# space/utils/config.py
import os
import logging
from typing import Optional
from dataclasses import dataclass, field

logger = logging.getLogger(__name__)


class ConfigError(Exception):
    """Custom exception for configuration errors."""
    pass


@dataclass
class AppConfig:
    """
    Application configuration loaded from environment variables.
    Includes validation and sensible defaults.
    """
    
    # SQL Backend Configuration
    sql_backend: str = "motherduck"  # "bigquery" or "motherduck"
    gcp_project: Optional[str] = None
    motherduck_token: Optional[str] = None
    motherduck_db: str = "workspace"
    
    # Model Configuration
    hf_model_repo: str = "your-org/your-model"
    hf_token: Optional[str] = None
    
    # Tracing Configuration
    trace_enabled: bool = True
    trace_url: Optional[str] = None
    
    # Feature Flags
    enable_forecasting: bool = True
    enable_explanations: bool = True
    
    # Performance Settings
    max_workers: int = 4
    timeout_seconds: int = 300
    
    # Additional settings
    log_level: str = "INFO"
    
    def __post_init__(self):
        """Validate configuration after initialization."""
        self._validate()
    
    def _validate(self):
        """Validate configuration values."""
        # Validate SQL backend
        valid_backends = ["bigquery", "motherduck"]
        if self.sql_backend not in valid_backends:
            raise ConfigError(
                f"Invalid sql_backend: {self.sql_backend}. "
                f"Must be one of: {valid_backends}"
            )
        
        # Validate backend-specific requirements
        if self.sql_backend == "bigquery":
            if not self.gcp_project:
                logger.warning("BigQuery selected but gcp_project not set")
        
        if self.sql_backend == "motherduck":
            if not self.motherduck_token:
                logger.warning("MotherDuck selected but motherduck_token not set")
        
        # Validate model configuration
        if not self.hf_model_repo:
            logger.warning("hf_model_repo not set - predictions/explanations will fail")
        
        # Validate numeric settings
        if self.max_workers < 1:
            raise ConfigError(f"max_workers must be >= 1, got {self.max_workers}")
        
        if self.timeout_seconds < 1:
            raise ConfigError(f"timeout_seconds must be >= 1, got {self.timeout_seconds}")
        
        # Validate log level
        valid_levels = ["DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"]
        if self.log_level.upper() not in valid_levels:
            raise ConfigError(
                f"Invalid log_level: {self.log_level}. "
                f"Must be one of: {valid_levels}"
            )
    
    @classmethod
    def from_env(cls) -> "AppConfig":
        """
        Create configuration from environment variables.
        
        Environment variables:
            SQL_BACKEND: "bigquery" or "motherduck" (default: "motherduck")
            GCP_PROJECT: GCP project ID for BigQuery
            GCP_SERVICE_ACCOUNT_JSON: Service account credentials for BigQuery
            MOTHERDUCK_TOKEN: MotherDuck authentication token
            MOTHERDUCK_DB: MotherDuck database name (default: "workspace")
            HF_MODEL_REPO: HuggingFace model repository (required)
            HF_TOKEN: HuggingFace API token (optional, for private repos)
            TRACE_ENABLED: Enable tracing (default: "true")
            TRACE_URL: Custom trace URL
            ENABLE_FORECASTING: Enable forecasting features (default: "true")
            ENABLE_EXPLANATIONS: Enable SHAP explanations (default: "true")
            MAX_WORKERS: Max parallel workers (default: 4)
            TIMEOUT_SECONDS: Request timeout (default: 300)
            LOG_LEVEL: Logging level (default: "INFO")
        """
        try:
            config = cls(
                sql_backend=os.getenv("SQL_BACKEND", "motherduck").lower(),
                gcp_project=os.getenv("GCP_PROJECT"),
                motherduck_token=os.getenv("MOTHERDUCK_TOKEN"),
                motherduck_db=os.getenv("MOTHERDUCK_DB", "workspace"),
                hf_model_repo=os.getenv("HF_MODEL_REPO", "your-org/your-model"),
                hf_token=os.getenv("HF_TOKEN"),
                trace_enabled=os.getenv("TRACE_ENABLED", "true").lower() == "true",
                trace_url=os.getenv("TRACE_URL"),
                enable_forecasting=os.getenv("ENABLE_FORECASTING", "true").lower() == "true",
                enable_explanations=os.getenv("ENABLE_EXPLANATIONS", "true").lower() == "true",
                max_workers=int(os.getenv("MAX_WORKERS", "4")),
                timeout_seconds=int(os.getenv("TIMEOUT_SECONDS", "300")),
                log_level=os.getenv("LOG_LEVEL", "INFO").upper()
            )
            
            logger.info("Configuration loaded successfully")
            logger.info(f"SQL Backend: {config.sql_backend}")
            logger.info(f"Model Repo: {config.hf_model_repo}")
            logger.info(f"Forecasting: {'enabled' if config.enable_forecasting else 'disabled'}")
            logger.info(f"Explanations: {'enabled' if config.enable_explanations else 'disabled'}")
            
            return config
            
        except ValueError as e:
            raise ConfigError(f"Invalid numeric configuration value: {e}") from e
        except Exception as e:
            raise ConfigError(f"Configuration loading failed: {e}") from e
    
    def to_dict(self) -> dict:
        """Convert configuration to dictionary (for logging/debugging)."""
        return {
            "sql_backend": self.sql_backend,
            "gcp_project": self.gcp_project or "not set",
            "motherduck_db": self.motherduck_db,
            "hf_model_repo": self.hf_model_repo,
            "hf_token_set": bool(self.hf_token),
            "trace_enabled": self.trace_enabled,
            "enable_forecasting": self.enable_forecasting,
            "enable_explanations": self.enable_explanations,
            "max_workers": self.max_workers,
            "timeout_seconds": self.timeout_seconds,
            "log_level": self.log_level
        }
    
    def validate_for_features(self, features: list) -> tuple[bool, list]:
        """
        Validate configuration supports requested features.
        
        Args:
            features: List of feature names to check
            
        Returns:
            Tuple of (all_valid, list_of_errors)
        """
        errors = []
        
        for feature in features:
            if feature == "predict" or feature == "explain":
                if not self.hf_model_repo or self.hf_model_repo == "your-org/your-model":
                    errors.append(f"{feature} requires valid HF_MODEL_REPO")
            
            elif feature == "forecast":
                if not self.enable_forecasting:
                    errors.append("forecasting is disabled (ENABLE_FORECASTING=false)")
            
            elif feature == "explain":
                if not self.enable_explanations:
                    errors.append("explanations are disabled (ENABLE_EXPLANATIONS=false)")
            
            elif feature == "sql":
                if self.sql_backend == "bigquery" and not self.gcp_project:
                    errors.append("BigQuery requires GCP_PROJECT")
                elif self.sql_backend == "motherduck" and not self.motherduck_token:
                    errors.append("MotherDuck requires MOTHERDUCK_TOKEN")
        
        return len(errors) == 0, errors