/**
 * @file main.c
 * @brief NexusGuard Embedded Agent - Main Entry Point
 * 
 * ESP32-based WireGuard agent for IoT/edge devices.
 * Connects to NexusGuard Server Core via HTTP provisioning + heartbeat.
 * 
 * @version 1.0.0
 * @date 2026-06-26
 */

#include <stdio.h>
#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 "esp_ota_ops.h"
#include "nvs_flash.h"

/* Agent modules */
#include "config.h"
#include "wifi.h"
#include "provision.h"
#include "heartbeat.h"
#include "tunnel.h"
#include "crypto.h"

static const char *TAG = "nexusguard";

/* Event bits */
#define WIFI_CONNECTED_BIT    BIT0
#define PROVISIONED_BIT       BIT1
#define TUNNEL_UP_BIT         BIT2
#define HEARTBEAT_OK_BIT      BIT3

static EventGroupHandle_t s_event_group;

/* Agent configuration */
static wg_config_t s_config;
static device_state_t s_state = STATE_BOOT;

/**
 * @brief Get hardware ID from ESP32 eFuse MAC
 */
static void get_hardware_id(char *hwid, size_t len)
{
    uint8_t mac[6];
    esp_efuse_mac_get_default(mac);
    snprintf(hwid, len, "%02x%02x%02x%02x%02x%02x",
             mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
}

/**
 * @brief WiFi event handler
 */
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();
    } else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
        ESP_LOGW(TAG, "WiFi disconnected, reconnecting...");
        esp_wifi_connect();
        xEventGroupClearBits(s_event_group, WIFI_CONNECTED_BIT);
    } 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));
        xEventGroupSetBits(s_event_group, WIFI_CONNECTED_BIT);
    }
}

/**
 * @brief Initialize WiFi
 */
static esp_err_t init_wifi(const char *ssid, const char *password)
{
    ESP_LOGI(TAG, "Initializing WiFi...");
    
    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,
                    &wifi_event_handler, NULL, &instance_any_id));
    ESP_ERROR_CHECK(esp_event_handler_instance_register(IP_EVENT, IP_EVENT_STA_GOT_IP,
                    &wifi_event_handler, NULL, &instance_got_ip));
    
    wifi_config_t wifi_config = {
        .sta = {
            .threshold.authmode = WIFI_AUTH_WPA2_PSK,
        },
    };
    
    strncpy((char *)wifi_config.sta.ssid, ssid, sizeof(wifi_config.sta.ssid) - 1);
    strncpy((char *)wifi_config.sta.password, password, sizeof(wifi_config.sta.password) - 1);
    
    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 initialized, connecting to %s...", ssid);
    
    return ESP_OK;
}

/**
 * @brief Main entry point
 */
void app_main(void)
{
    ESP_LOGI(TAG, "=== NexusGuard Embedded Agent v%s ===", CONFIG_NEXUS_AGENT_VERSION);
    ESP_LOGI(TAG, "Hardware: %s", CONFIG_IDF_TARGET);
    ESP_LOGI(TAG, "IDF Version: %s", esp_get_idf_version());
    ESP_LOGI(TAG, "Server: %s", CONFIG_NEXUS_SERVER_URL);
    
    /* Initialize NVS */
    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);
    
    /* Create event group */
    s_event_group = xEventGroupCreate();
    
    /* Get hardware ID */
    char hwid[32];
    get_hardware_id(hwid, sizeof(hwid));
    ESP_LOGI(TAG, "Hardware ID: %s", hwid);
    
    /* Initialize modules */
    ESP_ERROR_CHECK(config_init());
    ESP_ERROR_CHECK(crypto_init());
    
    /* Load saved config */
    ret = config_load(&s_config);
    if (ret == ESP_OK && config_is_valid(&s_config)) {
        ESP_LOGI(TAG, "Loaded saved config for device: %s", s_config.device_id);
        xEventGroupSetBits(s_event_group, PROVISIONED_BIT);
    } else {
        ESP_LOGW(TAG, "No valid config found, will provision...");
    }
    
    /* Initialize WiFi */
    const char *ssid = CONFIG_NEXUS_WIFI_SSID;
    const char *password = CONFIG_NEXUS_WIFI_PASSWORD;
    
    if (strlen(ssid) == 0) {
        ESP_LOGE(TAG, "WiFi SSID not configured! Set via menuconfig or NVS.");
        ESP_LOGE(TAG, "Run: idf.py menuconfig → Component config → NexusGuard Agent");
        return;
    }
    
    init_wifi(ssid, password);
    
    /* Wait for WiFi connection */
    ESP_LOGI(TAG, "Waiting for WiFi connection...");
    xEventGroupWaitBits(s_event_group, WIFI_CONNECTED_BIT, pdFALSE, pdTRUE, 
                        pdMS_TO_TICKS(30000));
    
    if (!(xEventGroupGetBits(s_event_group) & WIFI_CONNECTED_BIT)) {
        ESP_LOGE(TAG, "WiFi connection failed, restarting...");
        esp_restart();
    }
    
    ESP_LOGI(TAG, "WiFi connected!");
    
    /* Provision if needed */
    if (!(xEventGroupGetBits(s_event_group) & PROVISIONED_BIT)) {
        ESP_LOGI(TAG, "Provisioning device...");
        s_state = STATE_PROVISIONING;
        
        const char *server_url = CONFIG_NEXUS_SERVER_URL;
        const char *token = CONFIG_NEXUS_REG_TOKEN;
        
        if (strlen(server_url) == 0 || strlen(token) == 0) {
            ESP_LOGE(TAG, "Server URL or registration token not configured!");
            ESP_LOGE(TAG, "Run: idf.py menuconfig → Component config → NexusGuard Agent");
            return;
        }
        
        ret = provision_device(server_url, token, hwid, &s_config);
        if (ret != ESP_OK) {
            ESP_LOGE(TAG, "Provisioning failed: %s", esp_err_to_name(ret));
            ESP_LOGE(TAG, "Restarting in 5 seconds...");
            vTaskDelay(pdMS_TO_TICKS(5000));
            esp_restart();
        }
        
        ESP_LOGI(TAG, "Provisioning successful!");
        xEventGroupSetBits(s_event_group, PROVISIONED_BIT);
    }
    
    /* Initialize WireGuard tunnel */
    ESP_LOGI(TAG, "Initializing WireGuard tunnel...");
    s_state = STATE_TUNNEL_UP;
    
    ret = tunnel_init(&s_config);
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "Tunnel initialization failed: %s", esp_err_to_name(ret));
        ESP_LOGE(TAG, "Restarting in 5 seconds...");
        vTaskDelay(pdMS_TO_TICKS(5000));
        esp_restart();
    }
    
    ESP_LOGI(TAG, "WireGuard tunnel initialized!");
    xEventGroupSetBits(s_event_group, TUNNEL_UP_BIT);
    
    /* Main heartbeat loop */
    ESP_LOGI(TAG, "Starting heartbeat loop...");
    s_state = STATE_HEARTBEAT;
    
    while (1) {
        /* Wait for 30 seconds */
        vTaskDelay(pdMS_TO_TICKS(30000));
        
        /* Check WiFi */
        if (!(xEventGroupGetBits(s_event_group) & WIFI_CONNECTED_BIT)) {
            ESP_LOGW(TAG, "WiFi not connected, skipping heartbeat");
            continue;
        }
        
        /* Send heartbeat */
        bool tunnel_up = tunnel_is_up();
        int64_t last_hs = tunnel_get_last_handshake();
        
        ret = heartbeat_send(&s_config, "connected", tunnel_up, last_hs);
        if (ret != ESP_OK) {
            ESP_LOGW(TAG, "Heartbeat failed: %s", esp_err_to_name(ret));
            continue;
        }
        
        ESP_LOGI(TAG, "Heartbeat sent (tunnel=%s)", tunnel_up ? "up" : "down");
        
        /* Check for config changes */
        // TODO: Compare config hash and rebuild tunnel if needed
    }
}