Start out coin<->Amount<->Ticker mapping

src/types.ts

@@ -1,4 +1,6 @@
 import amino from "@tendermint/amino-js";
+import {Amount, Token} from "@iov/bcp";
+
 
 export type AminoTx = amino.Tx & { readonly value: amino.StdTx };
 
@@ -8,3 +10,31 @@ export function isAminoStdTx(txValue: amino.TxValue): txValue is amino.StdTx {
     typeof memo === "string" && Array.isArray(msg) && typeof fee === "object" && Array.isArray(signatures)
   );
 }
+
+export interface TokenInfo extends Token {
+  readonly denom: string;
+}
+
+// TODO: alias amino types
+export function amountToCoin(lookup: ReadonlyArray<TokenInfo>, amount: Amount): amino.Coin {
+  const match = lookup.find(({tokenTicker}) => tokenTicker === amount.tokenTicker);
+  if (!match) {
+    throw Error(`unknown ticker: ${amount.tokenTicker}`);
+  }
+  return {
+    denom: match.denom,
+    amount: amount.quantity,
+  };
+}
+
+export function coinToAmount(lookup: ReadonlyArray<TokenInfo>, coin: amino.Coin): Amount {
+  const match = lookup.find(({denom}) => denom === coin.denom);
+  if (!match) {
+    throw Error(`unknown denom: ${coin.denom}`);
+  }
+  return {
+    tokenTicker: match.tokenTicker,
+    fractionalDigits: match.fractionalDigits,
+    quantity: coin.amount,
+  };
+}