trait InsertTrait

trait InsertTrait {
    
    /**
     * The table on which to insert.
     *
     * @var string
     */
    protected $table;
    
    /**
     * An array of fields on which to insert.
     *
     * @var array
     */
    protected $insertFields = [];
    
    /**
     * An array of fields that should be set to their database-defined defaults.
     *
     * @var array
     */
    protected $defaultFields = [];
    
    /**
     * A nested array of values to insert.
     *
     * $insertValues is an array of arrays. Each sub-array is either an
     * associative array whose keys are field names and whose values are field
     * values to insert, or a non-associative array of values in the same order
     * as $insertFields.
     *
     * Whether multiple insert sets will be run in a single query or multiple
     * queries is left to individual drivers to implement in whatever manner is
     * most appropriate. The order of values in each sub-array must match the
     * order of fields in $insertFields.
     *
     * @var array
     */
    protected $insertValues = [];
    
    /**
     * Adds a set of field->value pairs to be inserted.
     *
     * This method may only be called once. Calling it a second time will be
     * ignored. To queue up multiple sets of values to be inserted at once,
     * use the values() method.
     *
     * @param array $fields
     *   An array of fields on which to insert. This array may be indexed or
     *   associative. If indexed, the array is taken to be the list of fields.
     *   If associative, the keys of the array are taken to be the fields and
     *   the values are taken to be corresponding values to insert. If a
     *   $values argument is provided, $fields must be indexed.
     * @param array $values
     *   (optional) An array of fields to insert into the database. The values
     *   must be specified in the same order as the $fields array.
     *
     * @return $this
     *   The called object.
     */
    public function fields(array $fields, array $values = []) {
        if (empty($this->insertFields)) {
            if (empty($values)) {
                if (!is_numeric(key($fields))) {
                    $values = array_values($fields);
                    $fields = array_keys($fields);
                }
            }
            $this->insertFields = $fields;
            if (!empty($values)) {
                $this->insertValues[] = $values;
            }
        }
        return $this;
    }
    
    /**
     * Adds another set of values to the query to be inserted.
     *
     * If $values is a numeric-keyed array, it will be assumed to be in the same
     * order as the original fields() call. If it is associative, it may be
     * in any order as long as the keys of the array match the names of the
     * fields.
     *
     * @param array $values
     *   An array of values to add to the query.
     *
     * @return $this
     *   The called object.
     */
    public function values(array $values) {
        if (is_numeric(key($values))) {
            $this->insertValues[] = $values;
        }
        elseif ($this->insertFields) {
            // Reorder the submitted values to match the fields array.
            foreach ($this->insertFields as $key) {
                $insert_values[$key] = $values[$key];
            }
            // For consistency, the values array is always numerically indexed.
            $this->insertValues[] = array_values($insert_values);
        }
        return $this;
    }
    
    /**
     * Specifies fields for which the database defaults should be used.
     *
     * If you want to force a given field to use the database-defined default,
     * not NULL or undefined, use this method to instruct the database to use
     * default values explicitly. In most cases this will not be necessary
     * unless you are inserting a row that is all default values, as you cannot
     * specify no values in an INSERT query.
     *
     * Specifying a field both in fields() and in useDefaults() is an error
     * and will not execute.
     *
     * @param array $fields
     *   An array of values for which to use the default values
     *   specified in the table definition.
     *
     * @return $this
     *   The called object.
     */
    public function useDefaults(array $fields) {
        $this->defaultFields = $fields;
        return $this;
    }
    
    /**
     * Returns the query placeholders for values that will be inserted.
     *
     * @param array $nested_insert_values
     *   A nested array of values to insert.
     * @param array $default_fields
     *   An array of fields that should be set to their database-defined defaults.
     *
     * @return array
     *   An array of insert placeholders.
     */
    protected function getInsertPlaceholderFragment(array $nested_insert_values, array $default_fields) {
        $max_placeholder = 0;
        $values = [];
        if ($nested_insert_values) {
            foreach ($nested_insert_values as $insert_values) {
                $placeholders = [];
                // Default fields aren't really placeholders, but this is the most convenient
                // way to handle them.
                $placeholders = array_pad($placeholders, count($default_fields), 'default');
                $new_placeholder = $max_placeholder + count($insert_values);
                for ($i = $max_placeholder; $i < $new_placeholder; ++$i) {
                    $placeholders[] = ':db_insert_placeholder_' . $i;
                }
                $max_placeholder = $new_placeholder;
                $values[] = '(' . implode(', ', $placeholders) . ')';
            }
        }
        else {
            // If there are no values, then this is a default-only query. We still need to handle that.
            $placeholders = array_fill(0, count($default_fields), 'default');
            $values[] = '(' . implode(', ', $placeholders) . ')';
        }
        return $values;
    }
    
    /**
     * {@inheritdoc}
     */
    public function count() : int {
        return count($this->insertValues);
    }

}