/* --------------------------------------------------------------------- 
**  Selection Sort
**  Figure 16.15: Main program for sorting.
**  Figure 16.9:  (Modified) Reading the data from a file.  
**  Figure 16.17: Writing the data to a file.  
**  Figure 16.18: Sorting by selecting the minimum.
**  Figure 16.21: Finding a minimum element.
** --------------------------------------------------------------------- 
*/
#include "tools.h" 

#define LENGTH 20   

int read_file( float x[], int nmax ); 
void sort_data( float data[], int n );    
void write_file( float data[], int n );   

void main( void ) 
{  
    int n;                       /* # of data items; will be <=LENGTH. */ 
    float data_list[LENGTH];     /* An array for the data to be sorted. */  

    banner();
    n = read_file( data_list, LENGTH );

    printf( " %i items were read; beginning to sort.\n", n );   
    sort_data( data_list, n );   

    puts( " Data sorted, ready for output" );
    write_file( data_list, n );  
    bye();  
}           

/* ------------------------------------------------------------------------ */
int 
read_file( float x[], int nmax)
{      
    int k;                      /* subscript variable for loop */              
    char infile[80];            /* name of input file */
    stream fin;                 /* stream for input file */
    int flag;                   /* for fscanf() return value */

    printf( " Name of input file: " );  
    scanf( " %79[^\n]", infile );        
    fin = fopen( infile, "r" );
    if (fin == NULL) fatal( "\n Fatal error: cannot open %s", infile );
    printf( " Reading data from %s.\n", infile );  

    for (k = 0; k < nmax; ) {       /* Don't read beyond end of data array. */
        flag = fscanf( fin, "%g", &x[k] );      
        if (flag == 1) ++k;         /* all is well -- count the item. */ 
        else if( feof(fin) ) break; /* no more data is available. */
        else {                      /* bad data -- note, skip, & continue. */
            say( " ---  Bad data while reading slot %i: ", k );
            clean_and_log( fin, stderr );
        }
    }
    fclose( fin ); 
    return k;  
}

/* ------------------------------------------------------------------------ */
void 
write_file( float data[], int n )
{      
    int k;                              /* Subscript variable for loop. */   
    stream fout;
    char filename[80];

    printf( " Name of output file: " );
    scanf( " %79[^\n]", filename );          
    fout = fopen( filename, "w" );    
    if (fout == NULL) fatal( " Fatal error: cannot open %s.", filename ); 

    for (k = 0; k < n; ++k) {           /* Don't print beyond end of data. */
        fprintf( fout, " %7.2f\n", data[k] );
    }
    fclose( fout );
}

/* ------------------------------------------------------------------------ */
void 
sort_data( float data[], int n )   
{
    int find_min( float data[], int begin, int n );  
    int start, where;
    float smallest;

    for (start = 0; start < n - 1; ++start) {
        where = find_min( data, start, n );
        smallest = data[where];
        data[where] = data[start]; 
        data[start] = smallest; 
    }   
}

/* ------------------------------------------------------------------------ */
int 
find_min( float data[], int begin, int n ) 
{ 
    int finger = begin;
    int cursor;  
    for (cursor = begin + 1; cursor < n; ++cursor) {  
        if (data[cursor] < data[finger]) finger = cursor;
    }
    return finger;
}