#!perl -w
use strict;

use Getopt::Long;
use Pod::Usage;
use XML::Twig;

my $VERSION="0.9";

# options (all used globally in the script)
my( $help, $man, @roots, @paths, $files, 
    $count, $nb_results, $nb_results_per_file,
    $encoding, @exclude,
    $wrap, $nowrap, $descr, $group, $pretty_print, $version, $text_only, $date, 
    $html, $tidy, 
    $add_ns,
    $verbose, $strict
  );

# used to check if the wrapping tags need to be output
my $results      = 0;
my $file_results = 0;

# first process the case where the user provides only 
# an xpath expression and a list of files
 if( @ARGV && ($ARGV[0] !~ m{^-}) )
   { splice( @ARGV, 0, 0, '--group_by_file', 'file', '--pretty_print', 'indented', '--cond'); }

GetOptions( 'help'            => \$help,
            'man'             => \$man,
            'Version'         => \$version,
            'cond=s'          => \@paths,
            'exclude|v=s'     => \@exclude,
            'root=s'          => \@roots,
            'files'           => \$files,
            'count'           => \$count,
            'nb_results=i'    => \$nb_results,
            'by_file=i'       => \$nb_results_per_file,
            'encoding=s'      => \$encoding,
            'wrap:s'          => \$wrap,
            'nowrap'          => \$nowrap,
            'descr:s'         => \$descr,
            'group_by_file:s' => \$group,
            'pretty_print:s'  => \$pretty_print,
            'text_only'       => \$text_only,
            'date!'           => \$date,
            'strict'          => \$strict,
            'html'            => \$html,
            'tidy'            => \$tidy,
            'add_ns'          => \$add_ns,
            'verbose'         => \$verbose,
    ) or pod2usage(2);

pod2usage(1) if $help;
pod2usage(-exitstatus => 0, -verbose => 2) if $man;
if( $version) { warn "$0 version $VERSION\n"; exit; }

binmode STDOUT, ':utf8';

# case where options are given, but no root or path, assume the
# first arg is a path
if( !@roots and !@paths and !@exclude and @ARGV) { @paths= shift @ARGV; }

unless( @roots or @paths or @exclude or $files)  { pod2usage(1); exit; }
if( ($files or $count) and !@paths)  { pod2usage(1); exit; }
if( ($files or $count) and (@roots or $encoding or defined( $wrap) 
                or defined( $group) or defined( $pretty_print)))
                                     { pod2usage(1); exit; }
if( $files and !@ARGV)               { pod2usage(1); exit; }
if( !$files and !$count and @paths and !@roots) { @roots= @paths; @paths=(); }

$date=1 unless( defined $date);

# defaults for optional arguments to options
$group        = 'file'     if( defined $group        and !$group);
$pretty_print = 'indented' if( defined $pretty_print and !$pretty_print);

if( $nowrap) { $wrap=''; } elsif( !defined( $wrap) and (@roots or @paths)) { $wrap= 'xml_grep'; }

if( !defined( $descr) and (@roots or @paths))
  { if( $date)
      { $date= localtime();
        $descr        = qq{version="$VERSION" date="$date"}
      }
    else
      { $descr        = qq{version="$VERSION"}; }
  } 

# some globals
my $current_file;
my $count_file  = 0;
my $count_total = 0;
my $nb_results_left_in_current_file=0;

# will be used to create the twig
my %options;  

if( $count)
  { my $twig_roots={};
    my $twig_root= sub { $count_file++; $_[0]->purge; };
    foreach my $path (@paths)
      { $twig_roots->{$path}= $twig_root; }

    $options{twig_roots}= $twig_roots;
  }
elsif( @exclude)
  { # general options
    $nowrap=1;
    # twig options
    $options{twig_print_outside_roots} = 1;
    my $root_handlers={};
    foreach my $exclude (@exclude)
      { $root_handlers->{$exclude}= sub { }; }
    $options{twig_roots}= $root_handlers;
  }
else
  { create_regular_handlers( \%options, \@roots, \@paths);
  }
    
if( $tidy) { $html= 1; $options{use_tidy}= 1; }     


$options{pretty_print}    = $pretty_print if( $pretty_print);
$options{output_encoding} = $encoding     if( $encoding); 
     
my $t= create_twig( %options);

if( @ARGV)
  { foreach my $file (@ARGV)
      { $current_file= $file;

        if( $nb_results_per_file) { $nb_results_left_in_current_file= $nb_results_per_file; }

        if( $verbose) { warn "parsing '$file'\n"; }
        my $ok= $html && ($current_file=~ m{^(http|ftp|file)://}) ? $t->safe_parseurl_html( $file) 
              : ($current_file=~ m{^(http|ftp|file)://})          ? $t->safe_parseurl( $file) 
              : $html                                             ? $t->safe_parsefile_html( $file)
              :                                                     $t->safe_parsefile( $file);

        if( !$ok)
          { if( $@ =~ m{XMLGREP: FOUND}) 
              { # in files mode
                print $current_file, "\n";
                $nb_results--;
                exit unless( $nb_results);
              }
            elsif( $@ =~ m{^XMLGREP: NB_RESULT_REACHED})
              { print file_result_end() if( $group && $file_results);
                print result_end()      if( $results);
                exit;
              }
            else
              { $@ ||= 'unknown cause';
                if( $strict) { die $@; } 
                warn $@;
                if( !$count) { print "<!-- error parsing file '$file' -->\n"; }
              }
          }

        if( $count)    
          { print "$current_file: $count_file\n";
            $count_total += $count_file;
            $count_file=0;
          }
        elsif( @roots) { print file_result_end() if( $file_results); }
        elsif( $count) { print "$count_total matches\n"; }
      }

    if( $count) { print "total: $count_total\n"; }
    print result_end() if( $results);
  }
else
  { $file_results=0;
    my $ok= $t->safe_parse( \*STDIN);
    if( !$ok and ( $@ !~ m{^XMLGREP: NB_RESULT_REACHED}))
      { if( !$strict) { warn $@; } else { die $@; } }
    if( $count) { print "$count_total matches\n"; }
    else        { print result_end();             }
  }

sub create_regular_handlers
  { my( $options, $roots, $paths)= @_;
    if( @$roots)
      { my $root_handlers={};
        my $root_handler= twig_roots_handler( @$paths);
        foreach my $root (@$roots)
          { $root_handlers->{$root}= $root_handler; }

        $options->{twig_roots}= $root_handlers;
      }

    if( @$paths)
      { my $twig_handlers={};
        my $twig_handler= twig_handlers();
        foreach my $path (@$paths)
          { $twig_handlers->{$path}= $twig_handler; }

        $options->{twig_handlers}= $twig_handlers;
      }
  }

sub create_twig
  { my( %options)= @_;
    my $twig;
    eval { $twig= XML::Twig->new( %options) };
    if( $@)
      { # see if we are in the case where the only condition uses string() or regexp
        if( ($@=~ m{^(regexp|string\(\)) condition not supported on twig_roots option})
            && $options{twig_roots} && !$options{twig_handlers}
            && ( keys %{$options{twig_roots}} == 1)
          )
          { # in this case add the proper twig_roots option
            my $cond= (keys %{$options{twig_roots}})[0];
            (my $root= $cond)=~ s{\[[^\]]*\]$}{};
            #warn "cond: '$cond' - root: '$root'\n";
            delete $options{twig_roots};
            delete $options{twig_handlers};
            @paths= ($cond);
            @roots= ($root);
            create_regular_handlers( \%options, \@roots, \@paths);
            return create_twig( %options);
          }
        elsif( $@=~ m{^wrong condition: unrecognized expression in handler: '(.*?)'})
          { die "error in filter condition '$1'\n"; }
        else
          { die "error: $@"; }
      }
      return $twig;
  }

 
sub twig_roots_handler
  { my( @paths)= @_;
    return  sub 
              { my( $t, $root)= @_;
                if( !@paths or $_->att( '#print'))
                  { print result_start()        if( !$results); 
                    print file_result_start()   if( $group && !$file_results);
                    if( $text_only)
                      { print $root->text, "\n"; }
                    else
                      { $root->print; }
                    if( ! -- $nb_results) { $@= "XMLGREP: NB_RESULT_REACHED"; die; }
                    if( ! -- $nb_results_left_in_current_file) { $t->finish_now(); }
                  }
                $t->purge; 
                1;
              };
  }

sub twig_handlers
  { if( $files)
      { return sub { $@="XMLGREP: FOUND"; die; }; }
    else
      { return sub { my( $t, $hit)= @_;
                     foreach my $elt ( $hit->ancestors_or_self) 
                       { $elt->set_att( '#print' => 1); }
                         1;
                   };
      }
  }

sub result_start
  { $results=1;
    return if( $text_only);
    my $enc_decl= $encoding ? qq{encoding="$encoding" } : '';
    return $wrap ?  qq{<?xml version="1.0" $enc_decl?>\n<$wrap $descr>\n}
                 : '';
  }

sub result_end
  { my $result;
    return if( $text_only);
    if( !$group) { $result= "\n"; }
    $result .= qq{</$wrap>\n} if( $wrap);
    return $result;
  }

sub file_result_start
  { $file_results=1;
    return if( $text_only);
    my $result;
    $result= qq{<$group filename="$current_file">};
    if( !$pretty_print)
      { $result.= "\n"; }
    return $result;
  }

sub file_result_end
  { $file_results=0;
    return '' if( $text_only);
    return qq{\n</$group>\n};
  }



__END__

=head1 NAME

xml_grep - grep XML files looking for specific elements

=head1 SYNOPSYS

  xml_grep [options] <file list> 

or

  xml_grep <xpath expression> <file list>

By default you can just give C<xml_grep> an XPath expression and
a list of files, and get an XML file with the result.

This is equivalent to writing 

  xml_grep --group_by_file file --pretty_print indented --cond <file list>

=head1 OPTIONS

=over 4

=item B<--help>

brief help message

=item B<--man>

full documentation

=item B<--Version>

display the tool version

=item B<--root> <cond>

look for and return xml chunks matching <cond>

if neither C<--root> nor C<--file> are used then the element(s)
that trigger the C<--cond> option is (are) used. If C<--cond> is
not used then all elements matching the <cond> are returned

several C<--root> can be provided

=item B<--cond> <cond>

return the chunks (or file names) only if they contain elements matching <cond>

several C<--cond> can be provided (in which case they are OR'ed)

=item B<--files>

return only file names (do not generate an XML output)

usage of this option precludes using any of the options that define the XML output:
C<--roots>, C<--encoding>, C<--wrap>, C<--group_by_file> or C<--pretty_print>

=item B<--count>

return only the number of matches in each file

usage of this option precludes using any of the options that define the XML output:
C<--roots>, C<--encoding>, C<--wrap>, C<--group_by_file> or C<--pretty_print>

=item B<--strict>

without this option parsing errors are reported to STDOUT and the file skipped


=item B<--date>

when on (by default) the wrapping element get a C<date> attribute that gives
the date the tool was run.

with C<--nodate> this attribute is not added, which can be useful if you need
to compare 2 runs.

=item B<--encoding> <enc>

encoding of the xml output (utf-8 by default)

=item B<--nb_results> <nb>

output only <nb> results

=item B<--by_file>

output only <nb> results by file 

=item B<--wrap> <tag>

wrap the xml result in the provided tag (defaults to 'xml_grep')

If wrap is set to an empty string (C<--wrap ''>) then the xml result is not wrapped at all. 

=item B<--nowrap>

same as using C<--wrap ''>: the xml result is not wrapped. 

=item B<--descr> <string>

attributes of the wrap tag (defaults to C<< version="<VERSION>" date="<date>" >>)

=item B<--group_by_file> <optional_tag>

wrap results for each files into a separate element. By default that element 
is named C<file>. It has an attribute named C<filename> that gives the name of the 
file.

the short version of this option is B<-g>

=item B<--exclude> <condition>

same as using C<-v> in grep: the elements that match the condition are excluded
from the result, the input file(s) is (are) otherwise unchanged 

the short form of this option is B<-v>

=item B<--pretty_print> <optional_style>

pretty print the output using XML::Twig styles ('C<indented>', 'C<record>'
or 'C<record_c>' are probably what you are looking for) 

if the option is used but no style is given then 'C<indented>' is used

short form for this argument is B<-s>

=item B<--text_only>

Displays the text of the results, one by line.

=item B<--html>

Allow HTML input, files are converted using HTML::TreeBuilder

=item B<--Tidy>

Allow HTML input, files are converted using HTML::Tidy 

=back

=head2 Condition Syntax

<cond> is an XPath-like expression as allowed by XML::Twig to trigger handlers. 
 
examples: 
  'para'
  'para[@compact="compact"]'
  '*[@urgent]'
  '*[@urgent="1"]'
  'para[string()="WARNING"]'

see XML::Twig for a more complete description of the <cond> syntax

options are processed by Getopt::Long so they can start with '-' or '--'
and can be abbreviated (C<-r> instead of C<--root> for example)

=head1 DESCRIPTION

B<xml_grep> does a grep on XML files. Instead of using regular 
expressions it uses XPath expressions (in fact the subset of 
XPath supported by XML::Twig)

the results can be the names of the files or XML elements 
containing matching elements.

=head1 SEE ALSO

XML::Twig Getopt::Long

=head1 LICENSE

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=head1 AUTHOR

Michel Rodriguez <mirod@xmltwig.com>