/*
    Copyright© 2021 John Sennesael

    UsenetSearch is Free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    UsenetSearch is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with UsenetSearch.  If not, see <https://www.gnu.org/licenses/>.
*/

#include "usenetsearch/Dns.h"

#include "usenetsearch/Logger.h"

#include <sys/socket.h>

#include <cerrno>
#include <thread>

namespace usenetsearch {

std::vector<struct addrinfo> DnsResolve(
    const std::string& host,
    int port,
    const std::chrono::milliseconds& timeOut)
{
    std::vector<struct addrinfo> results;
    struct addrinfo* firstResult = nullptr;
    struct addrinfo hints{};
    struct addrinfo* result = nullptr;

    hints.ai_family = AF_UNSPEC; // ipv6 or ipv4
    hints.ai_flags = AI_V4MAPPED | AI_ALL;

    const auto start_time = std::chrono::system_clock::now();
    while (true)
    {
        // Handle timeout.
        const auto time = std::chrono::system_clock::now();
        const auto deltaT = 
            std::chrono::duration_cast<std::chrono::milliseconds>(
                time - start_time
            );
        if (deltaT > timeOut) break;
        // Try to resolve.
        const int getAddrInfoResult = getaddrinfo(
            host.c_str(),
            std::to_string(port).c_str(),
            &hints,
            &result
        );
        firstResult = result;
        if (getAddrInfoResult == EAI_AGAIN)
        {
            std::this_thread::sleep_for(std::chrono::milliseconds{500});
            continue;
        }
        if (getAddrInfoResult == 0)
        {
            break; // success
        }
        else
        {
            Logger::Get().Fatal<DnsResolveException>(
                LOGID("Dns"), 
                "Could not resolve host " + host + ": - Error ("
                + std::to_string(getAddrInfoResult) + ") - "
                + gai_strerror(getAddrInfoResult)
            );
        }
    }
    if (result == nullptr)
    {
        Logger::Get().Fatal<DnsResolveException>(
            LOGID("Dns"), 
            "Timed out trying to resolve host: " + host
        );
    }
    while (result != nullptr)
    {
        results.emplace_back(*result);
        result = result->ai_next;
    }
    if (firstResult != nullptr)
    {
        freeaddrinfo(firstResult);
    }
    return results;

}

} // namespace usenetsearch