#include <stdio.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <getopt.h>
#include <signal.h>
#include <string.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <errno.h>


/////////////////////////////////////////////////////////////////////////////////////////
/*FLAGS FROM KERNEL*/

#define _MS_RDONLY       (1<<0)
#define _MS_NOSUID       (1<<1)
#define _MS_NODEV        (1<<2)
#define _MS_NOEXEC       (1<<3)
#define _MS_SYNCHRONOUS  (1<<4)
#define _MS_REMOUNT      (1<<5)
#define _MS_MANDLOCK     (1<<6)
#define _MS_DIRSYNC      (1<<7)
#define _MS_NOATIME      (1<<10)
#define _MS_NODIRATIME   (1<<11)
#define _MS_BIND         (1<<12)
#define _MS_MOVE         (1<<13)
#define _MS_REC          (1<<14)
#define _MS_SILENT       (1<<15)
#define _MS_POSIXACL     (1<<16)
#define _MS_UNBINDABLE   (1<<17)
#define _MS_PRIVATE      (1<<18)
#define _MS_SLAVE        (1<<19)
#define _MS_SHARED       (1<<20)
#define _MS_RELATIME     (1<<21)
#define _MS_KERNMOUNT    (1<<22)
#define _MS_I_VERSION    (1<<23)
#define _MS_STRICTATIME  (1<<24)
#define _MS_LAZYTIME     (1<<25)

#define STRUCT_LEN(VAR,STRUCT) ((sizeof(VAR)/sizeof(STRUCT))-1)

#define max(a,b) \
   ({ __typeof__ (a) _a = (a); \
       __typeof__ (b) _b = (b); \
     _a > _b ? _a : _b; })

typedef struct vfs_option_params {
    char *val;
    char *descr;
} vfs_option_params;

vfs_option_params vfs_options_proc_params_hidepid[] = {
    {"0","Everybody may access all proc"},
    {"1","User can access only their own proc, not other /proc/[pid]"},
    {"2","As for mode 1, extra hides pid directories of others"},
    {NULL,NULL},
};

vfs_option_params vfs_options_proc_params_gid[] = {
    {"gid","usergroup who sees /proc in mode 0"},
    {NULL,NULL},
};

typedef struct vfs_options 
{
    char *options;
    char *description;
    vfs_option_params *params;
} vfs_options;

vfs_options vfs_options_proc[] =
{
    {"hidepid=\%u" ,"",                                     (struct vfs_option_params *)&vfs_options_proc_params_hidepid},
    {"gid=\%u"     ,"user group that can access process",   (struct vfs_option_params *)&vfs_options_proc_params_gid},
    {NULL,NULL,NULL}
};


static const struct vfs {
    char *name;           //filesystem name
    long flags;           //dunno
    char *mountpoint;     //default mount point if mount dir is not set
    int nosource;         //does fs have source or not
    vfs_options *options; //hellpers to show all possible options to config fs mount
} vfstab[] = {
    {"devtmpfs",  0, "/Device",  1, NULL},
    {"mqueue",    0, "/Queue/",  1, NULL},
    {"proc",      0, "/Process", 1, (struct vfs_options*)&vfs_options_proc},
    {"tmpfs",     0, "/Ram",     1, NULL},
    {"sysfs",     0, "/System",  1, NULL},
    {"ext4",      0, NULL,       0, NULL},
    {"ext3",      0, NULL,       0, NULL},
    {"ext2",      0, NULL,       0, NULL},
    {"vfat",      0, NULL,       0, NULL},
    {"msdos",     0, NULL,       0, NULL},
    {"ntfs",      0, NULL,       0, NULL},
    {NULL,        0, NULL,       0, NULL},
};

static const struct mount_flags
{
    char *name;
    unsigned long bitfield;
} mountflgs[] = {
    {"bind",_MS_BIND},
    {"move",_MS_MOVE},
    {"rdonly",_MS_RDONLY},
    {"lazytime",_MS_LAZYTIME},
    {"nodev",_MS_NODEV},
    {"noexec",_MS_NOEXEC},
    {"nosuid",_MS_NOSUID},
    {"remount",_MS_REMOUNT},
    {"silent",_MS_SILENT},
    {"sync",_MS_SYNCHRONOUS},
    {NULL,0},
};

typedef struct {
    char *f_source_dir;
    char *f_target_dir;
    char *f_type;
    char *f_dir;
    char *f_flags;//g_params.f_output = 1;
    unsigned long mount_flags;
    char *f_options;
    int   f_verbose;
    int   f_helper;
} mount_params;

#define VERBOSE() if (g_params.f_verbose == 1)

static mount_params g_params;

void helper(char *progname)
{
    printf("Usage: %s [OPTS]\n\n"
        "Version: 0.0.1 \n"
        "-s source directory\n"
        "-d target directory\n"
        "-t filesystem type\n"
        "-f mount flags\n"
        "-o mount fs options\n"
        "-v verbose output\n"
        "-h help options\n"
        "-a helper for filetype options\n"
        "\n"
        , progname);
}

void sig_handler(int signo)
{
    switch(signo)
    {
        case SIGINT:
            //printf("Catch SIGINT Exit\n");
            //if (g_params.f_output)
            //{
            //    printf("Data in %d bytes Data out %d bytes",g_stats.cnt_in,g_stats.cnt_out);
            //}
        default:
            printf("Unknown signal %d\n",signo);
    }
    exit(0);
}

int check_filetype(char *fsname)
{
    int i;
    for (i=0;i<STRUCT_LEN(vfstab,struct vfs);i++)
    {
         if (strncmp(vfstab[i].name,fsname,max(strlen(vfstab[i].name),strlen(fsname))) == 0)
         {
            return 1;
         }
    }

    return 0;
}

int get_fs_idx(char *fsname)
{
    int i;
    for (i=0;i<STRUCT_LEN(vfstab,struct vfs);i++)
    {
         if (strncmp(vfstab[i].name,fsname,max(strlen(vfstab[i].name),strlen(fsname))) == 0)
         {
            return i;
         }
    }
    return -1;
}

unsigned long str2flag(char *opt)
{
    int i;
    for (i=0;i<STRUCT_LEN(mountflgs, struct mount_flags);i++)
    {
        if (strncmp(mountflgs[i].name,opt,strlen(mountflgs[i].name)) == 0)
        {
            return mountflgs[i].bitfield;
        }
    }
    return 0;
}

int smount(
    const char *source, 
    const char *target,
    const char *filesystemtype,
    unsigned long mountflags,
    const void *data)
{
    int ret=-1;

    if (g_params.f_verbose)
    {
        printf("Syscal params:\n");
        printf("source     :%s\n",source);
        printf("target     :%s\n",target);
        printf("filesystem :%s\n",filesystemtype);
        printf("mountflags :%lu\n",mountflags);
        printf("data       :%016xxd\n",data);
    }
    ret = syscall(SYS_mount,source,target,filesystemtype,mountflags,data);

    return ret;
}

int main(int argc, char **argv)
{
    int c;
    int i,j,k;
    int fs_idx=-1;

    printf("One big real mount\n");

    if (signal(SIGINT,sig_handler) == SIG_ERR)
    {
        printf("cannot register signal handler\n");
        exit(1);
    }

    memset(&g_params,0,sizeof(g_params));
    
    //process arguments
    while ((c = getopt(argc, argv, "ad:t:f:o:vs:")) != -1)
    {
        switch (c)
        {
            case 'a':
                //g_params.f_output = 1;
                g_params.f_helper = 1;
                break;
            case 's':
                g_params.f_source_dir = optarg;
                break;
            case 'd':
                g_params.f_target_dir = optarg;
                break;
            case 't':
                g_params.f_type = optarg;
                break;
            case 'f':
                g_params.f_flags = optarg;
                break;
            case 'o':
                g_params.f_options = optarg;
                break;
            case 'v':
                g_params.f_verbose = 1;
                break;
            default:
                helper(argv[0]);
                exit(1);
        }
    }

    if (1 == g_params.f_helper)
    {
        for (i=0;i<STRUCT_LEN(vfstab,struct vfs);i++)
        {
            printf("%s %s\n",vfstab[i].name,vfstab[i].mountpoint);
            if (vfstab[i].options != NULL)
            {
                j = 0;
                while (vfstab[i].options[j].options != NULL)
                {
                    printf("\t%s %s\n",
                        vfstab[i].options[j].options,
                        vfstab[i].options[j].description
                    );
                    k = 0;
                    while(vfstab[i].options[j].params[k].val != NULL)
                    {
                        printf("\t\t%s %s\n",
                            vfstab[i].options[j].params[k].val,
                            vfstab[i].options[j].params[k].descr
                        );
                        k++;
                    }
                    j++;
                }
            }
        }
    }

    if (NULL != g_params.f_type)
    {
        //dindt found fs name
        if (check_filetype(g_params.f_type) != 1)
        {
            printf("Unknow file type %s\n",g_params.f_type);
            printf("Supported formats: ");
            for (i=0;i<STRUCT_LEN(vfstab,struct vfs);i++)
            {
                printf("%s ",vfstab[i].name);
            }
            printf("\n");
            return 1;
        //found fs name
        } else
        {
            //find index of fs in fs table
            fs_idx = get_fs_idx(g_params.f_type); //should allways be possitive as its allready checked
            VERBOSE() printf("Filesystem is have index %d\n",fs_idx);
            
        }
        
    } else {
        printf("Filesystem type is not set\n");
        return -1;
    }

    if (NULL != g_params.f_flags)
    {
        char *token = strtok(g_params.f_flags,",");
        VERBOSE() printf("Flags: %d\n",g_params.mount_flags);
        while ( token != NULL )
        {
            VERBOSE() printf("Flags: %s\n",token);
            g_params.mount_flags |= str2flag(token);
            VERBOSE() printf("Flags: %d\n",g_params.mount_flags);
            token = strtok(NULL,",");
        }
    }

    //if target dir is defined use it
    if (NULL != g_params.f_target_dir)
    {
        VERBOSE() printf("Target dir %s\n",g_params.f_target_dir);
        mkdir(g_params.f_target_dir, 0000);
    //if target dir is not define use default one
    } else {
        g_params.f_target_dir = vfstab[fs_idx].mountpoint;
        VERBOSE() printf("Default target dir is set to %s\n",g_params.f_target_dir);
        mkdir(g_params.f_target_dir, 0000);
    }

    //source dir is not need for some of the fs'es
    if (((NULL != g_params.f_source_dir) && (vfstab[fs_idx].nosource == 0)) ||
        ((NULL == g_params.f_source_dir) && (vfstab[fs_idx].nosource == 1)))
    if ((NULL != g_params.f_target_dir) && 
        (NULL != g_params.f_flags) &&
        (NULL != g_params.f_type))
    {
        printf("Flags: %d\n",g_params.mount_flags);
        int ret = smount(
            g_params.f_source_dir,
            g_params.f_target_dir,
            g_params.f_type, 
            g_params.mount_flags, 
            "");
        int err = errno;
        printf("Mount exit code %d\n",ret);
        if (ret==-1)
        {
            printf("Strerr: %d %s\n",err,strerror(err));
        }
    }

    return 0;
}