package atom

import "fmt"

type CommonAttributes struct {
	Base                IRI                   `xml:"base,attr,omitempty"`
	Lang                LanguageTag           `xml:"lang,attr,omitempty"`
	UndefinedAttributes []*ExtensionAttribute `xml:",attr"`
}

// NewCommonAttributes creates a new set of CommonAttributes. It returns a
// *CommonAttributes.
func NewCommonAttributes() *CommonAttributes {
	return new(CommonAttributes)
}

// AddExtensionAttribute adds the ExtensionAttribute to the CommonAttributes.
func (c *CommonAttributes) AddExtensionAttribute(e *ExtensionAttribute) {
	if c.UndefinedAttributes == nil {
		c.UndefinedAttributes = make([]*ExtensionAttribute, 1)
		c.UndefinedAttributes[0] = e
	} else {
		c.UndefinedAttributes = append(c.UndefinedAttributes, e)
	}
}

// Check checks the CommonAttributes for incompatibilities with RFC4287. It
// returns an error.
func (c *CommonAttributes) Check() error {
	for i, a := range c.UndefinedAttributes {
		if err := a.Check(); err != nil {
			return fmt.Errorf("extension attribute %v of common attributes: %v", i, err)
		}
	}

	return nil
}