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src/autocomplete-input.js

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+'use strict';
+
+/**
+ * Slash-command autocomplete prompt.
+ *
+ * An `input`-style single-line prompt built on @inquirer/core. It behaves like
+ * a normal text input, but as soon as the buffer starts with "/" (and no
+ * arguments have been typed yet) it renders the matching slash commands as
+ * inline help below the prompt.
+ *
+ *   ↑ / ↓  move the highlight between matches
+ *   Tab    complete the highlighted command into the buffer
+ *   Enter  submit the buffer (like a normal input)
+ *
+ * The filter term is frozen while the menu is open, so completing a command
+ * with Tab does not collapse the list — repeated ↑/↓ + Tab still works.
+ */
+
+import chalk from 'chalk';
+import {
+    createPrompt,
+    useState,
+    useKeypress,
+    usePrefix,
+    isEnterKey,
+    isTabKey,
+    isUpKey,
+    isDownKey,
+    makeTheme,
+} from '@inquirer/core';
+
+import { filterCommands } from './slash-commands.js';
+
+const MAX_SUGGESTIONS = 6;
+
+/** Show the inline menu only while the first word is being typed (no space yet). */
+function termFrom(line) {
+    if (typeof line !== 'string' || !line.startsWith('/')) return null;
+    if (line.includes(' ')) return null;
+    return line.toLowerCase();
+}
+
+/**
+ * Replace readline's actual edit buffer, not just the visible terminal line.
+ * `rl.clearLine()` only erases terminal output; using it before `rl.write()`
+ * leaves the old buffer in place and turns a completion such as `/h` into
+ * `/h/help` internally.
+ */
+function replaceBuffer(rl, nextValue) {
+    rl.write(null, { ctrl: true, name: 'a' });
+    rl.write(null, { ctrl: true, name: 'k' });
+    rl.write(nextValue);
+}
+
+export const autocompleteInput = createPrompt((config, done) => {
+    const theme = makeTheme({}, config.theme);
+    const [status, setStatus] = useState('idle');
+    const [value, setValue] = useState('');
+    const [term, setTerm] = useState(null); // frozen filter term while the menu is open
+    const [active, setActive] = useState(0); // highlighted suggestion index
+
+    const prefix = usePrefix({ status, theme });
+    const suggestions = term === null ? [] : filterCommands(term).slice(0, MAX_SUGGESTIONS);
+    const count = suggestions.length;
+
+    useKeypress((key, rl) => {
+        if (status !== 'idle') return;
+
+        if (isEnterKey(key)) {
+            const answer = value || rl.line;
+            setValue(answer);
+            setStatus('done');
+            done(answer);
+            return;
+        }
+
+        // Move the highlight within the open menu. Arrow keys do not change
+        // readline's text buffer, so no line clearing or rewriting is needed.
+        if (count > 0 && (isUpKey(key) || isDownKey(key))) {
+            const delta = isUpKey(key) ? -1 : 1;
+            setActive((active + delta + count) % count);
+            return;
+        }
+
+        // Complete the highlighted command into both the displayed value and
+        // readline's real edit buffer.
+        if (isTabKey(key)) {
+            if (count === 0) return;
+            const pick = suggestions[active % count];
+            replaceBuffer(rl, pick.name);
+            setValue(pick.name);
+            return; // keep `term` frozen so the menu stays open
+        }
+
+        // Ordinary editing: mirror the readline buffer and refresh the menu.
+        const line = rl.line;
+        setValue(line);
+        setTerm(termFrom(line));
+        setActive(0);
+    });
+
+    const message = theme.style.message(config.message);
+    const formattedValue = status === 'done' ? theme.style.answer(value) : value;
+
+    const lines = suggestions.map((c, i) => {
+        const marker = i === active % count ? chalk.cyan('❯') : ' ';
+        return `  ${chalk.cyan(marker)} ${chalk.bold(c.name.padEnd(7))} ${chalk.dim(c.description)}`;
+    });
+    if (count > 1) {
+        lines.push(chalk.dim('    ↑/↓ choose · Tab complete'));
+    }
+
+    const header = [prefix, message, formattedValue].filter((v) => v !== undefined).join(' ');
+    return [header, lines.length ? lines.join('\n') : undefined];
+});
+
+export default autocompleteInput;