import os
from pathlib import Path


BASE_DIR = Path(__file__).resolve().parent


def environment_flag(name: str, *, default: bool = False) -> bool:
    value = os.environ.get(name)
    if value is None:
        return default
    return value.strip().lower() in {"1", "true", "yes", "on"}


def environment_list(name: str) -> list[str] | None:
    values = [value.strip() for value in os.environ.get(name, "").split(",")]
    filtered = [value for value in values if value]
    return filtered or None


class Config:
    """Shared settings with secure production-oriented defaults."""

    SECRET_KEY = os.environ.get("SECRET_KEY")
    SQLALCHEMY_DATABASE_URI = os.environ.get(
        "DATABASE_URL",
        f"sqlite:///{BASE_DIR / 'instance' / 'steady.db'}",
    )
    SQLALCHEMY_TRACK_MODIFICATIONS = False
    SESSION_COOKIE_HTTPONLY = True
    SESSION_COOKIE_SAMESITE = "Lax"
    SESSION_COOKIE_SECURE = True
    REMEMBER_COOKIE_HTTPONLY = True
    REMEMBER_COOKIE_SAMESITE = "Lax"
    REMEMBER_COOKIE_SECURE = True
    WTF_CSRF_TIME_LIMIT = 3600
    MAX_CONTENT_LENGTH = 2 * 1024 * 1024
    TRUSTED_HOSTS = environment_list("TRUSTED_HOSTS")
    TRUST_PROXY_HEADERS = environment_flag("TRUST_PROXY_HEADERS")
    ENABLE_HSTS = False

    FEATURE_ADMIN = environment_flag("FEATURE_ADMIN")
    FEATURE_API_V1 = False
    FEATURE_BROWSER_REMINDERS = False


class DevelopmentConfig(Config):
    DEBUG = True
    SECRET_KEY = os.environ.get("SECRET_KEY", "development-only-change-me")
    SESSION_COOKIE_SECURE = False
    REMEMBER_COOKIE_SECURE = False


class TestingConfig(Config):
    TESTING = True
    SECRET_KEY = "testing-only"
    SQLALCHEMY_DATABASE_URI = "sqlite:///:memory:"
    WTF_CSRF_ENABLED = False
    SESSION_COOKIE_SECURE = False
    REMEMBER_COOKIE_SECURE = False


class ProductionConfig(Config):
    ENABLE_HSTS = True
    PREFERRED_URL_SCHEME = "https"


CONFIGS = {
    "development": DevelopmentConfig,
    "testing": TestingConfig,
    "production": ProductionConfig,
}