package bbgo

import (
	"fmt"
	"reflect"

	log "github.com/sirupsen/logrus"

	"github.com/c9s/bbgo/pkg/dynamic"
	"github.com/c9s/bbgo/pkg/service"
)

type PersistenceSelector struct {
	// StoreID is the store you want to use.
	StoreID string `json:"store" yaml:"store"`

	// Type is the persistence type
	Type string `json:"type" yaml:"type"`
}

var DefaultPersistenceServiceFacade = &service.PersistenceServiceFacade{
	Memory: service.NewMemoryService(),
}

var PersistenceServiceFacade = DefaultPersistenceServiceFacade

// Persistence is used for strategy to inject the persistence.
type Persistence struct {
	PersistenceSelector *PersistenceSelector `json:"persistence,omitempty" yaml:"persistence,omitempty"`
}

func (p *Persistence) backendService(t string) (service.PersistenceService, error) {
	switch t {
	case "json":
		return PersistenceServiceFacade.Json, nil

	case "redis":
		if PersistenceServiceFacade.Redis == nil {
			log.Warn("redis persistence is not available, fallback to memory backend")
			return PersistenceServiceFacade.Memory, nil
		}
		return PersistenceServiceFacade.Redis, nil

	case "memory":
		return PersistenceServiceFacade.Memory, nil

	}

	return nil, fmt.Errorf("unsupported persistent type %s", t)
}

func (p *Persistence) Load(val interface{}, subIDs ...string) error {
	ps, err := p.backendService(p.PersistenceSelector.Type)
	if err != nil {
		return err
	}

	log.Debugf("using persistence store %T for loading", ps)

	if p.PersistenceSelector.StoreID == "" {
		p.PersistenceSelector.StoreID = "default"
	}

	store := ps.NewStore(p.PersistenceSelector.StoreID, subIDs...)
	return store.Load(val)
}

func (p *Persistence) Save(val interface{}, subIDs ...string) error {
	ps, err := p.backendService(p.PersistenceSelector.Type)
	if err != nil {
		return err
	}

	log.Debugf("using persistence store %T for storing", ps)

	if p.PersistenceSelector.StoreID == "" {
		p.PersistenceSelector.StoreID = "default"
	}

	store := ps.NewStore(p.PersistenceSelector.StoreID, subIDs...)
	return store.Save(val)
}

func (p *Persistence) Sync(obj interface{}) error {
	id := callID(obj)
	if len(id) == 0 {
		return nil
	}

	ps := PersistenceServiceFacade.Get()
	return storePersistenceFields(obj, id, ps)
}

// Sync syncs the object properties into the persistence layer
func Sync(obj interface{}) {
	id := callID(obj)
	if len(id) == 0 {
		log.Warnf("InstanceID() is not provided, can not sync persistence")
		return
	}

	ps := PersistenceServiceFacade.Get()
	err := storePersistenceFields(obj, id, ps)
	if err != nil {
		log.WithError(err).Errorf("persistence sync failed")
	}
}

func loadPersistenceFields(obj interface{}, id string, persistence service.PersistenceService) error {
	return dynamic.IterateFieldsByTag(obj, "persistence", func(tag string, field reflect.StructField, value reflect.Value) error {
		log.Debugf("[loadPersistenceFields] loading value into field %v, tag = %s, original value = %v", field, tag, value)

		newValueInf := dynamic.NewTypeValueInterface(value.Type())
		// inf := value.Interface()
		store := persistence.NewStore("state", id, tag)
		if err := store.Load(&newValueInf); err != nil {
			if err == service.ErrPersistenceNotExists {
				log.Debugf("[loadPersistenceFields] state key does not exist, id = %v, tag = %s", id, tag)
				return nil
			}

			return err
		}

		newValue := reflect.ValueOf(newValueInf)
		if value.Kind() != reflect.Ptr && newValue.Kind() == reflect.Ptr {
			newValue = newValue.Elem()
		}

		log.Debugf("[loadPersistenceFields] %v = %v -> %v\n", field, value, newValue)

		value.Set(newValue)
		return nil
	})
}

func storePersistenceFields(obj interface{}, id string, persistence service.PersistenceService) error {
	return dynamic.IterateFieldsByTag(obj, "persistence", func(tag string, ft reflect.StructField, fv reflect.Value) error {
		log.Debugf("[storePersistenceFields] storing value from field %v, tag = %s, original value = %v", ft, tag, fv)

		inf := fv.Interface()
		store := persistence.NewStore("state", id, tag)
		return store.Save(inf)
	})
}