package tenant

import (
	"context"
	"encoding/json"
	"time"

	"github.com/influxdata/influxdb/v2"
	"github.com/influxdata/influxdb/v2/kit/platform"
	"github.com/influxdata/influxdb/v2/kv"
)

const (
	orgOperationLogKeyPrefix    = "org"
	bucketOperationLogKeyPrefix = "bucket"
	userOperationLogKeyPrefix   = "user"
)

// OpLogStore is a type which persists and reports operation log entries on a backing
// kv store transaction.
type OpLogStore interface {
	AddLogEntryTx(ctx context.Context, tx kv.Tx, k, v []byte, t time.Time) error
	ForEachLogEntryTx(ctx context.Context, tx kv.Tx, k []byte, opts influxdb.FindOptions, fn func([]byte, time.Time) error) error
}

// OpLogService is a type which stores operation logs for buckets, users and orgs.
type OpLogService struct {
	kv kv.Store

	opLogStore OpLogStore

	TimeGenerator influxdb.TimeGenerator
}

// NewOpLogService constructs and configures a new op log service.
func NewOpLogService(store kv.Store, opLogStore OpLogStore) *OpLogService {
	return &OpLogService{
		kv:            store,
		opLogStore:    opLogStore,
		TimeGenerator: influxdb.RealTimeGenerator{},
	}
}

// GetOrganizationOperationLog retrieves a organization operation log.
func (s *OpLogService) GetOrganizationOperationLog(ctx context.Context, id platform.ID, opts influxdb.FindOptions) ([]*influxdb.OperationLogEntry, int, error) {
	// TODO(desa): might be worthwhile to allocate a slice of size opts.Limit
	log := []*influxdb.OperationLogEntry{}

	err := s.kv.View(ctx, func(tx kv.Tx) error {
		key, err := encodeOrganizationOperationLogKey(id)
		if err != nil {
			return err
		}

		return s.opLogStore.ForEachLogEntryTx(ctx, tx, key, opts, func(v []byte, t time.Time) error {
			e := &influxdb.OperationLogEntry{}
			if err := json.Unmarshal(v, e); err != nil {
				return err
			}
			e.Time = t

			log = append(log, e)

			return nil
		})
	})

	if err != nil && err != kv.ErrKeyValueLogBoundsNotFound {
		return nil, 0, err
	}

	return log, len(log), nil
}

// GetBucketOperationLog retrieves a buckets operation log.
func (s *OpLogService) GetBucketOperationLog(ctx context.Context, id platform.ID, opts influxdb.FindOptions) ([]*influxdb.OperationLogEntry, int, error) {
	// TODO(desa): might be worthwhile to allocate a slice of size opts.Limit
	log := []*influxdb.OperationLogEntry{}

	err := s.kv.View(ctx, func(tx kv.Tx) error {
		key, err := encodeBucketOperationLogKey(id)
		if err != nil {
			return err
		}

		return s.opLogStore.ForEachLogEntryTx(ctx, tx, key, opts, func(v []byte, t time.Time) error {
			e := &influxdb.OperationLogEntry{}
			if err := json.Unmarshal(v, e); err != nil {
				return err
			}
			e.Time = t

			log = append(log, e)

			return nil
		})
	})

	if err != nil && err != kv.ErrKeyValueLogBoundsNotFound {
		return nil, 0, err
	}

	return log, len(log), nil
}

// GetUserOperationLog retrieves a user operation log.
func (s *OpLogService) GetUserOperationLog(ctx context.Context, id platform.ID, opts influxdb.FindOptions) ([]*influxdb.OperationLogEntry, int, error) {
	// TODO(desa): might be worthwhile to allocate a slice of size opts.Limit
	log := []*influxdb.OperationLogEntry{}

	err := s.kv.View(ctx, func(tx kv.Tx) error {
		key, err := encodeUserOperationLogKey(id)
		if err != nil {
			return err
		}

		return s.opLogStore.ForEachLogEntryTx(ctx, tx, key, opts, func(v []byte, t time.Time) error {
			e := &influxdb.OperationLogEntry{}
			if err := json.Unmarshal(v, e); err != nil {
				return err
			}
			e.Time = t

			log = append(log, e)

			return nil
		})
	})

	if err != nil && err != kv.ErrKeyValueLogBoundsNotFound {
		return nil, 0, err
	}

	return log, len(log), nil
}

func encodeOrganizationOperationLogKey(id platform.ID) ([]byte, error) {
	buf, err := id.Encode()
	if err != nil {
		return nil, err
	}
	return append([]byte(orgOperationLogKeyPrefix), buf...), nil
}

func encodeBucketOperationLogKey(id platform.ID) ([]byte, error) {
	buf, err := id.Encode()
	if err != nil {
		return nil, err
	}
	return append([]byte(bucketOperationLogKeyPrefix), buf...), nil
}

func encodeUserOperationLogKey(id platform.ID) ([]byte, error) {
	buf, err := id.Encode()
	if err != nil {
		return nil, err
	}
	return append([]byte(userOperationLogKeyPrefix), buf...), nil
}