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.

2 files changed, 24 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)