fix: guard ship purchases against insufficient funds

README.md

@@ -679,4 +679,4 @@ ESEIDEL-4E: null
   Orbiting X1-AV52-62175B ASTEROID_FIELD EXCAVATOR 1/60
   MOUNT_SURVEYOR_II         1 x 17,478c  = 17,478c
 
-null in this case is a surveyor.
+null in this case is a surveyor.

packages/cli/lib/behavior/behavior.dart

@@ -48,6 +48,10 @@ void jobAssert(
   }
 }
 
+/// Throw a job exception.
+Never failJob(String message, Duration timeout) =>
+    throw JobException(message, timeout);
+
 /// Exception thrown from a Job if the condition is not met.
 T assertNotNull<T>(
   T? value,
@@ -175,11 +179,9 @@ class MultiJob {
         return result.waitTime;
       }
     }
-    jobAssert(
-      false,
+    failJob(
       'Too many $name job iterations',
       const Duration(hours: 1),
     );
-    return null;
   }
 }

packages/cli/lib/behavior/buy_ship.dart

@@ -5,6 +5,7 @@ import 'package:cli/logger.dart';
 import 'package:cli/nav/navigation.dart';
 import 'package:cli/nav/route.dart';
 import 'package:cli/net/actions.dart';
+import 'package:cli/net/exceptions.dart';
 import 'package:cli/net/queries.dart';
 import 'package:cli/trading.dart';
 import 'package:db/db.dart';
@@ -118,21 +119,36 @@ Future<DateTime?> advanceBuyShip(
   recordShipyardDataAndLog(caches.shipyardPrices, shipyard, ship);
 
   // TODO(eseidel): Catch exceptions about insufficient credits.
-  final result = await purchaseShipAndLog(
-    api,
-    db,
-    caches.ships,
-    caches.agent,
-    ship,
-    shipyard.waypointSymbol,
-    shipType,
-  );
+  final PurchaseShip201ResponseData result;
+  try {
+    result = await purchaseShipAndLog(
+      api,
+      db,
+      caches.ships,
+      caches.agent,
+      ship,
+      shipyard.waypointSymbol,
+      shipType,
+    );
+  } on ApiException catch (e) {
+    // ApiException 400: {"error":{"message":"Failed to purchase ship.
+    // Agent has insufficient funds.","code":4216,
+    // "data":{"creditsAvailable":116103,"creditsNeeded":172355}}}
+    final neededCredits = neededCreditsFromPurchaseShipException(e);
+    if (neededCredits == null) {
+      // Was not an insufficient credits exception.
+      rethrow;
+    }
+    failJob(
+      'Failed to purchase ship ${caches.agent.agent.credits} < $neededCredits',
+      const Duration(minutes: 10),
+    );
+  }
+
   // Record our success!
   state.isComplete = true;
-  jobAssert(
-    false,
+  failJob(
     'Purchased ${result.ship.symbol} ($shipType)!',
     const Duration(minutes: 10),
   );
-  return null;
 }

packages/cli/lib/behavior/jobs/mount_job.dart

@@ -82,6 +82,5 @@ Future<JobResult> doMountJob(
   );
   // We're done.
   state.isComplete = true;
-  jobAssert(false, 'Mounting complete!', const Duration(hours: 1));
-  return JobResult.complete();
+  failJob('Mounting complete!', const Duration(hours: 1));
 }

packages/cli/lib/net/exceptions.dart

@@ -148,3 +148,33 @@ bool isInsufficientCreditsException(ApiException e) {
 bool isShipNotInOrbitException(ApiException e) {
   return isAPIExceptionWithCode(e, 4236);
 }
+
+// ApiException 400: {"error":{"message":"Failed to purchase ship.
+// Agent has insufficient funds.","code":4216,
+// "data":{"creditsAvailable":116103,"creditsNeeded":172355}}}
+// bool isInsufficientCreditsToPurchaseShipException(ApiException e) {
+//   return isAPIExceptionWithCode(e, 4216);
+// }
+
+int? neededCreditsFromPurchaseShipException(ApiException e) {
+  final jsonString = e.message;
+  if (jsonString != null) {
+    Map<String, dynamic> exceptionJson;
+    try {
+      exceptionJson = jsonDecode(jsonString) as Map<String, dynamic>;
+    } on FormatException catch (e) {
+      // Catch any json decode errors, so the original exception can be
+      // rethrown by the caller instead of a json decode error.
+      logger.warn('Failed to parse exception json: $e');
+      return null;
+    }
+    final error = mapCastOfType<String, dynamic>(exceptionJson, 'error');
+    final code = mapValueOfType<int>(error, 'code');
+    if (code != 4216) {
+      return null;
+    }
+    final errorData = mapCastOfType<String, dynamic>(error, 'data');
+    return mapValueOfType<int>(errorData, 'creditsNeeded');
+  }
+  return null;
+}