#!/usr/bin/env perl
#
use strict;
use warnings;

use CSS::Minifier::XS 0.07;
use File::Basename;
use File::Copy;
use File::Find;
use File::Path qw(make_path);
use File::Slurp;
use File::Spec;
use Getopt::Long;
use JavaScript::Minifier::XS;
use Pod::Usage;
use XML::LibXML;
use XML::LibXSLT;

my $canonical_url = 'https://www.exim.org/';

## Parse arguments
my %opt = parse_arguments();

## setup static root location
## TODO: for doc generation only this should be within the docs dir
$opt{staticroot} = File::Spec->catdir( $opt{docroot}, 'static' );

## Generate the pages
my %cache;    # General cache object
do_doc( 'spec',   $_ ) foreach @{ $opt{spec}   || [] };
do_doc( 'filter', $_ ) foreach @{ $opt{filter} || [] };
do_web() if ( $opt{web} );
do_static() if ( $opt{web} or !$opt{localstatic} );    # need this for all other pages generated

## Add the exim-html-current symlink
foreach my $type (qw(html pdf)) {
    print "Symlinking exim-$type-current to exim-$type-$opt{latest}\n" if ( $opt{verbose} );
    unlink("$opt{docroot}/exim-$type-current");
    symlink( "exim-$type-$opt{latest}", "$opt{docroot}/exim-$type-current" )
        || warn "symlink to $opt{docroot}/exim-$type-current failed";
}

# ------------------------------------------------------------------
## Generate the website files
sub do_web {

    ## copy these templates to docroot...
    copy_transform_files( "$opt{tmpl}/web", $opt{docroot}, 0 );
}

# ------------------------------------------------------------------
## Generate the static file set
sub do_static {
    my $staticroot = shift || $opt{staticroot};

    ## make sure I have a directory
    mkdir($staticroot) or die "Unable to make staticroot: $!\n" unless ( -d $staticroot );

    ## copy these templates to docroot...
    copy_transform_files( "$opt{tmpl}/static", $staticroot, 1 );
}

# ------------------------------------------------------------------
## Generate the website files
sub copy_transform_files {
    my $source = shift;
    my $target = shift;
    my $static = shift;

    ## Make sure the template web directory exists
    die "No such directory: $source\n" unless ( -d $source );

    ## Scan the web templates
    find(
        sub {
            my ($path) = substr( $File::Find::name, length("$source"), length($File::Find::name) ) =~ m#^/*(.*)$#;

            if ( -d "$source/$path" ) {

                ## Create the directory in the target if it doesn't exist
                if ( !-d "$target/$path" ) {
                    mkdir("$target/$path") or die "Unable to make $target/$path: $!\n";
                }

            }
            else {

                ## Build HTML from XSL files and simply copy static files which have changed
                if ( ( !$static ) and ( $path =~ /(.+)\.xsl$/ ) ) {
                    print "Generating  : /$1.html\n" if ( $opt{verbose} );
                    transform( undef, "$source/$path", "$target/$1.html" );
                }
                elsif ( -f "$source/$path" ) {

                    ## Skip if the file hasn't changed (mtime/size based)
                    return
                        if (( -f "$target/$path" )
                        and ( ( stat("$source/$path") )[9] == ( stat("$target/$path") )[9] )
                        and ( ( stat("$source/$path") )[7] == ( stat("$target/$path") )[7] ) );

                    if ( $path =~ /(.+)\.css$/ ) {
                        print "CSS to  : /$path\n" if ( $opt{verbose} );
                        my $content = read_file("$source/$path");
                        write_file( "$target/$path", $opt{minify} ? CSS::Minifier::XS::minify($content) : $content );
                    }
                    elsif ( $path =~ /(.+)\.js$/ ) {
                        print "JS to  : /$path\n" if ( $opt{verbose} );
                        my $content = read_file("$source/$path");
                        write_file( "$target/$path",
                            $opt{minify} ? JavaScript::Minifier::XS::minify($content) : $content );
                    }
                    else {
                        ## Copy
                        print "Copying to  : /$path\n" if ( $opt{verbose} );
                        copy( "$source/$path", "$target/$path" ) or die "$path: $!";
                    }
                    ## Set mtime
                    utime( time, ( stat("$source/$path") )[9], "$target/$path" );
                }
            }

        },
        "$source"
    );
}

# ------------------------------------------------------------------
## Generate index/chapter files for a doc
sub do_doc {
    my ( $type, $xml_path ) = @_;

    ## Read and validate the XML file
    my $xml = XML::LibXML->new()->parse_file($xml_path) or die $!;

    ## Get the version number
    my $version = $xml->findvalue('/book/bookinfo/revhistory/revision/revnumber');
    die "Unable to get version number\n" unless defined $version && $version =~ /^\d+(\.\d+)*$/;

    ## Prepend chapter filenames?
    my $prepend_chapter = $type eq 'filter' ? 'filter_' : '';

    ## Add the canonical url for this document
    $xml->documentElement()
        ->appendTextChild( 'canonical_url',
        "${canonical_url}exim-html-current/doc/html/spec_html/" . ( $type eq 'spec' ? 'index' : 'filter' ) . ".html" );

    ## Add a url for the latest version of this document
    if ( $version ne $opt{latest} ) {
        $xml->documentElement()
            ->appendTextChild( 'current_url',
            "../../../../exim-html-current/doc/html/spec_html/" . ( $type eq 'spec' ? 'index' : 'filter' ) . ".html" );
    }

    ## Fixup the XML
    xref_fixup( $xml, $prepend_chapter );

    ## set the staticroot
    my $staticroot =
        $opt{localstatic}
        ? File::Spec->catdir( $opt{docroot}, "exim-html-$version", 'doc', 'html', 'static' )
        : $opt{staticroot};
    unless ( -d $staticroot ) {
        make_path( $staticroot, { verbose => $opt{verbose} } );
        do_static($staticroot);
    }

    ## Generate the front page
    {
        my $path = "exim-html-$version/doc/html/spec_html/" . ( $type eq 'filter' ? $type : 'index' ) . ".html";
        print "Generating  : docroot:/$path\n" if ( $opt{verbose} );
        transform( $xml, "$opt{tmpl}/doc/index.xsl", "$opt{docroot}/$path", $staticroot );
    }

    ## Generate a Table of Contents XML file
    {
        my $path =
            "exim-html-$version/doc/html/spec_html/" . ( $type eq 'filter' ? 'filter_toc' : 'index_toc' ) . ".xml";
        print "Generating  : docroot:/$path\n" if ( $opt{verbose} );
        transform( $xml, "$opt{tmpl}/doc/toc.xsl", "$opt{docroot}/$path", $staticroot );
    }

    ## Generate the chapters
    my $counter = 0;
    my @chapters = map { $_->cloneNode(1) } $xml->findnodes('/book/chapter');
    my( $chapter_title, $chapter_title_prev, $chapter_title_next );
    foreach my $chapter (@chapters) {

        ## Add a <chapter_id>N</chapter_id> node for the stylesheet to use
        $chapter->appendTextChild( 'chapter_id', ++$counter );

        ## Get the current and surrounding chapter titles
        $chapter_title_prev = $chapter_title;
        $chapter_title      = $chapter_title_next || $chapter->findvalue('title_uri');
        $chapter_title_next = $chapters[$counter]->findvalue('title_uri') if $counter < int(@chapters);

        ## Add previous/next/canonical urls for nav
        {
            $chapter->appendTextChild( 'prev_url',
                  $counter == 1
                ? $type eq 'filter'
                        ? 'filter.html'
                        : 'index.html'
                : sprintf( '%sch-%s.html', $prepend_chapter, $chapter_title_prev ) );
            $chapter->appendTextChild( 'this_url', sprintf( '%sch-%s.html', $prepend_chapter, $chapter_title ) );
            $chapter->appendTextChild( 'next_url', sprintf( '%sch-%s.html', $prepend_chapter, $chapter_title_next ) )
                unless int(@chapters) == $counter;
            $chapter->appendTextChild( 'toc_url', ( $type eq 'filter' ? 'filter' : 'index' ) . '.html' );
            $chapter->appendTextChild(
                'canonical_url',
                sprintf(
                    'https://www.exim.org/exim-html-current/doc/html/spec_html/%sch-%s.html',
                    $prepend_chapter, $chapter_title
                )
            );
            if ( $version ne $opt{latest} ) {
                $chapter->appendTextChild(
                    'current_url',
                    sprintf(
                        '../../../../exim-html-current/doc/html/spec_html/%sch-%s.html',
                        $prepend_chapter, $chapter_title
                    )
                );
            }
        }

        ## Create an XML document from the chapter
        my $doc = XML::LibXML::Document->createDocument( '1.0', 'UTF-8' );
        $doc->setDocumentElement($chapter);

        ## Transform the chapter into html
        {
            my $real_path = sprintf( 'exim-html-%s/doc/html/spec_html/%sch-%s.html', $version, $prepend_chapter, $chapter_title );
            my $link_path = sprintf( 'exim-html-%s/doc/html/spec_html/%sch%02d.html',  $version, $prepend_chapter, $counter );
            print "Generating  : docroot:/$real_path\n" if ( $opt{verbose} );
            transform( $doc, "$opt{tmpl}/doc/chapter.xsl", "$opt{docroot}/$real_path", $staticroot );
            # Making a relative symlink to a file in the same directory.
            # Extract just the filename portion of $real_path.
            my $real_file = basename($real_path);
            print "Symlinking  : docroot:/$link_path to $real_file\n" if ( $opt{verbose} );
            if ( -f "$opt{docroot}/$link_path" ) {
               unlink("$opt{docroot}/$link_path") or die "failed removing $opt{docroot}/$link_path: $!";
            }
            symlink( "$real_file", "$opt{docroot}/$link_path" ) || die "symlink to $opt{docroot}/$link_path failed: $!";
        }
    }
}

# ------------------------------------------------------------------
## Fixup xref tags
sub xref_fixup {
    my ( $xml, $prepend_chapter ) = @_;

    my %index = ();

    ## Add the "prepend_chapter" info
    ( $xml->findnodes('/book') )[0]->appendTextChild( 'prepend_chapter', $prepend_chapter );

    ## Iterate over each chapter
    my $chapter_counter = 0;
    foreach my $chapter ( $xml->findnodes('/book/chapter') ) {
        ++$chapter_counter;

        my $chapter_id = $chapter->getAttribute('id');
        unless ($chapter_id) {    # synthesise missing id
            $chapter_id = sprintf( 'chapter_noid_%04d', $chapter_counter );
            $chapter->setAttribute( 'id', $chapter_id );
        }
        my $chapter_title = $chapter->findvalue('title');

        ## Set title_uri so we can use eg ch-introduction.html instead of ch01.html
        $chapter->appendTextChild( 'title_uri', title_to_uri($chapter_title) );

        $index{$chapter_id} = { chapter_id => $chapter_counter, chapter_title => $chapter_title };

        ## Iterate over each section
        my $section_counter = 0;
        foreach my $section ( $chapter->findnodes('section') ) {
            ++$section_counter;

            my $section_id = $section->getAttribute('id');
            unless ($section_id) {    # synthesise missing id
                $section_id = sprintf( 'section_noid_%04d_%04d', $chapter_counter, $section_counter );
                $section->setAttribute( 'id', $section_id );
            }
            my $section_title = $section->findvalue('title');

            $index{$section_id} = {
                chapter_id    => $chapter_counter,
                chapter_title => $chapter_title,
                section_id    => $section_counter,
                section_title => $section_title
            };
        }
    }
    ## Build indexes as new chapters
    build_indexes( $xml, $prepend_chapter, \%index );

    ## Replace all of the xrefs in the XML
    foreach my $xref ( $xml->findnodes('//xref') ) {
        my $linkend = $xref->getAttribute('linkend');
        if ( exists $index{$linkend} ) {
            $xref->setAttribute( 'chapter_id',    $index{$linkend}{'chapter_id'} );
            $xref->setAttribute( 'chapter_title', $index{$linkend}{'chapter_title'} );
            $xref->setAttribute( 'section_id', $index{$linkend}{'section_id'} ) if ( $index{$linkend}{'section_id'} );
            $xref->setAttribute( 'section_title', $index{$linkend}{'section_title'} )
                if ( $index{$linkend}{'section_title'} );
            $xref->setAttribute( 'url',
                sprintf( '%sch-%s.html', $prepend_chapter, title_to_uri($index{$linkend}{'chapter_title'}) )
                    . ( $index{$linkend}{'section_id'} ? '#' . $linkend : '' ) );
        }
    }
}

# ------------------------------------------------------------------
## Build indexes
sub build_indexes {
    my ( $xml, $prepend_chapter, $xref ) = @_;

    my $index_hash = {};
    my $current_id;
    foreach my $node ( $xml->findnodes('//section | //chapter | //indexterm') ) {
        if ( $node->nodeName eq 'indexterm' ) {
            my $role      = $node->getAttribute('role') || 'concept';
            my $primary   = $node->findvalue('child::primary');
            my $first     = ( $primary =~ /^[A-Za-z]/ ) ? uc( substr( $primary, 0, 1 ) ) : '';  # first letter or marker
            my $secondary = $node->findvalue('child::secondary') || '';
            next unless ( $primary || $secondary );    # skip blank entries for now...
            $index_hash->{$role}{$first}{$primary}{$secondary} ||= [];
            push @{ $index_hash->{$role}{$first}{$primary}{$secondary} }, $current_id;
        }
        else {
            $current_id = $node->getAttribute('id');
        }
    }

    # now we build a set of new chapters with the index data in
    my $book = ( $xml->findnodes('/book') )[0];
    foreach my $role ( sort { $a cmp $b } keys %{$index_hash} ) {
        my $chapter = XML::LibXML::Element->new('chapter');
        $book->appendChild($chapter);
        $chapter->setAttribute( 'id', join( '_', 'index', $role ) );
        $chapter->setAttribute( 'class', 'index' );
        $chapter->appendTextChild( 'title', ( ucfirst($role) . ' Index' ) );
        $chapter->appendTextChild( 'title_uri', title_to_uri(ucfirst($role) . ' Index') );

        foreach my $first ( sort { $a cmp $b } keys %{ $index_hash->{$role} } ) {
            my $section = XML::LibXML::Element->new('section');
            my $list    = XML::LibXML::Element->new('variablelist');
            $chapter->appendChild($section);
            $section->setAttribute( 'id', join( '_', 'index', $role, $first ) );
            $section->setAttribute( 'class', 'index' );
            $section->appendTextChild( 'title', $first ? $first : 'Symbols' );
            $section->appendChild($list);
            foreach my $primary ( sort { $a cmp $b } keys %{ $index_hash->{$role}{$first} } ) {
                my $entry = XML::LibXML::Element->new('varlistentry');
                my $item  = XML::LibXML::Element->new('listitem');
                $list->appendChild($entry)->appendTextChild( 'term', $primary );
                $entry->appendChild($item);
                my $slist;
                foreach my $secondary ( sort { $a cmp $b } keys %{ $index_hash->{$role}{$first}{$primary} } ) {
                    my $para = XML::LibXML::Element->new('para');
                    if ( $secondary eq '' ) {
                        $item->appendChild($para);    # skip having extra layer of heirarchy
                    }
                    else {
                        unless ($slist) {
                            $slist = XML::LibXML::Element->new('variablelist');
                            $item->appendChild($slist);
                        }
                        my $sentry = XML::LibXML::Element->new('varlistentry');
                        my $sitem  = XML::LibXML::Element->new('listitem');
                        $slist->appendChild($sentry)->appendTextChild( 'term', $secondary );
                        $sentry->appendChild($sitem)->appendChild($para);
                    }
                    my $count = 0;
                    foreach my $ref ( @{ $index_hash->{$role}{$first}{$primary}{$secondary} } ) {
                        $para->appendText(', ')
                            if ( $count++ );
                        my $xrefel = XML::LibXML::Element->new('xref');
                        $xrefel->setAttribute( linkend => $ref );
                        $xrefel->setAttribute( longref => 1 );
                        $para->appendChild($xrefel);
                    }
                }
            }
        }
    }
}

# ------------------------------------------------------------------
## Handle the transformation
sub transform {
    my ( $xml, $xsl_path, $out_path, $staticroot_abs ) = @_;

    ## make sure $staticroot is set
    $staticroot_abs ||= $opt{staticroot};

    ## Build an empty XML structure if an undefined $xml was passed
    unless ( defined $xml ) {
        $xml = XML::LibXML::Document->createDocument( '1.0', 'UTF-8' );
        $xml->setDocumentElement( $xml->createElement('content') );
    }

    ## Add the current version of Exim to the XML
    $xml->documentElement()->appendTextChild( 'current_version', $opt{latest} );

    ## Add the old versions of Exim to the XML
    $xml->documentElement()->appendTextChild( 'old_versions', $_ ) foreach old_docs_versions();

    ## Parse the ".xsl" file as XML
    my $xsl = XML::LibXML->new()->parse_file($xsl_path) or die $!;

    ## Generate a stylesheet from the ".xsl" XML.
    my $stylesheet = XML::LibXSLT->new()->parse_stylesheet($xsl);

    ## work out the static root relative to the target
    my $target_dir = ( File::Spec->splitpath($out_path) )[1];
    my $staticroot = File::Spec->abs2rel( $staticroot_abs, $target_dir );

    ## Generate a doc from the XML transformed with the XSL
    my $doc = $stylesheet->transform( $xml, staticroot => sprintf( "'%s'", $staticroot ) );

    ## Make the containing directory if it doesn't exist
    make_path( ( $out_path =~ /^(.+)\/.+$/ )[0], { verbose => $opt{verbose} } );

    ## Write out the document
    open my $out, '>', $out_path or die "Unable to write $out_path - $!";
    print $out $stylesheet->output_as_bytes($doc);
    close $out;
}

# ------------------------------------------------------------------
## Takes a chapter title and fixes it up so it is suitable for use in a URI
sub title_to_uri {
    my $title = lc(shift);
    $title =~ s/[^a-z0-9\s]+//gi; # Only allow spaces, numbers and letters
    $title =~ s/\s+/_/g;          # Replace spaces with underscores so URLs are easier to copy about
    return $title;
}

# ------------------------------------------------------------------
## Look in the docroot for old versions of the documentation
sub old_docs_versions {
    if ( !exists $cache{old_docs_versions} ) {
        my @versions;
        foreach ( glob("$opt{docroot}/exim-html-*") ) {
            push @versions, $1 if /-(\d+(?:\.\d+)?)$/ && $1 lt $opt{latest} && -d $_;
        }
        $cache{old_docs_versions} = [ reverse sort { $a cmp $b } @versions ];
    }
    return @{ $cache{old_docs_versions} };
}

# ------------------------------------------------------------------
## error_help
sub error_help {
    my $msg = shift;

    warn $msg;
    pod2usage( -exitval => 1, -verbose => 0 );
}

# ------------------------------------------------------------------
## Parse arguments
sub parse_arguments {

    my %opt = ( spec => [], filter => [], help => 0, man => 0, web => 0, minify => 1, verbose => 0, localstatic => 0 );
    GetOptions(
        \%opt,      'help|h!', 'man!',      'web!',    'spec=s{1,}', 'filter=s{1,}',
        'latest=s', 'tmpl=s',  'docroot=s', 'minify!', 'verbose!',   'localstatic!'
    ) || pod2usage( -exitval => 1, -verbose => 0 );

    ## --help
    pod2usage(0) if ( $opt{help} );
    pod2usage( -verbose => 2 ) if ( $opt{man} );

    ## --spec and --filter lists
    foreach my $set (qw[spec filter]) {
        $opt{$set} =
            [ map { my $f = File::Spec->rel2abs($_); error_help( 'No such file: ' . $_ ) unless -f $f; $f }
                @{ $opt{$set} } ];
    }
    ## --latest
    error_help('Missing value for latest') unless ( exists( $opt{latest} ) && defined( $opt{latest} ) );
    error_help('Invalid value for latest') unless $opt{latest} =~ /^\d+(?:\.\d+)*$/;

    ## --tmpl and --docroot
    foreach my $set (qw[tmpl docroot]) {
        error_help( 'Missing value for ' . $set ) unless ( exists( $opt{$set} ) && defined( $opt{$set} ) );
        my $f = File::Spec->rel2abs( $opt{$set} );
        error_help( 'No such directory: ' . $opt{$set} ) unless -d $f;
        $opt{$set} = $f;
    }
    error_help('Excess arguments') if ( scalar(@ARGV) );

    error_help('Must include at least one of --web, --spec or --filter')
        unless ( $opt{web} || scalar( @{ $opt{spec} || [] } ) || scalar( @{ $opt{filter} || [] } ) );

    return %opt;
}

# ------------------------------------------------------------------
1;

__END__

=head1 NAME

gen.pl - Generate exim html documentation and website

=head1 SYNOPSIS

gen.pl [options]

 Options:
   --help              display this help and exits
   --man               displays man page
   --spec file...      spec docbook/XML source files
   --filter file...    filter docbook/XML source files
   --web               Generate the general website pages
   --latest VERSION    Required. Specify the latest stable version of Exim.
   --tmpl PATH         Required. Path to the templates directory
   --docroot PATH      Required. Path to the website document root
   --[no-]minify       [Don't] minify CSS and Javascript
   --localstatic       Makes the static files local to each doc ver

=head1 OPTIONS

=over 4

=item B<--help>

Display help and exits

=item B<--man>

Display man page

=item B<--spec> I<file...>

List of files that make up the specification documentation docbook/XML source
files.

=item B<--filter> I<file...>

List of files that make up the filter documentation docbook/XML source files.

=item B<--web>

Generate the website from the template files.

=item B<--latest> I<version>

Specify the current exim version. This is used to create links to the current
documentation.

This option is I<required>

=item B<--tmpl> I<directory>

Specify the directory that the templates are kept in.

This option is I<required>

=item B<--docroot> I<directory>

Specify the directory that the output should be generated into. This is the
website C<docroot> directory.

This option is I<required>

=item B<--minify>

If this option is set then both the CSS and Javascript files processed are
minified using L<CSS::Minifier::XS> and L<JavaScript::Minifier::XS>
respectively.

This option is set by default - to disable it specify C<--no-minify>

=item B<--localstatic>

Makes the static files (CSS, images etc), local for each version of the
documentation. This is more suitable for packaged HTML documentation.

=back

=head1 DESCRIPTION

Generates the exim website and HTML documentation.

=head1 EXAMPLE

    script/gen.pl \
      --web \
      --spec docbook/*/spec.xml \
      --filter  docbook/*/filter.xml \
      --latest 4.72 \
      --tmpl templates \
      --docroot /tmp/website

=head1 AUTHOR

Mike Cardwell

Nigel Metheringham <nigel@exim.org> - mostly broke the framework Mike produced.

=head1 COPYRIGHT

Copyright 2010-2012 Exim Maintainers. All rights reserved.

=cut