Reworked balancing and rebalancing

schema/tables.sql

@@ -59,7 +59,8 @@ CREATE TABLE Transfer (
 );
 
 -- For internal purposes: Memory of rebalance triggers
-CREATE TABLE __DO_NOT_MANIPULATE__trigger_memory (d, c, m);
+-- Do not fiddle with it! I.e. if you do, don't expect any support.
+CREATE TABLE __INTERNAL_TRIGGER_STACK (id, d, c, m);
 
 -- Only for use of HTTP interface
 CREATE TABLE web_auth ( user_id primary key, password, grade not null, username, email );

schema/triggers/balanceTransfer.sql

@@ -1,5 +1,5 @@
-CREATE TRIGGER balanceTransfer
-     AFTER INSERT ON Transfer 
+CREATE TRIGGER linkTransferTightly
+    AFTER INSERT ON Transfer 
 BEGIN
 
   SELECT RAISE(FAIL, "It is not the debtor who is set to pay")
@@ -16,51 +16,58 @@ BEGIN
     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")
+  INSERT INTO __INTERNAL_TRIGGER_STACK
+      SELECT NEW.ROWID,
+          CASE remainingDebt   WHEN 0 THEN RAISE(FAIL, "Debt settled") ELSE NEW.billId END,
+          CASE remainingCredit WHEN 0 THEN RAISE(FAIL, "Credit spent") ELSE NEW.credId END,
+          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
       )
-      WHERE credId = (
-          SELECT targetCredit
-          FROM Debit
-          WHERE billId=NEW.billId
-      );
-
-  DELETE FROM __DO_NOT_MANIPULATE__trigger_memory;
+  ;
+
+END;
+
+CREATE TRIGGER reflectTransfer
+    AFTER INSERT ON __INTERNAL_TRIGGER_STACK
+    WHEN NEW.id > 0
+BEGIN
+
+  UPDATE Debit
+      SET paid = paid + NEW.m
+      WHERE billId = NEW.d;
+
+  UPDATE Credit
+      SET spent = spent + NEW.m
+      WHERE credId = NEW.c;
+
+  UPDATE Transfer
+      SET amount = ifnull(amount,0) + NEW.m
+      WHERE ROWID = NEW.id;
+
+  UPDATE Credit
+      SET value = value + NEW.m
+      WHERE credId = (
+          SELECT targetCredit
+          FROM Debit
+          WHERE billId = NEW.d
+      );
+
+  DELETE FROM __INTERNAL_TRIGGER_STACK WHERE id=NEW.id;
+
+END;
+
+CREATE TRIGGER refreshTransfer
+    AFTER UPDATE OF amount ON Transfer
+BEGIN
+
+    DELETE FROM Transfer
+        WHERE ROWID = NEW.ROWID AND amount = 0;
+
+    UPDATE Transfer
+        SET timestamp=CURRENT_TIMESTAMP
+        WHERE ROWID=NEW.ROWID;   
 
 END;
 

schema/triggers/enforceDebtImmutableOutsideTrigger.sql

@@ -2,11 +2,8 @@
 -- 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)
+    WHEN NOT EXISTS (SELECT * FROM __INTERNAL_TRIGGER_STACK LIMIT 1)
 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;
+    SELECT RAISE(FAIL, "paid is set and adjusted automatically according to added Transfer records");
 END;
 

schema/triggers/enforceFixedCredit.sql

@@ -1,7 +1,7 @@
 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)
+     AND NOT EXISTS (SELECT * FROM __INTERNAL_TRIGGER_STACK)
 BEGIN
     SELECT RAISE(FAIL, "Credit involved in transactions to revoke at first");
 END;

schema/triggers/enforceFixedDebit.sql

@@ -1,6 +1,7 @@
 CREATE TRIGGER enforceFixedDebit
     BEFORE UPDATE OF debtor, transferCredit, value ON Debit
     WHEN EXISTS (SELECT * FROM Transfer WHERE billId=NEW.billId)
+     AND NOT EXISTS (SELECT * FROM __INTERNAL_TRIGGER_STACK LIMIT 1)
 BEGIN
     SELECT RAISE(FAIL, "Debt is involved in transfers to revoke at first");
 END;

schema/triggers/enforceImmutableTransfer.sql

@@ -1,6 +1,7 @@
 CREATE TRIGGER enforceImmutableTransfer
     BEFORE UPDATE ON Transfer
     WHEN OLD.amount IS NOT NULL
+      AND NOT EXISTS (SELECT * FROM __INTERNAL_TRIGGER_STACK)
 BEGIN
     SELECT RAISE(FAIL, "Transfer cannot be updated, but needs to be replaced to make triggers run");
 END;

schema/triggers/enforceSpentImmutableOutsideTrigger.sql

@@ -2,11 +2,8 @@
 -- 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)
+    WHEN NOT EXISTS (SELECT * FROM __INTERNAL_TRIGGER_STACK)
 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;
+    SELECT RAISE(FAIL, "spent is set and adjusted automatically according to added Transfer records");
 END;
 

schema/triggers/rebalanceIncreasedCredit.sql

@@ -3,11 +3,12 @@
 -- That way, a transfer may issue recursively chained transfers.
 CREATE TRIGGER rebalanceIncreasedCredit
     AFTER UPDATE OF value ON Credit
-WHEN NEW.value > OLD.spent
+    WHEN NEW.value > OLD.value
 BEGIN
 
-    REPLACE INTO Transfer (credId, billId)
-        SELECT OLD.credId, t.billId
+    INSERT INTO __INTERNAL_TRIGGER_STACK
+        SELECT t.ROWID, NEW.value, ca.difference,
+            min(ca.difference, NEW.value - OLD.value)
         FROM Transfer t
           JOIN CurrentArrears ca ON t.billId = ca.billId
         WHERE OLD.credId = t.credId

schema/triggers/rebalanceReducedCredit.sql

@@ -2,42 +2,50 @@
 -- 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
+    BEFORE 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;
-
+    INSERT INTO __INTERNAL_TRIGGER_STACK (id) VALUES (-NEW.credId);
+    UPDATE __INTERNAL_TRIGGER_STACK SET c=OLD.spent-NEW.value;
+    DELETE FROM __INTERNAL_TRIGGER_STACK WHERE id=-NEW.credId;
 END;
 
+CREATE TRIGGER _inner_rebalanceReducedCredit
+    AFTER UPDATE OF c ON __INTERNAL_TRIGGER_STACK
+BEGIN
+
+    UPDATE __INTERNAL_TRIGGER_STACK
+        SET d = (
+            SELECT ROWID
+            FROM Transfer
+            WHERE credId = abs(OLD.id)
+            ORDER BY timestamp DESC
+            LIMIT 1
+          )
+        WHERE id = OLD.id
+    ;
+
+    UPDATE __INTERNAL_TRIGGER_STACK
+        SET m = min((
+            SELECT amount
+            FROM Transfer
+            WHERE credId = abs(OLD.id)
+            ORDER BY timestamp DESC
+            LIMIT 1
+          ), NEW.c)
+        WHERE id = OLD.id
+    ;
+
+    INSERT INTO __INTERNAL_TRIGGER_STACK
+        SELECT d, billId, abs(OLD.id), -m
+          FROM __INTERNAL_TRIGGER_STACK s
+              JOIN Transfer t ON t.ROWID=d
+          WHERE id = OLD.id AND m > 0
+    ;
+
+    UPDATE __INTERNAL_TRIGGER_STACK
+        SET c = NEW.c-m
+        WHERE id = OLD.id AND m > 0
+    ; -- recurse
+
+END;

schema/triggers/revokeTransfer.sql

@@ -1,27 +1,11 @@
 CREATE TRIGGER revokeTransfer
     BEFORE DELETE ON Transfer
+    WHEN OLD.amount > 0
 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;
+  INSERT INTO __INTERNAL_TRIGGER_STACK VALUES (
+      OLD.ROWID, OLD.billId, OLD.credId, -OLD.amount
+  );
 
 END;
 

t/schema.t

@@ -125,5 +125,6 @@ $db->make_transfers( q{*} => q{*} );
 
 is $rose->available_credits->get_column("difference")->sum, 3600, "partial use of credit";
 is $db->resultset("Balance")->find("alex")->earned, '10800', 'indirect transfers';
+is $db->resultset("Balance")->find("Club")->available, '0', '   ... spent increased';
 
 done_testing();