add ui for 1st task

courseSection/accessingPsiElementsLesson/accessingPsiElementsClassProgrammingTask/src/main/kotlin/org/jetbrains/academy/plugin/course/dev/ui/DemoPanelFactory.kt

@@ -0,0 +1,98 @@
+package org.jetbrains.academy.plugin.course.dev.ui
+
+import com.intellij.notification.NotificationGroupManager
+import com.intellij.notification.NotificationType
+import com.intellij.openapi.application.WriteAction
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.wm.ToolWindow
+import com.intellij.openapi.wm.ToolWindowFactory
+import com.intellij.psi.PsiManager
+import com.intellij.testFramework.LightVirtualFile
+import com.intellij.ui.components.JBPanel
+import com.intellij.ui.components.JBScrollPane
+import com.intellij.ui.table.JBTable
+import com.intellij.util.ui.JBUI
+import org.jetbrains.academy.plugin.course.dev.access.countKtClasses
+import org.jetbrains.kotlin.idea.KotlinLanguage
+import java.awt.BorderLayout
+import java.awt.FlowLayout
+import java.awt.event.ActionListener
+import javax.swing.JButton
+import javax.swing.table.DefaultTableModel
+
+class DemoPanelFactory : ToolWindowFactory {
+    companion object {
+        private const val DEMO_PLUGIN_NOTIFICATION = "IdeDevCourseDemo"
+    }
+
+
+    // TODO use UI bundle instead of a string here?
+    private val runTaskMethodButton = JButton("Run task function").apply {
+        isBorderPainted = false
+        isVisible = true
+    }
+
+    lateinit var demoWindow: DemoPanelWindow
+    private val tableModel = DefaultTableModel()
+    private val resultsTable = JBTable(tableModel)
+    override fun createToolWindowContent(project: Project, toolWindow: ToolWindow) {
+        demoWindow = project.getService(DemoPanelService::class.java).demoWindow
+        demoWindow.jComponent.size = JBUI.size(toolWindow.component.width, toolWindow.component.height)
+        tableModel.addColumn("Test Number")
+        tableModel.addColumn("Your Output")
+        tableModel.addColumn("Expected Output")
+        val buttonPanel = JBPanel<JBPanel<*>>(FlowLayout()).apply {
+            add(runTaskMethodButton)
+        }
+        // Wrapping the resultsTable in a JScrollPane
+        val scrollPane = JBScrollPane(resultsTable)
+        scrollPane.preferredSize = JBUI.size(400, 100) // Set preferred size for scrollPane
+
+        val panel = JBPanel<JBPanel<*>>(BorderLayout()).apply {
+            add(buttonPanel, BorderLayout.SOUTH)
+            add(scrollPane, BorderLayout.CENTER)
+        }
+        toolWindow.component.add(panel)
+
+        // TODO add another listener? This example as a demo for now
+        runTaskMethodButton.setListener {
+            NotificationGroupManager.getInstance().getNotificationGroup(DEMO_PLUGIN_NOTIFICATION)
+                .createNotification("This panel demonstrates how the plugin works. The current task is a theory task, the plugin does nothing.", NotificationType.INFORMATION)
+                .notify(project)
+        }
+
+        runTaskMethodButton.addActionListener {
+            // Creating a virtual file with Kotlin content
+            val tempVfsFile = WriteAction.compute<LightVirtualFile, Exception> {
+                LightVirtualFile("MyClass.kt", KotlinLanguage.INSTANCE, """
+            class MyFirstClass {
+            }
+
+            class MySecondClass {
+            }
+        """.trimIndent())
+            }
+
+            // Convert virtual file to PSI file
+            val psiFile = PsiManager.getInstance(project).findFile(tempVfsFile)
+
+            // Call your function and get the result
+            psiFile?.let {
+                val result = countKtClasses(it)
+
+                // Display the result in the table
+                tableModel.setRowCount(0)
+                tableModel.addRow(arrayOf("1", result.toString(), 2))
+            }
+
+        }
+    }
+
+    private fun JButton.setListener(listener: ActionListener) {
+        actionListeners.forEach {
+            removeActionListener(it)
+        }
+        addActionListener(listener)
+    }
+
+}

courseSection/accessingPsiElementsLesson/accessingPsiElementsClassProgrammingTask/src/main/kotlin/org/jetbrains/academy/plugin/course/dev/ui/DemoPanelService.kt

@@ -0,0 +1,14 @@
+package org.jetbrains.academy.plugin.course.dev.ui
+
+import com.intellij.openapi.Disposable
+import com.intellij.openapi.components.Service
+import com.intellij.openapi.diagnostic.logger
+import com.intellij.openapi.project.Project
+
+@Service(Service.Level.PROJECT)
+class DemoPanelService : Disposable {
+    val demoWindow = DemoPanelWindow(this)
+    override fun dispose() {
+        logger<Project>().info("Jcef window service was disposed")
+    }
+}

courseSection/accessingPsiElementsLesson/accessingPsiElementsClassProgrammingTask/src/main/kotlin/org/jetbrains/academy/plugin/course/dev/ui/DemoPanelWindow.kt

@@ -0,0 +1,17 @@
+package org.jetbrains.academy.plugin.course.dev.ui
+
+import com.intellij.openapi.util.Disposer
+import com.intellij.ui.jcef.JBCefBrowser
+import javax.swing.JComponent
+
+class DemoPanelWindow(service: DemoPanelService) {
+    private val windowBrowser: JBCefBrowser = JBCefBrowser()
+
+    val jComponent: JComponent
+        get() = windowBrowser.component
+
+    init {
+        // TODO load the panel's content
+        Disposer.register(service, windowBrowser)
+    }
+}

courseSection/accessingPsiElementsLesson/accessingPsiElementsClassProgrammingTask/src/main/resources/META-INF/plugin.xml

@@ -0,0 +1,16 @@
+<idea-plugin>
+    <id>jetbrains.academy.plugin.course.dev.ui.demo</id>
+    <name>IDE Development Course Demo</name>
+    <vendor>JetBrains</vendor>
+
+    <depends>com.intellij.modules.platform</depends>
+    <depends>org.jetbrains.kotlin</depends>
+
+    <extensions defaultExtensionNs="com.intellij">
+        <notificationGroup id="IdeDevCourseDemo" displayType="BALLOON"/>
+
+        <toolWindow doNotActivateOnStart="true"
+                    factoryClass="org.jetbrains.academy.plugin.course.dev.ui.DemoPanelFactory"
+                    id="IDECourseDemo" anchor="right"/>
+    </extensions>
+</idea-plugin>

courseSection/accessingPsiElementsLesson/accessingPsiElementsClassProgrammingTask/task-info.yaml

@@ -5,3 +5,11 @@ files:
     visible: false
   - name: src/main/kotlin/org/jetbrains/academy/plugin/course/dev/access/ElementsCounter.kt
     visible: true
+  - name: src/main/kotlin/org/jetbrains/academy/plugin/course/dev/ui/DemoPanelService.kt
+    visible: false
+  - name: src/main/kotlin/org/jetbrains/academy/plugin/course/dev/ui/DemoPanelWindow.kt
+    visible: false
+  - name: src/main/kotlin/org/jetbrains/academy/plugin/course/dev/ui/DemoPanelFactory.kt
+    visible: false
+  - name: src/main/resources/META-INF/plugin.xml
+    visible: false