/*
  Copyright 2016 Grégory Soutadé

  This file is part of iptogeo.

  iptogeo 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.

  iptogeo 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 iptogeo.  If not, see <http://www.gnu.org/licenses/>.
*/

#define _GNU_SOURCE 1 // for POLLRDHUP && syncfs
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <sys/time.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <time.h>
#include <syslog.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
#include <poll.h>

#ifdef USE_SECCOMP
#include <seccomp.h>
#endif

#include "ip_to_geo.h"
#include "protocol.h"

#define WAIT_TIME 100
#define MAX_WAIT_TIME 500

typedef struct {
    int socket;
    time_t timeout; // in µs
    int nb_remaining_requests;
} socket_ctx_t;

typedef struct thread_ctx_s{
    struct thread_ctx_s* prev;
    struct thread_ctx_s* next;
    pthread_t thread;
    socket_ctx_t* sockets;
    int nb_cur_sockets;
    int nb_available_sockets;
    int max_timeout;
    int max_sockets; // in ms
    int stop;
    int quiet;
    pthread_mutex_t mutex;
    struct pollfd * pollfds;
} thread_ctx_t;

static pthread_mutex_t s_fastmutex = PTHREAD_MUTEX_INITIALIZER;
static thread_ctx_t* s_last_thread = NULL;
static int s_server_socket = -1;
static int s_stop = 0;

void sigint(int sig)
{
    syslog(LOG_WARNING, "signal received, stopping threads");
    s_stop = 1;
    shutdown(s_server_socket, SHUT_RDWR);
}

static int check_request(request_t* req)
{
    if (req->magic != REQ_MAGIC)
        return REQ_ERR_BAD_MAGIC;

    if (req->version != REQ_VERSION)
        return REQ_ERR_BAD_VERSION;

    if (req->ip_type != REQ_IPV4 &&
        req->ip_type != REQ_IPV6)
        return REQ_ERR_BAD_IP_VERSION;

    if (req->ip_type != REQ_IPV4)
        return REQ_ERR_UNSUPPORTED_IP_VERSION;

    if (req->req != REQ_REQ)
        return REQ_ERR_BAD_REQ_FIELD;

    return REQ_ERR_NO_ERR;
}

static int handle_request(thread_ctx_t* thread_ctx, int socket)
{
    request_t req;
    const uint8_t* geo;
    int sent=0;
    int ret = read(socket, &req, sizeof(req));

    // Socket closed
    if (ret == 0)
    {
        if (thread_ctx->quiet < 0)
            syslog(LOG_DEBUG, "Socket %d closed", socket);
        return 1;
    }
    
    if (thread_ctx->quiet < 0)
        syslog(LOG_DEBUG, "New request");
    
    if (ret != sizeof(req))
    {
        if (thread_ctx->quiet < 0)
            syslog(LOG_DEBUG, "Invalid request size %d", ret);

        return -1;
    }

    ret = check_request(&req);
    req.req = REQ_RESP;

    if (ret)
    {
        req.err = ret;
        if (thread_ctx->quiet < 0)
            syslog(LOG_DEBUG, "Request error %d", ret);
    }
    else
    {
        if (thread_ctx->quiet < 0)
        {
            char dst[64];
            inet_ntop((req.ip_type == REQ_IPV4)?AF_INET:AF_INET6, req.ip, dst, sizeof(dst));
            syslog(LOG_DEBUG, "Request for %s from socket %d", dst, socket);
        }

        geo = ip_to_geo(req.ip, req.ip_type);
        if (!geo)
        {
            req.err = REQ_IP_NOT_FOUND;
            if (thread_ctx->quiet < 0)
                syslog(LOG_DEBUG, "Not found");
        }
        else
        {
            req.err = REQ_ERR_NO_ERR;
            geo = get_country_code(geo);
            if (thread_ctx->quiet < 0)
                syslog(LOG_DEBUG, "Res %s", geo);
            req.country_code[0] = geo[0];
            req.country_code[1] = geo[1];
            req.country_code[2] = 0;
            req.country_code[3] = 0;
        }
    }
    
    for (sent=0; sent < sizeof(req); sent += ret)
    {
        ret = write(socket, &((uint8_t*)&req)[sent], sizeof(req)-sent);
        if (ret < 0)
            return -1;
    }

    return 0;
}

static void delete_thread(thread_ctx_t* thread_ctx)
{
    int i;

    pthread_mutex_lock(&s_fastmutex);
    thread_ctx->nb_available_sockets = 0;

    if (thread_ctx->quiet < 0)
        syslog(LOG_DEBUG, "Delete thread %p", thread_ctx);
    
    for(i=0; i<thread_ctx->nb_cur_sockets; i++)
    {
        if (thread_ctx->sockets[i].timeout > 0)
        {
            close (thread_ctx->sockets[i].socket);
        }
    }

    free(thread_ctx->sockets);
    free(thread_ctx->pollfds);

    if (thread_ctx->next)
        thread_ctx->next->prev = thread_ctx->prev;
    if (thread_ctx->prev)
        thread_ctx->prev->next = thread_ctx->next;

    if (thread_ctx == s_last_thread)
        s_last_thread = thread_ctx->next;
    pthread_mutex_unlock(&s_fastmutex);

    free(thread_ctx);
}

static inline void close_socket(socket_ctx_t* socket)
{
    socket->timeout = -1;
    close(socket->socket);
}

#define POLL_ERR_MASK (POLLRDHUP|POLLERR|POLLHUP|POLLNVAL)

static void* thread_loop(void* param)
{
    thread_ctx_t* ctx = (thread_ctx_t*)param;
    int i, ret, nfds, nb_cur_sockets, nb_available_sockets, poll_idx;
    struct timeval time1, time2, time_res;
    int wait_time = WAIT_TIME;

    while (!ctx->stop)
    {
        nfds = 0;
        
        pthread_mutex_lock(&ctx->mutex);
        nb_cur_sockets = ctx->nb_cur_sockets;
        nb_available_sockets = ctx->nb_available_sockets;
        pthread_mutex_unlock(&ctx->mutex);

        for(i=0; i<nb_cur_sockets; i++)
        {
            if (ctx->sockets[i].timeout > 0)
            {
                ctx->pollfds[nfds].fd = ctx->sockets[i].socket;
                ctx->pollfds[nfds].events = POLLIN|POLL_ERR_MASK;
                nfds++;
            }
        }

        if (!nfds)
        {
            /*
              No more active socket for this thread
              nor available slots
            */
            if (!nb_available_sockets)
                break;

            if (wait_time < MAX_WAIT_TIME)
                wait_time += WAIT_TIME;

            usleep(wait_time);
            continue;
        }
        else
            wait_time = WAIT_TIME;

        gettimeofday(&time1, NULL);
        ret = poll(ctx->pollfds, nfds, ctx->max_timeout);
        gettimeofday(&time2, NULL);

        // Timeout, remove all current sockets
        if (ret == 0)
        {
            if (ctx->quiet < 0)
                syslog(LOG_DEBUG, "Timeout");

            for(i=0; i<nb_cur_sockets; i++)
            {
                if (ctx->sockets[i].timeout > 0)
                    close_socket(&ctx->sockets[i]);
            }
        }
        else if (ret < 0)
        {
            if (!s_stop && !ctx->stop)
                syslog(LOG_WARNING, "poll has errors (%m)\n");
            break;
        }
        else 
        {
            timersub(&time2, &time1, &time_res);
            poll_idx = -1;
            for(i=0; i<nb_cur_sockets; i++)
            {
                if (ctx->sockets[i].timeout < 0) continue;
                poll_idx++;
                if (ctx->pollfds[poll_idx].fd != ctx->sockets[i].socket)
                {
                    if (ctx->quiet < 0)
                        syslog(LOG_ERR, "Socket not found but present in poll fds");
                    continue;
                }

                // Error
                if (ctx->pollfds[poll_idx].revents & POLL_ERR_MASK)
                {
                    if (ctx->quiet < 0)
                        syslog(LOG_ERR, "Error (or closed) socket %d", ctx->sockets[i].socket);
                    close_socket(&ctx->sockets[i]);
                }
                // Someone is speaking
                else if (ctx->pollfds[poll_idx].revents & POLLIN)
                {
                    ctx->sockets[i].timeout = ctx->max_timeout*1000;
                    ret = handle_request(ctx, ctx->sockets[i].socket);
                    if (ret == 1)
                    {
                        if (ctx->quiet < 0)
                            syslog(LOG_DEBUG, "Client has closed socket %d",
                                ctx->sockets[i].socket);
                        close_socket(&ctx->sockets[i]);
                    }
                    // No more requests accepted
                    else if (!ctx->sockets[i].nb_remaining_requests--)
                    {
                        if (ctx->quiet < 0)
                            syslog(LOG_DEBUG, "Max requests reached for socket %d",
                                   ctx->sockets[i].socket);
                        syncfs(ctx->sockets[i].socket);
                        close_socket(&ctx->sockets[i]);
                    }
                }
                else
                {
                    ctx->sockets[i].timeout -= (time_res.tv_sec*1000000 + time_res.tv_usec);
                    if (ctx->sockets[i].timeout <= 0)
                        close_socket(&ctx->sockets[i]);
                }
            }
        }
    };

    delete_thread(ctx);

    pthread_exit(NULL);

    return NULL;
}

static inline thread_ctx_t* create_thread_ctx(struct gengetopt_args_info* params)
{
    thread_ctx_t* thread_ctx = malloc(sizeof(*thread_ctx));

    if (params->verbose_flag)
        syslog(LOG_DEBUG, "Create a new thread %p", thread_ctx);

    thread_ctx->sockets = malloc(sizeof(*thread_ctx->sockets)*params->sockets_per_thread_arg);
    thread_ctx->pollfds = malloc(sizeof(*thread_ctx->pollfds)*params->sockets_per_thread_arg);
    thread_ctx->nb_cur_sockets = 0;
    thread_ctx->nb_available_sockets = params->sockets_per_thread_arg;
    thread_ctx->max_timeout = params->sockets_timeout_arg*1000;
    thread_ctx->stop = 0;
    thread_ctx->quiet = params->quiet_flag;
    if (params->verbose_flag)
        thread_ctx->quiet = -1;
    thread_ctx->prev = NULL;
    pthread_mutex_init(&thread_ctx->mutex, NULL);

    thread_ctx->next = s_last_thread;
    if (s_last_thread)
        s_last_thread->prev = thread_ctx;
    s_last_thread = thread_ctx;

    return thread_ctx;
}

static void fill_new_socket(struct gengetopt_args_info* params, int socket)
{
    thread_ctx_t* thread_ctx;
    int launch_thread = 0;
    
    pthread_mutex_lock(&s_fastmutex);

    thread_ctx = s_last_thread;
    if (!thread_ctx || !thread_ctx->nb_available_sockets)
    {
        thread_ctx = create_thread_ctx(params);
        launch_thread = 1;
    }

    pthread_mutex_unlock(&s_fastmutex);

    thread_ctx->sockets[thread_ctx->nb_cur_sockets].socket = socket;
    thread_ctx->sockets[thread_ctx->nb_cur_sockets].timeout = thread_ctx->max_timeout*1000; // ms -> us
    thread_ctx->sockets[thread_ctx->nb_cur_sockets].nb_remaining_requests = params->client_max_requests_arg;

    pthread_mutex_lock(&thread_ctx->mutex);
    thread_ctx->nb_cur_sockets++;
    thread_ctx->nb_available_sockets--;
    pthread_mutex_unlock(&thread_ctx->mutex);

    if (launch_thread)
        pthread_create(&thread_ctx->thread, NULL, thread_loop, thread_ctx);
}

int daemonize(struct gengetopt_args_info* params)
{
    int ret;
    struct sockaddr_in sockaddr;
    socklen_t sockaddr_len;
    int new_socket;
    void* thread_ret;
    
    // Should have both ipv4 & ipv6
    s_server_socket = socket(AF_INET, SOCK_STREAM, 0); // Should have both TCP & UDP

    if (!s_server_socket)
    {
        if (!params->quiet_flag)
            fprintf(stderr, "Unable to create socket (%m)\n");
        return -1;
    }

    memset(&sockaddr, 0, sizeof(sockaddr));
    sockaddr.sin_family = AF_INET; // Should detect interface type (v4 or v6)
    sockaddr.sin_port = htons(params->port_arg);
    if (params->bind_ip_given)
    {
        ret = inet_aton(params->bind_ip_arg, &sockaddr.sin_addr);
        if (ret)
        {
            if (!params->quiet_flag)
                fprintf(stderr, "Error with bind address %s (%m)\n", params->bind_ip_arg);
            return -1;
        }
    }
    else
        sockaddr.sin_addr.s_addr = INADDR_ANY;
    
    ret = bind(s_server_socket, (struct sockaddr *)&sockaddr, sizeof(sockaddr));
    if (ret)
    {
        if (!params->quiet_flag)
            fprintf(stderr, "Unable to bind (%m)\n");
        return -2;
    }

    ret = listen(s_server_socket, 0);
    if (ret)
    {
        if (!params->quiet_flag)
            fprintf(stderr, "Unable to listen (%m)\n");
        return -3;
    }
    
    if (!params->no_background_flag)
    {
        ret = daemon(0, 0);
        if (ret)
        {
            if (!params->quiet_flag)
                fprintf(stderr, "Daemon error (%m)\n");
            return -4;
        }
    }

    openlog("ip_to_geod", 0, LOG_DAEMON);

    syslog(LOG_INFO, "ip_togeod started\n");
    
    signal(SIGINT,  sigint);
    signal(SIGUSR1, sigint);
    signal(SIGUSR2, sigint);

#ifdef USE_SECCOMP
    scmp_filter_ctx seccomp_ctx = seccomp_init(SCMP_ACT_KILL);
    
    if (seccomp_ctx == NULL)
    {
        syslog(LOG_ERR, "unable to initialize seccomp\n");
        return -5;
    }

    seccomp_rule_add(seccomp_ctx, SCMP_ACT_ALLOW, SCMP_SYS(read), 0);
    seccomp_rule_add(seccomp_ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 0);
    seccomp_rule_add(seccomp_ctx, SCMP_ACT_ALLOW, SCMP_SYS(close), 0);
    seccomp_rule_add(seccomp_ctx, SCMP_ACT_ALLOW, SCMP_SYS(accept), 0);
#endif

    while (!s_stop)
    {
        sockaddr_len = sizeof(sockaddr);
        new_socket = accept(s_server_socket, (struct sockaddr *) &sockaddr, &sockaddr_len);
        if (new_socket < 0)
        {
            if (!s_stop)
                syslog(LOG_ERR, "accept error (%m), exiting");
            break;
        }
        if (!params->quiet_flag)
            syslog(LOG_INFO, "new connection from %s, socket %d",
                   inet_ntoa(sockaddr.sin_addr), new_socket);
        fill_new_socket(params, new_socket);
    }

    close(s_server_socket);

    while (s_last_thread)
    {
        s_last_thread->stop = 1;
        pthread_join(s_last_thread->thread, &thread_ret);
    }

    closelog();

#ifdef USE_SECCOMP
    if (seccomp_ctx)
        seccomp_release(seccomp_ctx);
#endif

    return 0;
}