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Cash contract: Introduce a DepositPointer abstraction for easier grouping

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In this current model, you cannot mix up money from different deposits: they must always be kept separate.
This commit is contained in:
Mike Hearn 2015-11-03 18:05:21 +01:00
parent fd67a85c29
commit a09120d445
2 changed files with 31 additions and 28 deletions
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22
src/Cash.kt
View File

@ -11,13 +11,16 @@ import java.util.*
// Just a fake program identifier for now. In a real system it could be, for instance, the hash of the program bytecode.
val CASH_PROGRAM_ID = SecureHash.sha256("cash")
/**
* Reference to some money being stored by an institution e.g. in a vault or (more likely) on their normal ledger.
* The deposit reference is intended to be encrypted so it's meaningless to anyone other than the institution.
*/
data class DepositPointer(val institution: Institution, val reference: OpaqueBytes)
/** A state representing a claim on the cash reserves of some institution */
data class CashState(
/** The institution that has this original cash deposit (propagated) */
val issuingInstitution: Institution,
/** Whatever internal ID the bank needs in order to locate that deposit, may be encrypted (propagated) */
val depositReference: OpaqueBytes,
/** Where the underlying currency backing this ledger entry can be found (propagated) */
val deposit: DepositPointer,
val amount: Amount,
@ -68,19 +71,18 @@ class CashContract : Contract {
// For each deposit that's represented in the inputs, group the inputs together and verify that the outputs
// balance, taking into account a possible exit command from that issuer.
var outputsLeft = cashOutputs.size
for ((pair, inputs) in cashInputs.groupBy { Pair(it.issuingInstitution, it.depositReference) }) {
val (issuer, depositRef) = pair
val outputs = cashOutputs.filter { it.issuingInstitution == issuer && it.depositReference == depositRef }
for ((deposit, inputs) in cashInputs.groupBy { it.deposit }) {
val outputs = cashOutputs.filter { it.deposit == deposit }
outputsLeft -= outputs.size
val inputAmount = inputs.map { it.amount }.sum()
val outputAmount = outputs.map { it.amount }.sumOrZero(currency)
val issuerCommand = args.filter { it.signingInstitution == issuer }.map { it.command as? ExitCashCommand }.filterNotNull().singleOrNull()
val issuerCommand = args.filter { it.signingInstitution == deposit.institution }.map { it.command as? ExitCashCommand }.filterNotNull().singleOrNull()
val amountExitingLedger = issuerCommand?.amount ?: Amount(0, inputAmount.currency)
requireThat {
"for deposit $depositRef at issuer ${issuer.name} the amounts balance" by (inputAmount == outputAmount + amountExitingLedger)
"for deposit ${deposit.reference} at issuer ${deposit.institution.name} the amounts balance" by (inputAmount == outputAmount + amountExitingLedger)
}
}

37
tests/CashTests.kt
View File

@ -8,15 +8,16 @@ import kotlin.test.assertFailsWith
class CashTests {
val inState = CashState(
issuingInstitution = MEGA_CORP,
depositReference = OpaqueBytes.of(1),
deposit = DepositPointer(MEGA_CORP, OpaqueBytes.of(1)),
amount = 1000.DOLLARS,
owner = DUMMY_PUBKEY_1
)
val outState = inState.copy(owner = DUMMY_PUBKEY_2)
val contract = CashContract()
fun CashState.editInstitution(institution: Institution) = copy(deposit = deposit.copy(institution = institution))
fun CashState.editDepositRef(ref: Byte) = copy(deposit = deposit.copy(reference = OpaqueBytes.of(ref)))
@Test
fun trivial() {
transaction {
@ -41,7 +42,7 @@ class CashTests {
}
transaction {
output { outState }
output { outState.copy(issuingInstitution = MINI_CORP) }
output { outState.editInstitution(MINI_CORP) }
contract `fails requirement` "no output states are unaccounted for"
}
// Simple reallocation works.
@ -95,14 +96,14 @@ class CashTests {
// Can't change issuer.
transaction {
input { inState }
output { outState.copy(issuingInstitution = MINI_CORP) }
output { outState.editInstitution(MINI_CORP) }
contract `fails requirement` "at issuer MegaCorp the amounts balance"
}
// Can't change deposit reference when splitting.
transaction {
input { inState }
output { outState.copy(depositReference = OpaqueBytes.of(0), amount = inState.amount / 2) }
output { outState.copy(depositReference = OpaqueBytes.of(1), amount = inState.amount / 2) }
output { outState.editDepositRef(0).copy(amount = inState.amount / 2) }
output { outState.editDepositRef(1).copy(amount = inState.amount / 2) }
contract `fails requirement` "for deposit [01] at issuer MegaCorp the amounts balance"
}
// Can't mix currencies.
@ -126,15 +127,15 @@ class CashTests {
// Can't have superfluous input states from different issuers.
transaction {
input { inState }
input { inState.copy(issuingInstitution = MINI_CORP) }
input { inState.editInstitution(MINI_CORP) }
output { outState }
contract `fails requirement` "at issuer MiniCorp the amounts balance"
}
// Can't combine two different deposits at the same issuer.
transaction {
input { inState }
input { inState.copy(depositReference = OpaqueBytes.of(3)) }
output { outState.copy(amount = inState.amount * 2, depositReference = OpaqueBytes.of(3)) }
input { inState.editDepositRef(3) }
output { outState.copy(amount = inState.amount * 2).editDepositRef(3) }
contract `fails requirement` "for deposit [01]"
}
}
@ -164,9 +165,9 @@ class CashTests {
// Multi-issuer case.
transaction {
input { inState }
input { inState.copy(issuingInstitution = MINI_CORP) }
input { inState.editInstitution(MINI_CORP) }
output { inState.copy(issuingInstitution = MINI_CORP, amount = inState.amount - 200.DOLLARS) }
output { inState.copy(amount = inState.amount - 200.DOLLARS).editInstitution(MINI_CORP) }
output { inState.copy(amount = inState.amount - 200.DOLLARS) }
arg(DUMMY_PUBKEY_1) { MoveCashCommand() }
@ -186,7 +187,7 @@ class CashTests {
transaction {
// Gather 2000 dollars from two different issuers.
input { inState }
input { inState.copy(issuingInstitution = MINI_CORP) }
input { inState.editInstitution(MINI_CORP) }
// Can't merge them together.
transaction {
@ -202,7 +203,7 @@ class CashTests {
// This works.
output { inState.copy(owner = DUMMY_PUBKEY_2) }
output { inState.copy(issuingInstitution = MINI_CORP, owner = DUMMY_PUBKEY_2) }
output { inState.copy(owner = DUMMY_PUBKEY_2).editInstitution(MINI_CORP) }
arg(DUMMY_PUBKEY_1) { MoveCashCommand() }
contract.accepts()
}
@ -216,10 +217,10 @@ class CashTests {
val OUR_PUBKEY_1 = DUMMY_PUBKEY_1
val THEIR_PUBKEY_1 = DUMMY_PUBKEY_2
val WALLET = listOf(
CashState(issuingInstitution = MEGA_CORP, depositReference = OpaqueBytes.of(1), amount = 100.DOLLARS, owner = OUR_PUBKEY_1),
CashState(issuingInstitution = MEGA_CORP, depositReference = OpaqueBytes.of(2), amount = 400.DOLLARS, owner = OUR_PUBKEY_1),
CashState(issuingInstitution = MINI_CORP, depositReference = OpaqueBytes.of(1), amount = 80.DOLLARS, owner = OUR_PUBKEY_1),
CashState(issuingInstitution = MINI_CORP, depositReference = OpaqueBytes.of(2), amount = 80.SWISS_FRANCS, owner = OUR_PUBKEY_1)
CashState(DepositPointer(MEGA_CORP, OpaqueBytes.of(1)), 100.DOLLARS, OUR_PUBKEY_1),
CashState(DepositPointer(MEGA_CORP, OpaqueBytes.of(2)), 400.DOLLARS, OUR_PUBKEY_1),
CashState(DepositPointer(MINI_CORP, OpaqueBytes.of(1)), 80.DOLLARS, OUR_PUBKEY_1),
CashState(DepositPointer(MINI_CORP, OpaqueBytes.of(2)), 80.SWISS_FRANCS, OUR_PUBKEY_1)
)
@Test