Refactor gncOwnerReduceSplitTo out of reduce_biggest_split

It can now be used both for scrubbing and when applying payments

src/engine/ScrubBusiness.c

@@ -64,41 +64,11 @@ static gboolean reduce_biggest_split (Split *splitA, Split *splitB)
 {
     gnc_numeric valA = xaccSplitGetValue (splitA);
     gnc_numeric valB = xaccSplitGetValue (splitB);
-    gnc_numeric new_val, rem_val;
-    Split *to_reduce, *rem_split;
-    Transaction *txn;
-    GNCLot *lot;
 
-    if (gnc_numeric_positive_p (valA) == gnc_numeric_positive_p (valB))
-        return FALSE; //Splits are not of opposite sign
-
-    if (gnc_numeric_equal (gnc_numeric_abs (valA), gnc_numeric_abs (valB)))
-        return FALSE; // Splits have an equal value (but with opposite sign - nothing to do
-    else if (gnc_numeric_compare (gnc_numeric_abs (valA), gnc_numeric_abs (valB)) > 0)
-    {
-        to_reduce = splitA;
-        new_val = gnc_numeric_neg (valB);
-    }
+    if (gnc_numeric_compare (gnc_numeric_abs (valA), gnc_numeric_abs (valB)) >= 0)
+        return gncOwnerReduceSplitTo (splitA, gnc_numeric_neg (valB));
     else
-    {
-        to_reduce = splitB;
-        new_val = gnc_numeric_neg (valA);
-    }
-
-    rem_val = gnc_numeric_add (valA, valB, GNC_DENOM_AUTO, GNC_HOW_DENOM_LCD); // note: values are of opposite sign
-    rem_split = xaccMallocSplit (xaccSplitGetBook (to_reduce));
-    xaccSplitCopyOnto (to_reduce, rem_split);
-    xaccSplitSetValue (rem_split, rem_val);
-
-    txn = xaccSplitGetParent (to_reduce);
-    xaccTransBeginEdit (txn);
-    xaccSplitSetValue (to_reduce, new_val);
-    xaccSplitSetParent (rem_split, txn);
-    xaccTransCommitEdit (txn);
-
-    lot = xaccSplitGetLot (to_reduce);
-    gnc_lot_add_split (lot, rem_split);
-    return TRUE;
+        return gncOwnerReduceSplitTo (splitB, gnc_numeric_neg (valA));
 }
 
 

src/engine/gncOwner.c

@@ -841,6 +841,38 @@ gncOwnerCreatePaymentLot (const GncOwner *owner, Transaction *txn,
     return payment_lot;
 }
 
+gboolean
+gncOwnerReduceSplitTo (Split *split, gnc_numeric target_value)
+{
+    gnc_numeric split_val = xaccSplitGetValue (split);
+    gnc_numeric rem_val;
+    Split *rem_split;
+    Transaction *txn;
+    GNCLot *lot;
+
+    if (gnc_numeric_positive_p (split_val) != gnc_numeric_positive_p (target_value))
+        return FALSE; // Split and target value have to be of the same sign
+
+    if (gnc_numeric_equal (split_val, target_value))
+        return FALSE; // Split already has the target value
+
+    rem_val = gnc_numeric_sub (split_val, target_value, GNC_DENOM_AUTO, GNC_HOW_DENOM_LCD); // note: values are of opposite sign
+    rem_split = xaccMallocSplit (xaccSplitGetBook (split));
+    xaccSplitCopyOnto (split, rem_split);
+    xaccSplitSetValue (rem_split, rem_val);
+
+    txn = xaccSplitGetParent (split);
+    xaccTransBeginEdit (txn);
+    xaccSplitSetValue (split, target_value);
+    xaccSplitSetParent (rem_split, txn);
+    xaccTransCommitEdit (txn);
+
+    lot = xaccSplitGetLot (split);
+    gnc_lot_add_split (lot, rem_split);
+
+    return TRUE;
+}
+
 void
 gncOwnerSetLotLinkMemo (Transaction *ll_txn)
 {

src/engine/gncOwner.h

@@ -266,6 +266,14 @@ gncOwnerApplyPayment (const GncOwner *owner, Transaction *txn, GList *lots,
                       gnc_numeric amount, gnc_numeric exch, Timespec date,
                       const char *memo, const char *num, gboolean auto_pay);
 
+/** Helper function to reduce the value of a split to target_value. To make
+ *  sure the split's parent transaction remains balanced a second split
+ *  will be created with the remainder. Similarly if the split was part of a
+ *  (business) lot, the remainder split will be added to the same lot to
+ *  keep the lot's balance unchanged.
+ */
+gboolean gncOwnerReduceSplitTo (Split *split, gnc_numeric target_value);
+
 /** To help a user understand what a lot link transaction does,
  *  we set the memo to name all documents involved in the link.
  *  The function below calculates this memo and sets it for