<?php

/**
 * @file
 * Definition of views_handler_filter_fields_compare.
 */

/**
 * A handler to filter a view using fields comparison.
 *
 * @ingroup views_filter_handlers
 */
class views_handler_filter_fields_compare extends views_handler_filter {

  /**
   * {@inheritdoc}
   */
  public function can_expose() {
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function option_definition() {
    $options = parent::option_definition();

    $options['left_field'] = $options['right_field'] = array('default' => '');

    return $options;
  }

  /**
   * Provide a list of all operators.
   */
  public function fields_operator_options() {
    return array(
      '<' => t('Is less than'),
      '<=' => t('Is less than or equal to'),
      '=' => t('Is equal to'),
      '<>' => t('Is not equal to'),
      '>=' => t('Is greater than or equal to'),
      '>' => t('Is greater than'),
    );
  }

  /**
   * Provide a list of available fields.
   */
  public function field_options() {
    $options = array();

    $field_handlers = $this->view->display_handler->get_handlers('field');
    foreach ($field_handlers as $field => $handler) {
      if ($handler->table != 'views') {
        $options[$field] = $handler->ui_name();
      }
    }

    return $options;
  }

  /**
   * {@inheritdoc}
   */
  public function options_form(&$form, &$form_state) {
    parent::options_form($form, $form_state);

    $field_options = $this->field_options();

    $form['left_field'] = array(
      '#type' => 'select',
      '#title' => t('Left field'),
      '#default_value' => $this->options['left_field'],
      '#options' => $field_options,
      '#weight' => -3,
    );

    $form['operator'] = array(
      '#type' => 'select',
      '#title' => t('Operator'),
      '#default_value' => $this->options['operator'],
      '#options' => $this->fields_operator_options(),
      '#weight' => -2,
    );

    $form['right_field'] = array(
      '#type' => 'select',
      '#title' => t('Right field'),
      '#default_value' => $this->options['right_field'],
      '#options' => $field_options,
      '#weight' => -1,
    );

  }

  /**
   * {@inheritdoc}
   */
  public function query() {
    // Build extra condition from existing fields (from existing joins).
    $left = $this->options['left_field'];
    $right = $this->options['right_field'];

    // Get all existing field handlers.
    $field_handlers = $this->view->display_handler->get_handlers('field');

    // Make sure the selected fields still exist.
    if (!isset($field_handlers[$left], $field_handlers[$right])) {
      return;
    }

    // Get the left table and field.
    $left_handler = $field_handlers[$left];
    $left_handler->set_relationship();
    $left_table_alias = $this->query->ensure_table($left_handler->table, $left_handler->relationship);

    // Get the left table and field.
    $right_handler = $field_handlers[$right];
    $right_handler->set_relationship();
    $right_table_alias = $this->query->ensure_table($right_handler->table, $right_handler->relationship);

    // Build piece of SQL.
    $snippet = $left_table_alias . '.' . $left_handler->real_field
      . ' ' . $this->options['operator'] . ' '
      . $right_table_alias . '.' . $right_handler->real_field;

    $this->query->add_where_expression($this->options['group'], $snippet);
  }

  /**
   * {@inheritdoc}
   */
  public function admin_summary() {
    return check_plain(
      $this->options['left_field'] . ' '
      . $this->options['operator'] . ' '
      . $this->options['right_field']
    );
  }

}