/*
 * This file is part of the ethersrv-linux project
 * Copyright (C) 2017 Mateusz Viste
 */

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/statvfs.h> /* statvfs() for diskfree calls */
#include <sys/stat.h>    /* stat() */
#include <sys/types.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>      /* free() */
#include <string.h>
#include <time.h>        /* time_t, struct tm... */
#include <unistd.h>
#include <linux/msdos_fs.h>
#include <sys/ioctl.h>

#include "debug.h"
#include "fs.h" /* include self for control */

/* database containing file/dir identifiers and their names - this is used
 * whenever ethersrv-linux needs to provide etherdfs with a 16bit identifier
 * that etherdfs will subsequently use to refer to this file or dir (typically
 * used during FindFirst+FindNext steps and Open/Create+Write/Read.
 * the struct may also contain an entire directory listing computed by FFirst
 * (and used then by FNext) */
static struct sfsdb {
  char *name;
  time_t lastused;
  struct sdirlist { /* pointer to dir listing, if dir and if generated by FFirst */
    struct fileprops fprops;
    struct sdirlist *next;
  } *dirlist;
} fsdb[65536];

/* frees a sdirlist linked list */
static void freedirlist(struct sdirlist *d) {
  while (d != NULL) {
    struct sdirlist *victim = d;
    d = d->next;
    free(victim);
  }
}

/* returns the "start sector" of a filesystem item (file or directory).
 * it registers the item into the file cache and returns its id or 0xffff on
 * error */
unsigned short getitemss(char *f) {
  unsigned short i, firstfree = 0xffffu, oldest = 0;
  time_t now = time(NULL);
  /* see if not already in cache */
  for (i = 0; i < 0xffffu; i++) {
    /* is it what I am looking after? */
    if ((fsdb[i].name != NULL) && (strcmp(fsdb[i].name, f) == 0)) {
      fsdb[i].lastused = now;
      return(i);
    }
    /* if the entry is not what I was looking for, check its last usage and remove if older than one hour */
    if ((now - fsdb[i].lastused) > 3600) {
      free(fsdb[i].name);
      freedirlist(fsdb[i].dirlist);
      memset(&(fsdb[i]), 0, sizeof(struct sfsdb));
    }
    /* if slot free, remember it, perhaps we'll use it */
    if ((firstfree == 0xffffu) && (fsdb[i].name == NULL)) {
      firstfree = i;
    } else if (fsdb[oldest].lastused > fsdb[i].lastused) { /* otherwise see if it's the oldest entry (I might remove it later if no choice) */
      oldest = i;
    }
  }
  /* not found - if no free slot available, pick the oldest one and replace it */
  if (firstfree == 0xffffu) {
    firstfree = oldest;
    free(fsdb[oldest].name);
    freedirlist(fsdb[oldest].dirlist);
    memset(&(fsdb[oldest]), 0, sizeof(struct sfsdb));
  }
  /* register it */
  fsdb[firstfree].name = strdup(f);
  if (fsdb[firstfree].name == NULL) {
    fprintf(stderr, "ERROR: OUT OF MEM!\n");
    return(0xffffu);
  }
  fsdb[firstfree].lastused = now;
  return(firstfree);
}

char *sstoitem(unsigned short ss) {
  return(fsdb[ss].name);
}

/* turns a character c into its upper-case variant */
char upchar(char c) {
  if ((c >= 'a') && (c <= 'z')) c -= ('a' - 'A');
  return(c);
}

/* translates a filename string into a fcb-style block ("FILE0001TXT") */
void filename2fcb(char *d, char *s) {
  int i;
  /* fill the FCB block with spaces */
  for (i = 0; i < 11; i++) d[i] = ' ';
  /* cover '.' and '..' entries */
  for (i = 0; i < 8; i++) {
    if (s[i] != '.') break;
    d[i] = '.';
  }
  /* fill in the filename, up to 8 chars or first dot, whichever comes first */
  for (; i < 8; i++) {
    if ((s[i] == '.') || (s[i] == 0)) break;
    d[i] = upchar(s[i]);
  }
  s += i;
  /* fast forward to either the first dot or NULL-terminator */
  for (; ((*s != '.') && (*s != 0)); s++);
  if (*s == 0) return;
  s++; /* skip the dot */
  /* fill in the extension */
  d += 8;
  for (i = 0; i < 3; i++) {
    if ((s[i] == '.') || (s[i] == 0)) break;
    *d = upchar(s[i]);
    d++;
  }
}

/* converts a time_t into a DWORD with DOS (FAT-style) timestamp bits
               24                16                 8                 0
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|Y|Y|Y|Y|Y|Y|Y|M| |M|M|M|D|D|D|D|D| |h|h|h|h|h|m|m|m| |m|m|m|s|s|s|s|s|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 \___________/\________/\_________/ \________/\____________/\_________/
    year        month       day        hour       minute      seconds */
static unsigned long time2dos(time_t t) {
  unsigned long res;
  struct tm *ltime;
  ltime = localtime(&t);
  res = ltime->tm_year - 80; /* tm_year is years from 1900, while FAT needs years from 1980 */
  res <<= 4;
  res |= ltime->tm_mon + 1; /* tm_mon is in range 0..11 while FAT expects 1..12 */
  res <<= 5;
  res |= ltime->tm_mday;
  res <<= 5;
  res |= ltime->tm_hour;
  res <<= 6;
  res |= ltime->tm_min;
  res <<= 5;
  res |= (ltime->tm_sec >> 1); /* DOS stores seconds divided by two */
  return(res);
}

/* match FCB-style filename to a FCB-style mask ("FILE0001???"), returns 0 if
 * matching, non-zero otherwise - a FCB block is *exactly* 11 bytes long */
static int matchfile2mask(char *msk, char *fil) {
  int i;
  /* compare filename to mask */
  for (i = 0; i < 11; i++) {
    if ((upchar(fil[i]) != upchar(msk[i])) && (msk[i] != '?')) return(-1);
  }
  return(0);
}


/* provides DOS-like attributes for item i, as well as size, filling fprops
 * accordingly. returns item's attributes or 0xff on error.
 * DOS attr flags: 1=RO 2=HID 4=SYS 8=VOL 16=DIR 32=ARCH 64=DEVICE */
unsigned char getitemattr(char *i, struct fileprops *fprops, unsigned char fatflag) {
  uint32_t attr;
  int fd;
  struct stat statbuf;
  if (stat(i, &statbuf) != 0) return(0xff); /* error (probably doesn't exist) */
  /* zero out fprops and fill it out */
  if (fprops != NULL) {
    char *fname = i;
    char *ptr;
    /* set fname to the file part of i */
    for (ptr = i; *ptr != 0; ptr++) {
      if (((*ptr == '/') || (*ptr == '\\')) && (*(ptr+1) != 0)) fname = ptr + 1;
    }
    /* zero out struct and set timestamp & fcbname */
    memset(fprops, 0, sizeof(struct fileprops));
    fprops->ftime = time2dos(statbuf.st_mtime);
    filename2fcb(fprops->fcbname, fname);
  }
  /* is this is a directory? */
  if (S_ISDIR(statbuf.st_mode)) {
    if (fprops != NULL) fprops->fattr = 16;
    return(16);
  }
  /* not a directory, set size */
  if (fprops != NULL) fprops->fsize = statbuf.st_size;
  /* if not a FAT drive, return a fake attribute of 0x20 (archive) */
  if (fatflag == 0) return(0x20);
  /* try to fetch DOS attributes by calling the FAT IOCTL API */
  fd = open(i, O_RDONLY);
  if (fd == -1) return(0xff);
  if (ioctl(fd, FAT_IOCTL_GET_ATTRIBUTES, &attr) < 0) {
    fprintf(stderr, "Failed to fetch attributes of '%s'\n", i);
    close(fd);
    return(0);
  } else {
    close(fd);
    if (fprops != NULL) fprops->fattr = attr;
    return(attr);
  }
}

/* set attributes fattr on file i. returns 0 on success, non-zero otherwise. */
int setitemattr(char *i, unsigned char fattr) {
  int fd, res;
  fd = open(i, O_RDONLY);
  if (fd == -1) return(-1);
  res = ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &fattr);
  close(fd);
  if (res < 0) return(-1);
  return(0);
}

/* generates a directory listing for *root and returns the number of file
 * system entries, or a negative value on error */
static long gendirlist(struct sfsdb *root, unsigned char fatflag) {
  char fullpath[1024];
  int fullpathoffset;
  struct dirent *diridx;
  DIR *dp;
  struct sdirlist *lastnode = NULL, *newnode;
  long res = 0;
  freedirlist(root->dirlist);
  dp = opendir(root->name);
  if (dp == NULL) return(-1);
  fullpathoffset = sprintf(fullpath, "%s/", root->name);
  for (;;) {
    diridx = readdir(dp);
    if (diridx == NULL) break;
    newnode = calloc(1, sizeof(struct sdirlist));
    if (newnode == NULL) {
      fprintf(stderr, "ERROR: out of mem!");
      break;
    }
    sprintf(fullpath + fullpathoffset, "%s", diridx->d_name);
    getitemattr(fullpath, &(newnode->fprops), fatflag);
    /* add new node to linked list */
    if (lastnode == NULL) {
      root->dirlist = newnode;
    } else {
      lastnode->next = newnode;
    }
    lastnode = newnode;
    res++;
  }
  closedir(dp);
  return(res);
}

/* searches for file matching the FCB-style template fcbtmpl in directory dss (dss is the starting sector of the directory, as obtained via getitemss) with AT MOST attributes attr, fills 'out' with the nth match. returns 0 on success, non-zero otherwise. *nth is updated with the nth id of the file that matched */
int findfile(struct fileprops *f, unsigned short dss, char *fcbtmpl, unsigned char attr, unsigned short *nth, int flags) {
  int n = 0;
  struct sdirlist *dirlist;
  /* recompute the dir listing if operation is FFirst (nth == 0) or if no
   * cache found */
  if ((*nth == 0) || (fsdb[dss].dirlist == NULL)) {
    long count = gendirlist(&(fsdb[dss]), flags & FFILE_ISFAT);
    if (count < 0) {
      fprintf(stderr, "Error: failed to scan dir '%s'\n", fsdb[dss].name);
      return(-1);
#ifdef DEBUG
    } else {
      DBG("scanned dir '%s' and found %ld items\n", fsdb[dss].name, count);
      for (dirlist = fsdb[dss].dirlist; dirlist != NULL; dirlist = dirlist->next) {
        DBG("  '%s' attr %02Xh (%ld bytes)\n", dirlist->fprops.fcbname, dirlist->fprops.fattr, dirlist->fprops.fsize);
      }
#endif
    }
  }
  /* */
  for (dirlist = fsdb[dss].dirlist; dirlist != NULL; dirlist = dirlist->next) {
    /* forward to where we need to start listing */
    n++;
    if (n <= *nth) continue;
    /* skip '.' and '..' items if directory is root */
    if ((dirlist->fprops.fcbname[0] == '.') && (flags & FFILE_ISROOT)) continue;
    /* if no match, continue */
    if (matchfile2mask(fcbtmpl, dirlist->fprops.fcbname) != 0) continue;
    /* do attributes match? (return only items with AT MOST the specified combination of hidden, system, and directory attributes if no VOL bit set, otherwise look for VOL only.
       DOS attribs: 1=RO 2=HID 4=SYS 8=VOL 16=DIR 32=ARCH 64=DEV */
    if (attr == 0x08) { /* I want VOL */
      if ((dirlist->fprops.fattr & 0x08) == 0) continue;
    } else { /* else return any file with at most the specified attributes */
      if ((attr | (dirlist->fprops.fattr & 0x16)) != attr) continue;
    }
    break;
  }
  if (dirlist != NULL) {
    *nth = n;
    memcpy(f, &(dirlist->fprops), sizeof(struct sdirlist));
    return(0);
  }
  return(-1);
}


/* creates or truncates a file f in directory d with attributes attr. returns 0 on success (and f filled), non-zero otherwise. */
int createfile(struct fileprops *f, char *d, char *fn, unsigned char attr, unsigned char fatflag) {
  char fullpath[512];
  FILE *fd;
  sprintf(fullpath, "%s/%s", d, fn);
  /* try to create/truncate the file */
  fd = fopen(fullpath, "wb");
  if (fd == NULL) return(-1);
  fclose(fd);
  /* set attribs (only if FAT drive) */
  if (fatflag != 0) {
    if (setitemattr(fullpath, attr) != 0) fprintf(stderr, "Error: failed to set attribute %02Xh to '%s'\n", attr, fullpath);
  }
  /* collect and set attributes */
  getitemattr(fullpath, f, fatflag);
  return(0);
}


/* returns disks total size, in bytes, or 0 on error. also sets dfree to the
 * amount of available bytes */
unsigned long long diskinfo(char *path, unsigned long long *dfree) {
  struct statvfs buf;
  unsigned long long res;
  if (statvfs(path, &buf) != 0) return(0);
  res = buf.f_blocks;
  res *= buf.f_frsize;
  *dfree = buf.f_bfree;
  *dfree *= buf.f_bsize;
  return(res);
}

/* try to create directory, return 0 on success, non-zero otherwise */
int makedir(char *d) {
  return(mkdir(d, 0));
}

/* try to remove directory, return 0 on success, non-zero otherwise */
int remdir(char *d) {
  return(rmdir(d));
}

/* change to directory d, return 0 if worked, non-zero otherwise (used
 * essentially to check whether the directory exists or not) */
int changedir(char *d) {
  return(chdir(d));
}

/* reads len bytes from file starting at sector fss, from offset, writes to
 * buff. returns amount of bytes read or a negative value on error. */
long readfile(unsigned char *buff, unsigned short fss, unsigned long offset, unsigned short len) {
  long res;
  char *fname;
  FILE *fd;
  fname = fsdb[fss].name;
  if (fname == NULL) return(-1);
  fd = fopen(fname, "rb");
  if (fd == NULL) return(-1);
  if (fseek(fd, offset, SEEK_SET) != 0) {
    fclose(fd);
    return(-1);
  }
  res = fread(buff, 1, len, fd);
  fclose(fd);
  return(res);
}


/* writes len bytes from buff to file starting at sect fss, starting at
 * offset. returns amount of bytes written or a negative value on error. */
long writefile(unsigned char *buff, unsigned short fss, unsigned long offset, unsigned short len) {
  long res;
  char *fname;
  FILE *fd;
  fname = fsdb[fss].name;
  if (fname == NULL) return(-1);
  /* if len is 0, then it means "truncate" or "extend" ! */
  if (len == 0) {
    DBG("truncate '%s' to %lu bytes\n", fname, offset);
    if (truncate(fname, offset) != 0) fprintf(stderr, "Error: truncate() failed\n");
    return(0);
  }
  /* otherwise do a regular write */
  DBG("write %u bytes into file '%s' at offset %lu\n", len, fname, offset);
  fd = fopen(fname, "r+b");
  if (fd == NULL) return(-1);
  if (fseek(fd, offset, SEEK_SET) != 0) {
    DBG("fseek() to %lu failed!\n", offset);
    fclose(fd);
    return(-1);
  }
  res = fwrite(buff, 1, len, fd);
  fclose(fd);
  return(res);
}


/* remove all files matching the pattern, returns the number of removed files if any found,
 * or -1 on error or if no matching file found */
int delfiles(char *pattern) {
  unsigned int i, fileoffset = 0;
  int ispattern = 0;
  char patterncopy[512];
  char dirnamefcb[12];
  char *dir, *fil;
  char filfcb[12];
  struct dirent *diridx;
  DIR *dp;
  /* scan the pattern for '?' characters, and find where the file part starts, also copy the pattern to patterncopy[] */
  for (i = 0; pattern[i] != 0; i++) {
    if (pattern[i] == '?') ispattern = 1;
    if (pattern[i] == '/') fileoffset = i;
    patterncopy[i] = pattern[i];
  }
  patterncopy[i] = 0;
  /* if regular file, delete it right away*/
  if (ispattern == 0) {
    if (unlink(pattern) != 0) {
      DBG("Error: failure to delete file '%s' (%s)\n", pattern, strerror(errno));
      return(-1);
    }
    return(1);
  }
  /* if pattern, get dir and fil parts and iterate over all directory */
  dir = patterncopy;
  patterncopy[fileoffset] = 0;
  fil = patterncopy + fileoffset + 1;
  filename2fcb(filfcb, fil);
  /* iterate over the directory and delete whatever is matching the pattern */
  dp = opendir(dir);
  if (dp == NULL) return(-1);
  for (;;) {
    diridx = readdir(dp);
    if (diridx == NULL) break;
    /* skip directories */
    if (diridx->d_type == DT_DIR) continue;
    /* if match, delete the file and continue */
    filename2fcb(dirnamefcb, diridx->d_name);
    if (matchfile2mask(filfcb, dirnamefcb) == 0) {
      char fname[512];
      sprintf(fname, "%s/%s", dir, diridx->d_name);
      if (unlink(fname) != 0) fprintf(stderr, "failed to delete '%s'\n", fname);
    }
  }
  closedir(dp);

  return(0);
}

/* rename fn1 into fn2 */
int renfile(char *fn1, char *fn2) {
  return(rename(fn1, fn2));
}

/* checks if a path resides on a FAT filesystem, returns 0 if so, non-zero otherwise */
int isfat(char *d) {
  int fd;
  uint32_t volid;
  /* test if I can fetch the serial id through calling the FAT IOCTL API */
  fd = open(d, O_RDONLY);
  if (fd == -1) return(-1);
  if (ioctl(fd, FAT_IOCTL_GET_VOLUME_ID, &volid) < 0) {
    close(fd);
    return(-1);
  }
  close(fd);
  return(0);
}

/* returns the size of an open file (or -1 on error) */
long getfopsize(unsigned short fss) {
  struct fileprops fprops;
  char *fname = fsdb[fss].name;
  if (fname == NULL) return(-1);
  if (getitemattr(fname, &fprops, 0) == 0xff) return(-1);
  return(fprops.fsize);
}