package eventstore

import (
	"context"
	"encoding/json"
	"reflect"
	"sync"

	"github.com/caos/zitadel/internal/errors"
	"github.com/caos/zitadel/internal/eventstore/v2/repository"
)

//Eventstore abstracts all functions needed to store valid events
// and filters the stored events
type Eventstore struct {
	repo              repository.Repository
	interceptorMutex  sync.Mutex
	eventInterceptors map[EventType]eventTypeInterceptors
}

type eventTypeInterceptors struct {
	eventMapper func(*repository.Event) (EventReader, error)
}

func NewEventstore(repo repository.Repository) *Eventstore {
	return &Eventstore{
		repo:              repo,
		eventInterceptors: map[EventType]eventTypeInterceptors{},
		interceptorMutex:  sync.Mutex{},
	}
}

//Health checks if the eventstore can properly work
// It checks if the repository can serve load
func (es *Eventstore) Health(ctx context.Context) error {
	return es.repo.Health(ctx)
}

//PushAggregate pushes the aggregate and reduces the new events on the aggregate
func (es *Eventstore) PushAggregate(ctx context.Context, writeModel queryReducer, aggregate aggregater) error {
	events, err := es.PushAggregates(ctx, aggregate)
	if err != nil {
		return err
	}

	writeModel.AppendEvents(events...)
	return writeModel.Reduce()
}

//PushAggregates maps the events of all aggregates to an eventstore event
// based on the pushMapper
func (es *Eventstore) PushAggregates(ctx context.Context, aggregates ...aggregater) ([]EventReader, error) {
	events, err := es.aggregatesToEvents(aggregates)
	if err != nil {
		return nil, err
	}

	err = es.repo.Push(ctx, events...)
	if err != nil {
		return nil, err
	}

	return es.mapEvents(events)
}

func (es *Eventstore) aggregatesToEvents(aggregates []aggregater) ([]*repository.Event, error) {
	events := make([]*repository.Event, 0, len(aggregates))
	for _, aggregate := range aggregates {
		var previousEvent *repository.Event
		for _, event := range aggregate.Events() {
			data, err := eventData(event)
			if err != nil {
				return nil, err
			}
			events = append(events, &repository.Event{
				AggregateID:           aggregate.ID(),
				AggregateType:         repository.AggregateType(aggregate.Type()),
				ResourceOwner:         aggregate.ResourceOwner(),
				EditorService:         event.EditorService(),
				EditorUser:            event.EditorUser(),
				Type:                  repository.EventType(event.Type()),
				Version:               repository.Version(aggregate.Version()),
				PreviousEvent:         previousEvent,
				PreviousSequence:      aggregate.PreviousSequence(),
				Data:                  data,
				CheckPreviousSequence: event.CheckPrevious(),
			})
			previousEvent = events[len(events)-1]
		}
	}
	return events, nil
}

//FilterEvents filters the stored events based on the searchQuery
// and maps the events to the defined event structs
func (es *Eventstore) FilterEvents(ctx context.Context, queryFactory *SearchQueryBuilder) ([]EventReader, error) {
	query, err := queryFactory.build()
	if err != nil {
		return nil, err
	}
	events, err := es.repo.Filter(ctx, query)
	if err != nil {
		return nil, err
	}

	return es.mapEvents(events)
}

func (es *Eventstore) mapEvents(events []*repository.Event) (mappedEvents []EventReader, err error) {
	mappedEvents = make([]EventReader, len(events))

	es.interceptorMutex.Lock()
	defer es.interceptorMutex.Unlock()

	for i, event := range events {
		interceptors, ok := es.eventInterceptors[EventType(event.Type)]
		if !ok || interceptors.eventMapper == nil {
			mappedEvents[i] = BaseEventFromRepo(event)
			//TODO: return error if unable to map event
			continue
			// return nil, errors.ThrowPreconditionFailed(nil, "V2-usujB", "event mapper not defined")
		}
		mappedEvents[i], err = interceptors.eventMapper(event)
		if err != nil {
			return nil, err
		}
	}

	return mappedEvents, nil
}

type reducer interface {
	//Reduce handles the events of the internal events list
	// it only appends the newly added events
	Reduce() error
	//AppendEvents appends the passed events to an internal list of events
	AppendEvents(...EventReader)
}

//FilterToReducer filters the events based on the search query, appends all events to the reducer and calls it's reduce function
func (es *Eventstore) FilterToReducer(ctx context.Context, searchQuery *SearchQueryBuilder, r reducer) error {
	events, err := es.FilterEvents(ctx, searchQuery)
	if err != nil {
		return err
	}

	r.AppendEvents(events...)

	return r.Reduce()
}

//LatestSequence filters the latest sequence for the given search query
func (es *Eventstore) LatestSequence(ctx context.Context, queryFactory *SearchQueryBuilder) (uint64, error) {
	query, err := queryFactory.build()
	if err != nil {
		return 0, err
	}
	return es.repo.LatestSequence(ctx, query)
}

type queryReducer interface {
	reducer
	//Query returns the SearchQueryFactory for the events needed in reducer
	Query() *SearchQueryBuilder
}

//FilterToQueryReducer filters the events based on the search query of the query function,
// appends all events to the reducer and calls it's reduce function
func (es *Eventstore) FilterToQueryReducer(ctx context.Context, r queryReducer) error {
	events, err := es.FilterEvents(ctx, r.Query())
	if err != nil {
		return err
	}
	r.AppendEvents(events...)

	return r.Reduce()
}

//RegisterFilterEventMapper registers a function for mapping an eventstore event to an event
func (es *Eventstore) RegisterFilterEventMapper(eventType EventType, mapper func(*repository.Event) (EventReader, error)) *Eventstore {
	if mapper == nil || eventType == "" {
		return es
	}
	es.interceptorMutex.Lock()
	defer es.interceptorMutex.Unlock()

	interceptor := es.eventInterceptors[eventType]
	interceptor.eventMapper = mapper
	es.eventInterceptors[eventType] = interceptor

	return es
}

func eventData(event EventPusher) ([]byte, error) {
	switch data := event.Data().(type) {
	case nil:
		return nil, nil
	case []byte:
		if json.Valid(data) {
			return data, nil
		}
		return nil, errors.ThrowInvalidArgument(nil, "V2-6SbbS", "data bytes are not json")
	}
	dataType := reflect.TypeOf(event.Data())
	if dataType.Kind() == reflect.Ptr {
		dataType = dataType.Elem()
	}
	if dataType.Kind() == reflect.Struct {
		dataBytes, err := json.Marshal(event.Data())
		if err != nil {
			return nil, errors.ThrowInvalidArgument(err, "V2-xG87M", "could  not marhsal data")
		}
		return dataBytes, nil
	}
	return nil, errors.ThrowInvalidArgument(nil, "V2-91NRm", "wrong type of event data")
}