#include "quiz.h"

extern struct thai_phrase *random ();


random_sentence ()
{
	chosen_sentence = random ( &sentence_head );
}


random_word ()
{
	chosen_word = random ( &word_head );
}


static
struct thai_phrase *
random ( head )
struct thai_phrase *head;
{
	long dist ();

	long count;
	long total_right;
	long total_wrong;
	long num;
	static long seed = 0;
	struct thai_phrase *p;
	ULONG seconds , micros;

	if ( head->next == NULL )
		return ( head );
	total_right = 0;
	total_wrong = 0;
	count = 0;
	for ( p = head->next; p != NULL; p = p->next ) {
		total_right += p->right;
		total_wrong += p->wrong;
		count++;
	}
	CurrentTime ( &seconds , &micros );
	seed += seconds + micros + 1234567;
	num = ( seed & 0x7FFF ) % ( count + dist ( total_wrong , total_right ) );
	for ( p = head->next; p != NULL; p = p->next ) {
		num -= dist ( (long)p->wrong , (long)p->right ) + 1;
		if ( num < 0 )
			return ( p );
	}
	return ( head->next );
}


static long
dist ( wrong , right )
long wrong , right;
{
	if ( wrong > right )
		return ( wrong - right );
	return ( 0 );
}