From 7d1dc59d6a0dedbd2aa273aee8b99fed35ef2059 Mon Sep 17 00:00:00 2001
From: Graham <gpe@openrs2.dev>
Date: Thu, 9 Jan 2020 20:27:31 +0000
Subject: [PATCH] Convert pre-increments to post-increments where possible

---
 .../dev/openrs2/deob/ast/AstDeobfuscator.kt   |  2 +
 .../ast/transform/IncrementTransformer.kt     | 40 +++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 deob-ast/src/main/java/dev/openrs2/deob/ast/transform/IncrementTransformer.kt

diff --git a/deob-ast/src/main/java/dev/openrs2/deob/ast/AstDeobfuscator.kt b/deob-ast/src/main/java/dev/openrs2/deob/ast/AstDeobfuscator.kt
index fcfb3bc1..be62dd1b 100644
--- a/deob-ast/src/main/java/dev/openrs2/deob/ast/AstDeobfuscator.kt
+++ b/deob-ast/src/main/java/dev/openrs2/deob/ast/AstDeobfuscator.kt
@@ -15,6 +15,7 @@ import dev.openrs2.deob.ast.transform.BitMaskTransformer
 import dev.openrs2.deob.ast.transform.ComplementTransformer
 import dev.openrs2.deob.ast.transform.EncloseTransformer
 import dev.openrs2.deob.ast.transform.IfElseTransformer
+import dev.openrs2.deob.ast.transform.IncrementTransformer
 import dev.openrs2.deob.ast.transform.NegativeLiteralTransformer
 import dev.openrs2.deob.ast.transform.NewInstanceTransformer
 import dev.openrs2.deob.ast.transform.TernaryTransformer
@@ -87,6 +88,7 @@ class AstDeobfuscator(private val modules: List<Path>) {
             BitMaskTransformer(),
             ValueOfTransformer(),
             NewInstanceTransformer(),
+            IncrementTransformer(),
             EncloseTransformer()
         )
     }
diff --git a/deob-ast/src/main/java/dev/openrs2/deob/ast/transform/IncrementTransformer.kt b/deob-ast/src/main/java/dev/openrs2/deob/ast/transform/IncrementTransformer.kt
new file mode 100644
index 00000000..788b0a43
--- /dev/null
+++ b/deob-ast/src/main/java/dev/openrs2/deob/ast/transform/IncrementTransformer.kt
@@ -0,0 +1,40 @@
+package dev.openrs2.deob.ast.transform
+
+import com.github.javaparser.ast.CompilationUnit
+import com.github.javaparser.ast.Node
+import com.github.javaparser.ast.expr.UnaryExpr
+import com.github.javaparser.ast.stmt.ExpressionStmt
+import com.github.javaparser.ast.stmt.ForStmt
+import dev.openrs2.deob.ast.util.walk
+
+class IncrementTransformer : Transformer() {
+    override fun transform(unit: CompilationUnit) {
+        unit.walk(Node.TreeTraversal.POSTORDER) { stmt: ExpressionStmt ->
+            if (!stmt.expression.isUnaryExpr) {
+                return@walk
+            }
+
+            val unaryExpr = stmt.expression.asUnaryExpr()
+            unaryExpr.operator = prefixToPostfix(unaryExpr.operator)
+        }
+
+        unit.walk(Node.TreeTraversal.POSTORDER) { stmt: ForStmt ->
+            stmt.update.forEach {
+                if (!it.isUnaryExpr) {
+                    return@forEach
+                }
+
+                val unaryExpr = it.asUnaryExpr()
+                unaryExpr.operator = prefixToPostfix(unaryExpr.operator)
+            }
+        }
+    }
+
+    companion object {
+        fun prefixToPostfix(operator: UnaryExpr.Operator) = when (operator) {
+            UnaryExpr.Operator.PREFIX_INCREMENT -> UnaryExpr.Operator.POSTFIX_INCREMENT
+            UnaryExpr.Operator.PREFIX_DECREMENT -> UnaryExpr.Operator.POSTFIX_DECREMENT
+            else -> operator
+        }
+    }
+}