package main

import (
	"encoding/json"
	"errors"
	"fmt"

	"github.com/xujiajun/nutsdb"
)

func ReadUser(username string) (*UserData, error) {
	data, err := DbRead(bucketUsers, username)
	if err != nil {
		return nil, err
	}
	var user UserData
	err = json.Unmarshal(data, &user)
	return &user, err
}

func SaveUser(user *UserData) error {
	data, err := json.Marshal(user)
	if err != nil {
		return err
	}
	if user.Username == "" {
		return errors.New("user empty")
	}
	err = DbSave(bucketUsers, user.Username, data)
	return err
}

func AddUserToAnime(username string, userId, animeId int64) (*AnimeUser, error) {
	var anime AnimeUser
	err := db.Update(
		func(tx *nutsdb.Tx) error {
			keyBytes := Int64ToByte(animeId)
			e, err := tx.Get(bucketAnime, keyBytes)
			var users []WatchUser
			if err != nil {
				users = make([]WatchUser, 0)
			} else {
				// parse user list
				users, err = parseUserList(e.Value)
				if err != nil {
					return err
				}
			}
			// check if user already part
			for _, u := range users {
				if u.MalID == userId {
					// early terminate
					anime = AnimeUser{
						Anime: animeId,
						Users: users,
					}
					return err
				}
			}

			// add user
			users = append(users, WatchUser{
				Username: username,
				MalID:    userId,
			})
			anime = AnimeUser{
				Anime: animeId,
				Users: users,
			}
			newData, err := json.Marshal(users)
			if err != nil {
				return err
			}
			return tx.Put(bucketAnime, keyBytes, newData, nutsdb.Persistent)
		})
	return &anime, err
}

func DeleteUserFromAnime(username string, userId, animeId int64) (*AnimeUser, error) {
	var anime AnimeUser
	err := db.Update(
		func(tx *nutsdb.Tx) error {
			keyBytes := Int64ToByte(animeId)
			e, err := tx.Get(bucketAnime, keyBytes)
			var users []WatchUser
			if err != nil {
				users = make([]WatchUser, 0)
			} else {
				// parse user list
				users, err = parseUserList(e.Value)
				if err != nil {
					return err
				}
			}
			// check if user already part
			for i, u := range users {
				// early terminate
				if u.MalID == userId {
					// delete user from list
					users[i] = users[len(users)-1]
					users = users[:len(users)-1]
					// check if anime needs recycling
					anime = AnimeUser{
						Anime: animeId,
						Users: users,
					}
					if len(users) == 0 {
						return tx.Delete(bucketAnime, keyBytes)
					}
					newData, err := json.Marshal(users)
					if err != nil {
						return err
					}
					return tx.Put(bucketAnime, keyBytes, newData, nutsdb.Persistent)
				}
			}
			return fmt.Errorf("%s %d schaut nicht %d", username, userId, animeId)
		})
	return &anime, err
}

func DeleteUserFromAnimes(userId int64) error {
	return db.Update(
		func(tx *nutsdb.Tx) error {
			entries, err := tx.GetAll(bucketAnime)
			if err != nil {
				return err
			}
			// iterate entries
			for _, e := range entries {
				// parse user list
				users, err := parseUserList(e.Value)
				if err != nil {
					return err
				}
				// check if user is part
				for i, u := range users {
					if u.MalID == userId {
						// delete user from list
						users[i] = users[len(users)-1]
						users = users[:len(users)-1]
						// check if anime needs recycling
						if len(users) == 0 {
							err = tx.Delete(bucketAnime, e.Key)
							if err != nil {
								return err
							}
						} else {
							newData, err := json.Marshal(users)
							if err != nil {
								return err
							}
							err = tx.Put(bucketAnime, e.Key, newData, nutsdb.Persistent)
							if err != nil {
								return err
							}
						}

						break
					}
				}
			}
			return nil
		})
}

func ReadAnimeUsers() ([]AnimeUser, error) {
	var animes []AnimeUser
	err := db.View(
		func(tx *nutsdb.Tx) error {
			entries, err := tx.GetAll(bucketAnime)
			if err != nil {
				return err
			}
			animes = make([]AnimeUser, 0)
			// iterate entries
			for _, e := range entries {
				// decode anime list
				animeId, err := BytesToInt64(e.Key)
				if err != nil {
					return err
				}
				// parse user list
				users, err := parseUserList(e.Value)
				if err != nil {
					return err
				}
				anime := AnimeUser{
					Anime: animeId,
					Users: users,
				}
				animes = append(animes, anime)
			}
			return nil
		})
	return animes, err
}

func DbClean() error {
	return db.Update(
		func(tx *nutsdb.Tx) error {
			return db.Merge()
		})
}

func DbSave(bucket, key string, val []byte) error {
	return db.Update(
		func(tx *nutsdb.Tx) error {
			keyBytes := []byte(key)
			return tx.Put(bucket, keyBytes, val, nutsdb.Persistent)
		})
}

func DbRead(bucket, key string) ([]byte, error) {
	var val []byte
	err := db.View(
		func(tx *nutsdb.Tx) error {
			keyBytes := []byte(key)
			e, err := tx.Get(bucket, keyBytes)
			if err != nil {
				return err
			}
			val = make([]byte, len(e.Value))
			copy(val, e.Value)
			return err
		})
	return val, err
}

func DbDelete(bucket, key string) error {
	return db.Update(
		func(tx *nutsdb.Tx) error {
			keyBytes := []byte(key)
			return tx.Delete(bucket, keyBytes)
		})
}

func parseUserList(data []byte) ([]WatchUser, error) {
	var users []WatchUser
	err := json.Unmarshal(data, &users)
	return users, err
}