Contracts: a bit more work on the CP implementation, add a unit test for redemption at time.

.gitignore

@@ -1,3 +1,5 @@
+TODO
+
 # Created by .ignore support plugin (hsz.mobi)
 
 .gradle

src/contracts/ComedyPaper.kt

@@ -50,17 +50,23 @@ object ComedyPaper : Contract {
             // For now do not allow multiple pieces of CP to trade in a single transaction. Study this more!
             val input = inStates.filterIsInstance<ComedyPaper.State>().single()
 
+            requireThat {
+                "the transaction is signed by the owner of the CP" by (command.signers.contains(input.owner))
+            }
+
             when (command.value) {
                 is Commands.Move -> requireThat {
                     val output = outStates.filterIsInstance<ComedyPaper.State>().single()
-                    "the transaction is signed by the owner of the CP" by (command.signers.contains(input.owner))
                     "the output state is the same as the input state except for owner" by (input.withoutOwner() == output.withoutOwner())
                 }
 
                 is Commands.Redeem -> requireThat {
-                    val received = outStates.sumCash()
+                    val received = try {
+                        outStates.sumCash()
+                    } catch (e: UnsupportedOperationException) {
+                        throw IllegalStateException("invalid cash outputs")
+                    }
                     // Do we need to check the signature of the issuer here too?
-                    "the transaction is signed by the owner of the CP" by (command.signers.contains(input.owner))
                     "the paper must have matured" by (input.maturityDate < time)
                     "the received amount equals the face value" by (received == input.faceValue)
                     "the paper must be destroyed" by outStates.filterIsInstance<ComedyPaper.State>().none()

src/core/ContractsDSL.kt

@@ -26,7 +26,7 @@ inline fun <reified T : Command> List<VerifiedSigned<Command>>.requireSingleComm
     select<T>().single()
 } catch (e: NoSuchElementException) {
     // Better error message.
-    throw IllegalStateException("Required ${T::class.simpleName} command")
+    throw IllegalStateException("Required ${T::class.qualifiedName} command")
 }
 
 // endregion
@@ -51,13 +51,14 @@ val Double.SWISS_FRANCS: Amount get() = Amount((this * 100).toInt(), USD)
 // region Requirements
 ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
-object Requirements {
+class Requirements {
     infix fun String.by(expr: Boolean) {
         if (!expr) throw IllegalArgumentException("Failed requirement: $this")
     }
 }
+val R = Requirements()
 inline fun requireThat(body: Requirements.() -> Unit) {
-    Requirements.body()
+    R.body()
 }
 
 // endregion

src/core/TestUtils.kt

@@ -60,43 +60,48 @@ val TEST_PROGRAM_MAP: Map<SecureHash, Contract> = mapOf(
 // TODO: Make it impossible to forget to test either a failure or an accept for each transaction{} block
 
 // Corresponds to the args to Contract.verify
-data class TransactionForTest(
-    private val inStates: MutableList<ContractState> = arrayListOf(),
-    private val outStates: MutableList<ContractState> = arrayListOf(),
+class TransactionForTest() {
+    private val inStates = arrayListOf<ContractState>()
+
+    class LabeledOutput(val label: String?, val state: ContractState) {
+        override fun toString() = state.toString() + (if (label != null) " ($label)" else "")
+        override fun equals(other: Any?) = other is LabeledOutput && state.equals(other.state)
+        override fun hashCode(): Int = state.hashCode()
+    }
+    private val outStates = arrayListOf<LabeledOutput>()
     private val args: MutableList<VerifiedSigned<Command>> = arrayListOf()
-) {
+
+    constructor(inStates: List<ContractState>, outStates: List<ContractState>, args: List<VerifiedSigned<Command>>) : this() {
+        this.inStates.addAll(inStates)
+        this.outStates.addAll(outStates.map { LabeledOutput(null, it) })
+        this.args.addAll(args)
+    }
+
     fun input(s: () -> ContractState) = inStates.add(s())
-    fun output(s: () -> ContractState) = outStates.add(s())
-    fun arg(key: PublicKey, c: () -> Command) = args.add(VerifiedSigned(listOf(key), TEST_KEYS_TO_CORP_MAP[key].let { if (it != null) listOf(it) else emptyList() }, c()))
-
-    private fun run() = TransactionForVerification(inStates, outStates, args, TEST_TX_TIME).verify(TEST_PROGRAM_MAP)
-
-    infix fun `fails requirement`(msg: String) {
-        try {
-            run()
-        } catch(e: Exception) {
-            val m = e.message
-            if (m == null)
-                fail("Threw exception without a message")
-            else
-                if (!m.toLowerCase().contains(msg.toLowerCase())) throw AssertionError("Error was actually: $m", e)
-        }
+    fun output(label: String? = null, s: () -> ContractState) = outStates.add(LabeledOutput(label, s()))
+    fun arg(vararg key: PublicKey, c: () -> Command) {
+        val keys = listOf(*key)
+        // TODO: replace map->filterNotNull once upgraded to next Kotlin
+        args.add(VerifiedSigned(keys, keys.map { TEST_KEYS_TO_CORP_MAP[it] }.filterNotNull(), c()))
     }
 
+    private fun run(time: Instant) = TransactionForVerification(inStates, outStates.map { it.state }, args, time).verify(TEST_PROGRAM_MAP)
+
+    infix fun `fails requirement`(msg: String) = rejects(msg)
     // which is uglier?? :)
     fun fails_requirement(msg: String) = this.`fails requirement`(msg)
 
-    fun accepts() = run()
-    fun rejects(withMessage: String? = null) {
+    fun accepts(time: Instant = TEST_TX_TIME) = run(time)
+    fun rejects(withMessage: String? = null, time: Instant = TEST_TX_TIME) {
         val r = try {
-            run()
+            run(time)
             false
         } catch (e: Exception) {
             val m = e.message
             if (m == null)
                 fail("Threw exception without a message")
             else
-                if (withMessage != null && !m.contains(withMessage)) throw AssertionError("Error was actually: $m", e)
+                if (withMessage != null && !m.toLowerCase().contains(withMessage.toLowerCase())) throw AssertionError("Error was actually: $m", e)
             true
         }
         if (!r) throw AssertionError("Expected exception but didn't get one")
@@ -112,6 +117,21 @@ data class TransactionForTest(
         return tx
     }
 
+    // Use this to create transactions where the output of this transaction is automatically used as an input of
+    // the next.
+    fun chain(vararg outputLabels: String, body: TransactionForTest.() -> Unit) {
+        val states = outStates.filter {
+            val l = it.label
+            if (l != null)
+                outputLabels.contains(l)
+            else
+                false
+        }.map { it.state }    // TODO: replace with mapNotNull after next Kotlin upgrade
+        val tx = TransactionForTest()
+        tx.inStates.addAll(states)
+        tx.body()
+    }
+
     override fun toString(): String {
         return """transaction {
             inputs:   $inStates
@@ -119,6 +139,15 @@ data class TransactionForTest(
             args:     $args
         }"""
     }
+
+    override fun equals(other: Any?) = this === other || (other is TransactionForTest && inStates == other.inStates && outStates == other.outStates && args == other.args)
+
+    override fun hashCode(): Int {
+        var result = inStates.hashCode()
+        result += 31 * result + outStates.hashCode()
+        result += 31 * result + args.hashCode()
+        return result
+    }
 }
 
 fun transaction(body: TransactionForTest.() -> Unit): TransactionForTest {

src/core/Transactions.kt

@@ -41,7 +41,6 @@ class TransactionForVerification(
     val args: List<VerifiedSigned<Command>>,
     val time: Instant
 ) {
-
     fun verify(programMap: Map<SecureHash, Contract>) {
         // For each input and output state, locate the program to run. Then execute the verification function. If any
         // throws an exception, the entire transaction is invalid.

tests/contracts/ComedyPaperTests.kt

@@ -14,12 +14,18 @@ class ComedyPaperTests {
     )
     val PAPER_2 = PAPER_1.copy(owner = DUMMY_PUBKEY_2)
 
+    val CASH_1 = Cash.State(InstitutionReference(MINI_CORP, OpaqueBytes.of(1)), 1000.DOLLARS, DUMMY_PUBKEY_1)
+    val CASH_2 = CASH_1.copy(owner = DUMMY_PUBKEY_2)
+    val CASH_3 = CASH_1.copy(owner = DUMMY_PUBKEY_1)
+
     @Test
     fun move() {
-        // One entity sells the paper to another (e.g. the issuer sells it to a first time buyer)
         transaction {
+            // One entity sells the paper to another (e.g. the issuer sells it to a first time buyer)
             input { PAPER_1 }
-            output { PAPER_2 }
+            input { CASH_1 }
+            output("a") { PAPER_2 }
+            output { CASH_2 }
 
             this.rejects()
 
@@ -28,10 +34,25 @@ class ComedyPaperTests {
                 this `fails requirement` "is signed by the owner"
             }
 
-            transaction {
             arg(DUMMY_PUBKEY_1) { ComedyPaper.Commands.Move() }
+            arg(DUMMY_PUBKEY_1) { Cash.Commands.Move() }
             this.accepts()
-            }
+        }.chain("a") {
+            arg(DUMMY_PUBKEY_2, MINI_CORP_KEY) { ComedyPaper.Commands.Redeem() }
+
+            // No cash output, can't redeem like that!
+            this.rejects("invalid cash outputs")
+
+            input { CASH_3 }
+            output { CASH_2 }
+
+            arg(DUMMY_PUBKEY_1) { Cash.Commands.Move() }
+
+            // Time passes, but not enough. An attempt to redeem is made.
+            this.rejects("must have matured")
+
+            // Try again at the right time.
+            this.accepts(TEST_TX_TIME + 10.days)
         }
     }
 }