#!/usr/bin/perl

# stripgutenberg.pl < in.txt > out.txt
#
# designed for piping
# Written by Andrew Dunbar (hippietrail), released into the public domain, Dec 2010

use strict;

my $debug = 0;

my $state = 'beginning';
my $print = 0;
my $printed = 0;

while (1) {
	$_ = <>;

	last unless $_;

	# strip UTF-8 BOM
	if ($. == 1 && index($_, "\xef\xbb\xbf") == 0) {
		$_ = substr($_, 3);
	}

	if ($state eq 'beginning') {
		if (/^(The Project Gutenberg [Ee]Book( of|,)|Project Gutenberg's )/) {
			$state = 'normal pg header';
			$debug && print "state: beginning -> normal pg header\n";
			$print = 0;
		} elsif (/^$/) {
			$state = 'beginning blanks';
			$debug && print "state: beginning -> beginning blanks\n";
		} else {
			die "unrecognized beginning: $_";
		}
	} elsif ($state eq 'normal pg header') {
		if (/^\*\*\*\ ?START OF TH(IS|E) PROJECT GUTENBERG EBOOK,? /) {
			$state = 'end of normal header';
			$debug && print "state: normal pg header -> end of normal pg header\n";
		} else {
			# body of normal pg header
		}
	} elsif ($state eq 'end of normal header') {
		if (/^(Produced by|Transcribed from)/) {
			$state = 'post header';
			$debug && print "state: end of normal pg header -> post header\n";
		} elsif (/^$/) {
			# blank lines
		} else {
			$state = 'etext body';
			$debug && print "state: end of normal header -> etext body\n";
			$print = 1;
		}
	} elsif ($state eq 'post header') {
		if (/^$/) {
			$state = 'blanks after post header';
			$debug && print "state: post header -> blanks after post header\n";
		} else {
			# multiline Produced / Transcribed
		}
	} elsif ($state eq 'blanks after post header') {
		if (/^$/) {
			# more blank lines
		} else {
			$state = 'etext body';
			$debug && print "state: blanks after post header -> etext body\n";
			$print = 1;
		}
	} elsif ($state eq 'beginning blanks') {
		if (/<!-- #INCLUDE virtual=\"\/include\/ga-books-texth\.html\" -->/) {
			$state = 'header include';
			$debug && print "state: beginning blanks -> header include\n";
		} elsif (/^Title: /) {
			$state = 'aus header';
			$debug && print "state: beginning blanks -> aus header\n";
		} elsif (/^$/) {
			# more blanks
		} else {
			die "unexpected stuff after beginning blanks: $_";
		}
	} elsif ($state eq 'header include') {
		if (/^$/) {
			# blanks after header include
		} else {
			$state = 'aus header';
			$debug && print "state: header include -> aus header\n";
		}
	} elsif ($state eq 'aus header') {
		if (/^To contact Project Gutenberg of Australia go to http:\/\/gutenberg\.net\.au$/) {
			$state = 'end of aus header';
			$debug && print "state: aus header -> end of aus header\n";
		} elsif (/^A Project Gutenberg of Australia eBook$/) {
			$state = 'end of aus header';
			$debug && print "state: aus header -> end of aus header\n";
		}
	} elsif ($state eq 'end of aus header') {
		if (/^((Title|Author): .*)?$/) {
			# title, author, or blank line
		} else {
			$state = 'etext body';
			$debug && print "state: end of aus header -> etext body\n";
			$print = 1;
		}
	} elsif ($state eq 'etext body') {
		# here's the stuff
		if (/^<!-- #INCLUDE virtual="\/include\/ga-books-textf\.html" -->$/) {
			$state = 'footer';
			$debug && print "state: etext body -> footer\n";
			$print = 0;
		} elsif (/^(\*\*\* ?)?end of (the )?project/i) {
			$state = 'footer';
			$debug && print "state: etext body -> footer\n";
			$print = 0;
		}
	} elsif ($state eq 'footer') {
		# nothing more of interest
	} else {
		die "unknown state '$state'";
	}

	if ($print) {
		print;
		++$printed;
	} else {
		$debug && print "## $_";
	}
}