Adds config files for the API

pyproject.toml

@@ -28,6 +28,7 @@ pqn = "pqnstack.cli:app"
 
 [project.optional-dependencies]
 webapp = [
+    "dotenv>=0.9.9",
     "fastapi[standard]>=0.115.14",
     "httpx>=0.28.1",
     "pydantic>=2.11.7",

src/pqnstack/app/core/config.py

@@ -1,35 +1,38 @@
 import logging
-from dataclasses import dataclass
-from dataclasses import field
+import os
+import tomllib
+from pathlib import Path
 
+from dotenv import load_dotenv
 from pydantic import BaseModel
+from pydantic import Field
 
 from pqnstack.constants import BellState
 from pqnstack.constants import QKDEncodingBasis
 from pqnstack.pqn.protocols.measurement import MeasurementConfig
 
+load_dotenv()
+
+
 logger = logging.getLogger(__name__)
 
 
-@dataclass
-class CHSHSettings:
+class CHSHSettings(BaseModel):
     # Specifies which half waveplate to use for the CHSH experiment. First value is the provider's name, second is the motor name.
     hwp: tuple[str, str] = ("", "")
     request_hwp: tuple[str, str] = ("", "")
-    measurement_config: MeasurementConfig = field(default_factory=lambda: MeasurementConfig(5))
+    measurement_config: MeasurementConfig = Field(default_factory=lambda: MeasurementConfig(integration_time_s=5))
 
 
-@dataclass
-class QKDSettings:
+class QKDSettings(BaseModel):
     hwp: tuple[str, str] = ("", "")
     request_hwp: tuple[str, str] = ("", "")
     bitstring_length: int = 4
-    discriminating_threshold = 10
-    measurement_config: MeasurementConfig = field(default_factory=lambda: MeasurementConfig(5))
+    discriminating_threshold: int = 10
+    measurement_config: MeasurementConfig = Field(default_factory=lambda: MeasurementConfig(integration_time_s=5))
 
 
-@dataclass
-class Settings:
+class Settings(BaseModel):
     router_name: str
     router_address: str
     router_port: int
@@ -39,11 +42,31 @@ class Settings:
     timetagger: tuple[str, str] | None = None  # Name of the timetagger to use for the CHSH experiment.
 
 
-static_typecheck_msg = "Please set the global 'settings' variable before use."
+def load_settings_from_toml(config_path: str | Path) -> Settings:
+    """Load settings from a TOML configuration file with Pydantic validation."""
+    config_path = Path(config_path)
+
+    with Path.open(config_path, "rb") as f:
+        config_data = tomllib.load(f)
+
+    # Pydantic will handle all validation and type conversion automatically
+    return Settings(**config_data)
 
 
 def get_settings() -> Settings:
-    raise NotImplementedError(static_typecheck_msg)
+    """Load settings from the config file specified in API_CONFIG_PATH environment variable."""
+    config_path = os.getenv("API_CONFIG_PATH")
+
+    if config_path is None:
+        logger.warning("API_CONFIG_PATH environment variable not found, using default value './config.toml'")
+        config_path = "./config.toml"
+
+    config_file = Path(config_path)
+    if not config_file.exists():
+        msg = f"Configuration file not found: {config_file.absolute()} or 'API_CONFIG_PATH' environment variable is not set"
+        raise FileNotFoundError(msg)
+
+    return load_settings_from_toml(config_path)
 
 
 settings = get_settings()

src/pqnstack/pqn/protocols/measurement.py

@@ -1,8 +1,9 @@
 from dataclasses import dataclass
 
+from pydantic import BaseModel
 
-@dataclass
-class MeasurementConfig:
+
+class MeasurementConfig(BaseModel):
     integration_time_s: float
     binwidth_ps: int = 500
     channel1: int = 1