#!/bin/bash

## dice rolling prototype
## input arg examples
## 3 sided 4 dice: 3d4
## 6 sided 7 dice: 6d7
## add 3 to total: +6
## sub 5 from tot: -5
##### SPECIAL CASE #####
## 10 sided 2 dice produces percentages


# a test to make sure a variable is a number
int_test() {
  [ -n "$1" ]                   &&
  [ "$1" -eq "$1" 2>&- ]
}


read INPUT
TOTAL=0
for WORD in ${INPUT[@]} ; do       #Grab an argument
  {
    [ "${WORD%%[-,+]*}" = "" ]  && #Start with a + or - ??
    EXTRA="${WORD#[-,+]}"       && #Get the number
    int_test $EXTRA             &&
    {
      [ "${WORD%%+*}" = "" ]    && #Is it positive ??
      {
        TOTAL=$(( TOTAL + EXTRA ))
        echo "ADD: $EXTRA"
      } || {                       #Must be negative
        TOTAL=$(( TOTAL - EXTRA ))
        echo "SUB: $EXTRA"
      }
    }
  } && continue || {               #Continue to the next arg ??
    SIDES=${WORD%%[d,D]*}
    DICE=${WORD#$SIDES[d,D]}
    int_test "$SIDES"           &&
    int_test "$DICE"
  } && {                           #Correct format ??
    [ $SIDES -eq 10 ]           && #Percentage special case ??
    [ $DICE  -eq 2  ]           &&
    {
      ROLL=$(( RANDOM % SIDES ))
      ROLL2=$(( RANDOM % SIDES ))
      echo "PERCENT: $ROLL$ROLL2%"
    } || {                         #Roll the dice!!
      CNT=1 ; SUB_TOT=0
      echo "SIDES: $SIDES"
      while [ $DICE -ge $CNT ] ; do
        ROLL=$(( (RANDOM % SIDES)+1 ))
        SUB_TOT=$(( SUB_TOT + ROLL))
        echo " $CNT $ROLL"
        CNT=$(( CNT + 1 ))
      done
      echo "SUB TOT: $SUB_TOT"
    }
  }                             &&
   TOTAL=$(( TOTAL + SUB_TOT )) ||
   echo "ERROR: $WORD"             #Must have been a bad arg
done
echo "TOTAL: $TOTAL"