#!/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