#include "driver.hpp"
#include <map>
#include <vector>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cassert>
#include <poll.h>
#include <sys/time.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <sys/select.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netdb.h>
using SOCKET=int;
const int INVALID_SOCKET = -1;
using SocketVector = std::vector<SOCKET>;
using PollVector = std::vector<struct pollfd>;

struct termios orig_termios;

void set_nonblocking(int fd) {
    int flags = fcntl(fd, F_GETFL, 0);
    assert(flags != -1);
    int status = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
    assert(status != -1);
}

static void disableRawMode() {
    tcsetattr(0, TCSAFLUSH, &orig_termios);
}

static void enableRawMode() {
    int status = tcgetattr(0, &orig_termios);
    assert(status >= 0);
    atexit(disableRawMode);
    struct termios raw = orig_termios;
    raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
    raw.c_lflag &= ~(ECHO | ICANON);
    raw.c_oflag |= OPOST;
    raw.c_cc[VMIN] = 0;
    raw.c_cc[VTIME] = 0;
    status = tcsetattr(0, TCSAFLUSH, &raw);
    assert(status >= 0);
}

SOCKET open_connection(const std::string &target, std::string &err) {
    struct addrinfo *addrs = nullptr;
    struct addrinfo *goodaddr = nullptr;
    struct addrinfo hints;
    SOCKET sock = INVALID_SOCKET;
    std::string host, port;
    char errbuf[1024];

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_NUMERICSERV;
    
    err = "";
    util::split_host_port(target, host, port);
    int status = getaddrinfo(host.c_str(), port.c_str(), &hints, &addrs);
    if (status != 0) {
        err = gai_strerror(status);
        goto error;
    }
    if (addrs == nullptr) {
        err = "no such host found";
        goto error;
    }
    goodaddr = addrs;
    assert(goodaddr->ai_family == AF_INET);
    assert(goodaddr->ai_socktype == SOCK_STREAM);
    assert(goodaddr->ai_protocol == IPPROTO_TCP);
    sock = socket(goodaddr->ai_family, goodaddr->ai_socktype, goodaddr->ai_protocol);
    assert(sock > 0);
    set_nonblocking(sock);
    status = connect(sock, goodaddr->ai_addr, goodaddr->ai_addrlen);
    if ((status != 0) && (errno != EINPROGRESS)) {
        goto error_errno;
    }
    freeaddrinfo(addrs);
    return sock;

error_errno:
    err = strerror_r(errno, errbuf, 1024);
error:
    if (sock != INVALID_SOCKET) close(sock);
    if (addrs != nullptr) freeaddrinfo(addrs);
    return INVALID_SOCKET;
}

SOCKET listen_on_port(int port, std::string &err) {
    int status;
    err = "";
    SOCKET sock = socket(AF_INET, SOCK_STREAM, 0);
    assert(sock > 0);

    int enable = 1;
    status = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
    assert(status == 0);

    struct sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(port);

    status = bind(sock, (struct sockaddr *)&server, sizeof(server));
    assert(status == 0);
    status = listen(sock, 10);
    assert(status == 0);
    set_nonblocking(sock);
    return sock;
}

SocketVector accept_on_socket(SOCKET listen_socket) {
    SocketVector result;
    while (true) {
        SOCKET chsock = accept(listen_socket, nullptr, nullptr);
        if (chsock >= 0) {
            result.push_back(chsock);
        } else {
            if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
                // Normal completion - we're out of incoming sockets.
                return result;
            } else if (errno == ECONNABORTED) {
                // The remote disconnected before we had a chance to accept.
                // Just pretend it never happened.
            } else {
                // Unexpected error.
                assert(false);
            }
        }
    }
}

class MonoClock {
private:
    struct timespec base_;
public:
    MonoClock() {
        int status = clock_gettime(CLOCK_MONOTONIC, &base_);
        assert(status == 0);
    }
    double get() {
        struct timespec t;
        int status = clock_gettime(CLOCK_MONOTONIC, &t);
        assert(status == 0);
        double tv_sec = t.tv_sec - base_.tv_sec;
        double tv_nsec = t.tv_nsec - base_.tv_nsec;
        return tv_sec + (tv_nsec * 1.0E-9);
    }
};

static MonoClock monoclock;

namespace util {
    double profiling_clock() {
        return monoclock.get();
    }
}

class Driver {
public:
    enum ChanState {
        CHAN_INACTIVE,
        CHAN_CONNECTING,
        CHAN_OPEN,
    };
    struct ChanInfo {
        int chid;
        ChanState state;
        SOCKET socket;
    };

    DrivenEngine *driven_;
    std::vector<ChanInfo> chans_;
    bool any_inactive_;
    bool short_sleep_;
    std::map<int, SOCKET> listen_sockets_;
    std::unique_ptr<char[]> chbuf;

    void init(DrivenEngine *de) {
        driven_ = de;
        any_inactive_ = false;
        short_sleep_ = false;
        chbuf.reset(new char[65536]);
    }

    void handle_listen_ports() {
        std::set<int> listenports;
        driven_->drv_get_listen_ports(listenports);
        for (int port : listenports) {
            if (listen_sockets_.find(port) == listen_sockets_.end()) {
                std::string err;
                SOCKET sock = listen_on_port(port, err);
                if (sock != INVALID_SOCKET) {
                    listen_sockets_[port] = sock;
                }
            }
        }
    }

    void handle_lua_source() {
        if (driven_->drv_get_rescan_lua_source()) {
            driven_->drv_set_lua_source(util::read_lua_source("lua"));
            short_sleep_ = true;
        }
    }
    
    void close_channel(ChanInfo &chan, const std::string &err) {
        assert(chan.state != CHAN_INACTIVE);
        assert(close(chan.socket) == 0);
        driven_->drv_notify_close(chan.chid, err);
        chan.state = CHAN_INACTIVE;
        chan.socket = INVALID_SOCKET;
        chan.chid = -1;
        any_inactive_ = true;
        short_sleep_ = true;
    }

    void cleanup_channels() {
        if (any_inactive_) {
            for (int i = 0; i < int(chans_.size()); ) {
                if (chans_[i].state == CHAN_INACTIVE) {
                    chans_[i] = chans_.back();
                    chans_.pop_back();
                } else { 
                    i += 1;
                }
            }
            any_inactive_ = false;
        }
    }

    void handle_released_channels() {
        for (ChanInfo &chan : chans_) {
            if (driven_->drv_get_channel_released(chan.chid)) {
                close_channel(chan, "");
            }
        }
        cleanup_channels();
    }

    void handle_new_outgoing_sockets() {
        std::set<int> chans;
        driven_->drv_get_new_outgoing(chans);
        for (int chid : chans) {
            std::string err;
            SOCKET sock = open_connection(driven_->drv_get_target(chid), err);
            if (sock == INVALID_SOCKET) {
                driven_->drv_notify_close(chid, err);
                short_sleep_ = true;
            } else {
                ChanInfo newchan;
                newchan.chid = chid;
                newchan.state = CHAN_CONNECTING;
                newchan.socket = sock;
                chans_.push_back(newchan);
            }
        }
    }

    void handle_console_output() {
        while (true) {
            int nbytes; const char *bytes;
            driven_->drv_peek_outgoing(0, &nbytes, &bytes);
            if (nbytes == 0) break;
            int nwrote = write(1, bytes, nbytes);
            assert(nwrote > 0);
            driven_->drv_sent_outgoing(0, nwrote);
        }
    }

    void handle_console_input() {
        char buffer[256];
        while (true) {
            int nread = read(0, buffer, 256);
            if (nread == 0) break;
            assert(nread > 0);
            driven_->drv_recv_incoming(0, nread, buffer);
        }
    }

    void accept_connections(int port, SOCKET sock) {
        SocketVector sockets = accept_on_socket(sock);
        for (SOCKET sock : sockets) {
            int chid = driven_->drv_notify_accept(port);
            ChanInfo newchan;
            newchan.chid = chid;
            newchan.state = CHAN_OPEN;
            newchan.socket = sock;
            chans_.push_back(newchan);
            short_sleep_ = true;
        }
    }

    int calc_select_sets(fd_set &rfds, fd_set &wfds, fd_set &efds) const {
        FD_ZERO(&rfds);
        FD_ZERO(&wfds);
        FD_ZERO(&efds);
        int largest = -1;
        for (const auto &p : listen_sockets_) {
            FD_SET(p.second, &rfds);
            FD_SET(p.second, &efds);
            if (p.second > largest) largest = p.second;
        }
        for (const ChanInfo &chan : chans_) {
            SOCKET sock = chan.socket;
            if (sock == INVALID_SOCKET) continue;
            FD_SET(sock, &rfds);
            FD_SET(sock, &efds);
            if (!driven_->drv_outgoing_empty(chan.chid)) {
                FD_SET(sock, &wfds);
            }
            if (sock > largest) largest = sock;
        }
        return largest + 1;
    }

    void handle_socket_input_output(int mstimeout) {
        // Construct the pollfd vector.
        std::vector<struct pollfd> pollvec;
        pollvec.resize(listen_sockets_.size() + chans_.size() + 1);
        int index = 0;
        for (const auto &p : listen_sockets_) {
            struct pollfd &pfd = pollvec[index++];
            pfd.fd = p.second;
            pfd.events = POLLIN;
        }
        for (const ChanInfo &chan : chans_) {
            struct pollfd &pfd = pollvec[index++];
            pfd.fd = chan.socket;
            pfd.events = POLLIN;
            if (!driven_->drv_outgoing_empty(chan.chid)) {
                pfd.events |= POLLOUT;
            }
        }
        struct pollfd &stdiopoll = pollvec[index++];
        stdiopoll.fd = 0;
        stdiopoll.events = POLLIN;

        // Do the poll.
        int status = poll(&pollvec[0], pollvec.size(), mstimeout);
        assert(status >= 0);
        
        // Check listening sockets.
        index = 0;
        for (auto &p : listen_sockets_) {
            struct pollfd &pfd = pollvec[index++];
            if (pfd.revents & (POLLIN | POLLERR)) {
                accept_connections(p.first, p.second);
            }
        }

        // Transfer bytes wherever possible.
        for (ChanInfo &chan : chans_) {
            struct pollfd &pfd = pollvec[index++];
            SOCKET sock = chan.socket;
            if (sock == INVALID_SOCKET) continue;
            if (pfd.revents & POLLOUT) {
                int nbytes; const char *bytes;
                chan.state = CHAN_OPEN;
                driven_->drv_peek_outgoing(chan.chid, &nbytes, &bytes);
                if (nbytes > 0) {
                    int wbytes = send(sock, bytes, nbytes, 0);
                    if (wbytes < 0) {
                        close_channel(chan, "send failure");
                        continue;
                    } else {
                        driven_->drv_sent_outgoing(chan.chid, wbytes);
                    }
                }
            }
            if (pfd.revents & (POLLIN | POLLERR)) {
                // Someday, find a way to avoid this copy.
                int nrecv = recv(sock, chbuf.get(), 65536, 0);
                if (nrecv <= 0) {
                    close_channel(chan, "recv failure");
                    continue;
                } else {
                    driven_->drv_recv_incoming(chan.chid, nrecv, chbuf.get());
                    short_sleep_ = true;
                }
            }
        }

        // Delete any newly-inactive channels
        cleanup_channels();
    }

    void drive(DrivenEngine *de, int argc, char *argv[]) {
        enableRawMode();
        init(de);
        DrivenEngine::set(de);
        driven_->drv_set_lua_source(util::read_lua_source("lua"));
        driven_->drv_invoke_event_init(argc, argv);
        handle_listen_ports();
        while (!de->drv_get_stop_driver()) {
            short_sleep_ = false;
            handle_lua_source();
            handle_console_output();
            handle_console_input();
            handle_console_output();
            handle_released_channels();
            handle_new_outgoing_sockets();
            int mstimeout = short_sleep_ ? 0 : 100;
            handle_socket_input_output(mstimeout);
            driven_->drv_set_clock(monoclock.get());
            de->drv_invoke_event_update();
        }
        DrivenEngine::set(nullptr);
    }
};


void driver_drive(DrivenEngine *de, int argc, char *argv[]) {
    Driver driver;
    driver.drive(de, argc, argv);
}