implement transpose letters command

lib/ace/commands/default_commands.js

@@ -256,5 +256,9 @@ canon.addCommand({
         env.editor.insert(lang.stringRepeat(args.text  || "", args.times || 1));
     }
 });
+canon.addCommand({
+    name: "transposeletters",
+    exec: function(env, args, request) { env.editor.transposeLetters(); }
+});
 
 });

lib/ace/editor.js

@@ -565,6 +565,34 @@ var Editor =function(renderer, session) {
         this.clearSelection();
     };
 
+    
+    this.transposeLetters = function() {
+        if (this.$readOnly)
+            return;
+        
+        if (!this.selection.isEmpty()) {
+            //this.session.remove(this.getSelectionRange());
+            //this.clearSelection();
+            return;
+        }
+    
+        var cursor = this.getCursorPosition();
+        var column = cursor.column;
+        if (column == 0)
+            return;
+        
+        var line = this.session.getLine(cursor.row);
+        if (column < line.length) {
+            var swap = line.charAt(column) + line.charAt(column-1);
+            var range = new Range(cursor.row, column-1, cursor.row, column+1)
+        }
+        else {
+            var swap = line.charAt(column-1) + line.charAt(column-2);
+            var range = new Range(cursor.row, column-2, cursor.row, column)
+        }
+        this.session.replace(range, swap);
+    };
+    
     this.indent = function() {
         if (this.$readOnly)
             return;

lib/ace/test/text_edit_test.js

@@ -434,6 +434,56 @@ var Test = {
         editor.moveCursorTo(1, 8);
         editor.removeLeft();
         assert.equal(session.toString(), "123\n    456");
+    },
+    
+    "test: transpose at line start should be a noop": function() {
+        var session = new EditSession(["123", "4567", "89"]);
+        
+        var editor = new Editor(new MockRenderer(), session);
+        editor.moveCursorTo(1, 0);
+        editor.transposeLetters();
+        
+        assert.equal(session.getValue(), ["123", "4567", "89"].join("\n"));
+    },
+    
+    "test: transpose in line should swap the charaters before and after the cursor": function() {
+        var session = new EditSession(["123", "4567", "89"]);
+        
+        var editor = new Editor(new MockRenderer(), session);
+        editor.moveCursorTo(1, 2);
+        editor.transposeLetters();
+        
+        assert.equal(session.getValue(), ["123", "4657", "89"].join("\n"));
+    },
+    
+    "test: transpose at line end should swap the last two characters": function() {
+        var session = new EditSession(["123", "4567", "89"]);
+        
+        var editor = new Editor(new MockRenderer(), session);
+        editor.moveCursorTo(1, 4);
+        editor.transposeLetters();
+        
+        assert.equal(session.getValue(), ["123", "4576", "89"].join("\n"));
+    },
+    
+    "test: transpose with non empty selection should be a noop": function() {
+        var session = new EditSession(["123", "4567", "89"]);
+        
+        var editor = new Editor(new MockRenderer(), session);
+        editor.moveCursorTo(1, 1);
+        editor.getSelection().selectRight();
+        editor.transposeLetters();
+        
+        assert.equal(session.getValue(), ["123", "4567", "89"].join("\n"));
+    },
+    
+    "test: transpose should move the cursor behind the last swapped character": function() {
+        var session = new EditSession(["123", "4567", "89"]);
+        
+        var editor = new Editor(new MockRenderer(), session);
+        editor.moveCursorTo(1, 2);
+        editor.transposeLetters();
+        assert.position(editor.getCursorPosition(), 1, 3);        
     }
 };