package atom

import "fmt"

type CommonAttributes struct {
	Base                IRI         `xml:"base,attr,omitempty"`
	Lang                LanguageTag `xml:"lang,attr,omitempty"`
	UndefinedAttributes []string    `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(name, value string) {
	if c.UndefinedAttributes == nil {
		c.UndefinedAttributes = make([]string, 1)
		c.UndefinedAttributes[0] = fmt.Sprint(name, `="`, value, `"`)
	} else {
		c.UndefinedAttributes = append(c.UndefinedAttributes, fmt.Sprint(name, `="`, value, `"`))
	}
}

// Check checks the CommonAttributes for incompatibilities with RFC4287. It
// returns an error.
func (c *CommonAttributes) Check() error {
	for _, a := range c.UndefinedAttributes {
		if !isValidAttribute(a) {
			return fmt.Errorf("attribute %v of undefined attributes of common attributes not correctly formatted", a)
		}
	}

	return nil
}