feat: add typed configuration loader with env support

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/config.py

@@ -0,0 +1,53 @@
+"""Application configuration loader.
+
+Reads environment variables (with .env file support) and provides
+a typed, validated Settings object used throughout the application.
+"""
+
+from functools import lru_cache
+from pathlib import Path
+
+from dotenv import load_dotenv
+from pydantic_settings import BaseSettings
+from pydantic_settings import SettingsConfigDict
+
+# Load .env file from project root
+_env_path = Path(__file__).resolve().parent.parent / ".env"
+load_dotenv(_env_path)
+
+
+class Settings(BaseSettings):
+    """Typed application settings loaded from environment variables.
+
+    Attributes:
+        admin_username: Admin login username (from ADMIN_USERNAME env var).
+        admin_password: Admin login password (from ADMIN_PASSWORD env var).
+        app_env: Runtime environment — 'development' or 'production'.
+        app_host: Host address to bind the server to.
+        app_port: Port number for the server.
+        app_log_level: Minimum log level for structlog output.
+        database_url: SQLite connection string.
+    """
+
+    admin_username: str
+    admin_password: str
+    app_env: str = "development"
+    app_host: str = "0.0.0.0"
+    app_port: int = 8000
+    app_log_level: str = "info"
+    database_url: str = "sqlite:///data/sneakyswole.db"
+
+    model_config = SettingsConfigDict(
+        env_file=".env",
+        env_file_encoding="utf-8",
+    )
+
+
+@lru_cache(maxsize=1)
+def get_settings() -> Settings:
+    """Return a cached Settings instance (singleton pattern).
+
+    Returns:
+        The application Settings object.
+    """
+    return Settings()

tests/test_config.py

@@ -0,0 +1,43 @@
+"""Tests for the application configuration loader."""
+
+import os
+from unittest.mock import patch
+
+from app.config import Settings, get_settings
+
+
+class TestSettings:
+    """Tests for the Settings configuration class."""
+
+    def test_settings_loads_defaults(self) -> None:
+        """Settings should have sensible defaults for all fields."""
+        with patch.dict(os.environ, {
+            "ADMIN_USERNAME": "testadmin",
+            "ADMIN_PASSWORD": "testpass123",
+        }, clear=False):
+            settings = Settings()
+            assert settings.admin_username == "testadmin"
+            assert settings.admin_password == "testpass123"
+            assert settings.app_env == "development"
+            assert settings.app_host == "0.0.0.0"
+            assert settings.app_port == 8000
+            assert settings.database_url == "sqlite:///data/sneakyswole.db"
+
+    def test_settings_requires_admin_username(self) -> None:
+        """Settings should require ADMIN_USERNAME to be set."""
+        with patch.dict(os.environ, {"ADMIN_PASSWORD": "testpass"}, clear=True):
+            try:
+                Settings()
+                assert False, "Should have raised an error"
+            except Exception:
+                pass
+
+    def test_get_settings_returns_singleton(self) -> None:
+        """get_settings should return the same instance on repeated calls."""
+        with patch.dict(os.environ, {
+            "ADMIN_USERNAME": "admin",
+            "ADMIN_PASSWORD": "pass",
+        }, clear=False):
+            s1 = get_settings()
+            s2 = get_settings()
+            assert s1 is s2