from typing import Dict, Iterator, List, Optional

from langchain_core.document_loaders.base import BaseLoader
from langchain_core.documents import Document


class NeedleLoader(BaseLoader):
    """
    NeedleLoader is a document loader for managing documents stored in a collection.

    Setup:
        Install the `needle-python` library and set your Needle API key.

        .. code-block:: bash

            pip install needle-python
            export NEEDLE_API_KEY="your-api-key"

    Key init args:
        - `needle_api_key` (Optional[str]): API key for authenticating with Needle.
        - `collection_id` (str): Needle collection to load documents from.

    Usage:
        .. code-block:: python

            from langchain_community.document_loaders.needle import NeedleLoader

            loader = NeedleLoader(
                needle_api_key="your-api-key",
                collection_id="your-collection-id"
            )

            # Load documents
            documents = loader.load()
            for doc in documents:
                print(doc.metadata)

            # Lazy load documents
            for doc in loader.lazy_load():
                print(doc.metadata)
    """

    def __init__(
        self,
        needle_api_key: Optional[str] = None,
        collection_id: Optional[str] = None,
    ) -> None:
        """
        Initializes the NeedleLoader with API key and collection ID.

        Args:
            needle_api_key (Optional[str]): API key for authenticating with Needle.
            collection_id (Optional[str]): Identifier for the Needle collection.

        Raises:
            ImportError: If the `needle-python` library is not installed.
            ValueError: If the collection ID is not provided.
        """
        try:
            from needle.v1 import NeedleClient
        except ImportError:
            raise ImportError(
                "Please install with `pip install needle-python` to use NeedleLoader."
            )

        super().__init__()
        self.needle_api_key = needle_api_key
        self.collection_id = collection_id
        self.client: Optional[NeedleClient] = None

        if self.needle_api_key:
            self.client = NeedleClient(api_key=self.needle_api_key)

        if not self.collection_id:
            raise ValueError("Collection ID must be provided.")

    def _get_collection(self) -> None:
        """
        Ensures the Needle collection is set and the client is initialized.

        Raises:
            ValueError: If the Needle client is not initialized or
                        if the collection ID is missing.
        """
        if self.client is None:
            raise ValueError(
                "NeedleClient is not initialized. Provide a valid API key."
            )
        if not self.collection_id:
            raise ValueError("Collection ID must be provided.")

    def add_files(self, files: Dict[str, str]) -> None:
        """
        Adds files to the Needle collection.

        Args:
            files (Dict[str, str]): Dictionary where keys are file names and values
                                    are file URLs.

        Raises:
            ImportError: If the `needle-python` library is not installed.
            ValueError: If the collection is not properly initialized.
        """
        try:
            from needle.v1.models import FileToAdd
        except ImportError:
            raise ImportError(
                "Please install with `pip install needle-python` to add files."
            )

        self._get_collection()
        assert self.client is not None, "NeedleClient must be initialized."

        files_to_add = [FileToAdd(name=name, url=url) for name, url in files.items()]

        self.client.collections.files.add(
            collection_id=self.collection_id, files=files_to_add
        )

    def _fetch_documents(self) -> List[Document]:
        """
        Fetches metadata for documents from the Needle collection.

        Returns:
            List[Document]: A list of documents with metadata. Content is excluded.

        Raises:
            ValueError: If the collection is not properly initialized.
        """
        self._get_collection()
        assert self.client is not None, "NeedleClient must be initialized."

        files = self.client.collections.files.list(self.collection_id)
        docs = [
            Document(
                page_content="",  # Needle doesn't provide file content fetching
                metadata={
                    "source": file.url,
                    "title": file.name,
                    "size": getattr(file, "size", None),
                },
            )
            for file in files
            if file.status == "indexed"
        ]
        return docs

    def load(self) -> List[Document]:
        """
        Loads all documents from the Needle collection.

        Returns:
            List[Document]: A list of documents from the collection.
        """
        return self._fetch_documents()

    def lazy_load(self) -> Iterator[Document]:
        """
        Lazily loads documents from the Needle collection.

        Yields:
            Iterator[Document]: An iterator over the documents.
        """
        yield from self._fetch_documents()