string RandomOption(IReadOnlyList<string> options) {
	var random = new Random(Guid.NewGuid().GetHashCode());
	var index  = random.Next(options.Count);
	return options[index];
}