cobuild: handle fee payment and set change output

I call payFee before filling the witness in the previous version. The fee estimation is smaller because the tx size is smaller than the final one after adding all the witnesses. I set feeRate to 3000 to work around this.

In this commit, I refactor code to make it possible to create a dummy tx for fee estimation. It's guaranteed that the dummy tx is not less than the final tx.

src/actions/claim.js

@@ -2,12 +2,21 @@
 
 import { claimDao } from "@/lib/cobuild/publishers";
 import { useConfig } from "@/lib/config";
+import { prepareLockActions } from "@/lib/cobuild/lock-actions";
+import { payFee } from "@/lib/cobuild/fee-manager";
 
 export default async function withdraw(from, cell, config) {
   config = config ?? useConfig();
 
   try {
-    const buildingPacket = await claimDao(config)({ from, cell });
+    let buildingPacket = await claimDao(config)({ from, cell });
+    buildingPacket = await payFee(
+      buildingPacket,
+      [{ address: from, feeRate: 1200 }],
+      config,
+    );
+    buildingPacket = prepareLockActions(buildingPacket, config.ckbChainConfig);
+
     return {
       buildingPacket,
     };

src/actions/deposit.js

@@ -3,6 +3,8 @@
 import { parseUnit } from "@ckb-lumos/bi";
 import { depositDao } from "@/lib/cobuild/publishers";
 import { useConfig } from "@/lib/config";
+import { prepareLockActions } from "@/lib/cobuild/lock-actions";
+import { payFee } from "@/lib/cobuild/fee-manager";
 
 export default async function deposit(_prevState, formData, config) {
   config = config ?? useConfig();
@@ -11,7 +13,14 @@ export default async function deposit(_prevState, formData, config) {
   const amount = parseUnit(formData.get("amount"), "ckb");
 
   try {
-    const buildingPacket = await depositDao(config)({ from, amount });
+    let buildingPacket = await depositDao(config)({ from, amount });
+    buildingPacket = await payFee(
+      buildingPacket,
+      [{ address: from, feeRate: 1200 }],
+      config,
+    );
+    buildingPacket = prepareLockActions(buildingPacket, config.ckbChainConfig);
+
     return {
       buildingPacket,
     };

src/actions/transfer.js

@@ -2,6 +2,8 @@
 
 import { parseUnit } from "@ckb-lumos/bi";
 import { transferCkb } from "@/lib/cobuild/publishers";
+import { prepareLockActions } from "@/lib/cobuild/lock-actions";
+import { payFee } from "@/lib/cobuild/fee-manager";
 import { useConfig } from "@/lib/config";
 
 export default async function transfer(_prevState, formData, config) {
@@ -12,11 +14,23 @@ export default async function transfer(_prevState, formData, config) {
   const amount = parseUnit(formData.get("amount"), "ckb");
 
   try {
-    const buildingPacket = await transferCkb(config)({ from, to, amount });
+    let buildingPacket = await transferCkb(config)({
+      from,
+      to,
+      amount,
+    });
+    buildingPacket = await payFee(
+      buildingPacket,
+      [{ address: from, feeRate: 1200 }],
+      config,
+    );
+    buildingPacket = prepareLockActions(buildingPacket, config.ckbChainConfig);
+
     return {
       buildingPacket,
     };
   } catch (err) {
+    console.error(err.stack);
     return {
       error: err.toString(),
     };

src/actions/withdraw.js

@@ -2,12 +2,21 @@
 
 import { withdrawDao } from "@/lib/cobuild/publishers";
 import { useConfig } from "@/lib/config";
+import { prepareLockActions } from "@/lib/cobuild/lock-actions";
+import { payFee } from "@/lib/cobuild/fee-manager";
 
 export default async function withdraw(from, cell, config) {
   config = config ?? useConfig();
 
   try {
-    const buildingPacket = await withdrawDao(config)({ from, cell });
+    let buildingPacket = await withdrawDao(config)({ from, cell });
+    buildingPacket = await payFee(
+      buildingPacket,
+      [{ address: from, feeRate: 1200 }],
+      config,
+    );
+    buildingPacket = prepareLockActions(buildingPacket, config.ckbChainConfig);
+
     return {
       buildingPacket,
     };

src/app/accounts/[address]/sign-form.js

@@ -8,7 +8,6 @@ import * as joyid from "@/lib/wallet/joyid";
 import SubmitButton from "@/components/submit-button";
 import BuildingPacketReview from "@/lib/cobuild/react/building-packet-review";
 import {
-  prepareLockActions,
   findLockActionByLockScript,
   finalizeWitnesses,
 } from "@/lib/cobuild/lock-actions";
@@ -25,15 +24,8 @@ export default function SignForm({
   onCancel,
 }) {
   const [error, setError] = useState();
-  const preparedBuildingPacket = prepareLockActions(
-    buildingPacket,
-    ckbChainConfig,
-  );
   const lockScript = addressToScript(address, { config: ckbChainConfig });
-  const lockAction = findLockActionByLockScript(
-    preparedBuildingPacket,
-    lockScript,
-  );
+  const lockAction = findLockActionByLockScript(buildingPacket, lockScript);
   const lockActionData = GeneralLockAction.unpack(lockAction.data);
   const sign = async () => {
     try {
@@ -64,7 +56,7 @@ export default function SignForm({
         </Button>
       </form>
       <BuildingPacketReview
-        buildingPacket={preparedBuildingPacket}
+        buildingPacket={buildingPacket}
         lockActionData={lockActionData}
       />
     </>

src/lib/cobuild/fee-manager.js

@@ -0,0 +1,67 @@
+import { bytes } from "@ckb-lumos/codec";
+
+import payFeeWithBuildingPacket from "../lumos-adapter/pay-fee-with-building-packet";
+import * as generalLockActions from "./general-lock-actions";
+import { finalizeWitnesses } from "./lock-actions";
+import { groupByLock } from "./script-group";
+
+// feePayments: [{address, fee?, feeRate?}]
+export async function payFee(buildingPacket, feePayments, config) {
+  const groups = groupByLock(buildingPacket.value.resolvedInputs.outputs);
+
+  // Rember fields that should be restored
+  const witnesses = buildingPacket.value.payload.witnesses;
+
+  const buildingPacketWillPayFee = finalizeWitnesses(
+    Object.entries(groups).reduce(
+      (acc, [scriptHash, inputs]) =>
+        storeWitnessForFeeEstimation(
+          acc,
+          scriptHash,
+          inputs.map((e) => e[0]),
+          config.ckbChainConfig,
+        ),
+      buildingPacket,
+    ),
+  );
+
+  const buildingPacketHavePaidFee = await payFeeWithBuildingPacket(
+    buildingPacketWillPayFee,
+    feePayments,
+    config,
+  );
+
+  return {
+    type: buildingPacketHavePaidFee.type,
+    value: {
+      ...buildingPacketHavePaidFee.value,
+      payload: {
+        ...buildingPacketHavePaidFee.value.payload,
+        witnesses,
+      },
+    },
+  };
+}
+
+function storeWitnessForFeeEstimation(
+  buildingPacket,
+  scriptHash,
+  inputIndices,
+  ckbChainConfig,
+) {
+  const script =
+    buildingPacket.value.resolvedInputs.outputs[inputIndices[0]].lock;
+  if (script.codeHash === ckbChainConfig.SCRIPTS.JOYID_COBUILD_POC.CODE_HASH) {
+    return generalLockActions.storeWitnessForFeeEstimation(
+      buildingPacket,
+      scriptHash,
+      inputIndices,
+      // Variable length, but 500 is usually enough.
+      () => bytes.hexify(new Uint8Array(500)),
+    );
+  }
+
+  throw new Error(
+    `NotSupportedLock: codeHash=${script.codeHash} hashType=${script.hashType}`,
+  );
+}

src/lib/cobuild/general-lock-actions.js

@@ -48,6 +48,24 @@ export function prepareLockAction(
   };
 }
 
+export function storeWitnessForFeeEstimation(
+  buildingPacket,
+  scriptHash,
+  inputIndices,
+  createSealPlaceHolder,
+) {
+  buildingPacket = prepareLockAction(
+    buildingPacket,
+    scriptHash,
+    inputIndices,
+    createSealPlaceHolder,
+  );
+  const lockAction = buildingPacket.value.lockActions.find(
+    (action) => action.scriptHash === scriptHash,
+  );
+  return applyLockAction(buildingPacket, lockAction, createSealPlaceHolder());
+}
+
 export function applyLockAction(buildingPacket, lockAction, seal) {
   const witnesses = [...buildingPacket.value.payload.witnesses];
   const { witnessStore } = GeneralLockAction.unpack(lockAction.data);

src/lib/cobuild/lock-actions.js

@@ -2,6 +2,7 @@ import { utils as lumosBaseUtils } from "@ckb-lumos/base";
 
 import * as generalLockActions from "./general-lock-actions";
 import { parseWitnessType } from "./types";
+import { groupByLock } from "./script-group";
 
 const { computeScriptHash } = lumosBaseUtils;
 
@@ -66,12 +67,6 @@ export function findLockActionByLockScript(buildingPacket, lockScript) {
   );
 }
 
-function groupByLock(cellOutputs) {
-  return Object.groupBy(cellOutputs.entries(), ([_i, v]) =>
-    computeScriptHash(v.lock),
-  );
-}
-
 function dispatchLockActions(
   buildingPacket,
   scriptHash,

src/lib/cobuild/script-group.js

@@ -0,0 +1,8 @@
+import { utils as lumosBaseUtils } from "@ckb-lumos/base";
+const { computeScriptHash } = lumosBaseUtils;
+
+export function groupByLock(cellOutputs) {
+  return Object.groupBy(cellOutputs.entries(), ([_i, v]) =>
+    computeScriptHash(v.lock),
+  );
+}

src/lib/lumos-adapter/create-building-packet-from-skeleton.js

@@ -1,9 +1,12 @@
 import { createTransactionFromSkeleton } from "@ckb-lumos/helpers";
 
-export default function createBuildingPacketFromSkeleton(txSkeleton) {
+export default function createBuildingPacketFromSkeleton(
+  txSkeleton,
+  changeOutput,
+) {
   const resolvedInputs = {
     outputs: txSkeleton.inputs.map((cell) => cell.cellOutput).toJSON(),
-    outputData: txSkeleton.inputs.map((cell) => cell.data).toJSON(),
+    outputsData: txSkeleton.inputs.map((cell) => cell.data).toJSON(),
   };
   const payload = createTransactionFromSkeleton(txSkeleton);
   return {
@@ -12,11 +15,11 @@ export default function createBuildingPacketFromSkeleton(txSkeleton) {
       message: {
         actions: [],
       },
-      payload,
-      resolvedInputs,
-      changeOutput: null,
       scriptInfos: [],
       lockActions: [],
+      payload,
+      resolvedInputs,
+      changeOutput,
     },
   };
 }

src/lib/lumos-adapter/create-lumos-ckb-builder.js

@@ -10,19 +10,6 @@ import {
   packDaoWitnessArgs,
 } from "../dao";
 
-// **Attention:** There's no witnesses set yet, so I set fee rate to 3000 to hope that the final tx fee rate will be larger than 1000.
-async function payFee(txSkeleton, from, ckbChainConfig) {
-  return await commonScripts.payFeeByFeeRate(
-    txSkeleton,
-    [from],
-    3000,
-    undefined,
-    {
-      config: ckbChainConfig,
-    },
-  );
-}
-
 function buildCellDep(scriptInfo) {
   return {
     outPoint: {
@@ -33,6 +20,11 @@ function buildCellDep(scriptInfo) {
   };
 }
 
+function useLastOutputAsChangeOutput(txSkeleton) {
+  const size = txSkeleton.get("outputs").size;
+  return size > 1 ? size - 1 : null;
+}
+
 export default function createLumosCkbBuilder({ ckbRpcUrl, ckbChainConfig }) {
   initLumosCommonScripts(ckbChainConfig);
   const rpc = new RPC(ckbRpcUrl);
@@ -56,8 +48,11 @@ export default function createLumosCkbBuilder({ ckbRpcUrl, ckbChainConfig }) {
         },
       );
 
-      txSkeleton = await payFee(txSkeleton, from, ckbChainConfig);
-      return createBuildingPacketFromSkeleton(txSkeleton);
+      // lumos always add the target output first
+      return createBuildingPacketFromSkeleton(
+        txSkeleton,
+        useLastOutputAsChangeOutput(txSkeleton),
+      );
     },
 
     depositDao: async function ({ from, amount }) {
@@ -78,8 +73,10 @@ export default function createLumosCkbBuilder({ ckbRpcUrl, ckbChainConfig }) {
         { config: ckbChainConfig },
       );
 
-      txSkeleton = await payFee(txSkeleton, from, ckbChainConfig);
-      return createBuildingPacketFromSkeleton(txSkeleton);
+      return createBuildingPacketFromSkeleton(
+        txSkeleton,
+        useLastOutputAsChangeOutput(txSkeleton),
+      );
     },
 
     withdrawDao: async function ({ from, cell }) {
@@ -96,8 +93,10 @@ export default function createLumosCkbBuilder({ ckbRpcUrl, ckbChainConfig }) {
         config: ckbChainConfig,
       });
 
-      txSkeleton = await payFee(txSkeleton, from, ckbChainConfig);
-      return createBuildingPacketFromSkeleton(txSkeleton);
+      return createBuildingPacketFromSkeleton(
+        txSkeleton,
+        useLastOutputAsChangeOutput(txSkeleton),
+      );
     },
 
     claimDao: async function ({ from, cell }) {
@@ -157,8 +156,8 @@ export default function createLumosCkbBuilder({ ckbRpcUrl, ckbChainConfig }) {
 
       let txSkeleton = txSkeletonMutable.asImmutable();
 
-      txSkeleton = await payFee(txSkeleton, from, ckbChainConfig);
-      return createBuildingPacketFromSkeleton(txSkeleton);
+      // Allow pay fee from the unlocked cell directly.
+      return createBuildingPacketFromSkeleton(txSkeleton, 0);
     },
   };
 }

src/lib/lumos-adapter/init-lumos-common-scripts.js

@@ -77,6 +77,7 @@ export function buildLockInfo(ckbChainConfig, scriptInfo) {
         //===========================
         // 1.Add inputCell to txSkeleton
         txMutable.update("inputs", (inputs) => inputs.push(inputCell));
+        txMutable.update("witnesses", (witnesses) => witnesses.push("0x"));
 
         // 2. Add output. The function `lumos.commons.common.transfer` will scan outputs for available balance for each account.
         const outputCell = {