From e0db927bca979e2ca13535c5cc0148f3c5a1dc4f Mon Sep 17 00:00:00 2001
From: Simon Warta <simon@warta.it>
Date: Mon, 10 Feb 2020 18:42:20 +0100
Subject: [PATCH] Add strict toErc20Amount converter

---
 packages/bcp/src/cosmwasmcodec.spec.ts      |  2 +-
 packages/bcp/src/cosmwasmconnection.spec.ts |  2 +-
 packages/bcp/src/encode.spec.ts             | 34 ++++++++++++++++++++-
 packages/bcp/src/encode.ts                  | 10 +++++-
 packages/bcp/types/encode.d.ts              |  1 +
 5 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/packages/bcp/src/cosmwasmcodec.spec.ts b/packages/bcp/src/cosmwasmcodec.spec.ts
index d55a2939..2269887e 100644
--- a/packages/bcp/src/cosmwasmcodec.spec.ts
+++ b/packages/bcp/src/cosmwasmcodec.spec.ts
@@ -75,7 +75,7 @@ describe("CosmWasmCodec", () => {
         recipient: "cosmos1dddd" as Address,
         memo: "My first BASH payment",
         amount: {
-          fractionalDigits: 6,
+          fractionalDigits: 0,
           quantity: "345",
           tokenTicker: "BASH" as TokenTicker,
         },
diff --git a/packages/bcp/src/cosmwasmconnection.spec.ts b/packages/bcp/src/cosmwasmconnection.spec.ts
index 769eb07a..6e28d6dc 100644
--- a/packages/bcp/src/cosmwasmconnection.spec.ts
+++ b/packages/bcp/src/cosmwasmconnection.spec.ts
@@ -477,7 +477,7 @@ describe("CosmWasmConnection", () => {
         memo: "My first payment",
         amount: {
           quantity: "75",
-          fractionalDigits: 3, // todo: BROKEN!
+          fractionalDigits: 0,
           tokenTicker: "BASH" as TokenTicker,
         },
       });
diff --git a/packages/bcp/src/encode.spec.ts b/packages/bcp/src/encode.spec.ts
index 9b5138bc..0e239aa4 100644
--- a/packages/bcp/src/encode.spec.ts
+++ b/packages/bcp/src/encode.spec.ts
@@ -20,6 +20,7 @@ import {
   encodeFee,
   encodeFullSignature,
   encodePubkey,
+  toErc20Amount,
 } from "./encode";
 import { BankTokens, Erc20Token } from "./types";
 
@@ -75,6 +76,37 @@ describe("encode", () => {
     });
   });
 
+  describe("toErc20Amount", () => {
+    const [ash, bash] = defaultErc20Tokens;
+
+    it("encodes an amount", () => {
+      const amount: Amount = {
+        quantity: "789",
+        fractionalDigits: 0,
+        tokenTicker: "BASH" as TokenTicker,
+      };
+      expect(toErc20Amount(amount, bash)).toEqual("789");
+    });
+
+    it("throws on ticker mismatch", () => {
+      const amount: Amount = {
+        quantity: "789",
+        fractionalDigits: 0,
+        tokenTicker: "BASH" as TokenTicker,
+      };
+      expect(() => toErc20Amount(amount, ash)).toThrowError(/ticker mismatch/i);
+    });
+
+    it("throws on ticker mismatch", () => {
+      const amount: Amount = {
+        quantity: "789",
+        fractionalDigits: 2,
+        tokenTicker: "BASH" as TokenTicker,
+      };
+      expect(() => toErc20Amount(amount, bash)).toThrowError(/fractional digits mismatch/i);
+    });
+  });
+
   describe("amountToBankCoin", () => {
     it("encodes an amount", () => {
       expect(amountToBankCoin(defaultAmount, defaultTokens)).toEqual({
@@ -288,7 +320,7 @@ describe("encode", () => {
         recipient: "cosmos1dddd" as Address,
         memo: defaultMemo,
         amount: {
-          fractionalDigits: 6,
+          fractionalDigits: 0,
           quantity: "345",
           tokenTicker: "BASH" as TokenTicker,
         },
diff --git a/packages/bcp/src/encode.ts b/packages/bcp/src/encode.ts
index e0446735..f1a61b65 100644
--- a/packages/bcp/src/encode.ts
+++ b/packages/bcp/src/encode.ts
@@ -33,6 +33,14 @@ export function encodePubkey(pubkey: PubkeyBundle): types.PubKey {
   }
 }
 
+export function toErc20Amount(amount: Amount, erc20Token: Erc20Token): string {
+  if (amount.tokenTicker !== erc20Token.ticker) throw new Error("Ticker mismatch between amount and token");
+  if (amount.fractionalDigits !== erc20Token.fractionalDigits) {
+    throw new Error("Fractional digits mismatch between amount and token");
+  }
+  return amount.quantity;
+}
+
 export function amountToBankCoin(amount: Amount, tokens: BankTokens): types.Coin {
   const match = tokens.find(token => token.ticker === amount.tokenTicker);
   if (!match) throw Error(`unknown ticker: ${amount.tokenTicker}`);
@@ -117,7 +125,7 @@ export function buildUnsignedTx(
               contract: matchingErc20Token.contractAddress,
               msg: {
                 transfer: {
-                  amount: tx.amount.quantity,
+                  amount: toErc20Amount(tx.amount, matchingErc20Token),
                   recipient: tx.recipient,
                 },
               },
diff --git a/packages/bcp/types/encode.d.ts b/packages/bcp/types/encode.d.ts
index 8589e217..fe974fc0 100644
--- a/packages/bcp/types/encode.d.ts
+++ b/packages/bcp/types/encode.d.ts
@@ -2,6 +2,7 @@ import { types } from "@cosmwasm/sdk";
 import { Amount, Fee, FullSignature, PubkeyBundle, SignedTransaction, UnsignedTransaction } from "@iov/bcp";
 import { BankTokens, Erc20Token } from "./types";
 export declare function encodePubkey(pubkey: PubkeyBundle): types.PubKey;
+export declare function toErc20Amount(amount: Amount, erc20Token: Erc20Token): string;
 export declare function amountToBankCoin(amount: Amount, tokens: BankTokens): types.Coin;
 export declare function encodeFee(fee: Fee, tokens: BankTokens): types.StdFee;
 export declare function encodeFullSignature(fullSignature: FullSignature): types.StdSignature;