From 81dc89994d76128c339628ee51e72425f1b9f691 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timo=20Westk=C3=A4mper?= <timo.westkamper@gmail.com>
Date: Wed, 21 Oct 2015 22:53:36 +0300
Subject: [PATCH] Simplify operations

---
 .../com/querydsl/core/types/Template.java     | 42 +++++++++++++++++++
 .../com/querydsl/jpa/JPQLSerializerTest.java  |  2 +-
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/querydsl-core/src/main/java/com/querydsl/core/types/Template.java b/querydsl-core/src/main/java/com/querydsl/core/types/Template.java
index 9a323a343..7b84f46ea 100644
--- a/querydsl-core/src/main/java/com/querydsl/core/types/Template.java
+++ b/querydsl-core/src/main/java/com/querydsl/core/types/Template.java
@@ -16,11 +16,13 @@ package com.querydsl.core.types;
 import java.io.Serializable;
 import java.math.BigDecimal;
 import java.util.List;
+import java.util.Set;
 
 import javax.annotation.concurrent.Immutable;
 
 import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Sets;
 import com.querydsl.core.types.dsl.Expressions;
 import com.querydsl.core.util.MathUtils;
 
@@ -36,6 +38,8 @@ public final class Template implements Serializable {
 
     private static final long serialVersionUID = -1697705745769542204L;
 
+    private static final Set<? extends Operator> CONVERTIBLES = Sets.immutableEnumSet(Ops.ADD, Ops.SUB);
+
     /**
      * General template element
      */
@@ -224,6 +228,26 @@ public final class Template implements Serializable {
             } else {
                 Expression<?> expr1 = asExpression(arg1);
                 Expression<?> expr2 = asExpression(arg2);
+
+                if (arg2 instanceof Number) {
+                    if (CONVERTIBLES.contains(operator) && expr1 instanceof com.querydsl.core.types.Operation) {
+                        com.querydsl.core.types.Operation operation = (com.querydsl.core.types.Operation) expr1;
+                        if (CONVERTIBLES.contains(operation.getOperator()) && operation.getArg(1) instanceof Constant) {
+                            Number num1 = ((Constant<Number>) operation.getArg(1)).getConstant();
+                            Number num2;
+                            if (operator == operation.getOperator()) {
+                                num2 = MathUtils.result(num1, (Number) arg2, Ops.ADD);
+                            } else if (operator == Ops.ADD) {
+                                num2 = MathUtils.result((Number) arg2, num1, Ops.SUB);
+                            } else {
+                                num2 = MathUtils.result(num1, (Number) arg2, Ops.SUB);
+                            }
+                            return ExpressionUtils.operation(expr1.getType(), operator,
+                                    operation.getArg(0), Expressions.constant(num2));
+                        }
+                    }
+                }
+
                 return ExpressionUtils.operation(expr1.getType(), operator, expr1, expr2);
             }
         }
@@ -271,6 +295,24 @@ public final class Template implements Serializable {
                 return MathUtils.result(asNumber(arg1), arg2, operator);
             } else {
                 Expression<?> expr1 = asExpression(arg1);
+
+                if (CONVERTIBLES.contains(operator) && expr1 instanceof com.querydsl.core.types.Operation) {
+                    com.querydsl.core.types.Operation operation = (com.querydsl.core.types.Operation) expr1;
+                    if (CONVERTIBLES.contains(operation.getOperator()) && operation.getArg(1) instanceof Constant) {
+                        Number num1 = ((Constant<Number>) operation.getArg(1)).getConstant();
+                        Number num2;
+                        if (operator == operation.getOperator()) {
+                            num2 = MathUtils.result(num1, arg2, Ops.ADD);
+                        } else if (operator == Ops.ADD) {
+                            num2 = MathUtils.result(arg2, num1, Ops.SUB);
+                        } else {
+                            num2 = MathUtils.result(num1, arg2, Ops.SUB);
+                        }
+                        return ExpressionUtils.operation(expr1.getType(), operator,
+                                operation.getArg(0), Expressions.constant(num2));
+                    }
+                }
+
                 return ExpressionUtils.operation(expr1.getType(), operator, expr1, expr2);
             }
         }
diff --git a/querydsl-jpa/src/test/java/com/querydsl/jpa/JPQLSerializerTest.java b/querydsl-jpa/src/test/java/com/querydsl/jpa/JPQLSerializerTest.java
index c0a6e30c8..450b0a904 100644
--- a/querydsl-jpa/src/test/java/com/querydsl/jpa/JPQLSerializerTest.java
+++ b/querydsl-jpa/src/test/java/com/querydsl/jpa/JPQLSerializerTest.java
@@ -192,7 +192,7 @@ public class JPQLSerializerTest {
         JPQLSerializer serializer = new JPQLSerializer(HQLTemplates.DEFAULT);
         QCat cat = QCat.cat;
         serializer.handle(cat.name.substring(cat.name.length().subtract(1), 1));
-        assertEquals("substring(cat.name,(length(cat.name) - ?1 + ?1),(?1 - (length(cat.name) - ?1)))", serializer.toString());
+        assertEquals("substring(cat.name,(length(cat.name) + ?1),(?2 - (length(cat.name) - ?2)))", serializer.toString());
     }
 
     @Test