/* ------------------------------------------------------------------------ 
//   This program reads a set of quiz questions from a file and presents  
//      them to a user in random order.  The shuffle algorithm does random   
//      selection without replacement.                                       
// ------------------------------------------------------------------------ 
*/
#include "tools.h"           /* include commands and user defined utilities */ 

/* ---- Questions and answers --------------------------------------------- */
#define MAXQ    20              /* Maximum number of questions in the quiz. */
typedef struct { short number; char name[16]; char symbol[4]; } question_t;

int get_quiz( int n, question_t qu[] );
int do_quiz( int k, question_t quiz[] );

void main( void )                                                                  
{   
    question_t quiz[MAXQ];  /* Array of questions and answers.  */
    int nq;                 /* Number of questions in the quiz. */
    int right;              /* Number of correct answers. */

    banner();
    printf( "\n Chemical Element Quiz\n" );

    nq = get_quiz( MAXQ, quiz );   /* Read nq quiz questions from a file. */
    printf( "\n This quiz has %i questions.\n", nq );
    printf( " When you see an element name, enter its symbol and number.\n" );

    right = do_quiz( nq, quiz );
    printf( "\n You gave %i correct answers on %i questions.\n", right, nq );

    bye();
}

/* ----------------------------------------------------------------------------- */
int 
get_quiz( int n, question_t qu[] )
{   
    char filename[256];         /* Name of input file holding questions. */
    stream fin;                 /* Input stream for questions. */  
    int items;                  /* For the code returned by fscanf(). */
    int k;                      /* Number of questions in the quiz. */

    printf( "\n What quiz file do you want to use? " );
    scanf ( "%255s", filename );
    fin = fopen ( filename, "r" );
    if (fin == NULL) fatal ( " Error: cannot open file %s", filename );
    
    for (k = 0; k < n; ) {
        items = fscanf( fin, "%hi%15s%3s", &qu[k].number, qu[k].name, qu[k].symbol );
        if (items == 3) ++k;                   /* all is well -- count the item. */
        else if (feof( fin )) break;
        else {
            say( " Bad data while reading slot %i: ", n );
            clean_and_log( fin, stderr );
        }
    }
    return k;
}

/* ------------------------------------------------------------------------------- */
int 
do_quiz( int nq, question_t quiz[] )
{   
    bool ask( question_t q );   /* Prototype for subfunction. */

    int many = nq;              /* Number of questions not yet asked. */ 
    int score = 0;              /* Number of correct answers so far. */ 
    int k;                      /* Subscript of selected question. */

    srand( time( NULL ) );      /* initialize random number generator. */

    while (many > 0) {
        k = rand() % many;      /* Choose subscript of next question. */
        if( ask( quiz[k] ) ){
            score++;
            printf( "\t YES !  Score one.\n" );
        }
        else {
            printf( "\t Sorry, the answer is %s %hi \n", 
                     quiz[k].symbol, quiz[k].number );
        }

        /* Now remove the question from further consideration. */ 
        --many;                 /* Decrement the counter.    */
        quiz[k] = quiz[many];   /* Move last question into vacant slot. */
    }
    return score;
}

/* ----------------------------------------------------------------------------------- */
bool ask( question_t qu )
{
    char symb[4];               /* User response for atomic symbol. */
    short number;               /* User response for atomic number. */

    printf( "\n Element: %s\n", qu.name );          
    printf( "\t symbol ? ");            
    scanf( "%3s", symb );
    printf( "\t atomic number ? ");         
    scanf( "%hi", &number );
        
    return strequal( symb, qu.symbol ) && number == qu.number;
}