package reader

import (
	"context"
	"sync"
	"time"

	"github.com/sirupsen/logrus"
	"src.dualinventive.com/go/dinet"
)

// MessageReader reads incomming messages from a pubsub connection and send the messages to Influx
type MessageReader struct {
	mu sync.Mutex

	pubsub dinet.Conn
	w      dinet.Writer
}

// New creates a new message reader
func New(pubSubURI string, w dinet.Writer) (*MessageReader, error) {
	con, err := dinet.NewConn(dinet.TransportZmq)
	if err != nil {
		return nil, err
	}

	err = con.Connect(pubSubURI + "?type=sub")
	if err != nil {
		return nil, err
	}

	reader := &MessageReader{}
	reader.pubsub = con
	reader.w = w

	return reader, err
}

// Serve reads incomming messages from a pubsub connection and send the messages to Redis
func (r *MessageReader) Serve(ctx context.Context) {
	var wg sync.WaitGroup
	// Wait until the goroutine ends
	defer wg.Wait()

	wg.Add(1)
	go func() {
		defer wg.Done()
		<-ctx.Done()
		r.mu.Lock()
		defer r.mu.Unlock()
		if err := r.pubsub.Close(); err != nil {
			logrus.Error("Unable to close pub sub connection:", err)
		}
	}()

	for {
		if ctx.Err() != nil {
			logrus.Infof("reader context error: %v", ctx.Err())
			return
		}
		// Receive messages from the reader connection
		msg, err := r.pubsub.Recv()
		if err != nil {
			if err == dinet.ErrDisconnected {
				logrus.Warn("Reconnecting due to error:", err)
			} else {
				logrus.Error("Unable to receive publish message due to:", err)
			}
			r.reconnect(ctx)
			continue
		}

		if err := r.w.Send(msg); err != nil {
			logrus.Warn("Send error: ", err)
		}
	}
}

func (r *MessageReader) reconnect(ctx context.Context) {
	select {
	case <-ctx.Done():
		// Do not reconnect when the context is closed
		return
	default:
	}

	r.mu.Lock()
	defer r.mu.Unlock()
	// Try to reconnect
	for err := r.pubsub.Reconnect(); err != nil; err = r.pubsub.Reconnect() {
		select {
		case <-ctx.Done():
			// Do not reconnect when the context is closed
			return
		default:
		}

		logrus.Warn("Reconnect error: ", err)
		time.Sleep(100 * time.Millisecond)
	}
}