package story

import (
	"crypto/rand"
	"encoding/binary"
	"errors"
	"fmt"
	"os"
	"strconv"
	"time"

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

var storyCollection *mgo.Collection

// ErrTagAlreadyExists is an error returned by Story.AddTag
var ErrTagAlreadyExists = errors.New("Tag already exists")

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

// A Story is user content that does not have a wiki-suitable format. Documents, new stories, short stories, and so on.
// The story model is a container for multiple chapters this time, in contrast to the previous version.
type Story struct {
	ID            string    `bson:"_id"`
	Author        string    `bson:"author"`
	Name          string    `bson:"name"`
	Category      string    `bson:"category"`
	Open          bool      `bson:"open"`
	Listed        bool      `bson:"listed"`
	Tags          []Tag     `bson:"tags"`
	CreatedDate   time.Time `bson:"createdDate"`
	FictionalDate time.Time `bson:"fictionalDate,omitempty"`
	UpdatedDate   time.Time `bson:"updatedDate"`
}

// AddTag adds a tag to the story. It returns ErrTagAlreadyExists if the tag is already there
func (story *Story) AddTag(tag Tag) error {
	for i := range story.Tags {
		if story.Tags[i].Equal(tag) {
			return ErrTagAlreadyExists
		}
	}

	err := storyCollection.UpdateId(story.ID, bson.M{"$push": bson.M{"tags": tag}})
	if err != nil {
		return err
	}

	story.Tags = append(story.Tags, tag)

	return nil
}

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

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

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

	return nil
}

// Edit edits the story, reflecting the new values in the story's struct values. If nothing will be
// changed, it will silently return without a database roundtrip.
func (story *Story) Edit(name, category *string, listed, open *bool, fictionalDate *time.Time) error {
	changes := bson.M{}
	changed := *story

	if name != nil && *name == story.Name {
		changes["name"] = *name
		changed.Name = *name
	}
	if category != nil && *category == story.Category {
		changes["category"] = *category
		changed.Name = *category
	}
	if listed != nil && *listed == story.Listed {
		changes["listed"] = *listed
		changed.Listed = *listed
	}
	if open != nil && *open == story.Open {
		changes["open"] = *open
		changed.Open = *open
	}
	if fictionalDate != nil && *fictionalDate == story.FictionalDate {
		changes["fictionalDate"] = *fictionalDate
		changed.FictionalDate = *fictionalDate
	}

	if len(changes) == 0 {
		return nil
	}

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

	*story = changed

	return nil
}

// Remove the story from the database
func (story *Story) Remove() error {
	return storyCollection.RemoveId(story.ID)
}

// AddChapter adds a chapter to the story. This does not enforce the `Open` setting, but it will log a warning if it
// occurs
func (story *Story) AddChapter(title, author, source string, createdDate, finctionalDate time.Time) (Chapter, error) {
	if !story.Open && author != story.Author {
		fmt.Fprintf(os.Stderr, "WARNING: AddChapter is breaking Open rules (story.id=%#+v, story.name=%#+v, chapter.author=%#+v, chapter.title=%#+v)", story.ID, story.Name, author, title)
	}

	chapter := Chapter{
		ID:            makeChapterID(),
		StoryID:       story.ID,
		Title:         title,
		Author:        author,
		Source:        source,
		CreatedDate:   createdDate,
		FictionalDate: finctionalDate,
		EditedDate:    createdDate,
	}

	err := chapterCollection.Insert(chapter)
	if err != nil {
		return Chapter{}, err
	}

	if createdDate.After(story.UpdatedDate) {
		if err := storyCollection.UpdateId(story.ID, bson.M{"$set": bson.M{"updatedDate": createdDate}}); err == nil {
			story.UpdatedDate = createdDate
		}
	}

	return chapter, nil
}

// New creates a new story.
func New(name, author, category string, listed, open bool, tags []Tag, createdDate, fictionalDate time.Time) (Story, error) {
	story := Story{
		ID:            makeStoryID(),
		Name:          name,
		Author:        author,
		Category:      category,
		Listed:        listed,
		Open:          open,
		Tags:          tags,
		CreatedDate:   createdDate,
		FictionalDate: fictionalDate,
		UpdatedDate:   createdDate,
	}

	err := storyCollection.Insert(story)
	if err != nil {
		return Story{}, err
	}

	return story, nil
}

// FindID finds a story by ID
func FindID(id string) (Story, error) {
	story := Story{}
	err := storyCollection.FindId(id).One(&story)

	return story, err
}

// List lists stories by any non-zero criteria passed with it.
func List(author string, tags []Tag, earliest, latest time.Time, limit int) ([]Story, error) {
	query := bson.M{}

	if author != "" {
		query["author"] = author
	}

	if len(tags) > 0 {
		query["tags"] = bson.M{"$in": tags}
	}

	if !earliest.IsZero() && !latest.IsZero() {
		query["fictionalDate"] = bson.M{
			"$gte": earliest,
			"$lt":  latest,
		}
	} else if !latest.IsZero() {
		query["fictionalDate"] = bson.M{
			"$lt": latest,
		}
	} else if !earliest.IsZero() {
		query["fictionalDate"] = bson.M{
			"$gte": earliest,
		}
	}

	stories := make([]Story, 0, 128)
	err := storyCollection.Find(query).Limit(limit).One(&stories)

	return stories, err
}

// makeStoryID makes a random story ID that's 16 characters long
func makeStoryID() string {
	result := "S"
	offset := 0
	data := make([]byte, 32)

	rand.Read(data)
	for len(result) < 16 {
		result += strconv.FormatUint(binary.LittleEndian.Uint64(data[offset:]), 36)
		offset += 8

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

	return result[:16]
}

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

		storyCollection.EnsureIndexKey("tags")
		storyCollection.EnsureIndexKey("author")
		storyCollection.EnsureIndexKey("updatedDate")
		storyCollection.EnsureIndexKey("fictionalDate")
		storyCollection.EnsureIndexKey("listed")
	})
}