Use > and >= in for loops that decrement instead of increment

Signed-off-by: Graham <gpe@openrs2.dev>

deob-ast/src/main/java/dev/openrs2/deob/ast/transform/BinaryExprOrderTransformer.kt

@@ -4,6 +4,7 @@ import com.github.javaparser.ast.CompilationUnit
 import com.github.javaparser.ast.expr.BinaryExpr
 import dev.openrs2.deob.ast.Library
 import dev.openrs2.deob.ast.LibraryGroup
+import dev.openrs2.deob.ast.util.flip
 import dev.openrs2.deob.ast.util.isString
 import dev.openrs2.deob.ast.util.walk
 import javax.inject.Singleton
@@ -28,18 +29,4 @@ class BinaryExprOrderTransformer : Transformer() {
             }
         }
     }
-
-    private fun BinaryExpr.Operator.flip(): BinaryExpr.Operator? {
-        return when (this) {
-            BinaryExpr.Operator.PLUS, BinaryExpr.Operator.MULTIPLY -> this
-            BinaryExpr.Operator.EQUALS, BinaryExpr.Operator.NOT_EQUALS -> this
-            BinaryExpr.Operator.BINARY_AND, BinaryExpr.Operator.BINARY_OR -> this
-            BinaryExpr.Operator.XOR, BinaryExpr.Operator.OR, BinaryExpr.Operator.AND -> this
-            BinaryExpr.Operator.GREATER -> BinaryExpr.Operator.LESS
-            BinaryExpr.Operator.GREATER_EQUALS -> BinaryExpr.Operator.LESS_EQUALS
-            BinaryExpr.Operator.LESS -> BinaryExpr.Operator.GREATER
-            BinaryExpr.Operator.LESS_EQUALS -> BinaryExpr.Operator.GREATER_EQUALS
-            else -> null
-        }
-    }
 }

deob-ast/src/main/java/dev/openrs2/deob/ast/transform/ForLoopConditionTransformer.kt

@@ -1,10 +1,18 @@
 package dev.openrs2.deob.ast.transform
 
 import com.github.javaparser.ast.CompilationUnit
+import com.github.javaparser.ast.expr.AssignExpr
 import com.github.javaparser.ast.expr.BinaryExpr
+import com.github.javaparser.ast.expr.Expression
+import com.github.javaparser.ast.expr.UnaryExpr
+import com.github.javaparser.ast.expr.UnaryExpr.Operator.POSTFIX_DECREMENT
+import com.github.javaparser.ast.expr.UnaryExpr.Operator.POSTFIX_INCREMENT
+import com.github.javaparser.ast.expr.UnaryExpr.Operator.PREFIX_DECREMENT
+import com.github.javaparser.ast.expr.UnaryExpr.Operator.PREFIX_INCREMENT
 import com.github.javaparser.ast.stmt.ForStmt
 import dev.openrs2.deob.ast.Library
 import dev.openrs2.deob.ast.LibraryGroup
+import dev.openrs2.deob.ast.util.flip
 import dev.openrs2.deob.ast.util.hasSideEffects
 import dev.openrs2.deob.ast.util.walk
 import javax.inject.Singleton
@@ -13,6 +21,8 @@ import javax.inject.Singleton
 class ForLoopConditionTransformer : Transformer() {
     override fun transformUnit(group: LibraryGroup, library: Library, unit: CompilationUnit) {
         unit.walk { stmt: ForStmt ->
+            val updatedExprs = stmt.update.mapNotNull { it.getUpdatedExpr() }
+
             stmt.compare.ifPresent { compare ->
                 if (!compare.isBinaryExpr) {
                     return@ifPresent
@@ -23,14 +33,23 @@ class ForLoopConditionTransformer : Transformer() {
                     return@ifPresent
                 }
 
-                val flipped = when (expr.operator) {
-                    BinaryExpr.Operator.GREATER -> BinaryExpr.Operator.LESS
-                    BinaryExpr.Operator.GREATER_EQUALS -> BinaryExpr.Operator.LESS_EQUALS
-                    else -> return@ifPresent
+                val flipped = expr.operator.flip() ?: return@ifPresent
+
+                if (expr.left !in updatedExprs && expr.right in updatedExprs) {
+                    stmt.setCompare(BinaryExpr(expr.right, expr.left, flipped))
                 }
+            }
+        }
+    }
 
-                stmt.setCompare(BinaryExpr(expr.right, expr.left, flipped))
+    private fun Expression.getUpdatedExpr(): Expression? {
+        return when (this) {
+            is UnaryExpr -> when (operator) {
+                PREFIX_INCREMENT, PREFIX_DECREMENT, POSTFIX_INCREMENT, POSTFIX_DECREMENT -> expression
+                else -> null
             }
+            is AssignExpr -> target
+            else -> null
         }
     }
 }

deob-ast/src/main/java/dev/openrs2/deob/ast/util/ExprUtils.kt

@@ -122,3 +122,17 @@ fun Expression.hasSideEffects(): Boolean {
     // TODO(gpe): more cases
     return true
 }
+
+fun BinaryExpr.Operator.flip(): BinaryExpr.Operator? {
+    return when (this) {
+        BinaryExpr.Operator.PLUS, BinaryExpr.Operator.MULTIPLY -> this
+        BinaryExpr.Operator.EQUALS, BinaryExpr.Operator.NOT_EQUALS -> this
+        BinaryExpr.Operator.BINARY_AND, BinaryExpr.Operator.BINARY_OR -> this
+        BinaryExpr.Operator.XOR, BinaryExpr.Operator.OR, BinaryExpr.Operator.AND -> this
+        BinaryExpr.Operator.GREATER -> BinaryExpr.Operator.LESS
+        BinaryExpr.Operator.GREATER_EQUALS -> BinaryExpr.Operator.LESS_EQUALS
+        BinaryExpr.Operator.LESS -> BinaryExpr.Operator.GREATER
+        BinaryExpr.Operator.LESS_EQUALS -> BinaryExpr.Operator.GREATER_EQUALS
+        else -> null
+    }
+}