package bolt

import (
	"context"
	"github.com/gisle/stufflog/database/repositories"
	"github.com/gisle/stufflog/models"
	"github.com/gisle/stufflog/slerrors"
	"github.com/vmihailenco/msgpack/v4"
	"go.etcd.io/bbolt"
)

var bnPeriods = []byte("Period")

type periodRepository struct {
	db            *bbolt.DB
	userIdIdx     *index
	activityIdIdx *index
}

func (r *periodRepository) FindID(ctx context.Context, id string) (*models.Period, error) {
	period := new(models.Period)
	err := r.db.View(func(tx *bbolt.Tx) error {
		value := tx.Bucket(bnPeriods).Get(unsafeStringToBytes(id))
		if value == nil {
			return slerrors.NotFound("Period")
		}
		err := msgpack.Unmarshal(value, period)
		if err != nil {
			return err
		}
		return nil
	})
	if err != nil {
		return nil, err
	}

	return period, nil
}

func (r *periodRepository) List(ctx context.Context) ([]*models.Period, error) {
	periods := make([]*models.Period, 0, 16)
	err := r.db.View(func(tx *bbolt.Tx) error {
		cursor := tx.Bucket(bnPeriods).Cursor()

		for key, value := cursor.First(); key != nil; key, value = cursor.Next() {
			period := new(models.Period)
			err := msgpack.Unmarshal(value, period)
			if err != nil {
				return err
			}

			periods = append(periods, period)
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	return periods, nil
}

func (r *periodRepository) ListUser(ctx context.Context, user models.User) ([]*models.Period, error) {
	periods := make([]*models.Period, 0, 16)
	err := r.db.View(func(tx *bbolt.Tx) error {
		bucket := tx.Bucket(bnPeriods)

		ids, err := r.userIdIdx.WithTx(tx).Get(user.ID)
		if err != nil {
			return err
		}

		for _, id := range ids {
			value := bucket.Get(id)
			if value == nil {
				continue
			}

			period := new(models.Period)
			err := msgpack.Unmarshal(value, period)
			if err != nil {
				return err
			}

			periods = append(periods, period)
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	return periods, nil
}

func (r *periodRepository) ListActivity(ctx context.Context, activity models.Activity) ([]*models.Period, error) {
	periods := make([]*models.Period, 0, 16)
	err := r.db.View(func(tx *bbolt.Tx) error {
		bucket := tx.Bucket(bnPeriods)

		ids, err := r.activityIdIdx.WithTx(tx).Get(activity.ID)
		if err != nil {
			return err
		}

		for _, id := range ids {
			value := bucket.Get(id)
			if value == nil {
				continue
			}

			period := new(models.Period)
			err := msgpack.Unmarshal(value, period)
			if err != nil {
				return err
			}

			periods = append(periods, period)
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	return periods, nil

}

func (r *periodRepository) Insert(ctx context.Context, period models.Period) error {
	value, err := msgpack.Marshal(&period)
	if err != nil {
		return err
	}

	return r.db.Update(func(tx *bbolt.Tx) error {
		err := tx.Bucket(bnPeriods).Put(unsafeStringToBytes(period.ID), value)
		if err != nil {
			return err
		}

		err = r.index(tx, &period)
		if err != nil {
			return err
		}

		return nil
	})
}

func (r *periodRepository) Update(ctx context.Context, period models.Period, updates []*models.PeriodUpdate) (*models.Period, error) {
	err := r.db.Update(func(tx *bbolt.Tx) error {
		bucket := tx.Bucket(bnPeriods)

		// Re-Get to guarantee consistency.
		value := bucket.Get(unsafeStringToBytes(period.ID))
		if value == nil {
			return slerrors.NotFound("Activity")
		}
		err := msgpack.Unmarshal(value, &period)
		if err != nil {
			return err
		}

		// Perform updates
		didChange := false
		for _, update := range updates {
			changed, err := period.ApplyUpdate(*update)
			if err != nil {
				return err
			}
			if changed {
				didChange = true
			}
		}

		// Put back into bucket
		if didChange {
			value, err := msgpack.Marshal(&period)
			if err != nil {
				return err
			}

			err = bucket.Put(unsafeStringToBytes(period.ID), value)
			if err != nil {
				return err
			}

			err = r.index(tx, &period)
			if err != nil {
				return err
			}
		} else {
			return errUnchanged
		}

		return nil
	})
	if err != nil && err != errUnchanged {
		return nil, err
	}

	return &period, nil
}

func (r *periodRepository) Remove(ctx context.Context, period models.Period) error {
	return r.db.Update(func(tx *bbolt.Tx) error {
		err := tx.Bucket(bnPeriods).Delete(unsafeStringToBytes(period.ID))
		if err != nil {
			return err
		}

		err = r.unIndex(tx, &period)
		if err != nil {
			return err
		}

		return nil
	})
}

func (r *periodRepository) index(tx *bbolt.Tx, period *models.Period) error {
	idBytes := unsafeStringToBytes(period.ID)

	err := r.userIdIdx.WithTx(tx).Set(idBytes, period.UserID)
	if err != nil {
		return err
	}
	activityIDs := make([]string, 0, len(period.Goals))
	added := make(map[string]bool)
	for _, goal := range period.Goals {
		if !added[goal.ActivityID] {
			added[goal.ActivityID] = true
			activityIDs = append(activityIDs, goal.ActivityID)
		}
	}

	err = r.activityIdIdx.WithTx(tx).Set(idBytes, activityIDs...)
	if err != nil {
		return err
	}

	return nil
}

func (r *periodRepository) unIndex(tx *bbolt.Tx, period *models.Period) error {
	idBytes := unsafeStringToBytes(period.ID)

	err := r.userIdIdx.WithTx(tx).Set(idBytes)
	if err != nil {
		return err
	}
	err = r.activityIdIdx.WithTx(tx).Set(idBytes)
	if err != nil {
		return err
	}

	return nil
}

func newPeriodRepository(db *bbolt.DB) (repositories.PeriodRepository, error) {
	err := db.Update(func(tx *bbolt.Tx) error {
		_, err := tx.CreateBucketIfNotExists(bnPeriods)
		return err
	})
	if err != nil {
		return nil, err
	}

	userIdIdx, err := newModelIndex(db, "Period", "UserID")
	if err != nil {
		return nil, err
	}

	activityIdIdx, err := newModelIndex(db, "Period", "Goals.ActivityID")
	if err != nil {
		return nil, err
	}

	return &periodRepository{
		db:            db,
		userIdIdx:     userIdIdx,
		activityIdIdx: activityIdIdx,
	}, nil
}