#!/usr/bin/perl

##### FUNCTION
# To read ip settings from a machine generated file and
# write those ip settings to the dhcpcd.conf file.
#  This script is designed to be started by a systemd service.path
#  The service monitors the mb_ip.cfg file for change.  When the file is changed
#  the service calls this script.
#  Updated ip settings are applied after reboot.

##### INPUT
#  Takes user updates of IP settings saved in to the file /home/mimir/mb_ip.cfg
#  The user setting are range checked by the app before being saved to file.
#  The file mb_ip.cfg will only have ip settings that are valid (but not necessarily correct).

##### OUTPUT
#  Writes the ip settings to the /etc/dhcpcd.conf file.
#

#  Reference: https://www.perlmonks.org/?node_id=11136353
#
#  Dazz
#  ver 1.3
#  8 Sept 2021

use strict; 
use warnings;
use Path::Tiny;
use Data::Dump;

###### Input file with ip settings
my $ip_filename = '/home/mimir/mb_ip.cfg';  # The ip info entered by the user into the GUI

###### Output dhcp configuration file
# my $dhcpcdfile = '/etc/dhcpcd.conf';
my $dhcpcdfile = 'd.conf';             # TEST

############################################################################################

use constant { 
  FALSE => 0;
  TRUE  => 1;
};

# Load the input parameters ip_params from the input file
my %ip_params;
%ip_params = ( %ip_params, # add new data to defaults, split with "="
  path($ip_filename)->slurp =~ /^(\w+)=(.*?)\s*$/gm );

# Print the contents of ip_params.                       #TEST
use Data::Dump 'dd'; dd 'ip_params', \%ip_params;        #TEST

# Convert 2 lines DNS to 1 line DNS.
$ip_params{domain_name_servers} = $ip_params{domain_name_server_1}." ".$ip_params{domain_name_server_2};
delete($ip_params{domain_name_server_1});
delete($ip_params{domain_name_server_2});

# Print to check the contents ip_params with combined DNS line.                       #TEST
use Data::Dump 'dd'; dd 'ip_params', \%ip_params;				      #TEST

{ # block scope for locals
local @ARGV = $dhcpcdfile;
local $^I = '.bak'; # make backup, do inplace edit
my $foundinterface = FALSE;
while( <> )
  {
  if( /^\s*profile\s+static_$ip_params{interface}\b.*\n/m ) # look for profile with matching interface name
    {                                                       # format matches 'static profile_eth0'
    $foundinterface = TRUE;
    warn "found section for $ip_params{interface} at line $.\n";
    }
  elsif( $foundinterface and /static/ )
    {
warn "ip param key : $ip_params{$0}\n"; #TEST 
warn "ip param val : $ip_params{$1}\n"; #TEST ***ERROR:  $1 not initiated. Lines 72 and 73***
    s/^\s*static\s+(\w+)=\K.*/$ip_params{$1}/m or warn "failed to change $1";  # match string before \K  Return string after \K
    # ?? What increments $ip_params through the hash ??
    # ?? What stops over-writing of other later sections ?? eg. wlan0
    warn "set $1 to $ip_params{$1}\n";
    }
  elsif( $foundinterface )
    {
    $foundinterface = FALSE;
    warn "ending changes at line $.\n";
    }
  # Output line to dhcpcdfile
  print;
  }
}

##</code><code>##

#IP Configuration
#Mon Sep 06 14:29:34 NZST 2021
routers=192.168.9.91
interface=eth0
domain_name_server_2=8.8.4.9
domain_name_server_1=8.8.8.9
ip_address=192.168.10.9/24

##</code><code>##

#static domain_name_servers=192.168.1.1

# fallback to static profile on eth0
#interface eth0
#fallback static_eth0
 
### Static LAN IP profile for Mimirbox
profile static_eth0
 static ip_address=1.1.1.1/24
 static routers=1.1.1.1
 static domain_name_servers=1.1.1.1 2.2.2.2

# Access Point Static interface mimirbox wlan0
  interface wlan0
  static ip_address=192.130.2.20/24