1 files changed, 126 insertions, 0 deletions
diff --git a/src/utils/string-formatting.ts b/src/utils/string-formatting.ts
new file mode 100644
index 0000000..ff9f8bb
--- /dev/null
+++ b/src/utils/string-formatting.ts
@@ -0,0 +1,126 @@
+import type I18N from '@amp/web-apps-localization';
+import he from 'he';
+
+export function isString(string: unknown): string is string {
+    return typeof string === 'string';
+}
+
+export function concatWithMiddot(pieces: string[], i18n: I18N): string {
+    if (!pieces.length) {
+        return '';
+    }
+
+    return (
+        pieces.reduce((memo, current) => {
+            return i18n.t('ASE.Web.AppStore.ContentA.Middot.ContentB', {
+                contentA: memo,
+                contentB: current,
+            });
+        }) || ''
+    );
+}
+
+/**
+ * Truncates a block of text to fit within a character limit, with a bias towards ending on a
+ * full sentence. If no complete sentence fits within the limit, it falls back to a word-based
+ * truncation with an ellipsis.
+ *
+ * @param {string} text - The text to truncate.
+ * @param {number} limit - The maximum number of characters allowed before truncation.
+ * @param {string} [locale=en_US] - The locale to use when breaking the text into segments.
+ * @returns {string} Truncated text clipped to the limit, ideally ending on a natural stopping point.
+ */
+export function truncateAroundLimit(
+    text: string,
+    limit: number,
+    locale: string = 'en-US',
+): string {
+    // If the text is shorter than the limit, return all the text, unaltered.
+    if (text.length <= limit) {
+        return text;
+    }
+
+    const decodedText = he.decode(text);
+
+    const isSegemnterSupported = typeof Intl.Segmenter === 'function';
+    const terminatingPunctuation = '…';
+
+    // A very naive fallback if the browser doesn't support `Segementer`,
+    // which just truncates the text to the last space before the `limit`.
+    if (!isSegemnterSupported) {
+        const truncatedText = decodedText.slice(0, limit);
+        const indexOfLastSpace = truncatedText.lastIndexOf(' ');
+        if (indexOfLastSpace) {
+            return (
+                truncatedText.slice(0, indexOfLastSpace).trim() +
+                terminatingPunctuation
+            );
+        } else {
+            // If the text is an _exteremly_ long word or block of text, like a URL
+            return truncatedText.trim() + terminatingPunctuation;
+        }
+    }
+
+    const sentences = Array.from(
+        new Intl.Segmenter(locale, { granularity: 'sentence' }).segment(text),
+        (s) => s.segment,
+    );
+
+    let result = '';
+    for (const sentence of sentences) {
+        // If there is still room to add another sentence without going over the limit, add it.
+        if (result.length + sentence.length <= limit) {
+            result += sentence;
+        } else {
+            break;
+        }
+    }
+
+    result = result.trim();
+
+    // If the result we built based on full sentences is close-enough to the desired limit
+    // (e.g. within the threshold of 75% of 160), we can use it.
+    if (result.length >= limit * 0.75) {
+        return result;
+    }
+
+    // Otherwise, fallback to building up single words until we approach the limit.
+    const segments = Array.from(
+        new Intl.Segmenter(locale, { granularity: 'word' }).segment(
+            decodedText,
+        ),
+    );
+
+    result = '';
+    for (const { segment } of segments) {
+        if (result.length + segment.length <= limit) {
+            result += segment;
+        } else {
+            break;
+        }
+    }
+
+    return result.trim() + terminatingPunctuation;
+}
+
+export function escapeHtml(text: string): string {
+    return text
+        .replace(/&/g, '&amp;')
+        .replace(/</g, '&lt;')
+        .replace(/>/g, '&gt;');
+}
+
+export function commaSeparatedList(items: Array<string>, locale = 'en') {
+    return new Intl.ListFormat(locale, {
+        style: 'long',
+        type: 'conjunction',
+    }).format(items);
+}
+
+export function stripTags(text: string) {
+    return text.replace(/(<([^>]+)>)/gi, '');
+}
+
+export function stripUnicodeWhitespace(text: string) {
+    return text.replace(/[\u0000-\u001F]/g, '');
+}