/* Program to correct SPECSYS and SPECSYSG in the WAPP CIMAFITS headers  */

/* Mikael Lerner   ---   28-03-2006 */



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


#define BLOCK 40000000


int elements[] = { 18, 19 };


int check_block(char *p, int block) {

  unsigned char *p1;
  int i, j;

  for ( i = 0 ; i < 8 ; i++ ) {
    for ( j = 0 ; j < 2 ; j++ ) {
      p1 = p + 48960 + block * 16 * 1288 + ( i * 2 + j ) * 1288 + 154 * 8 + 2;
      if ( *p1++ != j )
	return -1;
      if ( *p1 != i )
	return -1;
    }
  }

  return(0);
}



int reshuffle(char *p, int block, int element) {

  char *p1;
  char values[16][8];
  int i, j;

  /*
  for ( i = 0 ; i < 8 ; i++ ) {
    for ( j = 0 ; j < 2 ; j++ ) {
      p1 = p + 48960 + block * 16 * 1288 + ( i * 2 + j ) * 1288 + element * 8;
      memcpy(values[((i+1)*2+j)%16], p1, 8);
    }
  }
  */

  for ( i = 0 ; i < 8 ; i++ ) {
    for ( j = 0 ; j < 2 ; j++ ) {
      p1 = p + 48960 + block * 16 * 1288 + ( i * 2 + j ) * 1288 + element * 8;
      /*
      memcpy(p1, values[i*2+j], 8);
      */
      memcpy(p1, "TOPOCENT", 8);
    }
  }

  return(0);
}



main(int argc, char *argv[]) {

  char file[256];
  char *p;
  int file_id;
  int rows, i, j;

  if ( argc < 2 ) {
    printf("ERROR: no file name given!\n");
    exit(1);
  }

  strncpy(file, argv[1], sizeof(file)-1);

  printf("Correcting file '%s' ...\n", file);

  if ( ( p = (char *) calloc(BLOCK, 1) ) == NULL ) {
    printf("ERROR: failed to allocate memory!\n");
    exit(1);
  }

  if ( ( file_id = open(file, O_RDWR) ) == -1 ) {
    printf("ERROR: can't open file '%s'!\n", file);
    exit(1);
  }

  if ( read(file_id, p, BLOCK) != BLOCK ) {
    printf("ERROR: can't read file '%s'!\n", file);
    close(file_id);
    exit(1);
  }

  if ( sscanf(&p[3220], "%d", &rows) != 1 ) {
    printf("ERROR: can't read number of rows in file '%s'!\n", file);
    close(file_id);
    exit(1);
  }

  if ( rows < 16 || rows > 42000 || (rows/16)*16 != rows ) {
    printf("ERROR: bad number of rows %d in file '%s'!\n", rows, file);
    close(file_id);
    exit(1);
  }

  printf("Processing %d rows (=%d ALFA scans) ...\n", rows, rows/16);

  for ( i = 0 ; i < rows/16 ; i++ ) {
    if ( check_block(p, i) == -1 ) {
      printf("ERROR: ALFA scan %d in file '%s' is not in valid order!\n", i+1,
	     file);
      close(file_id);
      exit(1);
    }
  }

  for ( i = 0 ; i < rows/16 ; i++ ) {
    for ( j = 0 ; j < sizeof(elements)/sizeof(int) ; j++ ) {
      if ( reshuffle(p, i, elements[j]) == -1 ) {
	printf("ERROR: can't reshuffle ALFA scan %d in file '%s'!\n", i+1,
	       file);
	close(file_id);
	exit(1);
      }
    }
  }

  if ( lseek(file_id, 0, SEEK_SET) == -1 ) {
    printf("ERROR: can't reposition file '%s' for writing!\n", file);
    close(file_id);
    exit(1);
  }

  if ( write(file_id, p, BLOCK) != BLOCK ) {
    printf("ERROR: failed writing to file '%s'!\n", file);
    printf("FATAL ERROR: file '%s' is now corrupted!\n", file);
    close(file_id);
    exit(1);
  }

  close(file_id);

  printf("Wrote modifications to file '%s'.\n", file);

  exit(0);
}