#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

use constant BASE_DIR => '/home/ken/tmp/pm_11143050';
use constant {
    LEN_BASE_DIR => length BASE_DIR,
    FS_DIR => BASE_DIR . '/fs',
};

use Cwd 'abs_path';
use Data::Dump;

my %fs_map;
walk_fs(FS_DIR, \%fs_map);
dd \%fs_map;

sub walk_fs {
    my ($path, $fs_map) = @_;

    opendir(my $dh, $path);

    while (readdir $dh) {
        next if /^\.{1,2}$/;
        my $entry = "$path/$_";
        my $fs_path = fs_path($entry);

        if (-f $entry) {
            $fs_map->{$fs_path} = [file => []];
        }
        elsif (-l $entry) {
            $fs_map->{$fs_path} = [link => [canon_path($entry)]];
        }
        elsif (-d $entry) {
            if (exists $fs_map->{fs_path($path)}) {
                push @{$fs_map->{fs_path($path)}[1]}, canon_path($entry);
            }

            $fs_map->{$fs_path} =  [dir => []];

            walk_fs($entry, $fs_map);
        }
        else {
            warn "IGNORED '$entry': not a plain file, link or directory.\n";
        }
    }

    closedir $dh;

    return;
}

sub fs_path {
    return substr $_[0], LEN_BASE_DIR;
}

sub canon_path {
    return substr abs_path($_[0]), LEN_BASE_DIR;
}

##</code><code>##

ken@titan ~/tmp/pm_11143050
$ ls -lR fs
fs:
total 0
drwxr-xr-x+ 1 ken None 0 Apr 19 03:49 a
drwxr-xr-x+ 1 ken None 0 Apr 19 02:46 t

fs/a:
total 1
prw-rw-rw-  1 ken None 0 Apr 19 03:49 a_named_pipe
drwxr-xr-x+ 1 ken None 0 Apr 19 02:46 b
-rw-r--r--  1 ken None 0 Apr 19 02:36 d
lrwxrwxrwx  1 ken None 5 Apr 19 02:42 r -> b/c/z
drwxr-xr-x+ 1 ken None 0 Apr 19 02:46 u
lrwxrwxrwx  1 ken None 8 Apr 19 02:35 x -> ../a/b/c

fs/a/b:
total 0
drwxr-xr-x+ 1 ken None 0 Apr 19 02:46 c
-rw-r--r--  1 ken None 0 Apr 19 02:37 e
lrwxrwxrwx  1 ken None 1 Apr 19 02:40 q -> y
drwxr-xr-x+ 1 ken None 0 Apr 19 02:46 v
lrwxrwxrwx  1 ken None 1 Apr 19 02:37 y -> .

fs/a/b/c:
total 0
-rw-r--r--  1 ken None 0 Apr 19 02:38 f
lrwxrwxrwx  1 ken None 7 Apr 19 02:40 p -> ../../x
drwxr-xr-x+ 1 ken None 0 Apr 19 02:46 w
lrwxrwxrwx  1 ken None 6 Apr 19 02:38 z -> ../../

fs/a/b/c/w:
total 0

fs/a/b/v:
total 0

fs/a/u:
total 0

fs/t:
total 0

##</code><code>##

ken@titan ~/tmp/pm_11143050
$ ./mapfs.pl
IGNORED '/home/ken/tmp/pm_11143050/fs/a/a_named_pipe': not a plain file, link or directory.
{
  "/fs/a"       => ["dir", ["/fs/a/b", "/fs/a/u"]],
  "/fs/a/b"     => ["dir", ["/fs/a/b/c", "/fs/a/b/v"]],
  "/fs/a/b/c"   => ["dir", ["/fs/a/b/c/w"]],
  "/fs/a/b/c/f" => ["file", []],
  "/fs/a/b/c/p" => ["link", ["/fs/a/b/c"]],
  "/fs/a/b/c/w" => ["dir", []],
  "/fs/a/b/c/z" => ["link", ["/fs/a"]],
  "/fs/a/b/e"   => ["file", []],
  "/fs/a/b/q"   => ["link", ["/fs/a/b"]],
  "/fs/a/b/v"   => ["dir", []],
  "/fs/a/b/y"   => ["link", ["/fs/a/b"]],
  "/fs/a/d"     => ["file", []],
  "/fs/a/r"     => ["link", ["/fs/a"]],
  "/fs/a/u"     => ["dir", []],
  "/fs/a/x"     => ["link", ["/fs/a/b/c"]],
  "/fs/t"       => ["dir", []],
}