/**
 * Block 3: CSV Writer für C-ITS Sniffer
 * 
 * Erstellt CSV-Dateien mit empfangenen C-ITS Nachrichten
 * Neue Datei alle 10 Minuten
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <time.h>

#include "sdkconfig.h"
#include "esp_err.h"
#include "esp_log.h"
#include "esp_vfs_fat.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"

static const char *TAG = "CSV_WRITER";

// CSV Datei Handle
static FILE *csv_file = NULL;
static char current_filename[64];
static time_t last_write_time = 0;
#define CSV_WRITE_INTERVAL_SEC (600)  // 10 Minuten

/**
 * C-ITS Message Header (BSI Format)
 */
typedef struct {
    uint32_t timestamp_sec;
    uint32_t timestamp_usec;
    uint16_t length;
    uint8_t sender_id[6];      // MAC Address
    uint8_t message_type;      // BSI Message Type
    uint8_t channel;          // Kanal
    int16_t rssi;             // Signal Stärke
} cits_message_t;

/**
 * CSV Header schreiben
 */
static void write_csv_header(FILE *fp)
{
    fprintf(fp, "timestamp_sec,timestamp_usec,length,sender_mac,message_type,channel,rssi\n");
}

/**
 * CSV Zeile schreiben
 */
static void write_csv_row(FILE *fp, cits_message_t *msg)
{
    char mac_str[18];
    snprintf(mac_str, sizeof(mac_str), "%02x:%02x:%02x:%02x:%02x:%02x",
             msg->sender_id[0], msg->sender_id[1], msg->sender_id[2],
             msg->sender_id[3], msg->sender_id[4], msg->sender_id[5]);
    
    fprintf(fp, "%u,%u,%u,%s,%u,%u,%d\n",
            msg->timestamp_sec, msg->timestamp_usec, msg->length,
            mac_str, msg->message_type, msg->channel, msg->rssi);
}

/**
 * Neue CSV-Datei erstellen
 */
static esp_err_t create_new_csv_file(void)
{
    time_t now;
    struct tm *tm_info;
    
    time(&now);
    tm_info = localtime(&now);
    
    // Dateinamen mit Zeitstempel
    snprintf(current_filename, sizeof(current_filename), 
             "/data/cits_%04d%02d%02d_%02d%02d%02d.csv",
             tm_info->tm_year + 1900, tm_info->tm_mon + 1, tm_info->tm_mday,
             tm_info->tm_hour, tm_info->tm_min, tm_info->tm_sec);
    
    if (csv_file != NULL) {
        fclose(csv_file);
    }
    
    csv_file = fopen(current_filename, "w");
    if (csv_file == NULL) {
        ESP_LOGE(TAG, "Failed to create CSV file: %s", current_filename);
        return ESP_FAIL;
    }
    
    write_csv_header(csv_file);
    fflush(csv_file);
    
    ESP_LOGI(TAG, "Created new CSV file: %s", current_filename);
    return ESP_OK;
}

/**
 * Prüfen ob neue Datei nötig (10 Minuten Intervall)
 */
static void check_new_csv_file(void)
{
    time_t now;
    time(&now);
    
    if (difftime(now, last_write_time) >= CSV_WRITE_INTERVAL_SEC) {
        create_new_csv_file();
        last_write_time = now;
    }
}

/**
 * C-ITS Nachricht speichern
 * 
 * @param msg Nachricht Daten
 */
void csv_store_cits_message(cits_message_t *msg)
{
    if (csv_file == NULL) {
        create_new_csv_file();
        if (csv_file == NULL) {
            return;
        }
    }
    
    check_new_csv_file();
    write_csv_row(csv_file, msg);
    fflush(csv_file);
}

/**
 * CSV System initialisieren
 */
esp_err_t csv_writer_init(void)
{
    // SPI Flash Filesystem mounten
    static wl_handle_t wl_handle;
    const esp_vfs_fat_mount_config_t mount_config = {
        .max_files = 4,
        .format_if_mount_failed = true
    };
    
    esp_err_t ret = esp_vfs_fat_spiflash_mount_rw_wl("/data", "storage", &mount_config, &wl_handle);
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "Failed to mount FATFS (%s)", esp_err_to_name(ret));
        return ret;
    }
    
    // Erste CSV Datei erstellen
    return create_new_csv_file();
}

/**
 * CSV System beenden
 */
void csv_writer_deinit(void)
{
    if (csv_file != NULL) {
        fclose(csv_file);
        csv_file = NULL;
    }
}