fix: add shared guard to prevent zero pricing (#237)

* fix: add shared guard to prevent zero pricePerTiBPerEpoch in capacity and storage calculations

- Introduced assertPriceNonZero() in core/utils/validate-pricing.ts
- Integrated into calculateActualCapacity() and calculateStorageFromUSDFC()
- Updated tests to expect throws on zero pricing
- Prevents Infinity / unsafe deposit calculations

* Update src/core/utils/validate-pricing.ts

Co-authored-by: Copilot <[email protected]>

* linting

---------

Co-authored-by: Russell Dempsey <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

src/core/payments/index.ts

@@ -18,6 +18,7 @@
 import { SIZE_CONSTANTS, type Synapse, TIME_CONSTANTS, TOKENS } from '@filoz/synapse-sdk'
 import { ethers } from 'ethers'
 import { isSessionKeyMode } from '../synapse/index.js'
+import { assertPriceNonZero } from '../utils/validate-pricing.js'
 import {
   BUFFER_DENOMINATOR,
   BUFFER_NUMERATOR,
@@ -508,7 +509,7 @@ export function calculateStorageAllowances(storageTiB: number, pricePerTiBPerEpo
  * @returns Storage capacity in TiB that can be supported
  */
 export function calculateActualCapacity(rateAllowance: bigint, pricePerTiBPerEpoch: bigint): number {
-  if (pricePerTiBPerEpoch === 0n) return 0
+  assertPriceNonZero(pricePerTiBPerEpoch)
 
   // Calculate TiB capacity from rate allowance
   const scaledQuotient = (rateAllowance * STORAGE_SCALE_MAX_BI) / pricePerTiBPerEpoch
@@ -536,7 +537,7 @@ export function calculateActualCapacity(rateAllowance: bigint, pricePerTiBPerEpo
  * @returns Storage capacity in TiB/month
  */
 export function calculateStorageFromUSDFC(usdfcAmount: bigint, pricePerTiBPerEpoch: bigint): number {
-  if (pricePerTiBPerEpoch === 0n) return 0
+  assertPriceNonZero(pricePerTiBPerEpoch)
 
   // Calculate how much this covers for lockup
   const epochsInLockupDays = BigInt(DEFAULT_LOCKUP_DAYS) * TIME_CONSTANTS.EPOCHS_PER_DAY

src/core/utils/validate-pricing.ts

@@ -0,0 +1,12 @@
+/**
+ * Validation utility for core financial calculations.
+ * Keeps pricing inputs non-zero and positive.
+ *
+ * @param pricePerTiBPerEpoch - Current pricing from storage service
+ */
+
+export function assertPriceNonZero(pricePerTiBPerEpoch: bigint): void {
+  if (pricePerTiBPerEpoch <= 0n) {
+    throw new Error('Invalid pricePerTiBPerEpoch: must be positive non-zero value')
+  }
+}

src/test/unit/payments-setup.test.ts

@@ -11,6 +11,7 @@ import {
   setServiceApprovals,
 } from '../../core/payments/index.js'
 import { formatFIL, formatUSDFC } from '../../core/utils/format.js'
+import { assertPriceNonZero } from '../../core/utils/validate-pricing.js'
 import { parseStorageAllowance } from '../../payments/setup.js'
 
 // Mock Synapse SDK
@@ -57,6 +58,20 @@ vi.mock('@filoz/synapse-sdk', () => {
   }
 })
 
+describe('assertPriceNonZero', () => {
+  it('throws when pricePerTiBPerEpoch is zero', () => {
+    expect(() => assertPriceNonZero(0n)).toThrow('Invalid pricePerTiBPerEpoch: must be positive non-zero value')
+  })
+
+  it('throws when pricePerTiBPerEpoch is negative', () => {
+    expect(() => assertPriceNonZero(-10n)).toThrow('Invalid pricePerTiBPerEpoch: must be positive non-zero value')
+  })
+
+  it('does not throw for positive price', () => {
+    expect(() => assertPriceNonZero(1n)).not.toThrow()
+  })
+})
+
 describe('Payment Setup Tests', () => {
   let mockSynapse: any
   let mockProvider: any
@@ -342,9 +357,10 @@ describe('Payment Setup Tests', () => {
       expect(capacityTiB).toBeCloseTo(expectedTiB, 5)
     })
 
-    it('should handle zero price gracefully', () => {
-      const capacityTiB = calculateActualCapacity(ethers.parseUnits('1', 18), 0n)
-      expect(capacityTiB).toBe(0)
+    it('throws when pricePerTiBPerEpoch is zero', () => {
+      expect(() => calculateActualCapacity(ethers.parseUnits('1', 18), 0n)).toThrow(
+        'Invalid pricePerTiBPerEpoch: must be positive non-zero value'
+      )
     })
   })
 
@@ -360,19 +376,10 @@ describe('Payment Setup Tests', () => {
       expect(capacityTiB).toBeCloseTo(expectedTiB, 5)
     })
 
-    it('should handle zero price gracefully', () => {
-      const capacityTiB = calculateStorageFromUSDFC(ethers.parseUnits('1', 18), 0n)
-      expect(capacityTiB).toBe(0)
-    })
-
-    // FIXME: if pricePerTiBPerEpoch is 0, shouldn't we throw an error or return Infinity?
-    // See https://github.com/filecoin-project/filecoin-pin/issues/38
-    it('returns 0 if pricePerTiBPerEpoch is 0', () => {
-      const usdfcAmount = ethers.parseUnits('1', 18)
-      const pricePerTiBPerEpoch = ethers.parseUnits('0', 18)
-      const capacityTiB = calculateStorageFromUSDFC(usdfcAmount, pricePerTiBPerEpoch)
-
-      expect(capacityTiB).toBe(0)
+    it('throws when pricePerTiBPerEpoch is zero', () => {
+      expect(() => calculateStorageFromUSDFC(ethers.parseUnits('1', 18), 0n)).toThrow(
+        'Invalid pricePerTiBPerEpoch: must be positive non-zero value'
+      )
     })
 
     it('returns 0 if usdfcAmount is 0', () => {