#include <string.h>

#include "esp_event.h"
#include "esp_log.h"
#include "esp_netif.h"
#include "esp_system.h"
#include "esp_timer.h"
#include "esp_wifi.h"
#include "freertos/FreeRTOS.h"
#include "freertos/event_groups.h"
#include "nvs_flash.h"

#include "app_config.h"
#include "wifi_manager.h"

static const char *TAG = "wifi_manager";

#define WIFI_CONNECTED_BIT BIT0
#define WIFI_FAIL_BIT      BIT1
#define WIFI_MAX_RETRIES   8
#define WIFI_CONNECT_TIMEOUT_MS 30000
/* After the fast retries are spent, keep trying at this interval forever --
 * this is a wall appliance, so an AP outage must not require a power cycle. */
#define WIFI_RECONNECT_DELAY_MS 30000

static EventGroupHandle_t s_wifi_event_group = NULL;
static esp_timer_handle_t s_reconnect_timer = NULL;
static int s_retry_count = 0;

static void reconnect_timer_cb(void *arg)
{
    ESP_LOGI(TAG, "Slow reconnect attempt");
    esp_wifi_connect();
}

static void wifi_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();
        return;
    }

    if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
        /* Without this, wifi_is_connected() keeps reporting true after a
         * drop and callers never notice the link is gone. */
        xEventGroupClearBits(s_wifi_event_group, WIFI_CONNECTED_BIT);

        /*
         * A bounded burst of immediate retries covers transient drops;
         * signalling failure on the first disconnect (as this previously did)
         * meant a single blip was reported as a hard failure. Once the burst
         * is spent, fall back to a slow periodic retry instead of giving up:
         * FAIL_BIT only unblocks the boot-time wait in wifi_init_sta().
         */
        if (s_retry_count < WIFI_MAX_RETRIES) {
            s_retry_count++;
            ESP_LOGW(TAG, "Disconnected, retry %d/%d", s_retry_count, WIFI_MAX_RETRIES);
            esp_wifi_connect();
        } else {
            ESP_LOGW(TAG, "Still down after %d fast retries; retrying every %d s",
                     WIFI_MAX_RETRIES, WIFI_RECONNECT_DELAY_MS / 1000);
            xEventGroupSetBits(s_wifi_event_group, WIFI_FAIL_BIT);
            esp_timer_stop(s_reconnect_timer);
            esp_timer_start_once(s_reconnect_timer,
                                 (uint64_t)WIFI_RECONNECT_DELAY_MS * 1000);
        }
        return;
    }

    if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
        const ip_event_got_ip_t *event = (const ip_event_got_ip_t *)event_data;
        ESP_LOGI(TAG, "Got IP: " IPSTR, IP2STR(&event->ip_info.ip));
        s_retry_count = 0;
        xEventGroupClearBits(s_wifi_event_group, WIFI_FAIL_BIT);
        xEventGroupSetBits(s_wifi_event_group, WIFI_CONNECTED_BIT);
    }
}

esp_err_t wifi_init_sta(void)
{
    if (WIFI_SSID[0] == '\0') {
        ESP_LOGE(TAG, "WIFI_SSID is empty -- set it in main/app_config.h");
        return ESP_ERR_INVALID_STATE;
    }

    s_wifi_event_group = xEventGroupCreate();
    if (s_wifi_event_group == NULL) {
        return ESP_ERR_NO_MEM;
    }

    const esp_timer_create_args_t timer_args = {
        .callback = reconnect_timer_cb,
        .name = "wifi_reconnect",
    };
    ESP_ERROR_CHECK(esp_timer_create(&timer_args, &s_reconnect_timer));

    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);

    /* The TCP/IP stack and the default STA netif were never set up here, so
     * IP_EVENT_STA_GOT_IP could never fire and every connect timed out. */
    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_ERROR_CHECK(esp_event_handler_instance_register(WIFI_EVENT, ESP_EVENT_ANY_ID,
                                                        &wifi_event_handler, NULL, NULL));
    ESP_ERROR_CHECK(esp_event_handler_instance_register(IP_EVENT, IP_EVENT_STA_GOT_IP,
                                                        &wifi_event_handler, NULL, NULL));

    /* wifi_config_t.sta.ssid is a uint8_t array; it cannot be initialised
     * from a string literal in a designated initialiser. */
    wifi_config_t wifi_config = {
        .sta = {
            .threshold.authmode = WIFI_AUTH_WPA2_PSK,
            .sae_pwe_h2e = WPA3_SAE_PWE_BOTH,
        },
    };
    strlcpy((char *)wifi_config.sta.ssid, WIFI_SSID, sizeof(wifi_config.sta.ssid));
    strlcpy((char *)wifi_config.sta.password, WIFI_PASSWORD,
            sizeof(wifi_config.sta.password));

    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());

    /* Modem sleep adds hundreds of ms of latency per round trip, which is
     * enough to push a TLS handshake past its timeout on this board. */
    ESP_ERROR_CHECK(esp_wifi_set_ps(WIFI_PS_NONE));

    const EventBits_t bits = xEventGroupWaitBits(
        s_wifi_event_group,
        WIFI_CONNECTED_BIT | WIFI_FAIL_BIT,
        pdFALSE, pdFALSE,
        pdMS_TO_TICKS(WIFI_CONNECT_TIMEOUT_MS));

    if (bits & WIFI_CONNECTED_BIT) {
        ESP_LOGI(TAG, "Connected to SSID: %s", WIFI_SSID);
        return ESP_OK;
    }

    if (bits & WIFI_FAIL_BIT) {
        ESP_LOGE(TAG, "Failed to connect to SSID: %s", WIFI_SSID);
        return ESP_FAIL;
    }

    ESP_LOGE(TAG, "Timed out waiting for WiFi connection");
    return ESP_ERR_TIMEOUT;
}

bool wifi_is_connected(void)
{
    if (s_wifi_event_group == NULL) {
        return false;
    }
    return (xEventGroupGetBits(s_wifi_event_group) & WIFI_CONNECTED_BIT) != 0;
}

void wifi_get_status(char *buf, size_t len)
{
    if (buf == NULL || len == 0) {
        return;
    }

    if (!wifi_is_connected()) {
        snprintf(buf, len, "WiFi: not connected");
        return;
    }

    wifi_ap_record_t ap;
    if (esp_wifi_sta_get_ap_info(&ap) == ESP_OK) {
        snprintf(buf, len, "WiFi: %s (%d dBm)", (char *)ap.ssid, ap.rssi);
    } else {
        snprintf(buf, len, "WiFi: connected");
    }
}