package tapir

import (
	"crypto/rand"
	"encoding/base64"
	"encoding/binary"
	"errors"
	"git.openprivacy.ca/openprivacy/libricochet-go/connectivity"
	"git.openprivacy.ca/openprivacy/libricochet-go/identity"
	"git.openprivacy.ca/openprivacy/libricochet-go/log"
	"golang.org/x/crypto/ed25519"
	"golang.org/x/crypto/nacl/secretbox"
	"io"
	"net"
	"sync"
)

// Service defines the interface for a Tapir Service
type Service interface {
	Start(acn connectivity.ACN, privateKey ed25519.PrivateKey, identity identity.Identity)
	Connect(hostname string, application Application) (string, error)
	Listen(application Application) error
	GetConnection(connectionID string) (*Connection, error)
}

// Connection defines a Tapir Connection
type Connection struct {
	hostname     string
	conn         net.Conn
	capabilities sync.Map
	encrypted    bool
	key          [32]byte
	app          Application
	ID           identity.Identity
	Outbound     bool
}

// NewConnection creates a new Connection
func NewConnection(id identity.Identity, hostname string, outbound bool, conn net.Conn, app Application) *Connection {
	connection := new(Connection)
	connection.hostname = hostname
	connection.conn = conn
	connection.app = app
	connection.ID = id
	connection.Outbound = outbound
	go connection.app.Init(connection)
	return connection
}

// SetHostname sets the hostname on the connection
func (c *Connection) SetHostname(hostname string) {
	log.Debugf("[%v -- %v] Asserting Remote Hostname: %v", c.ID.Hostname(), c.hostname, hostname)
	c.hostname = hostname
}

// SetCapability sets a capability on the connection
func (c *Connection) SetCapability(name string) {
	log.Debugf("[%v -- %v] Setting Capability %v", c.ID.Hostname(), c.hostname, name)
	c.capabilities.Store(name, true)
}

// HasCapability checks if the connection has a given capability
func (c *Connection) HasCapability(name string) bool {
	_, ok := c.capabilities.Load(name)
	return ok
}

// Expect blocks and reads a single Tapir packet (1024 bytes), from the connection.
func (c *Connection) Expect() []byte {
	buffer := make([]byte, 1024)
	n, err := io.ReadFull(c.conn, buffer)

	if n != 1024 || err != nil {
		log.Errorf("[%v -> %v] Wire Error Reading, Read %d bytes, Error: %v", c.hostname, c.ID.Hostname(), n, err)
		return []byte{}
	}
	//log.Debugf("[%v -> %v] Wire Receive: %x", c.hostname, c.ID.Hostname(), buffer)

	if c.encrypted {
		var decryptNonce [24]byte
		copy(decryptNonce[:], buffer[:24])
		decrypted, ok := secretbox.Open(nil, buffer[24:], &decryptNonce, &c.key)
		if ok {
			copy(buffer, decrypted)
		} else {
			log.Errorf("[%v -> %v] Error Decrypting Message On Wire", c.hostname, c.ID.Hostname())
			return []byte{}
		}
	}
	len, _ := binary.Uvarint(buffer[0:2])
	return buffer[2 : len+2]
}

// SetEncryptionKey turns on application-level encryption on the connection using the given key.
func (c *Connection) SetEncryptionKey(key [32]byte) {
	c.key = key
	c.encrypted = true
}

// Send writes a given message to a Tapir packet (of 1024 bytes in length).
func (c *Connection) Send(message []byte) {

	maxLength := 1024
	buffer := make([]byte, maxLength)
	binary.PutUvarint(buffer[0:2], uint64(len(message)))
	copy(buffer[2:], message)

	if c.encrypted {
		var nonce [24]byte
		if _, err := io.ReadFull(rand.Reader, nonce[:]); err != nil {
			panic(err)
		}
		// MaxLength - 40 = MaxLength - 24 nonce bytes and 16 auth tag.
		encrypted := secretbox.Seal(nonce[:], buffer[0:maxLength-40], &nonce, &c.key)
		copy(buffer, encrypted[0:1024])
	}
	//log.Debugf("[%v -> %v] Wire Send %x",  c.ID.Hostname(), c.hostname, buffer)
	c.conn.Write(buffer)
}

// BaseOnionService is a concrete implementation of the service interface over Tor onion services.
type BaseOnionService struct {
	connections sync.Map
	acn         connectivity.ACN
	id          identity.Identity
	privateKey  ed25519.PrivateKey
}

// Start initializes a BaseOnionService with a given private key and identity
// The private key is needed to initialize the Onion listen socket, ideally we could just pass an Identity in here.
func (s *BaseOnionService) Start(acn connectivity.ACN, sk ed25519.PrivateKey, id identity.Identity) {
	// run add onion
	// get listen context
	s.acn = acn
	s.id = id
	s.privateKey = sk
}

// GetConnection returns a connection for a given hostname.
func (s *BaseOnionService) GetConnection(connectionID string) (*Connection, error) {
	conn, ok := s.connections.Load(connectionID)
	if !ok {
		return nil, errors.New("no connection found")
	}
	connection := conn.(*Connection)
	return connection, nil
}

// Connect initializes a new outbound connection to the given peer, using the defined Application
func (s *BaseOnionService) Connect(hostname string, app Application) (string, error) {
	// connects to a remote server
	// spins off to a connection struct
	log.Debugf("Connecting to %v", hostname)
	conn, _, err := s.acn.Open(hostname)
	if err == nil {
		connectionID := s.getNewConnectionID()
		log.Debugf("Connected to %v [%v]", hostname, connectionID)
		s.connections.Store(connectionID, NewConnection(s.id, hostname, true, conn, app.NewInstance()))
		return connectionID, nil
	}
	log.Debugf("Error connecting to %v %v", hostname, err)
	return "", err
}

func (s *BaseOnionService) getNewConnectionID() string {
	id := make([]byte, 10)
	rand.Read(id)
	connectionID := "connection-" + base64.StdEncoding.EncodeToString(id)
	return connectionID
}

// Listen starts a blocking routine that waits for incoming connections and initializes connections with them based
// on the given Application.
func (s *BaseOnionService) Listen(app Application) error {
	// accepts a new connection
	// spins off to a connection struct
	ls, err := s.acn.Listen(s.privateKey, 9878)
	log.Debugf("Starting a service on %v ", ls.AddressFull())
	if err == nil {
		for {
			conn, err := ls.Accept()
			if err == nil {
				tempHostname := s.getNewConnectionID()
				log.Debugf("Accepted connection from %v", tempHostname)
				s.connections.Store(tempHostname, NewConnection(s.id, tempHostname, false, conn, app.NewInstance()))
			} else {
				ls.Close()
				log.Debugf("Error accepting connection %v", err)
				return err
			}
		}
	}
	log.Debugf("Error listening to connection %v", err)
	return err
}