add support for selecting ranges in the editor model, and replacing them

this to support finding emoticons and replacing them with an emoji

test/editor/range-test.js

@@ -0,0 +1,88 @@
+/*
+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;
+}
+
+const pillChannel = "#riot-dev:matrix.org";
+
+describe('editor/range', function() {
+    it('range on empty model', function() {
+        const renderer = createRenderer();
+        const pc = createPartCreator();
+        const model = new EditorModel([], pc, renderer);
+        const range = model.startRange(model.positionForOffset(0, true));  // after "world"
+        let called = false;
+        range.expandBackwardsWhile(chr => {
+            called = true;
+            return true;
+        });
+        expect(called).toBe(false);
+        expect(range.text).toBe("");
+    });
+    it('range replace within a part', function() {
+        const renderer = createRenderer();
+        const pc = createPartCreator();
+        const model = new EditorModel([pc.plain("hello world!!!!")], pc, renderer);
+        const range = model.startRange(model.positionForOffset(11));  // after "world"
+        range.expandBackwardsWhile((index, offset) => model.parts[index].text[offset] !== " ");
+        expect(range.text).toBe("world");
+        range.replace([pc.roomPill(pillChannel)]);
+        console.log({parts: JSON.stringify(model.serializeParts())});
+        expect(model.parts[0].type).toBe("plain");
+        expect(model.parts[0].text).toBe("hello ");
+        expect(model.parts[1].type).toBe("room-pill");
+        expect(model.parts[1].text).toBe(pillChannel);
+        expect(model.parts[2].type).toBe("plain");
+        expect(model.parts[2].text).toBe("!!!!");
+        expect(model.parts.length).toBe(3);
+        expect(renderer.count).toBe(1);
+    });
+    it('range replace across parts', function() {
+        const renderer = createRenderer();
+        const pc = createPartCreator();
+        const model = new EditorModel([
+            pc.plain("try to re"),
+            pc.plain("pla"),
+            pc.plain("ce "),
+            pc.plain("me"),
+        ], pc, renderer);
+        const range = model.startRange(model.positionForOffset(14));  // after "replace"
+        range.expandBackwardsWhile((index, offset) => model.parts[index].text[offset] !== " ");
+        expect(range.text).toBe("replace");
+        console.log("range.text", {text: range.text});
+        range.replace([pc.roomPill(pillChannel)]);
+        expect(model.parts[0].type).toBe("plain");
+        expect(model.parts[0].text).toBe("try to ");
+        expect(model.parts[1].type).toBe("room-pill");
+        expect(model.parts[1].text).toBe(pillChannel);
+        expect(model.parts[2].type).toBe("plain");
+        expect(model.parts[2].text).toBe(" me");
+        expect(model.parts.length).toBe(3);
+        expect(renderer.count).toBe(1);
+    });
+});