import asyncio
from typing import List, Optional

from sqlalchemy import select
from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import selectinload

from letta.orm.errors import NoResultFound
from letta.orm.file import FileContent as FileContentModel
from letta.orm.file import FileMetadata as FileMetadataModel
from letta.orm.source import Source as SourceModel
from letta.orm.sqlalchemy_base import AccessType
from letta.schemas.agent import AgentState as PydanticAgentState
from letta.schemas.file import FileMetadata as PydanticFileMetadata
from letta.schemas.source import Source as PydanticSource
from letta.schemas.source import SourceUpdate
from letta.schemas.user import User as PydanticUser
from letta.server.db import db_registry
from letta.tracing import trace_method
from letta.utils import enforce_types, printd


class SourceManager:
    """Manager class to handle business logic related to Sources."""

    @enforce_types
    @trace_method
    async def create_source(self, source: PydanticSource, actor: PydanticUser) -> PydanticSource:
        """Create a new source based on the PydanticSource schema."""
        # Try getting the source first by id
        db_source = await self.get_source_by_id(source.id, actor=actor)
        if db_source:
            return db_source
        else:
            async with db_registry.async_session() as session:
                # Provide default embedding config if not given
                source.organization_id = actor.organization_id
                source = SourceModel(**source.model_dump(to_orm=True, exclude_none=True))
                await source.create_async(session, actor=actor)
                return source.to_pydantic()

    @enforce_types
    @trace_method
    async def update_source(self, source_id: str, source_update: SourceUpdate, actor: PydanticUser) -> PydanticSource:
        """Update a source by its ID with the given SourceUpdate object."""
        async with db_registry.async_session() as session:
            source = await SourceModel.read_async(db_session=session, identifier=source_id, actor=actor)

            # get update dictionary
            update_data = source_update.model_dump(to_orm=True, exclude_unset=True, exclude_none=True)
            # Remove redundant update fields
            update_data = {key: value for key, value in update_data.items() if getattr(source, key) != value}

            if update_data:
                for key, value in update_data.items():
                    setattr(source, key, value)
                await source.update_async(db_session=session, actor=actor)
            else:
                printd(
                    f"`update_source` was called with user_id={actor.id}, organization_id={actor.organization_id}, name={source.name}, but found existing source with nothing to update."
                )

            return source.to_pydantic()

    @enforce_types
    @trace_method
    async def delete_source(self, source_id: str, actor: PydanticUser) -> PydanticSource:
        """Delete a source by its ID."""
        async with db_registry.async_session() as session:
            source = await SourceModel.read_async(db_session=session, identifier=source_id)
            await source.hard_delete_async(db_session=session, actor=actor)
            return source.to_pydantic()

    @enforce_types
    @trace_method
    async def list_sources(
        self, actor: PydanticUser, after: Optional[str] = None, limit: Optional[int] = 50, **kwargs
    ) -> List[PydanticSource]:
        """List all sources with optional pagination."""
        async with db_registry.async_session() as session:
            sources = await SourceModel.list_async(
                db_session=session,
                after=after,
                limit=limit,
                organization_id=actor.organization_id,
                **kwargs,
            )
            return [source.to_pydantic() for source in sources]

    @enforce_types
    @trace_method
    async def size_async(self, actor: PydanticUser) -> int:
        """
        Get the total count of sources for the given user.
        """
        async with db_registry.async_session() as session:
            return await SourceModel.size_async(db_session=session, actor=actor)

    @enforce_types
    @trace_method
    async def list_attached_agents(self, source_id: str, actor: Optional[PydanticUser] = None) -> List[PydanticAgentState]:
        """
        Lists all agents that have the specified source attached.

        Args:
            source_id: ID of the source to find attached agents for
            actor: User performing the action (optional for now, following existing pattern)

        Returns:
            List[PydanticAgentState]: List of agents that have this source attached
        """
        async with db_registry.async_session() as session:
            # Verify source exists and user has permission to access it
            source = await SourceModel.read_async(db_session=session, identifier=source_id, actor=actor)

            # The agents relationship is already loaded due to lazy="selectin" in the Source model
            # and will be properly filtered by organization_id due to the OrganizationMixin
            agents_orm = source.agents
            return await asyncio.gather(*[agent.to_pydantic_async() for agent in agents_orm])

    # TODO: We make actor optional for now, but should most likely be enforced due to security reasons
    @enforce_types
    @trace_method
    async def get_source_by_id(self, source_id: str, actor: Optional[PydanticUser] = None) -> Optional[PydanticSource]:
        """Retrieve a source by its ID."""
        async with db_registry.async_session() as session:
            try:
                source = await SourceModel.read_async(db_session=session, identifier=source_id, actor=actor)
                return source.to_pydantic()
            except NoResultFound:
                return None

    @enforce_types
    @trace_method
    async def get_source_by_name(self, source_name: str, actor: PydanticUser) -> Optional[PydanticSource]:
        """Retrieve a source by its name."""
        async with db_registry.async_session() as session:
            sources = await SourceModel.list_async(
                db_session=session,
                name=source_name,
                organization_id=actor.organization_id,
                limit=1,
            )
            if not sources:
                return None
            else:
                return sources[0].to_pydantic()

    @enforce_types
    @trace_method
    async def create_file(
        self,
        file_metadata: PydanticFileMetadata,
        actor: PydanticUser,
        *,
        text: Optional[str] = None,
    ) -> PydanticFileMetadata:

        # short-circuit if it already exists
        existing = await self.get_file_by_id(file_metadata.id, actor=actor)
        if existing:
            return existing

        async with db_registry.async_session() as session:
            try:
                file_metadata.organization_id = actor.organization_id
                file_orm = FileMetadataModel(**file_metadata.model_dump(to_orm=True, exclude_none=True))
                await file_orm.create_async(session, actor=actor, no_commit=True)

                if text is not None:
                    content_orm = FileContentModel(file_id=file_orm.id, text=text)
                    await content_orm.create_async(session, actor=actor, no_commit=True)

                await session.commit()
                await session.refresh(file_orm)
                return await file_orm.to_pydantic_async()

            except IntegrityError:
                await session.rollback()
                return await self.get_file_by_id(file_metadata.id, actor=actor)

    # TODO: We make actor optional for now, but should most likely be enforced due to security reasons
    @enforce_types
    @trace_method
    async def get_file_by_id(
        self,
        file_id: str,
        actor: Optional[PydanticUser] = None,
        *,
        include_content: bool = False,
    ) -> Optional[PydanticFileMetadata]:
        """Retrieve a file by its ID.

        If `include_content=True`, the FileContent relationship is eagerly
        loaded so `to_pydantic(include_content=True)` never triggers a
        lazy SELECT (avoids MissingGreenlet).
        """
        async with db_registry.async_session() as session:
            try:
                if include_content:
                    # explicit eager load
                    query = (
                        select(FileMetadataModel).where(FileMetadataModel.id == file_id).options(selectinload(FileMetadataModel.content))
                    )
                    # apply org-scoping if actor provided
                    if actor:
                        query = FileMetadataModel.apply_access_predicate(
                            query,
                            actor,
                            access=["read"],
                            access_type=AccessType.ORGANIZATION,
                        )

                    result = await session.execute(query)
                    file_orm = result.scalar_one()
                else:
                    # fast path (metadata only)
                    file_orm = await FileMetadataModel.read_async(
                        db_session=session,
                        identifier=file_id,
                        actor=actor,
                    )

                return await file_orm.to_pydantic_async(include_content=include_content)

            except NoResultFound:
                return None

    @enforce_types
    @trace_method
    async def list_files(
        self, source_id: str, actor: PydanticUser, after: Optional[str] = None, limit: Optional[int] = 50, include_content: bool = False
    ) -> List[PydanticFileMetadata]:
        """List all files with optional pagination."""
        async with db_registry.async_session() as session:
            options = [selectinload(FileMetadataModel.content)] if include_content else None

            files = await FileMetadataModel.list_async(
                db_session=session,
                after=after,
                limit=limit,
                organization_id=actor.organization_id,
                source_id=source_id,
                query_options=options,
            )
            return [await file.to_pydantic_async(include_content=include_content) for file in files]

    @enforce_types
    @trace_method
    async def delete_file(self, file_id: str, actor: PydanticUser) -> PydanticFileMetadata:
        """Delete a file by its ID."""
        async with db_registry.async_session() as session:
            file = await FileMetadataModel.read_async(db_session=session, identifier=file_id)
            await file.hard_delete_async(db_session=session, actor=actor)
            return await file.to_pydantic_async()