feat(amazonq): implement TextDocumentService message handler

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/lsp/AmazonQLspService.kt

@@ -39,6 +39,7 @@ import software.aws.toolkits.core.utils.warn
 import software.aws.toolkits.jetbrains.isDeveloperMode
 import software.aws.toolkits.jetbrains.services.amazonq.lsp.encryption.JwtEncryptionManager
 import software.aws.toolkits.jetbrains.services.amazonq.lsp.model.createExtendedClientMetadata
+import software.aws.toolkits.jetbrains.services.amazonq.lsp.textdocument.TextDocumentServiceHandler
 import software.aws.toolkits.jetbrains.services.telemetry.ClientMetadata
 import java.io.IOException
 import java.io.OutputStreamWriter
@@ -86,7 +87,7 @@ internal class LSPProcessListener : ProcessListener {
 
 @Service(Service.Level.PROJECT)
 class AmazonQLspService(private val project: Project, private val cs: CoroutineScope) : Disposable {
-    private var instance: AmazonQServerInstance? = null
+    internal var instance: AmazonQServerInstance? = null
 
     init {
         cs.launch {
@@ -111,12 +112,12 @@ class AmazonQLspService(private val project: Project, private val cs: CoroutineS
     }
 }
 
-private class AmazonQServerInstance(private val project: Project, private val cs: CoroutineScope) : Disposable {
+internal class AmazonQServerInstance(private val project: Project, private val cs: CoroutineScope) : Disposable {
     private val encryptionManager = JwtEncryptionManager()
 
     private val launcher: Launcher<AmazonQLanguageServer>
 
-    private val languageServer: AmazonQLanguageServer
+    internal val languageServer: AmazonQLanguageServer
         get() = launcher.remoteProxy
 
     @Suppress("ForbiddenVoid")
@@ -235,6 +236,12 @@ private class AmazonQServerInstance(private val project: Project, private val cs
             }
             languageServer.initialized(InitializedParams())
         }
+
+        TextDocumentServiceHandler(
+            project,
+            languageServer,
+            this
+        )
     }
 
     override fun dispose() {

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/lsp/textdocument/TextDocumentServiceHandler.kt

@@ -0,0 +1,74 @@
+// Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package software.aws.toolkits.jetbrains.services.amazonq.lsp.textdocument
+
+import com.intellij.openapi.Disposable
+import com.intellij.openapi.fileEditor.FileEditorManager
+import com.intellij.openapi.fileEditor.FileEditorManagerListener
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.vfs.VirtualFile
+import org.eclipse.lsp4j.DidCloseTextDocumentParams
+import org.eclipse.lsp4j.DidOpenTextDocumentParams
+import org.eclipse.lsp4j.TextDocumentIdentifier
+import org.eclipse.lsp4j.TextDocumentItem
+import software.aws.toolkits.jetbrains.services.amazonq.lsp.AmazonQLanguageServer
+import software.aws.toolkits.jetbrains.services.amazonq.lsp.AmazonQLspService
+
+class TextDocumentServiceHandler(
+    private val project: Project,
+    private val languageServer: AmazonQLanguageServer,
+    private val serverInstance: Disposable,
+) : FileEditorManagerListener {
+
+    init {
+        subscribeToFileEditorEvents()
+    }
+
+    private fun subscribeToFileEditorEvents() {
+        project.messageBus.connect(serverInstance).subscribe(
+            FileEditorManagerListener.FILE_EDITOR_MANAGER,
+            this
+        )
+    }
+
+    fun executeIfRunning(project: Project, runnable: (AmazonQLanguageServer) ->  Unit) =
+        AmazonQLspService.getInstance(project).instance?.languageServer?.let { runnable(it)}
+
+    override fun fileOpened(
+        source: FileEditorManager,
+        file: VirtualFile
+    ) {
+        executeIfRunning(project) {
+            it.textDocumentService.didOpen(
+                DidOpenTextDocumentParams().apply {
+                    textDocument = TextDocumentItem().apply {
+                        uri = file.url
+                        text = file.inputStream.readAllBytes().decodeToString()
+                    }
+                }
+            )
+        }
+    }
+
+    override fun fileClosed(
+        source: FileEditorManager,
+        file: VirtualFile,
+    ) {
+        executeIfRunning(project) {
+            it.textDocumentService.didClose(
+                DidCloseTextDocumentParams().apply {
+                    textDocument = TextDocumentIdentifier().apply {
+                        uri = file.url
+                    }
+                }
+            )
+        }
+    }
+
+    private fun didChange() {
+    }
+
+    private fun didSave() {
+    }
+}