package models

import (
	"errors"
	"fmt"
	"io"
)

// StoryCategory represents the category of a story.
type StoryCategory string

const (
	// StoryCategoryInfo is a story category, see GraphQL documentation.
	StoryCategoryInfo StoryCategory = "Info"
	// StoryCategoryNews is a story category, see GraphQL documentation.
	StoryCategoryNews StoryCategory = "News"
	// StoryCategoryDocument is a story category, see GraphQL documentation.
	StoryCategoryDocument StoryCategory = "Document"
	// StoryCategoryBackground is a story category, see GraphQL documentation.
	StoryCategoryBackground StoryCategory = "Background"
	// StoryCategoryStory is a story category, see GraphQL documentation.
	StoryCategoryStory StoryCategory = "Story"
)

// IsValid returns whether the category is one of the valid values.
func (e *StoryCategory) IsValid() bool {
	switch *e {
	case StoryCategoryInfo, StoryCategoryNews, StoryCategoryDocument, StoryCategoryBackground, StoryCategoryStory:
		return true
	default:
		return false
	}
}

// UnmarshalGQL unmarshals
func (e *StoryCategory) UnmarshalGQL(v interface{}) error {
	str, ok := v.(string)
	if !ok {
		return errors.New("enums must be strings")
	}

	*e = StoryCategory(str)
	if !e.IsValid() {
		return fmt.Errorf("\"%s\" is not a valid StoryCategory", str)
	}

	return nil
}

// MarshalGQL turns it into a JSON string
func (e StoryCategory) MarshalGQL(w io.Writer) {
	fmt.Fprint(w, "\""+string(e)+"\"")
}