/*
Copyright © 2021-2022 Ettore Di Giacinto <mudler@mocaccino.org>
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
    http://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 config

import (
	"fmt"
	"math/bits"
	"os"
	"runtime"
	"strings"
	"time"

	"github.com/ipfs/go-log"
	"github.com/libp2p/go-libp2p"
	dht "github.com/libp2p/go-libp2p-kad-dht"
	"github.com/libp2p/go-libp2p/core/network"
	"github.com/libp2p/go-libp2p/core/peer"
	"github.com/libp2p/go-libp2p/p2p/host/autorelay"
	rcmgr "github.com/libp2p/go-libp2p/p2p/host/resource-manager"
	mplex "github.com/libp2p/go-libp2p/p2p/muxer/mplex"
	yamux "github.com/libp2p/go-libp2p/p2p/muxer/yamux"
	connmanager "github.com/libp2p/go-libp2p/p2p/net/connmgr"
	"github.com/mudler/edgevpn/pkg/blockchain"
	"github.com/mudler/edgevpn/pkg/crypto"
	"github.com/mudler/edgevpn/pkg/discovery"
	"github.com/mudler/edgevpn/pkg/logger"
	"github.com/mudler/edgevpn/pkg/node"
	"github.com/mudler/edgevpn/pkg/trustzone"
	"github.com/mudler/edgevpn/pkg/trustzone/authprovider/ecdsa"
	"github.com/mudler/edgevpn/pkg/vpn"
	"github.com/mudler/water"
	"github.com/peterbourgon/diskv"
)

// Config is the config struct for the node and the default EdgeVPN services
// It is used to generate opts for the node and the services before start.
type Config struct {
	NetworkConfig, NetworkToken                string
	Address                                    string
	Router                                     string
	Interface                                  string
	Libp2pLogLevel, LogLevel                   string
	LowProfile, BootstrapIface                 bool
	Blacklist                                  []string
	Concurrency                                int
	FrameTimeout                               string
	ChannelBufferSize, InterfaceMTU, PacketMTU int
	NAT                                        NAT
	Connection                                 Connection
	Discovery                                  Discovery
	Ledger                                     Ledger
	Limit                                      ResourceLimit
	// PeerGuard (experimental)
	// enable peerguardian and add specific auth options
	PeerGuard PeerGuard
}

type PeerGuard struct {
	Enable      bool
	Relaxed     bool
	Autocleanup bool
	PeerGate    bool
	// AuthProviders in the freemap form:
	// ecdsa:
	//   private_key: "foo_bar"
	AuthProviders map[string]map[string]interface{}
	SyncInterval  time.Duration
}

type ResourceLimit struct {
	FileLimit   string
	LimitConfig *rcmgr.LimitConfig
	Scope       string
	MaxConns    int
	StaticMin   int64
	StaticMax   int64
	Enable      bool
}

// Ledger is the ledger configuration structure
type Ledger struct {
	AnnounceInterval, SyncInterval time.Duration
	StateDir                       string
}

// Discovery allows to enable/disable discovery and
// set bootstrap peers
type Discovery struct {
	DHT, MDNS      bool
	BootstrapPeers []string
	Interval       time.Duration
}

// Connection is the configuration section
// relative to the connection services
type Connection struct {
	HolePunch bool
	AutoRelay bool

	AutoRelayDiscoveryInterval time.Duration
	RelayV1                    bool
	StaticRelays               []string
	OnlyStaticRelays           bool

	Mplex          bool
	MaxConnections int
}

// NAT is the structure relative to NAT configuration settings
// It allows to enable/disable the service and NAT mapping, and rate limiting too.
type NAT struct {
	Service   bool
	Map       bool
	RateLimit bool

	RateLimitGlobal, RateLimitPeer int
	RateLimitInterval              time.Duration
}

// Validate returns error if the configuration is not valid
func (c Config) Validate() error {
	if c.NetworkConfig == "" &&
		c.NetworkToken == "" {
		return fmt.Errorf("EDGEVPNCONFIG or EDGEVPNTOKEN not supplied. At least a config file is required")
	}
	return nil
}

func peers2List(peers []string) discovery.AddrList {
	addrsList := discovery.AddrList{}
	for _, p := range peers {
		addrsList.Set(p)
	}
	return addrsList
}
func peers2AddrInfo(peers []string) []peer.AddrInfo {
	addrsList := []peer.AddrInfo{}
	for _, p := range peers {
		pi, err := peer.AddrInfoFromString(p)
		if err == nil {
			addrsList = append(addrsList, *pi)
		}

	}
	return addrsList
}

// ToOpts returns node and vpn options from a configuration
func (c Config) ToOpts(l *logger.Logger) ([]node.Option, []vpn.Option, error) {

	if err := c.Validate(); err != nil {
		return nil, nil, err
	}

	config := c.NetworkConfig
	address := c.Address
	router := c.Router
	iface := c.Interface
	logLevel := c.LogLevel
	libp2plogLevel := c.Libp2pLogLevel
	dhtE, mDNS := c.Discovery.DHT, c.Discovery.MDNS

	ledgerState := c.Ledger.StateDir

	peers := c.Discovery.BootstrapPeers

	lvl, err := log.LevelFromString(logLevel)
	if err != nil {
		lvl = log.LevelError
	}

	llger := logger.New(lvl)

	libp2plvl, err := log.LevelFromString(libp2plogLevel)
	if err != nil {
		libp2plvl = log.LevelFatal
	}

	token := c.NetworkToken

	addrsList := peers2List(peers)

	dhtOpts := []dht.Option{}

	if c.LowProfile {
		dhtOpts = append(dhtOpts, dht.BucketSize(20))
	}
	d := discovery.NewDHT(dhtOpts...)
	m := &discovery.MDNS{}

	opts := []node.Option{
		node.WithDiscoveryInterval(c.Discovery.Interval),
		node.WithLedgerAnnounceTime(c.Ledger.AnnounceInterval),
		node.WithLedgerInterval(c.Ledger.SyncInterval),
		node.Logger(llger),
		node.WithDiscoveryBootstrapPeers(addrsList),
		node.WithBlacklist(c.Blacklist...),
		node.LibP2PLogLevel(libp2plvl),
		node.WithInterfaceAddress(address),
		node.WithSealer(&crypto.AESSealer{}),
		node.FromBase64(mDNS, dhtE, token, d, m),
		node.FromYaml(mDNS, dhtE, config, d, m),
	}

	vpnOpts := []vpn.Option{
		vpn.WithConcurrency(c.Concurrency),
		vpn.WithInterfaceAddress(address),
		vpn.WithLedgerAnnounceTime(c.Ledger.AnnounceInterval),
		vpn.Logger(llger),
		vpn.WithTimeout(c.FrameTimeout),
		vpn.WithInterfaceType(water.TUN),
		vpn.NetLinkBootstrap(c.BootstrapIface),
		vpn.WithChannelBufferSize(c.ChannelBufferSize),
		vpn.WithInterfaceMTU(c.InterfaceMTU),
		vpn.WithPacketMTU(c.PacketMTU),
		vpn.WithRouterAddress(router),
		vpn.WithInterfaceName(iface),
	}

	libp2pOpts := []libp2p.Option{libp2p.UserAgent("edgevpn")}

	// AutoRelay section configuration
	if c.Connection.AutoRelay {
		relayOpts := []autorelay.Option{}
		if c.Connection.RelayV1 {
			relayOpts = append(relayOpts, autorelay.WithCircuitV1Support())
		}

		staticRelays := c.Connection.StaticRelays
		if c.Connection.AutoRelayDiscoveryInterval == 0 {
			c.Connection.AutoRelayDiscoveryInterval = 5 * time.Minute
		}
		// If no relays are specified and no discovery interval, then just use default static relays (to be deprecated)

		relayOpts = append(relayOpts, autorelay.WithPeerSource(d.FindClosePeers(llger, c.Connection.OnlyStaticRelays, staticRelays...), c.Connection.AutoRelayDiscoveryInterval))

		libp2pOpts = append(libp2pOpts,
			libp2p.EnableAutoRelay(relayOpts...))
	}

	if c.Connection.Mplex {
		libp2pOpts = append(libp2pOpts,
			libp2p.ChainOptions(
				libp2p.Muxer("/yamux/1.0.0", yamux.DefaultTransport),
				libp2p.Muxer("/mplex/6.7.0", mplex.DefaultTransport),
			))
	}

	if c.NAT.RateLimit {
		libp2pOpts = append(libp2pOpts, libp2p.AutoNATServiceRateLimit(
			c.NAT.RateLimitGlobal,
			c.NAT.RateLimitPeer,
			c.NAT.RateLimitInterval,
		))
	}

	if c.Connection.MaxConnections != 0 {
		cm, err := connmanager.NewConnManager(
			1,
			c.Connection.MaxConnections,
			connmanager.WithGracePeriod(80*time.Second),
		)
		if err != nil {
			llger.Fatal("could not create connection manager")
		}

		libp2pOpts = append(libp2pOpts, libp2p.ConnectionManager(cm))
	}

	if !c.Limit.Enable || runtime.GOOS == "darwin" {
		libp2pOpts = append(libp2pOpts, libp2p.ResourceManager(&network.NullResourceManager{}))
	} else {
		var limiter rcmgr.Limiter

		if c.Limit.FileLimit != "" {
			limitFile, err := os.Open(c.Limit.FileLimit)
			if err != nil {
				return opts, vpnOpts, err
			}
			defer limitFile.Close()

			l, err := rcmgr.NewDefaultLimiterFromJSON(limitFile)
			if err != nil {
				return opts, vpnOpts, err
			}

			limiter = l
		} else if c.Limit.MaxConns != 0 {
			min := int64(1 << 30)
			max := int64(4 << 30)
			if c.Limit.StaticMin != 0 {
				min = c.Limit.StaticMin
			}
			if c.Limit.StaticMax != 0 {
				max = c.Limit.StaticMax
			}
			maxconns := int(c.Limit.MaxConns)

			defaultLimits := rcmgr.DefaultLimits.Scale(min+max/2, logScale(2*maxconns))

			limiter = rcmgr.NewFixedLimiter(defaultLimits)

		} else {
			defaults := rcmgr.DefaultLimits
			def := &defaults

			libp2p.SetDefaultServiceLimits(def)
			limiter = rcmgr.NewFixedLimiter(def.AutoScale())
		}

		rc, err := rcmgr.NewResourceManager(limiter)
		if err != nil {
			llger.Fatal("could not create resource manager")
		}

		if c.Limit.LimitConfig != nil {
			if err := node.NetSetLimit(rc, c.Limit.Scope, &c.Limit.LimitConfig.System); err != nil {
				return opts, vpnOpts, err
			}
		}

		libp2pOpts = append(libp2pOpts, libp2p.ResourceManager(rc))
	}

	if c.Connection.HolePunch {
		libp2pOpts = append(libp2pOpts, libp2p.EnableHolePunching())
	}

	if c.NAT.Service {
		libp2pOpts = append(libp2pOpts, libp2p.EnableNATService())
	}

	if c.NAT.Map {
		libp2pOpts = append(libp2pOpts, libp2p.NATPortMap())
	}

	opts = append(opts, node.WithLibp2pOptions(libp2pOpts...))

	if ledgerState != "" {
		opts = append(opts, node.WithStore(blockchain.NewDiskStore(diskv.New(diskv.Options{
			BasePath:     ledgerState,
			CacheSizeMax: uint64(50), // 50MB
		}))))
	} else {
		opts = append(opts, node.WithStore(&blockchain.MemoryStore{}))
	}

	if c.PeerGuard.Enable {
		pg := trustzone.NewPeerGater(c.PeerGuard.Relaxed)
		dur := c.PeerGuard.SyncInterval

		// Build up the authproviders for the peerguardian
		aps := []trustzone.AuthProvider{}
		for ap, providerOpts := range c.PeerGuard.AuthProviders {
			a, err := authProvider(llger, ap, providerOpts)
			if err != nil {
				return opts, vpnOpts, fmt.Errorf("invalid authprovider: %w", err)
			}
			aps = append(aps, a)
		}

		pguardian := trustzone.NewPeerGuardian(llger, aps...)

		opts = append(opts,
			node.WithNetworkService(
				pg.UpdaterService(dur),
				pguardian.Challenger(dur, c.PeerGuard.Autocleanup),
			),
			node.EnableGenericHub,
			node.GenericChannelHandlers(pguardian.ReceiveMessage),
		)
		// We always pass a PeerGater such will be registered to the API if necessary
		opts = append(opts, node.WithPeerGater(pg))
		// IF it's not enabled, we just disable it right away.
		if !c.PeerGuard.PeerGate {
			pg.Disable()
		}
	}

	return opts, vpnOpts, nil
}

func authProvider(ll log.StandardLogger, s string, opts map[string]interface{}) (trustzone.AuthProvider, error) {
	switch strings.ToLower(s) {
	case "ecdsa":
		pk, exists := opts["private_key"]
		if !exists {
			return nil, fmt.Errorf("No private key provided")
		}
		return ecdsa.ECDSA521Provider(ll, fmt.Sprint(pk))
	}
	return nil, fmt.Errorf("not supported")
}

func logScale(val int) int {
	bitlen := bits.Len(uint(val))
	return 1 << bitlen
}