Optimize Imports: improve tooltip information

#KT-21374 Fixed

idea/src/org/jetbrains/kotlin/idea/imports/KotlinImportOptimizer.kt

@@ -46,16 +46,30 @@ import org.jetbrains.kotlin.resolve.scopes.utils.*
 class KotlinImportOptimizer : ImportOptimizer {
     override fun supports(file: PsiFile?) = file is KtFile
 
-    override fun processFile(file: PsiFile?): Runnable {
-        val ktFile = (file as? KtFile) ?: return Runnable { /* empty runnable */ }
-        val preparedImports = prepareImports(ktFile) ?: return Runnable { /* empty runnable */ }
+    override fun processFile(file: PsiFile?): ImportOptimizer.CollectingInfoRunnable {
+        val ktFile = (file as? KtFile) ?: return DO_NOTHING
+        val (add, remove, imports) = prepareImports(ktFile) ?: return DO_NOTHING
 
-        return Runnable {
-            replaceImports(ktFile, preparedImports)
+        return object : ImportOptimizer.CollectingInfoRunnable {
+            override fun getUserNotificationInfo(): String = if (remove == 0) "Rearranged imports"
+            else buildString {
+                append("Removed ")
+                append(remove)
+                append(" import")
+                if (remove > 1) append("s")
+                if (add > 0) {
+                    append(", added ")
+                    append(add)
+                    append(" import")
+                    if (add > 1) append("s")
+                }
+            }
+
+            override fun run() = replaceImports(ktFile, imports)
         }
     }
 
-    private fun prepareImports(file: KtFile): List<ImportPath>? {
+    private fun prepareImports(file: KtFile): OptimizeInformation? {
         ApplicationManager.getApplication().assertReadAccessAllowed()
 
         val moduleInfo = file.getNullableModuleInfo()
@@ -68,9 +82,17 @@ class KotlinImportOptimizer : ImportOptimizer {
 
         val descriptorsToImport = collectDescriptorsToImport(file)
 
-        return prepareOptimizedImports(file, descriptorsToImport)
+        val imports = prepareOptimizedImports(file, descriptorsToImport) ?: return null
+        val intersect = imports.intersect(oldImports.map { it.importPath })
+        return OptimizeInformation(
+            add = imports.size - intersect.size,
+            remove = oldImports.size - intersect.size,
+            imports = imports
+        )
     }
 
+    private data class OptimizeInformation(val add: Int, val remove: Int, val imports: List<ImportPath>)
+
     private class CollectUsedDescriptorsVisitor(file: KtFile) : KtVisitorVoid() {
         private val currentPackageName = file.packageFqName
         private val aliases: Map<FqName, List<Name>> = file.importDirectives
@@ -220,5 +242,11 @@ class KotlinImportOptimizer : ImportOptimizer {
             return bindingContext[BindingContext.SHORT_REFERENCE_TO_COMPANION_OBJECT, element as? KtReferenceExpression]?.let { listOf(it) }
                 ?: resolveToDescriptors(bindingContext)
         }
+
+        private val DO_NOTHING = object : ImportOptimizer.CollectingInfoRunnable {
+            override fun run() = Unit
+
+            override fun getUserNotificationInfo() = "Unused imports not found"
+        }
     }
 }

idea/testData/editor/optimizeImports/common/ArrayAccessExpression.kt

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Unused imports not found"
 import test1.MyClass
 import test1.get
 

idea/testData/editor/optimizeImports/common/ArrayAccessExpression.kt.after

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Unused imports not found"
 import test1.MyClass
 import test1.get
 

idea/testData/editor/optimizeImports/common/ClassMemberImported.kt

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Removed 5 imports, added 2 imports"
 package test
 
 import dependency.*

idea/testData/editor/optimizeImports/common/ClassMemberImported.kt.after

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Removed 5 imports, added 2 imports"
 package test
 
 import dependency.A

idea/testData/editor/optimizeImports/common/ConflictWithAlias2.kt

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Removed 4 imports, added 1 import"
 import duration.*
 import duration.hours as hour
 import duration.minutes as minute

idea/testData/editor/optimizeImports/common/ConflictWithAlias2.kt.after

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Removed 4 imports, added 1 import"
 import duration.minutes
 import duration.hours as hour
 import duration.seconds as second

idea/testData/editor/optimizeImports/common/CurrentPackage.kt

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Removed 1 import"
 package ppp
 
 import ppp.*

idea/testData/editor/optimizeImports/common/CurrentPackage.kt.after

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Removed 1 import"
 package ppp
 
 open class C

idea/testData/editor/optimizeImports/common/DefaultImportAndAlias.kt

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Rearranged imports"
 import pack1.a
 import pack1.a as a1
 import kotlin.collections.List

idea/testData/editor/optimizeImports/common/DefaultImportAndAlias.kt.after

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Rearranged imports"
 import pack1.a
 import kotlin.collections.List
 import kotlin.run

idea/testData/editor/optimizeImports/common/DefaultImportAndAlias2.kt

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Removed 1 import"
 import pack1.a
 import pack1.a as a1
 import kotlin.run as run1

idea/testData/editor/optimizeImports/common/DefaultImportAndAlias2.kt.after

@@ -1,3 +1,4 @@
+// WITH_MESSAGE: "Removed 1 import"
 import pack1.a
 import pack1.a as a1
 import kotlin.run as run1

idea/tests/org/jetbrains/kotlin/idea/imports/AbstractOptimizeImportsTest.kt

@@ -6,16 +6,23 @@
 package org.jetbrains.kotlin.idea.imports
 
 import com.intellij.testFramework.LightProjectDescriptor
+import junit.framework.TestCase
 import org.jetbrains.kotlin.AbstractImportsTest
 import org.jetbrains.kotlin.idea.test.KotlinStdJSProjectDescriptor
 import org.jetbrains.kotlin.idea.test.KotlinWithJdkAndRuntimeLightProjectDescriptor
 import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.test.InTextDirectivesUtils
 
 abstract class AbstractOptimizeImportsTest : AbstractImportsTest() {
     override fun doTest(file: KtFile): String {
         OptimizedImportsBuilder.testLog = StringBuilder()
         try {
-            KotlinImportOptimizer().processFile(file).run()
+            val optimizer = KotlinImportOptimizer().processFile(file)
+            optimizer.run()
+            val message = InTextDirectivesUtils.findStringWithPrefixes(file.text, "// WITH_MESSAGE: ")
+            if (message != null) {
+                TestCase.assertEquals(message, optimizer.userNotificationInfo)
+            }
             return OptimizedImportsBuilder.testLog.toString()
         } finally {
             OptimizedImportsBuilder.testLog = null