#!/usr/bin/perl

use strict;
use warnings;

sub _search ($;$);						# pre-declare the _search() subroutine
sub _delete ($;$);						# pre-declare the _delete() subroutine

$|++;								# autoflush on

my $file = shift;						# get file from command line

unless ( $file and -f $file )					# check if we got a readable file
{
	print "Specify filename to load URLs from: ";		# ask the user for a filename to load the URLs from
	chomp( $file = <STDIN> );
	print "\n";
} # unless

open( my $in, '<', $file )					# try to open the specified filename
	or die "open R '$file' failed: $!";			# die on error
chomp( my @url_list = <$in> );					# get the URLs, one URL per line
close( $in );

my @new_urls = ();						# used to save unsaved URLs
my @del_urls = ();						# used to save deleted URLs
my @search   = ();						# used to save last search/get command return values
my $is_saved =  1;						# used to mark whether the URL list is saved or not
my $done     =  0;						# used to store if we are done

do {
	print "> ";						# ask the user for a command
	chomp( my $cmd = <STDIN> );
	$cmd  = lc $cmd;					# make the command lowercase
	$cmd =~ s/\s//;						# delete whitespace from the command

	do{$done=1;goto LOOP} if $cmd eq 'q' or $cmd eq 'quit' or $cmd eq 'exit' or $cmd eq 'bye';	# leave the loop if the user typed q or quit

	if ( $cmd eq 'a' or $cmd eq 'add' )			# add a new URL?
	{
		print "New URL: ";				# ask the user for a new URL to add
		chomp( my $new_url = <STDIN> );			# get the URL

		if ( grep { $_ eq $new_url } @url_list )	# check if we already have this URL in the list
		{
			print "\nURL already in list.\nYou may want to '> s[earch]' or '> see' the URL list.\n\n";
			goto LOOP;
		} # if

		push( @url_list, $new_url );			# add it to the URL list
		push( @new_urls, $new_url );			# add it to the 'unsaved' URL list
		$is_saved = 0;					# mark the list as unsaved

		print "\nURL added.\nYou may want to '> save' the URL list.\n\n";
	} # if
	elsif ( $cmd eq 'd' or $cmd eq 'del' or $cmd eq 'delete' )	# delete some URLs?
	{
		print "URL or # ";				# ask the user for a URL or a number
		chomp( my $del_url = <STDIN> );

		goto LOOP unless $del_url;

		my $url_pl = 0;					# used to store whether multiple URLs got deleted or not
		my $del    = 0;					# used to store if we deleted any URL

		if ( @search && $del_url =~ /^\d+/ )		# if a search list exists and the user specified a number
		{ $del = _delete( $search[ $del_url-1 ], 0 ) }	# delete the URL, do not ask the user before doing it
		else
		{
			_search( $del_url, sub{<STDIN>} );	# search the URL list

			if ( @search > 1 )			# we have multiple search items?
			{
				print "\nWhich URLs do you want to delete? (range) ";	# ask the user for the URLs to delete
				chomp( $del_url = <STDIN> );

				$del_url =~ s/\s//g;		# delete all spaces from the specified range

				for my $p ( split( ',', $del_url ) )	# iterate over each part of the range
				{
					my @p = split( '..', $p );	# try to split this part
					$p[1] = $p[0] if @p == 1;	# set p.1 so that we can build a range if we have just one value

					$del  = _delete( $search[ $_-1 ], 1 ) for $p[0] .. $p[1];	# delete the URLs, ask the user before doing it
				} # for

				$url_pl = 1;			# set the URL plural flag to 1
			} # if
			else
			{ $del = _delete( $search[0], 1 ) }	# delete the URL, ask the user before doing it
		} # else

		if ( $del )
		{ print "\nURL". ($url_pl ? 's' : '') ." deleted.\nYou may want to '> save' the URL list.\n\n" }
		else
		{ print "\nProblem while deleting ". ($url_pl ? 'one or more URLs' : 'the URL') .".\nYou may want to '> s(earch)' or '> see' the URL list to get more information.\nYou may also want to '> save' the URL list.\n\n" }
	} # elsif
	elsif ( $cmd eq 'c' or $cmd eq 'changes' )		# show changes?
	{
		if ( $is_saved )
		{
			print "There are no unsaved changes.\n\n";
			goto LOOP;
		} # if

		if ( @new_urls )
		{
			print "New URLs till last save:\n";
			for my $i ( 1 .. @new_urls )
			{
				<STDIN> if $i % 24 == 0;	# stop the output every 24 lines

				printf
					"%3s : %s\n",
					$i, $new_urls[$i-1];
			} # for

			print "\n";
		} # if
		if ( @del_urls )
		{
			print "Deleted URLs till last save:\n";
			for my $i ( 1 .. @del_urls )
			{
				<STDIN> if $i % 24 == 0;	# stop the output every 24 lines

				printf
					"%3s : %s\n",
					$i, $del_urls[$i-1];
			} # for

			print "\n";
		} # if
	} # elsif
	elsif ( $cmd eq 's' or $cmd eq 'search' )		# search the URL list?
	{
		print "Enter search string: ";			# ask the user for the search string
		chomp( my $search = <STDIN> );

		_search( $search, sub{<STDIN>} );		# search the URL list

		print "\nYou may want to '> d[elete]' or '> a[dd]' some URLs.\n\n";
	} # elsif
	elsif ( $cmd eq 'see' )					# show the full URL list?
	{
		_search( '' );					# search for nothing, so get all

		if ( $is_saved )
		{ print "\nThese were all URLs in the list.\n\n" }
		else
		{ print "\nThese were all URLs in the list.\nYou may want to '> save' the URL list, because it has got unsaved changes.\nTo see these changes, please use the '> c[hanges]' command.\n\n" }
	} # elsif
	elsif ( $cmd eq 'w' or $cmd eq 'write' or $cmd eq 'save' )	# save the URL list?
	{
		print "Type filename to save the list to [$file] ";	# ask the user for a filename to save the list to
		chomp( my $new_file = <STDIN> );

		($file = $new_file) if $new_file;

		open( my $out, '>', $file )			# try to open the specified filename
			or die "open W '$file' failed: $!";	# die on error
		print $out join( "\n", @url_list );		# write the url list to this file
		clsoe( $out );

		@new_urls = ();					# reset the 'unsaved' URL list
		@del_urls = ();					# reset the 'deleted' URL list
		$is_saved =  1;					# reset the is_saved flag

		print "\nURL list saved.\n\n";
	} # elsif
	else
	{
		print "Unknown command '$cmd'.\nPossible commands are: a[dd], c[hanges], d[el[ete]], s[earch], see, save/w[rite], q[uit]/exit/bye\n\n";
	} # else

	LOOP:
} until $done;

unless ( $is_saved )
{
	if ( @new_urls )
	{
		print "New URLs till last save:\n";
		for my $i ( 1 .. @new_urls )
		{
			<STDIN> if $i % 24 == 0;		# stop the output every 24 lines

			printf
				"%3s : %s\n",
				$i, $new_urls[$i-1];
		} # for

		print "\n";
	} # if
	if ( @del_urls )
	{
		print "Deleted URLs till last save:\n";
		for my $i ( 1 .. @del_urls )
		{
			<STDIN> if $i % 24 == 0;		# stop the output every 24 lines

			printf
				"%3s : %s\n",
				$i, $del_urls[$i-1];
		} # for
		print "\n";
	}

	print "Do you really want to lose these changes? (yes/no) [no] ";
	chomp( my $answer = <STDIN> );
	$answer  = lc $answer;					# make the answer lowercase
	$answer =~ s/\s//;					# delete whitespace from the answer

	exit 0 if $answer eq 'y' or $answer eq 'yes';		# exit the application, the user does not want to save the changes

	print "Type filename to save the list to [$file] ";	# ask the user for a filename to save the list to
	chomp( my $new_file = <STDIN> );

	($file = $new_file) if $new_file;

	open( my $out, '>', $file )				# try to open the specified filename
		or die "open W '$file' failed: $!";		# die on error
	print $out join( "\n", @url_list );			# write the url list to this file
	clsoe( $out );

	print "\nURL list saved.\n\n";
} # if

#
# _search( SEARCH [, WAIT_TIME] )
# This subroutine searches the @url_list array for SEARCH and saves the matches
# in @search.
# It will wait WAIT_TIME seconds after showing the number of results to the user.
# If WAIT_TIME is a code reference, it will run that code reference instead.
# The @search array will get printed to the screen with a <STDIN> stop every 24 lines.
#
sub _search ($;$)
{
	my( $search, $wait ) = @_;

	@search = grep { /\Q$search\E/ } @url_list;		# search the URL list

	print "\n@{[ 0+@search ]} entries matching '$search'.\n";

	if ( $wait && ref( $wait ) eq 'CODE' )
	{ $wait->() }						# run the wait code
	else
	{ select( undef, undef, undef, $wait || 0 ) }		# wait $wait or zero seconds

	for my $i ( 1 .. @search )
	{
		<STDIN> if $i % 24 == 0;			# stop the output every 24 lines

		printf
			"%3s : %s\n",
			$i, $search[$i-1];
	} # for
} # _search

#
# _delete( URL [, ASK_BEFORE] )
# This subroutine deletes one URL from the URL list.
# It will ask the user before deleting the item if ASK_BEFORE is set to true.
# This subroutine will also delete the URL from the 'unsaved' URL list and it will
# add all deleted URLs to the 'deleted' URL list and change the is saved flag
# respectively.
#
sub _delete ($;$)
{
	my( $url, $q ) = @_;

	if ( $q )						# shall we asked the user?
	{
		print "$url\nDo you really want to delete this URL? (yes/no) [yes] ";	# ask the user if he/she wants to delete the URL
		chomp( my $answer = <STDIN> );
		$answer  = lc $answer;				# make the answer lowercase
		$answer =~ s/\s//;				# delete whitespace from the answer

		return 0 if $answer eq 'n' or $answer eq 'no';	# return false if the answer was 'no'
	} # if

	my $idx;
	($idx) = grep { $url_list[$_] eq $url } 0.. $#url_list;	# try to find the URL in the URL list
	splice( @url_list, $idx, 1 ) if defined $idx;		# delete the URL from the URL list

	return 0 if ! defined $idx;				# return false if the URL could not be found

	push( @del_urls, $url );				# add the deleted URL to the 'deleted' URL list
	$is_saved = 0;						# reset the is_saved flag

	($idx) = grep { $new_urls[$_] eq $url } 0.. $#new_urls;	# try to find the URL in the 'unsaved' URL list
	splice( @new_urls, $idx, 1 ) if defined $idx;		# delete the URL from the 'unsaved' URL list

	return 1;
} # _delete