/* Fraction calculator

   29 September 2023, by Ruud Harmsen

   Input, stdin, on a line of text:
   Four integers, separated by whitespace, except that between the first
   and second pair, there must be (optionally surrounded by white space)
   one of the characters in [*x/:]. The first two mean multiplication,
   the second ones indicate division.

   On return/enter, the result is shown, also a fraction, the smallest one
   possible. Then on the next line the same in cents (1200 cents = 1 octave).

   If the first pair of numbers is missing, the previous result is used,
   which initially is 1:1.

   Leaving out the operator, that is, just typing 4 numbers, is also allowed,
   in which case the default is division.

   The program loop can be stopped by typing a letter q (quit) or e (exit)
   at the start of the line.

   2 October 2023:
   Program now also supports addition and subtraction.
 */

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include "../../rhmusicfuncs/rhmusicfuncs.h"

LLI opA_numer, opA_denom, opB_numer, opB_denom;
LLI w_opA_numer, w_opA_denom, w_opB_numer, w_opB_denom;
LLI res_numer, res_denom;
char operat[2] = "/";

void Calculate (void);
void CalculutePlMn (void);
void ReportResults (void);

int main (void)
{
   char line[81];
   int ret = 0;

   opA_numer = opA_denom = opB_numer = opB_denom = res_numer = res_denom = 1;
   while (fgets(line, sizeof line, stdin))
   {
      ret = sscanf(line, " %1[*x/:+-] %lld %lld ", operat, &opB_numer, &opB_denom);
      if (ret != 3)
         ret = sscanf(line, " %lld %lld %1[*x/:+-] %lld %lld ",
            &opA_numer, &opA_denom, operat, &opB_numer, &opB_denom);

      if (ret != 5)
      {
         ret = sscanf(line, " %lld %lld %lld %lld ",
            &opA_numer, &opA_denom,&opB_numer, &opB_denom);
         if (ret == 4)
            operat[0] = '/';
      }
      if (ret != 4 && (line[0] == 'q' || line[0] == 'e'))
         break;

      Calculate();
      ReportResults();

      /* Set default operand A: the previous result unless
         otherwise specified. */
      opA_numer = res_numer;
      opA_denom = res_denom;
   }

   return 0;
}

void Calculate (void)
{
   LLI thisGcd;

   if (*operat == ':') *operat = '/';
   if (*operat == 'x') *operat = '*';
   if (*operat == '+' || *operat == '-')
   {
      CalculutePlMn();
   }
   if (*operat != '/' && *operat != '*')
      return; /* Silently refuse to do anything. */

   /* Division is equivalent to multiplication by the inverse value */
   w_opB_numer = *operat == '*' ? opB_numer : opB_denom;
   w_opB_denom = *operat == '*' ? opB_denom : opB_numer;

   res_numer = opA_numer * w_opB_numer;
   res_denom = opA_denom * w_opB_denom;

   /* Safety first, no division by zero */
   if (res_numer == 0) res_numer = 1;
   if (res_denom == 0) res_denom = 1;

   thisGcd = gcd(res_numer, res_denom);
   res_numer /= thisGcd;
   res_denom /= thisGcd;
}

void CalculutePlMn (void)
{
   LLI thisGcd;

   thisGcd = gcd(opA_denom, opB_denom);
   w_opA_denom = w_opB_denom = opA_denom * opB_denom / thisGcd;
   w_opA_numer = opA_numer * w_opA_denom / opA_denom;
   w_opB_numer = opB_numer * w_opB_denom / opB_denom;
   if (*operat == '+')
      res_numer = w_opA_numer + w_opB_numer;
   else /* minus */
      res_numer = w_opA_numer - w_opB_numer;
   res_denom = w_opA_denom;

   thisGcd = gcd(llabs(res_numer), res_denom);
   res_numer /= thisGcd;
   res_denom /= thisGcd;
}

void ReportResults (void)
{
   if (*operat == '*' || *operat == '/')
   {
      /* Report result */
      printf("%3lld:%-3lld %s %3lld:%-3lld = %3lld:%-3lld\n",
         opA_numer, opA_denom, operat, opB_numer, opB_denom,
         res_numer, res_denom);
      printf("%6.1f  %c %6.1f  = %6.1f\n",
         rats2cents(opA_numer, opA_denom),
         *operat == '/' ? '-' : '+',
         rats2cents(opB_numer, opB_denom),
         rats2cents(res_numer, res_denom));
   }
   else
   {
      printf("%3lld:%-3lld %s %3lld:%-3lld = %3lld:%-3lld %s %3lld:%-3lld = %3lld:%-3lld\n",
           opA_numer,   opA_denom, operat,   opB_numer,   opB_denom,
         w_opA_numer, w_opA_denom, operat, w_opB_numer, w_opB_denom,
         res_numer, res_denom);
   }
}