disperser meterer for payments

api/clients/accountant.go

@@ -0,0 +1,128 @@
+package clients
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"errors"
+	"fmt"
+	"math/big"
+	"time"
+
+	"github.com/Layr-Labs/eigenda/core"
+	"github.com/Layr-Labs/eigenda/disperser/meterer"
+	"github.com/ethereum/go-ethereum/common"
+)
+
+type IAccountant interface {
+	AccountBlob(ctx context.Context, data []byte, quorums []uint8) (uint32, uint64, error)
+}
+
+type Accountant struct {
+	// on-chain states
+	reservation        meterer.ActiveReservation
+	onDemand           meterer.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{}
+
+	domainSigner     *meterer.EIP712Signer
+	accountantSigner *ecdsa.PrivateKey
+}
+
+func NewAccountant(reservation meterer.ActiveReservation, onDemand meterer.OnDemandPayment, reservationWindow uint32, pricePerChargeable uint32, minChargeableSize uint32, accountantSigner *ecdsa.PrivateKey) Accountant {
+	//todo: refactor signing strategy; EIP712 -> serializer? private key -> Local blob request signer?
+	chainID := big.NewInt(17000)
+	verifyingContract := common.HexToAddress("0x1234000000000000000000000000000000000000")
+
+	a := Accountant{
+		reservation:        reservation,
+		onDemand:           onDemand,
+		reservationWindow:  reservationWindow,
+		pricePerChargeable: pricePerChargeable,
+		minChargeableSize:  minChargeableSize,
+		binUsages:          []uint64{0, 0, 0},
+		cumulativePayment:  0,
+		stopRotation:       make(chan struct{}),
+		domainSigner:       meterer.NewEIP712Signer(chainID, verifyingContract),
+		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, uint64, error) {
+	//TODO: do we need to lock the binUsages here in case the rotation happens in the middle of the function?
+	currentBinUsage := a.binUsages[0]
+	currentBinIndex := meterer.GetCurrentBinIndex(a.reservationWindow)
+
+	// first attempt to use the active reservation
+	if currentBinUsage+dataLength <= a.reservation.DataRate {
+		a.binUsages[0] += dataLength
+		return currentBinIndex, 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 && currentBinUsage < a.reservation.DataRate && dataLength <= a.reservation.DataRate {
+		fmt.Println("in overflow:", currentBinUsage, dataLength, a.reservation.DataRate)
+		a.binUsages[0] += dataLength
+		a.binUsages[2] += currentBinUsage + dataLength - a.reservation.DataRate
+		return currentBinIndex, 0, nil
+	}
+
+	// reservation not available, attempt on-demand
+	//todo: rollback if disperser respond with some type of rejection?
+	incrementRequired := uint64(max(uint32(dataLength), a.minChargeableSize)) * uint64(a.pricePerChargeable) / uint64(a.minChargeableSize)
+	a.cumulativePayment += incrementRequired
+	if a.cumulativePayment <= uint64(a.onDemand.CumulativePayment) {
+		return 0, a.cumulativePayment, nil
+	}
+	return 0, 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) (*meterer.BlobHeader, error) {
+	binIndex, cumulativePayment, err := a.BlobPaymentInfo(ctx, dataLength)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO: have client first generate a commitment, then pass it here
+	commitment := core.NewG1Point(big.NewInt(0), big.NewInt(1))
+	header, err := meterer.ConstructBlobHeader(a.domainSigner, binIndex, cumulativePayment, *commitment, uint32(dataLength), quorums, a.accountantSigner)
+	if err != nil {
+		return nil, err
+	}
+	return header, nil
+}