"""
Application configuration management.

Simple configuration with sensible defaults. SQLite by default for development,
PostgreSQL supported via DATABASE_URL environment variable.

## Usage

    from app.core.config import get_config

    config = get_config()
    print(config.DATABASE_URL)

## Environment Variables

All configuration values can be overridden via environment variables.
The .env file in the project root is also loaded automatically.

| Variable | Default | Description |
|---|---|---|
| APP_NAME | MTG Online | Application display name |
| APP_VERSION | 0.2.0 | Application version |
| DEBUG | false | Enable debug mode |
| SECRET_KEY | change-me-in-production | Application secret key |
| JWT_SECRET_KEY | (same as SECRET_KEY) | JWT signing key |
| DATABASE_URL | sqlite:///./mtgonline.db | Database connection string |
| JWT_ALGORITHM | HS256 | JWT signing algorithm |
| JWT_ACCESS_TOKEN_EXPIRE_MINUTES | 60 | Access token lifetime |
| JWT_REFRESH_TOKEN_EXPIRE_DAYS | 7 | Refresh token lifetime |
| CORS_ORIGINS | ["http://localhost:3000", "http://localhost:8000"] | Allowed CORS origins |
| BCRYPT_ROUNDS | 12 | Bcrypt hashing rounds |
| LOG_LEVEL | INFO | Logging level |
| LOG_FORMAT | text | Log output format (text or json) |
| DATA_DIR | /app/data | Data directory for MTGJSON files |
| UPLOAD_DIR | /app/uploads | Upload directory |
"""

import os
from typing import Optional


def _load_env_file(path: str) -> None:
    """Load environment variables from a .env file if it exists.

    Args:
        path: Absolute or relative path to the .env file.
    """
    if os.path.isfile(path):
        with open(path, "r", encoding="utf-8") as f:
            for line in f:
                line = line.strip()
                if not line or line.startswith("#"):
                    continue
                if "=" not in line:
                    continue
                key, _, value = line.partition("=")
                key = key.strip()
                value = value.strip().strip("\"'")
                if key and value and key not in os.environ:
                    os.environ[key] = value


# Load .env from project root (one level up from backend/app/core/)
_project_root = os.path.abspath(os.path.join(os.path.dirname(__file__), "../../.."))
_env_path = os.path.join(_project_root, ".env")
_load_env_file(_env_path)

# Also try backend/.env
_backend_env = os.path.join(_project_root, "..", ".env")
_load_env_file(os.path.abspath(_backend_env))


class Config:
    """Application configuration with sensible defaults.

    All values can be overridden via environment variables.
    This is a simple class (not pydantic-settings) for minimal dependencies.

    Attributes:
        APP_NAME: Application display name.
        APP_VERSION: Application version string.
        DEBUG: Enable debug mode (enables SQL echo, etc.).
        SECRET_KEY: Application secret key for signing.
        JWT_SECRET_KEY: JWT signing key (falls back to SECRET_KEY).
        DATABASE_URL: SQLAlchemy database connection string.
            Defaults to SQLite for development.
        JWT_ALGORITHM: JWT signing algorithm (default HS256).
        JWT_ACCESS_TOKEN_EXPIRE_MINUTES: Access token lifetime in minutes.
        JWT_REFRESH_TOKEN_EXPIRE_DAYS: Refresh token lifetime in days.
        CORS_ORIGINS: List of allowed CORS origin URLs.
        BCRYPT_ROUNDS: Number of bcrypt hashing rounds.
        LOG_LEVEL: Logging level (DEBUG, INFO, WARNING, ERROR, CRITICAL).
        LOG_FORMAT: Log output format (text or json).
        DATA_DIR: Directory for MTGJSON data files.
        UPLOAD_DIR: Directory for user uploads.
    """

    # Application
    APP_NAME: str = "MTG Online"
    APP_VERSION: str = "0.2.0"
    DEBUG: bool = False
    SECRET_KEY: str = "change-me-in-production"
    JWT_SECRET_KEY: str = ""  # Falls back to SECRET_KEY if empty

    # Database - single unified connection string
    DATABASE_URL: str = "sqlite+aiosqlite:///./mtgonline.db"

    # JWT Configuration
    JWT_ALGORITHM: str = "HS256"
    JWT_ACCESS_TOKEN_EXPIRE_MINUTES: int = 60
    JWT_REFRESH_TOKEN_EXPIRE_DAYS: int = 7

    # CORS
    CORS_ORIGINS: list[str] = ["http://localhost:3000", "http://localhost:8000"]

    # Security
    BCRYPT_ROUNDS: int = 12

    # Logging
    LOG_LEVEL: str = "INFO"
    LOG_FORMAT: str = "text"

    # Directories
    DATA_DIR: str = "/app/data"
    UPLOAD_DIR: str = "/app/uploads"

    def __init__(self) -> None:
        """Initialize configuration from environment variables."""
        self._apply_env_overrides()

    def _apply_env_overrides(self) -> None:
        """Override configuration values from environment variables."""
        env_map: dict[str, type] = {
            "APP_NAME": str,
            "APP_VERSION": str,
            "DEBUG": bool,
            "SECRET_KEY": str,
            "JWT_SECRET_KEY": str,
            "DATABASE_URL": str,
            "JWT_ALGORITHM": str,
            "JWT_ACCESS_TOKEN_EXPIRE_MINUTES": int,
            "JWT_REFRESH_TOKEN_EXPIRE_DAYS": int,
            "BCRYPT_ROUNDS": int,
            "LOG_LEVEL": str,
            "LOG_FORMAT": str,
            "DATA_DIR": str,
            "UPLOAD_DIR": str,
        }

        for attr, type_cast in env_map.items():
            value = os.environ.get(attr)
            if value is not None:
                if type_cast == bool:
                    value = value.lower() in ("true", "1", "yes", "on")
                else:
                    value = type_cast(value)
                setattr(self, attr, value)

        # CORS_ORIGINS: parse comma-separated from env or keep default list
        cors_env = os.environ.get("CORS_ORIGINS")
        if cors_env:
            self.CORS_ORIGINS = [
                origin.strip() for origin in cors_env.split(",") if origin.strip()
            ]

    @property
    def jwt_secret(self) -> str:
        """Get the effective JWT secret key.

        Returns JWT_SECRET_KEY if set, otherwise falls back to SECRET_KEY.

        Returns:
            The JWT secret key string.
        """
        return self.JWT_SECRET_KEY or self.SECRET_KEY

    @property
    def is_sqlite(self) -> bool:
        """Check if the database is SQLite.

        Returns:
            True if using SQLite, False otherwise.
        """
        return self.DATABASE_URL.startswith("sqlite")

    @property
    def is_postgresql(self) -> bool:
        """Check if the database is PostgreSQL.

        Returns:
            True if using PostgreSQL, False otherwise.
        """
        return "postgresql" in self.DATABASE_URL


# Singleton instance
_config_instance: Optional[Config] = None


def get_config() -> Config:
    """Get the application configuration singleton.

    Returns a cached Config instance. Subsequent calls return the same object.

    Returns:
        The application configuration instance.

    Example:
        >>> config = get_config()
        >>> print(config.DATABASE_URL)
        sqlite:///./mtgonline.db
    """
    global _config_instance
    if _config_instance is None:
        _config_instance = Config()
    return _config_instance