text: /**
   * Copyright (c) 2017 - 2018, Nordic Semiconductor ASA
   * 
   * All rights reserved.
   * 
   * Redistribution and use in source and binary forms, with or without modification,
   * are permitted provided that the following conditions are met:
   * 
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   * 
   * 2. Redistributions in binary form, except as embedded into a Nordic
   *    Semiconductor ASA integrated circuit in a product or a software update for
   *    such product, must reproduce the above copyright notice, this list of
   *    conditions and the following disclaimer in the documentation and/or other
   *    materials provided with the distribution.
   * 
   * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
   *    contributors may be used to endorse or promote products derived from this
   *    software without specific prior written permission.
   * 
   * 4. This software, with or without modification, must only be used with a
   *    Nordic Semiconductor ASA integrated circuit.
   * 
   * 5. Any software provided in binary form under this license must not be reverse
   *    engineered, decompiled, modified and/or disassembled.
   * 
   * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
   * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
   * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   * 
   */
  
  /**
   * @brief Immediate Alert Application main file.
   *
   * This file contains source code for a sample application using the
   * Immediate Alert service.
   *
   * This application accepts pairing requests from any peer device.
   */
  
  #include <stdint.h>
  #include <string.h>
  
  #include "nordic_common.h"
  #include "nrf.h"
  #include "app_error.h"
  #include "ble.h"
  #include "ble_hci.h"
  #include "ble_srv_common.h"
  #include "ble_ias.h"
  #include "nrf_sdh.h"
  #include "nrf_sdh_soc.h"
  #include "nrf_sdh_ble.h"
  #include "app_timer.h"
  #include "bsp_btn_ble.h"
  #include "peer_manager.h"
  #include "nrf_fstorage.h"
  #include "fds.h"
  #include "ble_conn_state.h"
  #include "nrf_ble_gatt.h"
  #include "ble_advdata.h"
  #include "nrf_pwr_mgmt.h"
  
  #include "nrf_log.h"
  #include "nrf_log_ctrl.h"
  #include "nrf_log_default_backends.h"
  
  
  #define APP_BLE_OBSERVER_PRIO           3                                       /**< Application's BLE observer priority. You shouldn't need to modify this value. */
  #define APP_SOC_OBSERVER_PRIO           1                                       /**< Applications' SoC observer priority. You shoulnd't need to modify this value. */
  #define APP_BLE_CONN_CFG_TAG            1                                       /**< A tag identifying the SoftDevice BLE configuration. */
  
  #define CENTRAL_SCANNING_LED            BSP_BOARD_LED_0                         /**< LED to indicate that scanning is active. */
  #define CENTRAL_CONNECTED_LED           BSP_BOARD_LED_1                         /**< LED to indicate that the device has established at least one connection. */
  
  #define MIN_CONN_INTERVAL               MSEC_TO_UNITS(500, UNIT_1_25_MS)        /**< Minimum acceptable connection interval (0.5 seconds).  */
  #define MAX_CONN_INTERVAL               MSEC_TO_UNITS(1000, UNIT_1_25_MS)       /**< Maximum acceptable connection interval (1 second). */
  #define SLAVE_LATENCY                   0                                       /**< Slave latency. */
  #define CONN_SUP_TIMEOUT                MSEC_TO_UNITS(4000, UNIT_10_MS)         /**< Connection supervisory timeout (4 seconds). */
  
  #define SCAN_INTERVAL                   0x00A0                                  /**< Determines scan interval in units of 0.625 millisecond. */
  #define SCAN_WINDOW                     0x0050                                  /**< Determines scan window in units of 0.625 millisecond. */
  #define SCAN_DURATION                   0x0000                                  /**< Timeout when scanning. 0x0000 disables the timeout. */
  
  #define SECURITY_REQUEST_DELAY          APP_TIMER_TICKS(4000)                   /**< Delay after connection until Security Request is sent, if necessary (ticks). */
  
  #define SEC_PARAM_BOND                  1                                       /**< Perform bonding. */
  #define SEC_PARAM_MITM                  0                                       /**< Man In The Middle protection not required. */
  #define SEC_PARAM_LESC                  0                                       /**< LE Secure Connections not enabled. */
  #define SEC_PARAM_KEYPRESS              0                                       /**< Keypress notifications not enabled. */
  #define SEC_PARAM_IO_CAPABILITIES       BLE_GAP_IO_CAPS_NONE                    /**< No I/O capabilities. */
  #define SEC_PARAM_OOB                   0                                       /**< Out Of Band data not available. */
  #define SEC_PARAM_MIN_KEY_SIZE          7                                       /**< Minimum encryption key size. */
  #define SEC_PARAM_MAX_KEY_SIZE          16                                      /**< Maximum encryption key size. */
  
  #define TARGET_UUID                     BLE_UUID_IMMEDIATE_ALERT_SERVICE        /**< Target device name that the application is looking for. */
  
  #define DEAD_BEEF                       0xDEADBEEF                              /**< Value used as error code on stack dump. Can be used to identify stack location on stack unwind. */
  
  
  APP_TIMER_DEF(m_sec_req_timer_id);                        /**< Security request timer. The timer allows for starting a pairing request if one does not arrive from the Central. */
  NRF_BLE_GATT_DEF(m_gatt);                                 /**< GATT module instance. */
  BLE_IAS_DEF(m_ias, NRF_SDH_BLE_TOTAL_LINK_COUNT);         /**< Structure used to identify the Immediate Alert service. */
  
  static bool                  m_whitelist_disabled;        /**< True if whitelist has been temporarily disabled. */
  static bool                  m_memory_access_in_progress; /**< Flag to keep track of ongoing operations on persistent memory. */
  static bool                  m_sec_req_pending;           /**< Security Request is pending. */
  static ble_gap_scan_params_t m_scan_param;                /**< Scan parameters requested for scanning and connection. */
  static uint8_t               m_scan_buffer_data[BLE_GAP_SCAN_BUFFER_MIN]; /**< buffer where advertising reports will be stored by the SoftDevice. */
  
  /**@brief Pointer to the buffer where advertising reports will be stored by the SoftDevice. */
  static ble_data_t m_scan_buffer =
  {
      m_scan_buffer_data,
      BLE_GAP_SCAN_BUFFER_MIN
  };
  
  /**@brief Connection parameters requested for connection. */
  static ble_gap_conn_params_t const m_connection_param =
  {
      (uint16_t)MIN_CONN_INTERVAL,
      (uint16_t)MAX_CONN_INTERVAL,
      (uint16_t)SLAVE_LATENCY,
      (uint16_t)CONN_SUP_TIMEOUT
  };
  
  /**@brief Strings to display alert level information */
  static char const * const m_alerts[] =
  {
      "No Alert",
      "Mild Alert",
      "High Alert"
  };
  
  static void on_ias_evt(ble_ias_t * p_ias, ble_ias_evt_t * p_evt);
  static void scan_start(void);
  
  
  /**@brief Callback function for asserts in the SoftDevice.
   *
   * @details This function will be called in case of an assert in the SoftDevice.
   *
   * @warning This handler is an example only and does not fit a final product. You need to analyze
   *          how your product is supposed to react in case of an assert.
   * @warning On assert from the SoftDevice, the system can only recover on reset.
   *
   * @param[in] line_num   Line number of the failing ASSERT call.
   * @param[in] file_name  File name of the failing ASSERT call.
   */
  void assert_nrf_callback(uint16_t line_num, const uint8_t * p_file_name)
  {
      app_error_handler(DEAD_BEEF, line_num, p_file_name);
  }
  
  
  /**@brief Function for handling Peer Manager events.
   *
   * @param[in] p_evt  Peer Manager event.
   */
  static void pm_evt_handler(pm_evt_t const * p_evt)
  {
      ret_code_t err_code;
  
      switch (p_evt->evt_id)
      {
          case PM_EVT_BONDED_PEER_CONNECTED:
          {
              NRF_LOG_INFO("Connected to a previously bonded device.");
          } break;
  
          case PM_EVT_CONN_SEC_SUCCEEDED:
          {
              m_sec_req_pending = false;
              NRF_LOG_INFO("Connection secured: role: %d, conn_handle: 0x%x, procedure: %d.",
                           ble_conn_state_role(p_evt->conn_handle),
                           p_evt->conn_handle,
                           p_evt->params.conn_sec_succeeded.procedure);
              scan_start();
          } break;
  
          case PM_EVT_CONN_SEC_FAILED:
          {
              /* Often, when securing fails, it shouldn't be restarted, for security reasons.
               * Other times, it can be restarted directly.
               * Sometimes it can be restarted, but only after changing some Security Parameters.
               * Sometimes, it cannot be restarted until the link is disconnected and reconnected.
               * Sometimes it is impossible, to secure the link, or the peer device does not support it.
               * How to handle this error is highly application dependent. */
              m_sec_req_pending = false;
              NRF_LOG_INFO("Securing connection failed: role: %d, conn_handle: 0x%x, procedure: %d. Reason: 0x%04X",
                           ble_conn_state_role(p_evt->conn_handle),
                           p_evt->conn_handle,
                           p_evt->params.conn_sec_failed.procedure,
                           p_evt->params.conn_sec_failed.error);
  
              err_code = sd_ble_gap_disconnect(p_evt->conn_handle,
                                               BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
              if ((err_code != NRF_ERROR_INVALID_STATE) && (err_code != BLE_ERROR_INVALID_CONN_HANDLE))
              {
                  APP_ERROR_CHECK(err_code);
              }
          } break;
  
          case PM_EVT_CONN_SEC_CONFIG_REQ:
          {
              // Reject pairing request from an already bonded peer.
              pm_conn_sec_config_t conn_sec_config = {.allow_repairing = false};
              pm_conn_sec_config_reply(p_evt->conn_handle, &conn_sec_config);
          } break;
  
          case PM_EVT_STORAGE_FULL:
          {
              // Run garbage collection on the flash.
              err_code = fds_gc();
              if (err_code == FDS_ERR_NO_SPACE_IN_QUEUES)
              {
                  // Retry.
              }
              else
              {
                  APP_ERROR_CHECK(err_code);
              }
          } break;
  
          case PM_EVT_PEERS_DELETE_SUCCEEDED:
          {
              // Bonds are deleted. Start scanning.
              scan_start();
          } break;
  
          case PM_EVT_PEER_DATA_UPDATE_FAILED:
          {
              // Assert.
              APP_ERROR_CHECK(p_evt->params.peer_data_update_failed.error);
          } break;
  
          case PM_EVT_PEER_DELETE_FAILED:
          {
              // Assert.
              APP_ERROR_CHECK(p_evt->params.peer_delete_failed.error);
          } break;
  
          case PM_EVT_PEERS_DELETE_FAILED:
          {
              // Assert.
              APP_ERROR_CHECK(p_evt->params.peers_delete_failed_evt.error);
          } break;
  
          case PM_EVT_ERROR_UNEXPECTED:
          {
              // Assert.
              APP_ERROR_CHECK(p_evt->params.error_unexpected.error);
          } break;
  
          case PM_EVT_CONN_SEC_START:
          case PM_EVT_PEER_DATA_UPDATE_SUCCEEDED:
          case PM_EVT_PEER_DELETE_SUCCEEDED:
          case PM_EVT_LOCAL_DB_CACHE_APPLIED:
          case PM_EVT_LOCAL_DB_CACHE_APPLY_FAILED:
              // This can happen when the local DB has changed.
          case PM_EVT_SERVICE_CHANGED_IND_SENT:
          case PM_EVT_SERVICE_CHANGED_IND_CONFIRMED:
          default:
              break;
      }
  }
  
  
  /**@brief Function for handling the Security Request timer timeout.
   *
   * @details This function will be called each time the Security Request timer expires.
   *
   * @param[in]   p_context   Pointer used for passing some arbitrary information (context) from the
   *                          app_start_timer() call to the timeout handler.
   */
  static void sec_req_timeout_handler(void * p_context)
  {
      ret_code_t           err_code;
      uint16_t             conn_handle;
      pm_conn_sec_status_t status;
  
      if (p_context != NULL)
      {
          conn_handle = *((uint16_t *) p_context);
  
          NRF_LOG_INFO("Establishing secure connection using: 0x%04X.", conn_handle);
  
          if (conn_handle != BLE_CONN_HANDLE_INVALID)
          {
              err_code = pm_conn_sec_status_get(conn_handle, &status);
              APP_ERROR_CHECK(err_code);
  
              // If the link is still not secured by the peer, initiate security procedure.
              if (!status.encrypted)
              {
                  err_code = pm_conn_secure(conn_handle, false);
                  APP_ERROR_CHECK(err_code);
              }
          }
      }
      else
      {
          NRF_LOG_ERROR("No connection handle context available");
      }
  }
  
  
  /**@brief Function for the Timer initialization.
   *
   * @details Initializes the timer module. This creates and starts application timers.
   */
  static void timers_init(void)
  {
      ret_code_t err_code;
  
      // Initialize timer module.
      err_code = app_timer_init();
      APP_ERROR_CHECK(err_code);
  
      // Create Security Request timer.
      err_code = app_timer_create(&m_sec_req_timer_id,
                                  APP_TIMER_MODE_SINGLE_SHOT,
                                  sec_req_timeout_handler);
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@brief Function for initializing the GATT module.
   */
  static void gatt_init(void)
  {
      ret_code_t err_code = nrf_ble_gatt_init(&m_gatt, NULL);
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@brief Function for putting the chip into sleep mode.
   *
   * @note This function will not return.
   */
  static void sleep_mode_enter(void)
  {
      ret_code_t err_code;
  
      // Turn off LEDs
      bsp_board_led_off(CENTRAL_CONNECTED_LED);
      bsp_board_led_off(CENTRAL_SCANNING_LED);
  
      err_code = bsp_indication_set(BSP_INDICATE_ALERT_OFF);
      APP_ERROR_CHECK(err_code);
  
      // Prepare wakeup buttons.
      err_code = bsp_btn_ble_sleep_mode_prepare();
      APP_ERROR_CHECK(err_code);
  
      // Go to system-off mode (this function will not return; wakeup will cause a reset).
      err_code = sd_power_system_off();
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@brief Function for initializing the Immediate Alert Service.
   */
  static void ias_init(void)
  {
      ret_code_t     err_code;
      ble_ias_init_t ias_init_obj;
  
      memset(&ias_init_obj, 0, sizeof(ias_init_obj));
      ias_init_obj.evt_handler = on_ias_evt;
  
      err_code = ble_ias_init(&m_ias, &ias_init_obj);
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@brief Function for initializing the services that will be used by the application.
   */
  static void services_init(void)
  {
      ias_init();
  }
  
  
  /**@brief Function for the Signals alert event from the Immediate Alert service.
   *
   * @param[in] alert_level  Requested alert level.
   */
  static void alert_signal(uint8_t alert_level)
  {
      ret_code_t err_code;
  
      if (alert_level < ARRAY_SIZE(m_alerts))
      {
          NRF_LOG_INFO("%s.", m_alerts[alert_level]);
      }
  
      switch (alert_level)
      {
          case BLE_CHAR_ALERT_LEVEL_NO_ALERT:
              err_code = bsp_indication_set(BSP_INDICATE_ALERT_OFF);
              APP_ERROR_CHECK(err_code);
              break;
  
          case BLE_CHAR_ALERT_LEVEL_MILD_ALERT:
              err_code = bsp_indication_set(BSP_INDICATE_ALERT_0);
              APP_ERROR_CHECK(err_code);
              break;
  
          case BLE_CHAR_ALERT_LEVEL_HIGH_ALERT:
              err_code = bsp_indication_set(BSP_INDICATE_ALERT_3);
              APP_ERROR_CHECK(err_code);
              break;
  
          default:
              // No implementation needed.
              break;
      }
  }
  
  
  /**@brief Function for determining current alert level.
   *
   * @details This function will be called for @ref BLE_IAS_EVT_ALERT_LEVEL_UPDATED event which is
   *          passed to the application. It will determine the current alert level by finding
   *          the maximum one among connected peers.
   */
  static uint8_t alert_level_resolve(void)
  {
      ret_code_t                        err_code;
      uint8_t                           alert_level;
      uint8_t                           max_alert_level = BLE_CHAR_ALERT_LEVEL_NO_ALERT;
      ble_conn_state_conn_handle_list_t conn_handles    = ble_conn_state_conn_handles();
  
      // Iterate over all valid connection handles.
      for (uint32_t i = 0; i < conn_handles.len; i++)
      {
          if (ble_conn_state_status(conn_handles.conn_handles[i]) == BLE_CONN_STATUS_CONNECTED)
          {
              err_code = ble_ias_alert_level_get(&m_ias, conn_handles.conn_handles[i], &alert_level);
              APP_ERROR_CHECK(err_code);
  
              max_alert_level = (alert_level > max_alert_level) ? alert_level : max_alert_level;
          }
      }
      return max_alert_level;
  }
  
  
  /**@brief Function for handling Immediate Alert events.
   *
   * @details This function will be called for all Immediate Alert events which are passed to the
   *          application.
   *
   * @param[in] p_ias  Immediate Alert structure.
   * @param[in] p_evt  Event received from the Immediate Alert service.
   */
  static void on_ias_evt(ble_ias_t * p_ias, ble_ias_evt_t * p_evt)
  {
      NRF_LOG_DEBUG("Received IAS event from conn_handle: 0x%04X.", p_evt->conn_handle);
  
      switch (p_evt->evt_type)
      {
          case BLE_IAS_EVT_ALERT_LEVEL_UPDATED:
          {
              uint8_t alert_level;
  
              if (p_evt->p_link_ctx != NULL)
              {
                  NRF_LOG_INFO("New alert level: %s from conn_handle: 0x%04X.",
                               m_alerts[p_evt->p_link_ctx->alert_level],
                               p_evt->conn_handle);
              }
              else
              {
                  NRF_LOG_ERROR("No alert context for conn_handle: 0x%04X", p_evt->conn_handle);
              }
  
              // Update common alert level.
              alert_level = alert_level_resolve();
              alert_signal(alert_level);
          } break;
  
          default:
              // No implementation needed.
              break;
      }
  }
  
  
  /**@brief Function for handling the advertising report BLE event.
   *
   * @param[in] p_adv_report  Advertising report from the SoftDevice.
   */
  static void on_adv_report(ble_gap_evt_adv_report_t const * p_adv_report)
  {
      ret_code_t err_code;
      ble_uuid_t target_uuid = {.uuid = TARGET_UUID, .type = BLE_UUID_TYPE_BLE};
  
      if (ble_advdata_uuid_find(p_adv_report->data.p_data, p_adv_report->data.len, &target_uuid))
      {
          // Stop scanning.
          (void) sd_ble_gap_scan_stop();
  
          err_code = bsp_indication_set(BSP_INDICATE_IDLE);
          APP_ERROR_CHECK(err_code);
  
          // Initiate connection.
          m_scan_param.filter_policy = BLE_GAP_SCAN_FP_ACCEPT_ALL;
  
          err_code = sd_ble_gap_connect(&p_adv_report->peer_addr,
                                        &m_scan_param,
                                        &m_connection_param,
                                        APP_BLE_CONN_CFG_TAG);
  
          m_whitelist_disabled = false;
  
          if (err_code != NRF_SUCCESS)
          {
              NRF_LOG_DEBUG("Connection Request Failed, reason 0x%x", err_code);
          }
      }
      else
      {
          err_code = sd_ble_gap_scan_start(NULL, &m_scan_buffer);
          APP_ERROR_CHECK(err_code);
      }
  }
  
  
  /**@brief Function for handling BLE events.
   *
   * @param[in]   p_ble_evt   Bluetooth stack event.
   * @param[in]   p_context   Unused.
   */
  static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)
  {
      ret_code_t            err_code = NRF_SUCCESS;
      ble_gap_evt_t const * p_gap_evt = &p_ble_evt->evt.gap_evt;
      static uint16_t       m_conn_handle;
  
      switch (p_ble_evt->header.evt_id)
      {
          case BLE_GAP_EVT_CONNECTED:
          {
              NRF_LOG_INFO("Connected using conn_handle: 0x%04X.",
                           p_ble_evt->evt.gap_evt.conn_handle);
  
              // Handle LEDs.
              bsp_board_led_on(CENTRAL_CONNECTED_LED);
              bsp_board_led_off(CENTRAL_SCANNING_LED);
  
              // Prepare security request.
              m_sec_req_pending = true;
              m_conn_handle     = p_ble_evt->evt.gap_evt.conn_handle;
              err_code          = app_timer_start(m_sec_req_timer_id,
                                                  SECURITY_REQUEST_DELAY,
                                                  &m_conn_handle);
              APP_ERROR_CHECK(err_code);
          } break;
  
          case BLE_GAP_EVT_DISCONNECTED:
              NRF_LOG_INFO("Disconnected using conn_handle: 0x%04X.",
                           p_ble_evt->evt.gap_evt.conn_handle);
  
              //Handle LEDs.
              if (ble_conn_state_central_conn_count() == 0)
              {
                  bsp_board_led_off(CENTRAL_CONNECTED_LED);
              }
  
              if (p_ble_evt->evt.gap_evt.params.disconnected.reason ==
                  BLE_HCI_LOCAL_HOST_TERMINATED_CONNECTION)
              {
                  bsp_board_led_off(CENTRAL_SCANNING_LED);
                  (void) sd_ble_gap_scan_stop();
              }
              else
              {
                  // Start scanning
                  scan_start();
              }
              break;
  
          case BLE_GAP_EVT_ADV_REPORT:
              on_adv_report(&p_gap_evt->params.adv_report);
              break;
  
          case BLE_GAP_EVT_TIMEOUT:
          {
              if (p_ble_evt->evt.gap_evt.params.timeout.src == BLE_GAP_TIMEOUT_SRC_SCAN)
              {
                  NRF_LOG_DEBUG("Scan timed out.");
                  scan_start();
              }
              else if (p_ble_evt->evt.gap_evt.params.timeout.src == BLE_GAP_TIMEOUT_SRC_CONN)
              {
                  NRF_LOG_INFO("Connection Request timed out.");
              }
          } break;
  
          case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
          {
              NRF_LOG_DEBUG("PHY update request.");
              ble_gap_phys_t const phys =
              {
                  .rx_phys = BLE_GAP_PHY_AUTO,
                  .tx_phys = BLE_GAP_PHY_AUTO,
              };
              err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
              APP_ERROR_CHECK(err_code);
          } break;
  
          case BLE_GATTC_EVT_TIMEOUT:
              // Disconnect on GATT Client timeout event.
              NRF_LOG_DEBUG("GATT Client Timeout.");
              err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gattc_evt.conn_handle,
                                               BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
              APP_ERROR_CHECK(err_code);
              break;
  
          case BLE_GATTS_EVT_TIMEOUT:
              // Disconnect on GATT Server timeout event.
              NRF_LOG_DEBUG("GATT Server Timeout.");
              err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gatts_evt.conn_handle,
                                               BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
              APP_ERROR_CHECK(err_code);
              break;
  
          case BLE_GAP_EVT_CONN_PARAM_UPDATE_REQUEST:
              // Accepting parameters requested by peer.
              err_code = sd_ble_gap_conn_param_update(p_ble_evt->evt.gap_evt.conn_handle,
                                                      &p_ble_evt->evt.gap_evt.params.conn_param_update_request.conn_params);
              APP_ERROR_CHECK(err_code);
              break;
  
          default:
              // No implementation needed.
              break;
      }
  }
  
  
  /**@brief SoftDevice SoC event handler.
   *
   * @param[in]   evt_id      SoC event.
   * @param[in]   p_context   Context.
   */
  static void soc_evt_handler(uint32_t sys_evt, void * p_context)
  {
      switch (sys_evt)
      {
          case NRF_EVT_FLASH_OPERATION_SUCCESS:
              /* fall through */
          case NRF_EVT_FLASH_OPERATION_ERROR:
  
              if (m_memory_access_in_progress)
              {
                  m_memory_access_in_progress = false;
                  scan_start();
              }
              break;
  
          default:
              // No implementation needed.
              break;
      }
  }
  
  
  /**@brief Function for initializing the BLE stack.
   *
   * @details Initializes the SoftDevice and the BLE event interrupt.
   */
  static void ble_stack_init(void)
  {
      ret_code_t err_code;
  
      err_code = nrf_sdh_enable_request();
      APP_ERROR_CHECK(err_code);
  
      // Configure the BLE stack using the default settings.
      // Fetch the start address of the application RAM.
      uint32_t ram_start = 0;
      err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);
      APP_ERROR_CHECK(err_code);
  
      // Enable BLE stack.
      err_code = nrf_sdh_ble_enable(&ram_start);
      APP_ERROR_CHECK(err_code);
  
      // Register a handler for BLE and SoC events.
      NRF_SDH_BLE_OBSERVER(m_ble_observer, APP_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);
      NRF_SDH_SOC_OBSERVER(m_soc_observer, APP_SOC_OBSERVER_PRIO, soc_evt_handler, NULL);
  }
  
  
  /**@brief Function for the Peer Manager initialization.
   */
  static void peer_manager_init(void)
  {
      ble_gap_sec_params_t sec_param;
      ret_code_t           err_code;
  
      err_code = pm_init();
      APP_ERROR_CHECK(err_code);
  
      memset(&sec_param, 0, sizeof(ble_gap_sec_params_t));
  
      // Security parameters to be used for all security procedures.
      sec_param.bond           = SEC_PARAM_BOND;
      sec_param.mitm           = SEC_PARAM_MITM;
      sec_param.lesc           = SEC_PARAM_LESC;
      sec_param.keypress       = SEC_PARAM_KEYPRESS;
      sec_param.io_caps        = SEC_PARAM_IO_CAPABILITIES;
      sec_param.oob            = SEC_PARAM_OOB;
      sec_param.min_key_size   = SEC_PARAM_MIN_KEY_SIZE;
      sec_param.max_key_size   = SEC_PARAM_MAX_KEY_SIZE;
      sec_param.kdist_own.enc  = 1;
      sec_param.kdist_own.id   = 1;
      sec_param.kdist_peer.enc = 1;
      sec_param.kdist_peer.id  = 1;
  
      err_code = pm_sec_params_set(&sec_param);
      APP_ERROR_CHECK(err_code);
  
      err_code = pm_register(pm_evt_handler);
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@brief Function for disabling the use of whitelist and starting scanning.
   */
  static void whitelist_disable_and_scan(void)
  {
      if (!m_whitelist_disabled)
      {
          NRF_LOG_INFO("Whitelist temporarily disabled.");
          m_whitelist_disabled = true;
      }
  
      if (!m_sec_req_pending)
      {
          scan_start();
      }
  }
  
  
  /**@brief Function for handling events from the BSP module.
   *
   * @param[in]   event   Event generated when button is pressed.
   */
  static void bsp_event_handler(bsp_event_t event)
  {
      switch (event)
      {
          case BSP_EVENT_SLEEP:
              sleep_mode_enter();
              break;
  
          case BSP_EVENT_WHITELIST_OFF:
              whitelist_disable_and_scan();
              break;
  
          default:
              break;
      }
  }
  
  
  /**@brief Function for retrieving a list of peer manager peer IDs.
   *
   * @param[inout] p_peers   The buffer where to store the list of peer IDs.
   * @param[inout] p_size    In: The size of the @p p_peers buffer.
   *                         Out: The number of peers copied in the buffer.
   */
  static void peer_list_get(pm_peer_id_t * p_peers, uint32_t * p_size)
  {
      pm_peer_id_t peer_id;
      uint32_t     peers_to_copy;
  
      peers_to_copy = (*p_size < BLE_GAP_WHITELIST_ADDR_MAX_COUNT) ?
                       *p_size : BLE_GAP_WHITELIST_ADDR_MAX_COUNT;
  
      peer_id = pm_next_peer_id_get(PM_PEER_ID_INVALID);
      *p_size = 0;
  
      while ((peer_id != PM_PEER_ID_INVALID) && (peers_to_copy--))
      {
          p_peers[(*p_size)++] = peer_id;
          peer_id = pm_next_peer_id_get(peer_id);
      }
  }
  
  
  static void whitelist_load()
  {
      ret_code_t   ret;
      pm_peer_id_t peers[8];
      uint32_t     peer_cnt;
  
      memset(peers, PM_PEER_ID_INVALID, sizeof(peers));
      peer_cnt = (sizeof(peers) / sizeof(pm_peer_id_t));
  
      // Load all peers from flash and whitelist them.
      peer_list_get(peers, &peer_cnt);
  
      ret = pm_whitelist_set(peers, peer_cnt);
      APP_ERROR_CHECK(ret);
  
      // Set up the device identities list.
      // Some SoftDevices do not support this feature.
      ret = pm_device_identities_list_set(peers, peer_cnt);
      if (ret != NRF_ERROR_NOT_SUPPORTED)
      {
          APP_ERROR_CHECK(ret);
      }
  }
  
  
  /**@brief Function for starting the scanning.
   */
  static void scan_start(void)
  {
      ret_code_t err_code;
      bool       whitelist_on;
  
      (void) sd_ble_gap_scan_stop();
      bsp_board_led_off(CENTRAL_SCANNING_LED);
  
      // Check if there is available connection slot.
      if (ble_conn_state_central_conn_count() >= NRF_SDH_BLE_CENTRAL_LINK_COUNT)
      {
          NRF_LOG_DEBUG("Maximum number of connections: %d has been reached. Scanning cannot be restarted",
                        NRF_SDH_BLE_CENTRAL_LINK_COUNT);
          return;
      }
  
      if (nrf_fstorage_is_busy(NULL))
      {
          m_memory_access_in_progress = true;
          return;
      }
  
      // Whitelist buffers.
      ble_gap_addr_t whitelist_addrs[8];
      ble_gap_irk_t  whitelist_irks[8];
  
      memset(whitelist_addrs, 0x00, sizeof(whitelist_addrs));
      memset(whitelist_irks,  0x00, sizeof(whitelist_irks));
  
      uint32_t addr_cnt = (sizeof(whitelist_addrs) / sizeof(ble_gap_addr_t));
      uint32_t irk_cnt  = (sizeof(whitelist_irks)  / sizeof(ble_gap_irk_t));
  
      // Reload the whitelist and whitelist all peers.
      whitelist_load();
  
      // Get the whitelist previously set using pm_whitelist_set().
      err_code = pm_whitelist_get(whitelist_addrs, &addr_cnt,
                                  whitelist_irks,  &irk_cnt);
      APP_ERROR_CHECK(err_code);
  
      m_scan_param.active   = 0;
      m_scan_param.interval = SCAN_INTERVAL;
      m_scan_param.window   = SCAN_WINDOW;
  
      if (((addr_cnt == 0) && (irk_cnt == 0)) ||
          (m_whitelist_disabled))
      {
          // Don't use whitelist
          whitelist_on = false;
  
          m_scan_param.timeout           = SCAN_DURATION;
          m_scan_param.scan_phys         = BLE_GAP_PHY_1MBPS;
          m_scan_param.filter_policy     = BLE_GAP_SCAN_FP_ACCEPT_ALL;
      }
      else
      {
          // Use whitelist.
          whitelist_on = true;
  
          m_scan_param.scan_phys          = BLE_GAP_PHY_1MBPS;
          m_scan_param.filter_policy     = BLE_GAP_SCAN_FP_WHITELIST;
          m_scan_param.timeout          = 0x001E; // 30 seconds.
      }
  
      err_code = sd_ble_gap_scan_start(&m_scan_param, &m_scan_buffer);
      APP_ERROR_CHECK(err_code);
  
      bsp_board_led_on(CENTRAL_SCANNING_LED);
  
      if (whitelist_on)
      {
          NRF_LOG_INFO("Starting scan with whitelist.");
      }
      else
      {
          NRF_LOG_INFO("Starting scan.");
      }
  }
  
  
  /**@brief Function for initializing buttons and LEDs.
   *
   * @param[out] p_erase_bonds  Will be true if the clear bonding button was pressed to wake the application up.
   */
  static void buttons_leds_init(bool * p_erase_bonds)
  {
      ret_code_t  err_code;
      bsp_event_t startup_event;
  
      err_code = bsp_init(BSP_INIT_LEDS | BSP_INIT_BUTTONS, bsp_event_handler);
      APP_ERROR_CHECK(err_code);
  
      err_code = bsp_btn_ble_init(NULL, &startup_event);
      APP_ERROR_CHECK(err_code);
  
      *p_erase_bonds = (startup_event == BSP_EVENT_CLEAR_BONDING_DATA);
  }
  
  
  /**@brief Function for initializing the nrf_log module.
   */
  static void log_init(void)
  {
      ret_code_t err_code = NRF_LOG_INIT(NULL);
      APP_ERROR_CHECK(err_code);
  
      NRF_LOG_DEFAULT_BACKENDS_INIT();
  }
  
  
  /**@brief Function for initializing power management.
   */
  static void power_management_init(void)
  {
      ret_code_t err_code;
      err_code = nrf_pwr_mgmt_init();
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@brief Function for handling the idle state (main loop).
   *
   * @details Handle any pending log operation(s), then sleep until the next event occurs.
   */
  static void idle_state_handle(void)
  {
      if (NRF_LOG_PROCESS() == false)
      {
          nrf_pwr_mgmt_run();
      }
  }
  
  
  /**@brief Clear bond information from persistent storage.
   */
  static void delete_bonds(void)
  {
      ret_code_t err_code;
  
      NRF_LOG_INFO("Erase bonds!");
  
      err_code = pm_peers_delete();
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@brief Function for starting a scan, or instead trigger it from peer manager (after
   *        deleting bonds).
   *
   * @param[in] p_erase_bonds Pointer to a bool to determine if bonds will be deleted before scanning.
   */
  void scanning_start(bool * p_erase_bonds)
  {
      // Start scanning for peripherals and initiate connection
      // with devices that advertise GATT Service UUID.
      if (*p_erase_bonds == true)
      {
          // Scan is started by the PM_EVT_PEERS_DELETE_SUCCEEDED event.
          delete_bonds();
      }
      else
      {
          scan_start();
      }
  }
  
  
  /**@brief Function for application main entry.
   */
  int main(void)
  {
      bool erase_bonds;
  
      // Initialize.
      log_init();
      timers_init();
      buttons_leds_init(&erase_bonds);
      power_management_init();
      ble_stack_init();
      gatt_init();
      peer_manager_init();
      services_init();
  
      // Start execution.
      NRF_LOG_INFO("Immediate Alert example started.");
      scanning_start(&erase_bonds);
  
      // Enter main loop.
      for (;;)
      {
          idle_state_handle();
      }
  }
  
  
  /**
   * @}
   */
  