#!/usr/bin/perl

use warnings;
use strict;
use JSON;
use Getopt::Long;
use File::Which;
use Data::Dumper;

my $what = 'containers';
my $pretty = 0;

GetOptions(
  'what=s' => \$what,
  'pretty' => \$pretty
);

my $json = [];

my $docker = which('docker');

# If the docker cli is not available, terminate now
if (not defined $docker){
  print $json . "\n";
  exit(0);
}

my $format;
my $cmd;
if ($what =~ m/^containers?/){
  $format = '{' .
               '"{#DOCKER_CONTAINER_ID}":"{{ .ID }}",' .
               '"{#DOCKER_CONTAINER_IMAGE}": "{{ .Image }}",' .
               '"{#DOCKER_CONTAINER_NAME}":"{{ .Names }}",' .
               '"{#DOCKER_CONTAINER_STATE}": "{{ .State }}"' .
               '}';
  $cmd = "$docker container list --all --format '$format'";
} elsif ($what =~ m/^networks?/){
  $format = '{' .
            '"{#DOCKER_NET_ID}":"{{ .ID }}",' .
            '"{#DOCKER_NET_NAME}":"{{ .Name }}",' .
            '"{#DOCKER_NET_DRIVER}":"{{ .Driver }}",' .
            '"{#DOCKER_NET_SCOPE}":"{{ .Scope }}"' .
            '}';
  $cmd = "$docker network list --format '$format'";
} elsif ($what =~ m/^volumes?/){
  $format = '{' .
            '"{#DOCKER_VOL_NAME}":"{{ .Name }}",' .
            '"{#DOCKER_VOL_DRIVER}":"{{ .Driver }}",' .
            '"{#DOCKER_VOL_SCOPE}":"{{ .Scope }}"' .
            '}';
  $cmd = "$docker volume list --format '$format'";
} else {
  print <<_EOF
Usage: $0 --what=<item to discover> [--pretty]
with available item being
  * containers : list containers, including stopped ones
  * networks : list networks
  * volumes : list volumes
_EOF
}

foreach my $line (qx($cmd)){
  chomp $line;
  push @{$json}, from_json($line);
}
print to_json($json, { pretty => $pretty }) . "\n";
exit(0);