Re: pre-texted <STDIN>

[tybalt89]

Just as an excuse to play around with single line ANSI control sequences, I came up with this. It runs in an xterm on ArchLinux ( mostly because that's all I have to play with ).

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11115029
use warnings;

my $newline = promptandreviseline( "Previous Value : ", 'previous line
+' );

print "The New Line is: $newline\n";

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

use Term::ReadKey;
use Data::Dump qw( pp );

sub promptandreviseline
  {
  my ($prompt, $line) = @_;
  $line //= '';
  $line =~ tr/\t\n/ /;
  local $| = 1;
  my $startcolumn = 1 + length $prompt;
  print "\e[1G$prompt";
  my $cursor = length $line;
  my $pos = $startcolumn + $cursor;
  print "\e[${startcolumn}G\e[K$line\e[${pos}G";
  my $more = 1;
  ReadMode 'raw';
  while( $more )
    {
    sysread STDIN, my $input, 4096 or last;
    for my $key ( $input =~ /\e[^\e]+|./gs )
      {
      if( $key =~ /^[\cc\e]\z/ ) { $more = 0 } # ^c escape
      elsif( $key =~ /^[\n\r]\z/ )
        {
        print "\n";
        $line .= "\n";
        $more = 0
        }
      elsif( $key =~ /^[ -~]$/ ) { substr $line, $cursor++, 0, $key } 
+# char
      elsif( $key eq "\b" ) # backspace
        {
        $cursor > 0 and substr $line, --$cursor, 1, '';
        }
      elsif( $key eq "\e[3~" ) # Delete
        {
        $cursor < length($line) and substr $line, $cursor, 1, '';
        }
      elsif( $key eq "\e[D" ) { $cursor > 0 and $cursor-- } # left arr
+ow
      elsif( $key eq "\e[C" ) { $cursor < length($line) and ++$cursor 
+} # right
      elsif( $key eq "\e[F" ) { $cursor = length($line) } # End
      elsif( $key eq "\e[H" ) { $cursor = 0 } # Home
      else # invalid, show sequence
        {
        my $seq = pp $key;
        substr $line, $cursor, 0, $seq;
        $cursor += length $seq;
        }
      $pos = $startcolumn + $cursor;
      $more and print "\e[${startcolumn}G$line\e[K\e[${pos}G";
      }
    }
  ReadMode 'restore';
  return $line;
  }