text: // Copyright 2015-2018 Espressif Systems (Shanghai) PTE LTD
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  #pragma once
  
  #include <stdint.h>
  #include <stdbool.h>
  
  #include "esp_err.h"
  #include "esp_wifi_types.h"
  #include "tcpip_adapter.h"
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /** System event types enumeration */
  typedef enum {
      SYSTEM_EVENT_WIFI_READY = 0,           /*!< ESP32 WiFi ready */
      SYSTEM_EVENT_SCAN_DONE,                /*!< ESP32 finish scanning AP */
      SYSTEM_EVENT_STA_START,                /*!< ESP32 station start */
      SYSTEM_EVENT_STA_STOP,                 /*!< ESP32 station stop */
      SYSTEM_EVENT_STA_CONNECTED,            /*!< ESP32 station connected to AP */
      SYSTEM_EVENT_STA_DISCONNECTED,         /*!< ESP32 station disconnected from AP */
      SYSTEM_EVENT_STA_AUTHMODE_CHANGE,      /*!< the auth mode of AP connected by ESP32 station changed */
      SYSTEM_EVENT_STA_GOT_IP,               /*!< ESP32 station got IP from connected AP */
      SYSTEM_EVENT_STA_LOST_IP,              /*!< ESP32 station lost IP and the IP is reset to 0 */
      SYSTEM_EVENT_STA_WPS_ER_SUCCESS,       /*!< ESP32 station wps succeeds in enrollee mode */
      SYSTEM_EVENT_STA_WPS_ER_FAILED,        /*!< ESP32 station wps fails in enrollee mode */
      SYSTEM_EVENT_STA_WPS_ER_TIMEOUT,       /*!< ESP32 station wps timeout in enrollee mode */
      SYSTEM_EVENT_STA_WPS_ER_PIN,           /*!< ESP32 station wps pin code in enrollee mode */
      SYSTEM_EVENT_STA_WPS_ER_PBC_OVERLAP,   /*!< ESP32 station wps overlap in enrollee mode */
      SYSTEM_EVENT_AP_START,                 /*!< ESP32 soft-AP start */
      SYSTEM_EVENT_AP_STOP,                  /*!< ESP32 soft-AP stop */
      SYSTEM_EVENT_AP_STACONNECTED,          /*!< a station connected to ESP32 soft-AP */
      SYSTEM_EVENT_AP_STADISCONNECTED,       /*!< a station disconnected from ESP32 soft-AP */
      SYSTEM_EVENT_AP_STAIPASSIGNED,         /*!< ESP32 soft-AP assign an IP to a connected station */
      SYSTEM_EVENT_AP_PROBEREQRECVED,        /*!< Receive probe request packet in soft-AP interface */
      SYSTEM_EVENT_GOT_IP6,                  /*!< ESP32 station or ap or ethernet interface v6IP addr is preferred */
      SYSTEM_EVENT_ETH_START,                /*!< ESP32 ethernet start */
      SYSTEM_EVENT_ETH_STOP,                 /*!< ESP32 ethernet stop */
      SYSTEM_EVENT_ETH_CONNECTED,            /*!< ESP32 ethernet phy link up */
      SYSTEM_EVENT_ETH_DISCONNECTED,         /*!< ESP32 ethernet phy link down */
      SYSTEM_EVENT_ETH_GOT_IP,               /*!< ESP32 ethernet got IP from connected AP */
      SYSTEM_EVENT_MAX                       /*!< Number of members in this enum */
  } system_event_id_t;
  
  /* add this macro define for compatible with old IDF version */
  #ifndef SYSTEM_EVENT_AP_STA_GOT_IP6
  #define SYSTEM_EVENT_AP_STA_GOT_IP6 SYSTEM_EVENT_GOT_IP6
  #endif
  
  
  /** Argument structure of SYSTEM_EVENT_STA_WPS_ER_FAILED event */
  typedef wifi_event_sta_wps_fail_reason_t system_event_sta_wps_fail_reason_t;
  
  /** Argument structure of SYSTEM_EVENT_SCAN_DONE event */
  typedef wifi_event_sta_scan_done_t system_event_sta_scan_done_t;
  
  /** Argument structure of SYSTEM_EVENT_STA_CONNECTED event */
  typedef wifi_event_sta_connected_t system_event_sta_connected_t;
  
  /** Argument structure of SYSTEM_EVENT_STA_DISCONNECTED event */
  typedef wifi_event_sta_disconnected_t system_event_sta_disconnected_t;
  
  /** Argument structure of SYSTEM_EVENT_STA_AUTHMODE_CHANGE event */
  typedef wifi_event_sta_authmode_change_t system_event_sta_authmode_change_t;
  
  /** Argument structure of SYSTEM_EVENT_STA_WPS_ER_PIN event */
  typedef wifi_event_sta_wps_er_pin_t system_event_sta_wps_er_pin_t;
  
  /** Argument structure of  event */
  typedef wifi_event_ap_staconnected_t system_event_ap_staconnected_t;
  
  /** Argument structure of  event */
  typedef wifi_event_ap_stadisconnected_t system_event_ap_stadisconnected_t;
  
  /** Argument structure of  event */
  typedef wifi_event_ap_probe_req_rx_t system_event_ap_probe_req_rx_t;
  
  /** Argument structure of  event */
  typedef ip_event_ap_staipassigned_t system_event_ap_staipassigned_t;
  
  /** Argument structure of  event */
  typedef ip_event_got_ip_t system_event_sta_got_ip_t;
  
  /** Argument structure of  event */
  typedef ip_event_got_ip6_t system_event_got_ip6_t;
  
  /** Union of all possible system_event argument structures */
  typedef union {
      system_event_sta_connected_t               connected;          /*!< ESP32 station connected to AP */
      system_event_sta_disconnected_t            disconnected;       /*!< ESP32 station disconnected to AP */
      system_event_sta_scan_done_t               scan_done;          /*!< ESP32 station scan (APs) done */
      system_event_sta_authmode_change_t         auth_change;        /*!< the auth mode of AP ESP32 station connected to changed */
      system_event_sta_got_ip_t                  got_ip;             /*!< ESP32 station got IP, first time got IP or when IP is changed */
      system_event_sta_wps_er_pin_t              sta_er_pin;         /*!< ESP32 station WPS enrollee mode PIN code received */
      system_event_sta_wps_fail_reason_t         sta_er_fail_reason; /*!< ESP32 station WPS enrollee mode failed reason code received */
      system_event_ap_staconnected_t             sta_connected;      /*!< a station connected to ESP32 soft-AP */
      system_event_ap_stadisconnected_t          sta_disconnected;   /*!< a station disconnected to ESP32 soft-AP */
      system_event_ap_probe_req_rx_t             ap_probereqrecved;  /*!< ESP32 soft-AP receive probe request packet */
      system_event_ap_staipassigned_t            ap_staipassigned;   /**< ESP32 soft-AP assign an IP to the station*/
      system_event_got_ip6_t                     got_ip6;            /*!< ESP32 station　or ap or ethernet ipv6 addr state change to preferred */
  } system_event_info_t;
  
  /** Event, as a tagged enum */
  typedef struct {
      system_event_id_t     event_id;      /*!< event ID */
      system_event_info_t   event_info;    /*!< event information */
  } system_event_t;
  
  /** Event handler function type */
  typedef esp_err_t (*system_event_handler_t)(system_event_t *event);
  
  /**
    * @brief  Send a event to event task
    *
    * @note This API is part of the legacy event system. New code should use event library API in esp_event.h
    *
    * Other task/modules, such as the tcpip_adapter, can call this API to send an event to event task
    *
    * @param event Event to send
    *
    * @return ESP_OK : succeed
    * @return others : fail
    */
  esp_err_t esp_event_send(system_event_t *event);
  
  /**
   * @brief  Default event handler for system events
   *
   * @note This API is part of the legacy event system. New code should use event library API in esp_event.h
   *
   * This function performs default handling of system events.
   * When using esp_event_loop APIs, it is called automatically before invoking the user-provided
   * callback function.
   *
   * Applications which implement a custom event loop must call this function
   * as part of event processing.
   *
   * @param  event   pointer to event to be handled
   * @return ESP_OK if an event was handled successfully
   */
  esp_err_t esp_event_process_default(system_event_t *event);
  
  /**
    * @brief  Install default event handlers for Ethernet interface
    *
    * @note This API is part of the legacy event system. New code should use event library API in esp_event.h
    *
    */
  void esp_event_set_default_eth_handlers();
  
  /**
    * @brief  Install default event handlers for Wi-Fi interfaces (station and AP)
    *
    * @note This API is part of the legacy event system. New code should use event library API in esp_event.h
    */
  void esp_event_set_default_wifi_handlers();
  
  /**
   * @brief  Application specified event callback function
   *
   * @note This API is part of the legacy event system. New code should use event library API in esp_event.h
   *
   *
   * @param  ctx    reserved for user
   * @param  event  event type defined in this file
   *
   * @return
   *    - ESP_OK: succeed
   *    - others: fail
   */
  typedef esp_err_t (*system_event_cb_t)(void *ctx, system_event_t *event);
  
  /**
   * @brief  Initialize event loop
   *
   * @note This API is part of the legacy event system. New code should use event library API in esp_event.h
   *
   * Create the event handler and task
   *
   * @param  cb   application specified event callback, it can be modified by call esp_event_set_cb
   * @param  ctx  reserved for user
   *
   * @return
   *    - ESP_OK: succeed
   *    - others: fail
   */
  esp_err_t esp_event_loop_init(system_event_cb_t cb, void *ctx);
  
  /**
   * @brief  Set application specified event callback function
   *
   * @note This API is part of the legacy event system. New code should use event library API in esp_event.h
   *
   * @attention 1. If cb is NULL, means application don't need to handle
   *               If cb is not NULL, it will be call when an event is received, after the default event callback is completed
   *
   * @param  cb   application callback function
   * @param  ctx  argument to be passed to callback
   *
   *
   * @return old callback
   */
  system_event_cb_t esp_event_loop_set_cb(system_event_cb_t cb, void *ctx);
  
  #ifdef __cplusplus
  }
  #endif
  
  