readline: move utilities to internal modules

PR-URL: #38466
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

lib/internal/console/constructor.js

@@ -429,7 +429,10 @@ const consoleMethods = {
     if (this._stdout.isTTY && process.env.TERM !== 'dumb') {
       // The require is here intentionally to avoid readline being
       // required too early when console is first loaded.
-      const { cursorTo, clearScreenDown } = require('readline');
+      const {
+        cursorTo,
+        clearScreenDown,
+      } = require('internal/readline/callbacks');
       cursorTo(this._stdout, 0, 0);
       clearScreenDown(this._stdout);
     }

lib/internal/readline/callbacks.js

@@ -0,0 +1,132 @@
+'use strict';
+
+const {
+  NumberIsNaN,
+} = primordials;
+
+const {
+  codes: {
+    ERR_INVALID_ARG_VALUE,
+    ERR_INVALID_CURSOR_POS,
+  },
+} = require('internal/errors');
+
+const {
+  validateCallback,
+} = require('internal/validators');
+const {
+  CSI,
+} = require('internal/readline/utils');
+
+const {
+  kClearLine,
+  kClearScreenDown,
+  kClearToLineBeginning,
+  kClearToLineEnd,
+} = CSI;
+
+
+/**
+ * moves the cursor to the x and y coordinate on the given stream
+ */
+
+function cursorTo(stream, x, y, callback) {
+  if (callback !== undefined) {
+    validateCallback(callback);
+  }
+
+  if (typeof y === 'function') {
+    callback = y;
+    y = undefined;
+  }
+
+  if (NumberIsNaN(x)) throw new ERR_INVALID_ARG_VALUE('x', x);
+  if (NumberIsNaN(y)) throw new ERR_INVALID_ARG_VALUE('y', y);
+
+  if (stream == null || (typeof x !== 'number' && typeof y !== 'number')) {
+    if (typeof callback === 'function') process.nextTick(callback, null);
+    return true;
+  }
+
+  if (typeof x !== 'number') throw new ERR_INVALID_CURSOR_POS();
+
+  const data = typeof y !== 'number' ? CSI`${x + 1}G` : CSI`${y + 1};${x + 1}H`;
+  return stream.write(data, callback);
+}
+
+/**
+ * moves the cursor relative to its current location
+ */
+
+function moveCursor(stream, dx, dy, callback) {
+  if (callback !== undefined) {
+    validateCallback(callback);
+  }
+
+  if (stream == null || !(dx || dy)) {
+    if (typeof callback === 'function') process.nextTick(callback, null);
+    return true;
+  }
+
+  let data = '';
+
+  if (dx < 0) {
+    data += CSI`${-dx}D`;
+  } else if (dx > 0) {
+    data += CSI`${dx}C`;
+  }
+
+  if (dy < 0) {
+    data += CSI`${-dy}A`;
+  } else if (dy > 0) {
+    data += CSI`${dy}B`;
+  }
+
+  return stream.write(data, callback);
+}
+
+/**
+ * clears the current line the cursor is on:
+ *   -1 for left of the cursor
+ *   +1 for right of the cursor
+ *    0 for the entire line
+ */
+
+function clearLine(stream, dir, callback) {
+  if (callback !== undefined) {
+    validateCallback(callback);
+  }
+
+  if (stream === null || stream === undefined) {
+    if (typeof callback === 'function') process.nextTick(callback, null);
+    return true;
+  }
+
+  const type =
+    dir < 0 ? kClearToLineBeginning : dir > 0 ? kClearToLineEnd : kClearLine;
+  return stream.write(type, callback);
+}
+
+/**
+ * clears the screen from the current position of the cursor down
+ */
+
+function clearScreenDown(stream, callback) {
+  if (callback !== undefined) {
+    validateCallback(callback);
+  }
+
+  if (stream === null || stream === undefined) {
+    if (typeof callback === 'function') process.nextTick(callback, null);
+    return true;
+  }
+
+  return stream.write(kClearScreenDown, callback);
+}
+
+module.exports = {
+  clearLine,
+  clearScreenDown,
+  cursorTo,
+  moveCursor,
+};

lib/internal/readline/emitKeypressEvents.js

@@ -0,0 +1,96 @@
+'use strict';
+
+const {
+  SafeStringIterator,
+  Symbol,
+} = primordials;
+
+const {
+  charLengthAt,
+  CSI,
+  emitKeys,
+} = require('internal/readline/utils');
+
+const { clearTimeout, setTimeout } = require('timers');
+const {
+  kEscape,
+} = CSI;
+
+const { StringDecoder } = require('string_decoder');
+
+const KEYPRESS_DECODER = Symbol('keypress-decoder');
+const ESCAPE_DECODER = Symbol('escape-decoder');
+
+// GNU readline library - keyseq-timeout is 500ms (default)
+const ESCAPE_CODE_TIMEOUT = 500;
+
+/**
+ * accepts a readable Stream instance and makes it emit "keypress" events
+ */
+
+function emitKeypressEvents(stream, iface = {}) {
+  if (stream[KEYPRESS_DECODER]) return;
+
+  stream[KEYPRESS_DECODER] = new StringDecoder('utf8');
+
+  stream[ESCAPE_DECODER] = emitKeys(stream);
+  stream[ESCAPE_DECODER].next();
+
+  const triggerEscape = () => stream[ESCAPE_DECODER].next('');
+  const { escapeCodeTimeout = ESCAPE_CODE_TIMEOUT } = iface;
+  let timeoutId;
+
+  function onData(input) {
+    if (stream.listenerCount('keypress') > 0) {
+      const string = stream[KEYPRESS_DECODER].write(input);
+      if (string) {
+        clearTimeout(timeoutId);
+
+        // This supports characters of length 2.
+        iface._sawKeyPress = charLengthAt(string, 0) === string.length;
+        iface.isCompletionEnabled = false;
+
+        let length = 0;
+        for (const character of new SafeStringIterator(string)) {
+          length += character.length;
+          if (length === string.length) {
+            iface.isCompletionEnabled = true;
+          }
+
+          try {
+            stream[ESCAPE_DECODER].next(character);
+            // Escape letter at the tail position
+            if (length === string.length && character === kEscape) {
+              timeoutId = setTimeout(triggerEscape, escapeCodeTimeout);
+            }
+          } catch (err) {
+            // If the generator throws (it could happen in the `keypress`
+            // event), we need to restart it.
+            stream[ESCAPE_DECODER] = emitKeys(stream);
+            stream[ESCAPE_DECODER].next();
+            throw err;
+          }
+        }
+      }
+    } else {
+      // Nobody's watching anyway
+      stream.removeListener('data', onData);
+      stream.on('newListener', onNewListener);
+    }
+  }
+
+  function onNewListener(event) {
+    if (event === 'keypress') {
+      stream.on('data', onData);
+      stream.removeListener('newListener', onNewListener);
+    }
+  }
+
+  if (stream.listenerCount('keypress') > 0) {
+    stream.on('data', onData);
+  } else {
+    stream.on('newListener', onNewListener);
+  }
+}
+
+module.exports = emitKeypressEvents;

lib/internal/repl/utils.js

@@ -41,7 +41,7 @@ const {
   clearScreenDown,
   cursorTo,
   moveCursor,
-} = require('readline');
+} = require('internal/readline/callbacks');
 
 const {
   commonPrefix,