✨ Initial implementation

Implements `queryTerminal` function based on my original script.
Includes a manual (self-run) test case.

Author: connorjs

README.md

@@ -2,6 +2,15 @@
 
 > Query for terminfo capabilities using XTGETTCAP
 
+## Usage
+
+```js
+import { queryTerminal } from "query-terminal";
+
+const answer = await queryTerminal(`<some capability>`);
+console.log(answer);
+```
+
 ## Context
 
 The [supports-hyperlink] issue about [Kitty support][kitty-support] led me to

package.json

@@ -19,6 +19,9 @@
     "url": "https://github.com/connorjs"
   },
   "main": "query-terminal.js",
+  "exports": {
+    ".": "./query-terminal.js"
+  },
   "type": "module",
   "repository": {
     "type": "git",

query-terminal.js

@@ -0,0 +1,76 @@
+// Some constants for clarity
+const ESC = `\x1B`;
+const DCS = `${ESC}P`;
+const ST = `${ESC}\\`;
+const ONE = `1`.charCodeAt(0);
+const EQUALS = `=`.charCodeAt(0);
+
+/**
+ * Returns the DCS query string (XTGETTCAP). Only supports a single query.
+ *
+ * > Request Termcap/Terminfo String (XTGETTCAP)
+ *
+ * @param query {string} - The query to make.
+ * @returns The encoded DCS query string
+ * @see <https://invisible-island.net/xterm/ctlseqs/ctlseqs.html>
+ */
+function dcsQuery(query) {
+	const hex = Buffer.from(query, 'utf8').toString('hex');
+	return `${DCS}+q${hex}${ST}`;
+}
+
+/**
+ * Returns the DCS answer (to the {@link dcsQuery}). (The part after the `=`.)
+ *
+ * > DCS 1 + r Pt ST for valid requests, adding to Pt an = , and
+ * > the value of the corresponding string that xterm would send,
+ * > or
+ * > DCS 0 + r ST for invalid requests.
+ *
+ * @param response {Buffer} - The encoded DCS response.
+ * @returns The answer for valid requests and `undefined` for invalid requests
+ * @see <https://invisible-island.net/xterm/ctlseqs/ctlseqs.html>
+ */
+function dcsAnswer(response) {
+	const success = response[2];
+	if (success !== ONE) {
+		return undefined; // Invalid request
+	}
+
+	const index = response.lastIndexOf(EQUALS);
+	if (index < 0) {
+		return undefined; // No `=` found, so invalid format
+	}
+
+	const answer = response.subarray(index + 1, -1);
+	// Answer is an ASCII (UTF-8) string of Hex characters
+	return Buffer.from(answer.toString(), 'hex').toString();
+}
+
+/**
+ * Query the terminal for Termcap/Terminfo capabilities (XTGETTCAP).
+ *
+ * @param query {string} - The requested capability.
+ * @returns The answer for valid requests and `undefined` for invalid requests
+ */
+export async function queryTerminal(query) {
+	return new Promise(function (resolve, reject) {
+		try {
+			// Configure stdin to watch for the response
+			/** @type {import('node:stream').Readable} */
+			const stdin = process.stdin;
+			stdin.setRawMode(true);
+			stdin.resume(); // Listen
+			stdin.on('data', (data) => {
+				stdin.pause(); // Stop listening
+				resolve(dcsAnswer(data));
+			});
+
+			// XTGETTCAP means writing the DCS query to the terminal
+			process.stdout.write(dcsQuery(query));
+
+		} catch (error) {
+			reject(error);
+		}
+	});
+}

test/kitty-allow-hyperlinks.js

@@ -0,0 +1,7 @@
+import { queryTerminal } from "query-terminal";
+
+// Query for hyperlink specifically
+// https://sw.kovidgoyal.net/kitty/kittens/query_terminal/
+// https://github.com/kovidgoyal/kitty/blob/master/kittens/query_terminal/main.py
+const answer = await queryTerminal(`kitty-query-allow_hyperlinks`);
+console.log(answer);