#!/usr/software/bin/perl
# Example 2 - To get URLs in parallel when they are stored in a file.
use Parallel::ForkManager;
use LWP::Simple;

my $heredoc = <<ENDS;
# =============================================================== #
# ERROR: Missing arguments. See usage below.
# Usage: perl $0
#   E.g. perl $0 10 FB_inputFile.txt
# Author: suresh.saggar\@gmail.com
# =============================================================== #
ENDS

if($#ARGV != 1){
    printf $heredoc;
    exit;
}

my $num_of_processes = $ARGV[0];
# Create a file handle
open FH, "$ARGV[1]" or die "Cannot open filename[$filename]:$!\n";

my @URLs = undef;
chomp(@URL = ); # trim trailing spaces.

my $pm = new Parallel::ForkManager($num_of_processes);

#
# Setup a callback for when a child finishes up so we can get it's exit code
#
$pm->run_on_finish(
    sub {
        my ($pid, $exit_code, $ident) = @_;
        print "** ID[$ident] just got out of the pool with PID[$pid] and exit code[$exit_code] \n";
    }
);

$pm->run_on_start(
    sub {
        my ($pid, $ident)=@_;
        print "** ID[$ident] started with PID[$pid] \n";
    }
);

$pm->run_on_wait(
    sub {
        print "** Have to wait for one children ...\n"
    },
    0.5
);

my $id = 0;

for my $link (@URL) {
    $pm->start($id++) and next;
    my ($fn) = $link =~ /^.*\/(.*?)$/;
    if (!$fn) {
        warn "Cannot determine filename[$fn] from link[$link]\n";
        warn "Make sure you prefix each URL with http(s):/\/\ \n";
    } else {
        $0 .= " ".$fn;
        print "Getting [$fn] from [$link]\n";
        my $rc = getstore($link, $fn);
        print "[$link] downloaded. response code:[$rc]\n";
    };
    $pm->finish;

};

# Close the file handle
close FH;

print "Waiting for Children...\n";
$pm->wait_all_children;
print "Everybody[$num_of_processes] is out of the pool!\n";