#define BOOST_ASIO_HAS_CO_AWAIT
#include <iostream>
#include <string>
#include <string_view>
#include <vector>
#include <algorithm>
#include <exception>
#include <stdexcept>
#include <memory>
#include <boost/asio.hpp>

using namespace boost;



std::string_view streambufAsString(asio::streambuf& buffer) {
    return std::string_view{reinterpret_cast<const char*>(buffer.data().data()), buffer.data().size()};
}

bool isPrintable(std::string_view str) {
    for (const auto c : str) {
        if (!isprint(c)) {
            return false;
        }
    }
    return true;
}


enum class Event {
    join, leave, message
};


class User {
    std::vector<std::shared_ptr<User>>& users;
    asio::ip::tcp::socket socket;
    std::string nickname;
    bool good = true;

public:
    User(asio::io_context& ioc, std::vector<std::shared_ptr<User>>& users) : socket(ioc), users(users) {}

    auto& getSocket() {
        return socket;
    }
    const auto& getNickname() const {
        return nickname;
    }
    bool isGood() const {
        return good;
    }
    bool isLoggedOn() const {
        return good && !nickname.empty();
    }
    bool wasLoggedOn() {
        return !nickname.empty();
    }
    void markAsBad() {
        good = false;
    }

    asio::awaitable<void> sendString(std::string_view str) {
        co_await asio::async_write(socket, asio::buffer(str), asio::use_awaitable);
    }
    asio::awaitable<std::string> recvLine() {
        asio::streambuf buffer;
        co_await asio::async_read_until(socket, buffer, '\n', asio::use_awaitable);
        auto fres = std::string(streambufAsString(buffer));
        fres.pop_back();
        co_return fres;
    }

    asio::awaitable<void> connect() {
        try {
            // Ask for nickname
            co_await sendString("Welcome to pyChat! Please type your nickname: ");
            while (true) {
                // Get nickname as string
                auto proposedNickname = co_await recvLine();
                // Check that nickname has a healthy length
                if (proposedNickname.empty() || proposedNickname.size() > 30) {
                    co_await sendString("Your nickname has a bad length. Please choose a different one: ");
                    continue;
                }
                // Check that nickname is printable
                if (!isPrintable(proposedNickname)) {
                    co_await sendString("Your nickname is invalid. Please choose a different one: ");
                    continue;
                }
                // Check that nickname is not already taken
                if (std::find_if(users.begin(), users.end(), [&, this] (const auto& o) {return o->getNickname() == proposedNickname;}) != users.end()) {
                    co_await sendString("This nickname has already been taken. Please choose a different one: ");
                    continue;
                }
                // Use this nickname
                nickname = std::move(proposedNickname);
                break;
            }
            std::cout << "User has connected as " << nickname << std::endl;
            // Broadcast join
            co_await broadcastEvent(Event::join);
            // Wait loop for messages
            while (true) {
                auto message = co_await recvLine();
                // Check kind of message
                if (message.starts_with('/')) { // Command
                    if (message == "/quit") {
                        markAsBad();
                        throw std::runtime_error("User initiated disconnect");
                    } else {
                        co_await sendString("Invalid command: "+message+'\n');
                    }
                } else { // Message
                    // Make sure message is printable
                    if (!isPrintable(message)) {
                        co_await sendString("Message could not be sent because it contains non-printable characters.\n");
                        continue;
                    }
                    // Broadcast message
                    co_await broadcastEvent(Event::message, message);
                }
            }
        } catch (std::exception& e) {
            std::cout << "User " << (nickname.empty() ? "<unknown>" : nickname) << " has disconnected: " << e.what() << std::endl;
            markAsBad();
        }
        // Broadcast user disconnect
        if (wasLoggedOn()) {
            co_await broadcastEvent(Event::leave);
        }
        // Delete user from list
        auto it = std::find_if(users.begin(), users.end(), [this] (const auto& o) {
            return o.get() == this;
        });
        users.erase(it);
    }

    asio::awaitable<void> onEvent(User& sender, Event event, std::string_view param = "") {
        switch (event) {
        case Event::join: co_await sendString("* "+sender.nickname+" has joined.\n"); break;
        case Event::leave: co_await sendString("* "+sender.nickname+" has left.\n"); break;
        case Event::message: co_await sendString(" <"+sender.nickname+"> "+std::string(param)+'\n'); break;
        }
    }

    asio::awaitable<void> broadcastEvent(Event event, std::string_view param = "") {
        for (auto& user : users) {
            if (user->isLoggedOn()) {
                co_await user->onEvent(*this, event, param);
            }
        }
    }
};


class Server {
    asio::io_context& ioc;
    std::vector<std::shared_ptr<User>> users;

public:
    Server(asio::io_context& ioc) : ioc(ioc) {}

    asio::awaitable<void> listen(int port) {
        try {
            // Create acceptor
            asio::ip::tcp::acceptor acceptor(ioc, asio::ip::tcp::endpoint(asio::ip::tcp::v4(), port));
            // Handle all incoming connections
            while (true) {
                auto user = std::make_shared<User>(ioc, users);
                co_await acceptor.async_accept(user->getSocket(), asio::use_awaitable);
                asio::co_spawn(ioc, user->connect(), asio::detached);
                users.push_back(std::move(user));
            }
        } catch (std::exception& e) {
            std::cerr << "Failed to stay alive: " << e.what() << std::endl;
        }
    }
};


int main() {
    try {
        asio::io_context ioc;
        Server server(ioc);
        int port = 22080;
        asio::co_spawn(ioc, server.listen(port), asio::detached);
        std::cout << "Server has initialized and will now be listening on port " << port << '.' << std::endl;
        ioc.run();
    } catch (std::exception& e) {
        std::cerr << "Failed to launch: " << e.what() << std::endl;
    }
}