app/core/config.py

# app/core/config.py
import os
from pydantic_settings import BaseSettings
from typing import List, Union, Optional
from pydantic import AnyHttpUrl, validator, PostgresDsn
import logging
from dotenv import dotenv_values

logger = logging.getLogger(__name__)

class Settings(BaseSettings):
    PROJECT_NAME: str = "Chatbot Backend V2"
    API_V2_PREFIX: str = "/api/v2"
    DATABASE_URL: PostgresDsn
    NEO4J_URI: Optional[str] = None
    NEO4J_USERNAME: Optional[str] = None
    NEO4J_PASSWORD: Optional[str] = None
    NEO4J_DATABASE: Optional[str] = "neo4j"
    OPENAI_API_KEY: str
    OPENAI_MODEL_NAME: str = "gpt-4-turbo"
    
    RETRIEVAL_ARTIFACTS_PATH: str = "data/final_retrieval_artifacts.npz"
    QUERY_ENCODER_MODEL_NAME: str = "BAAI/bge-m3"

    S3_ARTIFACTS_URL: Optional[str] = None
    S3_RERANKER_URL: Optional[str] = None
    
    RERANKER_MODEL_PATH: str = "data/best_expert_judge_cross_encoder.pt" # Or the exact name of your saved .pt file
    RERANKER_MODEL_NAME: str = "mixedbread-ai/mxbai-rerank-base-v2" # The base model used in your training script
    RERANKER_SCORE_THRESHOLD: float = 0.0
    RERANKER_K_MIN: int = 5
    RERANKER_FALLOFF_THRESHOLD: int = 1
    RERANKER_K_MAX: int = 100

    SEQUENCE_EXPANSION_THRESHOLD: float =0.68
    
    BACKEND_CORS_ORIGINS: Union[str, List[AnyHttpUrl]] = "http://localhost:5173"

    @validator("BACKEND_CORS_ORIGINS", pre=True)
    def assemble_cors_origins(cls, v: Union[str, List[str]]) -> Union[List[str], str]:
        if isinstance(v, str) and not v.startswith("["):
            return [i.strip() for i in v.split(",")]
        elif isinstance(v, list):
            return v
        raise ValueError(v)

    class Config:
        case_sensitive = True
        env_file = '.env'
        env_file_encoding = 'utf-8'
        # --- FIX: Ignore extra fields from the .env file ---
        # This prevents the app from crashing if obsolete variables like
        # GNN_EMBEDDINGS_NPZ_PATH are still present.
        extra = 'ignore'
        # --- END OF FIX ---

settings = Settings()