#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include "fakedisc.h"

/* Reminders from fakedisc.h

  typedef unsigned char byte;
  typedef byte block[512];

  int createdisc(const char *name, int number_of_blocks);
  int mountdisc(const char *name);
  void dismountdisc(int discnum);

  int discsize(int discnum);
  int writeblock(int discnum, int blocknum, void *b);
  int readblock(int discnum, int blocknum, void *b);
*/

int dnum = -1;
const int maximum_name_length = 24;
const int direntries_per_block = 16;
const int firstdirblock=1, lastdirblock=4;

struct direntry
{ char name[maximum_name_length];
  int firstblock;
  int size; };

struct dirblock
{ direntry entry[direntries_per_block]; };

bool filenameequal(char * s, char * t)
{ for (int i=0; i<maximum_name_length; i+=1)
  { if (toupper(s[i]) != toupper(t[i]))
      return false;
    if (s[i] == 0)
      return true; }
  return true; }

void filenamecopy(char * dest, char * src)
{ for (int i=0; i<maximum_name_length; i+=1)
  { dest[i] = src[i];
    if (dest[i] == 0)
      break; } }

void filenameprint(char * s)
{ for (int i=0; i<maximum_name_length; i+=1)
  { char c = s[i];
    if (c == 0)
      break;
    if (c>' ' && c<='~')
      putchar(c);
    else
      printf("[%d]", c); } }

direntry findfile(char * name)
{ for (int i = firstdirblock; i<=lastdirblock; i+=1)
  { dirblock buffer;
    readblock(dnum, i, & buffer);
    for (int j=0; j<direntries_per_block; j+=1)
    { if (filenameequal(name, buffer.entry[j].name))
        return buffer.entry[j]; } }
  direntry x;
  x.name[0] = 0;
  return x; }

void addfile(char * name, int fblk, int size)
{ for (int i = firstdirblock; i<=lastdirblock; i+=1)
  { dirblock buffer;
    readblock(dnum, i, & buffer);
    for (int j=0; j<direntries_per_block; j+=1)
    { if (filenameequal(name, buffer.entry[j].name))
      { printf("error, name in use\n");
        return; }
      if (buffer.entry[j].name[0] == 0)
      { filenamecopy(buffer.entry[j].name, name);
        buffer.entry[j].firstblock = fblk;
        buffer.entry[j].size = size;
        writeblock(dnum, i, & buffer);
        return; } } }
  printf("root dir full\n"); }

void printchar(int c)
{ if (c>=' ' && c<='~')
    putchar(c);
  else if (c=='\n')
    printf("\\n\n");
  else
    printf("[%d]", c); }

void printstring(char * s)
{ for (int i=0; s[i]!=0; i+=1)
    printchar(s[i]); }

void command_create(char * part[])
{ bool ok = createdisc(part[1], atol(part[2]));
  if (ok)
  { dnum = mountdisc(part[1]);
    printf("OK, \"%s\", %d blocks\n", part[1], discsize(dnum)); }
  else
  { printf("create failed\n");
    return; }
  dirblock buffer;
  for (int i=0; i<direntries_per_block; i+=1)
    buffer.entry[i].name[0]=0;
  for (int i=firstdirblock; i<=lastdirblock; i+=1)
    writeblock(dnum, i, &buffer); }

void command_dir()
{ if (dnum < 0)
  { printf("no disc mounted\n");
    return; }
  dirblock buffer;
  for (int i = firstdirblock; i<=lastdirblock; i+=1)
  { readblock(dnum, i, & buffer);
    for (int j=0; j<direntries_per_block; j+=1)
    { if (buffer.entry[j].name[0]==0)
        continue;
      filenameprint(buffer.entry[j].name);
      int firstb = buffer.entry[j].firstblock;
      int size = buffer.entry[j].size;
      int numblocks = (size+511)/512;
      if (size == 0)
        printf(": 0 bytes\n");
      else
        printf(": %d bytes, blocks %d to %d\n", size, firstb, firstb+numblocks-1); } } }

void command_make(char * part[])
{ if (dnum < 0)
  { printf("no disc mounted\n");
    return; }
  char * name = part[1];
  int bnum = atol(part[2]);
  int nbytes = atol(part[3]);
  char * realfile = part[4];
  block buffer;
  int bnum1 = bnum;
  int pos = 0;   // how full is the buffer?
  FILE * fin = fopen(realfile, "r");
  if (fin==NULL)
  { printf("can't open '%s'\n", realfile);
    return; }
  if (nbytes==0)
    printf("using no blocks\n");
  else
  { printf("using blocks %d", bnum);
    for (int i=0; i<nbytes; i+=1)
    { if (pos==512)
      { writeblock(dnum, bnum, buffer);
        bnum+=1;
        pos=0; }
      int c = fgetc(fin);
      if (c == EOF)
        break;
      buffer[pos] = c;
      pos+=1; }
    if (pos!=0)
      writeblock(dnum, bnum, buffer);
    printf(" to %d\n", bnum); }
  addfile(name, bnum1, nbytes); }

void command_mount(char * name)
{ dnum = mountdisc(name);
  if (dnum < 0)
    printf("mount failed\n");
  else
    printf("%d blocks\n", discsize(dnum)); }

void command_readblock(char * bn)
{ if (dnum < 0)
  { printf("no disc mounted\n");
    return; }
  int blocknum = atol(bn);
  block buffer;
  bool ok = readblock(dnum, blocknum, buffer);
  if (ok)
    printstring((char *)buffer);
  else
    printf("read failed\n"); }

void command_read(char * name)
{ if (dnum < 0)
  { printf("no disc mounted\n");
    return; }
  block buffer;
  direntry de = findfile(name);
  if (de.name[0] == 0)
  { printf("can't find file \"%s\"\n", name);
    return; }
  int bnum = de.firstblock, pos = 0;
  char c = '\n';
  for (int i=0; i<de.size; i+=1)
  { if (pos==0)
    { readblock(dnum, bnum, buffer);
      bnum+=1; }
    c = buffer[pos];
    printchar(c);
    pos += 1;
    if (pos==512)
      pos = 0; }
  if (c != '\n')
    printf("\n"); }

void command_exit()
{ if (dnum >= 0)
    dismountdisc(dnum); }

void main(int argc, char * argv[])
{ char line[1000];
  char * part[100];
  int numparts;
  dnum = -1;

  if (argc > 1)
    command_mount(argv[1]);

  while (true)
  { printf("> ");
    char * s = fgets(line, 999, stdin);
    if (s==NULL) break;
    numparts = 0;
    s = strtok(line, " \r\n");
    while (s != NULL)
    { part[numparts] = s;
      numparts += 1;
      s = strtok(NULL, " \r\n"); }
    if (numparts == 0)
      continue;

    else if (strcmp(part[0], "?") == 0)
    { printf("   create name number-of-blocks\n");
      printf("   dir\n");
      printf("   m name\n");
      printf("   make name first-block-number number-of-bytes real-source-file\n");
      printf("   r block-number\n");
      printf("   read name\n");
      printf("   w block-number string-with-no-spaces\n");
      printf("   x\n"); }

    else if (strcasecmp(part[0], "create") == 0 && numparts == 3)
      command_create(part);
    else if (strcasecmp(part[0], "dir") == 0 && numparts == 1)
      command_dir();
    else if (strcasecmp(part[0], "m") == 0 && numparts == 2)
      command_mount(part[1]);
    else if (strcasecmp(part[0], "make") == 0 && numparts == 5)
      command_make(part);
    else if (strcasecmp(part[0], "r") == 0 && numparts == 2)
      command_readblock(part[1]);
    else if (strcasecmp(part[0], "read") == 0 && numparts == 2)
      command_read(part[1]);
    else if (strcasecmp(part[0], "x") == 0 && numparts == 1)
    { command_exit();
      break; }
    else
      printf("unrecognised command \"%s\"\n", part[0]); } }