package control

import (
	"context"
	"encoding/json"

	"github.com/pkg/errors"
	"github.com/xtaci/smux"
	"gitlab.com/wpetit/goweb/logger"
)

type Control struct {
	encoder *json.Encoder
	decoder *json.Decoder
	stream  *smux.Stream
}

func (c *Control) Init(ctx context.Context, sess *smux.Session, serverMode bool) error {
	config := smux.DefaultConfig()
	config.Version = 2

	logger.Debug(ctx, "creating control stream")

	var (
		stream *smux.Stream
		err    error
	)

	if serverMode {
		stream, err = sess.AcceptStream()
		if err != nil {
			return errors.WithStack(err)
		}
	} else {
		stream, err = sess.OpenStream()
		if err != nil {
			return errors.WithStack(err)
		}
	}

	c.stream = stream
	c.decoder = json.NewDecoder(stream)
	c.encoder = json.NewEncoder(stream)

	return nil
}

func (c *Control) AuthRequest(credentials interface{}) (bool, error) {
	req := NewMessage(TypeAuthRequest, &AuthRequestPayload{
		Credentials: credentials,
	})

	res := NewMessage(TypeAuthResponse, nil)

	if err := c.reqRes(req, res); err != nil {
		return false, errors.WithStack(err)
	}

	authResPayload, ok := res.Payload.(*AuthResponsePayload)
	if !ok {
		return false, errors.WithStack(ErrUnexpectedMessage)
	}

	return authResPayload.Success, nil
}

func (c *Control) ProxyReq(ctx context.Context, network, address string) error {
	req := NewMessage(TypeProxyRequest, &ProxyRequestPayload{
		Network: network,
		Address: address,
	})

	if err := c.Write(req); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (c *Control) Listen(ctx context.Context, handlers Handlers) error {
	errChan := make(chan error)
	msgChan := make(chan *Message)
	dieChan := c.stream.GetDieCh()

	go func(msgChan chan *Message, errChan chan error) {
		for {
			logger.Debug(ctx, "reading next message")

			msg, err := c.Read()
			if err != nil {
				errChan <- errors.WithStack(err)

				close(errChan)
				close(msgChan)

				return
			}

			msgChan <- msg
		}
	}(msgChan, errChan)

	for {
		select {
		case <-ctx.Done():
			return nil

		case <-dieChan:
			return errors.WithStack(ErrStreamClosed)

		case err := <-errChan:
			return errors.WithStack(err)

		case msg := <-msgChan:
			go func() {
				subCtx := logger.With(ctx, logger.F("messageType", msg.Type))

				handler, exists := handlers[msg.Type]
				if !exists {
					logger.Error(subCtx, "no message handler registered")

					return
				}

				res, err := handler(subCtx, msg)
				if err != nil {
					logger.Error(subCtx, "error while handling message", logger.E(err))

					return
				}

				if res == nil {
					return
				}

				if err := c.Write(res); err != nil {
					logger.Error(subCtx, "error while write message response", logger.E(err))

					return
				}
			}()
		}
	}
}

func (c *Control) Read() (*Message, error) {
	message := &Message{}

	if err := c.read(message); err != nil {
		return nil, errors.WithStack(err)
	}

	return message, nil
}

func (c *Control) Write(m *Message) error {
	if err := c.write(m); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (c *Control) reqRes(req *Message, res *Message) error {
	if err := c.write(req); err != nil {
		return errors.WithStack(err)
	}

	if err := c.read(res); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (c *Control) read(m *Message) error {
	if err := c.decoder.Decode(m); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (c *Control) write(m *Message) error {
	if err := c.encoder.Encode(m); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func New() *Control {
	return &Control{}
}