// Copyright 2018 The Netstack Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package channel provides the implemention of channel-based data-link layer
// endpoints. Such endpoints allow injection of inbound packets and store
// outbound packets in a channel.
package bufwritingchannel

import (
	"github.com/google/netstack/tcpip"
	"github.com/google/netstack/tcpip/buffer"
	"github.com/google/netstack/tcpip/link/channel"
	"github.com/google/netstack/tcpip/stack"
)

// Endpoint is link layer endpoint that stores outbound packets in a channel
// and allows injection of inbound packets.
type Endpoint struct {
	channel.Endpoint
}

// New creates a new channel endpoint.
func New(size int, mtu uint32, linkAddr tcpip.LinkAddress) (tcpip.LinkEndpointID, *Endpoint) {
	_, ce := channel.New(size, mtu, linkAddr)

	e := &Endpoint{
		Endpoint: *ce,
	}

	return stack.RegisterLinkEndpoint(e), e
}

func (e *Endpoint) WriteBuffer(_ *stack.Route, payload *buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
	p := channel.PacketInfo{
		Proto: protocol,
	}

	if payload != nil {
		p.Payload = payload.ToView()
	}

	select {
	case e.C <- p:
	default:
	}

	return nil
}