interface ConditionInterface

interface ConditionInterface {
    
    /**
     * Helper function: builds the most common conditional clauses.
     *
     * This method takes 1 to 3 parameters.
     *
     * If called with 1 parameter, it should be a ConditionInterface that in
     * itself forms a valid where clause. Use e.g. to build clauses with nested
     * AND's and OR's.
     *
     * If called with 2 parameters, they are taken as $field and $value with
     * $operator having a value of =.
     *
     * Do not use this method to test for NULL values. Instead, use
     * QueryConditionInterface::isNull() or QueryConditionInterface::isNotNull().
     *
     * To improve readability, the operators EXISTS and NOT EXISTS have their own
     * utility method defined.
     *
     * Drupal considers LIKE case insensitive and the following is often used
     * to tell the database that case insensitive equivalence is desired:
     * @code
     * \Drupal::database()->select('users')
     *  ->condition('name', $injected_connection->escapeLike($name), 'LIKE')
     * @endcode
     * Use 'LIKE BINARY' instead of 'LIKE' for case sensitive queries.
     *
     * Note: When using MySQL, the exact behavior also depends on the used
     * collation. if the field is set to binary, then a LIKE condition will also
     * be case sensitive and when a case insensitive collation is used, the =
     * operator will also be case insensitive.
     *
     * @param string|\Drupal\Core\Database\Query\ConditionInterface $field
     *   The name of the field to check. This can also be QueryConditionInterface
     *   in itself. Use where(), if you would like to add a more complex condition
     *   involving operators or functions, or an already compiled condition.
     * @param string|array|\Drupal\Core\Database\Query\SelectInterface|null $value
     *   The value to test the field against. In most cases, and depending on the
     *   operator, this will be a scalar or an array. As SQL accepts select
     *   queries on any place where a scalar value or set is expected, $value may
     *   also be a(n array of) SelectInterface(s). If $operator is a unary
     *   operator, e.g. IS NULL, $value will be ignored and should be null. If
     *   the operator requires a subquery, e.g. EXISTS, the $field will be ignored
     *   and $value should be a SelectInterface object.
     * @param string|null $operator
     *   The operator to use. Supported for all supported databases are at least:
     *   - The comparison operators =, <>, <, <=, >, >=.
     *   - The operators (NOT) BETWEEN, (NOT) IN, (NOT) EXISTS, (NOT) LIKE.
     *   Other operators (e.g. LIKE, BINARY) may or may not work. Defaults to =.
     *
     * @return $this
     *   The called object.
     *
     * @throws \Drupal\Core\Database\InvalidQueryException
     *   If passed invalid arguments, such as an empty array as $value.
     *
     * @see \Drupal\Core\Database\Query\ConditionInterface::isNull()
     * @see \Drupal\Core\Database\Query\ConditionInterface::isNotNull()
     * @see \Drupal\Core\Database\Query\ConditionInterface::exists()
     * @see \Drupal\Core\Database\Query\ConditionInterface::notExist()
     * @see \Drupal\Core\Database\Query\ConditionInterface::where()
     */
    public function condition($field, $value = NULL, $operator = '=');
    
    /**
     * Adds an arbitrary WHERE clause to the query.
     *
     * @param string $snippet
     *   A portion of a WHERE clause as a prepared statement. It must use named
     *   placeholders, not ? placeholders. The caller is responsible for providing
     *   unique placeholders that do not interfere with the placeholders generated
     *   by this QueryConditionInterface object.
     * @param array $args
     *   An associative array of arguments keyed by the named placeholders.
     *
     * @return $this
     *   The called object.
     */
    public function where($snippet, $args = []);
    
    /**
     * Sets a condition that the specified field be NULL.
     *
     * @param string|\Drupal\Core\Database\Query\SelectInterface $field
     *   The name of the field or a subquery to check.
     *
     * @return $this
     *   The called object.
     */
    public function isNull($field);
    
    /**
     * Sets a condition that the specified field be NOT NULL.
     *
     * @param string|\Drupal\Core\Database\Query\SelectInterface $field
     *   The name of the field or a subquery to check.
     *
     * @return $this
     *   The called object.
     */
    public function isNotNull($field);
    
    /**
     * Sets a condition that the specified subquery returns values.
     *
     * @param \Drupal\Core\Database\Query\SelectInterface $select
     *   The subquery that must contain results.
     *
     * @return $this
     *   The called object.
     */
    public function exists(SelectInterface $select);
    
    /**
     * Sets a condition that the specified subquery returns no values.
     *
     * @param \Drupal\Core\Database\Query\SelectInterface $select
     *   The subquery that must not contain results.
     *
     * @return $this
     *   The called object.
     */
    public function notExists(SelectInterface $select);
    
    /**
     * Sets a condition that is always false.
     *
     * @return $this
     */
    public function alwaysFalse();
    
    /**
     * Gets the, possibly nested, list of conditions in this conditional clause.
     *
     * This method returns by reference. That allows alter hooks to access the
     * data structure directly and manipulate it before it gets compiled.
     *
     * The data structure that is returned is an indexed array of entries, where
     * each entry looks like the following:
     * @code
     * array(
     *   'field' => $field,
     *   'value' => $value,
     *   'operator' => $operator,
     * );
     * @endcode
     *
     * In the special case that $operator is NULL, the $field is taken as a raw
     * SQL snippet (possibly containing a function) and $value is an associative
     * array of placeholders for the snippet.
     *
     * There will also be a single array entry of #conjunction, which is the
     * conjunction that will be applied to the array, such as AND.
     *
     * @return array
     *   The, possibly nested, list of all conditions (by reference).
     */
    public function &conditions();
    
    /**
     * Gets a complete list of all values to insert into the prepared statement.
     *
     * @return
     *   An associative array of placeholders and values.
     */
    public function arguments();
    
    /**
     * Compiles the saved conditions for later retrieval.
     *
     * This method does not return anything, but simply prepares data to be
     * retrieved via __toString() and arguments().
     *
     * @param $connection
     *   The database connection for which to compile the conditionals.
     * @param $queryPlaceholder
     *   The query this condition belongs to. If not given, the current query is
     *   used.
     */
    public function compile(Connection $connection, PlaceholderInterface $queryPlaceholder);
    
    /**
     * Check whether a condition has been previously compiled.
     *
     * @return
     *   TRUE if the condition has been previously compiled.
     */
    public function compiled();
    
    /**
     * Creates an object holding a group of conditions.
     *
     * See andConditionGroup() and orConditionGroup() for more.
     *
     * @param $conjunction
     *   - AND (default): this is the equivalent of andConditionGroup().
     *   - OR: this is the equivalent of orConditionGroup().
     *
     * @return \Drupal\Core\Database\Query\ConditionInterface
     *   An object holding a group of conditions.
     */
    public function conditionGroupFactory($conjunction = 'AND');
    
    /**
     * Creates a new group of conditions ANDed together.
     *
     * @return \Drupal\Core\Database\Query\ConditionInterface
     */
    public function andConditionGroup();
    
    /**
     * Creates a new group of conditions ORed together.
     *
     * @return \Drupal\Core\Database\Query\ConditionInterface
     */
    public function orConditionGroup();

}