From 52427c8276c4879349d3d08f5b423515828edc59 Mon Sep 17 00:00:00 2001
From: Prathamesh Musale <prathamesh.musale0@gmail.com>
Date: Wed, 11 Oct 2023 11:31:41 +0530
Subject: [PATCH] Implement payment authentication

---
 pkg/payments/payments_manager.go | 65 ++++++++++++++++++++++++++------
 1 file changed, 53 insertions(+), 12 deletions(-)

diff --git a/pkg/payments/payments_manager.go b/pkg/payments/payments_manager.go
index 1547846e..bce32616 100644
--- a/pkg/payments/payments_manager.go
+++ b/pkg/payments/payments_manager.go
@@ -17,6 +17,7 @@
 package payments
 
 import (
+	"errors"
 	"math/big"
 	"sync"
 	"time"
@@ -41,6 +42,14 @@ const (
 	DEFAULT_LRU_CACHE_VOUCHER_TTL              = 5 * 60 // 5mins
 	DEFAULT_LRU_CACHE_MAX_PAYMENT_CHANNELS     = 10000
 	DEFAULT_LRU_CACHE_PAYMENT_CHANNEL_TTL      = DEFAULT_LRU_CACHE_ACCOUNT_TTL
+
+	DEFAULT_VOUCHER_CHECK_INTERVAL = 2
+	DEFAULT_VOUCHER_CHECK_ATTEMPTS = 5
+)
+
+var (
+	ERR_PAYMENT_NOT_RECEIVED = errors.New("Payment not received")
+	ERR_AMOUNT_INSUFFICIENT  = errors.New("Payment amount insufficient")
 )
 
 type Payment struct {
@@ -48,11 +57,6 @@ type Payment struct {
 	amount  *big.Int
 }
 
-type paymentVoucher struct {
-	payer       common.Address
-	voucherHash common.Hash
-}
-
 // Struct representing payments manager
 // Maintains either an in-process Nitro node or communication with an out-of-process Nitro node
 type PaymentsManager struct {
@@ -66,14 +70,11 @@ type PaymentsManager struct {
 
 	paidSoFarOnChannel *expirable.LRU[nitroTypes.Destination, *big.Int]
 
-	paymentListeners []chan paymentVoucher
-
 	// Used to signal shutdown of the service
 	quitChan chan bool
 }
 
 func NewPaymentsManager(runInProcessNitroNode bool) (PaymentsManager, error) {
-	// TODO: Implement
 	var err error
 
 	pm := PaymentsManager{runInProcessNitroNode: runInProcessNitroNode}
@@ -130,6 +131,50 @@ func (pm *PaymentsManager) Stop() error {
 	return nil
 }
 
+func (pm *PaymentsManager) AuthenticatePayment(voucherHash common.Hash, signerAddress common.Address, value *big.Int) error {
+	// Check the payments map for required voucher
+	var isPaymentReceived, isOfSufficientValue bool
+	for i := 0; i < DEFAULT_VOUCHER_CHECK_ATTEMPTS; i++ {
+		isPaymentReceived, isOfSufficientValue = pm.acceptReceivedPayment(voucherHash, signerAddress, value)
+
+		if isPaymentReceived {
+			if !isOfSufficientValue {
+				return ERR_AMOUNT_INSUFFICIENT
+			}
+
+			return nil
+		}
+
+		// Retry after an interval if voucher not found
+		log.Debugf("Payment from %s not found, retrying after %d sec...", signerAddress, DEFAULT_VOUCHER_CHECK_INTERVAL)
+		time.Sleep(DEFAULT_VOUCHER_CHECK_INTERVAL * time.Second)
+	}
+
+	return ERR_PAYMENT_NOT_RECEIVED
+}
+
+// Check for a given payment voucher in LRU cache map
+// Returns whether the voucher was found, whether it was of sufficient value
+func (pm *PaymentsManager) acceptReceivedPayment(voucherHash common.Hash, signerAddress common.Address, minRequiredValue *big.Int) (bool, bool) {
+	paymentsMap, ok := pm.receivedPayments.Get(signerAddress)
+	if !ok {
+		return false, false
+	}
+
+	receivedPayment, ok := paymentsMap.Get(voucherHash)
+	if !ok {
+		return false, false
+	}
+
+	if receivedPayment.amount.Cmp(minRequiredValue) < 0 {
+		return true, false
+	}
+
+	// Delete the voucher from map after consuming it
+	paymentsMap.Remove(voucherHash)
+	return true, true
+}
+
 func (pm *PaymentsManager) run(receivedVouchers <-chan payments.Voucher) {
 	log.Info("starting voucher subscription...")
 	for {
@@ -168,10 +213,6 @@ func (pm *PaymentsManager) run(receivedVouchers <-chan payments.Voucher) {
 			}
 
 			paymentsMap.Add(voucherHash, Payment{voucher: voucher, amount: paymentAmount})
-
-			for _, listener := range pm.paymentListeners {
-				listener <- paymentVoucher{payer: payer, voucherHash: voucherHash}
-			}
 		case <-pm.quitChan:
 			log.Info("stopping voucher subscription loop")
 			// TODO: stop the nitro node if that means anything