introduce map for query streams

lib/wallet/query.ts

@@ -66,7 +66,8 @@ export interface QueryStream<T> {
                                    keyFn: (obj: T) => I): QueryStream<JoinResult<T,S>>;
   filter(f: (T: any) => boolean): QueryStream<T>;
   reduce<S>(f: (v: T, acc: S) => S, start?: S): Promise<S>;
-  flatMap(f: (x: T) => T[]): QueryStream<T>;
+  map<S>(f: (x:T) => S): QueryStream<S>;
+  flatMap<S>(f: (x: T) => S[]): QueryStream<S>;
   toArray(): Promise<T[]>;
 }
 
@@ -102,10 +103,14 @@ abstract class QueryStreamBase<T> implements QueryStream<T> {
     this.root = root;
   }
 
-  flatMap(f: (x: T) => T[]): QueryStream<T> {
+  flatMap<S>(f: (x: T) => T[]): QueryStream<S> {
     return new QueryStreamFlatMap(this, f);
   }
 
+  map<S>(f: (x: T) => S): QueryStream<T> {
+    return new QueryStreamMap(this, f);
+  }
+
   indexJoin<S,I extends IDBValidKey>(index: Index<I,S>,
                                      keyFn: (obj: T) => I): QueryStream<JoinResult<T, S>> {
     this.root.addStoreAccess(index.storeName, false);
@@ -213,6 +218,29 @@ class QueryStreamFlatMap<T> extends QueryStreamBase<T> {
 }
 
 
+class QueryStreamMap<T> extends QueryStreamBase<T> {
+  s: QueryStreamBase<T>;
+  mapFn: (v: T) => T[];
+
+  constructor(s: QueryStreamBase<T>, mapFn: (v: T) => T[]) {
+    super(s.root);
+    this.s = s;
+    this.mapFn = mapFn;
+  }
+
+  subscribe(f: SubscribeFn) {
+    this.s.subscribe((isDone, value, tx) => {
+      if (isDone) {
+        f(true, undefined, tx);
+        return;
+      }
+      let mappedValue = this.mapFn(value);
+      f(false, mappedValue, tx);
+    });
+  }
+}
+
+
 class QueryStreamIndexJoin<T, S> extends QueryStreamBase<JoinResult<T, S>> {
   s: QueryStreamBase<T>;
   storeName: string;

lib/wallet/wallet.ts

@@ -406,14 +406,14 @@ export class Wallet {
   updateExchanges(): void {
     console.log("updating exchanges");
 
-    this.q()
-        .iter(Stores.exchanges)
-        .reduce((exchange: IExchangeInfo) => {
-          this.updateExchangeFromUrl(exchange.baseUrl)
-              .catch((e) => {
-                console.error("updating exchange failed", e);
-              });
-        });
+    let exchangesUrls = this.q().iter(Stores.exchanges).map((e) => e.baseUrl);
+
+    for (let url of exchangesUrls) {
+      this.updateExchangeFromUrl(url)
+          .catch((e) => {
+            console.error("updating exchange failed", e);
+          });
+    }
   }
 
   /**
@@ -1291,9 +1291,6 @@ export class Wallet {
 
 
   async createRefreshSession(oldCoinPub: string): Promise<RefreshSession|undefined> {
-
-    // FIXME: this is not running in a transaction.
-
     let coin = await this.q().get<Coin>(Stores.coins, oldCoinPub);
 
     if (!coin) {
@@ -1335,13 +1332,20 @@ export class Wallet {
                                           newCoinDenoms,
                                           oldDenom.fee_refresh));
 
-    coin.currentAmount = Amounts.sub(coin.currentAmount,
-                                     refreshSession.valueWithFee).amount;
+    function mutateCoin(c: Coin): Coin {
+      let r = Amounts.sub(coin.currentAmount,
+                          refreshSession.valueWithFee);
+      if (r.saturated) {
+        // Something else must have written the coin value
+        throw AbortTransaction;
+      }
+      c.currentAmount = r.amount;
+      return c;
+    }
 
-    // FIXME:  we should check whether the amount still matches!
     await this.q()
               .put(Stores.refresh, refreshSession)
-              .put(Stores.coins, coin)
+              .mutate(Stores.coins, coin.coinPub, mutateCoin)
               .finish();
 
     return refreshSession;