package htlcswitch

import (
	"fmt"
	"testing"

	"github.com/btcsuite/fastsha256"
	"github.com/lightningnetwork/lnd/channeldb"
	"github.com/lightningnetwork/lnd/lnwire"
)

func genHtlc() (*lnwire.UpdateAddHTLC, error) {
	preimage, err := genPreimage()
	if err != nil {
		return nil, fmt.Errorf("unable to generate preimage: %v", err)
	}

	rhash := fastsha256.Sum256(preimage[:])
	htlc := &lnwire.UpdateAddHTLC{
		PaymentHash: rhash,
		Amount:      1,
	}

	return htlc, nil
}

// TestPaymentControlSwitchFail checks that payment status returns to Grounded
// status after failing, and that ClearForTakeoff allows another HTLC for the
// same payment hash.
func TestPaymentControlSwitchFail(t *testing.T) {
	t.Parallel()

	db, err := initDB()
	if err != nil {
		t.Fatalf("unable to init db: %v", err)
	}

	pControl := NewPaymentControl(db)

	htlc, err := genHtlc()
	if err != nil {
		t.Fatalf("unable to generate htlc message: %v", err)
	}

	// Sends base htlc message which initiate StatusInFlight.
	if err := pControl.ClearForTakeoff(htlc); err != nil {
		t.Fatalf("unable to send htlc message: %v", err)
	}

	pStatus, err := db.FetchPaymentStatus(htlc.PaymentHash)
	if err != nil {
		t.Fatalf("unable to fetch payment status: %v", err)
	}

	if pStatus != channeldb.StatusInFlight {
		t.Fatalf("payment status mismatch: expected %v, got %v",
			channeldb.StatusInFlight, pStatus)
	}

	// Fail the payment, which should moved it to Grounded.
	if err := pControl.Fail(htlc.PaymentHash); err != nil {
		t.Fatalf("unable to fail payment hash: %v", err)
	}

	// Verify the status is indeed Grounded.
	pStatus, err = db.FetchPaymentStatus(htlc.PaymentHash)
	if err != nil {
		t.Fatalf("unable to fetch payment status: %v", err)
	}

	if pStatus != channeldb.StatusGrounded {
		t.Fatalf("payment status mismatch: expected %v, got %v",
			channeldb.StatusGrounded, pStatus)
	}

	// Sends the htlc again, which should succeed since the prior payment
	// failed.
	if err := pControl.ClearForTakeoff(htlc); err != nil {
		t.Fatalf("unable to send htlc message: %v", err)
	}

	pStatus, err := db.FetchPaymentStatus(htlc.PaymentHash)
	if err != nil {
		t.Fatalf("unable to fetch payment status: %v", err)
	}

	if pStatus != channeldb.StatusInFlight {
		t.Fatalf("payment status mismatch: expected %v, got %v",
			channeldb.StatusInFlight, pStatus)
	}

	// Verifies that status was changed to StatusCompleted.
	if err := pControl.Success(htlc.PaymentHash); err != nil {
		t.Fatalf("error shouldn't have been received, got: %v", err)
	}

	pStatus, err = db.FetchPaymentStatus(htlc.PaymentHash)
	if err != nil {
		t.Fatalf("unable to fetch payment status: %v", err)
	}

	if pStatus != channeldb.StatusCompleted {
		t.Fatalf("payment status mismatch: expected %v, got %v",
			channeldb.StatusCompleted, pStatus)
	}

	// Attempt a final payment, which should now fail since the prior
	// payment succeed.
	if err := pControl.ClearForTakeoff(htlc); err != nil {
		t.Fatalf("unable to send htlc message: %v", err)
	}
}

// TestPaymentControlSwitchDoubleSend checks the ability of payment control to
// prevent double sending of htlc message, when message is in StatusInFlight.
func TestPaymentControlSwitchDoubleSend(t *testing.T) {
	t.Parallel()

	db, err := initDB()
	if err != nil {
		t.Fatalf("unable to init db: %v", err)
	}

	pControl := NewPaymentControl(db)

	htlc, err := genHtlc()
	if err != nil {
		t.Fatalf("unable to generate htlc message: %v", err)
	}

	// Sends base htlc message which initiate base status and move it to
	// StatusInFlight and verifies that it was changed.
	if err := pControl.ClearForTakeoff(htlc); err != nil {
		t.Fatalf("unable to send htlc message: %v", err)
	}

	pStatus, err := db.FetchPaymentStatus(htlc.PaymentHash)
	if err != nil {
		t.Fatalf("unable to fetch payment status: %v", err)
	}

	if pStatus != channeldb.StatusInFlight {
		t.Fatalf("payment status mismatch: expected %v, got %v",
			channeldb.StatusInFlight, pStatus)
	}

	// Try to initiate double sending of htlc message with the same
	// payment hash, should result in error indicating that payment has
	// already been sent.
	if err := pControl.ClearForTakeoff(htlc); err != ErrPaymentInFlight {
		t.Fatalf("payment control wrong behaviour: " +
			"double sending must trigger ErrPaymentInFlight error")
	}
}

// TestPaymentControlSwitchDoublePay checks the ability of payment control to
// prevent double payment.
func TestPaymentControlSwitchDoublePay(t *testing.T) {
	t.Parallel()

	db, err := initDB()
	if err != nil {
		t.Fatalf("unable to init db: %v", err)
	}

	pControl := NewPaymentControl(db)

	htlc, err := genHtlc()
	if err != nil {
		t.Fatalf("unable to generate htlc message: %v", err)
	}

	// Sends base htlc message which initiate StatusInFlight.
	if err := pControl.ClearForTakeoff(htlc); err != nil {
		t.Fatalf("unable to send htlc message: %v", err)
	}

	// Verify that payment is InFlight.
	pStatus, err := db.FetchPaymentStatus(htlc.PaymentHash)
	if err != nil {
		t.Fatalf("unable to fetch payment status: %v", err)
	}

	if pStatus != channeldb.StatusInFlight {
		t.Fatalf("payment status mismatch: expected %v, got %v",
			channeldb.StatusInFlight, pStatus)
	}

	// Move payment to completed status, second payment should return error.
	if err := pControl.Success(htlc.PaymentHash); err != nil {
		t.Fatalf("error shouldn't have been received, got: %v", err)
	}

	// Verify that payment is Completed.
	pStatus, err = db.FetchPaymentStatus(htlc.PaymentHash)
	if err != nil {
		t.Fatalf("unable to fetch payment status: %v", err)
	}

	if pStatus != channeldb.StatusCompleted {
		t.Fatalf("payment status mismatch: expected %v, got %v",
			channeldb.StatusCompleted, pStatus)
	}

	if err := pControl.ClearForTakeoff(htlc); err != ErrAlreadyPaid {
		t.Fatalf("payment control wrong behaviour:" +
			" double payment must trigger ErrAlreadyPaid")
	}
}