package ingest

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
	"sync"
	"time"

	"github.com/tech/sendico/edge/callbacks/internal/events"
	"github.com/tech/sendico/pkg/merrors"
	pkgmsg "github.com/tech/sendico/pkg/messaging"
	cons "github.com/tech/sendico/pkg/messaging/consumer"
	me "github.com/tech/sendico/pkg/messaging/envelope"
	pon "github.com/tech/sendico/pkg/messaging/notifications/paymentorchestrator"
	np "github.com/tech/sendico/pkg/messaging/notifications/processor"
	"github.com/tech/sendico/pkg/mlogger"
	"github.com/tech/sendico/pkg/model"
	"go.mongodb.org/mongo-driver/v2/bson"
	"go.uber.org/zap"
)

const (
	loggerNameIngest = "ingest"
	logFieldSubject  = "subject"

	errBrokerRequired    = "ingest: broker is required"
	errEventsRequired    = "ingest: events service is required"
	errResolverRequired  = "ingest: subscriptions resolver is required"
	errInboxRepoRequired = "ingest: inbox repo is required"
	errTaskRepoRequired  = "ingest: task repo is required"
	configFieldBroker    = "broker"
	configFieldEvents    = "events"
	configFieldResolver  = "resolver"
	configFieldInboxRepo = "inboxRepo"
	configFieldTaskRepo  = "taskRepo"

	logFailedStartConsumer   = "Failed to start messaging consumer"
	logIngestConsumerStarted = "Ingest consumer started"
	logIngestConsumerStopped = "Ingest consumer stopped"
	logIngestConsumerWarn    = "Ingest consumer stopped with error"

	ingestResultOK           = "ok"
	ingestResultEmptyPayload = "empty_payload"
	ingestResultInvalidEvent = "invalid_event"
	ingestResultPayloadError = "payload_error"
	ingestResultInboxError   = "inbox_error"
	ingestResultDuplicate    = "duplicate"
	ingestResultResolveError = "resolve_error"
	ingestResultNoEndpoints  = "no_endpoints"
	ingestResultTaskError    = "task_error"
)

type service struct {
	logger mlogger.Logger
	deps   Dependencies
	event  model.NotificationEvent

	cancel context.CancelFunc
	wg     sync.WaitGroup
	once   sync.Once
	stop   sync.Once

	mu       sync.Mutex
	consumer pkgmsg.Consumer

	processor np.EnvelopeProcessor
}

func newService(deps Dependencies) (Service, error) {
	if deps.Broker == nil {
		return nil, merrors.InvalidArgument(errBrokerRequired, configFieldBroker)
	}
	if deps.Events == nil {
		return nil, merrors.InvalidArgument(errEventsRequired, configFieldEvents)
	}
	if deps.Resolver == nil {
		return nil, merrors.InvalidArgument(errResolverRequired, configFieldResolver)
	}
	if deps.InboxRepo == nil {
		return nil, merrors.InvalidArgument(errInboxRepoRequired, configFieldInboxRepo)
	}
	if deps.TaskRepo == nil {
		return nil, merrors.InvalidArgument(errTaskRepoRequired, configFieldTaskRepo)
	}

	logger := deps.Logger
	if logger == nil {
		logger = zap.NewNop()
	}

	svc := &service{
		logger: logger.Named(loggerNameIngest),
		deps:   deps,
	}
	svc.processor = pon.NewPaymentStatusUpdatedProcessor(svc.logger, svc.handlePaymentStatusUpdated)
	svc.event = svc.processor.GetSubject()

	return svc, nil
}

func (s *service) Start(ctx context.Context) {
	s.once.Do(func() {
		runCtx := ctx
		if runCtx == nil {
			runCtx = context.Background()
		}
		runCtx, s.cancel = context.WithCancel(runCtx)

		s.wg.Add(1)
		go func() {
			defer s.wg.Done()
			s.run(runCtx)
		}()
	})
}

func (s *service) Stop() {
	s.stop.Do(func() {
		if s.cancel != nil {
			s.cancel()
		}
		s.closeConsumer()
		s.wg.Wait()
	})
}

func (s *service) run(ctx context.Context) {
	consumer, err := cons.NewConsumer(s.logger, s.deps.Broker, s.event)
	if err != nil {
		s.logger.Error(logFailedStartConsumer, zap.String(logFieldSubject, s.event.ToString()), zap.Error(err))
		return
	}
	s.setConsumer(consumer)
	defer s.closeConsumer()

	s.logger.Info(logIngestConsumerStarted, zap.String(logFieldSubject, s.event.ToString()))
	if err := consumer.ConsumeMessages(func(messageCtx context.Context, envelope me.Envelope) error {
		select {
		case <-ctx.Done():
			return ctx.Err()
		default:
		}
		return s.processor.Process(messageCtx, envelope)
	}); err != nil && !errors.Is(err, context.Canceled) {
		s.logger.Warn(logIngestConsumerWarn, zap.String(logFieldSubject, s.event.ToString()), zap.Error(err))
	}
	s.logger.Info(logIngestConsumerStopped, zap.String(logFieldSubject, s.event.ToString()))
}

func (s *service) setConsumer(consumer pkgmsg.Consumer) {
	s.mu.Lock()
	s.consumer = consumer
	s.mu.Unlock()
}

func (s *service) closeConsumer() {
	s.mu.Lock()
	consumer := s.consumer
	s.consumer = nil
	s.mu.Unlock()
	if consumer != nil {
		consumer.Close()
	}
}

func (s *service) handlePaymentStatusUpdated(ctx context.Context, msg *model.PaymentStatusUpdated) error {
	start := time.Now()
	result := ingestResultOK

	defer func() {
		if s.deps.Observer != nil {
			s.deps.Observer.ObserveIngest(result, time.Since(start))
		}
	}()

	if msg == nil {
		result = ingestResultEmptyPayload
		return nil
	}
	if strings.TrimSpace(msg.EventID) == "" || msg.Data.OrganizationRef == bson.NilObjectID || msg.OccurredAt.IsZero() {
		result = ingestResultInvalidEvent
		return nil
	}

	eventType := strings.TrimSpace(msg.Type)
	if eventType == "" {
		eventType = model.PaymentStatusUpdatedType
	}

	data, err := json.Marshal(msg.Data)
	if err != nil {
		result = ingestResultPayloadError
		return err
	}

	parsed := &events.Envelope{
		EventID:         strings.TrimSpace(msg.EventID),
		Type:            eventType,
		OrganizationRef: msg.Data.OrganizationRef,
		OccurredAt:      msg.OccurredAt.UTC(),
		PublishedAt:     msg.PublishedAt.UTC(),
		Data:            data,
	}

	inserted, err := s.deps.InboxRepo.TryInsert(ctx, parsed.EventID, parsed.Type, parsed.OrganizationRef, time.Now().UTC())
	if err != nil {
		result = ingestResultInboxError
		return err
	}
	if !inserted {
		result = ingestResultDuplicate
		return nil
	}

	endpoints, err := s.deps.Resolver.Resolve(ctx, parsed.Type, parsed.OrganizationRef)
	if err != nil {
		result = ingestResultResolveError
		return err
	}
	if len(endpoints) == 0 {
		result = ingestResultNoEndpoints
		return nil
	}

	payload, err := s.deps.Events.BuildPayload(ctx, parsed)
	if err != nil {
		result = ingestResultPayloadError
		return err
	}

	if err := s.deps.TaskRepo.UpsertTasks(ctx, parsed.EventID, endpoints, payload, s.deps.TaskDefaults, time.Now().UTC()); err != nil {
		result = ingestResultTaskError
		return err
	}

	return nil
}