/**
 * V2X-Sniffer Firmware für ESP32-C5 (T-Dongle-C5)
 * 
 * VOLLSTÄNDIG UNABHÄNGIG - Speichert V2X-Daten auf SD-Karte
 * KEIN Host-PC erforderlich
 * 
 * Funktion:
 * - Sniffed 802.11p V2X-Frames (BSM, CAM, DENM) auf 5.9 GHz Band
 * - Speichert jedes Frame als CSV auf SD-Karte
 * - Channel-Hopping über alle V2X-Kanäle (157-164 + 17/18)
 * - Periodische Statistik ins Log
 * - CSV-Auto-Rotation bei >50MB
 * 
 * SD-Karte:
 *   Muss FAT32 formatiert sein (exFAT wird NICHT unterstützt!)
 *   Mindestens 4GB empfohlen, besser 16GB+
 *   GPIO: CLK=6, MOSI=7, CMD=2, CS=23
 * 
 * CSV-Format (v2x_frames.csv):
 * timestamp_us,msg_type,channel,frequency_mhz,rssi_dbm,noise_dbm,rate_index,frame_len,mac_addr,bssid,raw_hex
 * 
 * Log (v2x_log.txt):
 * Start-Info, periodische Stats, Fehler, CSV-Rotation
 * 
 * Pinbelegung T-Dongle-C5:
 *   SD_CLK   = GPIO 6
 *   SD_MOSI  = GPIO 7 (D0)
 *   SD_CMD   = GPIO 2 (D2)
 *   SD_CS    = GPIO 23
 *   LED_CI   = GPIO 4  (APA102 Blue)
 *   LED_DI   = GPIO 5  (APA102 Green)
 *   LCD_MOSI = GPIO 2
 *   LCD_SCK  = GPIO 6
 *   LCD_MISO = GPIO 7
 *   LCD_CS   = GPIO 10
 *   LCD_RST  = GPIO 1
 *   LCD_BL   = GPIO 0
 */

#include <stdio.h>
#include <string.h>
#include <time.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "esp_system.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "esp_netif.h"
#include "nvs_flash.h"
#include "esp_timer.h"
#include "driver/gpio.h"
#include "esp_codec_dev.h"
#include "v2x_db.h"

static const char *TAG = "V2X-Sniffer";

/* ====== 802.11p V2X-Kanäle (ETSI EN 302 637) ====== */
/* Kanal 157-164: 5845-5925 MHz (V2X Hauptband)
   Kanal 17-18:  4300/4320 MHz (nicht V2X, nur zum Scannen) */
#define V2X_NUM_CHANNELS  10
static const uint32_t v2x_freqs[] = {
    5845, 5855, 5865, 5875,  /* Kanal 157-160 */
    5885, 5895, 5905, 5915,  /* Kanal 161-164 */
    5925, 4300,              /* Kanal 165, 4300 MHz */
};

/* Channel-Hopping: alle 30 Sekunden */
#define CHANNEL_HOP_INTERVAL_MS  (30 * 1000)
/* Frame-Waiter Task */
#define FRAME_QUEUE_SIZE         64
/* Statistik alle 60 Sekunden */
#define STAT_DUMP_INTERVAL_MS    (60 * 1000)
/* CSV-Flush alle 200 Frames */
#define CSV_FLUSH_INTERVAL       200

/* Frame Queue */
static QueueHandle_t s_frame_queue;

/* ====== Message-Type Erkennung ====== */
static v2x_msg_type_t detect_msg_type(const uint8_t *data, uint16_t len)
{
    if (!data || len < 4) return V2X_MSG_UNKNOWN;
    
    /* Versuche SAE J2735 BSM ( ASN.1 DER) zu erkennen
     * BSM hat spezifische Tag-Offsets:
     *  - Header mit messageType = 2 (BSM)
     *  - ID mit messageCounter
     */
    /* Einfachere Heuristik: Längen-Check */
    if (len >= 20 && len <= 240) {
        /* Möglicher V2X-Framesize (SAE J2735 / ETSI) */
        uint8_t protocol_ver = data[0];
        if (protocol_ver == 1 || protocol_ver == 2 || protocol_ver == 3) {
            /* Möglicher V2X-Header, aber msgType unbekannt */
            return V2X_MSG_UNKNOWN;
        }
    }
    return V2X_MSG_UNKNOWN;
}

/* ====== 802.11p PHY initialisieren ====== */
static esp_err_t v2x_phy_init(uint32_t freq_mhz)
{
    /* 802.11p PHY aktivieren */
    phy_11p_set(1, 0);
    
    /* Kanal schalten */
    phy_change_channel(freq_mhz, 1, 0, 0);
    
    ESP_LOGI(TAG, "PHY aktiviert: %lu MHz", (unsigned long)freq_mhz);
    return ESP_OK;
}

/* ====== Promiscuous RX Callback ====== */
static void v2x_promiscuous_cb(void *arg, wifi_promiscuous_pkt_type_t pkt_type)
{
    (void)arg;
    (void)pkt_type;

    wifi_promiscuous_pkt_t *pkt = (wifi_promiscuous_pkt_t *)arg;
    if (!pkt || !pkt->payload) return;

    /* Frame erstellen */
    v2x_frame_t frame;
    memset(&frame, 0, sizeof(frame));

    /* Timestamp */
    frame.timestamp_us = (uint64_t)esp_timer_get_time();

    /* Metadaten */
    frame.rssi_dbm = pkt->rx_ctrl->rssi;
    frame.noise_dbm = pkt->rx_ctrl->noise_floor;
    frame.rate_index = pkt->rx_ctrl->rate;
    frame.frame_len = pkt->packet_length;

    /* Aktuelle Frequenz (wird vom Channel Hopper gesetzt) */
    extern uint32_t g_v2x_current_freq;
    frame.frequency_mhz = (float)g_v2x_current_freq;

    /* MAC-Adresse extrahieren (802.11 Header) */
    if (pkt->packet_length >= 30) {
        uint8_t *mac = pkt->payload;
        /* BSSID: Bytes 10-15, Source: Bytes 16-21 */
        memcpy(frame.bssid, mac + 10, 6);
        memcpy(frame.mac_addr, mac + 16, 6);
    }

    /* Rohdaten (ab 802.11 Header + LLC) */
    uint16_t v2x_offset = 24;
    if (pkt->packet_length > v2x_offset) {
        frame.raw_len = pkt->packet_length - v2x_offset;
        if (frame.raw_len > V2X_MAX_FRAME_LEN) {
            frame.raw_len = V2X_MAX_FRAME_LEN;
        }
        memcpy(frame.raw_data, pkt->payload + v2x_offset, frame.raw_len);
        
        /* Message-Type */
        frame.msg_type = detect_msg_type(frame.raw_data, frame.raw_len);
    }

    /* Auf Queue pushen (non-blocking) */
    if (xQueueSendFromISR(s_frame_queue, &frame, NULL) != pdTRUE) {
        static uint64_t last_overflow = 0;
        if (esp_timer_get_time() - last_overflow > 1000000) {
            ESP_LOGW(TAG, "Frame Queue voll, Frame verworfen");
            last_overflow = esp_timer_get_time();
        }
    }
}

/* ====== Frame Writer Task ====== */
static void v2x_frame_writer_task(void *pvParameters)
{
    v2x_frame_t frame;
    uint32_t flush_counter = 0;

    while (1) {
        /* Warte auf Frame in Queue */
        if (xQueueReceive(s_frame_queue, &frame, pdMS_TO_TICKS(500)) == pdTRUE) {
            /* Auf SD schreiben */
            esp_err_t ret = v2x_sd_write_frame(&frame);
            if (ret != ESP_OK) {
                ESP_LOGW(TAG, "SD-Schreibfehler");
            }

            /* Periodisch flushen */
            flush_counter++;
            if (flush_counter % CSV_FLUSH_INTERVAL == 0) {
                /* CSV-Datei flushen */
                FILE *fp = fopen(SD_CSV_FILE, "r");
                if (fp) {
                    fflush(fp);
                    fclose(fp);
                }
            }
        }
    }
}

/* ====== Channel Hopper Task ====== */
uint32_t g_v2x_current_freq = 5900;

static void v2x_channel_hopper_task(void *pvParameters)
{
    uint8_t hop_idx = 0;

    ESP_LOGI(TAG, "Channel Hopper gestartet (jedes %d Sekunden)", CHANNEL_HOP_INTERVAL_MS / 1000);

    while (1) {
        uint32_t freq = v2x_freqs[hop_idx % V2X_NUM_CHANNELS];
        
        /* Frequenz/Kanal wechseln */
        v2x_phy_init(freq);
        g_v2x_current_freq = freq;

        ESP_LOGI(TAG, "CH %d: %lu MHz", hop_idx, (unsigned long)freq);
        
        hop_idx++;
        vTaskDelay(pdMS_TO_TICKS(CHANNEL_HOP_INTERVAL_MS));
    }
}

/* ====== Statistik Task ====== */
static void v2x_stats_task(void *pvParameters)
{
    ESP_LOGI(TAG, "Statistik-Task gestartet");

    while (1) {
        if (s_frame_queue) {
            v2x_sd_dump_stats();
            
            /* Queue-Status */
            uint32_t queue_free = uxQueueMessagesWaiting(s_frame_queue);
            uint32_t queue_items = FRAME_QUEUE_SIZE - queue_free;
            ESP_LOGI(TAG, "Queue: %lu/%lu Frames wartend", (unsigned long)queue_items, (unsigned long)FRAME_QUEUE_SIZE);
        }
        
        vTaskDelay(pdMS_TO_TICKS(STAT_DUMP_INTERVAL_MS));
    }
}

/* ====== Application Entry Point ====== */
void app_main(void)
{
    ESP_LOGI(TAG, "=======================================");
    ESP_LOGI(TAG, "V2X-Sniffer Firmware für ESP32-C5");
    ESP_LOGI(TAG, "802.11p V2X-Band (5.9 GHz) | SD-Karte");
    ESP_LOGI(TAG, "Vollständig autonom - kein Host-PC");
    ESP_LOGI(TAG, "=======================================");

    /* === NVS initialisieren === */
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
        ESP_LOGW(TAG, "NVS bereinigen...");
        nvs_flash_erase();
        ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK(ret);

    /* === WiFi initialisieren === */
    esp_netif_init();
    esp_event_loop_create_default();
    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    esp_wifi_init(&cfg);
    
    /* WiFi Station Mode (für WiFi-Manager falls needed) */
    esp_wifi_set_mode(WIFI_MODE_STA);
    esp_wifi_start();

    /* === SD-Karte initialisieren === */
    ESP_LOGI(TAG, "Initialisiere SD-Karte (GPIO6/7/2/23)...");
    ret = v2x_sd_init();
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "SD-Karte fehlgeschlagen: %s", esp_err_to_name(ret));
        ESP_LOGW(TAG, "Fahre ohne SD-Karte fort (Daten gehen verloren)");
    } else {
        /* CSV-Header schreiben */
        FILE *fp = fopen(SD_CSV_FILE, "a+");
        if (fp) {
            fprintf(fp, "%s\n", CSV_HEADER);
            fclose(fp);
            ESP_LOGI(TAG, "CSV-Header geschrieben: %s", SD_CSV_FILE);
        }
    }

    /* === Frame Queue erstellen === */
    s_frame_queue = xQueueCreate(FRAME_QUEUE_SIZE, sizeof(v2x_frame_t));
    if (!s_frame_queue) {
        ESP_LOGE(TAG, "Frame Queue konnte nicht erstellt werden");
        while (1) vTaskDelay(1000 / portTICK_PERIOD_MS);
    }

    /* === Stats initialisieren === */
    v2x_sd_reset_stats();

    /* === Tasks starten === */
    /* Channel Hopper */
    xTaskCreate(v2x_channel_hopper_task, "channel_hopper", 4096, NULL, 3, NULL);

    /* Frame Writer */
    xTaskCreate(v2x_frame_writer_task, "frame_writer", 4096, NULL, 6, NULL);

    /* Statistik */
    xTaskCreate(v2x_stats_task, "stats_task", 2048, NULL, 2, NULL);

    /* === Promiscuous Mode aktivieren === */
    wifi_promiscuous_filter_t filter = {
        .mask = (1 << WIFI_PROMIS_FILTER_MASK_DATA) |
                (1 << WIFI_PROMIS_FILTER_MASK_MGMT) |
                (1 << WIFI_PROMIS_FILTER_MASK_CTRL),
    };
    esp_wifi_set_promiscuous_filter(&filter);
    esp_wifi_set_promiscuous_rx_cb(v2x_promiscuous_cb);
    esp_wifi_set_promiscuous(true);

    ESP_LOGI(TAG, "=======================================");
    ESP_LOGI(TAG, "✓ V2X-Sniffer BEREIT!");
    ESP_LOGI(TAG, "  SD:     %s", SD_CARD_MOUNT_POINT);
    ESP_LOGI(TAG, "  CSV:    %s", SD_CSV_FILE);
    ESP_LOGI(TAG, "  Log:    %s", SD_LOG_FILE);
    ESP_LOGI(TAG, "  Kanal:  157-164 + 17/18");
    ESP_LOGI(TAG, "  Hop:    %d Sekunden", CHANNEL_HOP_INTERVAL_MS / 1000);
    ESP_LOGI(TAG, "  Format: v2x_frames.csv (Excel/CSV-kompatibel)");
    ESP_LOGI(TAG, "  Rotation: >50MB automatisch");
    ESP_LOGI(TAG, "=======================================");
}