support incrementing/decrementing doc positions with predicate

test/editor/position-test.js

@@ -0,0 +1,80 @@
+/*
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import expect from 'expect';
+import EditorModel from "../../src/editor/model";
+import {createPartCreator} from "./mock";
+
+function createRenderer() {
+    const render = (c) => {
+        render.caret = c;
+        render.count += 1;
+    };
+    render.count = 0;
+    render.caret = null;
+    return render;
+}
+
+describe('editor/position', function() {
+    it('move first position backward in empty model', function() {
+        const model = new EditorModel([], createPartCreator(), createRenderer());
+        const pos = model.positionForOffset(0, true);
+        const pos2 = pos.backwardsWhile(model, () => true);
+        expect(pos).toBe(pos2);
+    });
+    it('move first position forwards in empty model', function() {
+        const model = new EditorModel([], createPartCreator(), createRenderer());
+        const pos = model.positionForOffset(0, true);
+        const pos2 = pos.forwardsWhile(() => true);
+        expect(pos).toBe(pos2);
+    });
+    it('move forwards within one part', function() {
+        const pc = createPartCreator();
+        const model = new EditorModel([pc.plain("hello")], pc, createRenderer());
+        const pos = model.positionForOffset(1);
+        let n = 3;
+        const pos2 = pos.forwardsWhile(model, () => { n -= 1; return n >= 0; });
+        expect(pos2.index).toBe(0);
+        expect(pos2.offset).toBe(4);
+    });
+    it('move forwards crossing to other part', function() {
+        const pc = createPartCreator();
+        const model = new EditorModel([pc.plain("hello"), pc.plain(" world")], pc, createRenderer());
+        const pos = model.positionForOffset(4);
+        let n = 3;
+        const pos2 = pos.forwardsWhile(model, () => { n -= 1; return n >= 0; });
+        expect(pos2.index).toBe(1);
+        expect(pos2.offset).toBe(2);
+    });
+    it('move backwards within one part', function() {
+        const pc = createPartCreator();
+        const model = new EditorModel([pc.plain("hello")], pc, createRenderer());
+        const pos = model.positionForOffset(4);
+        let n = 3;
+        const pos2 = pos.backwardsWhile(model, () => { n -= 1; return n >= 0; });
+        expect(pos2.index).toBe(0);
+        expect(pos2.offset).toBe(1);
+    });
+    it('move backwards crossing to other part', function() {
+        const pc = createPartCreator();
+        const model = new EditorModel([pc.plain("hello"), pc.plain(" world")], pc, createRenderer());
+        const pos = model.positionForOffset(7);
+        let n = 3;
+        const pos2 = pos.backwardsWhile(model, () => { n -= 1; return n >= 0; });
+        expect(pos2.index).toBe(0);
+        expect(pos2.offset).toBe(4);
+    });
+});