class StringFilter

class StringFilter extends FilterPluginBase implements FilterOperatorsInterface {
    
    /**
     * All words separated by spaces or sentences encapsulated by double quotes.
     */
    const WORDS_PATTERN = '/ (-?)("[^"]+"|[^" ]+)/i';
    
    /**
     * Exposed filter options.
     *
     * @var bool
     */
    protected $alwaysMultiple = TRUE;
    
    /**
     * The database connection.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $connection;
    
    /**
     * Constructs a new StringFilter object.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin_id for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\Core\Database\Connection $connection
     *   The database connection.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, Connection $connection) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->connection = $connection;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('database'));
    }
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['expose']['contains']['required'] = [
            'default' => FALSE,
        ];
        $options['expose']['contains']['placeholder'] = [
            'default' => '',
        ];
        return $options;
    }
    
    /**
     * {@inheritdoc}
     */
    public function defaultExposeOptions() {
        parent::defaultExposeOptions();
        $this->options['expose']['placeholder'] = NULL;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildExposeForm(&$form, FormStateInterface $form_state) {
        parent::buildExposeForm($form, $form_state);
        $form['expose']['placeholder'] = [
            '#type' => 'textfield',
            '#default_value' => $this->options['expose']['placeholder'],
            '#title' => $this->t('Placeholder'),
            '#size' => 40,
            '#description' => $this->t('Hint text that appears inside the field when empty.'),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function operators() {
        $operators = [
            '=' => [
                'title' => $this->t('Is equal to'),
                'short' => $this->t('='),
                'method' => 'opEqual',
                'values' => 1,
            ],
            '!=' => [
                'title' => $this->t('Is not equal to'),
                'short' => $this->t('!='),
                'method' => 'opEqual',
                'values' => 1,
            ],
            'contains' => [
                'title' => $this->t('Contains'),
                'short' => $this->t('contains'),
                'method' => 'opContains',
                'values' => 1,
            ],
            'word' => [
                'title' => $this->t('Contains any word'),
                'short' => $this->t('has word'),
                'method' => 'opContainsWord',
                'values' => 1,
            ],
            'allwords' => [
                'title' => $this->t('Contains all words'),
                'short' => $this->t('has all'),
                'method' => 'opContainsWord',
                'values' => 1,
            ],
            'starts' => [
                'title' => $this->t('Starts with'),
                'short' => $this->t('begins'),
                'method' => 'opStartsWith',
                'values' => 1,
            ],
            'not_starts' => [
                'title' => $this->t('Does not start with'),
                'short' => $this->t('not_begins'),
                'method' => 'opNotStartsWith',
                'values' => 1,
            ],
            'ends' => [
                'title' => $this->t('Ends with'),
                'short' => $this->t('ends'),
                'method' => 'opEndsWith',
                'values' => 1,
            ],
            'not_ends' => [
                'title' => $this->t('Does not end with'),
                'short' => $this->t('not_ends'),
                'method' => 'opNotEndsWith',
                'values' => 1,
            ],
            'not' => [
                'title' => $this->t('Does not contain'),
                'short' => $this->t('!has'),
                'method' => 'opNotLike',
                'values' => 1,
            ],
            'shorterthan' => [
                'title' => $this->t('Length is shorter than'),
                'short' => $this->t('shorter than'),
                'method' => 'opShorterThan',
                'values' => 1,
            ],
            'longerthan' => [
                'title' => $this->t('Length is longer than'),
                'short' => $this->t('longer than'),
                'method' => 'opLongerThan',
                'values' => 1,
            ],
            'regular_expression' => [
                'title' => $this->t('Regular expression'),
                'short' => $this->t('regex'),
                'method' => 'opRegex',
                'values' => 1,
            ],
            'not_regular_expression' => [
                'title' => $this->t('Negated regular expression'),
                'short' => $this->t('not regex'),
                'method' => 'opNotRegex',
                'values' => 1,
            ],
        ];
        // if the definition allows for the empty operator, add it.
        if (!empty($this->definition['allow empty'])) {
            $operators += [
                'empty' => [
                    'title' => $this->t('Is empty (NULL)'),
                    'method' => 'opEmpty',
                    'short' => $this->t('empty'),
                    'values' => 0,
                ],
                'not empty' => [
                    'title' => $this->t('Is not empty (NOT NULL)'),
                    'method' => 'opEmpty',
                    'short' => $this->t('not empty'),
                    'values' => 0,
                ],
            ];
        }
        return $operators;
    }
    
    /**
     * Build strings from the operators() for 'select' options.
     */
    public function operatorOptions($which = 'title') {
        $options = [];
        foreach ($this->operators() as $id => $info) {
            $options[$id] = $info[$which];
        }
        return $options;
    }
    public function adminSummary() {
        if ($this->isAGroup()) {
            return $this->t('grouped');
        }
        if (!empty($this->options['exposed'])) {
            return $this->t('exposed');
        }
        $options = $this->operatorOptions('short');
        $output = '';
        if (!empty($options[$this->operator])) {
            $output = $options[$this->operator];
        }
        if (in_array($this->operator, $this->operatorValues(1))) {
            $output .= ' ' . $this->value;
        }
        return $output;
    }
    protected function operatorValues($values = 1) {
        $options = [];
        foreach ($this->operators() as $id => $info) {
            if (isset($info['values']) && $info['values'] == $values) {
                $options[] = $id;
            }
        }
        return $options;
    }
    
    /**
     * Provide a simple textfield for equality.
     */
    protected function valueForm(&$form, FormStateInterface $form_state) {
        // We have to make some choices when creating this as an exposed
        // filter form. For example, if the operator is locked and thus
        // not rendered, we can't render dependencies; instead we only
        // render the form items we need.
        $which = 'all';
        if (!empty($form['operator'])) {
            $source = ':input[name="options[operator]"]';
        }
        if ($exposed = $form_state->get('exposed')) {
            $identifier = $this->options['expose']['identifier'];
            if (empty($this->options['expose']['use_operator']) || empty($this->options['expose']['operator_id'])) {
                // exposed and locked.
                $which = in_array($this->operator, $this->operatorValues(1)) ? 'value' : 'none';
            }
            else {
                $source = ':input[name="' . $this->options['expose']['operator_id'] . '"]';
            }
        }
        if ($which == 'all' || $which == 'value') {
            $form['value'] = [
                '#type' => 'textfield',
                '#title' => $this->t('Value'),
                '#size' => 30,
                '#default_value' => $this->value,
            ];
            if (!empty($this->options['expose']['placeholder'])) {
                $form['value']['#attributes']['placeholder'] = $this->options['expose']['placeholder'];
            }
            $user_input = $form_state->getUserInput();
            if ($exposed && !isset($user_input[$identifier])) {
                $user_input[$identifier] = $this->value;
                $form_state->setUserInput($user_input);
            }
            if ($which == 'all') {
                // Setup #states for all operators with one value.
                foreach ($this->operatorValues(1) as $operator) {
                    $form['value']['#states']['visible'][] = [
                        $source => [
                            'value' => $operator,
                        ],
                    ];
                }
            }
        }
        if (!isset($form['value'])) {
            // Ensure there is something in the 'value'.
            $form['value'] = [
                '#type' => 'value',
                '#value' => NULL,
            ];
        }
    }
    
    /**
     * Get the query operator.
     *
     * @return string
     *   Returns LIKE or NOT LIKE or the database specific equivalent based on the
     *   query's operator.
     */
    public function operator() {
        return $this->getConditionOperator($this->operator == '=' ? 'LIKE' : 'NOT LIKE');
    }
    
    /**
     * Get specified condition operator mapping value.
     *
     * @param string $operator
     *   Condition operator.
     *
     * @return string
     *   Specified condition operator mapping value.
     */
    protected function getConditionOperator($operator) {
        $mapping = $this->connection
            ->mapConditionOperator($operator);
        return $mapping['operator'] ?? $operator;
    }
    
    /**
     * Add this filter to the query.
     *
     * Due to the nature of fapi, the value and the operator have an unintended
     * level of indirection. You will find them in $this->operator
     * and $this->value respectively.
     */
    public function query() {
        $this->ensureMyTable();
        $field = "{$this->tableAlias}.{$this->realField}";
        $info = $this->operators();
        if (!empty($info[$this->operator]['method'])) {
            $this->{$info[$this->operator]['method']}($field);
        }
    }
    
    /**
     * Adds a where clause for the operation, 'equals'.
     */
    public function opEqual($field) {
        $this->query
            ->addWhere($this->options['group'], $field, $this->value, $this->operator());
    }
    protected function opContains($field) {
        $operator = $this->getConditionOperator('LIKE');
        $this->query
            ->addWhere($this->options['group'], $field, '%' . $this->connection
            ->escapeLike($this->value) . '%', $operator);
    }
    protected function opContainsWord($field) {
        $where = $this->operator == 'word' ? $this->query
            ->getConnection()
            ->condition('OR') : $this->query
            ->getConnection()
            ->condition('AND');
        // Don't filter on empty strings.
        if (empty($this->value)) {
            return;
        }
        preg_match_all(static::WORDS_PATTERN, ' ' . $this->value, $matches, PREG_SET_ORDER);
        $operator = $this->getConditionOperator('LIKE');
        foreach ($matches as $match) {
            $phrase = FALSE;
            // Strip off phrase quotes
            if ($match[2][0] == '"') {
                $match[2] = substr($match[2], 1, -1);
                $phrase = TRUE;
            }
            $words = trim($match[2], ',?!();:-');
            $words = $phrase ? [
                $words,
            ] : preg_split('/ /', $words, -1, PREG_SPLIT_NO_EMPTY);
            foreach ($words as $word) {
                $where->condition($field, '%' . $this->connection
                    ->escapeLike(trim($word, " ,!?")) . '%', $operator);
            }
        }
        if ($where->count() === 0) {
            return;
        }
        // previously this was a call_user_func_array but that's unnecessary
        // as views will unpack an array that is a single arg.
        $this->query
            ->addWhere($this->options['group'], $where);
    }
    protected function opStartsWith($field) {
        $operator = $this->getConditionOperator('LIKE');
        $this->query
            ->addWhere($this->options['group'], $field, $this->connection
            ->escapeLike($this->value) . '%', $operator);
    }
    protected function opNotStartsWith($field) {
        $operator = $this->getConditionOperator('NOT LIKE');
        $this->query
            ->addWhere($this->options['group'], $field, $this->connection
            ->escapeLike($this->value) . '%', $operator);
    }
    protected function opEndsWith($field) {
        $operator = $this->getConditionOperator('LIKE');
        $this->query
            ->addWhere($this->options['group'], $field, '%' . $this->connection
            ->escapeLike($this->value), $operator);
    }
    protected function opNotEndsWith($field) {
        $operator = $this->getConditionOperator('NOT LIKE');
        $this->query
            ->addWhere($this->options['group'], $field, '%' . $this->connection
            ->escapeLike($this->value), $operator);
    }
    protected function opNotLike($field) {
        $operator = $this->getConditionOperator('NOT LIKE');
        $this->query
            ->addWhere($this->options['group'], $field, '%' . $this->connection
            ->escapeLike($this->value) . '%', $operator);
    }
    protected function opShorterThan($field) {
        $placeholder = $this->placeholder();
        // Type cast the argument to an integer because the SQLite database driver
        // has to do some specific alterations to the query base on that data type.
        $this->query
            ->addWhereExpression($this->options['group'], "LENGTH({$field}) < {$placeholder}", [
            $placeholder => (int) $this->value,
        ]);
    }
    protected function opLongerThan($field) {
        $placeholder = $this->placeholder();
        // Type cast the argument to an integer because the SQLite database driver
        // has to do some specific alterations to the query base on that data type.
        $this->query
            ->addWhereExpression($this->options['group'], "LENGTH({$field}) > {$placeholder}", [
            $placeholder => (int) $this->value,
        ]);
    }
    
    /**
     * Filters by a regular expression.
     *
     * @param string $field
     *   The expression pointing to the queries field, for example "foo.bar".
     */
    protected function opRegex($field) {
        $this->query
            ->addWhere($this->options['group'], $field, $this->value, 'REGEXP');
    }
    
    /**
     * Filters by a negated regular expression.
     *
     * @param string $field
     *   The expression pointing to the queries field, for example "foo.bar".
     */
    protected function opNotRegex($field) {
        $this->query
            ->addWhere($this->options['group'], $field, $this->value, 'NOT REGEXP');
    }
    protected function opEmpty($field) {
        if ($this->operator == 'empty') {
            $operator = "IS NULL";
        }
        else {
            $operator = "IS NOT NULL";
        }
        $this->query
            ->addWhere($this->options['group'], $field, NULL, $operator);
    }

}