package client

import (
	"context"
	"io"
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/api/rpc/common"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/api/rpc/message"
	"google.golang.org/grpc"
)

// MessageReader is an interface of the Message reader.
type MessageReader interface {
	// ReadMessage reads the next Message.
	//
	// Returns io.EOF if there are no more messages to read.
	// ReadMessage should not be called after io.EOF occasion.
	ReadMessage(message.Message) error
}

// MessageWriter is an interface of the Message writer.
type MessageWriter interface {
	// WriteMessage writers the next Message.
	//
	// WriteMessage should not be called after any error.
	WriteMessage(message.Message) error
}

// MessageReadWriter is a component interface
// for transmitting raw Protobuf messages.
type MessageReadWriter interface {
	MessageReader
	MessageWriter

	// Closes the communication session.
	//
	// All calls to send/receive messages must be done before closing.
	io.Closer
}

// Init initiates a messaging session and returns the interface for message transmitting.
func (c *Client) Init(info common.CallMethodInfo, opts ...CallOption) (MessageReadWriter, error) {
	prm := defaultCallParameters()

	for _, opt := range opts {
		opt(prm)
	}

	if err := c.openGRPCConn(prm.ctx, prm.dialer); err != nil {
		return nil, err
	}

	ctx, cancel := context.WithCancel(prm.ctx)

	// `conn.NewStream` doesn't check if `conn` may turn up invalidated right before this invocation.
	// In such cases, the operation can hang indefinitely, with the context timeout being the only
	// mechanism to cancel it.
	//
	// We use a separate timer instead of context timeout because the latter
	// would propagate to all subsequent read/write operations on the opened stream,
	// which is not desired for the stream's lifecycle management.
	dialTimeoutTimer := time.NewTimer(c.dialTimeout)
	defer dialTimeoutTimer.Stop()

	type newStreamRes struct {
		stream grpc.ClientStream
		err    error
	}
	newStreamCh := make(chan newStreamRes)

	go func() {
		stream, err := c.conn.NewStream(ctx, &grpc.StreamDesc{
			StreamName:    info.Name,
			ServerStreams: info.ServerStream(),
			ClientStreams: info.ClientStream(),
		}, toMethodName(info))

		newStreamCh <- newStreamRes{
			stream: stream,
			err:    err,
		}
	}()

	var res newStreamRes

	select {
	case <-dialTimeoutTimer.C:
		cancel()
		res = <-newStreamCh
		if res.stream != nil && res.err == nil {
			_ = res.stream.CloseSend()
		}
		return nil, context.Canceled
	case res = <-newStreamCh:
	}

	if res.err != nil {
		cancel()
		return nil, res.err
	}

	return &streamWrapper{
		ClientStream: res.stream,
		cancel:       cancel,
		timeout:      c.rwTimeout,
	}, nil
}