package wtclient

import (
	"net"

	"github.com/btcsuite/btcd/btcec"
	"github.com/lightningnetwork/lnd/brontide"
	"github.com/lightningnetwork/lnd/keychain"
	"github.com/lightningnetwork/lnd/lnwire"
	"github.com/lightningnetwork/lnd/watchtower/wtdb"
	"github.com/lightningnetwork/lnd/watchtower/wtserver"
)

// DB abstracts the required database operations required by the watchtower
// client.
type DB interface {
	// CreateTower initialize an address record used to communicate with a
	// watchtower. Each Tower is assigned a unique ID, that is used to
	// amortize storage costs of the public key when used by multiple
	// sessions. If the tower already exists, the address is appended to the
	// list of all addresses used to that tower previously and its
	// corresponding sessions are marked as active.
	CreateTower(*lnwire.NetAddress) (*wtdb.Tower, error)

	// RemoveTower modifies a tower's record within the database. If an
	// address is provided, then _only_ the address record should be removed
	// from the tower's persisted state. Otherwise, we'll attempt to mark
	// the tower as inactive by marking all of its sessions inactive. If any
	// of its sessions has unacked updates, then ErrTowerUnackedUpdates is
	// returned. If the tower doesn't have any sessions at all, it'll be
	// completely removed from the database.
	//
	// NOTE: An error is not returned if the tower doesn't exist.
	RemoveTower(*btcec.PublicKey, net.Addr) error

	// LoadTower retrieves a tower by its public key.
	LoadTower(*btcec.PublicKey) (*wtdb.Tower, error)

	// LoadTowerByID retrieves a tower by its tower ID.
	LoadTowerByID(wtdb.TowerID) (*wtdb.Tower, error)

	// ListTowers retrieves the list of towers available within the
	// database.
	ListTowers() ([]*wtdb.Tower, error)

	// NextSessionKeyIndex reserves a new session key derivation index for a
	// particular tower id. The index is reserved for that tower until
	// CreateClientSession is invoked for that tower and index, at which
	// point a new index for that tower can be reserved. Multiple calls to
	// this method before CreateClientSession is invoked should return the
	// same index.
	NextSessionKeyIndex(wtdb.TowerID) (uint32, error)

	// CreateClientSession saves a newly negotiated client session to the
	// client's database. This enables the session to be used across
	// restarts.
	CreateClientSession(*wtdb.ClientSession) error

	// ListClientSessions returns all sessions that have not yet been
	// exhausted. This is used on startup to find any sessions which may
	// still be able to accept state updates. An optional tower ID can be
	// used to filter out any client sessions in the response that do not
	// correspond to this tower.
	ListClientSessions(*wtdb.TowerID) (map[wtdb.SessionID]*wtdb.ClientSession, error)

	// FetchChanSummaries loads a mapping from all registered channels to
	// their channel summaries.
	FetchChanSummaries() (wtdb.ChannelSummaries, error)

	// RegisterChannel registers a channel for use within the client
	// database. For now, all that is stored in the channel summary is the
	// sweep pkscript that we'd like any tower sweeps to pay into. In the
	// future, this will be extended to contain more info to allow the
	// client efficiently request historical states to be backed up under
	// the client's active policy.
	RegisterChannel(lnwire.ChannelID, []byte) error

	// MarkBackupIneligible records that the state identified by the
	// (channel id, commit height) tuple was ineligible for being backed up
	// under the current policy. This state can be retried later under a
	// different policy.
	MarkBackupIneligible(chanID lnwire.ChannelID, commitHeight uint64) error

	// CommitUpdate writes the next state update for a particular
	// session, so that we can be sure to resend it after a restart if it
	// hasn't been ACK'd by the tower. The sequence number of the update
	// should be exactly one greater than the existing entry, and less that
	// or equal to the session's MaxUpdates.
	CommitUpdate(id *wtdb.SessionID,
		update *wtdb.CommittedUpdate) (uint16, error)

	// AckUpdate records an acknowledgment from the watchtower that the
	// update identified by seqNum was received and saved. The returned
	// lastApplied will be recorded.
	AckUpdate(id *wtdb.SessionID, seqNum, lastApplied uint16) error
}

// Dial connects to an addr using the specified net and returns the connection
// object.
type Dial func(net, addr string) (net.Conn, error)

// AuthDialer connects to a remote node using an authenticated transport, such as
// brontide. The dialer argument is used to specify a resolver, which allows
// this method to be used over Tor or clear net connections.
type AuthDialer func(localKey keychain.SingleKeyECDH, netAddr *lnwire.NetAddress,
	dialer func(string, string) (net.Conn, error)) (wtserver.Peer, error)

// AuthDial is the watchtower client's default method of dialing.
func AuthDial(localKey keychain.SingleKeyECDH, netAddr *lnwire.NetAddress,
	dialer func(string, string) (net.Conn, error)) (wtserver.Peer, error) {

	return brontide.Dial(localKey, netAddr, dialer)
}

// ECDHKeyRing abstracts the ability to derive shared ECDH keys given a
// description of the derivation path of a private key.
type ECDHKeyRing interface {
	keychain.ECDHRing

	// DeriveKey attempts to derive an arbitrary key specified by the
	// passed KeyLocator. This may be used in several recovery scenarios,
	// or when manually rotating something like our current default node
	// key.
	DeriveKey(keyLoc keychain.KeyLocator) (keychain.KeyDescriptor, error)
}