#!/usr/local/bin/perl

#
# this program demonstrates hash autovivification as described in
# Chatper 5, "References and Scoping" of "Intermediate Perl, 2nd Edition"
# https://www.oreilly.com/library/view/learning-perl-objects/0596004788/ch04.html
#
# it also experiements with some ways to print complex data structures using
# various modules such as Data::Dumper, JSON and YAML.
#

use strict;
use warnings;
use v5.22;
use Data::Dumper;
use Data::Dump qw(dump);
use Data::Printer;
use YAML;
use JSON;

my %total_bytes;

die "Usage: $0 [filename]" if (@ARGV != 1);
my $filename = shift;
open my $fh, '<', $filename 
    or die "Could not open file $filename: $!";

while (<$fh>) {
    my ($source, $destination, $bytes) = split;
    $total_bytes{$source}{$destination} += $bytes;
    #print Dumper( \%total_bytes );
}

my @column_width = (23, 23, 16);
my $format = "%-23s %-23s %16d\n";
#my $format = sprintf "%-*s %-*s %*d\n", foreach @column_width;
say "===========START OF REPORT==============";
printf "%-23s %-23s %-16s\n", "Source", "Destination", "Bytes Transfered";
printf "%-23s %-23s %-16s\n", "-"x23, "-"x23, "-"x16;
for my $source (sort keys %total_bytes) {
    for my $destination (sort keys %{ $total_bytes{$source} }) {
        printf $format, $source, $destination,
            $total_bytes{$source}{$destination};
    }
}
say "===========START of DUMPER===============";
print Dumper( \%total_bytes );  # this one is the best
#say "+++++++++++++++++++++++++++++++";
#dump( \%total_bytes);
#say "+++++++++++++++++++++++++++++++";
#p( %total_bytes);
#say "===========START of DUMP=================";
#print Dump( \%total_bytes );
#say "+++++++++++++++++++++++++++++++";
say "===========START of JSON=================";
print to_json( \%total_bytes, { pretty => 1 } ); # not bad
say "===========END of JSON===================";
my $json_in = to_json( \%total_bytes, { pretty => 1 } );
say "--------should be same as before-----------";
say $json_in;
$json_in = "[\n".$json_in."]";
say "----------not sure what this is-------------";
say $json_in;
my $hash_ref = from_json( $json_in ); # this actually an array ref now that
# we added the opening and closing brackets above

#for my $s (sort keys %{$hash_ref}) {
#    say $s;
#}
say "============start of final report==========";
foreach (@$hash_ref) {
    for my $s (keys %{$_}) {
        say $s;
    }
}