readline: move escape codes into internal/readline

Moves escape codes into internal/readline for easier management.

lib/internal/readline.js

@@ -7,9 +7,27 @@
 const ansi =
   /[\u001b\u009b][[()#;?]*(?:[0-9]{1,4}(?:;[0-9]{0,4})*)?[0-9A-ORZcf-nqry=><]/g;
 
+const kEscape = '\x1b';
+
 var getStringWidth;
 var isFullWidthCodePoint;
 
+function CSI(strings, ...args) {
+  let ret = `${kEscape}[`;
+  for (var n = 0; n < strings.length; n++) {
+    ret += strings[n];
+    if (n < args.length)
+      ret += args[n];
+  }
+  return ret;
+}
+
+CSI.kEscape = kEscape;
+CSI.kClearToBeginning = CSI`1K`;
+CSI.kClearToEnd = CSI`0K`;
+CSI.kClearLine = CSI`2K`;
+CSI.kClearScreenDown = CSI`0J`;
+
 if (process.binding('config').hasIntl) {
   const icu = process.binding('icu');
   getStringWidth = function getStringWidth(str, options) {
@@ -151,11 +169,11 @@ function* emitKeys(stream) {
       shift: false
     };
 
-    if (ch === '\x1b') {
+    if (ch === kEscape) {
       escaped = true;
       s += (ch = yield);
 
-      if (ch === '\x1b') {
+      if (ch === kEscape) {
         s += (ch = yield);
       }
     }
@@ -370,7 +388,7 @@ function* emitKeys(stream) {
       // backspace or ctrl+h
       key.name = 'backspace';
       key.meta = escaped;
-    } else if (ch === '\x1b') {
+    } else if (ch === kEscape) {
       // escape key
       key.name = 'escape';
       key.meta = escaped;
@@ -409,5 +427,6 @@ module.exports = {
   emitKeys,
   getStringWidth,
   isFullWidthCodePoint,
-  stripVTControlCharacters
+  stripVTControlCharacters,
+  CSI
 };

lib/readline.js

@@ -31,12 +31,21 @@ const { debug, inherits } = require('util');
 const Buffer = require('buffer').Buffer;
 const EventEmitter = require('events');
 const {
+  CSI,
   emitKeys,
   getStringWidth,
   isFullWidthCodePoint,
   stripVTControlCharacters
 } = require('internal/readline');
 
+const {
+  kEscape,
+  kClearToBeginning,
+  kClearToEnd,
+  kClearLine,
+  kClearScreenDown
+} = CSI;
+
 const kHistorySize = 30;
 const kMincrlfDelay = 100;
 const kMaxcrlfDelay = 2000;
@@ -995,7 +1004,7 @@ function emitKeypressEvents(stream, iface) {
           try {
             stream[ESCAPE_DECODER].next(r[i]);
             // Escape letter at the tail position
-            if (r[i] === '\x1b' && i + 1 === r.length) {
+            if (r[i] === kEscape && i + 1 === r.length) {
               timeoutId = setTimeout(escapeCodeTimeout, ESCAPE_CODE_TIMEOUT);
             }
           } catch (err) {
@@ -1047,9 +1056,9 @@ function cursorTo(stream, x, y) {
     throw new Error('Can\'t set cursor row without also setting it\'s column');
 
   if (typeof y !== 'number') {
-    stream.write('\x1b[' + (x + 1) + 'G');
+    stream.write(CSI`${x + 1}G`);
   } else {
-    stream.write('\x1b[' + (y + 1) + ';' + (x + 1) + 'H');
+    stream.write(CSI`${y + 1};${x + 1}H`);
   }
 }
 
@@ -1062,15 +1071,15 @@ function moveCursor(stream, dx, dy) {
     return;
 
   if (dx < 0) {
-    stream.write('\x1b[' + (-dx) + 'D');
+    stream.write(CSI`${-dx}D`);
   } else if (dx > 0) {
-    stream.write('\x1b[' + dx + 'C');
+    stream.write(CSI`${dx}C`);
   }
 
   if (dy < 0) {
-    stream.write('\x1b[' + (-dy) + 'A');
+    stream.write(CSI`${-dy}A`);
   } else if (dy > 0) {
-    stream.write('\x1b[' + dy + 'B');
+    stream.write(CSI`${dy}B`);
   }
 }
 
@@ -1087,13 +1096,13 @@ function clearLine(stream, dir) {
 
   if (dir < 0) {
     // to the beginning
-    stream.write('\x1b[1K');
+    stream.write(kClearToBeginning);
   } else if (dir > 0) {
     // to the end
-    stream.write('\x1b[0K');
+    stream.write(kClearToEnd);
   } else {
     // entire line
-    stream.write('\x1b[2K');
+    stream.write(kClearLine);
   }
 }
 
@@ -1105,7 +1114,7 @@ function clearScreenDown(stream) {
   if (stream === null || stream === undefined)
     return;
 
-  stream.write('\x1b[0J');
+  stream.write(kClearScreenDown);
 }
 
 module.exports = {