From b10f2529fa106205fc99d7e3eec8aa80bfb487ce Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 17 Aug 2018 20:26:51 +0300
Subject: [PATCH] Merge and conditions if they only differ in one sub-condition

---
 source/condition.cpp | 80 ++++++++++++++++++++++++++++++++++++++++++--
 source/condition.h   |  5 +++
 2 files changed, 83 insertions(+), 2 deletions(-)

diff --git a/source/condition.cpp b/source/condition.cpp
index e9400c4..5978250 100644
--- a/source/condition.cpp
+++ b/source/condition.cpp
@@ -216,7 +216,7 @@ Condition *AndCondition::flatten(OrCondition *cond1, Condition *cond2) const
 	unsigned count = cond1->count();
 	for(unsigned i=0; i<count; ++i)
 		if(Condition *sub = dispatch_flatten(cond1->get(i).clone(), (i+1<count ? cond2->clone() : cond2)))
-			result->add(sub);
+			add_merged_to(sub, result, true);
 	delete cond1;
 
 	if(result->is_viable())
@@ -239,7 +239,7 @@ Condition *AndCondition::flatten(OrCondition *cond1, OrCondition *cond2) const
 	for(unsigned i=0; i<count1; ++i)
 		for(unsigned j=0; j<count2; ++j)
 			if(Condition *sub = dispatch_flatten(cond1->get(i).clone(), cond2->get(j).clone()))
-				result->add(sub);
+				add_merged_to(sub, result, true);
 
 	delete cond1;
 	delete cond2;
@@ -251,6 +251,82 @@ Condition *AndCondition::flatten(OrCondition *cond1, OrCondition *cond2) const
 	return 0;
 }
 
+bool AndCondition::can_merge(const Condition &other, const CompoundCondition &parent) const
+{
+	const AndCondition *other_and = dynamic_cast<const AndCondition *>(&other);
+	if(!other_and || !dynamic_cast<const OrCondition *>(&parent))
+		return false;
+
+	return merge(*this, *other_and, parent, 0);
+}
+
+AndCondition *AndCondition::merge(const vector<const Condition *> &conds, const CompoundCondition &parent) const
+{
+	if(conds.size()!=2)
+		return 0;
+
+	const AndCondition *and1 = dynamic_cast<const AndCondition *>(conds[0]);
+	const AndCondition *and2 = dynamic_cast<const AndCondition *>(conds[1]);
+	if(!and1 || !and2 || !dynamic_cast<const OrCondition *>(&parent))
+		return 0;
+
+	AndCondition *result = 0;
+	merge(*and1, *and2, parent, &result);
+	return result;
+}
+
+bool AndCondition::merge(const AndCondition &cond1, const AndCondition &cond2, const CompoundCondition &parent, AndCondition **result)
+{
+	if(cond1.count()!=cond2.count())
+		return false;
+
+	int merge1 = -1;
+	vector<bool> used(cond1.count(), false);
+	for(unsigned i=0; i<cond1.count(); ++i)
+	{
+		int match = -1;
+		for(unsigned j=0; (match<0 && j<cond2.count()); ++j)
+			if(!used[j] && cond1.get(i).equals(cond2.get(j)))
+				match = j;
+
+		if(match>=0)
+			used[match] = true;
+		else if(merge1<0)
+			merge1 = i;
+		else
+			return false;
+	}
+
+	if(merge1>=0)
+	{
+		vector<const Condition *> merge_conds(2, 0);
+		merge_conds[0] = &cond1.get(merge1);
+		for(unsigned i=0; (!merge_conds[1] && i<cond2.count()); ++i)
+			if(!used[i])
+				merge_conds[1] = &cond2.get(i);
+
+		if(!merge_conds[1] || !merge_conds[0]->can_merge(*merge_conds[1], parent))
+			return false;
+
+		if(result)
+		{
+			*result = new AndCondition;
+			(*result)->add(merge_conds[0]->merge(merge_conds, parent));
+		}
+	}
+	else if(result)
+		*result = new AndCondition;
+
+	if(result)
+	{
+		for(unsigned i=0; i<cond2.count(); ++i)
+			if(used[i])
+				(*result)->add(cond2.get(i).clone());
+	}
+
+	return true;
+}
+
 bool AndCondition::is_viable() const
 {
 	for(vector<Condition *>::const_iterator i=conditions.begin(); i!=conditions.end(); ++i)
diff --git a/source/condition.h b/source/condition.h
index 9d945c7..6b0cf6b 100644
--- a/source/condition.h
+++ b/source/condition.h
@@ -74,6 +74,11 @@ protected:
 	virtual Condition *flatten(OrCondition *, Condition *) const;
 	virtual Condition *flatten(OrCondition *, AndCondition *) const;
 	virtual Condition *flatten(OrCondition *, OrCondition *) const;
+public:
+	virtual bool can_merge(const Condition &, const CompoundCondition &) const;
+	virtual AndCondition *merge(const std::vector<const Condition *> &, const CompoundCondition &) const;
+private:
+	static bool merge(const AndCondition &, const AndCondition &, const CompoundCondition &, AndCondition **);
 public:
 	virtual bool is_viable() const;
 	virtual void add_lines(std::list<FilterStatement> &) const;
-- 
2.43.0