feat(cip2): add support for custom random fn

Author: mkazlauskas

Diff for: packages/cip2/src/RoundRobinRandomImprove/change.ts

@@ -14,6 +14,7 @@ interface ChangeComputationArgs {
   estimateTxFee: EstimateTxFeeWithOriginalOutputs;
   computeMinimumCoinQuantity: ComputeMinimumCoinQuantity;
   tokenBundleSizeExceedsLimit: TokenBundleSizeExceedsLimit;
+  random: typeof Math.random;
 }
 
 interface ChangeComputationResult {
@@ -167,10 +168,13 @@ const computeRequestedAssetChangeBundles = (
  * Picks one UTxO from remaining set and puts it to the selected set.
  * Precondition: utxoRemaining.length > 0
  */
-const pickExtraRandomUtxo = ({ utxoRemaining, utxoSelected }: UtxoSelection): UtxoSelection => {
+const pickExtraRandomUtxo = (
+  { utxoRemaining, utxoSelected }: UtxoSelection,
+  random: typeof Math.random
+): UtxoSelection => {
   const remainingUtxoOfOnlyCoin = utxoRemaining.filter(([_, { value }]) => !value.assets);
   const pickFrom = remainingUtxoOfOnlyCoin.length > 0 ? remainingUtxoOfOnlyCoin : utxoRemaining;
-  const pickIdx = Math.floor(Math.random() * pickFrom.length);
+  const pickIdx = Math.floor(random() * pickFrom.length);
   const newUtxoSelected = [...utxoSelected, pickFrom[pickIdx]];
   const originalIdx = utxoRemaining.indexOf(pickFrom[pickIdx]);
   const newUtxoRemaining = [...utxoRemaining.slice(0, originalIdx), ...utxoRemaining.slice(originalIdx + 1)];
@@ -218,6 +222,7 @@ const computeChangeBundles = ({
   uniqueOutputAssetIDs,
   implicitCoin,
   computeMinimumCoinQuantity,
+  random,
   fee = 0n
 }: {
   utxoSelection: UtxoSelection;
@@ -226,6 +231,7 @@ const computeChangeBundles = ({
   implicitCoin: Required<Cardano.ImplicitCoin>;
   computeMinimumCoinQuantity: ComputeMinimumCoinQuantity;
   fee?: bigint;
+  random: typeof Math.random;
 }): UtxoSelection & { changeBundles: Cardano.Value[] } => {
   const requestedAssetChangeBundles = computeRequestedAssetChangeBundles(
     utxoSelection.utxoSelected,
@@ -251,8 +257,9 @@ const computeChangeBundles = ({
         fee,
         implicitCoin,
         outputValues,
+        random,
         uniqueOutputAssetIDs,
-        utxoSelection: pickExtraRandomUtxo(utxoSelection)
+        utxoSelection: pickExtraRandomUtxo(utxoSelection, random)
       });
     }
     // This is not a great error type for this, because the spec says
@@ -294,12 +301,14 @@ export const computeChangeAndAdjustForFee = async ({
   outputValues,
   uniqueOutputAssetIDs,
   implicitCoin,
+  random,
   utxoSelection
 }: ChangeComputationArgs): Promise<ChangeComputationResult> => {
   const changeInclFee = computeChangeBundles({
     computeMinimumCoinQuantity,
     implicitCoin,
     outputValues,
+    random,
     uniqueOutputAssetIDs,
     utxoSelection
   });
@@ -325,9 +334,10 @@ export const computeChangeAndAdjustForFee = async ({
       estimateTxFee,
       implicitCoin,
       outputValues,
+      random,
       tokenBundleSizeExceedsLimit,
       uniqueOutputAssetIDs,
-      utxoSelection: pickExtraRandomUtxo(changeInclFee)
+      utxoSelection: pickExtraRandomUtxo(changeInclFee, random)
     });
   }
 
@@ -336,6 +346,7 @@ export const computeChangeAndAdjustForFee = async ({
     fee,
     implicitCoin,
     outputValues,
+    random,
     uniqueOutputAssetIDs,
     utxoSelection: { utxoRemaining: changeInclFee.utxoRemaining, utxoSelected: changeInclFee.utxoSelected }
   });

Diff for: packages/cip2/src/RoundRobinRandomImprove/index.ts

@@ -5,7 +5,13 @@ import { computeChangeAndAdjustForFee } from './change';
 import { cslUtil } from '@cardano-sdk/core';
 import { roundRobinSelection } from './roundRobin';
 
-export const roundRobinRandomImprove = (): InputSelector => ({
+interface RoundRobinRandomImproveOptions {
+  random?: typeof Math.random;
+}
+
+export const roundRobinRandomImprove = ({
+  random = Math.random
+}: RoundRobinRandomImproveOptions = {}): InputSelector => ({
   select: async ({
     utxo: utxoSet,
     outputs: outputSet,
@@ -23,6 +29,7 @@ export const roundRobinRandomImprove = (): InputSelector => ({
     const roundRobinSelectionResult = roundRobinSelection({
       implicitCoin,
       outputs,
+      random,
       uniqueOutputAssetIDs,
       utxo
     });
@@ -38,6 +45,7 @@ export const roundRobinRandomImprove = (): InputSelector => ({
         }),
       implicitCoin,
       outputValues: toValues(outputs),
+      random,
       tokenBundleSizeExceedsLimit,
       uniqueOutputAssetIDs,
       utxoSelection: roundRobinSelectionResult

Diff for: packages/cip2/src/RoundRobinRandomImprove/roundRobin.ts

@@ -66,6 +66,7 @@ export const roundRobinSelection = ({
   utxo: utxosWithValue,
   outputs: outputsWithValue,
   uniqueOutputAssetIDs,
+  random,
   implicitCoin
 }: RoundRobinRandomImproveArgs): UtxoSelection => {
   // The subset of the UTxO that has already been selected:
@@ -81,7 +82,7 @@ export const roundRobinSelection = ({
       // this token from the remaining UTxO set:
       const utxo = filterUtxo(utxoRemaining);
       if (utxo.length > 0) {
-        const inputIdx = Math.floor(Math.random() * utxo.length);
+        const inputIdx = Math.floor(random() * utxo.length);
         const input = utxo[inputIdx];
         if (improvesSelection(utxoSelected, input, minimumTarget, getTotalSelectedQuantity)) {
           utxoSelected.push(input);

Diff for: packages/cip2/src/RoundRobinRandomImprove/util.ts

@@ -8,6 +8,7 @@ export interface RoundRobinRandomImproveArgs {
   outputs: Cardano.TxOut[];
   uniqueOutputAssetIDs: Cardano.AssetId[];
   implicitCoin: Required<Cardano.ImplicitCoin>;
+  random: typeof Math.random;
 }
 
 export interface UtxoSelection {
@@ -24,7 +25,7 @@ export const preprocessArgs = (
   availableUtxo: Set<Cardano.Utxo>,
   outputSet: Set<Cardano.TxOut>,
   partialImplicitCoin: Cardano.ImplicitCoin = noImplicitCoin
-): RoundRobinRandomImproveArgs => {
+): Omit<RoundRobinRandomImproveArgs, 'random'> => {
   const outputs = [...outputSet];
   const uniqueOutputAssetIDs = uniq(outputs.flatMap(({ value: { assets } }) => [...(assets?.keys() || [])]));
   const implicitCoin: Required<Cardano.ImplicitCoin> = {