UI Improvements (#7)

* Initial version with UI templates

* Implement basic screens

* Linting & bump to 0.3.0

* Tick off some TODOs

custom_components/auth_oidc/views/loader.py

@@ -0,0 +1,60 @@
+"""Jinja2 Async Environment"""
+
+import logging
+from os import path
+from typing import Dict, Any
+from jinja2 import Environment, DictLoader
+from aiofiles.os import scandir as async_scandir
+from aiofiles import open as async_open
+
+_LOGGER = logging.getLogger(__name__)
+
+templates: Dict[str, str] = {}
+
+
+class AsyncTemplateRenderer:
+    """An asynchronous template renderer that caches rendered templates."""
+
+    def __init__(self, template_dir: str = None):
+        self.template_dir = template_dir or path.dirname(path.abspath(__file__))
+
+    async def fetch_templates(self) -> None:
+        """Fetches all HTML files from the template directory."""
+        templates.clear()
+
+        files = await async_scandir(self.template_dir)
+
+        for file in files:
+            if file.is_dir():
+                continue
+
+            filename = file.name
+            if filename.endswith(".html"):
+                template_path = path.join(self.template_dir, filename)
+                try:
+                    _LOGGER.debug("Fetching template %s from disk", filename)
+                    async with async_open(
+                        template_path, mode="r", encoding="utf-8"
+                    ) as f:
+                        content = await f.read()
+                        templates[filename] = content
+                except (OSError, IOError) as e:
+                    _LOGGER.warning("Error reading template file %s: %s", filename, e)
+
+    async def render_template(self, template_name: str, **kwargs: Any) -> str:
+        """Renders a template with the given parameters."""
+
+        if not templates:
+            await (
+                self.fetch_templates()
+            )  # If the templates haven't been fetched, fetch them
+
+        if template_name not in templates:
+            raise ValueError(f"Template '{template_name}' not found.")
+
+        env = Environment(loader=DictLoader(templates), enable_async=True)
+        template = env.get_template(template_name)
+
+        # Render template
+        rendered_output = await template.render_async(**kwargs)
+        return rendered_output