Adding fomratting to mulitline autocomplete (#141)

It fixes [JetBrains: explore formatting multiline suggestions within
IntelliJ before rendering inlay
hint#72](#72)
## Test plan
* Trigger multiline autocompletion
* Change formatting style
* Trigger multiline autocompletion again and check if formatting is in
line with your settings


https://github.com/sourcegraph/jetbrains/assets/9321940/35ba1eea-7666-4474-aeaf-e953eccce8fc


<!-- All pull requests REQUIRE a test plan:
https://docs.sourcegraph.com/dev/background-information/testing_principles

Why does it matter? 

These test plans are there to demonstrate that are following industry
standards which are important or critical for our customers.
They might be read by customers or an auditor. There are meant be simple
and easy to read. Simply explain what you did to ensure
your changes are correct!

Here are a non exhaustive list of test plan examples to help you:

- Making changes on a given feature or component: 
- "Covered by existing tests" or "CI" for the shortest possible plan if
there is zero ambiguity
  - "Added new tests" 
- "Manually tested" (if non trivial, share some output, logs, or
screenshot)
- Updating docs: 
  - "previewed locally" 
  - share a screenshot if you want to be thorough
- Updating deps, that would typically fail immediately in CI if
incorrect
  - "CI" 
  - "locally tested" 
-->

README.md

@@ -187,6 +187,13 @@ You can configure the plugin on three levels:
 1. **Project-level** On the project level you are able to configure your default account, default branch name and remote url replacements
 2. **Application-level** All other settings are stored here
 
+## System Properties
+
+### Autocomplete system properties
+In order to disable newly introduced features we are giving an option to disable them via system properties:
+
+1. **Disable formatting autocomplete elements** `cody.autocomplete.enableFormatting=false`
+
 ## Managing Custom Keymaps
 
 ![A screenshot of the JetBrains preferences panel inside the Keymap tab](docs/keymaps.png)

build.gradle.kts

@@ -334,6 +334,9 @@ tasks {
     systemProperty("cody-agent.trace-path", "$buildDir/sourcegraph/cody-agent-trace.json")
     systemProperty("cody-agent.directory", buildCodyDir.parent)
     systemProperty("sourcegraph.verbose-logging", "true")
+    systemProperty(
+        "cody.autocomplete.enableFormatting",
+        project.property("cody.autocomplete.enableFormatting") ?: "true")
   }
 
   runPluginVerifier {

gradle.properties

@@ -23,4 +23,4 @@ gradleVersion=8.1.1
 # suppress inspection "UnusedProperty"
 kotlin.stdlib.default.dependency=false
 # See https://docs.gradle.org/current/userguide/build_cache.html#sec:build_cache_configure
-org.gradle.caching=true
+cody.autocomplete.enableFormatting=true

src/main/kotlin/com/sourcegraph/cody/autocomplete/CodyAutocompleteManager.kt

@@ -42,6 +42,7 @@ import com.sourcegraph.utils.CodyEditorUtil.getTextRange
 import com.sourcegraph.utils.CodyEditorUtil.isCommandExcluded
 import com.sourcegraph.utils.CodyEditorUtil.isEditorValidForAutocomplete
 import com.sourcegraph.utils.CodyEditorUtil.isImplicitAutocompleteEnabledForEditor
+import com.sourcegraph.utils.CodyFormatter
 import difflib.Delta
 import difflib.DiffUtils
 import difflib.Patch
@@ -322,7 +323,7 @@ class CodyAutocompleteManager {
       clearAutocompleteSuggestions(editor)
       currentAutocompleteTelemetry?.markCompletionDisplayed()
 
-      displayAgentAutocomplete(editor, offset, items, inlayModel, triggerKind, lookupString)
+      displayAgentAutocomplete(editor, offset, items, inlayModel, triggerKind)
     }
   }
 
@@ -338,8 +339,22 @@ class CodyAutocompleteManager {
       items: List<InlineAutocompleteItem>,
       inlayModel: InlayModel,
       triggerKind: InlineCompletionTriggerKind,
-      lookupString: String?,
   ) {
+    val project = editor.project
+    if (project != null && System.getProperty("cody.autocomplete.enableFormatting") != "false") {
+      items.map { item ->
+        if (item.insertText.lines().size > 1) {
+          item.insertText =
+              item.insertText.lines()[0] +
+                  CodyFormatter.formatStringBasedOnDocument(
+                      item.insertText.lines().drop(1).joinToString(separator = "\n"),
+                      project,
+                      editor.document,
+                      offset)
+        }
+      }
+    }
+
     val defaultItem = items.firstOrNull() ?: return
     val range = getTextRange(editor.document, defaultItem.range)
     val originalText = editor.document.getText(range)

src/main/kotlin/com/sourcegraph/cody/autocomplete/action/CycleCodyAutocompleteActionHandler.kt

@@ -44,12 +44,7 @@ class CycleCodyAutocompleteActionHandler(private val cycleDirection: CycleDirect
         CodyAutocompleteManager.instance.let {
           it.clearAutocompleteSuggestions(editor)
           it.displayAgentAutocomplete(
-              editor,
-              caret.offset,
-              newItems,
-              editor.inlayModel,
-              InlineCompletionTriggerKind.INVOKE,
-              null)
+              editor, caret.offset, newItems, editor.inlayModel, InlineCompletionTriggerKind.INVOKE)
         }
         autocompleteItemsCache[cacheKey] = newItems
       }

src/main/kotlin/com/sourcegraph/utils/CodyFormatter.kt

@@ -0,0 +1,47 @@
+package com.sourcegraph.utils
+
+import com.intellij.openapi.editor.Document
+import com.intellij.openapi.fileEditor.FileDocumentManager
+import com.intellij.openapi.project.Project
+import com.intellij.psi.PsiFileFactory
+import com.intellij.psi.codeStyle.CodeStyleManager
+import com.intellij.refactoring.suggested.endOffset
+
+class CodyFormatter {
+  companion object {
+    /**
+     * Formatting used to format inlay text inserted by Cody, based on the surrounding code style in
+     * the document.
+     */
+    fun formatStringBasedOnDocument(
+        originalText: String,
+        project: Project,
+        document: Document,
+        offset: Int
+    ): String {
+
+      val appendedString =
+          document.text.substring(0, offset) + originalText + document.text.substring(offset)
+
+      val file = FileDocumentManager.getInstance().getFile(document)!!
+      val psiFile =
+          PsiFileFactory.getInstance(project)
+              .createFileFromText("TEMP", file.fileType, appendedString)
+
+      val codeStyleManager = CodeStyleManager.getInstance(project)
+
+      var i = offset
+      var startRefactoringPosition = offset
+      while ((document.text.elementAt(i - 1) == ' ' ||
+          document.text.elementAt(i - 1) == '\n' ||
+          document.text.elementAt(i - 1) == '\t') && i > 0) {
+        startRefactoringPosition = i
+        i--
+      }
+      var endOffset = offset + psiFile.endOffset - document.textLength
+      codeStyleManager.reformatText(psiFile, startRefactoringPosition, endOffset)
+      endOffset = offset + psiFile.endOffset - document.textLength
+      return psiFile.text.substring(startRefactoringPosition, endOffset)
+    }
+  }
+}