// Copyright © 2021 Ettore Di Giacinto <mudler@mocaccino.org>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, see <http://www.gnu.org/licenses/>.

package node

import (
	"context"
	"time"

	"github.com/ipfs/go-log"
	"github.com/libp2p/go-libp2p"
	"github.com/libp2p/go-libp2p-core/host"
	"github.com/libp2p/go-libp2p-core/network"

	protocol "github.com/mudler/edgevpn/pkg/protocol"

	pubsub "github.com/libp2p/go-libp2p-pubsub"
	"github.com/mudler/edgevpn/pkg/blockchain"
	hub "github.com/mudler/edgevpn/pkg/hub"
	"github.com/mudler/edgevpn/pkg/logger"
)

type Node struct {
	config  Config
	HubRoom *hub.Room
	inputCh chan *hub.Message
	seed    int64
	host    host.Host

	ledger *blockchain.Ledger
}

var defaultLibp2pOptions = []libp2p.Option{
	libp2p.EnableNATService(),
	libp2p.NATPortMap(),
	libp2p.EnableAutoRelay(),
}

func New(p ...Option) *Node {
	c := Config{
		DiscoveryInterval:        120 * time.Second,
		StreamHandlers:           make(map[protocol.Protocol]StreamHandler),
		LedgerAnnounceTime:       5 * time.Second,
		LedgerSyncronizationTime: 5 * time.Second,
		SealKeyLength:            12,
		Options:                  defaultLibp2pOptions,
		Logger:                   logger.New(log.LevelDebug),
	}
	c.Apply(p...)

	return &Node{
		config:  c,
		inputCh: make(chan *hub.Message, 3000),
		seed:    0,
	}
}

// Ledger return the ledger which uses the node
// connection to broadcast messages
func (e *Node) Ledger() (*blockchain.Ledger, error) {
	if e.ledger != nil {
		return e.ledger, nil
	}

	mw, err := e.messageWriter()
	if err != nil {
		return nil, err
	}

	e.ledger = blockchain.New(mw, e.config.Store)
	return e.ledger, nil
}

// Start joins the node over the p2p network
func (e *Node) Start(ctx context.Context) error {

	ledger, err := e.Ledger()
	if err != nil {
		return err
	}

	// Set the handler when we receive messages
	// The ledger needs to read them and update the internal blockchain
	e.config.Handlers = append(e.config.Handlers, ledger.Update)

	e.config.Logger.Info("Starting EdgeVPN network")

	// Startup libp2p network
	err = e.startNetwork(ctx)
	if err != nil {
		return err
	}

	// Send periodically messages to the channel with our blockchain content
	ledger.Syncronizer(ctx, e.config.LedgerSyncronizationTime)

	// Start eventual declared NetworkServices
	for _, s := range e.config.NetworkServices {
		s(ctx, e.config, e, ledger)
	}

	return nil
}

// messageWriter returns a new MessageWriter bound to the edgevpn instance
// with the given options
func (e *Node) messageWriter(opts ...hub.MessageOption) (*messageWriter, error) {
	mess := &hub.Message{}
	mess.Apply(opts...)

	return &messageWriter{
		c:     e.config,
		input: e.inputCh,
		mess:  mess,
	}, nil
}

func (e *Node) startNetwork(ctx context.Context) error {
	e.config.Logger.Debug("Generating host data")

	host, err := e.genHost(ctx)
	if err != nil {
		e.config.Logger.Error(err.Error())
		return err
	}
	e.host = host

	ledger, err := e.Ledger()
	if err != nil {
		return err
	}

	for pid, strh := range e.config.StreamHandlers {
		host.SetStreamHandler(pid.ID(), network.StreamHandler(strh(e, ledger)))
	}

	e.config.Logger.Info("Node ID:", host.ID())
	e.config.Logger.Info("Node Addresses:", host.Addrs())

	// create a new PubSub service using the GossipSub router
	ps, err := pubsub.NewGossipSub(ctx, host, pubsub.WithMaxMessageSize(e.config.MaxMessageSize))
	if err != nil {
		return err
	}

	// join the "chat" room
	cr, err := hub.JoinRoom(ctx, ps, host.ID(), e.config.RoomName)
	if err != nil {
		return err
	}

	e.HubRoom = cr

	for _, sd := range e.config.ServiceDiscovery {
		if err := sd.Run(e.config.Logger, ctx, host); err != nil {
			e.config.Logger.Fatal(err)
		}
	}

	go e.handleEvents(ctx)

	e.config.Logger.Debug("Network started")
	return nil
}