Add HTML5 authoring diff preview

services/api-server/src/api_server/html5.py

@@ -371,6 +371,25 @@ def render_html5_authoring_preview(project_id: str, preview: object | None, erro
             <button type="submit">Preview</button>
           </form>
           {render_html5_authoring_preview_result(project_id)}
+          <form
+            class="authoring-preview-form"
+            data-html5-authoring-diff-form
+            method="post"
+            action="/html5/projects/{quote(project_id)}/authoring/semantic-diff-preview"
+            hx-post="/html5/projects/{quote(project_id)}/authoring/semantic-diff-preview"
+            hx-target="[data-html5-authoring-diff-result]"
+            hx-swap="outerHTML"
+          >
+            <input name="routine_name" placeholder="routine_name" />
+            <input name="source_path" placeholder="source_path" />
+            <input name="task_id" placeholder="task_id" />
+            <input name="session_id" placeholder="session_id" />
+            <input name="user_id" placeholder="user_id" />
+            <textarea name="original_text" placeholder="Original BSL"></textarea>
+            <textarea name="proposed_text" placeholder="Proposed BSL"></textarea>
+            <button type="submit">Diff preview</button>
+          </form>
+          {render_html5_authoring_diff_result(project_id)}
         </div>
         """
     return render_html5_authoring_preview_result(project_id, preview, error)
@@ -411,6 +430,41 @@ def render_html5_authoring_preview_result(project_id: str, preview: object | Non
     """
 
 
+def render_html5_authoring_diff_result(project_id: str, preview: object | None = None, error: str | None = None) -> str:
+    if preview is None and error is None:
+        return '<div class="authoring-diff-result" data-html5-authoring-diff-result></div>'
+    if error:
+        return f"""
+        <div class="authoring-diff-result" data-html5-authoring-diff-result>
+          <div class="panel-title">Diff preview</div>
+          <p class="muted padded">{escape(error)}</p>
+        </div>
+        """
+    changed = bool(getattr(preview, "changed", False))
+    added = getattr(preview, "added_lines", 0)
+    removed = getattr(preview, "removed_lines", 0)
+    target = getattr(preview, "target", None)
+    target_name = getattr(target, "qualified_name", None) or getattr(target, "name", None) or "target unavailable"
+    checks = getattr(preview, "checks", []) or []
+    diff = getattr(preview, "semantic_diff", []) or []
+    version_preview = getattr(preview, "version_preview", None)
+    next_version_id = str(getattr(version_preview, "next_version_id", ""))
+    check_rows = "".join(_authoring_check_item(check) for check in checks[:8])
+    diff_rows = "".join(_authoring_diff_item(line) for line in diff[:12]) or '<p class="muted padded">Diff пустой</p>'
+    return f"""
+    <div class="authoring-diff-result" data-html5-authoring-diff-result data-html5-project-id="{escape(project_id)}">
+      <div class="panel-title">Diff preview · {'changed' if changed else 'unchanged'}</div>
+      <article class="authoring-change">
+        <strong>{escape(str(target_name))}</strong>
+        <span>+{escape(str(added))} / -{escape(str(removed))}</span>
+        <small>{escape(next_version_id or "version preview unavailable")}</small>
+      </article>
+      <div class="check-list">{check_rows}</div>
+      <div class="diff-list">{diff_rows}</div>
+    </div>
+    """
+
+
 def render_html5_authoring_change_detail(project_id: str, preview: object | None) -> str:
     if preview is None:
         return f"""