feat(tempo): add split payments for charge

.changeset/quiet-cooks-smile.md

@@ -0,0 +1,5 @@
+---
+'mppx': minor
+---
+
+Add split-payment support to Tempo charge requests, including client transaction construction and stricter server verification for split transfers.

src/tempo/Methods.test.ts

@@ -51,6 +51,85 @@ describe('charge', () => {
     expect(result.success).toBe(true)
   })
 
+  test('schema: validates request with splits', () => {
+    const result = Methods.charge.schema.request.safeParse({
+      amount: '1',
+      currency: '0x20c0000000000000000000000000000000000001',
+      decimals: 6,
+      recipient: '0x1234567890abcdef1234567890abcdef12345678',
+      splits: [
+        {
+          amount: '0.25',
+          recipient: '0xabcdefabcdefabcdefabcdefabcdefabcdefabcd',
+        },
+        {
+          amount: '0.1',
+          memo: '0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef',
+          recipient: '0xbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb',
+        },
+      ],
+    })
+    expect(result.success).toBe(true)
+    if (!result.success) return
+
+    expect(result.data.methodDetails?.splits).toEqual([
+      {
+        amount: '250000',
+        recipient: '0xabcdefabcdefabcdefabcdefabcdefabcdefabcd',
+      },
+      {
+        amount: '100000',
+        memo: '0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef',
+        recipient: '0xbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb',
+      },
+    ])
+  })
+
+  test('schema: rejects empty splits', () => {
+    const result = Methods.charge.schema.request.safeParse({
+      amount: '1',
+      currency: '0x20c0000000000000000000000000000000000001',
+      decimals: 6,
+      recipient: '0x1234567890abcdef1234567890abcdef12345678',
+      splits: [],
+    })
+    expect(result.success).toBe(false)
+  })
+
+  test('schema: rejects more than 10 splits', () => {
+    const result = Methods.charge.schema.request.safeParse({
+      amount: '11',
+      currency: '0x20c0000000000000000000000000000000000001',
+      decimals: 6,
+      recipient: '0x1234567890abcdef1234567890abcdef12345678',
+      splits: Array.from({ length: 11 }, (_, index) => ({
+        amount: '0.1',
+        recipient: `0x${(index + 1).toString(16).padStart(40, '0')}`,
+      })),
+    })
+    expect(result.success).toBe(false)
+  })
+
+  test('schema: rejects split totals greater than or equal to amount', () => {
+    const result = Methods.charge.schema.request.safeParse({
+      amount: '1',
+      currency: '0x20c0000000000000000000000000000000000001',
+      decimals: 6,
+      recipient: '0x1234567890abcdef1234567890abcdef12345678',
+      splits: [
+        {
+          amount: '0.5',
+          recipient: '0xabcdefabcdefabcdefabcdefabcdefabcdefabcd',
+        },
+        {
+          amount: '0.5',
+          recipient: '0xbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb',
+        },
+      ],
+    })
+    expect(result.success).toBe(false)
+  })
+
   test('schema: rejects invalid request', () => {
     const result = Methods.charge.schema.request.safeParse({
       amount: '1',

src/tempo/Methods.ts

@@ -4,6 +4,12 @@ import { parseUnits } from 'viem'
 import * as Method from '../Method.js'
 import * as z from '../zod.js'
 
+const split = z.object({
+  amount: z.amount(),
+  memo: z.optional(z.hash()),
+  recipient: z.string(),
+})
+
 /**
  * Tempo charge intent for one-time TIP-20 token transfers.
  *
@@ -20,31 +26,58 @@ export const charge = Method.from({
       ]),
     },
     request: z.pipe(
-      z.object({
-        amount: z.amount(),
-        chainId: z.optional(z.number()),
-        currency: z.string(),
-        decimals: z.number(),
-        description: z.optional(z.string()),
-        externalId: z.optional(z.string()),
-        feePayer: z.optional(
-          z.pipe(
-            z.union([z.boolean(), z.custom<Account>()]),
-            z.transform((v): boolean => (typeof v === 'object' ? true : v)),
+      z
+        .object({
+          amount: z.amount(),
+          chainId: z.optional(z.number()),
+          currency: z.string(),
+          decimals: z.number(),
+          description: z.optional(z.string()),
+          externalId: z.optional(z.string()),
+          feePayer: z.optional(
+            z.pipe(
+              z.union([z.boolean(), z.custom<Account>()]),
+              z.transform((v): boolean => (typeof v === 'object' ? true : v)),
+            ),
           ),
+          memo: z.optional(z.hash()),
+          recipient: z.optional(z.string()),
+          splits: z.optional(z.array(split).check(z.minLength(1), z.maxLength(10))),
+        })
+        .check(
+          z.refine(({ amount, decimals, splits }) => {
+            if (!splits) return true
+
+            const totalAmount = parseUnits(amount, decimals)
+            const splitTotal = splits.reduce(
+              (sum, split) => sum + parseUnits(split.amount, decimals),
+              0n,
+            )
+
+            return (
+              splits.every((split) => parseUnits(split.amount, decimals) > 0n) &&
+              splitTotal < totalAmount
+            )
+          }, 'Invalid splits'),
         ),
-        memo: z.optional(z.hash()),
-        recipient: z.optional(z.string()),
-      }),
-      z.transform(({ amount, chainId, decimals, feePayer, memo, ...rest }) => ({
+      z.transform(({ amount, chainId, decimals, feePayer, memo, splits, ...rest }) => ({
         ...rest,
         amount: parseUnits(amount, decimals).toString(),
-        ...(chainId !== undefined || feePayer !== undefined || memo !== undefined
+        ...(chainId !== undefined ||
+        feePayer !== undefined ||
+        memo !== undefined ||
+        splits !== undefined
           ? {
               methodDetails: {
                 ...(chainId !== undefined && { chainId }),
                 ...(feePayer !== undefined && { feePayer }),
                 ...(memo !== undefined && { memo }),
+                ...(splits !== undefined && {
+                  splits: splits.map((split) => ({
+                    ...split,
+                    amount: parseUnits(split.amount, decimals).toString(),
+                  })),
+                }),
               },
             }
           : {}),

src/tempo/client/Charge.ts

@@ -11,6 +11,7 @@ import * as Client from '../../viem/Client.js'
 import * as z from '../../zod.js'
 import * as Attribution from '../Attribution.js'
 import * as AutoSwap from '../internal/auto-swap.js'
+import * as Charge_internal from '../internal/charge.js'
 import * as defaults from '../internal/defaults.js'
 import * as Methods from '../Methods.js'
 
@@ -54,18 +55,37 @@ export function charge(parameters: charge.Parameters = {}) {
       const { request } = challenge
       const { amount, methodDetails } = request
       const currency = request.currency as Address
-      const recipient = request.recipient as Address
+
+      if (parameters.expectedRecipients) {
+        const allowed = new Set(parameters.expectedRecipients.map((a) => a.toLowerCase()))
+        const splits = methodDetails?.splits as readonly { recipient: string }[] | undefined
+        if (splits) {
+          for (const split of splits) {
+            if (!allowed.has(split.recipient.toLowerCase()))
+              throw new Error(`Unexpected split recipient: ${split.recipient}`)
+          }
+        }
+      }
 
       const memo = methodDetails?.memo
         ? (methodDetails.memo as Hex.Hex)
         : Attribution.encode({ serverId: challenge.realm, clientId })
-
-      const transferCall = Actions.token.transfer.call({
-        amount: BigInt(amount),
-        memo,
-        to: recipient,
-        token: currency,
+      const transfers = Charge_internal.getTransfers({
+        amount,
+        methodDetails: {
+          ...methodDetails,
+          memo,
+        },
+        recipient: request.recipient as Address,
       })
+      const transferCalls = transfers.map((transfer) =>
+        Actions.token.transfer.call({
+          amount: BigInt(transfer.amount),
+          ...(transfer.memo && { memo: transfer.memo as Hex.Hex }),
+          to: transfer.recipient as Address,
+          token: currency,
+        }),
+      )
 
       const autoSwap = AutoSwap.resolve(
         context?.autoSwap ?? parameters.autoSwap,
@@ -82,7 +102,7 @@ export function charge(parameters: charge.Parameters = {}) {
           })
         : undefined
 
-      const calls = [...(swapCalls ?? []), transferCall]
+      const calls = [...(swapCalls ?? []), ...transferCalls]
 
       if (mode === 'push') {
         const { receipts } = await sendCallsSync(client, {
@@ -99,11 +119,19 @@ export function charge(parameters: charge.Parameters = {}) {
         })
       }
 
+      const validBefore = (() => {
+        const defaultExpiry = Math.floor(Date.now() / 1000) + 25
+        if (!challenge.expires) return defaultExpiry
+        const challengeExpiry = Math.floor(new Date(challenge.expires).getTime() / 1000)
+        return Math.min(defaultExpiry, challengeExpiry)
+      })()
+
       const prepared = await prepareTransactionRequest(client, {
         account,
         calls,
         ...(methodDetails?.feePayer && { feePayer: true }),
         nonceKey: 'expiring',
+        validBefore,
       } as never)
       // FIXME: figure out gas estimation issue for fee payer tx
       prepared.gas = prepared.gas! + 5_000n
@@ -131,6 +159,11 @@ export declare namespace charge {
     autoSwap?: AutoSwap | undefined
     /** Client identifier used to derive the client fingerprint in attribution memos. */
     clientId?: string | undefined
+    /**
+     * Allowlist of expected split recipient addresses. When set, the client
+     * rejects any challenge whose split recipients are not in this list.
+     */
+    expectedRecipients?: readonly string[] | undefined
     /**
      * Controls how the charge transaction is submitted.
      *

src/tempo/internal/charge.ts

@@ -0,0 +1,41 @@
+export type Split = {
+  amount: string
+  memo?: string | undefined
+  recipient: string
+}
+
+export type Transfer = {
+  amount: string
+  memo?: string | undefined
+  recipient: string
+}
+
+export function getTransfers(request: {
+  amount: string
+  methodDetails?: { memo?: string | undefined; splits?: readonly Split[] | undefined }
+  recipient: string
+}): Transfer[] {
+  const totalAmount = BigInt(request.amount)
+  const splits = request.methodDetails?.splits ?? []
+
+  const splitTotal = splits.reduce((sum, split) => sum + BigInt(split.amount), 0n)
+  if (splitTotal >= totalAmount)
+    throw new Error('Invalid charge request: split total must be less than total amount.')
+
+  const primaryAmount = totalAmount - splitTotal
+  if (primaryAmount <= 0n)
+    throw new Error('Invalid charge request: primary transfer amount must be positive.')
+
+  return [
+    {
+      amount: primaryAmount.toString(),
+      memo: request.methodDetails?.memo,
+      recipient: request.recipient,
+    },
+    ...splits.map((split) => ({
+      amount: split.amount,
+      memo: split.memo,
+      recipient: split.recipient,
+    })),
+  ]
+}

src/tempo/internal/fee-payer.test.ts

@@ -70,17 +70,7 @@ describe('validateCalls', () => {
     ).not.toThrow()
   })
 
-  test('error: rejects empty calls', () => {
-    expect(() => validateCalls([], details)).toThrow(FeePayerValidationError)
-  })
-
-  test('error: rejects unknown selector', () => {
-    expect(() => validateCalls([{ data: '0xdeadbeef' as `0x${string}` }], details)).toThrow(
-      'disallowed call pattern',
-    )
-  })
-
-  test('error: rejects extra calls beyond allowed patterns', () => {
+  test('accepts multiple transfers after swap prefix', () => {
     const swapSelector = Selectors.swapExactAmountOut
     expect(() =>
       validateCalls(
@@ -100,19 +90,48 @@ describe('validateCalls', () => {
             data: encodeFunctionData({
               abi: Abis.tip20,
               functionName: 'transfer',
-              args: [bogus, 100n],
+              args: [bogus, 90n],
             }),
           },
           {
             data: encodeFunctionData({
               abi: Abis.tip20,
-              functionName: 'transfer',
-              args: [bogus, 100n],
+              functionName: 'transferWithMemo',
+              args: [
+                '0x0000000000000000000000000000000000000002',
+                10n,
+                '0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef',
+              ],
             }),
           },
         ],
         details,
       ),
+    ).not.toThrow()
+  })
+
+  test('error: rejects empty calls', () => {
+    expect(() => validateCalls([], details)).toThrow(FeePayerValidationError)
+  })
+
+  test('error: rejects unknown selector', () => {
+    expect(() => validateCalls([{ data: '0xdeadbeef' as `0x${string}` }], details)).toThrow(
+      'disallowed call pattern',
+    )
+  })
+
+  test('error: rejects more than 11 transfers', () => {
+    expect(() =>
+      validateCalls(
+        Array.from({ length: 12 }, (_, index) => ({
+          data: encodeFunctionData({
+            abi: Abis.tip20,
+            functionName: 'transfer',
+            args: [`0x${(index + 1).toString(16).padStart(40, '0')}`, 100n],
+          }),
+        })),
+        details,
+      ),
     ).toThrow('disallowed call pattern')
   })