from typing import Any, Iterator

from langchain.docstore.document import Document
from langchain.document_loaders.dataframe import BaseDataFrameLoader


class PolarsDataFrameLoader(BaseDataFrameLoader):
    """Load `Polars` DataFrame."""

    def __init__(self, data_frame: Any, *, page_content_column: str = "text"):
        """Initialize with dataframe object.

        Args:
            data_frame: Polars DataFrame object.
            page_content_column: Name of the column containing the page content.
              Defaults to "text".
        """
        import polars as pl

        if not isinstance(data_frame, pl.DataFrame):
            raise ValueError(
                f"Expected data_frame to be a pl.DataFrame, got {type(data_frame)}"
            )
        super().__init__(data_frame, page_content_column=page_content_column)

    def lazy_load(self) -> Iterator[Document]:
        """Lazy load records from dataframe."""

        for row in self.data_frame.iter_rows(named=True):
            text = row[self.page_content_column]
            row.pop(self.page_content_column)
            yield Document(page_content=text, metadata=row)
