///////////////////////////////////////////////////////////////////////////////
// Copyright © 2020 xx network SEZC                                          //
//                                                                           //
// Use of this source code is governed by a license that can be found in the //
// LICENSE file                                                              //
///////////////////////////////////////////////////////////////////////////////

package api

import (
	"gitlab.com/xx_network/primitives/id"
	"time"

	"github.com/pkg/errors"
	jww "github.com/spf13/jwalterweatherman"
	"gitlab.com/elixxir/client/auth"
	"gitlab.com/elixxir/client/interfaces"
	"gitlab.com/elixxir/client/interfaces/params"
	"gitlab.com/elixxir/client/interfaces/user"
	"gitlab.com/elixxir/client/keyExchange"
	"gitlab.com/elixxir/client/network"
	"gitlab.com/elixxir/client/permissioning"
	"gitlab.com/elixxir/client/stoppable"
	"gitlab.com/elixxir/client/storage"
	"gitlab.com/elixxir/client/switchboard"
	"gitlab.com/elixxir/comms/client"
	"gitlab.com/elixxir/crypto/cyclic"
	"gitlab.com/elixxir/crypto/fastRNG"
	"gitlab.com/elixxir/primitives/version"
	"gitlab.com/xx_network/crypto/csprng"
	"gitlab.com/xx_network/crypto/large"
	"gitlab.com/xx_network/crypto/signature/rsa"
	"gitlab.com/xx_network/primitives/ndf"
)

type Client struct {
	//generic RNG for client
	rng *fastRNG.StreamGenerator
	// the storage session securely stores data to disk and memoizes as is
	// appropriate
	storage *storage.Session
	//the switchboard is used for inter-process signaling about received messages
	switchboard *switchboard.Switchboard
	//object used for communications
	comms *client.Comms
	// Network parameters
	parameters params.Network

	// note that the manager has a pointer to the context in many cases, but
	// this interface allows it to be mocked for easy testing without the
	// loop
	network interfaces.NetworkManager
	//object used to register and communicate with permissioning
	permissioning *permissioning.Permissioning
	//object containing auth interactions
	auth *auth.Manager

	//contains stopables for all running threads
	runner *stoppable.Multi
	status *statusTracker

	//handler for external services
	services *serviceProcessiesList

	clientErrorChannel chan interfaces.ClientError
}

// NewClient creates client storage, generates keys, connects, and registers
// with the network. Note that this does not register a username/identity, but
// merely creates a new cryptographic identity for adding such information
// at a later date.
func NewClient(ndfJSON, storageDir string, password []byte, registrationCode string) error {
	jww.INFO.Printf("NewClient()")
	// Use fastRNG for RNG ops (AES fortuna based RNG using system RNG)
	rngStreamGen := fastRNG.NewStreamGenerator(12, 3, csprng.NewSystemRNG)
	rngStream := rngStreamGen.GetStream()

	// Parse the NDF
	def, err := parseNDF(ndfJSON)
	if err != nil {
		return err
	}
	cmixGrp, e2eGrp := decodeGroups(def)

	protoUser := createNewUser(rngStream, cmixGrp, e2eGrp)

	err = checkVersionAndSetupStorage(def, storageDir, password, protoUser, 
		cmixGrp, e2eGrp, rngStreamGen, false, registrationCode)
	if err != nil {
		return err
	}

	//TODO: close the session
	return nil
}

// NewPrecannedClient creates an insecure user with predetermined keys with nodes
// It creates client storage, generates keys, connects, and registers
// with the network. Note that this does not register a username/identity, but
// merely creates a new cryptographic identity for adding such information
// at a later date.
func NewPrecannedClient(precannedID uint, defJSON, storageDir string, password []byte) error {
	jww.INFO.Printf("NewPrecannedClient()")
	// Use fastRNG for RNG ops (AES fortuna based RNG using system RNG)
	rngStreamGen := fastRNG.NewStreamGenerator(12, 3, csprng.NewSystemRNG)
	rngStream := rngStreamGen.GetStream()

	// Parse the NDF
	def, err := parseNDF(defJSON)
	if err != nil {
		return err
	}
	cmixGrp, e2eGrp := decodeGroups(def)

	protoUser := createPrecannedUser(precannedID, rngStream, cmixGrp, e2eGrp)

	err = checkVersionAndSetupStorage(def, storageDir, password, protoUser, 
		cmixGrp, e2eGrp, rngStreamGen, true, "")
	if err != nil {
		return err
	}
	//TODO: close the session
	return nil
}

// NewVanityClient creates a user with a receptionID that starts with the supplied prefix
// It creates client storage, generates keys, connects, and registers
// with the network. Note that this does not register a username/identity, but
// merely creates a new cryptographic identity for adding such information
// at a later date.
func NewVanityClient(ndfJSON, storageDir string, password []byte, registrationCode string, userIdPrefix string) error {
	jww.INFO.Printf("NewVanityClient()")
	// Use fastRNG for RNG ops (AES fortuna based RNG using system RNG)
	rngStreamGen := fastRNG.NewStreamGenerator(12, 3, csprng.NewSystemRNG)
	rngStream := rngStreamGen.GetStream()

	// Parse the NDF
	def, err := parseNDF(ndfJSON)
	if err != nil {
		return err
	}
	cmixGrp, e2eGrp := decodeGroups(def)

	protoUser := createNewVanityUser(rngStream, cmixGrp, e2eGrp, userIdPrefix)

	err = checkVersionAndSetupStorage(def, storageDir, password, protoUser, 
		cmixGrp, e2eGrp, rngStreamGen, false, registrationCode)
	if err != nil {
		return err
	}

	//TODO: close the session
	return nil
}

// OpenClient session, but don't connect to the network or log in
func OpenClient(storageDir string, password []byte, parameters params.Network) (*Client, error) {
	jww.INFO.Printf("OpenClient()")
	// Use fastRNG for RNG ops (AES fortuna based RNG using system RNG)
	rngStreamGen := fastRNG.NewStreamGenerator(12, 3, csprng.NewSystemRNG)

	// Get current client version
	currentVersion, err := version.ParseVersion(SEMVER)
	if err != nil {
		return nil, errors.WithMessage(err, "Could not parse version string.")
	}

	// Load Storage
	passwordStr := string(password)
	storageSess, err := storage.Load(storageDir, passwordStr, currentVersion,
		rngStreamGen)
	if err != nil {
		return nil, err
	}

	// Set up a new context
	c := &Client{
		storage:     storageSess,
		switchboard: switchboard.New(),
		rng:         rngStreamGen,
		comms:       nil,
		network:     nil,
		runner:      stoppable.NewMulti("client"),
		status:      newStatusTracker(),
		parameters:  parameters,
	}

	return c, nil
}

// Login initalizes a client object from existing storage.
func Login(storageDir string, password []byte, parameters params.Network) (*Client, error) {
	jww.INFO.Printf("Login()")

	//Open the client
	c, err := OpenClient(storageDir, password, parameters)

	if err != nil {
		return nil, err
	}

	//Attach the services interface
	c.services = newServiceProcessiesList(c.runner)

	//initilize comms
	err = c.initComms()
	if err != nil {
		return nil, err
	}

	//get the NDF to pass into permissioning and the network manager
	def := c.storage.GetBaseNDF()

	//initialize permissioning
	if def.Registration.Address != "" {
		err = c.initPermissioning(def)
		if err != nil {
			return nil, err
		}
	} else {
		jww.WARN.Printf("Registration with permissioning skipped due to " +
			"blank permissionign address. Client will not be able to register " +
			"or track network.")
	}

	// Initialize network and link it to context
	c.network, err = network.NewManager(c.storage, c.switchboard, c.rng, c.comms,
		parameters, def)
	if err != nil {
		return nil, err
	}

	//update gateway connections
	err = c.network.GetInstance().UpdateGatewayConnections()
	if err != nil {
		return nil, err
	}

	//initilize the auth tracker
	c.auth = auth.NewManager(c.switchboard, c.storage, c.network)

	return c, nil
}

// LoginWithNewBaseNDF_UNSAFE initializes a client object from existing storage
// while replacing the base NDF.  This is designed for some specific deployment
// procedures and is generally unsafe.
func LoginWithNewBaseNDF_UNSAFE(storageDir string, password []byte,
	newBaseNdf string, parameters params.Network) (*Client, error) {
	jww.INFO.Printf("LoginWithNewBaseNDF_UNSAFE()")

	// Parse the NDF
	def, err := parseNDF(newBaseNdf)
	if err != nil {
		return nil, err
	}

	//Open the client
	c, err := OpenClient(storageDir, password, parameters)

	if err != nil {
		return nil, err
	}

	//Attach the services interface
	c.services = newServiceProcessiesList(c.runner)

	//initialize comms
	err = c.initComms()
	if err != nil {
		return nil, err
	}

	//store the updated base NDF
	c.storage.SetBaseNDF(def)

	//initialize permissioning
	if def.Registration.Address != "" {
		err = c.initPermissioning(def)
		if err != nil {
			return nil, err
		}
	} else {
		jww.WARN.Printf("Registration with permissioning skipped due to " +
			"blank permissionign address. Client will not be able to register " +
			"or track network.")
	}

	// Initialize network and link it to context
	c.network, err = network.NewManager(c.storage, c.switchboard, c.rng, c.comms,
		parameters, def)
	if err != nil {
		return nil, err
	}

	//update gateway connections
	err = c.network.GetInstance().UpdateGatewayConnections()
	if err != nil {
		return nil, err
	}

	//initilize the auth tracker
	c.auth = auth.NewManager(c.switchboard, c.storage, c.network)

	return c, nil
}

func (c *Client) initComms() error {
	var err error

	//get the user from session
	u := c.storage.User()
	cryptoUser := u.GetCryptographicIdentity()

	//start comms
	c.comms, err = client.NewClientComms(cryptoUser.GetTransmissionID(),
		rsa.CreatePublicKeyPem(cryptoUser.GetTransmissionRSA().GetPublic()),
		rsa.CreatePrivateKeyPem(cryptoUser.GetTransmissionRSA()),
		cryptoUser.GetTransmissionSalt())
	if err != nil {
		return errors.WithMessage(err, "failed to load client")
	}
	return nil
}

func (c *Client) initPermissioning(def *ndf.NetworkDefinition) error {
	var err error
	//initialize permissioning
	c.permissioning, err = permissioning.Init(c.comms, def)
	if err != nil {
		return errors.WithMessage(err, "failed to init "+
			"permissioning handler")
	}

	//register with permissioning if necessary
	if c.storage.GetRegistrationStatus() == storage.KeyGenComplete {
		jww.INFO.Printf("Client has not registered yet, attempting registration")
		err = c.registerWithPermissioning()
		if err != nil {
			jww.ERROR.Printf("Client has failed registration: %s", err)
			return errors.WithMessage(err, "failed to load client")
		}
		jww.INFO.Printf("Client sucsecfully registered with the network")
	}
	return nil
}

// ----- Client Functions -----
// StartNetworkFollower kicks off the tracking of the network. It starts
// long running network client threads and returns an object for checking
// state and stopping those threads.
// Call this when returning from sleep and close when going back to
// sleep.
// These threads may become a significant drain on battery when offline, ensure
// they are stopped if there is no internet access
// Threads Started:
//   - Network Follower (/network/follow.go)
//   	tracks the network events and hands them off to workers for handling
//   - Historical Round Retrieval (/network/rounds/historical.go)
//		Retrieves data about rounds which are too old to be stored by the client
//	 - Message Retrieval Worker Group (/network/rounds/retrieve.go)
//		Requests all messages in a given round from the gateway of the last node
//	 - Message Handling Worker Group (/network/message/handle.go)
//		Decrypts and partitions messages when signals via the Switchboard
//	 - Health Tracker (/network/health)
//		Via the network instance tracks the state of the network
//	 - Garbled Messages (/network/message/garbled.go)
//		Can be signaled to check all recent messages which could be be decoded
//		Uses a message store on disk for persistence
//	 - Critical Messages (/network/message/critical.go)
//		Ensures all protocol layer mandatory messages are sent
//		Uses a message store on disk for persistence
//	 - KeyExchange Trigger (/keyExchange/trigger.go)
//		Responds to sent rekeys and executes them
//   - KeyExchange Confirm (/keyExchange/confirm.go)
//		Responds to confirmations of successful rekey operations
//   - Auth Callback (/auth/callback.go)
//      Handles both auth confirm and requests
func (c *Client) StartNetworkFollower() (<-chan interfaces.ClientError, error) {
	jww.INFO.Printf("StartNetworkFollower()")

	c.clientErrorChannel = make(chan interfaces.ClientError, 1000)

	cer := func(source, message, trace string) {
		select {
		case c.clientErrorChannel <- interfaces.ClientError{
			Source:  source,
			Message: message,
			Trace:   trace,
		}:
		default:
			jww.WARN.Printf("Failed to notify about ClientError from %s: %s", source, message)
		}
	}

	err := c.status.toStarting()
	if err != nil {
		return nil, errors.WithMessage(err, "Failed to Start the Network Follower")
	}

	stopAuth := c.auth.StartProcessies()
	c.runner.Add(stopAuth)

	stopFollow, err := c.network.Follow(cer)
	if err != nil {
		return nil, errors.WithMessage(err, "Failed to start following "+
			"the network")
	}
	c.runner.Add(stopFollow)
	// Key exchange
	c.runner.Add(keyExchange.Start(c.switchboard, c.storage, c.network, c.parameters.Rekey))

	err = c.status.toRunning()
	if err != nil {
		return nil, errors.WithMessage(err, "Failed to Start the Network Follower")
	}

	c.services.run(c.runner)

	return c.clientErrorChannel, nil
}

// StopNetworkFollower stops the network follower if it is running.
// It returns errors if the Follower is in the wrong status to stop or if it
// fails to stop it.
// if the network follower is running and this fails, the client object will
// most likely be in an unrecoverable state and need to be trashed.
func (c *Client) StopNetworkFollower(timeout time.Duration) error {
	err := c.status.toStopping()
	if err != nil {
		return errors.WithMessage(err, "Failed to Stop the Network Follower")
	}
	err = c.runner.Close(timeout)
	if err != nil {
		return errors.WithMessage(err, "Failed to Stop the Network Follower")
	}
	c.runner = stoppable.NewMulti("client")
	err = c.status.toStopped()
	if err != nil {
		return errors.WithMessage(err, "Failed to Stop the Network Follower")
	}
	return nil
}

// Gets the state of the network follower. Returns:
// Stopped 	- 0
// Starting - 1000
// Running	- 2000
// Stopping	- 3000
func (c *Client) NetworkFollowerStatus() Status {
	jww.INFO.Printf("NetworkFollowerStatus()")
	return c.status.get()
}

// Returns the health tracker for registration and polling
func (c *Client) GetHealth() interfaces.HealthTracker {
	jww.INFO.Printf("GetHealth()")
	return c.network.GetHealthTracker()
}

// Returns the switchboard for Registration
func (c *Client) GetSwitchboard() interfaces.Switchboard {
	jww.INFO.Printf("GetSwitchboard()")
	return c.switchboard
}

// RegisterRoundEventsCb registers a callback for round
// events.
func (c *Client) GetRoundEvents() interfaces.RoundEvents {
	jww.INFO.Printf("GetRoundEvents()")
	jww.WARN.Printf("GetRoundEvents does not handle Client Errors edge case!")
	return c.network.GetInstance().GetRoundEvents()
}

// AddService adds a service ot be controlled by the client thread control,
// these will be started and stopped with the network follower
func (c *Client) AddService(sp ServiceProcess) {
	c.services.Add(sp)
}

// GetUser returns the current user Identity for this client. This
// can be serialized into a byte stream for out-of-band sharing.
func (c *Client) GetUser() user.User {
	jww.INFO.Printf("GetUser()")
	return c.storage.GetUser()
}

// GetComms returns the client comms object
func (c *Client) GetComms() *client.Comms {
	return c.comms
}

// GetRng returns the client rng object
func (c *Client) GetRng() *fastRNG.StreamGenerator {
	return c.rng
}

// GetStorage returns the client storage object
func (c *Client) GetStorage() *storage.Session {
	return c.storage
}

// GetNetworkInterface returns the client Network Interface
func (c *Client) GetNetworkInterface() interfaces.NetworkManager {
	return c.network
}

// GetNodeRegistrationStatus gets the current status of node registration. It
// returns the the total number of nodes in the NDF and the number of those
// which are currently registers with. An error is returned if the network is
// not healthy.
func (c *Client) GetNodeRegistrationStatus() (int, int, error) {
	// Return an error if the network is not healthy
	if !c.GetHealth().IsHealthy() {
		return 0, 0, errors.New("Cannot get number of node registrations when " +
			"network is not healthy")
	}

	nodes := c.GetNetworkInterface().GetInstance().GetPartialNdf().Get().Nodes

	cmixStore := c.storage.Cmix()

	var numRegistered int
	for i, n := range nodes{
		nid, err := id.Unmarshal(n.ID)
		if err!=nil{
			return 0,0, errors.Errorf("Failed to unmarshal node ID %v " +
				"(#%d): %s", n.ID, i, err.Error())
		}
		if cmixStore.Has(nid){
			numRegistered++
		}
	}

	// Get the number of in progress node registrations
	return numRegistered, len(nodes), nil
}

// ----- Utility Functions -----
// parseNDF parses the initial ndf string for the client. do not check the
// signature, it is deprecated.
func parseNDF(ndfString string) (*ndf.NetworkDefinition, error) {
	if ndfString == "" {
		return nil, errors.New("ndf file empty")
	}

	netDef, err := ndf.Unmarshal([]byte(ndfString))
	if err != nil {
		return nil, err
	}

	return netDef, nil
}

// decodeGroups returns the e2e and cmix groups from the ndf
func decodeGroups(ndf *ndf.NetworkDefinition) (cmixGrp, e2eGrp *cyclic.Group) {
	largeIntBits := 16

	//Generate the cmix group
	cmixGrp = cyclic.NewGroup(
		large.NewIntFromString(ndf.CMIX.Prime, largeIntBits),
		large.NewIntFromString(ndf.CMIX.Generator, largeIntBits))
	//Generate the e2e group
	e2eGrp = cyclic.NewGroup(
		large.NewIntFromString(ndf.E2E.Prime, largeIntBits),
		large.NewIntFromString(ndf.E2E.Generator, largeIntBits))

	return cmixGrp, e2eGrp
}

// checkVersionAndSetupStorage is common code shared by NewClient, NewPrecannedClient and NewVanityClient
// it checks client version and creates a new storage for user data
func checkVersionAndSetupStorage(def *ndf.NetworkDefinition, storageDir string, password []byte,
	protoUser user.User, cmixGrp, e2eGrp *cyclic.Group, rngStreamGen *fastRNG.StreamGenerator,
	isPrecanned bool, registrationCode string) error {
	// Get current client version
	currentVersion, err := version.ParseVersion(SEMVER)
	if err != nil {
		return errors.WithMessage(err, "Could not parse version string.")
	}

	// Create Storage
	passwordStr := string(password)
	storageSess, err := storage.New(storageDir, passwordStr, protoUser,
		currentVersion, cmixGrp, e2eGrp, rngStreamGen)
	if err != nil {
		return err
	}

	// Save NDF to be used in the future
	storageSess.SetBaseNDF(def)

	if !isPrecanned {
		//store the registration code for later use
		storageSess.SetRegCode(registrationCode)
		//move the registration state to keys generated
		err = storageSess.ForwardRegistrationStatus(storage.KeyGenComplete)
	} else {
		//move the registration state to indicate registered with permissioning
		err = storageSess.ForwardRegistrationStatus(storage.PermissioningComplete)
	}

	if err != nil {
		return errors.WithMessage(err, "Failed to denote state "+
			"change in session")
	}

	return nil
}