###########################################################################
#
# HTMLPlug.pm -- basic html plugin
#
# A component of the Greenstone digital library software
# from the New Zealand Digital Library Project at the 
# University of Waikato, New Zealand.
#
# Copyright (C) 1999 New Zealand Digital Library Project
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
###########################################################################

# 
# Note that this plugin handles frames only in a very simple way
# i.e. each frame is treated as a separate document. This means
# search results will contain links to individual frames rather
# than linking to the top level frameset.
# There may also be some problems caused by the _parent target
# (it's removed by this plugin)
# To use frames properly you'll need to use the WebPlug plugin.
#


package HTMLPlug;

use BasPlug;
use html;
use util;
use parsargv;

sub BEGIN {
    @ISA = ('BasPlug');
}

use strict;

sub print_usage {
    print STDERR "\nIncorrect options passed to HTMLPlug, check your collect.cfg configuration file\n";

    print STDERR "\n  usage: plugin HTMLPlug [options]\n\n";
    print STDERR "  options:\n";
    print STDERR "   -process_exp           A perl regular expression to match against filenames.\n";
    print STDERR "                          Matching filenames will be processed by this plugin.\n";
    print STDERR "                          Defaults to '(?i)\.html?\$' i.e. all documents ending in\n";
    print STDERR "                          .htm or .html (case-insensitive).\n";
    print STDERR "   -nolinks               Don't make any attempt to trap links (setting this flag may\n";
    print STDERR "                          improve speed of building/importing but any relative links within\n";
    print STDERR "                          documents will be broken).\n";
    print STDERR "   -block_exp             Files matching this regular expression will be blocked from\n";
    print STDERR "                          being passed to any further plugins in the list. By default\n";
    print STDERR "                          HTMLPlug blocks any files with .gif, .jpg, .jpeg, .png, .pdf,\n";
    print STDERR "                          .rtf or .css file extensions.\n";
    print STDERR "   -keep_head             Don't remove headers from html files.\n";
    print STDERR "   -no_metadata           Don't attempt to extract any metadata from files.\n";
    print STDERR "   -metadata_fields       Comma separated list of metadata fields to attempt to extract.\n";
    print STDERR "                          Defaults to 'Title'\n";
    print STDERR "   -w3mir                 Set if w3mir was used to generate input file structure.\n";
    print STDERR "                          w3mir \n";
    print STDERR "   -assoc_files           Perl regular expression of file extensions to associate with\n";
    print STDERR "                          html documents. Defaults to '(?i)\.(jpe?g|gif|png|css|pdf)$'\n";
    print STDERR "   -rename_assoc_files    Renames files associated with documents (e.g. images). Also\n";
    print STDERR "                          creates much shallower directory structure (useful when creating\n";
    print STDERR "                          collections to go on cd-rom).\n\n";
}

sub new {
    my $class = shift (@_);
    my $self = new BasPlug ();

    if (!parsargv::parse(\@_, 
			 q^process_exp/.*/(?i)\.html?$^, \$self->{'process_exp'},
			 q^nolinks^, \$self->{'nolinks'},
			 q^block_exp/.*/(?i)\.(gif|jpe?g|png|pdf|rtf|css)$^, \$self->{'block_exp'},
			 q^keep_head^, \$self->{'keep_head'},
			 q^no_metadata^, \$self->{'no_metadata'},
			 q^metadata_fields/.*/Title^, \$self->{'metadata_fields'},
			 q^w3mir^, \$self->{'w3mir'},
			 q^assoc_files/.*/(?i)\.(jpe?g|gif|png|css|pdf)$^, \$self->{'assoc_files'},
			 q^rename_assoc_files^, \$self->{'rename_assoc_files'})) {
	&print_usage();
	die "\n";
    }

    $self->{'aux_files'} = {};
    $self->{'dir_num'} = 0;
    $self->{'file_num'} = 0;

    return bless $self, $class;
}

sub is_recursive {
    my $self = shift (@_);

    return 0; # this is not a recursive plugin
}

# return number of files processed, undef if can't process
# Note that $base_dir might be "" and that $file might 
# include directories
sub read {
    my $self = shift (@_);
    my ($pluginfo, $base_dir, $file, $metadata, $processor) = @_;

    my $filename = &util::filename_cat($base_dir, $file);
    return 0 if $filename =~ /$self->{'block_exp'}/;
    if ($filename !~ /$self->{'process_exp'}/ || !-f $filename) {
	return undef;
    }
    $file =~ s/^[\/\\]+//;

    $self->{'verbosity'} = $processor->{'verbosity'};
    print STDERR "HTMLPlug: processing $file\n" 
	if $self->{'verbosity'} > 1;

    # create a new document
    my $doc_obj = new doc ($file, "indexed_doc");
    my $cursection = $doc_obj->get_top_section();
    
    # read in HTML file
    open (FILE, $filename) || die "HTMLPlug::read - can't open $filename\n";
    undef $/;
    my $text = <FILE>;
    $/ = "\n";
    close FILE;
    if (!defined $text || $text !~ /\w/) {
	print STDERR "HTMLPlug: ERROR: $file contains no text\n" if $self->{'verbosity'};
	return 0;
    }

    $self->extra_metadata ($doc_obj, $cursection, $metadata);
    $self->extract_metadata (\$text, $metadata, $doc_obj, $cursection) 
	unless $self->{'no_metadata'};

    # Store URL for page as metadata - this can be used for an
    # altavista style search interface. The URL won't be valid
    # unless the file structure contains the domain name (i.e.
    # like when w3mir is used to download a website).
    my $web_url = "http://$file";
    $web_url =~ s/\\/\//g; # for windows
    $doc_obj->add_metadata($cursection, "URL", $web_url);

    # remove header and footer
    if (!$self->{'keep_head'}) {
	$text =~ s/^.*?<body[^>]*>//is;
	$text =~ s/(<\/body[^>]*>|<\/html[^>]*>)//isg;
    }

    # trap links
    if (!$self->{'nolinks'}) {

	# usemap="./#index" not handled correctly => change to "#index"
	$text =~ s/(<img[^>]*?usemap\s*=\s*\"?)([^\">\s]+)(\"?[^>]*>)/
	    $self->replace_usemap_links($1, $2, $3)/isge;

	$text =~ s/(<(?:a|area|frame|link)\s+[^>]*?(?:href|src)\s*=\s*\"?)([^\">\s]+)(\"?[^>]*>)/
	    $self->replace_href_links ($1, $2, $3, $base_dir, $file, $doc_obj, $cursection)/isge;
    }

    # trap images
    $text =~ s/(<img[^>]*?src\s*=\s*\"?)([^\">\s]+)(\"?[^>]*>)/
	$self->replace_images ($1, $2, $3, $base_dir, $file, $doc_obj, $cursection)/isge;

    $doc_obj->add_text ($cursection, $text);

    # add an OID
    $doc_obj->set_OID();

    # process the document
    $processor->process($doc_obj);

    return 1; # processed the file
}

sub replace_images {
    my $self = shift (@_);
    my ($front, $link, $back, $base_dir, 
	$file, $doc_obj, $section) = @_;
    
    $link =~ s/\n/ /g;
    
    my ($href, $hash_part, $rl) = $self->format_link ($link, $base_dir, $file);
    return $front . $self->add_file ($href, $rl, $hash_part, $base_dir, $doc_obj, $section) . $back;
}

sub replace_href_links {
    my $self = shift (@_);
    my ($front, $link, $back, $base_dir, $file, $doc_obj, $section) = @_;

    # attempt to sort out targets - frames are not handled 
    # well in this plugin and some cases will screw things
    # up - e.g. the _parent target (so we'll just remove 
    # them all ;-)
    $front =~ s/(target=\"?)_top(\"?)/$1_gsdltop_$2/is;
    $back =~ s/(target=\"?)_top(\"?)/$1_gsdltop_$2/is;
    $front =~ s/target=\"?_parent\"?//is;
    $back =~ s/target=\"?_parent\"?//is;

    return $front . $link . $back if $link =~ /^\#/s;
    $link =~ s/\n/ /g;

    my ($href, $hash_part, $rl) = $self->format_link ($link, $base_dir, $file);

    my ($filename) = $href =~ /^(?:.*?):(?:\/\/)?(.*)/;

    ##### leave all these links alone (they won't be picked up by intermediate 
    ##### pages). I think that's safest when dealing with frames, targets etc.
    ##### (at least until I think of a better way to do it). Problems occur with
    ##### mailto links from within small frames, the intermediate page is displayed
    ##### within that frame and can't be seen. There is still potential for this to
    ##### happen even with html pages - the solution seems to be to somehow tell
    ##### the browser from the server side to display the page being sent (i.e. 
    ##### the intermediate page) in the top level window - I'm not sure if that's 
    ##### possible - the following line should probably be deleted if that can be done
    return $front . $link . $back if $href =~ /^(mailto|news|gopher|nntp|telnet|javascript):/is;


    if (($rl == 0) || ($filename =~ /$self->{'process_exp'}/) || 
	($href =~ /\/$/) || ($href =~ /^(mailto|news|gopher|nntp|telnet|javascript):/i)) {
	&html::urlsafe ($href);
	return $front . "_httpextlink_&rl=" . $rl . "&href=" . $href . $hash_part . $back;
	
    } else {
	# link is to some other type of file (image, pdf etc.) so we'll
	# need to associate that file
	return $front . $self->add_file ($href, $rl, $hash_part, $base_dir, $doc_obj, $section) . $back;
    }
}

sub add_file {
    my $self = shift (@_);
    my ($href, $rl, $hash_part, $base_dir, $doc_obj, $section) = @_;
    my ($newname);

    my $filename = $href;
    $filename =~ s/^[^:]*:\/\///;
    $filename = &util::filename_cat ($base_dir, $filename);
    my ($ext) = $filename =~ /(\.[^\.]*)$/;

    if ((!defined $ext) || ($ext !~ /$self->{'assoc_files'}/)) {
	return "_httpextlink_&rl=" . $rl . "&href=" . $href . $hash_part;
    }

    if ($self->{'rename_assoc_files'}) {
	if (defined $self->{'aux_files'}->{$href}) {
	    $newname = $self->{'aux_files'}->{$href}->{'dir_num'} . "/" .
		$self->{'aux_files'}->{$href}->{'file_num'} . $ext;
	} else {
	    $newname = $self->{'dir_num'} . "/" . $self->{'file_num'} . $ext;
	    $self->{'aux_files'}->{$href} = {'dir_num' => $self->{'dir_num'}, 'file_num' => $self->{'file_num'}};
	    $self->inc_filecount ();
	}
	$doc_obj->associate_file($filename, $newname, undef, $section);
	return "_httpcollimg_/$newname";

    } else {
	($newname) = $filename =~ /([^\/\\]*)$/;
	$doc_obj->associate_file($filename, $newname, undef, $section);
	return "_httpcollimg_/_thisOID_/$newname";
    }
}


sub format_link {
    my $self = shift (@_);
    my ($link, $base_dir, $file) = @_;

    my ($before_hash, $hash_part) = $link =~ /^([^\#]*)(\#?.*)$/;
    $hash_part = "" if !defined $hash_part;
    if (!defined $before_hash || $before_hash !~ /[\w\.\/]/) {
	print STDERR "HTMLPlug: ERROR - badly formatted tag ignored ($link)\n"
	    if $self->{'verbosity'};
	return ($link, "", 0);
    }
    
    if ($before_hash =~ s/^((?:http|ftp|file):\/\/)//i) {
	my $type = $1;
	       
	if ($link =~ /^(http|ftp):/i) {
	    # Turn url (using /) into file name (possibly using \ on windows)
	    my @http_dir_split = split('/', $before_hash);
	    $before_hash = &util::filename_cat(@http_dir_split);
	}

	$before_hash = $self->eval_dir_dots($before_hash);
					 
	my $linkfilename = &util::filename_cat ($base_dir, $before_hash);

	my $rl = 0;
	$rl = 1 if (-e $linkfilename);

	# make sure there's a slash on the end if it's a directory
	if ($before_hash !~ /\/$/) {
	    $before_hash .= "/" if (-d $linkfilename);
	}

	return ($type . $before_hash, $hash_part, $rl);
    
    } elsif ($link !~ /^(mailto|news|gopher|nntp|telnet|javascript):/i) {

	if ($before_hash =~ s/^\///) {
	    # the first directory will be the domain name if w3mir was used
	    # to generate archives, otherwise we'll assume all files are
	    # from the same site and base_dir is the root
	    if ($self->{'w3mir'}) {
		my @dirs = split /[\/\\]/, $file;
		my $domname = shift (@dirs);
		$before_hash = &util::filename_cat($domname, $before_hash);
		$before_hash =~ s/\\/\//g; # for windows
	    }

	} else {
	    # Turn relative file path into full path
	    my $dirname = &File::Basename::dirname($file);
	    $before_hash = &util::filename_cat($dirname, $before_hash);
	    $before_hash = $self->eval_dir_dots($before_hash);
	}

	# make sure there's a slash on the end if it's a directory
	my $linkfilename = &util::filename_cat ($base_dir, $before_hash);
	if ($before_hash !~ /\/$/) {
	    $before_hash .= "/" if (-d $linkfilename);
	}

	return ("http://" . $before_hash, $hash_part, 1);

    } else {
	# mailto, news, nntp, telnet, javascript or gopher link
	return ($before_hash, "", 0);
    }
}

sub extract_metadata {
    my $self = shift (@_);
    my ($textref, $metadata, $doc_obj, $section) = @_;

    foreach my $field (split /,/, $self->{'metadata_fields'}) {
	
	# don't need to extract field if it was passed in from a previous 
	# (recursive) plugin
	next if defined $metadata->{$field};

	# see if there's a <meta> tag for this field
	if ($$textref =~ /<meta(.*?)(?:name|http-equiv)\s*=\s*\"?$field\"?([^>]*)/is) {
	    my $content = $1 . $2;
	    if ($content =~ /content\s*=\s*\"?(.*?)\"?/is) {
		if (defined $1) {
		    my $value = $1;
		    $value =~ s/\s+/ /gs;
		    $doc_obj->add_metadata($section, $field, $value);
		    next;
		}
	    }
	}
	
	# special case for Title metadata - try <title> tags
	# then first 100 characters of text
	
	if ($field =~ /^title$/i) {

	    # see if there's a <title> tag
	    if ($$textref =~ /<title[^>]*>([^<]*)<\/title[^>]*>/is) {
		if (defined $1) {
		    my $title = $1;
		    if ($title =~ /\w/) {
			$title =~ s/\s+/ /gs;
			$doc_obj->add_metadata ($section, $field, $title);
			next;
		    }
		}
	    }
	    
	    # if no title use first 100 characters
	    my $tmptext = $$textref;
	    $tmptext =~ s/<[^>]*>//g;
	    my $title = substr ($tmptext, 0, 100);
	    $title =~ s/\s+/ /gs;
	    $doc_obj->add_metadata ($section, $field, $title);
	}
    }
}

# evaluate any "../" to next directory up
# evaluate any "./" as here
sub eval_dir_dots {
    my $self = shift (@_);
    my ($filename) = @_;

    my $dirsep_os = &util::get_os_dirsep();
    my @dirsep = split(/$dirsep_os/,$filename);

    my @eval_dirs = ();
    foreach my $d (@dirsep) {
	if ($d eq "..") {
	    pop(@eval_dirs);

	} elsif ($d eq ".") {
	    # do nothing!

	} else {
	    push(@eval_dirs,$d);
	}
    }

    return &util::filename_cat(@eval_dirs);
}

sub replace_usemap_links {
    my $self = shift (@_);
    my ($front, $link, $back) = @_;

    $link =~ s/^\.\///;
    return $front . $link . $back;
}

sub inc_filecount {
    my $self = shift (@_);

    if ($self->{'file_num'} == 1000) {
	$self->{'dir_num'} ++;
	$self->{'file_num'} = 0;
    } else {
	$self->{'file_num'} ++;
    }
}

1;