Updates to coin distributor example

Author: mikera

convex-core/src/main/cvx/convex/lab/distributor.cvx

@@ -15,26 +15,38 @@
 
 ;; Set the amount of available coins. Only a trusted allocator can do this
 (defn ^:callable set-available [amount]
-  (when (> amount *balance*) 
-    (fail :STATE "Insufficient balance"))
+  (if (not (trust/trusted? allocator *caller* :set-available amount))
+	(fail :TRUST "Not authorised as allocator"))
 
-  (when-not (trust/trusted? allocator *caller* :set-available amount)
-    (fail :TRUST "Not authorised as allocator"))
+  (if (< amount 0) 
+	(fail :ARGUMENT "Negative amount!"))
 
-  (set! available-coins amount))
+  (set! available-coins (int amount)))
 
-;; Distribute coins coins. Only a trusted distributor can do this
+;; Distribute coins. Only a trusted distributor can do this
 (defn ^:callable distribute [receiver amount]
-  (cond
-    (not (int? amount)) 
-      (fail :ARGUMENT "amount must be an integer")
-	(not (trust/trusted? distributor *caller* :distribute amount))
-	  (fail :TRUST "Not authorised to distribute")
-	(> amount available-coins)
-	  (fail :FUNDS "Insufficient available coins")
-	  (do 
-		 (set! available-coins (- available-coins amount))
-		 (transfer receiver amount))))
+  (if (not (int? amount))
+	(fail :ARGUMENT "amount must be an integer"))
+  
+  (if (not (trust/trusted? distributor *caller* :distribute amount))
+	(fail :TRUST "Not authorised to distribute")) 
+  
+  (if (> amount available-coins)
+    (fail :FUNDS "Insufficient available coins"))
+  
+  ;; Every check passed, so:
+  ;; 1. reduce available coins (Effect)
+  ;; 2. Make an external transfer (interaction)
+  (do 
+    (set! available-coins (- available-coins amount))
+    (transfer receiver amount)))
 
 (defn ^:callable receive-coin [_ _ _]
-  (accept *offer*))
+  (accept *offer*))
+
+(defn ^:callable withdraw [amount]
+  (if (not (trust/trusted? allocator *caller* :withdraw amount))
+    (fail :TRUST "Not authorised to withdraw"))
+  
+  ;; Transfer the withdrawn amount back to the caller
+  (transfer *caller* amount))

convex-core/src/test/java/convex/actors/DistributorTest.java

@@ -41,13 +41,11 @@ public class DistributorTest extends ACVMTest {
 		assertArgumentError(step(c,"(call DIST (distribute *address* nil))"));
 		assertArgumentError(step(c,"(call DIST (distribute *address* -1))"));
 		assertCastError(step(c,"(call DIST (distribute :foo 0))"));
-		
-		// initially no actor balance, so can't set available coins greater than 0
-		assertStateError(step(c,"(call DIST (set-available 1))"));
 
 		// zero distribution is OK
 		c=exec(c,"(call DIST (distribute *address* 0))");
 
+		assertTrustError(step(c,"(query-as #0 `(call ~DIST (set-available 1000)))"));
 	}
 
 	@Test public void testDistributuion() {
@@ -70,4 +68,18 @@ public class DistributorTest extends ACVMTest {
 		assertEquals(700000L,evalL(c,"DIST/available-coins"));
 
 	}
+	
+	@Test public void testWithdraw() {
+		Context c=context();
+
+		// set available coins works after transferring in some coins
+		c=exec(c,"(transfer DIST 3000000)");
+		assertEquals(3000000L,evalL(c,"(balance DIST)"));
+
+		c=exec(c,"(call DIST (withdraw 1000000))");
+		assertEquals(2000000L,evalL(c,"(balance DIST)"));
+		
+		// withdraw more than is left = :FUNDS error
+		assertFundsError(step(c,"(call DIST (withdraw 2000001))"));
+	}
 }