From f41d37c2f9197eff0cc35d835abd6900df1da899 Mon Sep 17 00:00:00 2001
From: Martynas Kazlauskas <martynas.kazlauskas@iohk.io>
Date: Tue, 28 Sep 2021 09:33:21 +0300
Subject: [PATCH] feat(cip2): add functions to create selection constraints
 (wip)

---
 packages/cip2/src/selectionConstraints.ts     | 51 +++++++++++++++++
 packages/cip2/src/types.ts                    |  3 +-
 .../cip2/test/selectionConstraints.test.ts    | 56 +++++++++++++++++++
 3 files changed, 109 insertions(+), 1 deletion(-)
 create mode 100644 packages/cip2/src/selectionConstraints.ts
 create mode 100644 packages/cip2/test/selectionConstraints.test.ts

diff --git a/packages/cip2/src/selectionConstraints.ts b/packages/cip2/src/selectionConstraints.ts
new file mode 100644
index 00000000000..bda83ce02b7
--- /dev/null
+++ b/packages/cip2/src/selectionConstraints.ts
@@ -0,0 +1,51 @@
+import { CardanoSerializationLib, CSL, ProtocolParametersRequiredByWallet } from '@cardano-sdk/core';
+import { ComputeMinimumCoinQuantity, EstimateTxFee, SelectionSkeleton } from './types';
+
+export type BuildTx = (selection: SelectionSkeleton) => Promise<CSL.Transaction>;
+
+export const computeMinimumCost =
+  (
+    csl: CardanoSerializationLib,
+    { minFeeCoefficient, minFeeConstant }: ProtocolParametersRequiredByWallet,
+    buildTx: BuildTx
+  ): EstimateTxFee =>
+  async (selection) => {
+    const tx = await buildTx(selection);
+    return BigInt(
+      csl
+        .min_fee(
+          tx,
+          csl.LinearFee.new(
+            csl.BigNum.from_str(minFeeCoefficient.toString()),
+            csl.BigNum.from_str(minFeeConstant.toString())
+          )
+        )
+        .to_str()
+    );
+  };
+
+//
+export const computeMinimumCoinQuantity =
+  (
+    csl: CardanoSerializationLib,
+    { coinsPerUtxoWord }: ProtocolParametersRequiredByWallet
+  ): ComputeMinimumCoinQuantity =>
+  (multiasset) => {
+    const minUTxOValue = CSL.BigNum.from_str((BigInt(coinsPerUtxoWord) * 29n).toString());
+    const value = csl.Value.new(csl.BigNum.from_str('0'));
+    if (multiasset) {
+      value.set_multiasset(multiasset);
+    }
+    return BigInt(csl.min_ada_required(value, minUTxOValue).to_str());
+  };
+
+//         tokenBundleSizeExceedsLimit: (tokenBundle) => {
+//           logger.debug('SelectionConstraint: tokenBundleSizeExceedsLimit', tokenBundle);
+//           // Todo: Replace with real implementation
+//           return false;
+//         },
+//         computeSelectionLimit: async (selectionSkeleton) => {
+//           logger.debug('SelectionConstraint: computeSelectionLimit', selectionSkeleton);
+//           // Todo: Replace with real implementation
+//           return 5;
+//         }
diff --git a/packages/cip2/src/types.ts b/packages/cip2/src/types.ts
index b375cf63721..7a2e87d7dad 100644
--- a/packages/cip2/src/types.ts
+++ b/packages/cip2/src/types.ts
@@ -22,6 +22,7 @@ export interface SelectionResult {
     /**
      * Estimated fee for the transaction.
      * This value is included in 'change', so the actual change returned by the transaction is change-fee.
+     * TODO: refactor this to return CSL.BigNum?
      */
     fee: bigint;
   };
@@ -53,7 +54,7 @@ export type TokenBundleSizeExceedsLimit = (tokenBundle: CSL.MultiAsset) => boole
 /**
  * @returns minimum lovelace amount in a UTxO
  */
-export type ComputeMinimumCoinQuantity = (assetQuantities: CSL.MultiAsset) => bigint;
+export type ComputeMinimumCoinQuantity = (assetQuantities?: CSL.MultiAsset) => bigint;
 
 /**
  * @returns an upper bound for the number of ordinary inputs to
diff --git a/packages/cip2/test/selectionConstraints.test.ts b/packages/cip2/test/selectionConstraints.test.ts
new file mode 100644
index 00000000000..8dcf392c712
--- /dev/null
+++ b/packages/cip2/test/selectionConstraints.test.ts
@@ -0,0 +1,56 @@
+import {
+  CardanoSerializationLib,
+  loadCardanoSerializationLib,
+  ProtocolParametersRequiredByWallet
+} from '@cardano-sdk/core';
+import { PXL_Asset, TSLA_Asset } from './util';
+import { computeMinimumCoinQuantity, computeMinimumCost } from '../src/selectionConstraints';
+import { SelectionSkeleton } from '../src/types';
+import { valueQuantitiesToValue } from '../src/util';
+
+describe('selectionConstraints', () => {
+  let csl: CardanoSerializationLib;
+  beforeAll(async () => {
+    csl = await loadCardanoSerializationLib();
+  });
+
+  it('computeMinimumCost', async () => {
+    const fee = 200_000n;
+    // Need this to not have to build Tx
+    const stubCsl = {
+      min_fee: jest.fn().mockReturnValueOnce(csl.BigNum.from_str(fee.toString())),
+      LinearFee: csl.LinearFee,
+      BigNum: csl.BigNum
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    } as any as CardanoSerializationLib;
+    const buildTx = jest.fn();
+    const selectionSkeleton = {} as SelectionSkeleton;
+    const result = await computeMinimumCost(
+      stubCsl,
+      { minFeeCoefficient: 44, minFeeConstant: 155_381 } as ProtocolParametersRequiredByWallet,
+      buildTx
+    )(selectionSkeleton);
+    expect(result).toEqual(fee);
+    expect(buildTx).toBeCalledTimes(1);
+    expect(buildTx).toBeCalledWith(selectionSkeleton);
+  });
+
+  it('computeMinimumCoinQuantity', () => {
+    const withAssets = valueQuantitiesToValue(
+      {
+        coins: 10_000n,
+        assets: {
+          [TSLA_Asset]: 5000n,
+          [PXL_Asset]: 3000n
+        }
+      },
+      csl
+    ).multiasset();
+    const protocolParams = { coinsPerUtxoWord: 34_482 } as ProtocolParametersRequiredByWallet;
+    const minCoinWithAssets = computeMinimumCoinQuantity(csl, protocolParams)(withAssets);
+    const minCoinWithoutAssets = computeMinimumCoinQuantity(csl, protocolParams)();
+    expect(typeof minCoinWithAssets).toBe('bigint');
+    expect(typeof minCoinWithoutAssets).toBe('bigint');
+    expect(minCoinWithAssets).toBeGreaterThan(minCoinWithoutAssets);
+  });
+});