fix amount arithmetic

extension/lib/wallet/types.ts

@@ -105,6 +105,7 @@ export interface ReserveCreationInfo {
   mintInfo: IMintInfo;
   selectedDenoms: Denomination[];
   withdrawFee: AmountJson;
+  overhead: AmountJson;
 }
 
 
@@ -157,7 +158,7 @@ export namespace Amounts {
     saturated: boolean;
   }
 
-  function getMaxAmount(currency: string) {
+  function getMaxAmount(currency: string): AmountJson {
     return {
       currency,
       value: Number.MAX_SAFE_INTEGER,
@@ -165,25 +166,39 @@ export namespace Amounts {
     }
   }
 
+  export function getZero(currency: string): AmountJson {
+    return {
+      currency,
+      value: 0,
+      fraction: 0,
+    }
+  }
+
   export function add(first: AmountJson, ...rest: AmountJson[]): Result {
+    const doit = () => {
       let currency = first.currency;
       let value = first.value + Math.floor(first.fraction / 1e6);
       if (value > Number.MAX_SAFE_INTEGER) {
         return {amount: getMaxAmount(currency), saturated: true};
       }
-    let fraction = first.fraction;
+      let fraction = first.fraction % 1e6;
       for (let x of rest) {
         if (x.currency !== currency) {
           throw Error(`Mismatched currency: ${x.currency} and ${currency}`);
         }
 
+        value = value + x.value + Math.floor((fraction + x.fraction) / 1e6);
         fraction = (fraction + x.fraction) % 1e6;
-      value = value + x.value + (Math.floor(fraction + x.fraction) / 1e6);
         if (value > Number.MAX_SAFE_INTEGER) {
           return {amount: getMaxAmount(currency), saturated: true};
         }
       }
       return {amount: {currency, value, fraction}, saturated: false};
+    };
+    console.log("adding", first, "and", rest);
+    let ret = doit();
+    console.log("result is", ret);
+    return ret;
   }
 
 
@@ -199,7 +214,7 @@ export namespace Amounts {
         return {amount: {currency, value: 0, fraction: 0}, saturated: true};
       }
       value--;
-      fraction = +1e6;
+      fraction += 1e6;
     }
     console.assert(fraction >= b.fraction);
     fraction -= b.fraction;
@@ -211,6 +226,7 @@ export namespace Amounts {
   }
 
   export function cmp(a: AmountJson, b: AmountJson): number {
+    const doit = () => {
       if (a.currency !== b.currency) {
         throw Error(`Mismatched currency: ${a.currency} and ${b.currency}`);
       }
@@ -232,9 +248,29 @@ export namespace Amounts {
         default:
           throw Error("assertion failed");
       }
+    };
+
+    console.log("comparing", a, "and", b);
+    let res = doit();
+    console.log("result:", res);
+    return res;
+
+  }
+
+  export function copy(a: AmountJson): AmountJson {
+    return {
+      value: a.value,
+      fraction: a.fraction,
+      currency: a.currency,
     }
   }
 
+  export function isNonZero(a: AmountJson) {
+    return a.value > 0 || a.fraction > 0;
+  }
+}
+
+
 export interface Notifier {
   notify();
 }