// utun.c - Main application for utun VPN tunnel
#define _DEFAULT_SOURCE
#define _POSIX_C_SOURCE 200809L
#include "config_parser.h"
#include "etcp_connections.h"
#include "tun_if.h"
#include "secure_channel.h"
#include "routing.h"
#include "utun_instance.h"
#include "u_async.h"
#include "debug_config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <signal.h>

#include <getopt.h>
#include <arpa/inet.h>
/*

Архитектура:
main -> init utun instnaces -> mainloop()

utun instances: можно stop() - он ывзывает закрытие всех etcp (etcp_close) которые вызовут закрытие подключений), вызывает закрытие всех etcp сокетов



*/



// Global wakeup pipe write fd for signal handler
static int g_wakeup_pipe_write_fd = -1;

#define DEFAULT_CONFIG "utun.conf"
#define DEFAULT_PIDFILE "/var/run/utun.pid"

// Command line arguments
typedef struct {
    char *config_file;
    char *pid_file;
    char *log_file;
    char *debug_config;
    int foreground;
    int help;
} cmd_args_t;

// Global state





// Parse subnet string
static int parse_subnet(const char *subnet_str, uint32_t *network, uint8_t *prefix_length) {
    if (!subnet_str || !network || !prefix_length) return -1;
    char ip[64];
    int prefix;
    if (sscanf(subnet_str, "%[^/]/%d", ip, &prefix) != 2) return -1;
    if (prefix < 0 || prefix > 32) return -1;
    struct in_addr addr;
    if (inet_pton(AF_INET, ip, &addr) != 1) return -1;
    *network = addr.s_addr;
    *prefix_length = (uint8_t)prefix;
    return 0;
}

// Extract destination IPv4 address from packet
static uint32_t get_dest_ip(const uint8_t *packet, size_t len) {
    if (len < 20) return 0; // Minimum IPv4 header size
    // Check IP version (first nibble)
    uint8_t version = (packet[0] >> 4) & 0x0F;
    if (version != 4) return 0;
    // Destination IP is at offset 16
    uint32_t dest_ip;
    memcpy(&dest_ip, packet + 16, 4);
    return dest_ip;
}


// Parse command line arguments
static void parse_args(int argc, char *argv[], cmd_args_t *args) {
    memset(args, 0, sizeof(*args));
    args->config_file = DEFAULT_CONFIG;
    args->pid_file = DEFAULT_PIDFILE;
    args->log_file = NULL;
    args->debug_config = NULL;
    args->foreground = 0;
    args->help = 0;
    
    static struct option long_options[] = {
        {"config", required_argument, 0, 'c'},
        {"pidfile", required_argument, 0, 'p'},
        {"log", required_argument, 0, 'l'},
        {"debug", required_argument, 0, 'd'},
        {"foreground", no_argument, 0, 'f'},
        {"help", no_argument, 0, 'h'},
        {0, 0, 0, 0}
    };
    
    int opt;
    int option_index = 0;
    
    while ((opt = getopt_long(argc, argv, "c:p:l:d:fh", 
                              long_options, &option_index)) != -1) {
        switch (opt) {
            case 'c':
                args->config_file = optarg;
                break;
            case 'p':
                args->pid_file = optarg;
                break;
            case 'l':
                args->log_file = optarg;
                break;
            case 'f':
                args->foreground = 1;
                break;
            case 'd':
                args->debug_config = optarg;
                break;
            case 'h':
                args->help = 1;
                break;
            default:
                DEBUG_ERROR(DEBUG_CATEGORY_CONFIG, "Unknown option: %c", opt);
                exit(1);
        }
    }
}

// Print usage
static void print_usage(const char *progname) {
    printf("Usage: %s [OPTIONS]\n", progname);
    printf("Secure VPN tunnel over UDP with TUN interface\n\n");
    printf("Options:\n");
    printf("  -c, --config FILE    Configuration file (default: %s)\n", DEFAULT_CONFIG);
    printf("  -p, --pidfile FILE   PID file (default: %s)\n", DEFAULT_PIDFILE);
    printf("  -l, --log FILE       Log file (default: stderr)\n");
    printf("  -d, --debug CONFIG   Debug configuration (e.g., \"etcp:debug,routing:info\")\n");
    printf("  -f, --foreground     Run in foreground (don't daemonize)\n");
    printf("  -h, --help           Show this help\n");
    printf("\nExamples:\n");
    printf("  %s -c myconfig.conf\n", progname);
    printf("  %s --config server.conf --pidfile /var/run/utun.pid\n", progname);
}

// Write PID file
static int write_pidfile(const char *pidfile) {
    if (!pidfile) return -1;
    
    FILE *fp = fopen(pidfile, "w");
    if (!fp) {
        perror("fopen pidfile");
        return -1;
    }
    
    fprintf(fp, "%d\n", getpid());
    fclose(fp);
    return 0;
}

// Remove PID file
static void remove_pidfile(const char *pidfile) {
    if (pidfile) {
        unlink(pidfile);
    }
}

// Daemonize process
static int daemonize(void) {
    pid_t pid = fork();
    if (pid < 0) {
        perror("fork");
        return -1;
    }
    
    if (pid > 0) {
        // Parent exits
        exit(0);
    }
    
    // Child becomes session leader
    if (setsid() < 0) {
        perror("setsid");
        return -1;
    }
    
    // Close standard file descriptors
    close(STDIN_FILENO);
    close(STDOUT_FILENO);
    close(STDERR_FILENO);
    
    // Redirect to /dev/null
    int fd = open("/dev/null", O_RDWR);
    if (fd >= 0) {
        dup2(fd, STDIN_FILENO);
        dup2(fd, STDOUT_FILENO);
        dup2(fd, STDERR_FILENO);
        if (fd > 2) close(fd);
    }
    
    return 0;
}

// Open log file
static FILE* open_logfile(const char *logfile) {
    if (!logfile) return stderr;
    
    FILE *fp = fopen(logfile, "a");
    if (!fp) {
        perror("fopen logfile");
        return stderr;
    }
    
    // Set line buffering
    setlinebuf(fp);
    return fp;
}


// Main function

static volatile sig_atomic_t g_running = 1;
struct UASYNC* main_ua = NULL;

static void signal_handler(int sig) {
    (void)sig;
    g_running = 0;
    if (main_ua) {
        uasync_wakeup(main_ua);
    }
}

int main(int argc, char *argv[]) {
    cmd_args_t args;
    parse_args(argc, argv, &args);
    
    if (args.help) {
        print_usage(argv[0]);
        return 0;
    }
    
    // Initialize global debug system early if configured from command line
    if (args.debug_config) {
        debug_config_init();
        if (debug_parse_config(args.debug_config) < 0) {
            DEBUG_ERROR(DEBUG_CATEGORY_CONFIG, "Invalid debug configuration: %s", args.debug_config);
            return 1;
        }
    }

    // Create uasync instance
    struct UASYNC* ua = uasync_create();
    main_ua=ua;
    if (!ua) {
        DEBUG_ERROR(DEBUG_CATEGORY_MEMORY, "Failed to create uasync instance");
        return 1;
    }

    // Create and initialize instance
    struct UTUN_INSTANCE *instance = utun_instance_create(ua, args.config_file, args.log_file);
    if (!instance) {
        DEBUG_ERROR(DEBUG_CATEGORY_MEMORY, "Failed to create UTUN instance");
        return 1;
    }
    
    // Print config for debugging
    if (args.foreground) {
        print_config(instance->config);
    }
    
    // Initialize all components (TUN, routing, connections)
    if (utun_instance_init(instance) < 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_MEMORY, "Failed to initialize instance");
        utun_instance_destroy(instance);
        return 1;
    }
    
    // Register sockets with uasync
    if (utun_instance_register_sockets(instance) < 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_MEMORY, "Failed to register sockets");
        utun_instance_destroy(instance);
        return 1;
    }
    
    // Setup signal handlers
    signal(SIGINT, signal_handler);
    signal(SIGTERM, signal_handler);
    signal(SIGHUP, signal_handler);
    
    // Daemonize if not in foreground
    if (!args.foreground) {
        if (daemonize() < 0) {
            DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "Failed to daemonize");
            utun_instance_destroy(instance);
            return 1;
        }
    }
    
    // Write PID file
    if (write_pidfile(args.pid_file) < 0) {
        utun_instance_destroy(instance);
        return 1;
    }

    while (instance->running) uasync_poll(ua, 100);

    // Cleanup
    DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "Shutdown");

    utun_instance_unregister_sockets(instance);
    utun_instance_destroy(instance);
    remove_pidfile(args.pid_file);
    
    return 0;
}