package kubemq

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

	"github.com/kubemq-io/kubemq-go"

	"github.com/dapr/components-contrib/pubsub"
	"github.com/dapr/kit/logger"
)

// interface used to allow unit testing.
type kubemqEventsStoreClient interface {
	Stream(ctx context.Context, onResult func(result *kubemq.EventStoreResult, err error)) (func(msg *kubemq.EventStore) error, error)
	Subscribe(ctx context.Context, request *kubemq.EventsStoreSubscription, onEvent func(msg *kubemq.EventStoreReceive, err error)) error
	Close() error
}

type kubeMQEventStore struct {
	lock                 sync.RWMutex
	client               kubemqEventsStoreClient
	metadata             *kubemqMetadata
	logger               logger.Logger
	publishFunc          func(msg *kubemq.EventStore) error
	resultChan           chan *kubemq.EventStoreResult
	waitForResultTimeout time.Duration
	ctx                  context.Context
	ctxCancel            context.CancelFunc
	isInitialized        bool
}

func newKubeMQEventsStore(logger logger.Logger) *kubeMQEventStore {
	return &kubeMQEventStore{
		client:               nil,
		metadata:             nil,
		logger:               logger,
		publishFunc:          nil,
		resultChan:           make(chan *kubemq.EventStoreResult, 1),
		waitForResultTimeout: 10 * time.Second,
		ctx:                  nil,
		ctxCancel:            nil,
		isInitialized:        false,
	}
}

func (k *kubeMQEventStore) init() error {
	k.lock.RLock()
	isInit := k.isInitialized
	k.lock.RUnlock()
	if isInit {
		return nil
	}
	k.lock.Lock()
	defer k.lock.Unlock()
	k.ctx, k.ctxCancel = context.WithCancel(context.Background())
	clientID := k.metadata.ClientID
	if clientID == "" {
		clientID = getRandomID()
	}
	client, err := kubemq.NewEventsStoreClient(k.ctx,
		kubemq.WithAddress(k.metadata.internalHost, k.metadata.internalPort),
		kubemq.WithClientId(clientID),
		kubemq.WithTransportType(kubemq.TransportTypeGRPC),
		kubemq.WithCheckConnection(true),
		kubemq.WithAuthToken(k.metadata.AuthToken),
		kubemq.WithAutoReconnect(true),
		kubemq.WithReconnectInterval(time.Second))
	if err != nil {
		k.logger.Errorf("error init kubemq client error: %s", err.Error())
		return err
	}
	k.ctx, k.ctxCancel = context.WithCancel(context.Background())
	k.client = client
	if err := k.setPublishStream(); err != nil {
		k.logger.Errorf("error init kubemq client error: %w", err.Error())
		return err
	}
	k.isInitialized = true
	return nil
}

func (k *kubeMQEventStore) Init(meta *kubemqMetadata) error {
	k.metadata = meta
	_ = k.init()
	return nil
}

func (k *kubeMQEventStore) setPublishStream() error {
	var err error
	k.publishFunc, err = k.client.Stream(k.ctx, func(result *kubemq.EventStoreResult, err error) {
		select {
		case k.resultChan <- result:
		default:
		}
	})
	if err != nil {
		return err
	}
	return nil
}

func (k *kubeMQEventStore) Publish(req *pubsub.PublishRequest) error {
	if err := k.init(); err != nil {
		return err
	}
	if req.Topic == "" {
		return errors.New("kubemq pub/sub error: topic is required")
	}
	k.logger.Debugf("kubemq pub/sub: publishing message to %s", req.Topic)
	metadata := ""
	if req.Metadata != nil {
		data, err := json.Marshal(req.Metadata)
		if err != nil {
			return fmt.Errorf("kubemq pub/sub error: failed to marshal metadata: %s", err.Error())
		}
		metadata = string(data)
	}
	contentType := ""
	if req.ContentType != nil {
		contentType = *req.ContentType
	}
	event := &kubemq.EventStore{
		Id:       "",
		Channel:  req.Topic,
		Metadata: metadata,
		Body:     req.Data,
		ClientId: k.metadata.ClientID,
		Tags: map[string]string{
			"ContentType": contentType,
		},
	}
	if err := k.publishFunc(event); err != nil {
		k.logger.Errorf("kubemq pub/sub error: publishing to %s failed with error: %s", req.Topic, err.Error())
		return err
	}
	select {
	case res := <-k.resultChan:
		if res != nil && res.Err != nil {
			return res.Err
		}
	case <-time.After(k.waitForResultTimeout):
		return errors.New("kubemq pub/sub error: timeout waiting for response")
	}
	return nil
}

func (k *kubeMQEventStore) Features() []pubsub.Feature {
	return nil
}

func (k *kubeMQEventStore) Subscribe(ctx context.Context, req pubsub.SubscribeRequest, handler pubsub.Handler) error {
	if err := k.init(); err != nil {
		return err
	}
	clientID := k.metadata.ClientID
	if clientID == "" {
		clientID = getRandomID()
	}
	k.logger.Debugf("kubemq pub/sub: subscribing to %s", req.Topic)
	err := k.client.Subscribe(ctx, &kubemq.EventsStoreSubscription{
		Channel:          req.Topic,
		Group:            k.metadata.Group,
		ClientId:         clientID,
		SubscriptionType: kubemq.StartFromNewEvents(),
	}, func(event *kubemq.EventStoreReceive, err error) {
		if err != nil {
			k.logger.Errorf("kubemq pub/sub error: subscribing to %s failed with error: %s", req.Topic, err.Error())
			return
		}
		if ctx.Err() != nil {
			return
		}
		var metadata map[string]string
		if event.Metadata != "" {
			_ = json.Unmarshal([]byte(event.Metadata), &metadata)
		}
		var contentType *string
		if event.Tags != nil {
			if event.Tags["ContentType"] != "" {
				*contentType = event.Tags["ContentType"]
			}
		}
		msg := &pubsub.NewMessage{
			Data:        event.Body,
			Topic:       req.Topic,
			Metadata:    metadata,
			ContentType: contentType,
		}
		if err := handler(ctx, msg); err != nil {
			k.logger.Errorf("kubemq pub/sub error: error handling message from topic '%s', %s, resending...", req.Topic, err.Error())
			if k.metadata.DisableReDelivery {
				return
			}
			if err := k.Publish(&pubsub.PublishRequest{
				Data:  msg.Data,
				Topic: msg.Topic,
			}); err != nil {
				k.logger.Errorf("kubemq pub/sub error: error resending message from topic '%s', %s", req.Topic, err.Error())
			}
		}
	})
	if err != nil {
		k.logger.Errorf("kubemq pub/sub error: error subscribing to topic '%s', %s", req.Topic, err.Error())
		return err
	}
	time.Sleep(1 * time.Second)
	k.logger.Debugf("kubemq pub/sub: subscribed to %s completed", req.Topic)
	return nil
}

func (k *kubeMQEventStore) Close() error {
	if k.ctxCancel != nil {
		k.ctxCancel()
	}
	if k.client == nil {
		return nil
	}
	return k.client.Close()
}