sm-json

#!/usr/bin/perl -w

BEGIN{ push @INC, $ENV{'sm_path'}."/core/internal/perl"; }

use JSON -support_by_pp; # http://search.cpan.org/~makamaka/JSON-2.53/lib/JSON.pm

sub fail { print STDERR join(" ", @_)."\n"; exit 1; }

my (
  $path, $json_file, $json_file_handle, $json_object, $json, $key, $namespace,
  $hash, $subhash, $reference
);

$path      = shift(@ARGV);
$json_file = shift(@ARGV);

if( ! $path ) {
  fail "ERROR: A json path to extract must be given as the first argument\nexample: 'system/hostname'."
} elsif ( ! $json_file ) {
  fail "ERROR: A json file must be given as the second argument."
} elsif( ! -e $json_file ) {
  fail "ERROR: The json file $json_file does not exist!"
}

open($json_file_handle, '<', $json_file);
$json_string = join("", <$json_file_handle>);
close($json_file_handle);

$json_object = new JSON;
$json = $json_object->allow_nonref->utf8->relaxed->escape_slash->loose->allow_singlequote->allow_barekey->decode($json_string);

@_ = split("/", $path);
$key       = pop(@_);
$namespace = join("/", @_);
$hash      = $json;
$subhash   = {};

if($namespace) {
  foreach(split("/", $namespace)) {
    if(! $hash->{$_}) {
      exit 0 # No value.
    } elsif(exists $hash->{$_}) {
      # TODO: Question: Proper way to reassign the hash to it's subhash, this
      # works however I am not sure if there is an easier one liner that does
      # not involve a 2nd variable (subhash).
      $subhash = $hash->{$_};
      $hash = $subhash; # reassign the hash to the value of the current key (namespace).
    } else {
      fail "ERROR: Namespace ${namespace} missing under path '".join("/", $path)."'";
    }
  }
}

$reference = \$hash->{$key};

if (ref($reference) eq "SCALAR") {
  printf "%s\n", $hash->{$key};
} elsif (ref($$reference) eq "ARRAY") {
  print STDOUT join(" ", @{$hash->{$key}}) . "\n"; # TODO: Think this out a bit more.
} elsif (ref($hash->{$key}) eq "HASH") {
  # This allows for namespace querying to reflect on available keys.
  printf "%s\n", join(" ",keys(%{$hash->{$key}}));
} else {
  fail "ERROR: Key '$key' missing under namespace '$namespace' missing for path '$path'.";
}

exit 0; # Success!!!