Keep track of the previous vote in the database

Attached it the patch.

Patch includes:
- Database upgrade hook
- Views integration

Minor Side-effect (with no solution):
After updating the database, all previous vote values are NULL. Its as if no one has voted twice or more before.

Looks like I added additional code to the patch. New patch removes this

With patch #18 from #1269614: Add pre-save or pre-set hook before data is store to database you can add the previous value to be evaluated by implementing hook_votingapi_preset_votes_alter().

When you pass it by reference and set the previous value, Patch #2 breaks. You cannot select the correct vote to delete from the database, as the previous value now set. Attached is a patch that fixes this.

Simple example

function mymodule_votingapi_preset_votes_alter(&$votes) {
  foreach ($votes as &$vote) {
      $tmp = $user_info;
      $tmp += $vote;
      if (isset($vote['value'])) {
        // have to unset the value to be able to select the correct record
        // in the database to delete.
        unset($tmp['value']);
      }
      $vote['previous_value'] = votingapi_select_single_vote_value($tmp);
      ...
      // do whatever you want
      ...
   }  
}

Example that I am using in Voting Rules #1880550: Need: Pre vote or Pre cast Event

/**
 * Implements hook_votingapi_preset_votes_alter().
 */
function voting_rules_votingapi_preset_votes_alter(&$votes) {
  // for pass by reference
  $objVote = new EntityMetadataArrayObject($votes);
  for ($delta = 0; $delta < $objVote->count(); $delta++) {
    // Majority of the time you will need the previous value for comparision in a
    // rule. Voteapi module does not add before this function is called.
    $vote = $objVote->offsetGet($delta);
    if (!isset($vote['previous_value'])) {
      $tmp = votingapi_current_user_identifier();
      $tmp += $vote;
      if (isset($tmp['value'])) {
        unset($tmp['value']);
      }
      $vote['previous_value'] = votingapi_select_single_vote_value($tmp);
      $objVote->offsetSet($delta, $vote);
    }
  }
  ...
  // additional code
  ...
}

@melissavdh I have created the identical patch already in the Voting Rules issue queue. I should have referenced it before. #1882086: Add Rule for Previous vote value

Thank you for you comment and explanation though. It does have its place here. I believe its safe to change the status to rtbc

I have rethought this. If we do an additional query in the set function, before the preset hook, and grab the "current" vote and add it to the $vote variable, then we should be good.

I will create a new issue.

FYI - The 3 patches I have for Voting Rules will have to be rewritten too.

Leaving this issue closed (won't fix).