/**
 * collectd - src/email.c
 * Copyright (C) 2006-2008  Sebastian Harl
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Authors:
 *   Sebastian Harl <sh at tokkee.org>
 **/

/*
 * This plugin communicates with a spam filter, a virus scanner or similar
 * software using a UNIX socket and a very simple protocol:
 *
 * e-mail type (e.g. ham, spam, virus, ...) and size
 * e:<type>:<bytes>
 *
 * spam score
 * s:<value>
 *
 * successful spam checks
 * c:<type1>[,<type2>,...]
 */

#include "collectd.h"

#include "plugin.h"
#include "utils/common/common.h"

#include <stddef.h>

#include <sys/select.h>
#include <sys/un.h>

/* some systems (e.g. Darwin) seem to not define UNIX_PATH_MAX at all */
#ifndef UNIX_PATH_MAX
#define UNIX_PATH_MAX sizeof(((struct sockaddr_un *)0)->sun_path)
#endif /* UNIX_PATH_MAX */

#if HAVE_GRP_H
#include <grp.h>
#endif /* HAVE_GRP_H */

#define SOCK_PATH LOCALSTATEDIR "/run/" PACKAGE_NAME "-email"
#define MAX_CONNS 5
#define MAX_CONNS_LIMIT 16384

#define log_debug(...) DEBUG("email: "__VA_ARGS__)
#define log_err(...) ERROR("email: "__VA_ARGS__)
#define log_warn(...) WARNING("email: "__VA_ARGS__)

/*
 * Private data structures
 */
/* linked list of email and check types */
typedef struct type {
  char *name;
  int value;
  struct type *next;
} type_t;

typedef struct {
  type_t *head;
  type_t *tail;
} type_list_t;

/* collector thread control information */
typedef struct collector {
  pthread_t thread;

  /* socket descriptor of the current/last connection */
  FILE *socket;
} collector_t;

/* linked list of pending connections */
typedef struct conn {
  /* socket to read data from */
  FILE *socket;

  /* linked list of connections */
  struct conn *next;
} conn_t;

typedef struct {
  conn_t *head;
  conn_t *tail;
} conn_list_t;

/*
 * Private variables
 */
/* valid configuration file keys */
static const char *config_keys[] = {"SocketFile", "SocketGroup", "SocketPerms",
                                    "MaxConns"};
static int config_keys_num = STATIC_ARRAY_SIZE(config_keys);

/* socket configuration */
static char *sock_file;
static char *sock_group;
static int sock_perms = S_IRWXU | S_IRWXG;
static int max_conns = MAX_CONNS;

/* state of the plugin */
static int disabled;

/* thread managing "client" connections */
static pthread_t connector = (pthread_t)0;
static int connector_socket = -1;

/* tell the collector threads that a new connection is available */
static pthread_cond_t conn_available = PTHREAD_COND_INITIALIZER;

/* connections that are waiting to be processed */
static pthread_mutex_t conns_mutex = PTHREAD_MUTEX_INITIALIZER;
static conn_list_t conns;

/* tell the connector thread that a collector is available */
static pthread_cond_t collector_available = PTHREAD_COND_INITIALIZER;

/* collector threads */
static collector_t **collectors;

static pthread_mutex_t available_mutex = PTHREAD_MUTEX_INITIALIZER;
static int available_collectors;

static pthread_mutex_t count_mutex = PTHREAD_MUTEX_INITIALIZER;
static type_list_t list_count;
static type_list_t list_count_copy;

static pthread_mutex_t size_mutex = PTHREAD_MUTEX_INITIALIZER;
static type_list_t list_size;
static type_list_t list_size_copy;

static pthread_mutex_t score_mutex = PTHREAD_MUTEX_INITIALIZER;
static double score;
static int score_count;

static pthread_mutex_t check_mutex = PTHREAD_MUTEX_INITIALIZER;
static type_list_t list_check;
static type_list_t list_check_copy;

/*
 * Private functions
 */
static int email_config(const char *key, const char *value) {
  if (strcasecmp(key, "SocketFile") == 0) {
    if (sock_file != NULL)
      free(sock_file);
    sock_file = sstrdup(value);
  } else if (strcasecmp(key, "SocketGroup") == 0) {
    if (sock_group != NULL)
      free(sock_group);
    sock_group = sstrdup(value);
  } else if (strcasecmp(key, "SocketPerms") == 0) {
    /* the user is responsible for providing reasonable values */
    sock_perms = (int)strtol(value, NULL, 8);
  } else if (strcasecmp(key, "MaxConns") == 0) {
    long int tmp = strtol(value, NULL, 0);

    if (tmp < 1) {
      fprintf(stderr,
              "email plugin: `MaxConns' was set to invalid "
              "value %li, will use default %i.\n",
              tmp, MAX_CONNS);
      ERROR("email plugin: `MaxConns' was set to invalid "
            "value %li, will use default %i.\n",
            tmp, MAX_CONNS);
      max_conns = MAX_CONNS;
    } else if (tmp > MAX_CONNS_LIMIT) {
      fprintf(stderr,
              "email plugin: `MaxConns' was set to invalid "
              "value %li, will use hardcoded limit %i.\n",
              tmp, MAX_CONNS_LIMIT);
      ERROR("email plugin: `MaxConns' was set to invalid "
            "value %li, will use hardcoded limit %i.\n",
            tmp, MAX_CONNS_LIMIT);
      max_conns = MAX_CONNS_LIMIT;
    } else {
      max_conns = (int)tmp;
    }
  } else {
    return -1;
  }
  return 0;
} /* static int email_config (char *, char *) */

/* Increment the value of the given name in the given list by incr. */
static void type_list_incr(type_list_t *list, char *name, int incr) {
  if (list->head == NULL) {
    list->head = smalloc(sizeof(*list->head));

    list->head->name = sstrdup(name);
    list->head->value = incr;
    list->head->next = NULL;

    list->tail = list->head;
  } else {
    type_t *ptr;

    for (ptr = list->head; NULL != ptr; ptr = ptr->next) {
      if (strcmp(name, ptr->name) == 0)
        break;
    }

    if (ptr == NULL) {
      list->tail->next = smalloc(sizeof(*list->tail->next));
      list->tail = list->tail->next;

      list->tail->name = sstrdup(name);
      list->tail->value = incr;
      list->tail->next = NULL;
    } else {
      ptr->value += incr;
    }
  }
  return;
} /* static void type_list_incr (type_list_t *, char *) */

static void *collect(void *arg) {
  collector_t *this = (collector_t *)arg;

  while (1) {
    conn_t *connection;

    pthread_mutex_lock(&conns_mutex);

    while (conns.head == NULL) {
      pthread_cond_wait(&conn_available, &conns_mutex);
    }

    connection = conns.head;
    conns.head = conns.head->next;

    if (conns.head == NULL) {
      conns.tail = NULL;
    }

    pthread_mutex_unlock(&conns_mutex);

    /* make the socket available to the global
     * thread and connection management */
    this->socket = connection->socket;

    log_debug("collect: handling connection on fd #%i", fileno(this->socket));

    while (42) {
      /* 256 bytes ought to be enough for anybody ;-) */
      char line[256 + 1]; /* line + '\0' */

      errno = 0;
      if (fgets(line, sizeof(line), this->socket) == NULL) {
        if (errno != 0) {
          log_err("collect: reading from socket (fd #%i) "
                  "failed: %s",
                  fileno(this->socket), STRERRNO);
        }
        break;
      }

      size_t len = strlen(line);
      if ((line[len - 1] != '\n') && (line[len - 1] != '\r')) {
        log_warn("collect: line too long (> %" PRIsz " characters): "
                 "'%s' (truncated)",
                 sizeof(line) - 1, line);

        while (fgets(line, sizeof(line), this->socket) != NULL)
          if ((line[len - 1] == '\n') || (line[len - 1] == '\r'))
            break;
        continue;
      }
      if (len < 3) { /* [a-z] ':' '\n' */
        continue;
      }

      line[len - 1] = '\0';

      log_debug("collect: line = '%s'", line);

      if (line[1] != ':') {
        log_err("collect: syntax error in line '%s'", line);
        continue;
      }

      if (line[0] == 'e') { /* e:<type>:<bytes> */
        char *type = line + 2;
        char *bytes_str = strchr(type, ':');
        if (bytes_str == NULL) {
          log_err("collect: syntax error in line '%s'", line);
          continue;
        }

        *bytes_str = 0;
        bytes_str++;

        pthread_mutex_lock(&count_mutex);
        type_list_incr(&list_count, type, /* increment = */ 1);
        pthread_mutex_unlock(&count_mutex);

        int bytes = atoi(bytes_str);
        if (bytes > 0) {
          pthread_mutex_lock(&size_mutex);
          type_list_incr(&list_size, type, /* increment = */ bytes);
          pthread_mutex_unlock(&size_mutex);
        }
      } else if (line[0] == 's') { /* s:<value> */
        pthread_mutex_lock(&score_mutex);
        score = (score * (double)score_count + atof(line + 2)) /
                (double)(score_count + 1);
        ++score_count;
        pthread_mutex_unlock(&score_mutex);
      } else if (line[0] == 'c') { /* c:<type1>[,<type2>,...] */
        char *dummy = line + 2;
        char *endptr = NULL;
        char *type;

        pthread_mutex_lock(&check_mutex);
        while ((type = strtok_r(dummy, ",", &endptr)) != NULL) {
          dummy = NULL;
          type_list_incr(&list_check, type, /* increment = */ 1);
        }
        pthread_mutex_unlock(&check_mutex);
      } else {
        log_err("collect: unknown type '%c'", line[0]);
      }
    } /* while (42) */

    log_debug("Shutting down connection on fd #%i", fileno(this->socket));

    fclose(connection->socket);
    free(connection);

    this->socket = NULL;

    pthread_mutex_lock(&available_mutex);
    ++available_collectors;
    pthread_mutex_unlock(&available_mutex);

    pthread_cond_signal(&collector_available);
  } /* while (1) */

  pthread_exit((void *)0);
  return (void *)0;
} /* static void *collect (void *) */

static void *open_connection(void __attribute__((unused)) * arg) {
  const char *path = (NULL == sock_file) ? SOCK_PATH : sock_file;
  const char *group = (NULL == sock_group) ? COLLECTD_GRP_NAME : sock_group;

  /* create UNIX socket */
  errno = 0;
  if ((connector_socket = socket(PF_UNIX, SOCK_STREAM, 0)) == -1) {
    disabled = 1;
    log_err("socket() failed: %s", STRERRNO);
    pthread_exit((void *)1);
  }

  struct sockaddr_un addr = {
      .sun_family = AF_UNIX,
  };
  sstrncpy(addr.sun_path, path, (size_t)(UNIX_PATH_MAX - 1));

  errno = 0;
  if (bind(connector_socket, (struct sockaddr *)&addr,
           offsetof(struct sockaddr_un, sun_path) + strlen(addr.sun_path)) ==
      -1) {
    disabled = 1;
    close(connector_socket);
    connector_socket = -1;
    log_err("bind() failed: %s", STRERRNO);
    pthread_exit((void *)1);
  }

  errno = 0;
  if (listen(connector_socket, 5) == -1) {
    disabled = 1;
    close(connector_socket);
    connector_socket = -1;
    log_err("listen() failed: %s", STRERRNO);
    pthread_exit((void *)1);
  }

  {
    struct group sg;
    struct group *grp;
    int status;

    long int grbuf_size = sysconf(_SC_GETGR_R_SIZE_MAX);
    if (grbuf_size <= 0)
      grbuf_size = sysconf(_SC_PAGESIZE);
    if (grbuf_size <= 0)
      grbuf_size = 4096;
    char grbuf[grbuf_size];

    grp = NULL;
    status = getgrnam_r(group, &sg, grbuf, sizeof(grbuf), &grp);
    if (status != 0) {
      log_warn("getgrnam_r (%s) failed: %s", group, STRERROR(status));
    } else if (grp == NULL) {
      log_warn("No such group: `%s'", group);
    } else {
      status = chown(path, (uid_t)-1, grp->gr_gid);
      if (status != 0) {
        log_warn("chown (%s, -1, %i) failed: %s", path, (int)grp->gr_gid,
                 STRERRNO);
      }
    }
  }

  errno = 0;
  if (chmod(path, sock_perms) != 0) {
    log_warn("chmod() failed: %s", STRERRNO);
  }

  { /* initialize collector threads */
    conns.head = NULL;
    conns.tail = NULL;

    available_collectors = max_conns;

    collectors = smalloc(max_conns * sizeof(*collectors));

    for (int i = 0; i < max_conns; ++i) {
      collectors[i] = smalloc(sizeof(*collectors[i]));
      collectors[i]->socket = NULL;

      if (plugin_thread_create(&collectors[i]->thread, collect, collectors[i],
                               "email collector") == 0) {
        pthread_detach(collectors[i]->thread);
      } else {
        log_err("plugin_thread_create() failed: %s", STRERRNO);
        collectors[i]->thread = (pthread_t)0;
      }
    }
  }

  while (1) {
    int remote = 0;

    conn_t *connection;

    pthread_mutex_lock(&available_mutex);

    while (available_collectors == 0) {
      pthread_cond_wait(&collector_available, &available_mutex);
    }

    --available_collectors;

    pthread_mutex_unlock(&available_mutex);

    while (42) {
      errno = 0;

      remote = accept(connector_socket, NULL, NULL);
      if (remote == -1) {
        if (errno == EINTR)
          continue;

        disabled = 1;
        close(connector_socket);
        connector_socket = -1;
        log_err("accept() failed: %s", STRERRNO);
        pthread_exit((void *)1);
      }

      /* access() succeeded. */
      break;
    }

    connection = calloc(1, sizeof(*connection));
    if (connection == NULL) {
      close(remote);
      continue;
    }

    connection->socket = fdopen(remote, "r");
    connection->next = NULL;

    if (connection->socket == NULL) {
      close(remote);
      sfree(connection);
      continue;
    }

    pthread_mutex_lock(&conns_mutex);

    if (conns.head == NULL) {
      conns.head = connection;
      conns.tail = connection;
    } else {
      conns.tail->next = connection;
      conns.tail = conns.tail->next;
    }

    pthread_mutex_unlock(&conns_mutex);

    pthread_cond_signal(&conn_available);
  }

  pthread_exit((void *)0);
  return (void *)0;
} /* static void *open_connection (void *) */

static int email_init(void) {
  if (plugin_thread_create(&connector, open_connection, NULL,
                           "email listener") != 0) {
    disabled = 1;
    log_err("plugin_thread_create() failed: %s", STRERRNO);
    return -1;
  }

  return 0;
} /* int email_init */

static void type_list_free(type_list_t *t) {
  type_t *this;

  this = t->head;
  while (this != NULL) {
    type_t *next = this->next;

    sfree(this->name);
    sfree(this);

    this = next;
  }

  t->head = NULL;
  t->tail = NULL;
}

static int email_shutdown(void) {
  if (connector != ((pthread_t)0)) {
    pthread_kill(connector, SIGTERM);
    connector = (pthread_t)0;
  }

  if (connector_socket >= 0) {
    close(connector_socket);
    connector_socket = -1;
  }

  /* don't allow any more connections to be processed */
  pthread_mutex_lock(&conns_mutex);

  available_collectors = 0;

  if (collectors != NULL) {
    for (int i = 0; i < max_conns; ++i) {
      if (collectors[i] == NULL)
        continue;

      if (collectors[i]->thread != ((pthread_t)0)) {
        pthread_kill(collectors[i]->thread, SIGTERM);
        collectors[i]->thread = (pthread_t)0;
      }

      if (collectors[i]->socket != NULL) {
        fclose(collectors[i]->socket);
        collectors[i]->socket = NULL;
      }

      sfree(collectors[i]);
    }
    sfree(collectors);
  } /* if (collectors != NULL) */

  pthread_mutex_unlock(&conns_mutex);

  type_list_free(&list_count);
  type_list_free(&list_count_copy);
  type_list_free(&list_size);
  type_list_free(&list_size_copy);
  type_list_free(&list_check);
  type_list_free(&list_check_copy);

  unlink((sock_file == NULL) ? SOCK_PATH : sock_file);

  sfree(sock_file);
  sfree(sock_group);
  return 0;
} /* static void email_shutdown (void) */

static void email_submit(const char *type, const char *type_instance,
                         gauge_t value) {
  value_list_t vl = VALUE_LIST_INIT;

  vl.values = &(value_t){.gauge = value};
  vl.values_len = 1;
  sstrncpy(vl.plugin, "email", sizeof(vl.plugin));
  sstrncpy(vl.type, type, sizeof(vl.type));
  sstrncpy(vl.type_instance, type_instance, sizeof(vl.type_instance));

  plugin_dispatch_values(&vl);
} /* void email_submit */

/* Copy list l1 to list l2. l2 may partly exist already, but it is assumed
 * that neither the order nor the name of any element of either list is
 * changed and no elements are deleted. The values of l1 are reset to zero
 * after they have been copied to l2. */
static void copy_type_list(type_list_t *l1, type_list_t *l2) {
  type_t *last = NULL;

  for (type_t *ptr1 = l1->head, *ptr2 = l2->head; ptr1 != NULL;
       ptr1 = ptr1->next, last = ptr2, ptr2 = ptr2->next) {
    if (ptr2 == NULL) {
      ptr2 = smalloc(sizeof(*ptr2));
      ptr2->name = NULL;
      ptr2->next = NULL;

      if (last == NULL) {
        l2->head = ptr2;
      } else {
        last->next = ptr2;
      }

      l2->tail = ptr2;
    }

    if (ptr2->name == NULL) {
      ptr2->name = sstrdup(ptr1->name);
    }

    ptr2->value = ptr1->value;
    ptr1->value = 0;
  }
  return;
}

static int email_read(void) {
  double score_old;
  int score_count_old;

  if (disabled)
    return -1;

  /* email count */
  pthread_mutex_lock(&count_mutex);

  copy_type_list(&list_count, &list_count_copy);

  pthread_mutex_unlock(&count_mutex);

  for (type_t *ptr = list_count_copy.head; ptr != NULL; ptr = ptr->next) {
    email_submit("email_count", ptr->name, ptr->value);
  }

  /* email size */
  pthread_mutex_lock(&size_mutex);

  copy_type_list(&list_size, &list_size_copy);

  pthread_mutex_unlock(&size_mutex);

  for (type_t *ptr = list_size_copy.head; ptr != NULL; ptr = ptr->next) {
    email_submit("email_size", ptr->name, ptr->value);
  }

  /* spam score */
  pthread_mutex_lock(&score_mutex);

  score_old = score;
  score_count_old = score_count;
  score = 0.0;
  score_count = 0;

  pthread_mutex_unlock(&score_mutex);

  if (score_count_old > 0)
    email_submit("spam_score", "", score_old);

  /* spam checks */
  pthread_mutex_lock(&check_mutex);

  copy_type_list(&list_check, &list_check_copy);

  pthread_mutex_unlock(&check_mutex);

  for (type_t *ptr = list_check_copy.head; ptr != NULL; ptr = ptr->next)
    email_submit("spam_check", ptr->name, ptr->value);

  return 0;
} /* int email_read */

void module_register(void) {
  plugin_register_config("email", email_config, config_keys, config_keys_num);
  plugin_register_init("email", email_init);
  plugin_register_read("email", email_read);
  plugin_register_shutdown("email", email_shutdown);
} /* void module_register */