package story

import (
	"crypto/rand"
	"encoding/binary"
	"strconv"
	"time"

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

var chapterCollection *mgo.Collection

// A Chapter is a part of a story.
type Chapter struct {
	ID            string    `bson:"_id"`
	StoryID       string    `bson:"storyId"`
	Title         string    `bson:"title"`
	Author        string    `bson:"author"`
	Source        string    `bson:"source"`
	CreatedDate   time.Time `bson:"createdDate"`
	FictionalDate time.Time `bson:"fictionalDate,omitempty"`
	EditedDate    time.Time `bson:"editedDate"`
}

// Edit edits a chapter, and updates EditedDate. While many Edit functions cheat if there's nothing to
// change, this functill will due to EditedDate.
func (chapter *Chapter) Edit(title, source *string, fictionalDate *time.Time) error {
	now := time.Now()
	changes := bson.M{"editedDate": now}
	changed := *chapter
	changed.EditedDate = now

	if title != nil && *title != chapter.Title {
		changes["title"] = *title
		changed.Title = *title
	}
	if source != nil && *source != chapter.Source {
		changes["source"] = *source
		changed.Source = *source
	}
	if fictionalDate != nil && *fictionalDate != chapter.FictionalDate {
		changes["fictionalDate"] = *fictionalDate
		changed.FictionalDate = *fictionalDate
	}

	err := chapterCollection.UpdateId(chapter.ID, bson.M{"$set": changes})
	if err != nil {
		return err
	}

	*chapter = changed

	return nil
}

// Remove removes a chapter.
func (chapter *Chapter) Remove() error {
	return chapterCollection.RemoveId(chapter.ID)
}

// FindChapterID finds a chapter by its own ID
func FindChapterID(id string) (Chapter, error) {
	chapter := Chapter{}
	err := chapterCollection.FindId(id).One(&chapter)

	return chapter, err
}

// ListChapterStoryID lists all chapters for the story ID
func ListChapterStoryID(storyID string) ([]Chapter, error) {
	chapters := make([]Chapter, 0, 8)
	err := chapterCollection.Find(bson.M{"storyId": storyID}).Sort("createdDate").All(&chapters)
	if err != nil {
		return nil, err
	}

	return chapters, nil
}

// makeChapterID makes a random chapter ID that's 24 characters long
func makeChapterID() string {
	result := "SC"
	offset := 0
	data := make([]byte, 32)

	rand.Read(data)
	for len(result) < 24 {
		result += strconv.FormatUint(binary.LittleEndian.Uint64(data[offset:]), 36)
		offset += 8

		if offset >= 32 {
			rand.Read(data)
			offset = 0
		}
	}

	return result[:24]
}

func init() {
	store.HandleInit(func(db *mgo.Database) {
		chapterCollection = db.C("story.chapters")

		chapterCollection.EnsureIndexKey("storyId")
		chapterCollection.EnsureIndexKey("author")
		chapterCollection.EnsureIndexKey("createdDate")
	})
}