package atom

import (
	"encoding/xml"
	"fmt"
)

type Category struct {
	XMLName xml.Name `xml:"category"`
	*CommonAttributes
	Term   string `xml:"term,attr"`
	Scheme string `xml:"scheme,attr,omitempty"` // IRI
	Label  string `xml:"label,attr,omitempty"`  // Must be unescaped
}

// NewCategory creates a new Category. It returns a *Category.
func NewCategory(term string) *Category {
	return &Category{
		CommonAttributes: newCommonAttributes(),
		Term:             term,
	}
}

// Check checks the Category for incompatibilities with RFC4287. It returns an
// error.
func (c *Category) Check() error {
	if c.Term == "" {
		return fmt.Errorf("term attribute of category %v empty", c)
	}

	if c.Scheme != "" {
		if !isValidIRI(c.Scheme) {
			return fmt.Errorf("scheme attribute of category %v not correctly formatted", c)
		}
	}

	if !isCorrectlyEscaped(c.Label) {
		return fmt.Errorf("label attribute of category %v not correctly escaped", c)
	}

	return nil
}