Provide placeholder completion cell editor

src/main/kotlin/de/idetools/filename_template/settings/FilenameTemplateSettingsComponent.kt

@@ -26,6 +26,9 @@ class FilenameTemplateSettingsComponent(val filenameTemplates: ArrayList<Filenam
         activeColumn.resizable = false
         activeColumn.maxWidth = determineRequiredWidth(activeColumn)
 
+        val templateColumn = filenameTemplateTable.columnModel.getColumn(3)
+        templateColumn.cellEditor = PlaceholderCompletionCellEditor()
+
         val filenameTemplateTableScrollPane = JBScrollPane(filenameTemplateTable)
 
         panel.add(filenameTemplateTableScrollPane, BorderLayout.CENTER)

src/main/kotlin/de/idetools/filename_template/settings/PlaceholderCompletionCellEditor.kt

@@ -0,0 +1,68 @@
+package de.idetools.filename_template.settings
+
+import com.intellij.codeInsight.completion.CompletionResultSet
+import com.intellij.codeInsight.completion.InsertHandler
+import com.intellij.codeInsight.completion.InsertionContext
+import com.intellij.codeInsight.lookup.LookupElement
+import com.intellij.codeInsight.lookup.LookupElementBuilder
+import com.intellij.openapi.project.ProjectManager
+import com.intellij.util.TextFieldCompletionProviderDumbAware
+import com.intellij.util.textCompletion.TextFieldWithCompletion
+import java.awt.Component
+import javax.swing.AbstractCellEditor
+import javax.swing.JTable
+import javax.swing.table.TableCellEditor
+
+internal class PlaceholderCompletionCellEditor : AbstractCellEditor(), TableCellEditor {
+
+    private var component = TextFieldWithCompletion(
+        ProjectManager.getInstance().defaultProject,
+        PlaceholderCompletionProvider(),
+        "",
+        true,
+        true,
+        true
+    )
+
+    override fun getCellEditorValue(): Any {
+        return component.text
+    }
+
+    override fun getTableCellEditorComponent(
+        table: JTable,
+        value: Any,
+        isSelected: Boolean,
+        rowIndex: Int,
+        vColIndex: Int
+    ): Component {
+        component.text = value as String
+        return component
+    }
+
+    class PlaceholderCompletionProvider : TextFieldCompletionProviderDumbAware(true) {
+        object PlaceholderInsertHandler : InsertHandler<LookupElement> {
+            override fun handleInsert(context: InsertionContext, lookupElement: LookupElement) {
+                val text = context.document.text
+                if (context.tailOffset < text.length && text[context.tailOffset] == '}') {
+                    context.document.replaceString(context.tailOffset - 1, context.tailOffset + 1, "}")
+                }
+                if (0 < context.startOffset && text[context.startOffset - 1] == '{') {
+                    context.document.replaceString(context.startOffset - 1, context.startOffset + 1, "{")
+                }
+            }
+        }
+
+        override fun getPrefix(currentTextPrefix: String): String {
+            if (-1 < currentTextPrefix.indexOf('{')) {
+                return currentTextPrefix.removeRange(0, currentTextPrefix.lastIndexOf('{'))
+            }
+            return currentTextPrefix
+        }
+
+        override fun addCompletionVariants(text: String, offset: Int, prefix: String, result: CompletionResultSet) {
+            listOf("|", "0", "DATE", "EPOCH", "HOST", "PROJECT", "USER").forEach {
+                result.addElement(LookupElementBuilder.create("{${it}}").withInsertHandler(PlaceholderInsertHandler))
+            }
+        }
+    }
+}