extern "C" {
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <linux/if.h>
#include <linux/if_tun.h>

#include <sys/socket.h>
#include <netinet/in.h>

#include <arpa/inet.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
}

#include <cstring>
#include <expected>
#include <string>
#include <vector>
#include <span>
#include <iostream>
#include <thread>
#include <chrono>

#include <interface.hpp>

std::expected<void, std::string> Interface::Create(const std::string name) {
        if ((tunfd = open("/dev/net/tun", O_RDWR | O_CLOEXEC)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Create interface error: " + error);
        }
        struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
        strncpy(ifr.ifr_name, name.c_str(), IFNAMSIZ - 1);
        if (ioctl(tunfd, TUNSETIFF, (void*)(&ifr)) < 0) {
                close(tunfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Create interface error: " + error);
        }
        ifname = ifr.ifr_name;
#if 0
        if (ioctl(tunfd, TUNSETPERSIST, 0) < 0) {
                close(tunfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Create interface error: " + error);
        }
#endif

        //struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        int sockfd = 0;
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                close(tunfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Get MTU error: " + error);
        }
        strncpy(ifr.ifr_name, ifname.c_str(), IFNAMSIZ - 1);
        if (ioctl(sockfd, SIOCGIFMTU, &ifr) < 0) {
                close(tunfd);
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Get MTU error: " + error);
        }
        close(sockfd);
        mtu = ifr.ifr_mtu;
        return {};
}

std::expected<void, std::string> Interface::SetMTU(int ifmtu) {
        int sockfd = 0;
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set MTU error: " + error);
        }
        struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        strncpy(ifr.ifr_name, ifname.c_str(), IFNAMSIZ - 1);
        ifr.ifr_mtu = ifmtu;
        if (ioctl(sockfd, SIOCSIFMTU, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set MTU error: " + error);
        }
        close(sockfd);
        return {};
}

std::expected<int, std::string> Interface::GetMTU(void) {
        struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        int sockfd = 0;
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Get MTU error: " + error);
        }
        strncpy(ifr.ifr_name, ifname.c_str(), IFNAMSIZ - 1);
        if (ioctl(sockfd, SIOCGIFMTU, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Get MTU error: " + error);
        }
        close(sockfd);
        return ifr.ifr_mtu;
}

std::expected<std::string, std::string> Interface::GetIP4Address(void) {
        struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        int sockfd = 0;
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Get MTU error: " + error);
        }
        ifr.ifr_addr.sa_family = AF_INET;
        strncpy(ifr.ifr_name, ifname.c_str(), IFNAMSIZ - 1);

        if (ioctl(sockfd, SIOCGIFADDR, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Get MTU error: " + error);
        }
        close(sockfd);

        auto sinaddr = ((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr;
        std::string addr = inet_ntoa(sinaddr);
        return addr;
}

std::expected<void, std::string> Interface::SetIP4Address(std::string ipaddr) {
        struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        int sockfd = 0;
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set address error: " + error);
        }
        ifr.ifr_addr.sa_family = AF_INET;
        strncpy(ifr.ifr_name, ifname.c_str(), IFNAMSIZ - 1);

        struct sockaddr_in* addr = (struct sockaddr_in *)&ifr.ifr_addr;
        addr->sin_family = AF_INET;
        if (inet_pton(AF_INET, ipaddr.c_str(), &addr->sin_addr) <= 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set address error: " + error);
        }
        if (ioctl(sockfd, SIOCSIFADDR, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set address error: " + error);
        }
        close(sockfd);
        return {};
}

std::expected<void, std::string> Interface::SetIP4Netmask(int prefix) {
        if (prefix < 0 || prefix > 32) {
                return std::unexpected("Invalid prefix");
        }
        uint32_t mask = (prefix == 0) ? 0 : (~0U << (32 - prefix));

        //htonl(~((1U << (32 - prefix)) - 1));
        //struct in_addr addr;
        //addr.s_addr = mask;

        struct in_addr maskaddr;
        maskaddr.s_addr = htonl(mask);
        char buffer[INET_ADDRSTRLEN];
        if (inet_ntop(AF_INET, &maskaddr, buffer, sizeof(buffer)) == NULL) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set1 netmask error: " + error);
        }
        auto netmask = std::string(buffer);

        struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        int sockfd = 0;
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set2 netmask error: " + error);
        }
        ifr.ifr_addr.sa_family = AF_INET;
        strncpy(ifr.ifr_name, ifname.c_str(), IFNAMSIZ - 1);

        struct sockaddr_in* addr = (struct sockaddr_in *)&ifr.ifr_addr;
        addr->sin_family = AF_INET;
        if (inet_pton(AF_INET, netmask.c_str(), &addr->sin_addr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set3 netmask error: " + error);
        }
        if (ioctl(sockfd, SIOCSIFNETMASK, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set4 netmask error: " + error);
        }
        close(sockfd);
        return {};
}

std::expected<void, std::string> Interface::Up(void) {
        int sockfd = 0;
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Up interface error: " + error);
        }

        struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        strncpy(ifr.ifr_name, ifname.c_str(), IFNAMSIZ - 1);
        if (ioctl(sockfd, SIOCGIFFLAGS, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Up interface error: " + error);
        }
        ifr.ifr_flags |= (IFF_UP | IFF_RUNNING);
        if (ioctl(sockfd, SIOCSIFFLAGS, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Up interface error: " + error);
        }
        close(sockfd);
        return {};
}

std::expected<void, std::string> Interface::Down(void) {
        int sockfd = 0;
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Up interface error: " + error);
        }
        struct ifreq ifr;
        memset(&ifr, 0, sizeof(ifr));
        strncpy(ifr.ifr_name, ifname.c_str(), IFNAMSIZ - 1);
        if (ioctl(sockfd, SIOCGIFFLAGS, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Up interface error: " + error);
        }
        ifr.ifr_flags &= ~IFF_UP;
        if (ioctl(sockfd, SIOCSIFFLAGS, &ifr) < 0) {
                close(sockfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Up interface error: " + error);
        }
        close(sockfd);
        return {};
}

std::expected<std::string, std::string> Interface::Read() {
        char buffer[mtu];
        int rsize = 0;
        if ((rsize = read(tunfd, buffer, sizeof(buffer))) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Read interface error: " + error);
        }
        std::string rdata;
        rdata.append(buffer, rsize);
        return rdata;
}

std::string Interface::Name() {
        return ifname;
}

int Interface::MTU() {
        return mtu;
}

Interface::~Interface() {
        close(tunfd);
}


std::expected<void, std::string> Interface::UpN(void) {
        int netlinkfd = 0;
        if ((netlinkfd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Create interface error: " + error);
        }

        struct {
                struct nlmsghdr  header;
                struct ifinfomsg content;
        } request;

        memset(&request, 0, sizeof request);
        request.header.nlmsg_len = NLMSG_LENGTH(sizeof request.content);
        request.header.nlmsg_flags = NLM_F_REQUEST;
        request.header.nlmsg_type = RTM_NEWLINK;
        request.content.ifi_index = if_nametoindex(ifname.c_str());
        request.content.ifi_flags = IFF_UP;
        request.content.ifi_change = 1;

        if (send(netlinkfd, &request, request.header.nlmsg_len, 0) < 0) {
                close(netlinkfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Up interface error: " + error);
        }
        close(netlinkfd);
        return {};
}

std::expected<void, std::string> Interface::SetIP4AddrMask(const std::string address, const int prefix) {
        int netlinkfd = 0;
        if ((netlinkfd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE)) < 0) {
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Create interface error: " + error);
        }

        int rc = 0;
        struct sockaddr_nl sockaddr;
        memset(&sockaddr, 0, sizeof sockaddr);
        sockaddr.nl_family = AF_NETLINK;
        if ((rc = bind(netlinkfd, (struct sockaddr*) &sockaddr, sizeof sockaddr))< 0) {
                close(netlinkfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set interface address error: " + error);
        }
        struct {
                struct nlmsghdr  header;
                struct ifaddrmsg content;
                char             attributes_buf[64];
        } request;

        struct rtattr *request_attr;
        size_t attributes_buf_avail = sizeof request.attributes_buf;

        memset(&request, 0, sizeof request);
        request.header.nlmsg_len = NLMSG_LENGTH(sizeof request.content);
        request.header.nlmsg_flags = NLM_F_REQUEST | NLM_F_EXCL | NLM_F_CREATE;
        request.header.nlmsg_type = RTM_NEWADDR;
        request.content.ifa_index = if_nametoindex(ifname.c_str());
        request.content.ifa_family = AF_INET;
        request.content.ifa_prefixlen = prefix;

        /* request.attributes[IFA_LOCAL] = address */
        request_attr = IFA_RTA(&request.content);
        request_attr->rta_type = IFA_LOCAL;
        request_attr->rta_len = RTA_LENGTH(sizeof (struct in_addr));
        request.header.nlmsg_len += request_attr->rta_len;
        inet_pton(AF_INET, address.c_str(), RTA_DATA(request_attr));

        /* request.attributes[IFA_ADDRESS] = address */
        request_attr = RTA_NEXT(request_attr, attributes_buf_avail);
        request_attr->rta_type = IFA_ADDRESS;
        request_attr->rta_len = RTA_LENGTH(sizeof (struct in_addr));
        request.header.nlmsg_len += request_attr->rta_len;
        inet_pton(AF_INET, address.c_str(), RTA_DATA(request_attr));

        if (send(netlinkfd, &request, request.header.nlmsg_len, 0) < 0) {
                close(netlinkfd);
                int errnocopy = errno;
                std::string error = std::strerror(errnocopy);
                return std::unexpected("Set interface address error: " + error);
        }
        close(netlinkfd);
        return {};
}