from functools import lru_cache
from typing import Iterator, Optional

from strawberry.extensions.base_extension import SchemaExtension
from strawberry.schema.execute import validate_document


class ValidationCache(SchemaExtension):
    """Add LRU caching the validation step during execution to improve performance.

    Example:
    ```python
    import strawberry
    from strawberry.extensions import ValidationCache

    schema = strawberry.Schema(
        Query,
        extensions=[
            ValidationCache(maxsize=100),
        ],
    )
    ```
    """

    def __init__(self, maxsize: Optional[int] = None) -> None:
        """Initialize the ValidationCache.

        Args:
            maxsize: Set the maxsize of the cache. If `maxsize` is set to `None` then the
                cache will grow without bound.

        More info: https://docs.python.org/3/library/functools.html#functools.lru_cache
        """
        self.cached_validate_document = lru_cache(maxsize=maxsize)(validate_document)

    def on_validate(self) -> Iterator[None]:
        execution_context = self.execution_context

        errors = self.cached_validate_document(
            execution_context.schema._schema,
            execution_context.graphql_document,
            execution_context.validation_rules,
        )
        execution_context.errors = errors
        yield


__all__ = ["ValidationCache"]