repl completion: multi-column display of completions

lib/readline.js

@@ -41,7 +41,6 @@ function Interface (output, completer) {
     // Check process.env.TERM ?
     stdio.setRawMode(true);
     this._tty = true;
-    this.columns = stdio.getColumns();
 
     // Cursor position on the line.
     this.cursor = 0;
@@ -53,6 +52,11 @@ function Interface (output, completer) {
 
 inherits(Interface, EventEmitter);
 
+Interface.prototype.__defineGetter__("columns", function () {
+  if (this._tty) {
+    return stdio.getColumns();
+  }
+});
 
 Interface.prototype.setPrompt = function (prompt, length) {
   this._prompt = prompt;
@@ -156,14 +160,48 @@ Interface.prototype._tabComplete = function () {
       self._insertString(completions[0].slice(completeOn.length));
       self._refreshLine();
     } else {
-      //TODO: Multi-column display. Request to show if more than N completions.
-      self.output.write("\n");
-      completions.forEach(function (c) {
-        //TODO: try using '\r\n' instead of the following goop for getting to column 0
-        self.output.write('\x1b[0G');
-        self.output.write(c + "\n");
-      })
-      self.output.write('\n');
+      //TODO: If there is a common prefix to all matches (e.g. Python `sys.exi<Tab>`) then apply that portion
+      self.output.write("\r\n");
+      var width = completions.reduce(function(a, b) {
+        return a.length > b.length ? a : b;
+      }).length + 2;  // 2 space padding
+      var maxColumns = Math.floor(this.columns / width) || 1;
+
+      function handleGroup(group) {
+        if (group.length == 0) {
+          return;
+        }
+        var minRows = Math.ceil(group.length / maxColumns);
+        for (var row = 0; row < minRows; row++) {
+          for (var col = 0; col < maxColumns; col++) {
+            var idx = row * maxColumns + col;
+            if (idx >= group.length) {
+              break;
+            }
+            var item = group[idx];
+            self.output.write(item);
+            if (col < maxColumns - 1) {
+              for (var s = 0; s < width - item.length; s++) {
+                self.output.write(' ');
+              }
+            }
+          }
+          self.output.write('\r\n');
+        }
+        self.output.write('\r\n');
+      }
+
+      var group = [], c;
+      for (var i = 0; i < completions.length; i++) {
+        c = completions[i];
+        if (c === "") {
+          handleGroup(group);
+          group = [];
+        } else {
+          group.push(c);
+        }
+      }
+      handleGroup(group);
       self._refreshLine();
     }
   }