package reader

import (
	"context"
	"sync"
	"time"

	"src.dualinventive.com/go/dinet"
	"src.dualinventive.com/go/lib/dilog"
)

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

	logger dilog.Logger
	pubsub dinet.Conn
	r      dinet.Writer
}

// New creates a new message reader
func New(logger dilog.Logger, pubSubURI string, r 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{
		logger: logger,
		pubsub: con,
		r:      r,
	}
	return reader, err
}

// AddConn connects to an additional ZMQ connection
func (r *MessageReader) AddConn(pubSubURI string) error {
	return r.pubsub.Connect(pubSubURI + "?type=sub")
}

// 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 {
			r.logger.WithError(err).Error("unable to close pub sub connection")
		}
	}()

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

		if err := r.r.Send(msg); err != nil {
			r.logger.WithError(err).Warning("Send error")
		}
	}
}

func (r *MessageReader) reconnect(ctx context.Context) {
	r.mu.Lock()
	defer r.mu.Unlock()
	// Do not reconnect when the context is closed
	if ctx.Err() != nil {
		return
	}
	// Try to reconnect
	for err := r.pubsub.Reconnect(); err != nil; err = r.pubsub.Reconnect() {
		r.logger.WithError(err).Warning("Reconnect error")
		// Do not reconnect when the context is closed
		if ctx.Err() != nil {
			return
		}

		time.Sleep(100 * time.Millisecond)
	}
}