feat: client payment account integration

api/clients/accountant.go

@@ -0,0 +1,127 @@
+package clients
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"errors"
+	"math/big"
+	"time"
+
+	"github.com/Layr-Labs/eigenda/core"
+	"github.com/Layr-Labs/eigenda/core/meterer"
+)
+
+type IAccountant interface {
+	AccountBlob(ctx context.Context, data []byte, quorums []uint8) (uint32, uint64, error)
+}
+
+type Accountant struct {
+	// on-chain states
+	reservation        core.ActiveReservation
+	onDemand           core.OnDemandPayment
+	reservationWindow  uint32
+	pricePerChargeable uint32
+	minChargeableSize  uint32
+
+	// local accounting
+	// contains 3 bins; 0 for current bin, 1 for next bin, 2 for overflowed bin
+	binUsages         []uint64
+	cumulativePayment uint64
+	stopRotation      chan struct{}
+
+	accountantSigner *ecdsa.PrivateKey
+}
+
+func NewAccountant(reservation core.ActiveReservation, onDemand core.OnDemandPayment, reservationWindow uint32, pricePerChargeable uint32, minChargeableSize uint32, accountantSigner *ecdsa.PrivateKey) Accountant {
+	a := Accountant{
+		reservation:        reservation,
+		onDemand:           onDemand,
+		reservationWindow:  reservationWindow,
+		pricePerChargeable: pricePerChargeable,
+		minChargeableSize:  minChargeableSize,
+		binUsages:          []uint64{0, 0, 0},
+		cumulativePayment:  0,
+		stopRotation:       make(chan struct{}),
+		accountantSigner:   accountantSigner,
+	}
+	go a.startBinRotation()
+	return a
+}
+
+func (a *Accountant) startBinRotation() {
+	ticker := time.NewTicker(time.Duration(a.reservationWindow) * time.Second)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			a.rotateBins()
+		case <-a.stopRotation:
+			return
+		}
+	}
+}
+
+func (a *Accountant) rotateBins() {
+	// Shift bins: bin_i to bin_{i-1}, add 0 to bin2
+	a.binUsages[0] = a.binUsages[1]
+	a.binUsages[1] = a.binUsages[2]
+	a.binUsages[2] = 0
+}
+
+func (a *Accountant) Stop() {
+	close(a.stopRotation)
+}
+
+// accountant calculates and records payment information
+func (a *Accountant) BlobPaymentInfo(ctx context.Context, dataLength uint64) (uint32, *big.Int, error) {
+	//TODO: do we need to lock the binUsages here in case the blob rotation happens in the middle of the function?
+	binUsage := a.binUsages[0] + dataLength
+	now := time.Now().Unix()
+	currentBinIndex := meterer.GetBinIndex(uint64(now), a.reservationWindow)
+
+	// first attempt to use the active reservation
+	binLimit := a.reservation.SymbolsPerSec * uint64(a.reservationWindow)
+	if binUsage <= binLimit {
+		return currentBinIndex, big.NewInt(0), nil
+	}
+
+	// Allow one overflow when the overflow bin is empty, the current usage and new length are both less than the limit
+	if a.binUsages[2] == 0 && binUsage-dataLength < binLimit && dataLength <= binLimit {
+		a.binUsages[2] += binUsage - binLimit
+		return currentBinIndex, big.NewInt(0), nil
+	}
+
+	// reservation not available, attempt on-demand
+	//todo: rollback if disperser respond with some type of rejection?
+	incrementRequired := a.PaymentCharged(uint32(dataLength))
+	a.cumulativePayment += incrementRequired
+	if a.cumulativePayment <= a.onDemand.CumulativePayment.Uint64() {
+		return 0, big.NewInt(int64(a.cumulativePayment)), nil
+	}
+	return 0, big.NewInt(0), errors.New("Accountant cannot approve payment for this blob")
+}
+
+// accountant provides and records payment information
+func (a *Accountant) AccountBlob(ctx context.Context, dataLength uint64, quorums []uint8) (*core.PaymentMetadata, error) {
+	binIndex, cumulativePayment, err := a.BlobPaymentInfo(ctx, dataLength)
+	if err != nil {
+		return nil, err
+	}
+
+	return &core.PaymentMetadata{
+		AccountID:         string(a.accountantSigner.PublicKey.X.Bytes()),
+		BinIndex:          binIndex,
+		CumulativePayment: cumulativePayment,
+	}, nil
+}
+
+// PaymentCharged returns the chargeable price for a given data length
+func (a *Accountant) PaymentCharged(dataLength uint32) uint64 {
+	return uint64(core.RoundUpDivide(uint(a.BlobSizeCharged(dataLength)*a.pricePerChargeable), uint(a.minChargeableSize)))
+}
+
+// BlobSizeCharged returns the chargeable data length for a given data length
+func (a *Accountant) BlobSizeCharged(dataLength uint32) uint32 {
+	return max(dataLength, uint32(a.minChargeableSize))
+}