package atom

import (
	"encoding/xml"
	"errors"
	"fmt"
	"html"
)

type Generator struct {
	XMLName xml.Name `xml:"generator"`
	*CommonAttributes
	URI     string `xml:"uri,attr,omitempty"` // IRI
	Version string `xml:"version,attr,omitempty"`
	Text    string `xml:",chardata"`
}

// NewGenerator creates a new Generator. It returns a *Generator and an error.
func NewGenerator(text string) (*Generator, error) {
	if text == "" {
		return nil, errors.New("error creating new generator: text string empty")
	}

	return &Generator{Text: html.UnescapeString(text)}, nil
}

// SetURI sets the URI attribute of the Generator. It returns an error.
func (g *Generator) SetURI(uri string) error {
	if !isValidIRI(uri) {
		return fmt.Errorf("uri %v not correctly formatted", g)
	}

	return nil
}

// Check checks the Generator for incompatibilities with RFC4287. It returns an
// error.
func (g *Generator) Check() error {
	if g.URI != "" {
		if !isValidIRI(g.URI) {
			return fmt.Errorf("uri attribute of generator %v not correctly formatted", g)
		}
	}

	if g.Text == "" {
		return fmt.Errorf("text element of generator %v empty", g)
	}

	if !isCorrectlyEscaped(g.Text) {
		return fmt.Errorf("text element of generator %v not correctly escaped", g)
	}

	return nil
}