From c0238b1f21288456a22c8b0752ae0ca1f7be27c5 Mon Sep 17 00:00:00 2001
From: Mike Hearn <mike@plan99.net>
Date: Fri, 6 Nov 2015 12:59:52 +0100
Subject: [PATCH] Cash: add a TODO comment

---
 src/Cash.kt | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/Cash.kt b/src/Cash.kt
index 66bead9104..f37f6cfd2e 100644
--- a/src/Cash.kt
+++ b/src/Cash.kt
@@ -1,5 +1,4 @@
 import java.security.PublicKey
-import java.util.*
 
 /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 //
@@ -85,7 +84,12 @@ object CashContract : Contract {
             val inputAmount = inputs.map { it.amount }.sum()
             val outputAmount = outputs.map { it.amount }.sumOrZero(currency)
 
-            val issuerCommand = args.filter { it.signingInstitution == deposit.institution }.map { it.command as? ExitCashCommand }.filterNotNull().singleOrNull()
+            val issuerCommand = args.
+                    filter { it.signingInstitution == deposit.institution }.
+                    // TODO: this map+filterNotNull pattern will become a single function in the next Kotlin beta.
+                    map { it.command as? ExitCashCommand }.
+                    filterNotNull().
+                    singleOrNull()
             val amountExitingLedger = issuerCommand?.amount ?: Amount(0, inputAmount.currency)
 
             requireThat {
@@ -100,11 +104,16 @@ object CashContract : Contract {
         // data by the platform before execution.
         val owningPubKeys  = cashInputs.map  { it.owner }.toSortedSet()
         val keysThatSigned = args.filter { it.command is MoveCashCommand }.map { it.signer }.toSortedSet()
-        requireThat { "the owning keys are the same as the signing keys" by (owningPubKeys == keysThatSigned) }
+        requireThat {
+            "the owning keys are the same as the signing keys" by (owningPubKeys == keysThatSigned)
+        }
 
         // Accept.
     }
 
+    // TODO: craftSpend should work more like in bitcoinj, where it takes and modifies a transaction template.
+    // This would allow multiple contracts to compose properly (e.g. bond trade+cash movement).
+
     /** Generate a transaction that consumes one or more of the given input states to move money to the given pubkey. */
     @Throws(InsufficientBalanceException::class)
     fun craftSpend(amount: Amount, to: PublicKey, wallet: List<CashState>): TransactionForTest {