use warnings; use 5.012; use strict;
use IO::Handle;
use Getopt::Long;
use URI;
use File::Spec::Functions "catfile";
use XML::Twig;

our $VERSION = 0.001;

our $gbase = undef;
our $listfname = undef;
our $dirprefix = ".";
our $verbose;
our($versionopt, $helpopt);

Getopt::Long::Configure qw"bundling gnu_compat prefix_pattern=(--|-)";
GetOptions(
	"b|base=s" => \$gbase,
	"i|listfile=s" => \$listfname,
	"P|directory-prefix|prefix=s" => \$dirprefix,
	"v|verbose" => \$verbose,
	"V|version" => \$versionopt,
	"h|help" => \$helpopt,
);

if ($versionopt) {
	die "reshtml $VERSION\n";
} elsif ($helpopt) {
	my $helpstr = q(Usage: reshtml [-b BASEURL] [FILENAME...]
	Parses a HTML document, extract the list of images and other resources
	necessary to render it, qualifies URLs to absolute URL using BASEURL as the
	base, prints URLs one per line.  
	);
	$helpstr =~ s/\n\s*/\n/g;
	die $helpstr;
}

my $base;
my $relwarn;
my $ifname;
my %foundurl;
my $foundurl = sub {
	my($u) = @_;
	$u = URI->new($u);
	if (length($base)) {
		$u = $u->abs($base);
	} elsif (!$u->scheme) { # relative URL
		$relwarn++ or warn "warning: relative URL found and base address unknown, in file $ifname";
	}
	# we could canonicalize the URL for hashing purposes, but let's ignore that
	if (!$foundurl{$u}++) {
		print $u, "\n";
	}
};
my %twhnd;
$twhnd{"base"} = sub {
	my($tw, $e) = @_;
	$base = $e->att("href");
	1;
};
$twhnd{"link"} = $twhnd{"a"} = $twhnd{"area"} = sub {
	my($tw, $e) = @_;
	my $rs = $e->att("rel") // "";
	my %rw;
	for my $rw (split /[ \t\n\f\r]+/, $rs) { # seriously, HTML5 defines everything precisely
		$rw =~ y/A-Z/a-z/;
		$rw{$rw}++;	
	}
	if (length(my $u  = $e->att("href")) && (
		$rw{"icon"} || $rw{"stylesheet"} && !$rw{"alternate"}
	)) {
		&$foundurl($u);
	}
	1;
};
$twhnd{"img"} = $twhnd{"object"} = sub {
	my($tw, $e) = @_;
	for my $an ("src", "data") {
		if (length(my $u = $e->att($an))) {
			&$foundurl($u);
		}
	}
	1;
};

my $do_file = sub {
	my($fname, $stdin, $lbase) = @_;
	$ifname = $fname;
	$verbose and print STDERR "#$fname\n";
	$fname = catfile($dirprefix, $fname);
	$relwarn = 0;
	$base = $lbase // $gbase;
	my $twig = XML::Twig->new(twig_handlers => \%twhnd);
	if (!$stdin) {
		$twig->parsefile_html($fname);
	} else {
		$twig->parse_html(\*STDIN);
	}
	STDOUT->flush;
};

if (defined($listfname)) {
	@ARGV and die "error: both -i option and input filenames are given";
	open my $LIST, "<", $listfname or 
		die "error opening list file: ($listfname) $!";
	my $_;
	while (<$LIST>) {
		/\S/ or next;
		my($lbase, $fname, $rest) = split " ";
		length($rest) and die "error: invalid spec in listfile (too many words): $_ -";
		if (!defined($fname)) {
			$lbase =~ m"/([^/]+)/*$" or 
				die "error: cannot find suffix or base uri: $lbase";
			$fname = $1;
		}
		&$do_file($fname, 0, $lbase);
	}
} elsif (@ARGV) {
	for my $fname (@ARGV) {
		&$do_file($fname);
	}
} else {
	&$do_file("-", 1);
}

__END__