import re

_LINK_WITH_LABEL_PATTERN: re.Pattern[str] = re.compile(r'\[(?P<label>[^\[\]]+?)\]\s*\{link\}', re.IGNORECASE)
_LINK_PLACEHOLDER_PATTERN: re.Pattern[str] = re.compile(r'\{link\}', re.IGNORECASE)
_LINK_CLASS = 'tg-link'


def _replace_label_placeholder(match: re.Match[str]) -> str:
    label = match.group('label')
    return f'<a class="{_LINK_CLASS}">{label}</a>'


def prepare_creative_text_html(source: str) -> str:
    """Normalize Telegram HTML and replace {link} placeholder with custom elements.

    Supported patterns:
    - ``{link}`` → ``<a class="tg-link"></a>``
    - ``[Label]{link}`` → ``<a class="tg-link">Label</a>``
    """

    with_labels = _LINK_WITH_LABEL_PATTERN.sub(_replace_label_placeholder, source)
    return _LINK_PLACEHOLDER_PATTERN.sub(f'<a class="{_LINK_CLASS}"></a>', with_labels)