<?php

/**
 *  Implementation of hook_permission().
 *
 *  Adds a permission to merge terms.
 */
function term_merge_permission() {
  return array(
    'merge terms' => array(
      'title' => t('Merge terms'),
      'description' => t('Gives the user the ability to merge terms.'),
    )
  );
}

/**
 *  Implements hook_menu():
 */
function term_merge_menu() {
  $items = array(
    'admin/structure/taxonomy/%taxonomy_vocabulary_machine_name/merge' => array(
      'title' => 'Merge terms',
      'page callback' => 'drupal_get_form',
      'page arguments' => array('term_merge_term_merge_form', 3),
      'access arguments' => array('merge terms'),
      'type' => MENU_LOCAL_TASK,
    )
  );
  return $items;
}

/**
 *  Implements hook_help().
 */
function term_merge_help($path, $arg) {
  switch ($path) {
    // Main module help for the block module
    case 'admin/help#term_merge':
      return '<p>Allows you to merge multiple terms into one and and at the same time update all fields referencing to the old ones.</p>';


    /*case 'admin/structure/taxonomy/%/merge':
      return '<p>This form simply lets you merge multiple terms into one and at the same time update all fields referencing to the old ones.</p>';*/
  }
}

/**
 *  Implements hook_form_FORM_ID_alter().
 *
 *  Inserts the Merge button into the actions of the form.
 */
function term_merge_form_taxonomy_overview_terms_alter(&$form, &$form_state, $form_id) {
  if ($form['#total_entries'] > 0) {
    $form['actions'][] = array(
      'merge' => array(
        '#type' => 'submit',
        '#value' => t('Merge'),
        '#submit' => array('term_merge_form_taxonomy_overview_terms_merge_submit'),
        '#weight' => 1,
      )
    );

    $form['actions']['submit']['#weight'] = 0;
    $form['actions']['reset_alphabetical']['#weight'] = 2;
  }
}

/**
 *  Submit function for the merge button in the alteration of form form_taxonomy_overview_terms (see above).
 *  Redirects the user to the term merge form/page.
 */
function term_merge_form_taxonomy_overview_terms_merge_submit($form, &$form_state) {
  unset($form_state['storage']);
  $form_state['redirect'] = 'admin/structure/taxonomy/' . $form['#vocabulary']->machine_name . '/merge';
}

/**
 *  Implements hook_form().
 *
 *  Menu callback; displays components to let user select one or more terms for merging and
 *  let them be merged into another, specified term.
 */
function term_merge_term_merge_form($form, $form_state, $vocabulary) {

  if (!isset($form_state['storage']['term_list'])) { // Create th merge form.

    $form = array(
      'term_list' => array(
        '#type' => 'select',
        '#title' => t('Merge terms'),
        '#options' => _term_delete_form_replacement_term_options($vocabulary->vid, 0, FALSE),
        '#multiple' => TRUE,
        '#required' => TRUE,
        '#attributes' => array('size' => 15),
        '#prefix' => '<div class="merge-container clearfix"><div class="terms-selector">',
      ),

      'replacement_term' => array(
        '#type' => 'select',
        '#title' => t('Into'),
        '#description' => t('Cannot be any of the terms selected in the list to the left.'),
        '#options' => _term_delete_form_replacement_term_options($vocabulary->vid, 0, TRUE),
        '#prefix' => '</div><div class="merge-selectors">',
      ),

      'replacement_term_new' => array(
        '#type' => 'textfield',
        '#title' => t('Name of new term'),
        '#description' => t('A new term will be created with the specified name.'),
        '#suffix' => '</div>',
      ),

      'keep_merged' => array(
        '#type' => 'checkbox',
        '#title' => t('Only merge occurrences'),
        '#description' => t('Check this if you only want to merge occurrences of the merged terms leaving them as they are in the vocabulary.'),
        '#prefix' => '</div>',
      ),

      '#vocabulary' => $vocabulary,

      'merge_redirect_path' => array(
        '#type' => 'value',
        '#value' => 'admin/structure/taxonomy/' . $vocabulary->machine_name,
      ),
    );

    // Adds the .js and .css used by form.
    $form['#after_build'] = array('_term_merge_form_attach');
  }
  else {  // Let the user confirm the deletion.
    $form = array(
      'confirm_markup' => array(
        '#markup' => _term_merge_get_confirm_merge_markup($form_state),
        '#prefix' => '<div>',
        '#suffix' => '</div>',
      )
    );
  }

  $form['actions'] = array (
    'submit' => array(
      '#type' => 'submit',
      '#value' => t('Merge'),
    ),
    'cancel' => array(
      '#type' => 'link',
      '#title' => t('Cancel'),
      '#href' => 'admin/structure/taxonomy/' . $vocabulary->machine_name,
    )
  );

  return $form;
}

/**
 *  Validation handler for term_merge_term_merge_form().
 */
function term_merge_term_merge_form_validate($form, &$form_state) {
  $form_values = $form_state['values'];

  if (!isset($form_state['storage']['term_list'])) {
    // Convert the array of terms to merge into a normally keyed array.
    $form_values['term_list'] = array_values($form_values['term_list']);

    if ($form_values['replacement_term'] == '0' &&
        empty($form_values['replacement_term_new'])) {

      form_set_error('replacement_term_new', t('You must enter a name for the new term.'));
    }
    elseif ($pos = array_search($form_values['replacement_term'], $form_values['term_list'])) {
      array_splice($form_values['term_list'], $pos, 1);
    }
  }

}

/**
 *  Submit handler for term_merge_term_merge_form().
 *
 *  Collects data about what terms to merge into what term and sends it to term_merge().
 */
function term_merge_term_merge_form_submit($form, &$form_state) {

  if (!isset($form_state['storage']['term_list'])) {  // Store values and rebuild form for merge confirmation.
    $form_values = $form_state['values'];

    $form_state['storage']['term_list'] = $form_values['term_list'];
    $form_state['storage']['replacement_term'] = $form_values['replacement_term'];
    $form_state['storage']['replacement_term_new'] = $form_values['replacement_term_new'];
    $form_state['storage']['merge_redirect_path'] = $form_values['merge_redirect_path'];
    $form_state['storage']['keep_merged'] = $form_values['keep_merged'];
    $form_state['storage']['working_vocabulary'] = $form['#vocabulary'];

    $form_state['rebuild'] = TRUE;
  }
  else {  // Merge confirmed, do it!
    $replacement_term = $form_state['storage']['replacement_term'];
    $merged_terms = $form_state['storage']['term_list'];
    $replacement_term_new = $form_state['storage']['replacement_term_new'];

    // Create a new tid id the value of $replacement_term is equal to 0.
    if ($replacement_term == '0') {
      $new_term = _term_merge_term_create($replacement_term_new, $form_state['storage']['working_vocabulary'], $merged_terms);
      $dest_tid = $new_term->tid;
    }
    else {  // Else, the value of $replacement_term contains the tid of the new term.
      $dest_tid = $replacement_term;
    }

     // Redirect user after merge.
    $form_state['redirect'] = $form_state['storage']['merge_redirect_path'];

    // Now merge.
    term_merge($merged_terms, $dest_tid, $form_state['storage']['keep_merged']);
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 *
 * Add fields to allow term merging on the confirm deletion state of the form_taxonomy_form_term form.
 */
function term_merge_form_taxonomy_form_term_alter(&$form, &$form_state, $form_id) {
  // Only modify the form if it is in the "Confirm Delete" states.
  if (isset($form_state['confirm_delete']) && $form_state['confirm_delete'] === TRUE && user_access('term merge')) {

    $form['description']['#markup'] .= '<br /><br />' . t('You can replace any occurrences of the deleted term with another term by specifying the replacement below. This is useful when correcting typos, or to consolidate multiple, synonymous terms.') . '<br /><br />';

    $form['replacement_term_replace'] = array(
      '#type' => 'checkbox',
      '#title' => t('Replace deleted term with:'),
      '#prefix' => '<div>',
    );

    $form['replacement_term'] = array(
      '#type' => 'select',
      '#options' => _term_delete_form_replacement_term_options($form['#vocabulary']->vid, $form['#term']->tid, TRUE),
      '#suffix' => '</div>',
    );

    $form['replacement_term_new'] = array(
      '#type' => 'textfield',
      '#title' => t('Name of new term'),
    );

    $form['#after_build'] = array('_term_merge_form_attach');

    $form['#submit'] = array('term_merge_form_taxonomy_form_term_submit');
    $form['#validate'] = array('term_merge_form_taxonomy_form_term_validate');
  }
}

/**
 * Validation function for override of form_taxonomy_form_term (see above).
 *
 * If the user want's to create a new term, check to see if he has entered a name for it.
 */
function term_merge_form_taxonomy_form_term_validate($form, &$form_state) {
  $form_values = $form_state['values'];

  if ($form_values['replacement_term'] == '0' &&
      empty($form_state['values']['replacement_term_new'])) {

    form_set_error('replacement_term_new', t('You must enter a name for the new term.'));
  }
}

/**
 * Submit function for alteration of form_taxonomy_form_term (see above).
 *
 * If the user choose to create a new term for merging, create and save a term with the entered name.
 * Call the merge function to merge the replacement term into the deleted term.
 */
function term_merge_form_taxonomy_form_term_submit($form, &$form_state) {
  if ($form_state['values']['replacement_term_replace']) {

    $replacement_term = $form_state['values']['replacement_term'];
    /// Create a new tid id the value of $replacement_term is equal to 0.
    if ($replacement_term == '0') {
      $new_term = _term_merge_term_create(check_plain($form_state['values']['replacement_term_new']), $form['#vocabulary'], $form['#term']->tid);
      $dest_tid = $new_term->tid;
    }
    else {  // Else, the value of $replacement_term contains the tid of the new term.
      $dest_tid = $replacement_term;
    }

    // Merge.
    term_merge($form['#term']->tid, $dest_tid, TRUE);
  }
  else {
    // Continue as the confirm deletion form would normally.
    taxonomy_term_confirm_delete_submit($form, $form_state);
  }
}


/**
 *  Merge source terms into one destination term.
 * @param $source
 *    A single term tid or an array of term tids to be merged.
 * @param $dest
 *    The tid of the term to merge sources into.
 */
function term_merge($source, $dest, $keep_merged) {
  // Create an array of source if it isn't already one.
  if (!is_array($source)) {
    $source = array($source);
  }
  $source = array_values($source);

  // Create a skeleton for the merging batch.
  $update_batch = array(
    'title' => t('Merging terms'),
    'operations' => array(
      array('_term_merge_batch_store_merged_terms', array(
        $keep_merged ? array() : $source,
        count($source),
      ))
    ),
    'finished' => '_term_merge_finished',
  );

  // For every field existing on the site.
  foreach (field_info_fields() as $key => $field) {

    if ($field['type'] == 'taxonomy_term_reference') {
      $table_name = 'field_data_' . $key;
      $tid_field = $key . '_tid';

      $update_data = array();
      foreach ($source as $source_tid) {

        // Get data from fields previously containing a reference to the merged term.
        $fields_result = db_select($table_name, 'df')
          ->fields('df', array('entity_type', 'entity_id', 'delta'))
          ->condition($tid_field, $source_tid)
          ->execute();

        // Collect update data form the batch process and group them by their entity.
        foreach ($fields_result as $field_row) {
          $batch_key = $field_row->entity_type . '_' . $field_row->entity_id;
          $update_data[$batch_key][] = array(
            'field_name' => $key,
            'source_tid' => $source_tid,
            'dest_tid' => $dest,
          );
        }
      }

      // Create a batch processing step for every entity that needs an update.
      foreach ($update_data as $key => $batch_data) {
        $delimiter_pos = strripos($key, '_');
        $type = drupal_substr($key, 0, $delimiter_pos);
        $id = drupal_substr($key, $delimiter_pos + 1);

        $batch_data = array(
          'entity_type' => $type,
          'entity_id' => $id,
          'data' => $batch_data
        );
        $update_batch['operations'][] = array(
          '_term_merge_insert_field_values',
          array($batch_data)
        );
      }
    }
  }

  // Initialize the batch process.
  batch_set($update_batch);
}

/**
 *  Creates a new term with the specified name. The new term will have the same
 *  parent as the merged terms as long as long as they all a common parent.
 */
function _term_merge_term_create($name, $vocabulary, $merged_terms) {
  $new_term = new stdClass();

  if (!is_array($merged_terms)) {
    $merged_terms = array(0 => $merged_terms);
  }

  // Get parent of merged terms.
  $merged_parent_query = db_select('taxonomy_term_hierarchy', 'tth')
    ->fields('tth', array('parent'));
  $conditions = db_or();
  foreach ($merged_terms as $merged_tid) {
    $conditions->condition('tid', $merged_tid);
  }
  $merged_parent_result = $merged_parent_query->condition($conditions)
    ->execute()->fetchCol();

  if (count($parent = array_unique($merged_parent_result)) == 1) {
    $parent_tid = $parent[0];
  }
  else {
    $parent_tid = 0;
  }

  $term = new stdClass();
  $term->name = $name;
  $term->vid = $vocabulary->vid;
  $term->parent = $parent_tid;
  $term->vocabulary_machine_name = $vocabulary->machine_name;
  $term->description = '';

  taxonomy_term_save((object) $term);
  return $term;
}

/**
 *  Stores the merged terms in the context of the batch operation,
 *  I need them in the finish function of the batch operation.
 */
function _term_merge_batch_store_merged_terms($merged_terms_delete, $num_merged_terms, &$context) {
  $context['results']['merged_terms_delete'] = $merged_terms_delete;
  $context['results']['num_merged_terms'] = $num_merged_terms;
}

/**
 *  Batch operation for adding field values into entities.
 *
 *  Loads the entity specified in $update_data and add the term reference
 *  to all fields specified in $update_data['data'].
 */
function _term_merge_insert_field_values($update_data, &$context) {
  // Extract entity information.
  $entity_type = $update_data['entity_type'];
  $entity_id = $update_data['entity_id'];

  // Load the entity.
  $entity = entity_load($entity_type, array($entity_id));
  $entity = $entity[$entity_id];

  $context['message'] = 'Merging terms in fields of ' . $entity_type . ' ' . $entity->title . '.';

  $target_merged = FALSE;
  foreach ($update_data['data'] as $i => &$update_data_arr) {
    $update_data_arr = array_reverse($update_data_arr);
		
    $field_lang = field_language('node', $entity, $update_data_arr['field_name']);
    $field_values = &$entity->{$update_data_arr['field_name']}[$field_lang];
    foreach ($field_values as $i => $value) {
      if ($value['tid'] == $update_data_arr['source_tid']) {

        if (!$target_merged) {
          $field_values[$i]['tid'] = $update_data_arr['dest_tid']->tid;
          $target_merged = TRUE;
        }
        // Any more occurrences of the source tid will simply be removed.
        // We don't want duplicates.
        else {
          array_splice($field_values, $i, 1);
        }

        // If target tid is one of the source tids, remove it from the array
        // of terms that will be removed at the end of the process.
        if($update_data_arr['source_tid']== $update_data_arr['dest_tid']->tid) {
          foreach ($context['results']['merged_terms_delete'] as $i => $merged_term) {
            if ($merged_term == $update_data_arr['source_tid']) {
              array_splice($context['results']['merged_terms_delete'], $i, 1);
            }
          }
        }

        $context['results'][] = 'Merged ' . $update_data_arr['source_tid'] . ' with '
        . $update_data_arr['dest_tid']->tid . ' in ' . $update_data_arr['field_name']
        . ' of ' . $entity_type . ' ' . $entity_id;

        break;
      }
    }
  }

  if (empty($context['sandbox'])) {
    $context['sandbox']['progress'] = 0;
  }

  $context['sandbox']['progress']++;
  $context['finished'] = $context['sandbox']['progress']/$context['results']['num_merged_terms'];

  // Save the new field values if something has changed.
  if ($target_merged) {
    field_attach_update($entity_type, $entity);
  }
}

/**
 *  The merge batch operation was finished.
 */
function _term_merge_finished($success, $results, $operations) {
  if ($success) {
    $message = format_plural($results['num_merged_terms'], 'One term merged.', '@count terms merged.');
    $message .= '<br />';
    $message .= format_plural(count($results) - 2, 'One term occurrence merged.', '@count term occurrences merged.');
    if (count($results['merged_terms_delete']) > 0) {
      $message .= '<br />';
      $message .= format_plural(count($results['merged_terms_delete']), 'One term deleted', '@count terms deleted.');
    }
  }
  else {
    $message = t('Finished with an error.');
  }
  drupal_set_message($message);

  // Delete merged terms on success. We don't want to do this earlier if something went wrong during the batch process.
  if ($success) {
    foreach ($results['merged_terms_delete'] as $merged_term) {
      taxonomy_term_delete($merged_term);
    }
  }
}

/**
 * Returns the markup text for the confirmation message of term merging.
 */
function _term_merge_get_confirm_merge_markup($form_state) {
  $form_values = $form_state['values'];

  $terms = taxonomy_term_load_multiple($form_values['term_list']);
  $dest_term_name = ($dest_term = taxonomy_term_load($form_values['replacement_term'])) ?
    $dest_term->name : $form_values['replacement_term_new'];


  $merged_names = '';
  foreach (array_values($terms) as $i => $term) {
    $merged_names .= $term->name;
    if ($i < count($terms) - 2) {
      $merged_names .= ', ';
    }
    else if ($i == count($terms) - 2) {
      $merged_names .= ' & ';
    }
  }

  $output = 'Are you sure you want to merge <b>%term_names</b> with <b>%destination_term</b>'
    . (($form_state['storage']['replacement_term_new']) ? ' (new)' : '')
    . ' ? ';

  if ($form_values['keep_merged']) {
    $output .= 'Due to your choice, the merged terms will not be deleted from their vocabulary.<br />&nbsp;';
  }
  else {
    $output .= '<br /><u>All merged terms will be deleted</u>!<br />&nbsp;';
  }

  $output = t($output, array('%term_names' => $merged_names, '%destination_term' => $dest_term_name));
  return $output;
}

/**
 *  Returns values for the replacement_term select box in the form (see form builder at top).
 *  Don't return the value for the term that will be merged.
 */
function _term_delete_form_replacement_term_options($vid, $merged_term_tid, $add_new_option) {
  $tree = taxonomy_get_tree($vid);
  foreach ($tree as $i => $term) {
    if ($merged_term_tid != $term->tid) {
      $options[$term->tid] = $term->name;
    }
  }

  if ($add_new_option) {
    $options['0'] = t('New term, specified below');
  }

  return $options;
}


/**
 *  Add necessary JavaScript and css to the form.
 */
function _term_merge_form_attach($form_element) {
  if ($form_element['#id'] == 'term-merge-term-merge-form') {
    drupal_add_js(drupal_get_path('module', 'term_merge') . '/term_merge.js');
  }
  elseif ($form_element['#id'] == 'taxonomy-form-term') {
    drupal_add_js(drupal_get_path('module', 'term_merge') . '/term_merge_deletion.js');
  }

  drupal_add_css(drupal_get_path('module', 'term_merge') . '/term_merge.css');

  return $form_element;
}