package network

import (
	"context"
	"errors"
	"git.hpds.cc/Component/network/id"
	"time"

	"git.hpds.cc/Component/network/frame"
	"git.hpds.cc/Component/network/log"
)

// ClientOption client options
type ClientOption func(*clientOptions)

// Client is the abstraction of a HPDS-Client. a HPDS-Client can be
// Protocol Gateway, Message Queue or StreamFunction.
type Client struct {
	name       string                     // name of the client
	clientId   string                     // id of the client
	streamType StreamType                 // type of the dataStream
	processor  func(*frame.DataFrame)     // function to invoke when data arrived
	receiver   func(*frame.BackFlowFrame) // function to invoke when data is processed
	errorfn    func(error)                // function to invoke when error occured
	opts       *clientOptions

	// ctx and ctxCancel manage the lifecycle of client.
	ctx       context.Context
	ctxCancel context.CancelFunc

	writeFrameChan chan frame.Frame
	shutdownChan   chan error
}

// NewClient creates a new HPDS-Client.
func NewClient(appName string, connType ClientType, opts ...ClientOption) *Client {
	option := defaultClientOption()

	for _, o := range opts {
		o(option)
	}
	clientId := id.New()

	if option.credential != nil {
		log.Infof("use credential, credential_name: %s;", option.credential.Name())
	}

	ctx, ctxCancel := context.WithCancel(context.Background())

	return &Client{
		name:           appName,
		clientId:       clientId,
		streamType:     connType,
		opts:           option,
		errorfn:        func(err error) { log.Errorf("client err, %s", err) },
		writeFrameChan: make(chan frame.Frame),
		shutdownChan:   make(chan error, 1),
		ctx:            ctx,
		ctxCancel:      ctxCancel,
	}
}

// Connect connects to HPDS-MessageQueue.
func (c *Client) Connect(ctx context.Context, addr string) error {
	controlStream, dataStream, err := c.openStream(ctx, addr)
	if err != nil {
		log.Errorf("connect error, %s", err)
		return err
	}

	go c.runBackground(ctx, addr, controlStream, dataStream)

	return nil
}

func (c *Client) runBackground(ctx context.Context, addr string, controlStream ClientControlStream, dataStream DataStream) {
	reconnection := make(chan struct{})

	go c.processStream(controlStream, dataStream, reconnection)

	for {
		select {
		case <-c.ctx.Done():
			c.cleanStream(controlStream, nil)
			return
		case <-ctx.Done():
			c.cleanStream(controlStream, ctx.Err())
			return
		case <-reconnection:
		RECONNECT:
			var err error
			controlStream, dataStream, err = c.openStream(ctx, addr)
			if err != nil {
				log.Errorf("client reconnect error, %s", err)
				time.Sleep(time.Second)
				goto RECONNECT
			}
			go c.processStream(controlStream, dataStream, reconnection)
		}
	}
}

// WriteFrame write frame to client.
func (c *Client) WriteFrame(f frame.Frame) error {
	c.writeFrameChan <- f
	return nil
}

func (c *Client) cleanStream(controlStream ClientControlStream, err error) {
	errString := ""
	if err != nil {
		errString = err.Error()
		log.Errorf("client cancel with error, %s", err)
	}

	// controlStream is nil represents that client is not connected.
	if controlStream == nil {
		return
	}

	_ = controlStream.CloseWithError(0, errString)
}

// Close the client.
func (c *Client) Close() error {
	// break runBackgroud() for-loop.
	c.ctxCancel()

	// non-blocking to return Wait().
	select {
	case c.shutdownChan <- nil:
	default:
	}

	return nil
}

func (c *Client) openControlStream(ctx context.Context, addr string) (ClientControlStream, error) {
	controlStream, err := OpenClientControlStream(ctx, addr, c.opts.tlsConfig, c.opts.quicConfig)
	if err != nil {
		return nil, err
	}

	if err := controlStream.Authenticate(c.opts.credential); err != nil {
		return nil, err
	}

	return controlStream, nil
}

func (c *Client) openStream(ctx context.Context, addr string) (ClientControlStream, DataStream, error) {
	controlStream, err := c.openControlStream(ctx, addr)
	if err != nil {
		return nil, nil, err
	}
	dataStream, err := c.openDataStream(ctx, controlStream)
	if err != nil {
		return nil, nil, err
	}

	return controlStream, dataStream, nil
}

func (c *Client) openDataStream(ctx context.Context, controlStream ClientControlStream) (DataStream, error) {
	handshakeFrame := frame.NewHandshakeFrame(
		c.name,
		c.clientId,
		byte(c.streamType),
		c.opts.observeDataTags,
		[]byte{}, // The stream does not require metadata currently.
	)
	dataStream, err := controlStream.OpenStream(ctx, handshakeFrame)
	if err != nil {
		return nil, err
	}

	return dataStream, nil
}

func (c *Client) processStream(controlStream ClientControlStream, dataStream DataStream, reconnection chan<- struct{}) {
	defer func() {
		_ = dataStream.Close()
	}()

	var (
		controlStreamErrChan = c.receivingStreamClose(controlStream, dataStream)
		readFrameChan        = c.readFrame(dataStream)
	)
	for {
		select {
		case err := <-controlStreamErrChan:
			c.shutdownWithError(err)
		case result := <-readFrameChan:
			if err := result.err; err != nil {
				c.errorfn(err)
				reconnection <- struct{}{}
				return
			}
			c.handleFrame(result.frame)
		case f := <-c.writeFrameChan:
			err := dataStream.WriteFrame(f)
			// restore DataFrame.
			if d, ok := f.(*frame.DataFrame); ok {
				d.Clean()
			}
			if err != nil {
				c.errorfn(err)
				reconnection <- struct{}{}
				return
			}
		}
	}
}

// Wait waits client error returning.
func (c *Client) Wait() error {
	err := <-c.shutdownChan
	return err
}

func (c *Client) shutdownWithError(err error) {
	// non-blocking shutdown client.
	select {
	case c.shutdownChan <- err:
	default:
	}
}

type readResult struct {
	frame frame.Frame
	err   error
}

func (c *Client) readFrame(dataStream DataStream) chan readResult {
	readChan := make(chan readResult)
	go func() {
		for {
			f, err := dataStream.ReadFrame()
			readChan <- readResult{f, err}
			if err != nil {
				return
			}
		}
	}()

	return readChan
}

func (c *Client) handleFrame(f frame.Frame) {
	switch ff := f.(type) {
	case *frame.DataFrame:
		if c.processor == nil {
			log.Warnf("client processor has not been set")
		} else {
			c.processor(ff)
		}
	case *frame.BackFlowFrame:
		if c.receiver == nil {
			log.Warnf("client receiver has not been set")
		} else {
			c.receiver(ff)
		}
	default:
		log.Warnf("client data stream receive unexcepted frame, frame_type: %v", f)
	}
}

func (c *Client) receivingStreamClose(controlStream ControlStream, dataStream DataStream) chan error {
	closeStreamChan := make(chan error)

	go func() {
		for {
			streamID, reason, err := controlStream.ReceiveStreamClose()
			if err != nil {
				closeStreamChan <- err
				return
			}
			if streamID == c.clientId {
				c.ctxCancel()
				_ = dataStream.Close()
				closeStreamChan <- errors.New(reason)
				_ = controlStream.CloseWithError(0, reason)
				return
			}
		}
	}()

	return closeStreamChan
}

// SetDataFrameObserver sets the data frame handler.
func (c *Client) SetDataFrameObserver(fn func(*frame.DataFrame)) {
	c.processor = fn
	log.Debugf("SetDataFrameObserver")
}

// SetBackFlowFrameObserver sets the backflow frame handler.
func (c *Client) SetBackFlowFrameObserver(fn func(*frame.BackFlowFrame)) {
	c.receiver = fn
	log.Debugf("SetBackFlowFrameObserver")
}

// SetObserveDataTags set the data tag list that will be observed.
// Deprecated: use yomo.WithObserveDataTags instead
func (c *Client) SetObserveDataTags(tag ...frame.Tag) {
	c.opts.observeDataTags = append(c.opts.observeDataTags, tag...)
}

// SetErrorHandler set error handler
func (c *Client) SetErrorHandler(fn func(err error)) {
	c.errorfn = fn
}

// ClientId return the client ID
func (c *Client) ClientId() string {
	return c.clientId
}