NAME

    WWW::Mechanize::Chrome::DOMops - Operations on the DOM loaded in Chrome

VERSION

    Version 0.06

SYNOPSIS

    This module provides a set of tools to operate on the DOM loaded onto
    the provided <WWW::Mechanize::Chrome> object after fetching a URL.

    Operating on the DOM is powerful but there are security risks involved
    if the browser and profile you used for loading this DOM is your
    everyday browser and profile.

    Please read "SECURITY WARNING" before continuing on to the main course.

    Currently, WWW::Mechanize::Chrome::DOMops provides these tools:

      * find() : finds HTML elements,

      * zap() : deletes HTML elements.

    Both find() and zap() return some information from each match and its
    descendents (like tag, id etc.). This information can be tweaked by the
    caller. find() and zap() optionally execute javascript code on each
    match and its descendents and can return data back to the caller perl
    code.

    The selection of the HTML elements in the DOM can be done in various
    ways:

      * by CSS selector,

      * by tag,

      * by class.

      * by id,

      * by name.

    There is more information about this in section "ELEMENT SELECTORS".

    Here are some usage scenaria:

        use WWW::Mechanize::Chrome::DOMops qw/zap find VERBOSE_DOMops/;
    
        # adjust verbosity: 0, 1, 2, 3
        $WWW::Mechanize::Chrome::VERBOSE_DOMops = 3;
    
        # First, create a mech object and load a URL on it
        # Note: you need google-chrome binary installed in your system!
        # See section CREATING THE MECH OBJECT for creating the mech
        # and how to redirect its javascript console to perl's output
        my $mechobj = WWW::Mechanize::Chrome->new();
        # fetch a page which will setup a DOM on which to operate:
        $mechobj->get('https://www.bbbbbbbbb.com');
    
        # find elements in the DOM, select by id, tag, name, or 
        # by CSS selector.
        my $ret = find({
           'mech-obj' => $mechobj,
           # find elements whose class is in the provided
           # scalar class name or array of class names
           'element-class' => ['slanted-paragraph', 'class2', 'class3'],
           # *OR* their tag is this:
           'element-tag' => 'p',
           # *OR* their name is this:
           'element-name' => ['aname', 'name2'],
           # *OR* their id is this:
           'element-id' => ['id1', 'id2'],
           # *OR* just provide a CSS selector and get done with it already
           # the best choice
           'element-cssselector' => 'a-css-selector',
           # specifies that we should use the union of the above sets
           # hence the *OR* in above comment
           '||' => 1,
           # this says to find all elements whose class
           # is such-and-such AND element tag is such-and-such
           # '&&' => 1 means to calculate the INTERSECTION of all
           # individual matches.
    
           # build the information sent back from each match
           'element-information-from-matched' => <<'EOJ',
    // begin JS code to extract information from each match and return it
    // back as a hash
    const r = htmlElement.hasAttribute("role")
      ? htmlElement.getAttribute("role") : "<no role present>"
    ;
    return {"tag" : htmlElement.tagName, "id" : htmlElement.id, "role" : r};
    EOJ
           # optionally run javascript code on all those elements matched
           'find-cb-on-matched' => [
             {
               'code' =><<'EOJS',
      // the element to operate on is 'htmlElement'
      console.log("operating on this element "+htmlElement.tagName);
      // this is returned back in the results of find() under
      // key "cb-results"->"find-cb-on-matched"
      return 1;
    EOJS
               'name' => 'func1'
             }, {...}
           ],
           # optionally run javascript code on all those elements
           # matched AND THEIR CHILDREN too!
           'find-cb-on-matched-and-their-children' => [
             {
               'code' =><<'EOJS',
      // the element to operate on is 'htmlElement'
      console.log("operating on this element "+htmlElement.tagName);
      // this is returned back in the results of find() under
      // key "cb-results"->"find-cb-on-matched" notice the complex data
      return {"abc":"123",{"xyz":[1,2,3]}};
    EOJS
               'name' => 'func2'
             }
           ],
           # optionally ask it to create a valid id for any HTML
           # element returned which does not have an id.
           # The text provided will be postfixed with a unique
           # incrementing counter value 
           'insert-id-if-none' => '_prefix_id',
           # or ask it to randomise that id a bit to avoid collisions
           'insert-id-if-none-random' => '_prefix_id',
    
           # optionally, also output the javascript code to a file for debugging
           'js-outfile' => 'output.js',
        });
    
    
        # Delete an element from the DOM
        $ret = zap({
           'mech-obj' => $mechobj,
           'element-id' => 'paragraph-123'
        });
    
        # Mass murder:
        $ret = zap({
           'mech-obj' => $mechobj,
           'element-tag' => ['div', 'span', 'p'],
           '||' => 1, # the union of all those matched with above criteria
        });
    
        # error handling
        if( $ret->{'status'} < 0 ){ die "error: ".$ret->{'message'} }
        # status of -3 indicates parameter errors,
        # -2 indicates that eval of javascript code inside the mech object
        # has failed (syntax errors perhaps, which could have been introduced
        # by user-specified callback
        # -1 indicates that javascript code executed correctly but
        # failed somewhere in its logic.
    
        print "Found " . $ret->{'status'} . " matches which are: "
        # ... results are in $ret->{'found'}->{'first-level'}
        # ... and also in $ret->{'found'}->{'all-levels'}
        # the latter contains a recursive list of those
        # found AND ALL their children

EXPORT

    the sub to find element(s) in the DOM

        find()

    the sub to delete element(s) from the DOM

        zap()

    and the flag to denote verbosity (default is 0, no verbosity)

        $WWW::Mechanize::Chrome::DOMops::VERBOSE_DOMops

SUBROUTINES/METHODS

 find($params)

    It finds HTML elements in the DOM currently loaded on the
    parameters-specified WWW::Mechanize::Chrome object. The parameters are:

      * mech-obj : user must supply a WWW::Mechanize::Chrome object, this
      is required. See section "CREATING THE MECH OBJECT" for an example of
      creating the mech object with some parameters which work for me and
      javascript console output propagated on to perl's output.

      * element-information-from-matched : optional javascript code to be
      run on each HTML element matched in order to construct the
      information data whih is returned back. If none specified the
      following default will be used, which returns tagname and id:

         // the matched element is provided in htmlElement
         return {"tag" : htmlElement.tagName, "id" : htmlElement.id};

      Basically the code is expected to be the body of a function which
      accepts one parameter: htmlElement (that is the element matched).
      That means it must not have the function preamble (function name,
      signature, etc.). Neither it must have the postamble, which is the
      end-block curly bracket. This piece of code must return a HASH. The
      code can throw exceptions which will be caught (because the code is
      run within a try-catch block) and the error message will be
      propagated to the perl code with status of -1.

      * insert-id-if-none : some HTML elements simply do not have an id
      (e.g. <p>). If any of these elements is matched, its tag and its id
      (empty string) will be returned. By specifying this parameter (as a
      string, e.g. _replacing_empty_ids) all such elements matched will
      have their id set to _replacing_empty_ids_X where X is an
      incrementing counter value starting from a random number. By running
      find() more than once on the same on the same DOM you are risking
      having the same ID. So provide a different prefix every time. Or use
      insert-id-if-none-random, see below.

      * insert-id-if-none-random : each time find() is called a new random
      base id will be created formed by the specified prefix (as with
      insert-id-if-none) plus a long random string plus the incrementing
      counter, as above. This is supposed to be better at avoiding
      collisions but it can not guarantee it. If you are setting rand()'s
      seed to the same number before you call find() then you are
      guaranteed to have collisions.

      * find-cb-on-matched : an array of user-specified javascript code to
      be run on each element matched in the order the elements are returned
      and in the order of the javascript code in the specified array. Each
      item of the array is a hash with keys code and name. The former
      contains the code to be run assuming that the html element to operate
      on is named htmlElement. The code must end with a return statement
      which will be recorded and returned back to perl code. The code can
      throw exceptions which will be caught (because the callback is run
      within a try-catch block) and the error message will be propagated to
      the perl code with status of -1. Basically the code is expected to be
      the body of a function which accepts one parameter: htmlElement (that
      is the element matched). That means it must not have the function
      preamble (function name, signature, etc.). Neither it must have the
      postamble, which is the end-block curly bracket.

      Key name is just for making this process more descriptive and will be
      printed on log messages and returned back with the results. name can
      contain any characters. Here is an example:

          'find-cb-on-matched' : [
            {
              # this returns a complex data type
              'code' => 'console.log("found id "+htmlElement.id); return {"a":"1","b":"2"};'
              'name' => 'func1'
            },
            {
              'code' => 'console.log("second func: found id "+htmlElement.id); return 1;'
              'name' => 'func2'
            },
          ]

      * find-cb-on-matched-and-their-children : exactly the same as
      find-cb-on-matched but it operates on all those HTML elements matched
      and also all their children and children of children etc.

      * js-outfile : optionally save the javascript code (which is
      evaluated within the mech object) to a file.

      * element selectors are covered in section "ELEMENT SELECTORS".

    JAVASCRIPT HELPERS

    There is one javascript function available to all user-specified
    callbacks:

      * getAllChildren(anHtmlElement) : it returns back an array of HTML
      elements which are the children (at any depth) of the given
      anHtmlElement.

    RETURN VALUE:

    The returned value is a hashref with at least a status key which is
    greater or equal to zero in case of success and denotes the number of
    matched HTML elements. Or it is -3, -2 or -1 in case of errors:

      * -3 : there is an error with the parameters passed to this sub.

      * -2 : there is a syntax error in the javascript code to be evaluated
      by the mech object with something like $mech_obj-eval()>. Most likely
      this syntax error is with user-specified callback code. Note that all
      the javascript code to be evaluated is dumped to stderr by increasing
      the verbosity. But also it can be saved to a local file for easier
      debugging by supplying the js-outfile parameter to find() or zap().

      * -1 : there is a logical error while running the javascript code.
      For example a division by zero etc. This can be both in the callback
      code as well as in the internal javascript code for edge cases not
      covered by my tests. Please report these. Note that all the
      javascript code to be evaluated is dumped to stderr by increasing the
      verbosity. But also it can be saved to a local file for easier
      debugging by supplying the js-outfile parameter to find() or zap().

    If status is not negative, then this is success and its value denotes
    the number of matched HTML elements. Which can be zero or more. In this
    case the returned hash contains this

        "found" => {
          "first-level" => [
            {
              "tag" => "NAV",
              "id" => "nav-id-1"
            }
          ],
          "all-levels" => [
            {
              "tag" => "NAV",
              "id" => "nav-id-1"
            },
            {
              "id" => "li-id-2",
              "tag" => "LI"
            },
          ]
        }

    Key first-level contains those items matched directly while key
    all-levels contains those matched directly as well as those matched
    because they are descendents (direct or indirect) of each matched
    element.

    Each item representing a matched HTML element has two fields: tag and
    id. Beware of missing id or use insert-id-if-none or
    insert-id-if-none-random to fill in the missing ids.

    If find-cb-on-matched or find-cb-on-matched-and-their-children were
    specified, then the returned result contains this additional data:

     "cb-results" => {
        "find-cb-on-matched" => [
          [
            {
              "name" => "func1",
              "result" => {
                "a" => 1,
                "b" => 2
              }
            }
          ],
          [
            {
              "result" => 1,
              "name" => "func2"
            }
          ]
        ],
        "find-cb-on-matched-and-their-children" => ...
      },

    find-cb-on-matched and/or find-cb-on-matched-and-their-children will be
    present depending on whether corresponding value in the input
    parameters was specified or not. Each of these contain the return
    result for running the callback on each HTML element in the same order
    as returned under key found.

    HTML elements allows for missing id. So field id can be empty unless
    caller set the insert-id-if-none input parameter which will create a
    unique id for each HTML element matched but with missing id. These
    changes will be saved in the DOM. When this parameter is specified, the
    returned HTML elements will be checked for duplicates because now all
    of them have an id field. Therefore, if you did not specify this
    parameter results may contain duplicate items and items with empty id
    field. If you did specify this parameter then some elements of the DOM
    (those matched by our selectors) will have their missing id created and
    saved in the DOM.

    Another implication of using this parameter when running it twice or
    more with the same value is that you can get same ids. So, always
    supply a different value to this parameter if run more than once on the
    same DOM.

 zap($params)

    It removes HTML element(s) from the DOM currently loaded on the
    parameters-specified WWW::Mechanize::Chrome object. The params are
    exactly the same as with "find($params)" except that insert-id-if-none
    is ignored.

    zap() is implemented as a find() with an additional callback for all
    elements matched in the first level (not their children) as:

      'find-cb-on-matched' => {
        'code' => 'htmlElement.parentNode.removeChild(htmlElement); return 1;',
        'name' => '_thezapper'
       };

    RETURN VALUE:

    Return value is exactly the same as with "find($params)"

 $WWW::Mechanize::Chrome::DOMops::VERBOSE_DOMops

    Set this upon loading the module to 0, 1, 2, 3 to adjust verbosity. 0
    implies no verbosity.

ELEMENT SELECTORS

    Element selectors are how one selects HTML elements from the DOM. There
    are 5 ways to select HTML elements: by id, class, tag, name or via a
    CSS selector. Multiple selectors can be specified as well as multiple
    criteria in each selector (e.g. multiple class names in a element-class
    selector). The results from each selector are combined into a list of
    unique HTML elements (BEWARE of missing id fields) by means of UNION or
    INTERSECTION of the individual matches

    These are the valid selectors:

      * element-class : find DOM elements matching this class name

      * element-tag : find DOM elements matching this element tag

      * element-id : find DOM element matching this element id

      * element-name : find DOM element matching this element name

      * element-cssselector : find DOM element matching this CSS selector

    And one of these two must be used to combine the results into a final
    list

      * && : Intersection. When set to 1 the result is the intersection of
      all individual results. Meaning that an element will make it to the
      final list if it was matched by every selector specified. This is the
      default.

      * || : Union. When set to 1 the result is the union of all individual
      results. Meaning that an element will make it to the final list if it
      was matched by at least one of the selectors specified.

CREATING THE MECH OBJECT

    The mech (WWW::Mechanize::Chrome) object must be supplied to the
    functions in this module. It must be created by the caller. This is how
    I do it:

        use WWW::Mechanize::Chrome;
        use Log::Log4perl qw(:easy);
        Log::Log4perl->easy_init($ERROR);
    
        my %default_mech_params = (
            headless => 1,
        #   log => $mylogger,
            launch_arg => [
                    '--window-size=600x800',
                    '--password-store=basic', # do not ask me for stupid chrome account password
        #           '--remote-debugging-port=9223',
        #           '--enable-logging', # see also log above
                    '--disable-gpu',
                    '--no-sandbox',
                    '--ignore-certificate-errors',
                    '--disable-background-networking',
                    '--disable-client-side-phishing-detection',
                    '--disable-component-update',
                    '--disable-hang-monitor',
                    '--disable-save-password-bubble',
                    '--disable-default-apps',
                    '--disable-infobars',
                    '--disable-popup-blocking',
            ],
        );
    
        my $mech_obj = eval {
            WWW::Mechanize::Chrome->new(%default_mech_params)
        };
        die $@ if $@;
    
        # This transfers all javascript code's console.log(...)
        # messages to perl's warn()
        # we need to keep $console var in scope!
        my $console = $mech_obj->add_listener('Runtime.consoleAPICalled', sub {
              warn
                  "js console: "
                . join ", ",
                  map { $_->{value} // $_->{description} }
                  @{ $_[0]->{params}->{args} };
            })
        ;
    
        # and now fetch a page
        my $URL = '...';
        my $retmech = $mech_obj->get($URL);
        die "failed to fetch $URL" unless defined $retmech;
        $mech_obj->sleep(1); # let it settle
        # now the mech object has loaded the URL and has a DOM hopefully.
        # You can pass it on to find() or zap() to operate on the DOM.

SECURITY WARNING

    WWW::Mechanize::Chrome invokes the google-chrome executable on behalf
    of the current user. Headless or not, google-chrome is invoked.
    Depending on the launch parameters, either a fresh, new browser session
    will be created or the session of the current user with their profile,
    data, cookies, passwords, history, etc. will be used. The latter case
    is very dangerous.

    This behaviour is controlled by WWW::Mechanize::Chrome's constructor
    parameters which, in turn, are used for launching the google-chrome
    executable. Specifically, see WWW::Mechanize::Chrome#separate_session,
    <WWW::Mechanize::Chrome#data_directory and
    WWW::Mechanize::Chrome#incognito.

    Unless you really need to mechsurf with your current session, aim to
    launching the browser with a fresh new session. This is the safest
    option.

    Do not rely on default behaviour as this may change over time. Be
    explicit.

    Also, be warned that WWW::Mechanize::Chrome::DOMops executes javascript
    code on that google-chrome instance. This is done nternally with
    javascript code hardcoded into the WWW::Mechanize::Chrome::DOMops's
    package files.

    On top of that WWW::Mechanize::Chrome::DOMops allows for user-specified
    javascript code to be executed on that google-chrome instance. For
    example the callbacks on each element found, etc.

    This is an example of what can go wrong if you are not using a fresh
    google-chrome session:

    You have just used google-chrome to access your yahoo webmail and you
    did not logout. So, there will be an access cookie in the google-chrome
    when you later invoke it via WWW::Mechanize::Chrome (remember you have
    not told it to use a fresh session).

    If you allow unchecked user-specified (or copy-pasted from ChatGPT)
    javascript code in WWW::Mechanize::Chrome::DOMops's find(), zap(), etc.
    then it is, theoretically, possible that this javascript code initiates
    an XHR to yahoo and fetch your emails and pass them on to your perl
    code.

    But there is another problem, WWW::Mechanize::Chrome::DOMops's
    integrity of the embedded javascript code may have been compromised to
    exploit your current session.

    This is very likely with a Windows installation which, being the
    security swiss cheese it is, it is possible for anyone to compromise
    your module's code. It is less likely in Linux, if your modules are
    installed by root and are read-only for normal users. But, still, it is
    possible to be compromised (by root).

    Another issue is with the saved passwords and the browser's auto-fill
    when landing on a login form.

    Therefore, for all these reasons, it is advised not to invoke (via
    WWW::Mechanize::Chrome) google-chrome with your
    current/usual/everyday/email-access/bank-access identity so that it
    does not have access to your cookies, passwords, history etc.

    It is better to create a fresh google-chrome identity/profile and use
    that for your WWW::Mechanize::Chrome::DOMops needs.

    No matter what identity you use, you may want to erase the cookies and
    history of google-chrome upon its exit. That's a good practice.

    It is also advised to review the javascript code you provide via
    WWW::Mechanize::Chrome::DOMops callbacks if it is taken from 3rd-party,
    human or not, e.g. ChatGPT.

    Additionally, make sure that the current installation of
    WWW::Mechanize::Chrome::DOMops in your system is not compromised with
    malicious javascript code injected into it. For this you can check its
    MD5 hash.

DEPENDENCIES

    This module depends on WWW::Mechanize::Chrome which, in turn, depends
    on the google-chrome executable be installed on the host computer. See
    WWW::Mechanize::Chrome::Install on how to install the executable.

    Test scripts (which create there own mech object) will detect the
    absence of google-chrome binary and exit gracefully, meaning the test
    passes. But with a STDERR message to the user. Who will hopefully
    notice it and proceed to google-chrome installation. In any event, this
    module will be installed with or without google-chrome.

AUTHOR

    Andreas Hadjiprocopis, <bliako at cpan.org>

CODING CONDITIONS

    This code was written under extreme climate conditions of 44 Celsius.
    Keep packaging those vegs in kilos of plastic wrappers, keep
    obsolidating our perfectly good hardware, keep inventing new consumer
    needs and brainwash them down our throats, in short Crack Deep the Roof
    Beam, Capitalism.

BUGS

    Please report any bugs or feature requests to
    bug-www-mechanize-chrome-domops at rt.cpan.org, or through the web
    interface at
    https://rt.cpan.org/NoAuth/ReportBug.html?Queue=WWW-Mechanize-Chrome-DOMops.
    I will be notified, and then you'll automatically be notified of
    progress on your bug as I make changes.

SUPPORT

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

        perldoc WWW::Mechanize::Chrome::DOMops

    You can also look for information at:

      * RT: CPAN's request tracker (report bugs here)

      https://rt.cpan.org/NoAuth/Bugs.html?Dist=WWW-Mechanize-Chrome-DOMops

      * AnnoCPAN: Annotated CPAN documentation

      http://annocpan.org/dist/WWW-Mechanize-Chrome-DOMops

      * CPAN Ratings

      https://cpanratings.perl.org/d/WWW-Mechanize-Chrome-DOMops

      * Search CPAN

      https://metacpan.org/release/WWW-Mechanize-Chrome-DOMops

DEDICATIONS

    Almaz

ACKNOWLEDGEMENTS

    CORION for publishing WWW::Mechanize::Chrome and all its contributors.

LICENSE AND COPYRIGHT

    Copyright 2019 Andreas Hadjiprocopis.

    This program is free software; you can redistribute it and/or modify it
    under the terms of the the Artistic License (2.0). You may obtain a
    copy of the full license at:

    http://www.perlfoundation.org/artistic_license_2_0

    Any use, modification, and distribution of the Standard or Modified
    Versions is governed by this Artistic License. By using, modifying or
    distributing the Package, you accept this license. Do not use, modify,
    or distribute the Package, if you do not accept this license.

    If your Modified Version has been derived from a Modified Version made
    by someone other than you, you are nevertheless required to ensure that
    your Modified Version complies with the requirements of this license.

    This license does not grant you the right to use any trademark, service
    mark, tradename, or logo of the Copyright Holder.

    This license includes the non-exclusive, worldwide, free-of-charge
    patent license to make, have made, use, offer to sell, sell, import and
    otherwise transfer the Package with respect to any patent claims
    licensable by the Copyright Holder that are necessarily infringed by
    the Package. If you institute patent litigation (including a
    cross-claim or counterclaim) against any party alleging that the
    Package constitutes direct or contributory patent infringement, then
    this Artistic License to you shall terminate on the date that such
    litigation is filed.

    Disclaimer of Warranty: THE PACKAGE IS PROVIDED BY THE COPYRIGHT HOLDER
    AND CONTRIBUTORS "AS IS' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES.
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