From d1b8fbd0941e32aee9dbbd332601c1886e6ef6a9 Mon Sep 17 00:00:00 2001
From: Graham <gpe@openrs2.dev>
Date: Mon, 20 Jul 2020 12:02:48 +0100
Subject: [PATCH] Remove redundant casts

Signed-off-by: Graham <gpe@openrs2.dev>
---
 .../openrs2/deob/ast/AstDeobfuscatorModule.kt |  2 +
 .../ast/transform/RedundantCastTransformer.kt | 83 +++++++++++++++++++
 2 files changed, 85 insertions(+)
 create mode 100644 deob-ast/src/main/java/dev/openrs2/deob/ast/transform/RedundantCastTransformer.kt

diff --git a/deob-ast/src/main/java/dev/openrs2/deob/ast/AstDeobfuscatorModule.kt b/deob-ast/src/main/java/dev/openrs2/deob/ast/AstDeobfuscatorModule.kt
index b20a9b4962..7c6375b5f3 100644
--- a/deob-ast/src/main/java/dev/openrs2/deob/ast/AstDeobfuscatorModule.kt
+++ b/deob-ast/src/main/java/dev/openrs2/deob/ast/AstDeobfuscatorModule.kt
@@ -17,6 +17,7 @@ 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.RedundantCastTransformer
 import dev.openrs2.deob.ast.transform.TernaryTransformer
 import dev.openrs2.deob.ast.transform.Transformer
 import dev.openrs2.deob.ast.transform.UnencloseTransformer
@@ -42,6 +43,7 @@ object AstDeobfuscatorModule : AbstractModule() {
         binder.addBinding().to(NewInstanceTransformer::class.java)
         binder.addBinding().to(IncrementTransformer::class.java)
         binder.addBinding().to(ForLoopConditionTransformer::class.java)
+        binder.addBinding().to(RedundantCastTransformer::class.java)
         binder.addBinding().to(GlTransformer::class.java)
         binder.addBinding().to(EncloseTransformer::class.java)
     }
diff --git a/deob-ast/src/main/java/dev/openrs2/deob/ast/transform/RedundantCastTransformer.kt b/deob-ast/src/main/java/dev/openrs2/deob/ast/transform/RedundantCastTransformer.kt
new file mode 100644
index 0000000000..3b5a92f0c7
--- /dev/null
+++ b/deob-ast/src/main/java/dev/openrs2/deob/ast/transform/RedundantCastTransformer.kt
@@ -0,0 +1,83 @@
+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.CastExpr
+import com.github.javaparser.ast.expr.Expression
+import com.github.javaparser.ast.expr.MethodCallExpr
+import com.github.javaparser.ast.expr.NullLiteralExpr
+import com.github.javaparser.ast.expr.ObjectCreationExpr
+import com.github.javaparser.ast.expr.VariableDeclarationExpr
+import com.github.javaparser.resolution.MethodAmbiguityException
+import dev.openrs2.deob.ast.Library
+import dev.openrs2.deob.ast.LibraryGroup
+import dev.openrs2.deob.ast.util.walk
+
+class RedundantCastTransformer : Transformer() {
+    override fun transformUnit(group: LibraryGroup, library: Library, unit: CompilationUnit) {
+        // remove double casts
+        unit.walk { expr: CastExpr ->
+            val innerExpr = expr.expression
+            if (innerExpr is CastExpr && expr.type == innerExpr.type) {
+                expr.expression = innerExpr.expression.clone()
+            }
+        }
+
+        // remove null argument casts if the call remains unambiguous
+        unit.walk { expr: MethodCallExpr ->
+            for (i in expr.arguments.indices) {
+                val arg = expr.arguments[i]
+                if (!isCastedNull(arg)) {
+                    continue
+                }
+
+                expr.arguments[i] = NullLiteralExpr()
+                try {
+                    expr.resolve()
+                } catch (ex: MethodAmbiguityException) {
+                    expr.arguments[i] = arg
+                }
+            }
+        }
+
+        unit.walk { expr: ObjectCreationExpr ->
+            for (i in expr.arguments.indices) {
+                val arg = expr.arguments[i]
+                if (!isCastedNull(arg)) {
+                    continue
+                }
+
+                expr.arguments[i] = NullLiteralExpr()
+                try {
+                    expr.resolve()
+                } catch (ex: MethodAmbiguityException) {
+                    expr.arguments[i] = arg
+                }
+            }
+        }
+
+        // remove null assignment casts
+        unit.walk { expr: VariableDeclarationExpr ->
+            for (variable in expr.variables) {
+                variable.initializer.ifPresent { initializer ->
+                    if (isCastedNull(initializer)) {
+                        initializer.replace(NullLiteralExpr())
+                    }
+                }
+            }
+        }
+
+        unit.walk { expr: AssignExpr ->
+            if (isCastedNull(expr.value)) {
+                expr.value = NullLiteralExpr()
+            }
+        }
+    }
+
+    private fun isCastedNull(expr: Expression): Boolean {
+        if (expr !is CastExpr) {
+            return false
+        }
+        return expr.expression is NullLiteralExpr
+    }
+}