#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_system.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "nvs_flash.h"
#include "nvs.h"
#include "lwip/err.h"
#include "lwip/sys.h"

#define WIFI_SSID_MAX_LEN 32
#define WIFI_PASS_MAX_LEN 64
#define MAX_RETRY 5

static EventGroupHandle_t s_wifi_event_group;
#define WIFI_CONNECTED_BIT BIT0
#define WIFI_FAIL_BIT      BIT1

static const char *TAG = "wifi_nvm_sta";
static int s_retry_num = 0;

void save_wifi_creds(const char *ssid, const char *pass) {
    nvs_handle_t nvs_handle;
    ESP_ERROR_CHECK(nvs_open("wifi_creds", NVS_READWRITE, &nvs_handle));
    ESP_ERROR_CHECK(nvs_set_str(nvs_handle, "ssid", ssid));
    ESP_ERROR_CHECK(nvs_set_str(nvs_handle, "pass", pass));
    ESP_ERROR_CHECK(nvs_commit(nvs_handle));
    nvs_close(nvs_handle);
    ESP_LOGI(TAG, "WiFi credentials saved");
}

bool load_wifi_creds(char *ssid, size_t ssid_len, char *pass, size_t pass_len) {
    nvs_handle_t nvs_handle;
    esp_err_t err = nvs_open("wifi_creds", NVS_READONLY, &nvs_handle);
    if (err != ESP_OK) return false;

    err = nvs_get_str(nvs_handle, "ssid", ssid, &ssid_len);
    if (err != ESP_OK) {
        nvs_close(nvs_handle);
        return false;
    }

    err = nvs_get_str(nvs_handle, "pass", pass, &pass_len);
    nvs_close(nvs_handle);
    return err == ESP_OK;
}

static void event_handler(void* arg, esp_event_base_t event_base,
                          int32_t event_id, void* event_data) {
    if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_START) {
        esp_wifi_connect();
    } else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
        if (s_retry_num < MAX_RETRY) {
            esp_wifi_connect();
            s_retry_num++;
            ESP_LOGI(TAG, "retrying connection to AP");
        } else {
            xEventGroupSetBits(s_wifi_event_group, WIFI_FAIL_BIT);
        }
        ESP_LOGI(TAG,"failed to connect to AP");
    } else if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
        ip_event_got_ip_t* event = (ip_event_got_ip_t*) event_data;
        ESP_LOGI(TAG, "got ip: " IPSTR, IP2STR(&event->ip_info.ip));
        s_retry_num = 0;
        xEventGroupSetBits(s_wifi_event_group, WIFI_CONNECTED_BIT);
    }
}

void wifi_init_sta(void) {
    char ssid[WIFI_SSID_MAX_LEN] = {0};
    char pass[WIFI_PASS_MAX_LEN] = {0};

    bool creds_loaded = load_wifi_creds(ssid, sizeof(ssid), pass, sizeof(pass));

    if (!creds_loaded) {
        // Default open network: UCLA_WIFI
        strcpy(ssid, "UCLA_WIFI");
        pass[0] = '\0';  // No password
        save_wifi_creds(ssid, pass);
    }

    s_wifi_event_group = xEventGroupCreate();
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());
    esp_netif_create_default_wifi_sta();

    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK(esp_wifi_init(&cfg));

    esp_event_handler_instance_t instance_any_id;
    esp_event_handler_instance_t instance_got_ip;
    ESP_ERROR_CHECK(esp_event_handler_instance_register(WIFI_EVENT, ESP_EVENT_ANY_ID, &event_handler, NULL, &instance_any_id));
    ESP_ERROR_CHECK(esp_event_handler_instance_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &event_handler, NULL, &instance_got_ip));

    wifi_config_t wifi_config = { 0 };
    strncpy((char *)wifi_config.sta.ssid, ssid, sizeof(wifi_config.sta.ssid));
    strncpy((char *)wifi_config.sta.password, pass, sizeof(wifi_config.sta.password));
    wifi_config.sta.threshold.authmode = WIFI_AUTH_OPEN;

    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
    ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_config));
    ESP_ERROR_CHECK(esp_wifi_start());

    ESP_LOGI(TAG, "wifi_init_sta finished.");

    EventBits_t bits = xEventGroupWaitBits(s_wifi_event_group,
                                           WIFI_CONNECTED_BIT | WIFI_FAIL_BIT,
                                           pdFALSE,
                                           pdFALSE,
                                           portMAX_DELAY);

    if (bits & WIFI_CONNECTED_BIT) {
        ESP_LOGI(TAG, "connected to SSID:%s", ssid);
    } else if (bits & WIFI_FAIL_BIT) {
        ESP_LOGI(TAG, "Failed to connect to SSID:%s", ssid);
    } else {
        ESP_LOGE(TAG, "UNEXPECTED EVENT");
    }
}

void app_main(void) {
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
        ESP_ERROR_CHECK(nvs_flash_erase());
        ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK(ret);

    ESP_LOGI(TAG, "ESP_WIFI_MODE_STA");
    wifi_init_sta();
}