do not spit url between Read More chunks by expanding chunk to end of url

ts/test-both/util/graphemeAndLinkAwareSlice.ts

@@ -0,0 +1,70 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import { graphemeAndLinkAwareSlice } from '../../util/graphemeAndLinkAwareSlice';
+
+describe('graphemeAndLinkAwareSlice', () => {
+  it('returns entire string when shorter than maximum', () => {
+    const shortString = 'Hello, Signal!';
+    const result = graphemeAndLinkAwareSlice(shortString, 50);
+
+    assert.strictEqual(result.text, shortString);
+    assert.isFalse(result.hasReadMore);
+  });
+
+  it('should return string longer than max but within buffer', () => {
+    const input = 'Hello, Signal!';
+    const result = graphemeAndLinkAwareSlice(input, 5, 10);
+
+    assert.strictEqual(result.text, input);
+    assert.isFalse(result.hasReadMore);
+  });
+
+  it('should include entire url and detect no more to read', () => {
+    const input = 'Hello, Signal! https://signal.org';
+    const result = graphemeAndLinkAwareSlice(input, 16, 0);
+
+    assert.strictEqual(result.text, input);
+    assert.isFalse(result.hasReadMore);
+  });
+
+  it('should include entire url and detect more to read', () => {
+    const input = 'Hello, Signal! https://signal.org additional text';
+    const inputProperlyTruncated = 'Hello, Signal! https://signal.org';
+
+    const result = graphemeAndLinkAwareSlice(input, 16, 0);
+    assert.strictEqual(result.text, inputProperlyTruncated);
+    assert.isTrue(result.hasReadMore);
+  });
+
+  it('should truncate normally when url present after truncation', () => {
+    const input = 'Hello, Signal! https://signal.org additional text';
+    const inputProperlyTruncated = 'Hello, Signal!';
+
+    const result = graphemeAndLinkAwareSlice(input, 14, 0);
+    assert.strictEqual(result.text, inputProperlyTruncated);
+    assert.isTrue(result.hasReadMore);
+  });
+
+  it('truncates after url when url present before and at truncation point', () => {
+    const input =
+      'Hello, Signal! https://signal.org additional text https://example.com/example more text';
+    const inputProperlyTruncated =
+      'Hello, Signal! https://signal.org additional text https://example.com/example';
+
+    const result = graphemeAndLinkAwareSlice(input, 55, 0);
+    assert.strictEqual(result.text, inputProperlyTruncated);
+    assert.isTrue(result.hasReadMore);
+  });
+
+  it('truncates after url when url present at and after truncation point', () => {
+    const input =
+      'Hello, Signal! https://signal.org additional text https://example.com/example more text';
+    const inputProperlyTruncated = 'Hello, Signal! https://signal.org';
+
+    const result = graphemeAndLinkAwareSlice(input, 26, 0);
+    assert.strictEqual(result.text, inputProperlyTruncated);
+    assert.isTrue(result.hasReadMore);
+  });
+});