Create deep hash mapping in perl - perl

Question

Below is my Code with the Hash
#!/usr/bin/perl
use warnings;
use JSON::PP; # Just 'use JSON;' on most systems
my %name = (
'sl' => {
'fsd' => {
'conf' => {
'ul' => '/sl/fsd/conf/ul',
'si' => '/sl/fsd/conf/si',
'ho1' => '/sl/fsd/conf/ho1'
}
}
},
're' => {
'fsd' => {
'cron' => {
'README' => '/re/fsd/cron/README'
},
'bin' => {
'db' => {
'smart.p_add_tag' => '/re/fsd/bin/db/smart.p_add_tag',
'smart.p_tag_partition' => '/re/fsd/bin/db/smart.p_tag_partition',
'smart.p_add_tag_type' => '/re/fsd/bin/db/smart.p_add_tag_type'
}
},
'doc' => {
'SMART' => '/re/fsd/doc/SMART',
'README' => '/re/fsd/doc/README'
},
'data' => {
'README' => '/re/fsd/data/README'
},
'conf' => {
'al1' => '/re/fsd/conf/al1',
'file' => '/re/fsd/conf/file',
'ho' => '/re/fsd/conf/ho',
'al3' => '/re/fsd/conf/al3',
'hst' => '/re/fsd/conf/hst',
'us' => '/re/fsd/conf/us',
'README' => '/re/fsd/conf/README',
'al2' => '/re/fsd/conf/al2'
}
}
}
);
(my $root) = keys %name;
my %nodes = ();
my %tree = ();
my #queue = ($root);
list_children(\%name, \#queue, \%nodes) while #queue;
my $tree = build_tree($root, \%nodes);
my $json = JSON::PP->new->pretty; # prettify for human consumption
print $json->encode($tree);
sub list_children {
my $adjac = shift;
my $queue = shift;
my $nodes = shift;
my $node = shift #$queue;
my #children = keys %{$adjac->{$node}};
#children = grep { ! exists $nodes->{$_}} #children;
$nodes->{$node} = \#children;
push #$queue, #children;
}
sub build_tree {
my $root = shift;
my $nodes = shift;
my #children;
for my $child (#{$nodes->{$root}}) {
push #children, build_tree($child, $nodes);
}
my %h = ('text' => $root,
'children' => \#children);
return \%h;
}
I'm trying to output JSONified hash, but it is only traversing upto two levels. whereas i need it to traverse all upto the last child node of each parent. Can someone please help to achieve this.
Below is current output
{
"text" : "sl",
"children" : [
{
"text" : "fsd",
"children" : []
}
]
}

Answer 1

Normally, transforming the hash, and then json-ing is not the most efficient idea, because you're going to make one traversal to transform the hash and JSON's going to make one to json-ify it, and JSON is a type of transform of a hash.
However, JSON is usually done with XS, which means that the second traversal is faster, at least. That and JSON behavior is standardized.
use 5.016;
use strict;
use warnings;
use Data::Dumper ();
use JSON;
my $hash
= {
'Foods' => {
'fruits' => {
'orange' => '1',
'apple' => '2',
},
'Vegetables' => {
'tomato' => '3',
'carrot' => '1',
'cabbage' => '2',
}
}
};
sub descend {
my ( $structure, $block ) = #_;
my $res;
while ( my ( $k, $v ) = each %$structure ) {
$block->( $structure, $k, $v );
if ( ref( $v ) eq 'HASH' ) {
$res = descend( $v, $block );
}
}
return $res;
}
my $new = {};
my $curr = $new;
descend( $hash => sub {
my ( $lvl, $k, $v ) = #_;
my $node = { text => $k };
$curr->{children} //= [];
push $curr->{children}, $node;
if ( ref( $v ) eq 'HASH' ) {
$curr = $node;
}
else {
$node->{children} = { text => $v };
}
});
# allow for the root-level special case, and retrieve the first child.
$new = $new->{children}[0];
say Data::Dumper->Dump( [ $new ], [ '$new' ] );
say JSON->new->encode( $new );