Help for web.nav.view_style_switcher

def view_style_switcher(*, css=None, project=None):
    """
    Shows available styles (global + project), lets user choose, preview, and see raw CSS.
    If cookies are accepted, sets the style via cookie when changed in dropdown.
    If cookies are not accepted, only uses the css param for preview.
    """
    import os
    from bottle import request, response

    # Determine the project from context or fallback if not provided
    if not project:
        path = request.fullpath.strip("/").split("/")
        if path and path[0] in ("conway", "awg", "site", "etron"):
            project = path[0]
        else:
            project = "site"

    def list_styles_local(project):
        seen = set()
        styles = []
        # Global styles
        global_dir = gw.resource("data", "static", "styles")
        if os.path.isdir(global_dir):
            for f in sorted(os.listdir(global_dir)):
                if f.endswith(".css") and os.path.isfile(os.path.join(global_dir, f)):
                    if f not in seen:
                        styles.append(("global", f))
                        seen.add(f)
        if project:
            proj_dir = gw.resource("data", "static", project, "styles")
            if os.path.isdir(proj_dir):
                for f in sorted(os.listdir(proj_dir)):
                    if f.endswith(".css") and os.path.isfile(os.path.join(proj_dir, f)):
                        if f not in seen:
                            styles.append((project, f))
                            seen.add(f)
        return styles

    styles = list_styles_local(project)
    all_styles = [fname for _, fname in styles]
    style_sources = {fname: src for src, fname in styles}

    cookies_enabled = gw.web.app.is_enabled('web.cookies')
    cookies_accepted = gw.web.cookies.check_consent() if cookies_enabled else False
    css_cookie = gw.web.cookies.get("css")

    # Handle POST
    if request.method == "POST":
        selected_style = request.forms.get("css")
        if cookies_enabled and cookies_accepted and selected_style and selected_style in all_styles:
            gw.web.cookies.set("css", selected_style)
            response.status = 303
            response.set_header("Location", request.fullpath)
            return ""

    # --- THIS IS THE MAIN LOGIC: ---
    # Priority: query param > explicit function arg > cookie > default
    style_query = request.query.get("css")
    selected_style = (
        style_query if style_query in all_styles else
        (css if css in all_styles else
         (css_cookie if css_cookie in all_styles else
          (all_styles[0] if all_styles else "base.css")))
    )
    # If still not valid, fallback to default
    if selected_style not in all_styles:
        selected_style = all_styles[0] if all_styles else "base.css"

    # Determine preview link and path for raw CSS
    if style_sources.get(selected_style) == "global":
        preview_href = f"/static/styles/{selected_style}"
        css_path = gw.resource("data", "static", "styles", selected_style)
        css_link = f'<link rel="stylesheet" href="/static/styles/{selected_style}">'
    else:
        preview_href = f"/static/{project}/styles/{selected_style}"
        css_path = gw.resource("data", "static", project, "styles", selected_style)
        css_link = f'<link rel="stylesheet" href="/static/{project}/styles/{selected_style}">'

    preview_html = f"""
        {css_link}
        <div class="style-preview">
            <h2>Theme Preview: {selected_style[:-4].replace('_', ' ').title()}</h2>
            <p>This is a preview of the <b>{selected_style}</b> theme.</p>
            <button>Sample button</button>
            <pre>code block</pre>
        </div>
    """
    css_code = ""
    try:
        with open(css_path, encoding="utf-8") as f:
            css_code = f.read()
    except Exception:
        css_code = "Could not load CSS file."

    selector = style_selector_form(
        all_styles=styles,
        selected_style=selected_style,
        cookies_enabled=cookies_enabled,
        cookies_accepted=cookies_accepted,
        project=project
    )

    return f"""
        <h1>Select a Site Theme</h1>
        {selector}
        {preview_html}
        <h3>CSS Source: {selected_style}</h3>
        <pre style="max-height:400px;overflow:auto;">{html_escape(css_code)}</pre>
    """