Refactorization and splitting of schema files

schema/triggers/balanceTransfer.sql

@@ -0,0 +1,66 @@
+CREATE TRIGGER balanceTransfer
+     AFTER INSERT ON Transfer 
+BEGIN
+
+  SELECT RAISE(FAIL, "It is not the debtor who is set to pay")
+    WHERE (SELECT debtor FROM Debit WHERE billId=NEW.billId)
+       != (SELECT account FROM Credit WHERE credId=NEW.credId)
+    ;
+
+  SELECT RAISE(FAIL, "Target of a debit cannot be an incoming payment")
+  FROM Credit c
+    JOIN Debit d ON c.credId = d.targetCredit
+  WHERE c.credId = NEW.credId
+    AND c.value > 0
+  GROUP BY c.credId
+    HAVING count(d.billId) == 0
+  ;
+
+  INSERT INTO __DO_NOT_MANIPULATE__trigger_memory
+     SELECT remainingDebt, remainingCredit, min(remainingDebt,remainingCredit) 
+     FROM (SELECT
+         (SELECT value - paid FROM Debit WHERE billId=NEW.billId) AS remainingDebt, 
+         (SELECT value - spent FROM Credit WHERE credId=NEW.credId) AS remainingCredit
+     )
+  ;
+
+  UPDATE Debit
+      SET paid = paid + CASE
+        WHEN (SELECT d FROM __DO_NOT_MANIPULATE__trigger_memory) <= 0
+          THEN RAISE(FAIL, "Debt settled")
+        ELSE
+          (SELECT m FROM __DO_NOT_MANIPULATE__trigger_memory)
+      END
+      WHERE billId=NEW.billId;
+
+  UPDATE Credit
+      SET spent = spent + CASE
+        WHEN (SELECT c FROM __DO_NOT_MANIPULATE__trigger_memory) <= 0
+          THEN RAISE(FAIL, "Credit spent")
+        ELSE IFNULL(
+          (SELECT m FROM __DO_NOT_MANIPULATE__trigger_memory),
+          RAISE(FAIL,"Oops, lost __DO_NOT_MANIPULATE__trigger_memory record before increasing spent")
+        )
+      END
+      WHERE credId=NEW.credId;
+
+  UPDATE Transfer
+      SET amount = (SELECT m FROM __DO_NOT_MANIPULATE__trigger_memory)
+      WHERE billId=NEW.billId AND credId=NEW.credId
+        ;
+
+  UPDATE Credit
+      SET value = value + IFNULL(
+          (SELECT m FROM __DO_NOT_MANIPULATE__trigger_memory),
+          RAISE(FAIL, "Oops, lost __DO_NOT_MANIPULATE__trigger_memory record before increasing value")
+      )
+      WHERE credId = (
+          SELECT targetCredit
+          FROM Debit
+          WHERE billId=NEW.billId
+      );
+
+  DELETE FROM __DO_NOT_MANIPULATE__trigger_memory;
+
+END;
+

schema/triggers/checkIBANatTransfer.sql

@@ -0,0 +1,13 @@
+CREATE TRIGGER checkIBANatTransfer
+    BEFORE INSERT ON Debit
+    WHEN NEW.targetCredit IS NULL
+BEGIN
+   SELECT RAISE(FAIL, "IBAN used does not match IBAN currently stored in account record")
+   FROM (
+      SELECT instr(NEW.purpose, IBAN) AS fnd
+      FROM Account
+      WHERE ID=NEW.debtor
+   ) AS matchingIBAN
+   WHERE fnd IS NULL OR fnd = 0;
+END;
+

schema/triggers/enforcDebtImmutableOutsideTrigger.sql

@@ -0,0 +1,12 @@
+-- Prevent modification of paid value outside triggers which must adjust it exclusively
+-- when new transfer records are inserted
+CREATE TRIGGER enforceDebtImmutableOutsideTrigger
+    BEFORE UPDATE OF paid ON Debit
+    WHEN NOT EXISTS (SELECT * FROM Transfer t WHERE NEW.billId=t.billId AND amount IS NULL)
+BEGIN
+    SELECT RAISE(FAIL, "paid is set and adjusted automatically according to added Transfer records")
+    WHERE (NEW.paid + IFNULL(
+            (SELECT m FROM __DO_NOT_MANIPULATE__trigger_memory WHERE c IS NULL AND d IS NULL), 0
+        ) ) <> OLD.paid;
+END;
+

schema/triggers/enforceFixedCredit.sql

@@ -0,0 +1,8 @@
+CREATE TRIGGER enforceFixedCredit
+    BEFORE UPDATE OF account, value ON Credit
+    WHEN EXISTS (SELECT * FROM Transfer WHERE credId=NEW.credId)
+     AND NOT EXISTS (SELECT * FROM __DO_NOT_MANIPULATE__trigger_memory)
+BEGIN
+    SELECT RAISE(FAIL, "Credit involved in transactions to revoke at first");
+END;
+

schema/triggers/enforceFixedDebit.sql

@@ -0,0 +1,7 @@
+CREATE TRIGGER enforceFixedDebit
+    BEFORE UPDATE OF debtor, transferCredit, value ON Debit
+    WHEN EXISTS (SELECT * FROM Transfer WHERE billId=NEW.billId)
+BEGIN
+    SELECT RAISE(FAIL, "Debt is involved in transfers to revoke at first");
+END;
+

schema/triggers/enforceImmutableTransfer.sql

@@ -0,0 +1,7 @@
+CREATE TRIGGER enforceImmutableTransfer
+    BEFORE UPDATE ON Transfer
+    WHEN OLD.amount IS NOT NULL
+BEGIN
+    SELECT RAISE(FAIL, "Transfer cannot be updated, but needs to be replaced to make triggers run");
+END;
+

schema/triggers/enforceSpentImmutableOutsideTrigger.sql

@@ -0,0 +1,12 @@
+-- Prevent modification of spent value outside triggers which must adjust it exclusively
+-- when new transfer records are inserted
+CREATE TRIGGER enforceSpentImmutableOutsideTrigger
+    BEFORE UPDATE OF spent ON Credit
+    WHEN NOT EXISTS (SELECT * FROM Transfer t WHERE NEW.credId=t.credId AND amount IS NULL)
+BEGIN
+    SELECT RAISE(FAIL, "spent is set and adjusted automatically according to added Transfer records")
+    WHERE (NEW.spent + IFNULL(
+            (SELECT m FROM __DO_NOT_MANIPULATE__trigger_memory WHERE c IS NULL AND d IS NULL), 0
+        ) ) <> OLD.spent;
+END;
+

schema/triggers/enforceZeroPaidAtStart.sql

@@ -0,0 +1,7 @@
+CREATE TRIGGER enforceZeroPaidAtStart
+    BEFORE INSERT ON Debit
+BEGIN
+    SELECT RAISE(FAIL, "Debt must be initially unpaid")
+    WHERE NEW.paid <> 0;
+END;
+

schema/triggers/enforceZeroSpentAtStart.sql

@@ -0,0 +1,7 @@
+CREATE TRIGGER enforceZeroSpentAtStart
+    BEFORE INSERT ON Credit
+BEGIN
+    SELECT RAISE(FAIL, "credit must be initially unused")
+    WHERE NEW.spent != 0;
+END;
+

schema/triggers/rebalanceIncreasedCredit.sql

@@ -0,0 +1,16 @@
+-- When we enter a transfer, the targetCredit of the associated bill might already be the credId
+-- of a transfer for other dues itself. We can update (replace) the transfer for an unfullfilled one.
+-- That way, a transfer may issue recursively chained transfers.
+CREATE TRIGGER rebalanceIncreasedCredit
+    AFTER UPDATE OF value ON Credit
+WHEN NEW.value > OLD.spent
+BEGIN
+
+    REPLACE INTO Transfer (credId, billId)
+        SELECT OLD.credId, t.billId
+        FROM Transfer t
+          JOIN CurrentArrears ca ON t.billId = ca.billId
+        WHERE OLD.credId = t.credId
+    ;
+
+END;

schema/triggers/rebalanceReducedCredit.sql

@@ -0,0 +1,43 @@
+-- When a transfer is revoked, the targetCredit of the associated bill is reduced. Hence we must
+-- check if we can still have paid the debts linked to this transfer in an "is paid from" relation,
+-- otherwise we have to revoke these transfers as well.
+CREATE TRIGGER rebalanceReducedCredit
+    AFTER UPDATE OF value ON Credit
+WHEN NEW.value < OLD.spent
+BEGIN
+
+    REPLACE INTO __DO_NOT_MANIPULATE__trigger_memory (d, m)
+    SELECT
+        'from_' || NEW.credId,
+        billId 
+    FROM Transfer
+    WHERE credId = NEW.credId
+    ORDER BY timestamp DESC
+    LIMIT 1
+    ;
+
+    DELETE
+    FROM Transfer
+    WHERE credId = NEW.credId
+      AND billId IN (
+        SELECT billId
+        FROM __DO_NOT_MANIPULATE__trigger_memory
+        WHERE c = 'from_' || NEW.credId
+      )
+    ;
+
+    INSERT INTO Transfer (credId, billId)
+        SELECT NEW.credId, m
+        FROM __DO_NOT_MANIPULATE__trigger_memory
+        WHERE d = 'from_' || NEW.credId
+          AND NEW.value > (
+              SELECT spent
+              FROM Credit
+              WHERE credId = NEW.credId
+          )
+    ;
+
+    DELETE FROM __DO_NOT_MANIPULATE__trigger_memory WHERE d = 'from_' || NEW.credId;
+
+END;
+

schema/triggers/revokeTransfer.sql

@@ -0,0 +1,27 @@
+CREATE TRIGGER revokeTransfer
+    BEFORE DELETE ON Transfer
+BEGIN
+
+  INSERT INTO __DO_NOT_MANIPULATE__trigger_memory VALUES (null,null,OLD.amount);
+
+  UPDATE Debit
+      SET paid = paid - OLD.amount
+      WHERE billId=OLD.billId
+      ;
+
+  UPDATE Credit
+      SET value = value - OLD.amount
+      WHERE credId = (
+          SELECT targetCredit
+          FROM Debit
+          WHERE billId=OLD.billId
+      );
+
+  UPDATE Credit
+      SET spent = spent - OLD.amount
+      WHERE credId = OLD.credId;
+
+  DELETE FROM __DO_NOT_MANIPULATE__trigger_memory;
+
+END;
+