add delta invert and tests, closes #28

src/Delta.ts

@@ -367,15 +367,24 @@ class Delta {
       } else if (op.retain && op.attributes == null) {
         inverted.retain(op.retain);
         return baseIndex + op.retain;
-      } else if (op.delete) {
-        base
-          .slice(baseIndex, baseIndex + op.delete)
-          .forEach(o => inverted.push(o));
-        return baseIndex + op.delete;
+      } else if (op.delete || (op.retain && op.attributes)) {
+        const length = (op.delete || op.retain) as number;
+        const slice = base.slice(baseIndex, baseIndex + length);
+        slice.forEach(baseOp => {
+          if (op.delete) {
+            inverted.push(baseOp);
+          } else if (op.retain && op.attributes) {
+            inverted.retain(
+              op.retain,
+              AttributeMap.invert(op.attributes, baseOp.attributes),
+            );
+          }
+        });
+        return baseIndex + length;
       }
       return baseIndex;
     }, 0);
-    return inverted;
+    return inverted.chop();
   }
 
   transform(index: number, priority?: boolean): number;

test/delta/invert.js

@@ -0,0 +1,55 @@
+var Delta = require('../../dist/Delta');
+
+describe('invert()', function() {
+  it('insert', function() {
+    var delta = new Delta().retain(2).insert('A');
+    var base = new Delta().insert('123456');
+    var expected = new Delta().retain(2).delete(1);
+    var inverted = delta.invert(base);
+    expect(expected).toEqual(inverted);
+    expect(base.compose(delta).compose(inverted)).toEqual(base);
+  });
+
+  it('delete', function() {
+    var delta = new Delta().retain(2).delete(3);
+    var base = new Delta().insert('123456');
+    var expected = new Delta().retain(2).insert('345');
+    var inverted = delta.invert(base);
+    expect(expected).toEqual(inverted);
+    expect(base.compose(delta).compose(inverted)).toEqual(base);
+  });
+
+  it('retain', function() {
+    var delta = new Delta().retain(2).retain(3, { bold: true });
+    var base = new Delta().insert('123456');
+    var expected = new Delta().retain(2).retain(3, { bold: null });
+    var inverted = delta.invert(base);
+    expect(expected).toEqual(inverted);
+    expect(base.compose(delta).compose(inverted)).toEqual(base);
+  });
+
+  it('combined', function() {
+    var delta = new Delta()
+      .retain(2)
+      .delete(2)
+      .insert('AB', { italic: true })
+      .retain(2, { italic: null, bold: true })
+      .retain(2, { color: 'red' })
+      .delete(1);
+    var base = new Delta()
+      .insert('123', { bold: true })
+      .insert('456', { italic: true })
+      .insert('789', { color: 'red', bold: true });
+    var expected = new Delta()
+      .retain(2)
+      .insert('3', { bold: true })
+      .insert('4', { italic: true })
+      .delete(2)
+      .retain(2, { italic: true, bold: null })
+      .retain(2)
+      .insert('9', { color: 'red', bold: true });
+    var inverted = delta.invert(base);
+    expect(expected).toEqual(inverted);
+    expect(base.compose(delta).compose(inverted)).toEqual(base);
+  });
+});