package App::DuckPAN::Restart;
our $AUTHORITY = 'cpan:DDG';
# ABSTRACT: Automatic restarting of application on file change
$App::DuckPAN::Restart::VERSION = '1018';
use File::Find::Rule;
use Filesys::Notify::Simple;

use App::DuckPAN::TemplateDefinitions;
use Try::Tiny;

use strict;

use Moo::Role;

requires '_run_app';

sub run_restarter {
	my ($self, $args) = @_;

	# exit immediately if not in an IA directory
	$self->app->get_ia_type;

	# will keep (re)starting the server until the app exits
	while(1){
	    defined(my $app = fork) or die 'Failed to fork application';
	    unless($app){ # app kid
	        $self->_run_app($args);
	        exit 0;
	    }

	    # Slightly different format here since we need to take care of
	    # the newly spawned app on failure.
	    my $fmon = fork;
	    unless($fmon){ # file monitor kid
	        unless(defined $fmon){
	            kill SIGTERM => $app;
	            die 'Failed to fork file monitor';
	        }
	        $self->_monitor_directories;
	        exit 0;
	    }

	    # wait for one them to exit. -1 waits for all children
	    my $pid = waitpid -1, 0;

	    # reload the application
	    if($pid == $fmon){
	        # if we can't kill the app, let's not start another
	        unless(kill SIGTERM => $app){
	            die "Failed to kill the application (pid: $app). Check manually";
	        }
	        # wait for it, otherwise the next whie loop will get it
	        waitpid($app, 0);
	    }
	    elsif($pid == $app){ # or exit
	        kill SIGTERM => $fmon;
	        exit;
	    }
	    else{ die "Unknown kid $pid reaped!\n"; } # shouldn't happen
	}
}

sub _get_directories_to_monitor {
	my $self = shift;
	my @output_dirs;

	try {
	    my $template_defs = App::DuckPAN::TemplateDefinitions->new;
	    my @templates = $template_defs->get_templates;

	    for my $template (@templates) {
	        push @output_dirs, $template->output_directory
	            unless $template->name =~ /test/;
	    }
	}
	catch {
	    if (/template definitions/i) {
	        # There was a problem loading the template definitions file. This
	        # can happen if the instant answer repository is of an older
	        # version and does not have the templates.yml file.
	        #
	        # In this case we use the older method of determining directories
	        # to monitor. This support can be removed sometime in the future.
	        # Note: Cheatsheet directories will not be monitored with this
	        # method.

	        $self->app->emit_debug("Instant Answers repository does not have a " .
	            "template definitions file. Some directories may not be monitored " .
	            "for changes.");

	        while(my ($type, $io) = each %{$self->app->get_ia_type()->{templates}}){
	            next if $type eq 'test'; # skip the test dir?
	            push @output_dirs, $io->{out};
	        }
	    }
	    else {
	        die $_;
	    }
	};

	my %distinct_dirs;

	# add all subdirectories
	for my $dir (@output_dirs) {
	    ++$distinct_dirs{$_} for File::Find::Rule->directory()->in($dir);
	}

	++$distinct_dirs{$self->app->get_ia_type()->{dir}};

	return [ keys %distinct_dirs ];
}

# Monitors development directories for file changes.  Tries to get the
# list of directories in a general way.  This subroutine
# blocks, so when it returns we know there's been a change
sub _monitor_directories {
	my $self = shift;

	# Find all of the directories that neeed to monitored
	# Note: Could potentially be functionality added to App::DuckPAN
	# which would return the directories involved in an IA
	# (see https://github.com/duckduckgo/p5-app-duckpan/issues/200)
	my $dirs = $self->_get_directories_to_monitor;

	FSMON: while(1){
	    # Find all subdirectories
	    # Create our watcher with each directory
	    my $watcher = Filesys::Notify::Simple->new($dirs);
	    # Wait for something to happen.  This blocks, which is why
	    # it's in a wheel.  On detection of update it will fall
	    # through; thus the while(1)
	    my $reload;
	    $watcher->wait(sub {
	        for my $event (@_) {
	            my $file = $event->{path};
	            # if it's a newly created directory, dot file, or pulled
	            # in dynamically there shouldn't be a need to reload.
	            # This will catch directories with files in them properly,
	            # as each file will be its own event
	            if( (-d $file) || ($file =~ m{^(?:.+/)?\.[^/]+$}o) || ($file =~ /\.(?:handlebars|css|js)$/oi) ){
	                next;
	            }
	            # All other changes trigger a reload
	            ++$reload;
	        }
	    });
	    # time to reload or keep waiting
	    last FSMON if $reload;
	}
}

1;

__END__

=pod

=head1 NAME

App::DuckPAN::Restart - Automatic restarting of application on file change

=head1 VERSION

version 1018

=head1 AUTHOR

DuckDuckGo <open@duckduckgo.com>, Zach Thompson <zach@duckduckgo.com>, Zaahir Moolla <moollaza@duckduckgo.com>, Torsten Raudssus <torsten@raudss.us> L<https://raudss.us/>

=head1 COPYRIGHT AND LICENSE

This software is Copyright (c) 2013 by DuckDuckGo, Inc. L<https://duckduckgo.com/>.

This is free software, licensed under:

  The Apache License, Version 2.0, January 2004

=cut