/*
 * xl2tpd-control - the xl2tpd control utility
 *
 * Copyright (C) 2011 Alexander Dorokhov <alex.dorokhov@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (see the file LICENSE); if not, see
 * https://www.gnu.org/licenses/, or contact Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 ****************************************************************
 */
 
#define _GNU_SOURCE

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>

#include "l2tp.h"

/* Paul: Alex: can we change this to use stdout, and let applications using
 * xl2tpd-control capture the output, instead of creating tmp files?
 */
/* result filename format including absolute path and formatting %i for pid */
#define RESULT_FILENAME_FORMAT "/var/run/xl2tpd/xl2tpd-control-%i.out"

#define ERROR_LEVEL 1
#define DEBUG_LEVEL 2

#define TUNNEL_REQUIRED 1
#define TUNNEL_NOT_REQUIRED 0
#define TIMEOUT 1000000  //timeout is 1s

char result_filename[128];
int result_fd = -1;

int log_level = ERROR_LEVEL;

void print_error (int level, const char *fmt, ...);
int read_result(int result_fd, char* buf, ssize_t size);

/* Definition of a command */
struct command_t
{
    char *name;
    int (*handler) (FILE*, char* tunnel, int optc, char *optv[]);
    int requires_tunnel;
};

int command_add_lac       (FILE*, char* tunnel, int optc, char *optv[]);
int command_connect_lac   (FILE*, char* tunnel, int optc, char *optv[]);
int command_disconnect_lac(FILE*, char* tunnel, int optc, char *optv[]);
int command_status_lac    (FILE*, char* tunnel, int optc, char *optv[]);
int command_remove_lac    (FILE*, char* tunnel, int optc, char *optv[]);
int command_available     (FILE*, char* tunnel, int optc, char *optv[]);
int command_add_lns       (FILE*, char* tunnel, int optc, char *optv[]);
int command_status_lns    (FILE*, char* tunnel, int optc, char *optv[]);
int command_remove_lns    (FILE*, char* tunnel, int optc, char *optv[]);

struct command_t commands[] = {
    {"add-lac",       &command_add_lac,       TUNNEL_REQUIRED},
    {"connect-lac",   &command_connect_lac,   TUNNEL_REQUIRED},
    {"disconnect-lac",&command_disconnect_lac,TUNNEL_REQUIRED},
    {"status-lac",    &command_status_lac,    TUNNEL_REQUIRED},
    {"remove-lac",    &command_remove_lac,    TUNNEL_REQUIRED},
    {"available",     &command_available,     TUNNEL_NOT_REQUIRED},
    {"add-lns",       &command_add_lns,       TUNNEL_REQUIRED},
    {"status-lns",    &command_status_lns,    TUNNEL_REQUIRED},
    {"remove-lns",    &command_remove_lns,    TUNNEL_REQUIRED}
};

void usage()
{
    printf ("Usage: xl2tpd-control [-c <PATH>] <COMMAND> <TUNNEL_NAME> [<OPTIONS>]\n\n"
            "       -c  set xl2tpd control file\n"
            "       -d  enable debugging mode\n"
            "--version  show version\n"
            "   --help  show this help message\n\n"
            "List of supported commands:\n"
            "add-lac, status-lac, remove-lac, connect-lac, disconnect-lac\n"
            "add-lns, status-lns, remove-lns, available\n\n"
            "See xl2tpd-control(8) man page for more details.\n");
}

void cleanup(void)
{
    /* cleaning up */
    unlink (result_filename);
    if (result_fd >= 0)
        close (result_fd);
}

int main (int argc, char *argv[])
{
    char* control_filename = NULL;
    char* tunnel_name = NULL;
    struct command_t* command = NULL;    
    int i; /* argv iterator */

    if (argv[1] && !strncmp (argv[1], "--help", 6)) {
        usage();
        return 0;
    }

    if (argv[1] && !strncmp (argv[1], "--version", 9)) {
        printf ("Version: %s\n", SERVER_VERSION);
        return 0;
    }

    /* parse global options */
    for (i = 1; i < argc; i++) {
        if (!strncmp (argv[i], "-c", 2)) {
            control_filename = argv[++i];
        } else if (!strncmp (argv[i], "-d", 2)) {
            log_level = DEBUG_LEVEL;
        } else {
            break;
        }
    }

    if (i >= argc) {
        print_error (ERROR_LEVEL, "error: command not specified\n");
        usage();
        return -1;
    }

    if (!control_filename) {
        control_filename = strdup (CONTROL_PIPE);
    }

    /* parse command name */
    for (command = commands; command->name; command++)
    {
        if (!strcasecmp (argv[i], command->name))
        {
            i++;
            break;
        }
    }
    
    if (!command->name) {
        print_error (ERROR_LEVEL, "error: no such command\n");
        free(control_filename);
        usage();
        return -1;
    }
    
    /* get tunnel name */
    if(command->requires_tunnel){
        if (i >= argc) {
            print_error (ERROR_LEVEL, "error: tunnel name not specified\n");
            usage();
            free(control_filename);
            return -1;
        }
        tunnel_name = argv[i++];    
        /* check tunnel name for whitespaces */
        if (strstr (tunnel_name, " ")) {
            print_error (ERROR_LEVEL, "error: tunnel name shouldn't include spaces\n");
            usage();
            free(control_filename);
            return -1;
        }
    }
    
    char buf[CONTROL_PIPE_MESSAGE_SIZE] = "";
    FILE* mesf = fmemopen (buf, CONTROL_PIPE_MESSAGE_SIZE, "w");

    /* create result pipe for reading */
    snprintf (result_filename, 128, RESULT_FILENAME_FORMAT, getpid());
    unlink (result_filename);
    mkfifo (result_filename, 0600);
    atexit(cleanup);

    result_fd = open (result_filename, O_RDONLY | O_NONBLOCK, 0600);
    if (result_fd < 0)
    {
        print_error (ERROR_LEVEL,
            "error: unable to open %s for reading.\n", result_filename);
        return -2;
    }
   
    /* turn off O_NONBLOCK */
    if (fcntl (result_fd, F_SETFL, O_RDONLY) == -1) {
        print_error (ERROR_LEVEL,
            "Can not turn off nonblocking mode for result_fd: %s\n",
            strerror(errno));
        return -2;
    }
    
    /* pass result filename to command */
    fprintf (mesf, "@%s ", result_filename);
    if (ferror (mesf)) {
        print_error (ERROR_LEVEL, "internal error: message buffer to short");
        return -2;
    }
    
    /* format command with remaining arguments */
    int command_res = command->handler (
        mesf, tunnel_name, argc - i, argv + i
    );

    if (command_res < 0) {
        print_error (ERROR_LEVEL, "error: command parse error\n");
        return -1;
    }
    
    fflush (mesf);
    
    if (ferror (mesf)) {
        print_error (ERROR_LEVEL,
            "error: message too long (max = %i ch.)\n",
            CONTROL_PIPE_MESSAGE_SIZE - 1);
        return -1;
    }
    
    print_error (DEBUG_LEVEL, "command to be passed:\n%s\n", buf);

    /* try to open control file for writing */
    int control_fd = open (control_filename, O_WRONLY | O_NONBLOCK, 0600);
    if (control_fd < 0) {
        int errorno = errno;
        switch (errorno)
        {
        case EACCES:
            print_error (ERROR_LEVEL,
                "Unable to open %s for writing."
                " Is xl2tpd running and you have appropriate permissions?\n",
                control_filename);
            break;
        default:
            print_error (ERROR_LEVEL,
                "Unable to open %s for writing: %s\n",
                control_filename, strerror (errorno));
        }
        return -1;
    }

    /* turn off O_NONBLOCK */
    if (fcntl (control_fd, F_SETFL, O_WRONLY) == -1) {
        print_error (ERROR_LEVEL,
            "Can not turn off nonblocking mode for control_fd: %s\n",
            strerror(errno));
        return -2;
    }
    
    /* pass command to control pipe */
    if (write (control_fd, buf, ftell (mesf)) < 0) {
      int errorno = errno;
      print_error (ERROR_LEVEL,
                "Unable to write to %s: %s\n",
                control_filename, strerror (errorno));
      close (control_fd);
      return -1;
    }
    close (control_fd);
    
    /* read result from pipe */
    char rbuf[CONTROL_PIPE_MESSAGE_SIZE] = "";
    int command_result_code = read_result (
        result_fd, rbuf, CONTROL_PIPE_MESSAGE_SIZE
    );
    /* rbuf contains a newline, make it double to form a boundary. */
    print_error (DEBUG_LEVEL, "command response: \n%s\n", rbuf);
    
    return command_result_code;
}

void print_error (int level, const char *fmt, ...)
{
    if (level > log_level) return;
    va_list args;
    va_start (args, fmt);
    fprintf (stderr, "xl2tpd-control: ");
    vfprintf (stderr, fmt, args);
    va_end (args);
}


int read_result(int result_fd, char* buf, ssize_t size)
{
    /* read result from result_fd */
    /*FIXME: there is a chance to hang up reading.
             Should I create watching thread with timeout?
     */
    ssize_t readed = 0;
    ssize_t len;
    int write_pipe = 0;
    struct timeval tvs;
    struct timeval tve;
    unsigned long diff;
    gettimeofday(&tvs, NULL);

    do
    {
        len = read (result_fd, buf + readed, size - readed);
        if (len < 0)
        {
            if (errno == EINTR)
                continue;
            print_error (ERROR_LEVEL,
                "error: can't read command result: %s\n", strerror (errno));
            break;
        }
        else if (len == 0) {
            if(!write_pipe) {
                 gettimeofday(&tve, NULL);
                 diff = (tve.tv_sec - tvs.tv_sec) * 1000000 + (tve.tv_usec - tvs.tv_usec);
                 if (diff >= TIMEOUT) {
                     print_error (DEBUG_LEVEL, "error: read timout\n");
                     break;
                 } else {
                     usleep(10);
                     continue;
                 }
            }
            break;
        }
        else {
            write_pipe = 1;
            readed += len;
            if ((size - readed) <= 0)
                break;
       }
    } while (1);

    buf[readed] = '\0';

    /* scan result code */
    int command_result_code = -3;
    sscanf (buf, "%i", &command_result_code);

    return command_result_code;
}

int command_add
(FILE* mesf, char* tunnel, int optc, char *optv[], int reqopt)
{
    if (optc <= 0) {
        print_error (ERROR_LEVEL, "error: tunnel configuration expected\n");
        return -1;
    }

    fprintf (mesf, "%c %s ", reqopt, tunnel);
    int i;
    int wait_key = 1;
    for (i = 0; i < optc; i++)
    {
        fprintf (mesf, "%s", optv[i]);
        if (wait_key)
        {
            /* try to find '=' */
            char* eqv = strstr (optv[i], "=");
            if (eqv) {
                /* check is it not last symbol */
                if (eqv != (optv[i] + strlen(optv[i]) - 1)) {
                    fprintf (mesf, ";"); /* end up option */
                } else {
                    wait_key = 0; /* now we waiting for value */
                }
            } else { /* two-word key */
                fprintf (mesf, " "); /* restore space */
            }
        } else {
            fprintf (mesf, ";"); /* end up option */
            wait_key = 1; /* now we again waiting for key */
        }
    }
    return 0;
}

int command_add_lac
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    return command_add(mesf, tunnel, optc, optv, CONTROL_PIPE_REQ_LAC_ADD_MODIFY);
}

int command_add_lns
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    return command_add(mesf, tunnel, optc, optv, CONTROL_PIPE_REQ_LNS_ADD_MODIFY);
}


int command_connect_lac
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    fprintf (mesf, "%c %s", CONTROL_PIPE_REQ_LAC_CONNECT, tunnel);
    /* try to read authname and password from opts */
    if (optc > 0) {
        if (optc == 1)
            fprintf (mesf, " %s", optv[0]);
        else // optc >= 2
            fprintf (mesf, " %s %s", optv[0], optv[1]);
    }
    return 0;
}

int command_disconnect_lac
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    UNUSED(optc);
    UNUSED(optv);
    fprintf (mesf, "%c %s", CONTROL_PIPE_REQ_LAC_DISCONNECT, tunnel);
    return 0;
}

int command_remove_lac
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    UNUSED(optc);
    UNUSED(optv);
    fprintf (mesf, "%c %s", CONTROL_PIPE_REQ_LAC_REMOVE, tunnel);
    return 0;
}

int command_status_lns
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    UNUSED(optc);
    UNUSED(optv);
    fprintf (mesf, "%c %s", CONTROL_PIPE_REQ_LNS_STATUS, tunnel);
    return 0;
}

int command_status_lac
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    UNUSED(optc);
    UNUSED(optv);
    fprintf (mesf, "%c %s", CONTROL_PIPE_REQ_LAC_STATUS, tunnel);
    return 0;
}

int command_available
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    UNUSED(optc);
    UNUSED(optv);
    fprintf (mesf, "%c %s", CONTROL_PIPE_REQ_AVAILABLE, tunnel);
    return 0;
}

int command_remove_lns
(FILE* mesf, char* tunnel, int optc, char *optv[])
{
    UNUSED(optc);
    UNUSED(optv);
    fprintf (mesf, "%c %s", CONTROL_PIPE_REQ_LNS_REMOVE, tunnel);
    return 0;
}