"""Bound the upstream work requested by a single search."""

MAX_SEARCH_TERMS = 20
MAX_TEXT_TERM_CHARS = 2_000
MAX_TOTAL_TEXT_CHARS = 10_000


class SearchLimitError(ValueError):
    """A search exceeds the public per-search limits."""


def validate_search_size(text_queries=None, image_queries=None):
    """Reject the whole search before any terms are sent upstream.

    Count Python Unicode characters, consistently for direct and shared searches.
    This intentionally imposes no per-user or per-IP search quota.
    """
    text_queries = [] if text_queries is None else text_queries
    image_queries = [] if image_queries is None else image_queries
    if not isinstance(text_queries, (list, tuple)) or not isinstance(image_queries, (list, tuple)):
        raise SearchLimitError("Search terms must be supplied as lists.")
    if len(text_queries) + len(image_queries) > MAX_SEARCH_TERMS:
        raise SearchLimitError(f"Use at most {MAX_SEARCH_TERMS} text and image terms per search.")

    total_chars = 0
    for query in text_queries:
        if not isinstance(query, str):
            raise SearchLimitError("Each text term must be text.")
        if len(query) > MAX_TEXT_TERM_CHARS:
            raise SearchLimitError(f"Use at most {MAX_TEXT_TERM_CHARS:,} characters per text term.")
        total_chars += len(query)
    if total_chars > MAX_TOTAL_TEXT_CHARS:
        raise SearchLimitError(f"Use at most {MAX_TOTAL_TEXT_CHARS:,} text characters per search.")