package yggdrasil

import (
	"encoding/hex"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"regexp"

	"github.com/yggdrasil-network/yggdrasil-go/src/address"
	"github.com/yggdrasil-network/yggdrasil-go/src/config"
	"github.com/yggdrasil-network/yggdrasil-go/src/crypto"
	"github.com/yggdrasil-network/yggdrasil-go/src/defaults"
)

var buildName string
var buildVersion string

// The Core object represents the Yggdrasil node. You should create a Core
// object for each Yggdrasil node you plan to run.
type Core struct {
	// This is the main data structure that holds everything else for a node
	boxPub      crypto.BoxPubKey
	boxPriv     crypto.BoxPrivKey
	sigPub      crypto.SigPubKey
	sigPriv     crypto.SigPrivKey
	switchTable switchTable
	peers       peers
	sessions    sessions
	router      router
	dht         dht
	admin       admin
	searches    searches
	multicast   multicast
	tcp         tcpInterface
	log         *log.Logger
	ifceExpr    []*regexp.Regexp // the zone of link-local IPv6 peers must match this
}

func (c *Core) init(bpub *crypto.BoxPubKey,
	bpriv *crypto.BoxPrivKey,
	spub *crypto.SigPubKey,
	spriv *crypto.SigPrivKey) {
	// TODO separate init and start functions
	//  Init sets up structs
	//  Start launches goroutines that depend on structs being set up
	// This is pretty much required to completely avoid race conditions
	if c.log == nil {
		c.log = log.New(ioutil.Discard, "", 0)
	}
	c.boxPub, c.boxPriv = *bpub, *bpriv
	c.sigPub, c.sigPriv = *spub, *spriv
	c.admin.core = c
	c.searches.init(c)
	c.dht.init(c)
	c.sessions.init(c)
	c.multicast.init(c)
	c.peers.init(c)
	c.router.init(c)
	c.switchTable.init(c, c.sigPub) // TODO move before peers? before router?
}

// Get the current build name. This is usually injected if built from git,
// or returns "unknown" otherwise.
func GetBuildName() string {
	if buildName == "" {
		return "unknown"
	}
	return buildName
}

// Get the current build version. This is usually injected if built from git,
// or returns "unknown" otherwise.
func GetBuildVersion() string {
	if buildVersion == "" {
		return "unknown"
	}
	return buildVersion
}

// Starts up Yggdrasil using the provided NodeConfig, and outputs debug logging
// through the provided log.Logger. The started stack will include TCP and UDP
// sockets, a multicast discovery socket, an admin socket, router, switch and
// DHT node.
func (c *Core) Start(nc *config.NodeConfig, log *log.Logger) error {
	c.log = log

	if name := GetBuildName(); name != "unknown" {
		c.log.Println("Build name:", name)
	}
	if version := GetBuildVersion(); version != "unknown" {
		c.log.Println("Build version:", version)
	}

	c.log.Println("Starting up...")

	var boxPub crypto.BoxPubKey
	var boxPriv crypto.BoxPrivKey
	var sigPub crypto.SigPubKey
	var sigPriv crypto.SigPrivKey
	boxPubHex, err := hex.DecodeString(nc.EncryptionPublicKey)
	if err != nil {
		return err
	}
	boxPrivHex, err := hex.DecodeString(nc.EncryptionPrivateKey)
	if err != nil {
		return err
	}
	sigPubHex, err := hex.DecodeString(nc.SigningPublicKey)
	if err != nil {
		return err
	}
	sigPrivHex, err := hex.DecodeString(nc.SigningPrivateKey)
	if err != nil {
		return err
	}
	copy(boxPub[:], boxPubHex)
	copy(boxPriv[:], boxPrivHex)
	copy(sigPub[:], sigPubHex)
	copy(sigPriv[:], sigPrivHex)

	c.init(&boxPub, &boxPriv, &sigPub, &sigPriv)
	c.admin.init(c, nc.AdminListen)

	if err := c.tcp.init(c, nc.Listen, nc.ReadTimeout); err != nil {
		c.log.Println("Failed to start TCP interface")
		return err
	}

	if nc.SwitchOptions.MaxTotalQueueSize >= SwitchQueueTotalMinSize {
		c.switchTable.queueTotalMaxSize = nc.SwitchOptions.MaxTotalQueueSize
	}

	if err := c.switchTable.start(); err != nil {
		c.log.Println("Failed to start switch")
		return err
	}

	c.sessions.setSessionFirewallState(nc.SessionFirewall.Enable)
	c.sessions.setSessionFirewallDefaults(
		nc.SessionFirewall.AllowFromDirect,
		nc.SessionFirewall.AllowFromRemote,
		nc.SessionFirewall.AlwaysAllowOutbound,
	)
	c.sessions.setSessionFirewallWhitelist(nc.SessionFirewall.WhitelistEncryptionPublicKeys)
	c.sessions.setSessionFirewallBlacklist(nc.SessionFirewall.BlacklistEncryptionPublicKeys)

	if err := c.router.start(); err != nil {
		c.log.Println("Failed to start router")
		return err
	}

	c.router.cryptokey.setEnabled(nc.TunnelRouting.Enable)
	if c.router.cryptokey.isEnabled() {
		c.log.Println("Crypto-key routing enabled")
		for ipv6, pubkey := range nc.TunnelRouting.IPv6Destinations {
			if err := c.router.cryptokey.addRoute(ipv6, pubkey); err != nil {
				panic(err)
			}
		}
		for _, source := range nc.TunnelRouting.IPv6Sources {
			if c.router.cryptokey.addSourceSubnet(source); err != nil {
				panic(err)
			}
		}
		for ipv4, pubkey := range nc.TunnelRouting.IPv4Destinations {
			if err := c.router.cryptokey.addRoute(ipv4, pubkey); err != nil {
				panic(err)
			}
		}
		for _, source := range nc.TunnelRouting.IPv4Sources {
			if c.router.cryptokey.addSourceSubnet(source); err != nil {
				panic(err)
			}
		}
	}

	if err := c.admin.start(); err != nil {
		c.log.Println("Failed to start admin socket")
		return err
	}

	if err := c.multicast.start(); err != nil {
		c.log.Println("Failed to start multicast interface")
		return err
	}

	ip := net.IP(c.router.addr[:]).String()
	if err := c.router.tun.start(nc.IfName, nc.IfTAPMode, fmt.Sprintf("%s/%d", ip, 8*len(address.GetPrefix())-1), nc.IfMTU); err != nil {
		c.log.Println("Failed to start TUN/TAP")
		return err
	}

	c.log.Println("Startup complete")
	return nil
}

// Stops the Yggdrasil node.
func (c *Core) Stop() {
	c.log.Println("Stopping...")
	c.router.tun.close()
	c.admin.close()
}

// Generates a new encryption keypair. The encryption keys are used to
// encrypt traffic and to derive the IPv6 address/subnet of the node.
func (c *Core) NewEncryptionKeys() (*crypto.BoxPubKey, *crypto.BoxPrivKey) {
	return crypto.NewBoxKeys()
}

// Generates a new signing keypair. The signing keys are used to derive the
// structure of the spanning tree.
func (c *Core) NewSigningKeys() (*crypto.SigPubKey, *crypto.SigPrivKey) {
	return crypto.NewSigKeys()
}

// Gets the node ID.
func (c *Core) GetNodeID() *crypto.NodeID {
	return crypto.GetNodeID(&c.boxPub)
}

// Gets the tree ID.
func (c *Core) GetTreeID() *crypto.TreeID {
	return crypto.GetTreeID(&c.sigPub)
}

// Gets the IPv6 address of the Yggdrasil node. This is always a /128.
func (c *Core) GetAddress() *net.IP {
	address := net.IP(address.AddrForNodeID(c.GetNodeID())[:])
	return &address
}

// Gets the routed IPv6 subnet of the Yggdrasil node. This is always a /64.
func (c *Core) GetSubnet() *net.IPNet {
	subnet := address.SubnetForNodeID(c.GetNodeID())[:]
	subnet = append(subnet, 0, 0, 0, 0, 0, 0, 0, 0)
	return &net.IPNet{IP: subnet, Mask: net.CIDRMask(64, 128)}
}

// Sets the output logger of the Yggdrasil node after startup. This may be
// useful if you want to redirect the output later.
func (c *Core) SetLogger(log *log.Logger) {
	c.log = log
}

// Adds a peer. This should be specified in the peer URI format, i.e.
// tcp://a.b.c.d:e, udp://a.b.c.d:e, socks://a.b.c.d:e/f.g.h.i:j
func (c *Core) AddPeer(addr string, sintf string) error {
	return c.admin.addPeer(addr, sintf)
}

// Adds an expression to select multicast interfaces for peer discovery. This
// should be done before calling Start. This function can be called multiple
// times to add multiple search expressions.
func (c *Core) AddMulticastInterfaceExpr(expr *regexp.Regexp) {
	c.ifceExpr = append(c.ifceExpr, expr)
}

// Adds an allowed public key. This allow peerings to be restricted only to
// keys that you have selected.
func (c *Core) AddAllowedEncryptionPublicKey(boxStr string) error {
	return c.admin.addAllowedEncryptionPublicKey(boxStr)
}

// Gets the default admin listen address for your platform.
func (c *Core) GetAdminDefaultListen() string {
	return defaults.GetDefaults().DefaultAdminListen
}

// Gets the default TUN/TAP interface name for your platform.
func (c *Core) GetTUNDefaultIfName() string {
	return defaults.GetDefaults().DefaultIfName
}

// Gets the default TUN/TAP interface MTU for your platform. This can be as high
// as 65535, depending on platform, but is never lower than 1280.
func (c *Core) GetTUNDefaultIfMTU() int {
	return defaults.GetDefaults().DefaultIfMTU
}

// Gets the maximum supported TUN/TAP interface MTU for your platform. This
// can be as high as 65535, depending on platform, but is never lower than 1280.
func (c *Core) GetTUNMaximumIfMTU() int {
	return defaults.GetDefaults().MaximumIfMTU
}

// Gets the default TUN/TAP interface mode for your platform.
func (c *Core) GetTUNDefaultIfTAPMode() bool {
	return defaults.GetDefaults().DefaultIfTAPMode
}

// Gets the current TUN/TAP interface name.
func (c *Core) GetTUNIfName() string {
	return c.router.tun.iface.Name()
}

// Gets the current TUN/TAP interface MTU.
func (c *Core) GetTUNIfMTU() int {
	return c.router.tun.mtu
}