package stories

import (
	"errors"

	"git.aiterp.net/rpdata/api/models"
	"github.com/globalsign/mgo/bson"
)

// ErrTagNotExists is an error returned by Story.RemoveTag
var ErrTagNotExists = errors.New("Tag does not exist on story")

// RemoveTag removes a tag to the story. It returns ErrTagNotExists if the tag does not exist.
func RemoveTag(story models.Story, tag models.Tag) (models.Story, error) {
	index := -1
	for i := range story.Tags {
		if story.Tags[i].Equal(tag) {
			index = i
			break
		}
	}
	if index == -1 {
		return models.Story{}, ErrTagNotExists
	}

	err := collection.UpdateId(story.ID, bson.M{"$pull": bson.M{"tags": tag}})
	if err != nil {
		return models.Story{}, err
	}

	story.Tags = append(story.Tags[:index], story.Tags[index+1:]...)

	return story, nil
}