package message

import (
	"bytes"
	"fmt"
	"io"

	"v.io/core/veyron/runtimes/google/ipc/stream/id"
	"v.io/core/veyron/runtimes/google/ipc/version"
	inaming "v.io/core/veyron/runtimes/google/naming"
	"v.io/core/veyron2/naming"
)

// Control is the interface implemented by all control messages.
type Control interface {
	readFrom(r *bytes.Buffer) error
	writeTo(w io.Writer) error
}

// OpenVC is a Control implementation requesting the creation of a new virtual
// circuit.
type OpenVC struct {
	VCI         id.VC
	DstEndpoint naming.Endpoint
	SrcEndpoint naming.Endpoint
	Counters    Counters
}

// CloseVC is a Control implementation notifying the closure of an established
// virtual circuit.
// The Error string will be empty in case the close was the result of an
// explicit close by the application (and not an error).
type CloseVC struct {
	VCI   id.VC
	Error string
}

// AddReceiveBuffers is a Control implementation used by the sender of the
// message to inform the other end of a virtual circuit that it is ready to
// receive more bytes of data (specified per flow).
type AddReceiveBuffers struct {
	Counters Counters
}

// OpenFlow is a Control implementation notifying the senders intent to create
// a new Flow. It also include the number of bytes the sender of this message
// is willing to read.
type OpenFlow struct {
	VCI             id.VC
	Flow            id.Flow
	InitialCounters uint32
}

// HopSetup is a control message used to negotiate VIF options on a
// hop-by-hop basis.
type HopSetup struct {
	Versions version.Range
	Options  []HopSetupOption
}

// HopSetupOption is the base interface for optional HopSetup options.
type HopSetupOption interface {
	// code is the identifier for the option.
	code() hopSetupOptionCode

	// size returns the number of bytes needed to represent the option.
	size() uint16

	// write the option to the writer.
	write(w io.Writer) error

	// read the option from the reader.
	read(r io.Reader) error
}

// NaclBox is a HopSetupOption that specifies the public key for the NaclBox
// encryption protocol.
type NaclBox struct {
	PublicKey [32]byte
}

// HopSetupStream is a byte stream used to negotiate VIF setup.  During VIF setup,
// each party sends a HopSetup message to the other party containing their version
// and options.  If the version requires further negotiation (such as for authentication),
// the HopSetupStream is used for the negotiation.
//
// The protocol used on the stream is version-specific, it is not specified here.  See
// vif/auth.go for an example.
type HopSetupStream struct {
	Data []byte
}

// Setup option codes.
type hopSetupOptionCode uint16

const (
	naclBoxPublicKey hopSetupOptionCode = 0
)

// Command enum.
type command uint8

const (
	openVCCommand            command = 0
	closeVCCommand           command = 1
	addReceiveBuffersCommand command = 2
	openFlowCommand          command = 3
	hopSetupCommand          command = 4
	hopSetupStreamCommand    command = 5
)

func writeControl(w io.Writer, m Control) error {
	var command command
	switch m.(type) {
	case *OpenVC:
		command = openVCCommand
	case *CloseVC:
		command = closeVCCommand
	case *AddReceiveBuffers:
		command = addReceiveBuffersCommand
	case *OpenFlow:
		command = openFlowCommand
	case *HopSetup:
		command = hopSetupCommand
	case *HopSetupStream:
		command = hopSetupStreamCommand
	default:
		return fmt.Errorf("unrecognized VC control message: %T", m)
	}
	var header [1]byte
	header[0] = byte(command)
	if n, err := w.Write(header[:]); n != len(header) || err != nil {
		return fmt.Errorf("failed to write header. Got (%d, %v) want (%d, nil)", n, err, len(header))
	}
	if err := m.writeTo(w); err != nil {
		return err
	}
	return nil
}

func readControl(r *bytes.Buffer) (Control, error) {
	var header byte
	var err error
	if header, err = r.ReadByte(); err != nil {
		return nil, fmt.Errorf("message too small, cannot read control message command (0, %v)", err)
	}
	command := command(header)
	var m Control
	switch command {
	case openVCCommand:
		m = new(OpenVC)
	case closeVCCommand:
		m = new(CloseVC)
	case addReceiveBuffersCommand:
		m = new(AddReceiveBuffers)
	case openFlowCommand:
		m = new(OpenFlow)
	case hopSetupCommand:
		m = new(HopSetup)
	case hopSetupStreamCommand:
		m = new(HopSetupStream)
	default:
		return nil, fmt.Errorf("unrecognized VC control message command(%d)", command)
	}
	if err := m.readFrom(r); err != nil {
		return nil, fmt.Errorf("failed to deserialize control message %d(%T): %v", command, m, err)
	}
	return m, nil
}

func (m *OpenVC) writeTo(w io.Writer) (err error) {
	if err = writeInt(w, m.VCI); err != nil {
		return
	}
	if err = writeString(w, m.DstEndpoint.String()); err != nil {
		return
	}
	if err = writeString(w, m.SrcEndpoint.String()); err != nil {
		return
	}
	if err = writeCounters(w, m.Counters); err != nil {
		return
	}
	return nil
}

func (m *OpenVC) readFrom(r *bytes.Buffer) (err error) {
	if err = readInt(r, &m.VCI); err != nil {
		return
	}
	var ep string
	if err = readString(r, &ep); err != nil {
		return
	}
	if m.DstEndpoint, err = inaming.NewEndpoint(ep); err != nil {
		return
	}
	if err = readString(r, &ep); err != nil {
		return
	}
	if m.SrcEndpoint, err = inaming.NewEndpoint(ep); err != nil {
		return
	}
	if m.Counters, err = readCounters(r); err != nil {
		return
	}
	return nil
}

func (m *CloseVC) writeTo(w io.Writer) (err error) {
	if err = writeInt(w, m.VCI); err != nil {
		return
	}
	if err = writeString(w, m.Error); err != nil {
		return
	}
	return
}

func (m *CloseVC) readFrom(r *bytes.Buffer) (err error) {
	if err = readInt(r, &m.VCI); err != nil {
		return
	}
	if err = readString(r, &m.Error); err != nil {
		return
	}
	return
}

func (m *AddReceiveBuffers) writeTo(w io.Writer) error {
	return writeCounters(w, m.Counters)
}

func (m *AddReceiveBuffers) readFrom(r *bytes.Buffer) (err error) {
	m.Counters, err = readCounters(r)
	return
}

func (m *OpenFlow) writeTo(w io.Writer) (err error) {
	if err = writeInt(w, m.VCI); err != nil {
		return
	}
	if err = writeInt(w, m.Flow); err != nil {
		return
	}
	if err = writeInt(w, m.InitialCounters); err != nil {
		return
	}
	return
}

func (m *OpenFlow) readFrom(r *bytes.Buffer) (err error) {
	if err = readInt(r, &m.VCI); err != nil {
		return
	}
	if err = readInt(r, &m.Flow); err != nil {
		return
	}
	if err = readInt(r, &m.InitialCounters); err != nil {
		return
	}
	return
}

func (m *HopSetup) writeTo(w io.Writer) error {
	if err := writeInt(w, m.Versions.Min); err != nil {
		return err
	}
	if err := writeInt(w, m.Versions.Max); err != nil {
		return err
	}
	for _, opt := range m.Options {
		if err := writeInt(w, opt.code()); err != nil {
			return err
		}
		if err := writeInt(w, opt.size()); err != nil {
			return err
		}
		if err := opt.write(w); err != nil {
			return err
		}
	}
	return nil
}

func (m *HopSetup) readFrom(r *bytes.Buffer) error {
	if err := readInt(r, &m.Versions.Min); err != nil {
		return err
	}
	if err := readInt(r, &m.Versions.Max); err != nil {
		return err
	}
	for {
		var code hopSetupOptionCode
		err := readInt(r, &code)
		if err == io.EOF {
			return nil
		}
		if err != nil {
			return err
		}

		var size uint16
		if err := readInt(r, &size); err != nil {
			return err
		}
		l := &io.LimitedReader{R: r, N: int64(size)}

		switch code {
		case naclBoxPublicKey:
			var opt NaclBox
			if err := opt.read(l); err != nil {
				return err
			}
			m.Options = append(m.Options, &opt)
		}

		// Consume any data remaining.
		readAndDiscardToError(l)
	}
}

// NaclBox returns the first NaclBox option, or nil if there is none.
func (m *HopSetup) NaclBox() *NaclBox {
	for _, opt := range m.Options {
		if b, ok := opt.(*NaclBox); ok {
			return b
		}
	}
	return nil
}

func (*NaclBox) code() hopSetupOptionCode {
	return naclBoxPublicKey
}

func (m *NaclBox) size() uint16 {
	return uint16(len(m.PublicKey))
}

func (m *NaclBox) write(w io.Writer) error {
	_, err := w.Write(m.PublicKey[:])
	return err
}

func (m *NaclBox) read(r io.Reader) error {
	_, err := io.ReadFull(r, m.PublicKey[:])
	return err
}

func (m *HopSetupStream) writeTo(w io.Writer) error {
	_, err := w.Write(m.Data)
	return err
}

func (m *HopSetupStream) readFrom(r *bytes.Buffer) error {
	m.Data = r.Bytes()
	return nil
}