/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/
/* <DESC>
 * multi socket API usage with epoll and timerfd
 * </DESC>
 */
/* Example application source code using the multi socket interface to
 * download many files at once.
 *
 * This example features the same basic functionality as hiperfifo.c does,
 * but this uses epoll and timerfd instead of libevent.
 *
 * Written by Jeff Pohlmeyer, converted to use epoll by Josh Bialkowski

Requires a linux system with epoll

When running, the program creates the named pipe "hiper.fifo"

Whenever there is input into the fifo, the program reads the input as a list
of URL's and creates some new easy handles to fetch each URL via the
curl_multi "hiper" API.


Thus, you can try a single URL:
  % echo http://www.yahoo.com > hiper.fifo

Or a whole bunch of them:
  % cat my-url-list > hiper.fifo

The fifo buffer is handled almost instantly, so you can even add more URL's
while the previous requests are still being downloaded.

Note:
  For the sake of simplicity, URL length is limited to 1023 char's !

This is purely a demo app, all retrieved data is simply discarded by the write
callback.

*/

#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/timerfd.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

#include <curl/curl.h>

#define MSG_OUT stdout /* Send info to stdout, change to stderr if you want */


/* Global information, common to all connections */
typedef struct _GlobalInfo
{
  int epfd;    /* epoll filedescriptor */
  int tfd;     /* timer filedescriptor */
  int fifofd;  /* fifo filedescriptor */
  CURLM *multi;
  int still_running;
  FILE *input;
} GlobalInfo;


/* Information associated with a specific easy handle */
typedef struct _ConnInfo
{
  CURL *easy;
  char *url;
  GlobalInfo *global;
  char error[CURL_ERROR_SIZE];
} ConnInfo;


/* Information associated with a specific socket */
typedef struct _SockInfo
{
  curl_socket_t sockfd;
  CURL *easy;
  int action;
  long timeout;
  GlobalInfo *global;
} SockInfo;

#define mycase(code) \
  case code: s = __STRING(code)

/* Die if we get a bad CURLMcode somewhere */
static void mcode_or_die(const char *where, CURLMcode code)
{
  if(CURLM_OK != code) {
    const char *s;
    switch(code) {
      mycase(CURLM_BAD_HANDLE); break;
      mycase(CURLM_BAD_EASY_HANDLE); break;
      mycase(CURLM_OUT_OF_MEMORY); break;
      mycase(CURLM_INTERNAL_ERROR); break;
      mycase(CURLM_UNKNOWN_OPTION); break;
      mycase(CURLM_LAST); break;
      default: s = "CURLM_unknown"; break;
      mycase(CURLM_BAD_SOCKET);
      fprintf(MSG_OUT, "ERROR: %s returns %s\n", where, s);
      /* ignore this error */
      return;
    }
    fprintf(MSG_OUT, "ERROR: %s returns %s\n", where, s);
    exit(code);
  }
}

static void timer_cb(GlobalInfo* g, int revents);

/* Update the timer after curl_multi library does it's thing. Curl will
 * inform us through this callback what it wants the new timeout to be,
 * after it does some work. */
static int multi_timer_cb(CURLM *multi, long timeout_ms, GlobalInfo *g)
{
  struct itimerspec its;

  fprintf(MSG_OUT, "multi_timer_cb: Setting timeout to %ld ms\n", timeout_ms);

  if(timeout_ms > 0) {
    its.it_interval.tv_sec = 0;
    its.it_interval.tv_nsec = 0;
    its.it_value.tv_sec = timeout_ms / 1000;
    its.it_value.tv_nsec = (timeout_ms % 1000) * 1000 * 1000;
  }
  else if(timeout_ms == 0) {
    /* libcurl wants us to timeout now, however setting both fields of
     * new_value.it_value to zero disarms the timer. The closest we can
     * do is to schedule the timer to fire in 1 ns. */
    its.it_interval.tv_sec = 0;
    its.it_interval.tv_nsec = 0;
    its.it_value.tv_sec = 0;
    its.it_value.tv_nsec = 1;
  }
  else {
    memset(&its, 0, sizeof(struct itimerspec));
  }

  timerfd_settime(g->tfd, /*flags=*/0, &its, NULL);
  return 0;
}


/* Check for completed transfers, and remove their easy handles */
static void check_multi_info(GlobalInfo *g)
{
  char *eff_url;
  CURLMsg *msg;
  int msgs_left;
  ConnInfo *conn;
  CURL *easy;
  CURLcode res;

  fprintf(MSG_OUT, "REMAINING: %d\n", g->still_running);
  while((msg = curl_multi_info_read(g->multi, &msgs_left))) {
    if(msg->msg == CURLMSG_DONE) {
      easy = msg->easy_handle;
      res = msg->data.result;
      curl_easy_getinfo(easy, CURLINFO_PRIVATE, &conn);
      curl_easy_getinfo(easy, CURLINFO_EFFECTIVE_URL, &eff_url);
      fprintf(MSG_OUT, "DONE: %s => (%d) %s\n", eff_url, res, conn->error);
      curl_multi_remove_handle(g->multi, easy);
      free(conn->url);
      curl_easy_cleanup(easy);
      free(conn);
    }
  }
}

/* Called by libevent when we get action on a multi socket filedescriptor*/
static void event_cb(GlobalInfo *g, int fd, int revents)
{
  CURLMcode rc;
  struct itimerspec its;

  int action = ((revents & EPOLLIN) ? CURL_CSELECT_IN : 0) |
               ((revents & EPOLLOUT) ? CURL_CSELECT_OUT : 0);

  rc = curl_multi_socket_action(g->multi, fd, action, &g->still_running);
  mcode_or_die("event_cb: curl_multi_socket_action", rc);

  check_multi_info(g);
  if(g->still_running <= 0) {
    fprintf(MSG_OUT, "last transfer done, kill timeout\n");
    memset(&its, 0, sizeof(struct itimerspec));
    timerfd_settime(g->tfd, 0, &its, NULL);
  }
}

/* Called by main loop when our timeout expires */
static void timer_cb(GlobalInfo* g, int revents)
{
  CURLMcode rc;
  uint64_t count = 0;
  ssize_t err = 0;

  err = read(g->tfd, &count, sizeof(uint64_t));
  if(err == -1) {
    /* Note that we may call the timer callback even if the timerfd is not
     * readable. It's possible that there are multiple events stored in the
     * epoll buffer (i.e. the timer may have fired multiple times). The
     * event count is cleared after the first call so future events in the
     * epoll buffer will fail to read from the timer. */
    if(errno == EAGAIN) {
      fprintf(MSG_OUT, "EAGAIN on tfd %d\n", g->tfd);
      return;
    }
  }
  if(err != sizeof(uint64_t)) {
    fprintf(stderr, "read(tfd) == %ld", err);
    perror("read(tfd)");
  }

  rc = curl_multi_socket_action(g->multi,
                                  CURL_SOCKET_TIMEOUT, 0, &g->still_running);
  mcode_or_die("timer_cb: curl_multi_socket_action", rc);
  check_multi_info(g);
}


/* Clean up the SockInfo structure */
static void remsock(SockInfo *f, GlobalInfo* g)
{
  if(f) {
    if(f->sockfd) {
      if(epoll_ctl(g->epfd, EPOLL_CTL_DEL, f->sockfd, NULL))
        fprintf(stderr, "EPOLL_CTL_DEL failed for fd: %d : %s\n",
                f->sockfd, strerror(errno));
    }
    free(f);
  }
}


/* Assign information to a SockInfo structure */
static void setsock(SockInfo *f, curl_socket_t s, CURL *e, int act,
                    GlobalInfo *g)
{
  struct epoll_event ev;
  int kind = ((act & CURL_POLL_IN) ? EPOLLIN : 0) |
             ((act & CURL_POLL_OUT) ? EPOLLOUT : 0);

  if(f->sockfd) {
    if(epoll_ctl(g->epfd, EPOLL_CTL_DEL, f->sockfd, NULL))
      fprintf(stderr, "EPOLL_CTL_DEL failed for fd: %d : %s\n",
              f->sockfd, strerror(errno));
  }

  f->sockfd = s;
  f->action = act;
  f->easy = e;

  ev.events = kind;
  ev.data.fd = s;
  if(epoll_ctl(g->epfd, EPOLL_CTL_ADD, s, &ev))
    fprintf(stderr, "EPOLL_CTL_ADD failed for fd: %d : %s\n",
            s, strerror(errno));
}


/* Initialize a new SockInfo structure */
static void addsock(curl_socket_t s, CURL *easy, int action, GlobalInfo *g)
{
  SockInfo *fdp = (SockInfo*)calloc(1, sizeof(SockInfo));

  fdp->global = g;
  setsock(fdp, s, easy, action, g);
  curl_multi_assign(g->multi, s, fdp);
}

/* CURLMOPT_SOCKETFUNCTION */
static int sock_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *sockp)
{
  GlobalInfo *g = (GlobalInfo*) cbp;
  SockInfo *fdp = (SockInfo*) sockp;
  const char *whatstr[]={ "none", "IN", "OUT", "INOUT", "REMOVE" };

  fprintf(MSG_OUT,
          "socket callback: s=%d e=%p what=%s ", s, e, whatstr[what]);
  if(what == CURL_POLL_REMOVE) {
    fprintf(MSG_OUT, "\n");
    remsock(fdp, g);
  }
  else {
    if(!fdp) {
      fprintf(MSG_OUT, "Adding data: %s\n", whatstr[what]);
      addsock(s, e, what, g);
    }
    else {
      fprintf(MSG_OUT,
              "Changing action from %s to %s\n",
              whatstr[fdp->action], whatstr[what]);
      setsock(fdp, s, e, what, g);
    }
  }
  return 0;
}


/* CURLOPT_WRITEFUNCTION */
static size_t write_cb(void *ptr, size_t size, size_t nmemb, void *data)
{
  (void)ptr;
  (void)data;
  return size * nmemb;
}


/* CURLOPT_PROGRESSFUNCTION */
static int prog_cb(void *p, double dltotal, double dlnow, double ult,
                   double uln)
{
  ConnInfo *conn = (ConnInfo *)p;
  (void)ult;
  (void)uln;

  fprintf(MSG_OUT, "Progress: %s (%g/%g)\n", conn->url, dlnow, dltotal);
  return 0;
}


/* Create a new easy handle, and add it to the global curl_multi */
static void new_conn(char *url, GlobalInfo *g)
{
  ConnInfo *conn;
  CURLMcode rc;

  conn = (ConnInfo*)calloc(1, sizeof(ConnInfo));
  conn->error[0]='\0';

  conn->easy = curl_easy_init();
  if(!conn->easy) {
    fprintf(MSG_OUT, "curl_easy_init() failed, exiting!\n");
    exit(2);
  }
  conn->global = g;
  conn->url = strdup(url);
  curl_easy_setopt(conn->easy, CURLOPT_URL, conn->url);
  curl_easy_setopt(conn->easy, CURLOPT_WRITEFUNCTION, write_cb);
  curl_easy_setopt(conn->easy, CURLOPT_WRITEDATA, conn);
  curl_easy_setopt(conn->easy, CURLOPT_VERBOSE, 1L);
  curl_easy_setopt(conn->easy, CURLOPT_ERRORBUFFER, conn->error);
  curl_easy_setopt(conn->easy, CURLOPT_PRIVATE, conn);
  curl_easy_setopt(conn->easy, CURLOPT_NOPROGRESS, 0L);
  curl_easy_setopt(conn->easy, CURLOPT_PROGRESSFUNCTION, prog_cb);
  curl_easy_setopt(conn->easy, CURLOPT_PROGRESSDATA, conn);
  curl_easy_setopt(conn->easy, CURLOPT_FOLLOWLOCATION, 1L);
  curl_easy_setopt(conn->easy, CURLOPT_LOW_SPEED_TIME, 3L);
  curl_easy_setopt(conn->easy, CURLOPT_LOW_SPEED_LIMIT, 10L);
  fprintf(MSG_OUT,
          "Adding easy %p to multi %p (%s)\n", conn->easy, g->multi, url);
  rc = curl_multi_add_handle(g->multi, conn->easy);
  mcode_or_die("new_conn: curl_multi_add_handle", rc);

  /* note that the add_handle() will set a time-out to trigger very soon so
     that the necessary socket_action() call will be called by this app */
}

/* This gets called whenever data is received from the fifo */
static void fifo_cb(GlobalInfo* g, int revents)
{
  char s[1024];
  long int rv = 0;
  int n = 0;

  do {
    s[0]='\0';
    rv = fscanf(g->input, "%1023s%n", s, &n);
    s[n]='\0';
    if(n && s[0]) {
      new_conn(s, g); /* if we read a URL, go get it! */
    }
    else
      break;
  } while(rv != EOF);
}

/* Create a named pipe and tell libevent to monitor it */
static const char *fifo = "hiper.fifo";
static int init_fifo(GlobalInfo *g)
{
  struct stat st;
  curl_socket_t sockfd;
  struct epoll_event epev;

  fprintf(MSG_OUT, "Creating named pipe \"%s\"\n", fifo);
  if(lstat (fifo, &st) == 0) {
    if((st.st_mode & S_IFMT) == S_IFREG) {
      errno = EEXIST;
      perror("lstat");
      exit(1);
    }
  }
  unlink(fifo);
  if(mkfifo (fifo, 0600) == -1) {
    perror("mkfifo");
    exit(1);
  }
  sockfd = open(fifo, O_RDWR | O_NONBLOCK, 0);
  if(sockfd == -1) {
    perror("open");
    exit(1);
  }

  g->fifofd = sockfd;
  g->input = fdopen(sockfd, "r");

  epev.events = EPOLLIN;
  epev.data.fd = sockfd;
  epoll_ctl(g->epfd, EPOLL_CTL_ADD, sockfd, &epev);

  fprintf(MSG_OUT, "Now, pipe some URL's into > %s\n", fifo);
  return 0;
}

static void clean_fifo(GlobalInfo *g)
{
    epoll_ctl(g->epfd, EPOLL_CTL_DEL, g->fifofd, NULL);
    fclose(g->input);
    unlink(fifo);
}


int g_should_exit_ = 0;

void sigint_handler(int signo)
{
  g_should_exit_ = 1;
}

int main(int argc, char **argv)
{
  GlobalInfo g;
  struct itimerspec its;
  struct epoll_event ev;
  struct epoll_event events[10];
  (void)argc;
  (void)argv;

  g_should_exit_ = 0;
  signal(SIGINT, sigint_handler);

  memset(&g, 0, sizeof(GlobalInfo));
  g.epfd = epoll_create1(EPOLL_CLOEXEC);
  if(g.epfd == -1) {
    perror("epoll_create1 failed");
    exit(1);
  }

  g.tfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK | TFD_CLOEXEC);
  if(g.tfd == -1) {
    perror("timerfd_create failed");
    exit(1);
  }

  memset(&its, 0, sizeof(struct itimerspec));
  its.it_interval.tv_sec = 0;
  its.it_value.tv_sec = 1;
  timerfd_settime(g.tfd, 0, &its, NULL);

  ev.events = EPOLLIN;
  ev.data.fd = g.tfd;
  epoll_ctl(g.epfd, EPOLL_CTL_ADD, g.tfd, &ev);

  init_fifo(&g);
  g.multi = curl_multi_init();

  /* setup the generic multi interface options we want */
  curl_multi_setopt(g.multi, CURLMOPT_SOCKETFUNCTION, sock_cb);
  curl_multi_setopt(g.multi, CURLMOPT_SOCKETDATA, &g);
  curl_multi_setopt(g.multi, CURLMOPT_TIMERFUNCTION, multi_timer_cb);
  curl_multi_setopt(g.multi, CURLMOPT_TIMERDATA, &g);

  /* we do not call any curl_multi_socket*() function yet as we have no handles
     added! */

  fprintf(MSG_OUT, "Entering wait loop\n");
  fflush(MSG_OUT);
  while(!g_should_exit_) {
    int idx;
    int err = epoll_wait(g.epfd, events,
                         sizeof(events)/sizeof(struct epoll_event), 10000);
    if(err == -1) {
      if(errno == EINTR) {
        fprintf(MSG_OUT, "note: wait interrupted\n");
        continue;
      }
      else {
        perror("epoll_wait");
        exit(1);
      }
    }

    for(idx = 0; idx < err; ++idx) {
      if(events[idx].data.fd == g.fifofd) {
        fifo_cb(&g, events[idx].events);
      }
      else if(events[idx].data.fd == g.tfd) {
        timer_cb(&g, events[idx].events);
      }
      else {
        event_cb(&g, events[idx].data.fd, events[idx].events);
      }
    }
  }

  fprintf(MSG_OUT, "Exiting normally.\n");
  fflush(MSG_OUT);

  curl_multi_cleanup(g.multi);
  clean_fifo(&g);
  return 0;
}