#!/usr/bin/env perl

use strict;
use warnings;

my %msg = ();
my @start = ();
my %reorder = (help=>-1);

READ: while(<>) {
  if(m/^# HELP HEADER START/) {
    while(<>) {
      next READ if m/^# HELP HEADER END/;
      if(m/# (.*)/) {
        push @start, $1
      } else {
        die "$0: Invalid HELP HEADER section in Makefile!\n";
      }
    }
    next READ
  }
  if(m/# HELP((?:\([^\(\)]+\))?):\s*(.*)/) {
    my ($target, $message) = ($1, $2);
    if($target=~m/\((.*)\)/) {
      $target = $1;
    } else {
      my $line = <>;
      die "$0: Unexpected end of file, target expected!\n" if not defined $line;
      $line=~m/^([^:]+):/ or die "$0: HELP marker expects target but no target found!\n";
      $target = $1
    }
    $msg{$target} .= $message
  }
}

print "$_\n" for @start;
print "\n" if @start;
for my $tar(sort {($reorder{$a}||0) <=> ($reorder{$b}||0) || $a cmp $b } keys %msg) {
  print "$tar\n  $msg{$tar}\n\n"
}