/**
 * collectd - src/notify_email.c
 * Copyright (C) 2008  Oleg King
 * Copyright (C) 2010  Florian Forster
 *
 * This program 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 2 of the License, or (at your
 * option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 *
 * Authors:
 *   Oleg King <king2 at kaluga.ru>
 *   Florian Forster <octo at collectd.org>
 **/

#include "collectd.h"

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

#include <auth-client.h>
#include <libesmtp.h>

#define MAXSTRING 256

static const char *config_keys[] = {"SMTPServer",   "SMTPPort", "SMTPUser",
                                    "SMTPPassword", "From",     "Recipient",
                                    "Subject"};
static int config_keys_num = STATIC_ARRAY_SIZE(config_keys);

static char **recipients;
static int recipients_len;

static smtp_session_t session;
static pthread_mutex_t session_lock = PTHREAD_MUTEX_INITIALIZER;
static smtp_message_t message;
static auth_context_t authctx;

static int smtp_port = 25;
static char *smtp_host;
static char *smtp_user;
static char *smtp_password;
static char *email_from;
static char *email_subject;

#define DEFAULT_SMTP_HOST "localhost"
#define DEFAULT_SMTP_FROM "root@localhost"
#define DEFAULT_SMTP_SUBJECT "Collectd notify: %s@%s"

/* Callback to get username and password */
static int authinteract(auth_client_request_t request, char **result,
                        int fields, void __attribute__((unused)) * arg) {
  for (int i = 0; i < fields; i++) {
    if (request[i].flags & AUTH_USER)
      result[i] = smtp_user;
    else if (request[i].flags & AUTH_PASS)
      result[i] = smtp_password;
    else
      return 0;
  }
  return 1;
} /* int authinteract */

/* Callback to print the recipient status */
static void print_recipient_status(smtp_recipient_t recipient,
                                   const char *mailbox,
                                   void __attribute__((unused)) * arg) {
  const smtp_status_t *status;

  status = smtp_recipient_status(recipient);
  if (status->text[strlen(status->text) - 2] == '\r')
    status->text[strlen(status->text) - 2] = 0;
  INFO("notify_email: notify sent to %s: %d %s", mailbox, status->code,
       status->text);
} /* void print_recipient_status */

/* Callback to monitor SMTP activity */
static void monitor_cb(const char *buf, int buflen, int writing,
                       void __attribute__((unused)) * arg) {
  char log_str[MAXSTRING];

  sstrncpy(log_str, buf, sizeof(log_str));
  if (buflen > 2)
    log_str[buflen - 2] = 0; /* replace \n with \0 */

  if (writing == SMTP_CB_HEADERS) {
    DEBUG("notify_email plugin: SMTP --- H: %s", log_str);
    return;
  }
  DEBUG(writing ? "notify_email plugin: SMTP >>> C: %s"
                : "notify_email plugin: SMTP <<< S: %s",
        log_str);
} /* void monitor_cb */

static int notify_email_init(void) {
  char server[MAXSTRING];

  ssnprintf(server, sizeof(server), "%s:%i",
            (smtp_host == NULL) ? DEFAULT_SMTP_HOST : smtp_host, smtp_port);

  pthread_mutex_lock(&session_lock);

  auth_client_init();

  session = smtp_create_session();
  if (session == NULL) {
    pthread_mutex_unlock(&session_lock);
    ERROR("notify_email plugin: cannot create SMTP session");
    return -1;
  }

  smtp_set_monitorcb(session, monitor_cb, NULL, 1);
  smtp_set_hostname(session, hostname_g);
  smtp_set_server(session, server);

  if (smtp_user && smtp_password) {
    authctx = auth_create_context();
    auth_set_mechanism_flags(authctx, AUTH_PLUGIN_PLAIN, 0);
    auth_set_interact_cb(authctx, authinteract, NULL);
  }

  if (!smtp_auth_set_context(session, authctx)) {
    pthread_mutex_unlock(&session_lock);
    ERROR("notify_email plugin: cannot set SMTP auth context");
    return -1;
  }

  pthread_mutex_unlock(&session_lock);
  return 0;
} /* int notify_email_init */

static int notify_email_shutdown(void) {
  pthread_mutex_lock(&session_lock);

  if (session != NULL)
    smtp_destroy_session(session);
  session = NULL;

  if (authctx != NULL)
    auth_destroy_context(authctx);
  authctx = NULL;

  auth_client_exit();

  pthread_mutex_unlock(&session_lock);
  return 0;
} /* int notify_email_shutdown */

static int notify_email_config(const char *key, const char *value) {
  if (strcasecmp(key, "Recipient") == 0) {
    char **tmp;

    tmp = realloc(recipients, (recipients_len + 1) * sizeof(char *));
    if (tmp == NULL) {
      ERROR("notify_email: realloc failed.");
      return -1;
    }

    recipients = tmp;
    recipients[recipients_len] = strdup(value);
    if (recipients[recipients_len] == NULL) {
      ERROR("notify_email: strdup failed.");
      return -1;
    }
    recipients_len++;
  } else if (0 == strcasecmp(key, "SMTPServer")) {
    sfree(smtp_host);
    smtp_host = strdup(value);
  } else if (0 == strcasecmp(key, "SMTPPort")) {
    int port_tmp = atoi(value);
    if (port_tmp < 1 || port_tmp > 65535) {
      WARNING("notify_email plugin: Invalid SMTP port: %i", port_tmp);
      return 1;
    }
    smtp_port = port_tmp;
  } else if (0 == strcasecmp(key, "SMTPUser")) {
    sfree(smtp_user);
    smtp_user = strdup(value);
  } else if (0 == strcasecmp(key, "SMTPPassword")) {
    sfree(smtp_password);
    smtp_password = strdup(value);
  } else if (0 == strcasecmp(key, "From")) {
    sfree(email_from);
    email_from = strdup(value);
  } else if (0 == strcasecmp(key, "Subject")) {
    sfree(email_subject);
    email_subject = strdup(value);
  } else {
    return -1;
  }
  return 0;
} /* int notify_email_config (const char *, const char *) */

static int notify_email_notification(const notification_t *n,
                                     user_data_t __attribute__((unused)) *
                                         user_data) {

  struct tm timestamp_tm;
  char timestamp_str[64];

  char severity[32];
  char subject[MAXSTRING];

  char buf[4096] = "";
  char *buf_ptr = buf;
  int buf_len = sizeof(buf);

  ssnprintf(severity, sizeof(severity), "%s",
            (n->severity == NOTIF_FAILURE)
                ? "FAILURE"
                : ((n->severity == NOTIF_WARNING)
                       ? "WARNING"
                       : ((n->severity == NOTIF_OKAY) ? "OKAY" : "UNKNOWN")));

  ssnprintf(subject, sizeof(subject),
            (email_subject == NULL) ? DEFAULT_SMTP_SUBJECT : email_subject,
            severity, n->host);

  localtime_r(&CDTIME_T_TO_TIME_T(n->time), &timestamp_tm);
  strftime(timestamp_str, sizeof(timestamp_str), "%Y-%m-%d %H:%M:%S",
           &timestamp_tm);
  timestamp_str[sizeof(timestamp_str) - 1] = '\0';

  /* Let's make RFC822 message text with \r\n EOLs */
  int status = ssnprintf(buf, buf_len,
                         "MIME-Version: 1.0\r\n"
                         "Content-Type: text/plain; charset=\"US-ASCII\"\r\n"
                         "Content-Transfer-Encoding: 8bit\r\n"
                         "Subject: %s\r\n"
                         "\r\n"
                         "%s - %s@%s\r\n"
                         "\r\n",
                         subject, timestamp_str, severity, n->host);

  if (status > 0) {
    buf_ptr += status;
    buf_len -= status;
  }

#define APPEND(format, value)                                                  \
  if ((buf_len > 0) && (strlen(value) > 0)) {                                  \
    status = ssnprintf(buf_ptr, buf_len, format "\r\n", value);                \
    if (status > 0) {                                                          \
      buf_ptr += status;                                                       \
      buf_len -= status;                                                       \
    }                                                                          \
  }

  APPEND("Host: %s", n->host);
  APPEND("Plugin: %s", n->plugin);
  APPEND("Plugin instance: %s", n->plugin_instance);
  APPEND("Type: %s", n->type);
  APPEND("Type instance: %s", n->type_instance);
  APPEND("\r\nMessage: %s", n->message);

  pthread_mutex_lock(&session_lock);

  if (session == NULL) {
    /* Initialization failed or we're in the process of shutting down. */
    pthread_mutex_unlock(&session_lock);
    return -1;
  }

  if (!(message = smtp_add_message(session))) {
    pthread_mutex_unlock(&session_lock);
    ERROR("notify_email plugin: cannot set SMTP message");
    return -1;
  }
  smtp_set_reverse_path(message, email_from);
  smtp_set_header(message, "To", NULL, NULL);
  smtp_set_message_str(message, buf);

  for (int i = 0; i < recipients_len; i++)
    smtp_add_recipient(message, recipients[i]);

  /* Initiate a connection to the SMTP server and transfer the message. */
  if (!smtp_start_session(session)) {
    ERROR("notify_email plugin: SMTP server problem: %s",
          smtp_strerror(smtp_errno(), buf, sizeof buf));
    pthread_mutex_unlock(&session_lock);
    return -1;
  } else {
#if COLLECT_DEBUG
    const smtp_status_t *status;
    /* Report on the success or otherwise of the mail transfer. */
    status = smtp_message_transfer_status(message);
    DEBUG("notify_email plugin: SMTP server report: %d %s", status->code,
          (status->text != NULL) ? status->text : "\n");
#endif
    smtp_enumerate_recipients(message, print_recipient_status, NULL);
  }

  pthread_mutex_unlock(&session_lock);
  return 0;
} /* int notify_email_notification */

void module_register(void) {
  plugin_register_init("notify_email", notify_email_init);
  plugin_register_shutdown("notify_email", notify_email_shutdown);
  plugin_register_config("notify_email", notify_email_config, config_keys,
                         config_keys_num);
  plugin_register_notification("notify_email", notify_email_notification,
                               /* user_data = */ NULL);
} /* void module_register (void) */