Calculating balances in the Sandbox.

At this point, the Sandbox goes through the whole
history of one account (= one IBAN) and calculates
the balance for it.

Later, a mechanism to calculate the balance only
based on a subset of such transactions should be
provided.

3 files changed, 96 insertions, 2 deletions

diff --git a/sandbox/src/main/kotlin/tech/libeufin/sandbox/EbicsProtocolBackend.kt b/sandbox/src/main/kotlin/tech/libeufin/sandbox/EbicsProtocolBackend.kt
index 4df1853f..0cc34380 100644
--- a/sandbox/src/main/kotlin/tech/libeufin/sandbox/EbicsProtocolBackend.kt
+++ b/sandbox/src/main/kotlin/tech/libeufin/sandbox/EbicsProtocolBackend.kt
@@ -307,7 +307,7 @@ fun buildCamtString(type: Int, subscriberIban: String, history: List<RawPayment>
                         }
                         element("Amt") {
                             attribute("Ccy", "EUR")
-                            text(Amount(0).toPlainString())
+                            text(balanceForAccount(subscriberIban).toString())
                         }
                         element("CdtDbtInd") {
                             // a temporary value to get the camt to validate.
diff --git a/sandbox/src/main/kotlin/tech/libeufin/sandbox/bankAccount.kt b/sandbox/src/main/kotlin/tech/libeufin/sandbox/bankAccount.kt
index a0c0d16b..d55f0912 100644
--- a/sandbox/src/main/kotlin/tech/libeufin/sandbox/bankAccount.kt
+++ b/sandbox/src/main/kotlin/tech/libeufin/sandbox/bankAccount.kt
@@ -5,16 +5,38 @@ import org.jetbrains.exposed.sql.select
 import org.jetbrains.exposed.sql.transactions.transaction
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
+import tech.libeufin.sandbox.BankAccountTransactionsTable.amount
 import tech.libeufin.util.RawPayment
 import tech.libeufin.util.importDateFromMillis
 import tech.libeufin.util.toDashedDate
+import java.math.BigInteger
 
 private val logger: Logger = LoggerFactory.getLogger("tech.libeufin.sandbox")
 
+fun balanceForAccount(iban: String): BigInteger {
+    logger.debug("Calculating balance for account: ${iban}")
+    var balance = BigInteger.ZERO
+    transaction {
+        BankAccountTransactionsTable.select {
+            BankAccountTransactionsTable.creditorIban eq iban
+        }.forEach {
+            val amount = BigInteger(it[amount])
+            balance += amount
+        }
+        BankAccountTransactionsTable.select {
+            BankAccountTransactionsTable.debtorIban eq iban
+        }.forEach {
+            val amount = BigInteger(it[amount])
+            balance -= amount
+        }
+    }
+    return balance
+}
+
 fun historyForAccount(iban: String): List<RawPayment> {
     val history = mutableListOf<RawPayment>()
+    logger.debug("Querying transactions involving: ${iban}")
     transaction {
-        logger.debug("Querying transactions involving: ${iban}")
         BankAccountTransactionsTable.select {
             BankAccountTransactionsTable.creditorIban eq iban or
                     (BankAccountTransactionsTable.debtorIban eq iban)
diff --git a/sandbox/src/test/kotlin/BalanceTest.kt b/sandbox/src/test/kotlin/BalanceTest.kt
new file mode 100644
index 00000000..a8c4d9e9
--- /dev/null
+++ b/sandbox/src/test/kotlin/BalanceTest.kt
@@ -0,0 +1,72 @@
+import org.jetbrains.exposed.dao.id.EntityID
+import org.jetbrains.exposed.sql.SchemaUtils
+import org.jetbrains.exposed.sql.insert
+import org.jetbrains.exposed.sql.transactions.transaction
+import org.junit.Test
+import tech.libeufin.sandbox.BankAccountTransactionsTable
+import tech.libeufin.sandbox.BankAccountsTable
+import tech.libeufin.sandbox.balanceForAccount
+import tech.libeufin.util.millis
+import java.math.BigInteger
+import java.time.LocalDateTime
+
+class BalanceTest {
+
+    @Test
+    fun balanceTest() {
+        withTestDatabase {
+            transaction {
+                SchemaUtils.create(BankAccountTransactionsTable)
+                BankAccountTransactionsTable.insert {
+                    it[account] = EntityID(0, BankAccountsTable)
+                    it[creditorIban] = "earns"
+                    it[creditorBic] = "BIC"
+                    it[creditorName] = "Creditor Name"
+                    it[debtorIban] = "spends"
+                    it[debtorBic] = "BIC"
+                    it[debtorName] = "Debitor Name"
+                    it[subject] = "deal"
+                    it[amount] = "1"
+                    it[date] = LocalDateTime.now().millis()
+                    it[currency] = "EUR"
+                    it[pmtInfId] = "0"
+                    it[direction] = "DBIT"
+                    it[accountServicerReference] = "test-account-servicer-reference"
+                }
+                BankAccountTransactionsTable.insert {
+                    it[account] = EntityID(0, BankAccountsTable)
+                    it[creditorIban] = "earns"
+                    it[creditorBic] = "BIC"
+                    it[creditorName] = "Creditor Name"
+                    it[debtorIban] = "spends"
+                    it[debtorBic] = "BIC"
+                    it[debtorName] = "Debitor Name"
+                    it[subject] = "deal"
+                    it[amount] = "1"
+                    it[date] = LocalDateTime.now().millis()
+                    it[currency] = "EUR"
+                    it[pmtInfId] = "0"
+                    it[direction] = "DBIT"
+                    it[accountServicerReference] = "test-account-servicer-reference"
+                }
+                BankAccountTransactionsTable.insert {
+                    it[account] = EntityID(0, BankAccountsTable)
+                    it[creditorIban] = "other"
+                    it[creditorBic] = "BIC"
+                    it[creditorName] = "Creditor Name"
+                    it[debtorIban] = "earns"
+                    it[debtorBic] = "BIC"
+                    it[debtorName] = "Debitor Name"
+                    it[subject] = "deal"
+                    it[amount] = "1"
+                    it[date] = LocalDateTime.now().millis()
+                    it[currency] = "EUR"
+                    it[pmtInfId] = "0"
+                    it[direction] = "DBIT"
+                    it[accountServicerReference] = "test-account-servicer-reference"
+                }
+                assert(BigInteger.ONE == balanceForAccount("earns"))
+            }
+        }
+    }
+}
\ No newline at end of file