/*******************************************************************************
   Source code accompanying Assignment # 3:
   This file contains functions for reading and writing rolodex file entries.
   You should not modify this file.  The code that you write for the assignment
   should be put in another file.  To create your program, you will then need
   to compile the two .c files (this file and the one you write) and link
   the resultant object files to form the executable.
*******************************************************************************/

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

#define MAX_LEN    320    /* maximum # of characters in a field */

/***************************************************************************
NAME:        skip_white_space( const char *ptr )
INPUT:       ptr            : points to the current character
OUTPUT:      ---
RETURN:      const char *   : points to the next non-white-space character
DESCRIPTION: Skips over white space in the string given as 'ptr'.

---------------------------------------------------------------------------*/
static const char *skip_white_space( const char *ptr )
{
    while ( isspace( *ptr ) )
        ++ptr;

    return ( ptr );
}

/***************************************************************************
NAME:       read_field( FILE *fp, const char *field_name,
                         char *field_value )
INPUT:      fp            : file to read from
            field_name    : name of the field to be read
OUTPUT:     field_value   : value of the field
RETURN:     int           : 1 if successfull
                            0 otherwise
DESCRIPTION: Attempts to read the given field from the file.
             Note that the field value may have leading white-space.

---------------------------------------------------------------------------*/
static int read_field( FILE *fp, const char *field_name,
                       char *field_value )
{
    int    num_matched;
    char    format[80];

    /* The following sprintf command creates a format string for the scanf.
       Eg: If 'field_name' is "FOO", the format string would
       be " FOO:%[^\n]". This would be used to check for a line
       starting with "FOO:" and would read all the characters
       following the ':' until the end of line.  */

    sprintf( format, " %s:%%[^\n]", field_name );
    /* The space before the %s is important ! */

    num_matched = fscanf( fp, format, field_value );

    return ( num_matched == 1 );
}

/***************************************************************************
NAME:       ReadRoloEntry( FILE *fp, const char **ptr_name,
                           const char **ptr_addr, const char **ptr_phone )
INPUT:      fp          : file to read from
OUTPUT:     ptr_name    : the NAME field of the entry
            ptr_addr    : the ADDR field of the entry
            ptr_phone   : the PHONE field of the entry
RETURN:     int            : 0 if successfully read an entry
                            -1 on error or end of file
DESCRIPTION: Reads one entry (consisting of a name, address, and phone)
             from the file.
             The NAME field must appear in the file and must be the first
             of the three lines defining the entry.
             The ADDR and PHONE fields are optional but the ADDR field
             must precede the PHONE field if both exist.

             Note that the output parameter values will get overwritten
             the next time this function is called so they should be
             copied by the caller if they are supposed to persist.

---------------------------------------------------------------------------*/
int ReadRoloEntry( FILE *fp, const char **ptr_name, const char **ptr_addr,
                   const char **ptr_phone )
{
    int         status;
    static char name[MAX_LEN + 1],
                addr[MAX_LEN + 1],
                phone[MAX_LEN + 1];

    /* Set all buffers to the empty string */

    name[0] = '\0';
    addr[0] = '\0';
    phone[0] = '\0';
    status = -1;

    if ( read_field( fp, "NAME", name ) )
    {
        read_field( fp, "ADDR", addr );
        read_field( fp, "PHONE", phone );
        status = 0;
    }

    *ptr_name = skip_white_space( name );
    *ptr_addr = skip_white_space( addr );
    *ptr_phone = skip_white_space( phone );

    return ( status );
}

/***************************************************************************
NAME:   WriteRoloEntry( FILE *fp, const char *name, const char *addr,
                        const char *phone )
INPUT:  fp      : file to write to
        name    : the NAME field of the entry
        addr    : the ADDR field of the entry
        phone   : the PHONE field of the entry
OUTPUT:        ---
RETURN:        int        : 0 if successfully wrote the entry
                           -1 on error
DESCRIPTION: Writes one entry (consisting of name, address, and phone)
             to the file.
             Only non-empty fields are written to the file.

---------------------------------------------------------------------------*/
int WriteRoloEntry( FILE *fp, const char *name, const char *addr,
                    const char *phone )
{
    int status = -1;

    if ( name != NULL && name[0] != '\0' )
    {
        fprintf( fp, "NAME: %.*s\n", MAX_LEN, name );

        if ( addr != NULL && addr[0] != '\0' )
            fprintf( fp, "ADDR: %.*s\n", MAX_LEN, addr );

        if ( phone != NULL && phone[0] != '\0' )
            fprintf( fp, "PHONE: %.*s\n", MAX_LEN, phone );

        fprintf( fp, "\n" );

        status = 0;
    }

    return ( status );
}

#ifdef UNIT_TEST
/***************************************************************************
This 'main' function is for use in doing a unit-test of the above functions.
The basic idea of a unit-test is that each module should be tested in isolation
from the others.  When this module is used as part of a larger program,
this main is not used - hence it is ifdef'd out.
---------------------------------------------------------------------------*/
int    main( int argc, char *argv[] )
{
    FILE        *fp;
    const char  *name, *addr, *phone;
    const char  *rolofile = "rolo.txt";

    if ( argc > 1 )
        rolofile = argv[1];

    fp = fopen( rolofile, "r" );
    if ( fp == NULL )
    {
        fprintf( stderr, "Couldn't open %s\n", rolofile );
        exit( 1 );
    }

    while ( ReadRoloEntry( fp, &name, &addr, &phone ) != -1 )
    {
        WriteRoloEntry( stdout, name, addr, phone );
    }

    if ( fclose( fp ) != 0 )
        fprintf( stderr, "Couldn't close %s\n", rolofile );

    return ( 0 );
}
#endif /* UNIT_TEST */