feat: support @ file autocomplete in ask editor

src/ui/autocomplete.ts

@@ -0,0 +1,49 @@
+import { accessSync, constants as fsConstants } from "node:fs";
+import { delimiter, join } from "node:path";
+import { CombinedAutocompleteProvider } from "@mariozechner/pi-tui";
+
+const FD_BINARY_NAMES =
+	process.platform === "win32"
+		? ["fd.exe", "fdfind.exe", "fd", "fdfind"]
+		: ["fd", "fdfind"];
+
+/**
+ * pi resolves fd internally for its main editor, but that resolver is not part of
+ * the public extension API. Custom editors therefore need to supply the fd path
+ * themselves when reusing CombinedAutocompleteProvider for `@` file mentions.
+ */
+export function createAskAutocompleteProvider(cwd: string) {
+	return new CombinedAutocompleteProvider(
+		[],
+		cwd,
+		findAutocompleteBinary(FD_BINARY_NAMES)
+	);
+}
+
+function findAutocompleteBinary(binaryNames: readonly string[]): string | null {
+	const pathValue = process.env.PATH;
+	if (!pathValue) {
+		return null;
+	}
+
+	const directories = pathValue.split(delimiter).filter(Boolean);
+	for (const binaryName of binaryNames) {
+		const executablePath = directories
+			.map((directory) => join(directory, binaryName))
+			.find(isExecutableFile);
+		if (executablePath) {
+			return executablePath;
+		}
+	}
+
+	return null;
+}
+
+function isExecutableFile(path: string): boolean {
+	try {
+		accessSync(path, fsConstants.X_OK);
+		return true;
+	} catch {
+		return false;
+	}
+}

src/ui/controller.ts

@@ -26,6 +26,7 @@ import {
 } from "../state/transitions.ts";
 import { isEditingView } from "../state/view.ts";
 import type { AskParams, AskResult, AskState } from "../types.ts";
+import { createAskAutocompleteProvider } from "./autocomplete.ts";
 import type { AskInputCommand } from "./input.ts";
 import { getInputCommand } from "./input.ts";
 import { renderAskScreen } from "./render.ts";
@@ -38,9 +39,9 @@ type Tui = CustomCallbackArgs[0];
 type Theme = CustomCallbackArgs[1];
 type Keybindings = CustomCallbackArgs[2];
 type Done = (result: AskResult) => void;
+type AskFlowParams = AskParams & Pick<ExtensionContext, "cwd">;
 
 interface AskFlowController {
-	cachedLines: string[] | undefined;
 	done: Done;
 	editor: Editor;
 	state: AskState;
@@ -54,7 +55,7 @@ export function runAskFlow(
 	params: AskParams
 ): Promise<AskResult> {
 	return ctx.ui.custom<AskResult>((...args) =>
-		createAskFlowController(args, params)
+		createAskFlowController(args, { ...params, cwd: ctx.cwd })
 	);
 }
 
@@ -65,12 +66,11 @@ function createAskFlowController(
 		Keybindings,
 		(result: AskResult) => void,
 	],
-	params: AskParams
+	params: AskFlowParams
 ) {
 	const controller: AskFlowController = {
-		cachedLines: undefined,
 		done,
-		editor: createEditor(tui, theme),
+		editor: createEditor(tui, theme, params.cwd),
 		state: createInitialState(params),
 		suppressAutoInputForSelection: false,
 		theme,
@@ -83,7 +83,7 @@ function createAskFlowController(
 	return {
 		render: (width: number) => renderController(controller, width),
 		invalidate() {
-			controller.cachedLines = undefined;
+			// The editor manages its own async autocomplete redraws.
 		},
 		handleInput(data: string) {
 			handleControllerInput(controller, data);
@@ -95,15 +95,12 @@ function renderController(
 	controller: AskFlowController,
 	width: number
 ): string[] {
-	if (!controller.cachedLines) {
-		controller.cachedLines = renderAskScreen({
-			editor: controller.editor,
-			state: controller.state,
-			theme: controller.theme,
-			width,
-		});
-	}
-	return controller.cachedLines;
+	return renderAskScreen({
+		editor: controller.editor,
+		state: controller.state,
+		theme: controller.theme,
+		width,
+	});
 }
 
 function handleControllerInput(controller: AskFlowController, data: string) {
@@ -268,7 +265,6 @@ function submitEditorValue(state: AskState, value: string): AskState {
 }
 
 function refresh(controller: AskFlowController) {
-	controller.cachedLines = undefined;
 	controller.tui.requestRender();
 }
 
@@ -331,8 +327,14 @@ function saveEditorAndMoveOption(
 	return moveOption(nextState, delta);
 }
 
-function createEditor(tui: Tui, theme: Theme) {
-	const editorTheme: EditorTheme = {
+function createEditor(tui: Tui, theme: Theme, cwd: string) {
+	const editor = new Editor(tui, createEditorTheme(theme));
+	editor.setAutocompleteProvider(createAskAutocompleteProvider(cwd));
+	return editor;
+}
+
+function createEditorTheme(theme: Theme): EditorTheme {
+	return {
 		borderColor: (text) => theme.fg("accent", text),
 		selectList: {
 			description: (text) => theme.fg("muted", text),
@@ -342,7 +344,6 @@ function createEditor(tui: Tui, theme: Theme) {
 			selectedText: (text) => theme.fg("accent", text),
 		},
 	};
-	return new Editor(tui, editorTheme);
 }
 
 function getEditorTextForCurrentView(state: AskState): string {

src/ui/render-helpers.ts

@@ -7,6 +7,11 @@ import { UI_DIMENSIONS, UI_TEXT } from "./constants.ts";
 type Theme = ExtensionContext["ui"]["theme"];
 type ThemeColor = "accent" | "muted" | "text" | "dim" | "success" | "warning";
 
+const EDITOR_BORDER_PATTERN = /^[┌┐└┘─]+$/;
+const EDITOR_SCROLL_BORDER_PATTERN = /^─── [↑↓] \d+ more ─*$/;
+const ANSI_CONTROL_SEQUENCE = "\u001b[";
+const ANSI_TERMINATOR = "m";
+
 export function pushWrappedText(
 	lines: string[],
 	text: string,
@@ -65,8 +70,7 @@ export function renderEditorBlock(args: {
 		placeholderColor = "muted",
 		isEmpty = false,
 	} = args;
-	const innerLines =
-		editorLines.length >= 2 ? editorLines.slice(1, -1) : editorLines;
+	const innerLines = getEditorContentLines(editorLines);
 
 	if (isEmpty && placeholder) {
 		lines.push(
@@ -93,6 +97,53 @@ export function renderEditorBlock(args: {
 	}
 }
 
+function getEditorContentLines(editorLines: string[]): string[] {
+	if (editorLines.length <= 2) {
+		return editorLines;
+	}
+
+	const contentLines = editorLines.slice(1);
+	const trailingBorderIndex = contentLines.findIndex(isEditorBorderLine);
+	if (trailingBorderIndex === -1) {
+		return contentLines;
+	}
+
+	return contentLines.filter((_, index) => index !== trailingBorderIndex);
+}
+
+function isEditorBorderLine(line: string): boolean {
+	const plainText = stripAnsiColorCodes(line).trim();
+	if (plainText.length === 0) {
+		return false;
+	}
+
+	return (
+		EDITOR_BORDER_PATTERN.test(plainText) ||
+		EDITOR_SCROLL_BORDER_PATTERN.test(plainText)
+	);
+}
+
+function stripAnsiColorCodes(text: string): string {
+	let result = text;
+	while (true) {
+		const start = result.indexOf(ANSI_CONTROL_SEQUENCE);
+		if (start === -1) {
+			return result;
+		}
+
+		const end = result.indexOf(
+			ANSI_TERMINATOR,
+			start + ANSI_CONTROL_SEQUENCE.length
+		);
+		if (end === -1) {
+			return result;
+		}
+
+		result =
+			result.slice(0, start) + result.slice(end + ANSI_TERMINATOR.length);
+	}
+}
+
 function renderEditorLine(
 	line: string,
 	availableWidth: number,