Fix: keep signature when inserting a template #621

lib/__tests__/template-utils.test.ts

@@ -10,6 +10,7 @@ import {
   filterTemplates,
   exportTemplates,
   importTemplates,
+  spliceTemplateAboveSignature,
 } from '../template-utils';
 import type { EmailTemplate } from '../template-types';
 
@@ -333,3 +334,39 @@ describe('filterTemplates', () => {
     expect(filterTemplates(templates, 'xyz')).toHaveLength(0);
   });
 });
+
+describe('spliceTemplateAboveSignature', () => {
+  const template = '<p>Template body</p>';
+
+  it('keeps the signature block below the template (separator marker)', () => {
+    const prev = '<p></p><p data-signature-block="separator">-- </p><div>My signature</div><p data-signature-block="end"></p>';
+    expect(spliceTemplateAboveSignature(prev, template)).toBe(
+      '<p>Template body</p><p data-signature-block="separator">-- </p><div>My signature</div><p data-signature-block="end"></p>'
+    );
+  });
+
+  it('keeps the signature block below the template (start marker, no separator)', () => {
+    const prev = '<p>old draft text</p><p data-signature-block="start"></p><div>My signature</div><p data-signature-block="end"></p>';
+    expect(spliceTemplateAboveSignature(prev, template)).toBe(
+      '<p>Template body</p><p data-signature-block="start"></p><div>My signature</div><p data-signature-block="end"></p>'
+    );
+  });
+
+  it('replaces the whole body when there is no signature block', () => {
+    expect(spliceTemplateAboveSignature('<p>old draft text</p>', template)).toBe(template);
+  });
+
+  it('keeps everything from the start marker onward when the end marker is missing', () => {
+    const prev = '<p>old</p><p data-signature-block="separator">-- </p><div>My signature</div>';
+    expect(spliceTemplateAboveSignature(prev, template)).toBe(
+      '<p>Template body</p><p data-signature-block="separator">-- </p><div>My signature</div>'
+    );
+  });
+
+  it('discards user edits above the signature', () => {
+    const prev = '<p>half-written draft</p><p data-signature-block="separator">-- </p><div>Sig</div><p data-signature-block="end"></p>';
+    const result = spliceTemplateAboveSignature(prev, template);
+    expect(result).not.toContain('half-written draft');
+    expect(result).toContain('Sig');
+  });
+});

lib/template-utils.ts

@@ -80,6 +80,26 @@ export function filterTemplates(templates: EmailTemplate[], query: string): Emai
   );
 }
 
+// Compose bodies carry the embedded signature bracketed by
+// data-signature-block markers (see email-composer's
+// buildEmbeddedSignatureHtml). Applying a template must replace only the
+// message content, so splice the template above the signature range instead
+// of overwriting the whole body.
+export function spliceTemplateAboveSignature(prevHtml: string, templateHtml: string): string {
+  const doc = new DOMParser().parseFromString(prevHtml, 'text/html');
+  const startEl = doc.querySelector('[data-signature-block="separator"], [data-signature-block="start"]');
+  if (!startEl) return templateHtml;
+  const endEl = doc.querySelector('[data-signature-block="end"]');
+  const host = doc.createElement('div');
+  let cursor: Node | null = startEl;
+  while (cursor) {
+    host.appendChild(cursor.cloneNode(true));
+    if (cursor === endEl) break;
+    cursor = cursor.nextSibling;
+  }
+  return templateHtml + host.innerHTML;
+}
+
 function sanitizeText(value: unknown): string {
   return DOMPurify.sanitize(String(value || ''), STRIP_HTML_CONFIG);
 }