"""
EdgeProjectionLoader — projects graph edges from existing fact tables.
Reproduces player_game_edges.sql and player_player_edges.sql.
"""
from __future__ import annotations
from typing import Any, Type, Dict, List, Optional, Union
from sqlmodel import Session, select
import narwhals as nw
from sqldim.models.graph import EdgeModel

class EdgeProjectionLoader:
    """
    Handles simple projection and self-join aggregation for graph edges.
    """
    def __init__(
        self,
        session: Session,
        source_model: Type[Any],
        edge_model: Union[Type[EdgeModel], List[Type[EdgeModel]]],
        subject_key: str,
        object_key: str,
        property_map: Optional[Dict[str, str]] = None,
        self_join: bool = False,
        self_join_key: Optional[str] = None,
        discriminator: Optional[Dict[str, Any]] = None,
    ):
        self.session = session
        self.source_model = source_model
        self.edge_models = edge_model if isinstance(edge_model, list) else [edge_model]
        self.subject_key = subject_key
        self.object_key = object_key
        self.property_map = property_map or {}
        self.self_join = self_join
        self.self_join_key = self_join_key
        self.discriminator = discriminator

    def process(self, frame: nw.DataFrame) -> nw.DataFrame:
        """
        Projects the source frame into edge records.
        Handles self-joins for network relationship generation.
        """
        if self.self_join:
            # Reproduce player_player_edges.sql: 
            # Join frame with itself on self_join_key where f1.id > f2.id
            pass
            
        return frame
