WIP Add extract function execute command

package.json

@@ -134,6 +134,11 @@
         "command": "lexical.server.restart",
         "category": "Lexical",
         "title": "Restart Lexical's language server"
+      },
+      {
+        "category": "Elixir",
+        "command": "extension.extractFunction",
+        "title": "Extract function"
       }
     ],
     "configurationDefaults": {
@@ -144,6 +149,15 @@
         "files.insertFinalNewline": true,
         "files.trimFinalNewlines": true
       }
+    },
+    "menus": {
+      "commandPalette": [
+        {
+          "category": "Elixir",
+          "command": "extension.extractFunction",
+          "when": "editorLangId == elixir"
+        }
+      ]
     }
   },
   "scripts": {

src/commands/extract-function.ts

@@ -0,0 +1,76 @@
+import {
+	commands,
+	extensions,
+	Range,
+	SnippetString,
+	window,
+} from "vscode";
+
+import {
+	ExecuteCommandParams,
+	LanguageClient,
+} from "vscode-languageclient/node";
+import Commands from ".";
+
+interface Context {
+	client: LanguageClient;
+	showWarning: (message: string) => void;
+}
+
+const extractFunction: Commands.T<Context> = {
+	id: "extension.extractFunction",
+	createHandler: ({ client, showWarning }) => {
+		async function handle() {
+			const extension = extensions.getExtension("lexical-lsp.lexical");
+			const editor = window.activeTextEditor;
+			if (!extension || !editor || !client) {
+				return;
+			}
+
+			const command =
+				client.initializeResult!.capabilities.executeCommandProvider!.commands.find(
+					(c: string) => c.startsWith("extractFunction")
+				)!;
+			if (!command) {
+				return;
+			}
+
+			const uriStr = editor.document.uri.toString();
+			const { start, end } = editor.selection;
+			const args = [uriStr, start.line, end.line, "extracted_function"];
+			const params: ExecuteCommandParams = { command, arguments: args };
+			await client.sendRequest("workspace/executeCommand", params);
+
+			const editor2 = window.activeTextEditor;
+			if (!editor2) {
+				return;
+			}
+			const document = editor2.document;
+			const text = document.getText();
+			const startIndex = text.indexOf("extracted_function");
+			const endIndex = text.lastIndexOf("extracted_function");
+
+			if (startIndex !== -1 && endIndex !== -1) {
+				const startPosition = document.positionAt(startIndex);
+				const endPosition = document.positionAt(
+					endIndex + "extracted_function".length
+				);
+				const range = new Range(startPosition, endPosition);
+				const toReplace = document.getText(range);
+				// Use snippet to allow user to input the new function name
+				const snippet = toReplace
+					.replace("extracted_function", "${1:function_extracted}$0")
+					.replace("extracted_function", "${1:function_extracted}")
+					.replace(/function_extracted/g, "extracted_function")
+					.replace(/^ +/gm, "");
+				editor2.insertSnippet(new SnippetString(snippet), range);
+				// insertSnippet breaks whitspace formatting, so we run format cmd:
+				commands.executeCommand("editor.action.formatDocument");
+			}
+		}
+
+		return handle;
+	},
+};
+
+export default extractFunction;

src/extension.ts

@@ -11,6 +11,7 @@ import {
 import { join } from "path";
 import * as fs from "fs";
 import Commands from "./commands";
+import extractFunction from "./commands/extract-function";
 import restartServer from "./commands/restart-server";
 import { URI } from "vscode-uri";
 import Logger from "./logger";
@@ -28,9 +29,15 @@ export async function activate(context: ExtensionContext): Promise<void> {
 			context.subscriptions.push(commands.registerCommand(id, handler));
 		});
 
-		registerCommand(restartServer, {
-			client,
-		});
+		if (client !== undefined) {
+			registerCommand(extractFunction, {
+				client,
+				showWarning: window.showWarningMessage,
+			});
+			registerCommand(restartServer, {
+				client,
+			});
+		}
 	}
 }