/*  ios_s.c  --  I/O service module for a sequence of input files */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

#define ERR_OPEN_INPUT 10
#define ERR_OPEN_OUTPUT 10
#define ERR_LINE_SIZE 12
#define ERR_LINE_SYNTAX 13
#define ERR_LINE_MISSING 14
#define ERR_COMMAND_LINE 20

#define LINE_SIZE 102

static char  Line_buffer [LINE_SIZE];

static FILE * infile;
static FILE * outfile;

static int  input_files_count = 0;
static int  output_files_count = 0;

static int  input_lines_count;

static void  syntax_error ( void );

FILE *  open_input_file ( char filename [] )
{
 if ( ++input_files_count > 1 )  fclose ( infile );
 input_lines_count = 0;
 infile = fopen ( filename, "rt" );
 if ( infile )  return ( infile );
 printf ( "error when opening the %d-th input file \"%s\"\n",
   input_files_count, filename );
 exit ( ERR_OPEN_INPUT );
}

FILE *  open_output_file ( char filename [] )
{
 if ( ++output_files_count > 1 )  fclose ( outfile );
 outfile = fopen ( filename, "wt" );
 if ( outfile )  return ( outfile );
 printf ( "error when opening the %d-th output file \"%s\"\n",
   output_files_count, filename );
 exit ( ERR_OPEN_OUTPUT );
}

int  get_line ( char ** start )
{   char c;  char * left;  char * right;
 ++ input_lines_count;
 do {
   if ( NULL == fgets ( Line_buffer, LINE_SIZE, infile ) )
     { * start = NULL;  return (-1); }
   c = * ( left = & Line_buffer [0] );
   while ( ( c != 0 ) && ( c != '[' ) && ( c != ']' ) )
     c = * ++left;
   if ( c == '[' )  break;
   if ( c == ']' )  syntax_error ();
   while ( left > & Line_buffer [0] ) {
     c = * (left-1);
     if  (
              (signed char) c < 0
           || ! isascii ( c )
           || ! isspace ( c )
         )
       break;
     --left;
   }
   if ( left > & Line_buffer [0] )  syntax_error ();
 } while ( 1 );
 c = * ( right = ++left );
 while ( ( c != 0 ) && ( c != '[' ) && ( c != ']' ) )
   c = * ++right;
 if ( right >= & Line_buffer [ LINE_SIZE - 1 ] ) {
   printf (
     "line %d of the %d-th input file: line length exceeds %d\n",
     LINE_SIZE - 2 );
   exit ( ERR_LINE_SIZE );
 }
 if ( c != ']' )  syntax_error ();
 * right = 0;
 * start = left;
 return ( right - left );
}

int  get_line_sure ( char ** start )
{   int n;
 n = get_line ( start );
 if ( n >= 0 )  return (n);
 printf ( "missing line %d of the %d-th input file\n",
  input_lines_count, input_files_count );
 exit ( ERR_LINE_MISSING );
}

void  err_command_line ( char usage [] )
{
 printf ( "usage: %s\n", usage );
 exit ( ERR_COMMAND_LINE );
}

static void  syntax_error ( void )
{
 printf ( "line %d of the %d-th input file is not of the form [...]\n",
   input_lines_count, input_files_count );
 exit ( ERR_LINE_SYNTAX );
}

/*  end of  ios_s.c  */