refactor: extract isValidContext to a base class for top-level strate…

…gies

src/main/kotlin/com/github/lppedd/highlighter/TopLevelReturnHighlightStrategy.kt

@@ -0,0 +1,28 @@
+package com.github.lppedd.highlighter
+
+import com.github.lppedd.highlighter.ReturnHighlightStrategy.PsiResult
+import com.github.lppedd.highlighter.ReturnHighlightStrategy.PsiResult.*
+import com.intellij.openapi.progress.ProgressManager
+import com.intellij.psi.PsiElement
+
+/**
+ * @author Edoardo Luppi
+ */
+abstract class TopLevelReturnHighlightStrategy<T : PsiElement> : ReturnHighlightStrategy<T> {
+  override fun isValidContext(psiElement: T): Boolean {
+    var psi: PsiElement? = psiElement
+
+    while (psi != null) {
+      ProgressManager.checkCanceled()
+      psi = when (check(psi)) {
+        VALID -> return true
+        INVALID -> return false
+        CONTINUE -> psi.parent
+      }
+    }
+
+    return false
+  }
+
+  protected abstract fun check(psiElement: PsiElement): PsiResult
+}

src/main/kotlin/com/github/lppedd/highlighter/java/JavaTopLevelHighlightStrategy.kt

@@ -1,43 +1,31 @@
 package com.github.lppedd.highlighter.java
 
-import com.github.lppedd.highlighter.ReturnHighlightStrategy
 import com.github.lppedd.highlighter.ReturnHighlightStrategy.PsiResult
 import com.github.lppedd.highlighter.ReturnHighlightStrategy.PsiResult.*
-import com.intellij.openapi.progress.ProgressManager
+import com.github.lppedd.highlighter.TopLevelReturnHighlightStrategy
 import com.intellij.psi.*
 import com.intellij.psi.util.PsiTreeUtil
 
 /**
  * @author Edoardo Luppi
  */
-object JavaTopLevelHighlightStrategy : ReturnHighlightStrategy<PsiKeyword> {
+object JavaTopLevelHighlightStrategy : TopLevelReturnHighlightStrategy<PsiKeyword>() {
   override fun isValidContext(psiElement: PsiKeyword): Boolean {
     // Note: it seems the Java Psi structure isn't quite right when errors are
     //  present. Thus, we need to intercept a lower-level PsiElement
-    if (psiElement.text != PsiKeyword.RETURN) {
-      return false
+    return if (psiElement.text != PsiKeyword.RETURN) {
+      false
+    } else {
+      super.isValidContext(psiElement)
     }
-
-    var psi: PsiElement? = psiElement
-
-    while (psi != null) {
-      ProgressManager.checkCanceled()
-      psi = when (check(psi)) {
-        VALID -> return true
-        INVALID -> return false
-        CONTINUE -> psi.parent
-      }
-    }
-
-    return false
   }
 
-  private fun check(psiElement: PsiElement): PsiResult =
-      when (psiElement) {
-        is PsiLambdaExpression -> checkLambdaExpression(psiElement)
-        is PsiMethod -> VALID
-        else -> CONTINUE
-      }
+  override fun check(psiElement: PsiElement): PsiResult =
+    when (psiElement) {
+      is PsiLambdaExpression -> checkLambdaExpression(psiElement)
+      is PsiMethod -> VALID
+      else -> CONTINUE
+    }
 
   private fun checkLambdaExpression(psiElement: PsiLambdaExpression): PsiResult {
     // Lambda expressions are valid only if immediately assigned to a Field

src/main/kotlin/com/github/lppedd/highlighter/javascript/JavaScriptTopLevelHighlightStrategy.kt

@@ -1,8 +1,8 @@
 package com.github.lppedd.highlighter.javascript
 
-import com.github.lppedd.highlighter.ReturnHighlightStrategy
 import com.github.lppedd.highlighter.ReturnHighlightStrategy.PsiResult
 import com.github.lppedd.highlighter.ReturnHighlightStrategy.PsiResult.*
+import com.github.lppedd.highlighter.TopLevelReturnHighlightStrategy
 import com.intellij.lang.javascript.psi.*
 import com.intellij.lang.javascript.psi.ecmal4.JSClass
 import com.intellij.lang.javascript.psi.ecmal4.JSQualifiedNamedElement
@@ -13,29 +13,14 @@ import com.intellij.psi.util.PsiTreeUtil
 /**
  * @author Edoardo Luppi
  */
-object JavaScriptTopLevelHighlightStrategy : ReturnHighlightStrategy<JSReturnStatement> {
-  override fun isValidContext(psiElement: JSReturnStatement): Boolean {
-    var psi: PsiElement? = psiElement
-
-    while (psi != null) {
-      ProgressManager.checkCanceled()
-      psi = when (check(psi)) {
-        VALID -> return true
-        INVALID -> return false
-        CONTINUE -> psi.parent
-      }
+object JavaScriptTopLevelHighlightStrategy : TopLevelReturnHighlightStrategy<JSReturnStatement>() {
+  override fun check(psiElement: PsiElement): PsiResult =
+    when (psiElement) {
+      is JSFunctionExpression -> checkJSFunctionExpression(psiElement)
+      is JSFunction -> checkJSFunction(psiElement)
+      else -> CONTINUE
     }
 
-    return false
-  }
-
-  private fun check(psiElement: PsiElement): PsiResult =
-      when (psiElement) {
-        is JSFunctionExpression -> checkJSFunctionExpression(psiElement)
-        is JSFunction -> checkJSFunction(psiElement)
-        else -> CONTINUE
-      }
-
   private fun checkJSFunctionExpression(psiElement: JSFunctionExpression): PsiResult {
     // Function Expressions are valid only if immediately assigned
     // to a Class Field, when in Class scope

src/main/kotlin/com/github/lppedd/highlighter/php/PhpTopLevelHighlightStrategy.kt

@@ -1,8 +1,8 @@
 package com.github.lppedd.highlighter.php
 
-import com.github.lppedd.highlighter.ReturnHighlightStrategy
 import com.github.lppedd.highlighter.ReturnHighlightStrategy.PsiResult
 import com.github.lppedd.highlighter.ReturnHighlightStrategy.PsiResult.*
+import com.github.lppedd.highlighter.TopLevelReturnHighlightStrategy
 import com.intellij.openapi.progress.ProgressManager
 import com.intellij.psi.PsiElement
 import com.intellij.psi.util.PsiTreeUtil
@@ -14,23 +14,8 @@ import com.jetbrains.php.lang.psi.elements.Function
 /**
  * @author Edoardo Luppi
  */
-object PhpTopLevelHighlightStrategy : ReturnHighlightStrategy<PhpReturn> {
-  override fun isValidContext(psiElement: PhpReturn): Boolean {
-    var psi: PsiElement? = psiElement
-
-    while (psi != null) {
-      ProgressManager.checkCanceled()
-      psi = when (check(psi)) {
-        VALID -> return true
-        INVALID -> return false
-        CONTINUE -> psi.parent
-      }
-    }
-
-    return false
-  }
-
-  private fun check(psiElement: PsiElement): PsiResult =
+object PhpTopLevelHighlightStrategy : TopLevelReturnHighlightStrategy<PhpReturn>() {
+  override fun check(psiElement: PsiElement): PsiResult =
     when (psiElement) {
       is PhpExpression -> checkExpression(psiElement)
       is Function -> checkFunction(psiElement)