#!/usr/bin/perl -w

# program name: distanace.pl
#
# This program calculates the distance between any two botswana towns
# It requires that two source files towns.txt and distance.txt be in the same
# directory as this program
#
# First experiment with this program by supplying it with towns that are listed
# in towns.txt.
#
# Adapt this code to suit your asnwers to the question in assigment 2
# Warning: There is no validation corrections or subroutines, it is upto you
# to make sure you adapt this code to suit your solution.
#
# towns.txt format: town id|town name|location eg. 28|Ramatlabama|B
# Distance.txt format:
#    This is a row-by-column table that stores distances between any pair
#    of towns. When distance is worked out, start with the smaller Town ID
#    as a row (or file line number in terms of script programming),
#    and a bigger number as a column (use normal array subscripts for rows).
#    There are 42 towns in all, this translates into a 42X42 table. Note that
#    these are true distances, not dummy values.
#
# STEPS:
#
# Step 1;
# =======
#
# Get two town names as input (from keyboard or file)
#
# Step 2:
# ========
#
# Work out the town codes from using towns.txt
#
# Step 3:
# =======
#
# Use the two town codes and distance.txt to determine the distance between them
#
# Author: Dr. Dimane Mpoeleng, Computer Science, CSI423
#
################################################################################


# Get two towns from the keyboard

print "Type town 1:";
$town1=<STDIN>;
chomp ($town1);

print "Type town 2:";
$town2=<STDIN>;
chomp($town2);


###########################
# Work out the town codes
###########################

open (TOWNS, "< towns.txt");

$town1code=999;     # dummy values
$town2code=999;

while ($line=<TOWNS>)
{
  chomp($line);

  ($code, $town, $loc) = split(/\|/,$line);

  if ($town eq $town1)
  {
     $town1code = $code;
  }
  if ($town eq $town2)
  {
     $town2code = $code;
  }
  $loc=""; # do something with location so the compiler won't complain
}

close (TOWNS);

######################################
# Work out the distance between codes
######################################

#Remember how I warned you on how best to work out distance from the table? Read
# Section 4.3 here: http://168.167.14.30/teaching/csi423/csi423_assignment2.htm
#
# When distance is worked out, start with the smaller Town ID as a row (or file
# line number in terms of script programming), and a bigger number as a column
# (use normal array subscripts for rows). There are 42 towns in all, this
# translates into a 42X42 table. Note that these are true distances, not dummy
# values.
#
#For example if the distance between Jwaneng (town1code = 8) and Francistown
# (town2code = 3) is to be worked, 3 should be treated as a row and 8 as a
# column to get 628 km. However swapping 8 and 3 by treating 8 as a row and 3
# as a column would yield xxxx.
#
# see how the table looks like here :
#
#         http://168.167.14.30/teaching/csi423/distancetable.txt
###########################################


open (DISTANCE, "< distancetable.txt");

@DistanceArray=<DISTANCE>;   # the array will contain all lines of distance.txt
                             # row by row unsplit, so each line has to be split

# take out the row that matches the smaller towncode!
# start with a small ID as a row then the bigger towncode as a column

$row="";    # initialise row

if ($town1code < $town2code)
{
  $smallercode=$town1code;
  $biggercode =$town2code
}
else
{
  $smallercode=$town2code;
  $biggercode =$town1code      # note: town code start at 1, not 0, so we
}                                         # have already avoided reading in town
                                          # labes of distancetable.txt

$row=$DistanceArray[$smallercode];

chomp($row);    # remove newline

# now split the row into an array.

@RowArray=split(/\|/, $row);

#get the distance

$distance = $RowArray[$biggercode];


print "the two towns are   : [$town1] and [$town2]\n";
print "their codes are     : [$town1code] and [$town2code]\n";
print "distance between is : [$distance km]\n";