package channeldb

import (
	"bytes"
	"io"
	"net"
	"time"

	"github.com/boltdb/bolt"
	"github.com/roasbeef/btcd/btcec"
	"github.com/roasbeef/btcd/wire"
)

var (
	// nodeInfoBucket stores meta-data pertaining to nodes that we've had
	// direct channel-based correspondence with. This bucket allows one to
	// query for all open channels pertaining to the node by exploring each
	// node's sub-bucket within the openChanBucket.
	nodeInfoBucket = []byte("nib")
)

// LinkNode stores meta-data related to node's that we have/had a direct
// channel open with. Information such as the Bitcoin network the node
// advertised, and its identity public key are also stored. Additionally, this
// struct and the bucket its stored within have store data similar to that of
// Bitcion's addrmanager. The TCP address information stored within the struct
// can be used to establish persistent connections will all channel
// counter-parties on daemon startup.
//
// TODO(roasbeef): also add current OnionKey plus rotation schedule?
// TODO(roasbeef): add bitfield for supported services
//  * possibly add a wire.NetAddress type, type
type LinkNode struct {
	// Network indicates the Bitcoin network that the LinkNode advertises
	// for incoming channel creation.
	Network wire.BitcoinNet

	// IdentityPub is the node's current identity public key. Any
	// channel/topology related information received by this node MUST be
	// signed by this public key.
	IdentityPub *btcec.PublicKey

	// LastSeen tracks the last time this node was seen within the network.
	// A node should be marked as seen if the daemon either is able to
	// establish an outgoing connection to the node or receives a new
	// incoming connection from the node. This timestamp (stored in unix
	// epoch) may be used within a heuristic which aims to determine when a
	// channel should be unilaterally closed due to inactivity.
	//
	// TODO(roasbeef): replace with block hash/height?
	//  * possibly add a time-value metric into the heuristic?
	LastSeen time.Time

	// Addresses is a list of IP address in which either we were able to
	// reach the node over in the past, OR we received an incoming
	// authenticated connection for the stored identity public key.
	//
	// TODO(roasbeef): also need to support hidden service addrs
	Addresses []*net.TCPAddr

	db *DB
}

// NewLinkNode creates a new LinkNode from the provided parameters, which is
// backed by an instance of channeldb.
func (db *DB) NewLinkNode(bitNet wire.BitcoinNet, pub *btcec.PublicKey,
	addr *net.TCPAddr) *LinkNode {

	return &LinkNode{
		Network:     bitNet,
		IdentityPub: pub,
		LastSeen:    time.Now(),
		Addresses:   []*net.TCPAddr{addr},
		db:          db,
	}
}

// UpdateLastSeen updates the last time this node was directly encountered on
// the Lightning Network.
func (l *LinkNode) UpdateLastSeen(lastSeen time.Time) error {
	l.LastSeen = lastSeen

	return l.Sync()
}

// AddAddress appends the specified TCP address to the list of known addresses
// this node is/was known to be reachable at.
func (l *LinkNode) AddAddress(addr *net.TCPAddr) error {
	for _, a := range l.Addresses {
		if a.String() == addr.String() {
			return nil
		}
	}

	l.Addresses = append(l.Addresses, addr)

	return l.Sync()
}

// Sync performs a full database sync which writes the current up-to-date data
// within the struct to the database.
func (l *LinkNode) Sync() error {

	// Finally update the database by storing the link node and updating
	// any relevant indexes.
	return l.db.Update(func(tx *bolt.Tx) error {
		nodeMetaBucket := tx.Bucket(nodeInfoBucket)
		if nodeMetaBucket == nil {
			return ErrLinkNodesNotFound
		}

		return putLinkNode(nodeMetaBucket, l)
	})
}

// putLinkNode serializes then writes the encoded version of the passed link
// node into the nodeMetaBucket. This function is provided in order to allow
// the ability to re-use a database transaction across many operations.
func putLinkNode(nodeMetaBucket *bolt.Bucket, l *LinkNode) error {
	// First serialize the LinkNode into its raw-bytes encoding.
	var b bytes.Buffer
	if err := serializeLinkNode(&b, l); err != nil {
		return err
	}

	// Finally insert the link-node into the node meta-data bucket keyed
	// according to the its pubkey serialized in compressed form.
	nodePub := l.IdentityPub.SerializeCompressed()
	return nodeMetaBucket.Put(nodePub, b.Bytes())
}

// FetchLinkNode attempts to lookup the data for a LinkNode based on a target
// identity public key. If a particular LinkNode for the passed identity public
// key cannot be found, then ErrNodeNotFound if returned.
func (db *DB) FetchLinkNode(identity *btcec.PublicKey) (*LinkNode, error) {
	var (
		node *LinkNode
		err  error
	)

	err = db.View(func(tx *bolt.Tx) error {
		// First fetch the bucket for storing node meta-data, bailing
		// out early if it hasn't been created yet.
		nodeMetaBucket := tx.Bucket(nodeInfoBucket)
		if nodeMetaBucket == nil {
			return ErrLinkNodesNotFound
		}

		// If a link node for that particular public key cannot be
		// located, then exit early with a ErrNodeNotFound.
		pubKey := identity.SerializeCompressed()
		nodeBytes := nodeMetaBucket.Get(pubKey)
		if nodeBytes == nil {
			return ErrNodeNotFound
		}

		// Finally, decode an allocate a fresh LinkNode object to be
		// returned to the caller.
		nodeReader := bytes.NewReader(nodeBytes)
		node, err = deserializeLinkNode(nodeReader)
		if err != nil {
			return err
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	return node, nil
}

// FetchAllLinkNodes attempts to fetch all active LinkNodes from the database.
// If there haven't been any channels explicitly linked to LinkNodes written to
// the database, then this function will return an empty slice.
func (db *DB) FetchAllLinkNodes() ([]*LinkNode, error) {
	var linkNodes []*LinkNode

	err := db.View(func(tx *bolt.Tx) error {
		nodeMetaBucket := tx.Bucket(nodeInfoBucket)
		if nodeMetaBucket == nil {
			return ErrLinkNodesNotFound
		}

		return nodeMetaBucket.ForEach(func(k, v []byte) error {
			if v == nil {
				return nil
			}

			nodeReader := bytes.NewReader(v)
			linkNode, err := deserializeLinkNode(nodeReader)
			if err != nil {
				return err
			}

			linkNodes = append(linkNodes, linkNode)
			return nil
		})

		return nil
	})
	if err != nil {
		return nil, err
	}

	return linkNodes, nil
}

func serializeLinkNode(w io.Writer, l *LinkNode) error {
	var buf [8]byte

	byteOrder.PutUint32(buf[:4], uint32(l.Network))
	if _, err := w.Write(buf[:4]); err != nil {
		return err
	}

	serializedID := l.IdentityPub.SerializeCompressed()
	if _, err := w.Write(serializedID); err != nil {
		return err
	}

	seenUnix := uint64(l.LastSeen.Unix())
	byteOrder.PutUint64(buf[:], seenUnix)
	if _, err := w.Write(buf[:]); err != nil {
		return err
	}

	numAddrs := uint32(len(l.Addresses))
	byteOrder.PutUint32(buf[:4], numAddrs)
	if _, err := w.Write(buf[:4]); err != nil {
		return err
	}

	for _, addr := range l.Addresses {
		addrString := addr.String()
		if err := wire.WriteVarString(w, 0, addrString); err != nil {
			return err
		}
	}

	return nil
}

func deserializeLinkNode(r io.Reader) (*LinkNode, error) {
	var (
		err error
		buf [8]byte
	)

	node := &LinkNode{}

	if _, err := io.ReadFull(r, buf[:4]); err != nil {
		return nil, err
	}
	node.Network = wire.BitcoinNet(byteOrder.Uint32(buf[:4]))

	var pub [33]byte
	if _, err := io.ReadFull(r, pub[:]); err != nil {
		return nil, err
	}
	node.IdentityPub, err = btcec.ParsePubKey(pub[:], btcec.S256())
	if err != nil {
		return nil, err
	}

	if _, err := io.ReadFull(r, buf[:]); err != nil {
		return nil, err
	}
	node.LastSeen = time.Unix(int64(byteOrder.Uint64(buf[:])), 0)

	if _, err := io.ReadFull(r, buf[:4]); err != nil {
		return nil, err
	}
	numAddrs := byteOrder.Uint32(buf[:4])

	node.Addresses = make([]*net.TCPAddr, numAddrs)
	for i := uint32(0); i < numAddrs; i++ {
		addrString, err := wire.ReadVarString(r, 0)
		if err != nil {
			return nil, err
		}

		addr, err := net.ResolveTCPAddr("tcp", addrString)
		if err != nil {
			return nil, err
		}
		node.Addresses[i] = addr
	}

	return node, nil
}