handler.go

/*
	Copyright NetFoundry Inc.

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	https://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
*/

package channel

import (
	"crypto/x509"
)

// Binding is used to add handlers to Channel.
//
// NOTE: It is intended that the Add* methods are used at initial channel setup, and not invoked on an in-service
// Channel. The Binding should not be retained once the channel setup is complete
type Binding interface {
	Bind(h BindHandler) error
	AddPeekHandler(h PeekHandler)
	AddTransformHandler(h TransformHandler)
	AddReceiveHandler(contentType int32, h ReceiveHandler)
	AddReceiveHandlerF(contentType int32, h ReceiveHandlerF)
	AddTypedReceiveHandler(h TypedReceiveHandler)
	AddErrorHandler(h ErrorHandler)
	AddCloseHandler(h CloseHandler)
	SetUserData(data interface{})
	GetUserData() interface{}
	GetChannel() Channel
}

type BindHandler interface {
	BindChannel(binding Binding) error
}

type BindHandlerF func(binding Binding) error

func (f BindHandlerF) BindChannel(binding Binding) error {
	return f(binding)
}

// BindHandlers takes the given handlers and returns a BindHandler which
// runs the handlers one at a time, returning an error as soon as
// an error is encountered, or nil, if no errors are encountered.
func BindHandlers(handlers ...BindHandler) BindHandler {
	if len(handlers) == 1 {
		return handlers[0]
	}

	return BindHandlerF(func(binding Binding) error {
		for _, handler := range handlers {
			if handler != nil {
				if err := handler.BindChannel(binding); err != nil {
					return err
				}
			}
		}
		return nil
	})
}

type ConnectionHandler interface {
	HandleConnection(hello *Hello, certificates []*x509.Certificate) error
}

type PeekHandler interface {
	Connect(ch Channel, remoteAddress string)
	Rx(m *Message, ch Channel)
	Tx(m *Message, ch Channel)
	Close(ch Channel)
}

type TransformHandler interface {
	Rx(m *Message, ch Channel)
	Tx(m *Message, ch Channel)
}

type ReceiveHandler interface {
	HandleReceive(m *Message, ch Channel)
}

type TypedReceiveHandler interface {
	ContentType() int32
	ReceiveHandler
}

type ReceiveHandlerF func(m *Message, ch Channel)

func (self ReceiveHandlerF) HandleReceive(m *Message, ch Channel) {
	self(m, ch)
}

type AsyncFunctionReceiveAdapter struct {
	Type    int32
	Handler ReceiveHandlerF
}

func (adapter *AsyncFunctionReceiveAdapter) ContentType() int32 {
	return adapter.Type
}

func (adapter *AsyncFunctionReceiveAdapter) HandleReceive(m *Message, ch Channel) {
	go adapter.Handler(m, ch)
}

type ErrorHandler interface {
	HandleError(err error, ch Channel)
}

type ErrorHandlerF func(err error, ch Channel)

func (self ErrorHandlerF) HandleError(err error, ch Channel) {
	self(err, ch)
}

type CloseHandler interface {
	HandleClose(ch Channel)
}

type CloseHandlerF func(ch Channel)

func (self CloseHandlerF) HandleClose(ch Channel) {
	self(ch)
}

type MessageSourceF func(notifer *CloseNotifier) (Sendable, error)

type UnderlayHandler interface {
	// ChannelCreated is called after the MultiChannel has been created but before binding happens.
	// This allows the underlay handler to set the channel, if desired, before binding happens
	ChannelCreated(channel MultiChannel)

	// Start is called after the MultiChannel has been created with the first underlay and binding is complete.
	// If this is a dial side, Start may be used to add additional underlays
	Start(channel MultiChannel)

	// GetMessageSource returns the message source for the given underlay. In general this will
	// check the type in the underlay headers and use that to figure out which go channels
	// to read from
	GetMessageSource(underlay Underlay) MessageSourceF

	// HandleTxFailed is called when an underlay write fails. This allows the message to
	// be re-queued if the channel semantic allow.
	HandleTxFailed(underlay Underlay, sendable Sendable) bool

	// HandleUnderlayClose is called when an underlay closes. This may cause the multi channel to be
	// closed if it no longer has enough underlays to meet its requirements, or may intitiate
	// dialing addition underlays
	HandleUnderlayClose(channel MultiChannel, underlay Underlay)

	// HandleUnderlayAccepted is call when an underlay is added to the multi-underlay channel
	HandleUnderlayAccepted(channel MultiChannel, underlay Underlay)

	// GetDefaultSender returns the default sender for the underlay
	GetDefaultSender() Sender

	// GetCloseNotify returns the chan used to signal that the channel is closed
	GetCloseNotify() chan struct{}
}