#include <stdlib.h> /* rand() and friends */
#include <time.h>
#include <string.h>
#include <stdio.h> /* sprintf() */
#include <sqlite3.h>

/**
   A simple example of writing a custom SQL function for sqlite3.

   It provides results of a so-called Fudge-dice roll. Fudge dice (dF)
   are used by the Fudge roleplaying system (http://fudgerpg.com).

   Call it with 0, 1 or 2 arguments:

   0 args: same as calling dF(4).

   1 arg: arg1 is an integer telling how many dice to roll.

   2 args: arg2 is any value. The TYPE of the value is used to
   dynamically set the return type. If arg2 is an INTEGER (the
   default) or DOUBLE then a number of the appropriate type is
   returned to the caller via sqlite_result_xxx(context,...). If arg2
   is a string then a description showing the results of each die roll
   of the set, plus the total, is sent back.

   You may bind this function to your db by calling something like:

   sqlite3_create_function( myDb, "dF", -1, SQLITE_ANY, 0, sqlite_func_dF, 0, 0 );

   Author: stephan at wanderinghorse dot net

   License: Public Domain
*/
void sqlite_func_dF(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv )
{
    static char seeded = 0;
    enum {BufLen = 128};
    char buf[BufLen+1] = {0};
    char * bPos = buf;
    int count = 0;
    int returnT;
    int reti = 0;
    if( !seeded && (seeded=1) ){
        srand( time(NULL) );
    }

    if( argc > 2 ){
        sqlite3_result_error( context,
                              "dF() function requires 0, 1, or 2 arguments: "
                              "(0==roll 4dF and return int), "
                              "(1==roll [ARG0]dF and return int), "
                              "(2=roll [ARG0]dF and return result as TYPEOF(ARG1))",
                              -1 );
        return;
    }

    returnT = (argc<2) ? SQLITE_INTEGER : sqlite3_value_type(argv[1]);
    if( 0 == argc ){
        count = 4;
    }
    else{
        count = sqlite3_value_int(argv[0]);
        if( count < 1 ) count = 4;
    }
    if(count > BufLen/2+20){
        sqlite3_result_error( context, "dF() can't buffer that many dice.", -1 );
        return;
    }
    
    if( SQLITE_TEXT == returnT ){
        /*bPos += sprintf(bPos, "dF: ");*/
    }
    {
        int rnd;
        char marker;
        while( count-- ){
            rnd = rand() % 3 - 1;
            if( SQLITE_TEXT == returnT ) {
                marker = ((0==rnd) ? '0' : ((rnd>0) ? '+' : '-'));
                *bPos++ = marker;
                *bPos++ = ' ';
            }
            reti += rnd;
        }
    }
    if( SQLITE_TEXT == returnT ){
        bPos += sprintf(bPos, "= %d", reti);
        *bPos = 0;
        sqlite3_result_text( context, buf, strlen(buf), SQLITE_TRANSIENT );
    }
    else if( SQLITE_FLOAT == returnT ){
        sqlite3_result_double(context, 1.0 * reti);
    }
    else{
        sqlite3_result_int(context, reti);
    }
    return;
}