import os
from datetime import timedelta
from dotenv import load_dotenv

# Load .env from the project root (only takes effect locally; no-op in production
# if variables are already set in the environment)
load_dotenv()

basedir = os.path.abspath(os.path.dirname(__file__))


def _require_env(key: str) -> str:
    """Return the value of a required environment variable, raising if absent."""
    value = os.environ.get(key)
    if not value:
        raise RuntimeError(
            f"Required environment variable '{key}' is not set. "
            f"Add it to your .env file (development) or server environment (production)."
        )
    return value


class Config:
    # ── Security ────────────────────────────────────────────────────────────
    # SECRET_KEY must be set externally — no insecure fallback.
    SECRET_KEY = _require_env('SECRET_KEY')

    # ── Database ────────────────────────────────────────────────────────────
    # DATABASE_URL must be set externally — no hardcoded credentials.
    SQLALCHEMY_DATABASE_URI = _require_env('DATABASE_URL')
    SQLALCHEMY_TRACK_MODIFICATIONS = False
    SQLALCHEMY_ECHO = False

    # ── Multi-tenancy (MT-1) ─────────────────────────────────────────────────
    # Master switch. When False (default) the app behaves EXACTLY as the
    # single-tenant deployment: no Host resolution, every query uses
    # SQLALCHEMY_DATABASE_URI. Flip to True only after tenants are registered
    # in the control plane (see MULTI_TENANT_PLAN.md). The control plane env
    # vars (CONTROL_DATABASE_URL, CONTROL_FERNET_KEY) are only required when
    # this is True.
    MULTI_TENANT_ENABLED = os.environ.get(
        'MULTI_TENANT_ENABLED', 'false'
    ).strip().lower() in ('1', 'true', 'yes', 'on')
    # Path prefixes that bypass the tenant gate even when enabled (e.g. health
    # checks). '/static/' is always exempt. Comma-separated in the environment.
    MULTI_TENANT_EXEMPT_PATHS = [
        p.strip() for p in os.environ.get('MULTI_TENANT_EXEMPT_PATHS', '').split(',')
        if p.strip()
    ]
    # Per-tenant SQLAlchemy engine pool tuning (see MULTI_TENANT_PLAN.md §4).
    TENANT_ENGINE_POOL_SIZE    = int(os.environ.get('TENANT_ENGINE_POOL_SIZE', 5))
    TENANT_ENGINE_MAX_OVERFLOW = int(os.environ.get('TENANT_ENGINE_MAX_OVERFLOW', 5))
    TENANT_ENGINE_POOL_RECYCLE = int(os.environ.get('TENANT_ENGINE_POOL_RECYCLE', 1800))

    # ── File uploads ────────────────────────────────────────────────────────
    UPLOAD_FOLDER = os.path.join(basedir, 'app/static/uploads')
    MAX_CONTENT_LENGTH = 50 * 1024 * 1024   # 50 MB
    ALLOWED_EXTENSIONS = {'png', 'jpg', 'jpeg', 'gif'}

    # ── Session / cookies ───────────────────────────────────────────────────
    PERMANENT_SESSION_LIFETIME = timedelta(hours=24)
    # Secure by default — subclasses must explicitly opt out for local dev.
    SESSION_COOKIE_SECURE   = True
    SESSION_COOKIE_HTTPONLY = True
    SESSION_COOKIE_SAMESITE = 'Lax'

    # ── Mail ────────────────────────────────────────────────────────────────
    # ── Application base URL (used in email links) ─────────────────────────
    APP_BASE_URL         = os.environ.get('APP_BASE_URL', '')
    MAIL_DEFAULT_SENDER  = os.environ.get('MAIL_DEFAULT_SENDER', 'noreply@janitorialqc.local')

    # ── Digest email secret token (used to authenticate cron trigger) ────────
    DIGEST_SECRET        = os.environ.get('DIGEST_SECRET')

    # ── Google Maps (used for GPS map on inspection view) ────────────────────
    GOOGLE_MAPS_API_KEY  = os.environ.get('GOOGLE_MAPS_API_KEY', '')

    MAIL_SERVER   = os.environ.get('MAIL_SERVER')
    MAIL_USERNAME = os.environ.get('MAIL_USERNAME')
    MAIL_PASSWORD = os.environ.get('MAIL_PASSWORD')

    # ── SSL vs STARTTLS selection ────────────────────────────────────────────
    # Port 465 = implicit SSL  → MAIL_USE_SSL=True,  MAIL_USE_TLS=False
    # Port 587 = STARTTLS      → MAIL_USE_SSL=False, MAIL_USE_TLS=True
    # The two flags are mutually exclusive; setting both True breaks Flask-Mail.
    _mail_port    = int(os.environ.get('MAIL_PORT') or 587)
    MAIL_PORT     = _mail_port
    MAIL_USE_SSL  = _mail_port == 465
    MAIL_USE_TLS  = not MAIL_USE_SSL   # STARTTLS only when NOT using implicit SSL


class DevelopmentConfig(Config):
    DEBUG = True
    SQLALCHEMY_ECHO = True
    # Allow HTTP cookies during local development (HTTP, not HTTPS)
    SESSION_COOKIE_SECURE = False


class ProductionConfig(Config):
    DEBUG = False
    # Inherits SESSION_COOKIE_SECURE = True from Config — no override needed.


config = {
    'development': DevelopmentConfig,
    'production':  ProductionConfig,
    'default':     DevelopmentConfig,
}