#!/bin/sh

# PAIR - a simple matching game, implmemented as a linear array

# Usage: PAIR rowcount
#    note: rowcount must be even and specifies how many 13-slot rows are created
#    default value is 2 rows of 13 values

declare -a board 
declare -a letters=(A B C D E F G H I J K L M N O P Q R S T U V W X Y Z)
rows=4			# default # of 13 slot rows

initialize ()
{
   # given number of rows, initialize the board with all blank values

   count=1   maxcount=$1

   while [ $count -le $maxcount ]
   do
     addon=$(( 13 * ( $count - 1 ) ))
 
     for slot in {1..13}
     do
       index=$(( $addon + $slot )) 
       letter=$(( $index % 26 )) 	# unshuffled value

       board[ $index ]="-${letters[$letter]}"	# unguessed start with '-'
     done
     count=$(( $count + 1 ))
   done
}

shuffle ()
{
   # given the board[] array with $1 * 13 entries, shuffle the contents

   totalvalues=$(( $1 * 13 ))

   index=$totalvalues

   while [ $index -gt 1 ] ; do

     randval=$(( ( $RANDOM % $index ) + 1 ))
 
     # swapping value pair

     temp=${board[$index]}
     board[$index]=${board[$randval]}
     board[$randval]=$temp

     index=$(( $index - 1 ))
   done
}

showgrid ()
{
   # show our grid. This means we need to display $1 x 13 slots with labels
   #     rows is grabbed from the global var 'rows'

   count=1

   echo "    1   2   3   4   5   6   7   8   9   10  11  12  13"

   while [ $count -le $rows ]
   do 
     /bin/echo -n "$count: "
     addon=$(( 13 * ( $count -1 ) ))

     for slot in {1..13}
     do
       index=$(( $slot + $addon ))
       value=${board[$index]}
       if [ ${value:0:1} != '-' ] ; then   # matched!
         /bin/echo -n "<${board[$index]}> "
       else
         /bin/echo -n "<-> "     # still unknown
       fi
     done
     echo ""
     count=$(( $count + 1 ))
   done
}

##################################

if [ $# -gt 0 ] ; then
  rows=$1
fi

if [ $(( $rows % 4 )) -ne 0 ] ; then
  echo "Ooops! Please only specify a multiple of 4 as the number of rows (4, 8, 12, etc)"
  exit 1
fi

slot1=slot2="X"			# start with a non-empty value
unsolved=$(( $rows * 13 ))
maxvalues=$unsolved		# parameter testing

echo "Welcome to PAIRS. Your mission is to identify matching letters in the grid."
echo "Good luck. If you give up at any point, just use q to quit."
echo ""

initialize $rows

shuffle $rows

showgrid

while [ $unsolved -gt 0 ] ; do
  echo ""
  /bin/echo -n "Enter a pair of values in row,col format : "
  read slot1 slot2

  if [ "$slot1" = "" -o "$slot2" = "" ] ; then
    echo "bye." 
    exit 1
  fi

  row1=$( echo $slot1 | cut -c1 )
  col1=$( echo $slot1 | cut -d, -f2 )
  row2=$( echo $slot2 | cut -c1 )
  col2=$( echo $slot2 | cut -d, -f2 )

  index1=$(( ( $row1 - 1) * 13 + $col1 ))
  index2=$(( ( $row2 - 1) * 13 + $col2 ))
 
  if [ $index1 -lt 0 -o $index1 -gt $maxvalues -o $index2 -lt 0 -o $index2 -gt $maxvalues ] ; then
    echo "bad input, not a valid value"
    exit 1
  fi

  val1=${board[$index1]}
  val2=${board[$index2]}

  if [ $val1 = $val2 ] ; then
    echo "You've got a match. Nicely done!"
    board[$index1]=${val1:1:1}
    board[$index1]=${val2:1:1}
    unsolved=$(( $unsolved - 2 ))
  else
    echo "No match, but $row1,$col1 = ${val1:1:1} and $row2,$col2 = ${val2:1:1}."
  fi

  echo ""
  showgrid

done

exit 0