package MediaWiki::API;

use warnings;
use strict;

# our required modules

use LWP::UserAgent;
use JSON::XS;
use Encode;
use Carp;

#use Data::Dumper;

use constant {
  ERR_NO_ERROR => 0,
  ERR_CONFIG   => 1,
  ERR_HTTP     => 2,
  ERR_API      => 3,
  ERR_LOGIN    => 4,
  ERR_EDIT     => 5,
  ERR_PARAMS   => 6,
  ERR_UPLOAD   => 7,
  ERR_DOWNLOAD => 8,

  DEF_RETRIES => 0,
  DEF_RETRY_DELAY => 0,

  DEF_MAX_LAG => undef,
  DEF_MAX_LAG_RETRIES => 4,
  DEF_MAX_LAG_DELAY => 5
};

=head1 NAME

MediaWiki::API - Provides a Perl interface to the MediaWiki API (http://www.mediawiki.org/wiki/API)

=head1 VERSION

Version 0.23

=cut

our $VERSION  = "0.23";

=head1 SYNOPSIS

This module provides an interface between Perl and the MediaWiki API (http://www.mediawiki.org/wiki/API) allowing creation of scripts to automate editing and extraction of data from MediaWiki driven sites like Wikipedia.

  use MediaWiki::API;

  my $mw = MediaWiki::API->new();
  $mw->{config}->{api_url} = 'http://en.wikipedia.org/w/api.php';

  # log in to the wiki
  $mw->login( { lgname => 'username', lgpassword => 'password' } )
    || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

  # get a list of articles in category
  my $articles = $mw->list ( {
    action => 'query',
    list => 'categorymembers',
    cmtitle => 'Category:Perl',
    cmlimit => 'max' } )
    || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

  # and print the article titles
  foreach (@{$articles}) {
      print "$_->{title}\n";
  }

  # get user info
  my $userinfo = $mw->api( {
    action => 'query',
    meta => 'userinfo',
    uiprop => 'blockinfo|hasmsg|groups|rights|options|editcount|ratelimits' } );

    ...

=head1 FUNCTIONS

=head2 MediaWiki::API->new( [ $config_hash ] )

Returns a MediaWiki API object. You can pass a config as a hashref when calling new, or set the configuration later.

  my $mw = MediaWiki::API->new( { api_url => 'http://en.wikipedia.org/w/api.php' }  );

Configuration options are

=over

=item * api_url = 'Path to mediawiki api.php';

=item * files_url = 'Base url for files'; (needed if the api returns a relative URL for images like /images/a/picture.jpg)

=item * upload_url = 'http://en.wikipedia.org/wiki/Special:Upload'; (path to the upload special page which is required if you want to upload images)

=item * on_error = Function reference to call if an error occurs in the module.

=item * retries = Integer value; The number of retries to send an API request if an http error or JSON decoding error occurs. Defaults to 0 (try only once - don't retry). If max_retries is set to 4, and the wiki is down, the error won't be reported until after the 5th connection attempt. 

=item * retry_delay = Integer value in seconds; The amount of time to wait before retrying a request if an HTTP error or JSON decoding error occurs.

=item * max_lag = Integer value in seconds; Wikipedia runs on a database cluster and as such high edit rates cause the slave servers to lag. If this config option is set then if the lag is more then the value of max_lag, the api will wait before retrying the request. 5 is a recommended value. More information about this subject can be found at http://www.mediawiki.org/wiki/Manual:Maxlag_parameter. note the config option includes an underscore so match the naming scheme of the other configuration options. 

=item * max_lag_delay = Integer value in seconds; This configuration option specified the delay to wait before retrying a request when the server has reported a lag more than the value of max_lag. This defaults to 5 if using the max_lag configuration option.

=item * max_lag_retries = Integer value; The number of retries to send an API request if the server has reported a lag more than the value of max_lag. If the maximum retries is reached, an error is returned. Setting this to a negative value like -1 will mean the request is resent until the servers max_lag is below the threshold or another error occurs. Defaults to 4.

=back

An example for the on_error configuration could be something like:

  $mw->{config}->{on_error} = \&on_error;

  sub on_error {
    print "Error code: " . $mw->{error}->{code} . "\n";
    print $mw->{error}->{stacktrace}."\n";
    die;
  }

Errors are stored in $mw->{error}->{code} with more information in $mw->{error}->{details}. $mw->{error}->{stacktrace} includes
the details and a stacktrace to locate where any problems originated from (in some code which uses this module for example).

The error codes are as follows

=over

=item * ERR_NO_ERROR = 0 (No error)

=item * ERR_CONFIG   = 1 (An error with the configuration)

=item * ERR_HTTP     = 2 (An http related connection error)

=item * ERR_API      = 3 (An error returned by the MediaWiki API)

=item * ERR_LOGIN    = 4 (An error logging in to the MediaWiki)

=item * ERR_EDIT     = 5 (An error with an editing function)

=item * ERR_PARAMS   = 6 (An error with parameters passed to a helper function)

=item * ERR_UPLOAD   = 7 (An error with the file upload facility)

=item * ERR_DOWNLOAD = 8 (An error with downloading a file)

=back

Other useful parameters and objects in the MediaWiki::API object are

=over

=item * MediaWiki::API->{ua} = The LWP::UserAgent object. You could modify this to get or modify the cookies (MediaWiki::API->{ua}->cookie_jar) or to change the UserAgent string sent by this perl module (MediaWiki::API->{ua}->agent)

=item * MediaWiki::API->{response} = the last response object returned by the LWP::UserAgent after an API request.

=back

=cut

sub new {

  my ($class, $config) = @_;
  my $self = { config => $config  };

  my $ua = LWP::UserAgent->new();
  $ua->cookie_jar({});
  $ua->agent(__PACKAGE__ . "/$VERSION");
  $ua->default_header("Accept-Encoding" => "gzip, deflate");

  $self->{ua} = $ua;

  my $json = JSON::XS->new->utf8()->max_depth(10) ;
  $self->{json} = $json;

  # initialise some defaults
  $self->{error}->{code} = 0;
  $self->{error}->{details} = '';
  $self->{error}->{stacktrace} = '';

  $self->{config}->{retries} = DEF_RETRIES;
  $self->{config}->{retry_delay} = DEF_RETRY_DELAY;

  $self->{config}->{max_lag} = DEF_MAX_LAG;
  $self->{config}->{max_lag_retries} = DEF_MAX_LAG_RETRIES;
  $self->{config}->{max_lag_delay} = DEF_MAX_LAG_DELAY;

  bless ($self, $class);
  return $self;
}

=head2 MediaWiki::API->login( $query_hash )

Logs in to a MediaWiki. Parameters are those used by the MediaWiki API (http://www.mediawiki.org/wiki/API:Login). Returns a hash with some login details, or undef on login failure. Errors are stored in MediaWiki::API->{error}->{code} and MediaWiki::API->{error}->{details}.

  my $mw = MediaWiki::API->new( { api_url => 'http://en.wikipedia.org/w/api.php' }  );

  #log in to the wiki
  $mw->login( {lgname => 'username', lgpassword => 'password' } )
    || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

=cut

sub login {
  my ($self, $query) = @_;
  $query->{action} = 'login';
  # attempt to login, and return undef if there was an api failure
  return undef unless ( my $ref = $self->api( $query ) );

  # reassign hash reference to the login section
  my $login = $ref->{login};
  return $self->_error( ERR_LOGIN, 'Login Failure - ' . $login->{result} )
    unless ( $login->{result} eq 'Success' );

  # everything was ok so return the reference
  return $login;
}

=head2 MediaWiki::API->api( $query_hash, $options_hash )

Call the MediaWiki API interface. Parameters are passed as a hashref which are described on the MediaWiki API page (http://www.mediawiki.org/wiki/API). returns a hashref with the results of the call or undef on failure with the error code and details stored in MediaWiki::API->{error}->{code} and MediaWiki::API->{error}->{details}. MediaWiki::API uses the LWP::UserAgent module to send the http requests to the MediaWiki API. After any API call, the response object returned by LWP::UserAgent is available in $mw->{response};

  binmode STDOUT, ':utf8';

  # get the name of the site
  if ( my $ref = $mw->api( { action => 'query', meta => 'siteinfo' } ) ) {
    print $ref->{query}->{general}->{sitename};
  }

  # list of titles for "Albert Einstein" in different languages.
  my $titles = $mw->api( {
    action => 'query',
    titles => 'Albert Einstein',
    prop => 'langlinks',
    lllimit => 'max' } )
    || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

  my ($pageid,$langlinks) = each ( %{ $titles->{query}->{pages} } );

  foreach ( @{ $langlinks->{langlinks} } ) {
    print "$_->{'*'}\n";
  }

Parameters are encoded from perl strings to UTF-8 to be passed to Mediawiki automatically, which is normally what you would want. In case for any reason your parameters are already in UTF-8 you can skip the encoding by passing an option skip_encoding => 1 in the $options_hash. For example:

  # $data already contains utf-8 encoded wikitext
  my $ref = $mw->api( { action => 'parse', text => $data }, { skip_encoding => 1 } );

=cut

sub api {
  my ($self, $query, $options) = @_;

  unless ( $options->{skip_encoding} ) {
    $self->_encode_hashref_utf8($query);
  }

  my $retries = $self->{config}->{retries};
  my $maxlagretries = $self->{config}->{max_lag_retries};

  $query->{maxlag} = $self->{config}->{max_lag} if defined $self->{config}->{max_lag}; 

  return $self->_error(ERR_CONFIG,"You need to give the URL to the mediawiki API php.")
    unless $self->{config}->{api_url};

  $query->{format}='json';

  my $ref;
  while (1) {

    # connection retry loop.
    foreach my $try (0 .. $retries) {

      # if we are already retrying, then wait the specified delay
      if ( $try > 0 ) {
        sleep $self->{config}->{retry_delay};
      }

      my $response = $self->{ua}->post( $self->{config}->{api_url}, $query );
      $self->{response} = $response;
      
      # if the request was successful then check the returned content and decode.
      if ( $response->is_success ) {
        
        my $decontent = $response->decoded_content( charset => 'none' );

        if ( ! defined $decontent ) {
          return $self->_error(ERR_HTTP,"Unable to decode content returned by $self->{config}->{api_url} - Unknown content encoding?")
            if ( $try == $retries );
          next;
        }
        
        if ( length $decontent == 0 ) {
          return $self->_error(ERR_HTTP,"$self->{config}->{api_url} returned a zero length string")
            if ( $try == $retries );
          next;
        }

        # decode the json trapping any errors
        eval {
          $ref = $self->{json}->decode($decontent);
        };

        if ( $@) {
          # an error occurred, so we check if we need to retry and continue
          my $error = $@;
          return $self->_error(ERR_HTTP,"Failed to decode JSON returned by $self->{config}->{api_url}\nDecoding Error:\n$error\nReturned Data:\n$decontent")
            if ( $try == $retries );
          next;
        } else {
          # no error so we want out of the retry loop
          last;
        }

      # if the request was not successful then we retry or return a failure if the maximum retries
      # have been reached, otherwise we try again
      } else {
        return $self->_error(ERR_HTTP, $response->status_line . " : error occurred when accessing $self->{config}->{api_url} after " . ($try+1) . " attempt(s)")
          if ( $try == $retries );
        next;
      }       
      
    }

    return $self->_error(ERR_API,"API has returned an empty array reference. Please check your parameters") if ( ref($ref) eq 'ARRAY' && scalar @{$ref} == 0);

    # check lag and wait
    if (ref($ref) eq 'HASH' && exists $ref->{error} && $ref->{error}->{code} eq 'maxlag' ) {
      $ref->{'error'}->{'info'} =~ /: (\d+) seconds lagged/;
      my $lag = $1;
      if ($maxlagretries == 0) {
        return $self->_error(ERR_API,"Server has reported lag above the configure max_lag value of " . $self->{config}->{max_lag} . " value after " .($maxlagretries+1)." attempt(s). Last reported lag was - ". $ref->{'error'}->{'info'})
      } else {
        sleep $self->{config}->{max_lag_delay};
        $maxlagretries-- if $maxlagretries > 0;
        # redo the request
        next;
      }

    }

    # if we got this far, then we have a hashref from the api and we want out of the while loop
    last;

  }

  return $self->_error(ERR_API,$ref->{error}->{code} . ": " . $ref->{error}->{info} ) if ( ref($ref) eq 'HASH' && exists $ref->{error} );

  return $ref;
}

=head2 MediaWiki::API->logout()

Log the current user out and clear associated cookies and edit tokens.

=cut

sub logout {
  my ($self) = @_;
  # clear login cookies
  $self->{ua}->{cookie_jar} = undef;
  # clear cached tokens
  $self->{config}->{tokens} = undef;
}

=head2 MediaWiki::API->edit( $query_hash )

A helper function for doing edits using the MediaWiki API. Parameters are passed as a hashref which are described on the MediaWiki API editing page (http://www.mediawiki.org/wiki/API:Changing_wiki_content). Note that you need $wgEnableWriteAPI = true in your LocalSettings.php to use these features.

Currently only

=over

=item * Create/Edit pages (Mediawiki >= 1.13 )

=item * Move pages  (Mediawiki >= 1.12 )

=item * Rollback  (Mediawiki >= 1.12 )

=item * Delete pages  (Mediawiki >= 1.12 )

=back

are supported via this call. Use this call to edit pages without having to worry about getting an edit token from the API first. The function will cache edit tokens to speed up future edits (Except for rollback edits, which are not cachable).

Returns a hashref with the results of the call or undef on failure with the error code and details stored in MediaWiki::API->{error}->{code} and MediaWiki::API->{error}->{details}.

Here are some example snippets of code. The first example is for adding some text to an existing page (if the page doesn't exist nothing will happen). Note that the timestamp for the revision we are changing is saved. This allows us to avoid edit conflicts. The value is passed back to the edit function, and if someone had edited the page in the meantime, an error will be returned.

  my $pagename = "Wikipedia:Sandbox";
  my $ref = $mw->get_page( { title => $pagename } );
  unless ( $ref->{missing} ) {
    my $timestamp = $ref->{timestamp};
    $mw->edit( {
      action => 'edit',
      title => $pagename,
      basetimestamp => $timestamp, # to avoid edit conflicts
      text => $ref->{'*'} . "\nAdditional text" } )
      || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};
  }

The following code deletes a page with the name "DeleteMe". You can specify a reason for the deletion, otherwise
a generated reason will be used.

  # delete a page
  $mw->edit( {
    action => 'delete', title => 'DeleteMe', reason => 'no longer needed' } ) 
    || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

This code moves a page from MoveMe to MoveMe2.

  # move a page
  $mw->edit( {
    action => 'move', from => 'MoveMe', to => 'MoveMe2' } )
    || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

The following scrippet rolls back one or more edits from user MrVandal. If the user is not the last editor of the page, an error will be returned. If no user is passed, the edits for whoever last changed the page will be rolled back.

  $mw->edit( {
    action => 'rollback', title => 'Sandbox', user => 'MrVandal' } )
    || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

=cut

sub edit {
  my ($self, $query) = @_;

  # gets and sets a token for the specific action (different tokens for different edit actions such as rollback/delete etc). Also sets the timestamp for edits to avoid conflicts.
  return undef unless ( $self->_get_set_tokens( $query ) );

  # do the edit
  return undef unless ( my $ref = $self->api( $query ) );

  return $ref;
}


=head2 MediaWiki::API->get_page( $params_hash )

A helper function for getting the most recent page contents (and other metadata) for a page. It calls the lower level api function with a revisions query to get the most recent revision.

  # get some page contents
  my $page = $mw->get_page( { title => 'Main Page' } );
  # print page contents
  print $page->{'*'};

Returns a hashref with the following keys or undef on an error. If the page is missing then the returned hashref will contain only ns, title and a key called "missing".

=over

=item * '*' - contents of page

=item * 'pageid' - page id of page

=item * 'revid' - revision id of page

=item * 'timestamp' - timestamp of revision

=item * 'user' - user who made revision

=item * 'title' - the title of the page

=item * 'ns' - the namespace the page is in

=item * 'size' - size of page in bytes

=back

Full information about these can be read on (http://www.mediawiki.org/wiki/API:Query_-_Properties#revisions_.2F_rv)

=cut

sub get_page {
  my ($self, $params) = @_;
  return undef unless ( my $ref = $self->api( { action => 'query', prop => 'revisions', titles => $params->{title}, rvprop => 'ids|flags|timestamp|user|comment|size|content' } ) );
  # get the page id and the page hashref with title and revisions
  my ($pageid, $pageref) = each %{ $ref->{query}->{pages} };
  # get the first revision
  my $rev = @{ $pageref->{revisions } }[0];
  # delete the revision from the hashref
  delete($pageref->{revisions});
  # if the page is missing then return the pageref
  return $pageref if ( defined $pageref->{missing} );
  # combine the pageid, the latest revision and the page title into one hash
  return { 'pageid'=>$pageid, %{ $rev }, %{ $pageref } };
}

=head2 MediaWiki::API->list( $query_hash, $options_hash )

A helper function for getting lists using the MediaWiki API. Parameters are passed as a hashref which are described on the MediaWiki API editing page (http://www.mediawiki.org/wiki/API:Query_-_Lists).

This function will return a reference to an array of hashes or undef on failure. It handles getting lists of data from the MediaWiki api, continuing the request with another connection if needed. The options_hash currently has two parameters:

=over

=item * max => value

=item * hook => \&function_hook

=back

The value of max specifies the maximum "queries" which will be used to pull data out. For example the default limit per query is 10 items, but this can be raised to 500 for normal users and higher for sysops and bots. If the limit is raised to 500 and max was set to 2, a maximum of 1000 results would be returned.

If you wish to process large lists, for example the articles in a large category, you can pass a hook function, which will be passed a reference to an array of results for each query connection.

  binmode STDOUT, ':utf8';

  # process the first 400 articles in the main namespace in the category "Surnames".
  # get 100 at a time, with a max of 4 and pass each 100 to our hook.
  $mw->list ( { action => 'query',
                list => 'categorymembers',
                cmtitle => 'Category:Surnames',
                cmnamespace => 0,
                cmlimit=>'100' },
              { max => 4, hook => \&print_articles } )
  || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

  # print the name of each article
  sub print_articles {
    my ($ref) = @_;
    foreach (@$ref) {
      print "$_->{title}\n";
    }
  }

=cut

sub list {
  my ($self, $query, $options) = @_;
  my ($ref, @results);
  my ($cont_key, $cont_value, $array_key);

  my $list = $query->{list};

  $options->{max} = 0 if ( !defined $options->{max} );

  my $continue = 0;
  my $count = 0;
  do {
    return undef unless ( $ref = $self->api( $query ) );

    # return (empty) array if results are empty
    return @results unless ( $ref->{query}->{$list} );

    # check if there are more results to be had
    if ( exists( $ref->{'query-continue'} ) ) {
      # get query-continue hashref and extract key and value (key will be used as from parameter to continue where we left off)
      ($cont_key, $cont_value) = each( %{ $ref->{'query-continue'}->{$list} } );
      $query->{$cont_key} = $cont_value;
      $continue = 1;
    } else {
      $continue = 0;
    }

    if ( defined $options->{hook} ) {
      $options->{hook}( $ref->{query}->{$list} );
    } else {
      push @results, @{ $ref->{query}->{$list} };
    }

    $count += 1;

  } until ( ! $continue || $count >= $options->{max} && $options->{max} != 0 );

  return 1 if ( defined $options->{hook} ); 
  return \@results;

}

=head2 MediaWiki::API->upload( $params_hash )

A function to upload files to a MediaWiki. This function does not use the MediaWiki API currently as support for file uploading is not yet implemented. Instead it uploads using the Special:Upload page, and as such an additional configuration value is needed.

  my $mw = MediaWiki::API->new( {
   api_url => 'http://en.wikipedia.org/w/api.php' }  );
  # configure the special upload location.
  $mw->{config}->{upload_url} = 'http://en.wikipedia.org/wiki/Special:Upload';

The upload function is then called as follows

  # upload a file to MediaWiki
  open FILE, "myfile.jpg" or die $!;
  binmode FILE;
  my ($buffer, $data);
  while ( read(FILE, $buffer, 65536) )  {
    $data .= $buffer;
  }
  close(FILE);

  $mw->upload( { title => 'file.jpg',
                 summary => 'This is the summary to go on the Image:file.jpg page',
                 data => $data } ) || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

Error checking is limited. Also note that the module will force a file upload, ignoring any warning for file size or overwriting an old file.

=cut

sub upload {
  my ($self, $params) = @_;

  return $self->_error(ERR_CONFIG,"You need to give the URL to the mediawiki Special:Upload page.") unless $self->{config}->{upload_url};

  my $response = $self->{ua}->post(
    $self->{config}->{upload_url},
    Content_Type => 'multipart/form-data',
    Content => [
      wpUploadFile => [ undef, $params->{title}, Content => $params->{data} ],
      wpSourceType => 'file',
      wpDestFile => $params->{title},
      wpUploadDescription => $params->{summary},
      wpUpload => 'Upload file',
      wpIgnoreWarning => 'true', ]
  );

  return $self->_error(ERR_UPLOAD,"There was a problem uploading the file - $params->{title}") unless ( $response->code == 302 );
  return 1;

}

=head2 MediaWiki::API->download( $params_hash )

A function to download images/files from a MediaWiki. A file url may need to be configured if the api returns a relative URL.

  my $mw = MediaWiki::API->new( {
    api_url => 'http://www.exotica.org.uk/mediawiki/api.php' }  );
  # configure the file url. Wikipedia doesn't need this but the ExoticA wiki does.
  $mw->{config}->{files_url} = 'http://www.exotica.org.uk';

The download function is then called as follows

  my $file = $mw->download( { title => 'Image:Mythic-Beasts_Logo.png'} )
    || die $mw->{error}->{code} . ': ' . $mw->{error}->{details};

If the file does not exist (on the wiki) an empty string is returned. If the file is unable to be downloaded undef is returned.

=cut

sub download {
  my ($self, $params) = @_;

  return $self->_error(ERR_PARAMS,"You need to give a name for the Image page") unless
    ( defined $params->{title} );

  return undef unless my $ref = $self->api(
    { action => 'query',
      titles => $params->{title},
      prop   => 'imageinfo',
      iiprop => 'url' } );

  # get the page id and the page hashref with title and revisions
  my ( $pageid, $pageref ) = each %{ $ref->{query}->{pages} };

  # if the page is missing then return an empty string
  return '' if ( defined $pageref->{missing} );

  my $url = @{ $pageref->{imageinfo} }[0]->{url};

  unless ( $url =~ /^http\:\/\// ) {
    return $self->_error(ERR_PARAMS,'The API returned a relative path. You need to configure the url where files are stored in {config}->{files_url}')
      unless ( defined $self->{config}->{files_url} );
    $url = $self->{config}->{files_url} . $url;
  }

  my $response = $self->{ua}->get($url);
  return $self->_error(ERR_DOWNLOAD,"The file '$url' was not found")
    unless ( $response->code == 200 );

  return $response->decoded_content;
}

# encodes a hash (passed by reference) to utf-8
# used to encode parameters before being passed to the api
sub _encode_hashref_utf8 {
  my ($self, $ref) = @_;
  for my $key ( keys %{$ref} ) {
    $ref->{$key} = encode_utf8( $ref->{$key} ) if defined $ref->{$key};
  }
}

# gets a token for a specified parameter and sets it in the query for the call
sub _get_set_tokens {
  my ($self, $query) = @_;
  my ($prop, $title, $token);
  my $action = $query->{action};

  # check if we have a cached token.
  if ( exists( $self->{config}->{tokens}->{$action} ) ) {
    $query->{token} = $self->{config}->{tokens}->{$action};
    return 1;
  }

  # set the properties we want to extract based on the action
  # for edit we want to get the datestamp of the last revision also to avoid edit conflicts
  $prop = 'info|revisions' if ( $action eq 'edit' );
  $prop = 'info' if ( $action eq 'move' or $action eq 'delete' );
  $prop = 'revisions' if ( $query->{action} eq 'rollback' );

  if ( $action eq 'move' ) {
    $title = $query->{from};
  } else {
    $title = $query->{title};
  }

  if ( $action eq 'rollback' ) {
    $token = 'rvtoken';
  } else {
    $token = 'intoken';
  }

  return undef unless ( my $ref = $self->api( { action => 'query', prop => 'info|revisions', $token => $action, titles => $title } ) );

  my ($pageid, $pageref) = each %{ $ref->{query}->{pages} };

  # if the page doesn't exist and we aren't editing/creating a new page then return an error
  return $self->_error( ERR_EDIT, "Unable to $action page '$title'. Page does not exist.") if ( defined $pageref->{missing} && $action ne 'edit' );

  if ( $action eq 'rollback' ) {
    $query->{token} = @{ $pageref->{revisions} }[0]->{$action.'token'};
    my $lastuser = @{ $pageref->{revisions} }[0]->{user};
    $query->{user} = @{ $pageref->{revisions} }[0]->{user} unless defined $query->{user};
    return $self->_error( ERR_EDIT, "Unable to rollback edits from user '$query->{user}' for page '$title'. Last edit was made by user $lastuser" ) if ( $query->{user} ne $lastuser );
  } else {
    $query->{token} = $pageref->{$action.'token'};
  }

  return $self->_error( ERR_EDIT, "Unable to get an edit token for action '$action'." ) unless ( defined $query->{token} );

  # cache the token. rollback tokens are specific for the page name and last edited user so can not be cached.
  if ( $action ne 'rollback' ) {
    $self->{config}->{tokens}->{$action} = $query->{token};
  }

  return 1;
}

sub _error {
  my ($self, $code, $desc) = @_;
  $self->{error}->{code} = $code;
  $self->{error}->{details} = $desc;
  $self->{error}->{stacktrace} = Carp::longmess($desc);

  $self->{config}->{on_error}->() if (defined $self->{config}->{on_error});

  return undef;
}

__END__

=head1 AUTHOR

Jools 'BuZz' Smyth, C<< <buzz [at] exotica.org.uk> >>

=head1 BUGS

Please report any bugs or feature requests to C<bug-mediawiki-api at rt.cpan.org>, or through
the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=MediaWiki-API>.  I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

=head1 SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc MediaWiki::API


You can also look for information at:

=over 4

=item * RT: CPAN's request tracker

L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=MediaWiki-API>

=item * AnnoCPAN: Annotated CPAN documentation

L<http://annocpan.org/dist/MediaWiki-API>

=item * CPAN Ratings

L<http://cpanratings.perl.org/d/MediaWiki-API>

=item * Search CPAN

L<http://search.cpan.org/dist/MediaWiki-API>

=back


=head1 ACKNOWLEDGEMENTS

=over

=item * Carl Beckhorn (cbeckhorn [at] fastmail.fm) for ideas and support

=item * Stuart 'Kyzer' Caie (kyzer [at] 4u.net) for UnExoticA perl code and support

=item * Edward Chernenko (edwardspec [at] gmail.com) for his earlier MediaWiki module

=item * Dan Collins (EN.WP.ST47 [at] gmail.com) for bug reports and patches

=item * Jonas 'Spectral' Nyren (spectral [at] ludd.luth.se) for hints and tips!

=item * Jason 'XtC' Skelly (xtc [at] amigaguide.org) for moral support

=back

=head1 COPYRIGHT & LICENSE

Copyright 2008 Jools Smyth, all rights reserved.

This library 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 3 of the License, or
(at your option) any later version.

This library 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, see <http://www.gnu.org/licenses/>.

=cut

1; # End of MediaWiki::API
