docs: add project description and server setup instructions to README

server/app/config.py

@@ -0,0 +1,99 @@
+"""
+Demeter Server — Configuration
+
+Loads settings from environment variables and the device registry
+from config/devices.yaml.
+"""
+
+from __future__ import annotations
+
+import logging
+from pathlib import Path
+from typing import Optional
+
+import yaml
+from pydantic import BaseModel, Field
+from pydantic_settings import BaseSettings
+
+logger = logging.getLogger(__name__)
+
+# ── Paths ──
+
+BASE_DIR = Path(__file__).resolve().parent.parent
+CONFIG_DIR = BASE_DIR / "config"
+TEMPLATES_DIR = BASE_DIR / "templates"
+
+
+# ── Device Config Models ──
+
+class ResourceConfig(BaseModel):
+    """A single CoAP resource on a device."""
+    uri: str
+    name: str
+    type: str = "periodic"  # "periodic" or "event"
+
+
+class DeviceConfig(BaseModel):
+    """A single ESP sensor node."""
+    id: str
+    name: str
+    ip: str
+    port: int = 5683
+    enabled: bool = True
+    resources: list[ResourceConfig] = Field(default_factory=list)
+
+
+class DevicesConfig(BaseModel):
+    """Top-level device registry loaded from YAML."""
+    devices: list[DeviceConfig] = Field(default_factory=list)
+
+
+# ── Application Settings ──
+
+class Settings(BaseSettings):
+    """Server settings loaded from environment variables."""
+
+    # FastAPI
+    app_title: str = "Demeter IoT Server"
+    app_version: str = "0.1.0"
+    debug: bool = False
+
+    # Server
+    host: str = "0.0.0.0"
+    port: int = 8000
+
+    # Loki
+    loki_url: Optional[str] = None  # e.g. "http://localhost:3100/loki/api/v1/push"
+
+    # CoAP
+    coap_request_timeout: float = 10.0  # seconds
+    coap_reconnect_base: float = 5.0    # base backoff seconds
+    coap_reconnect_max: float = 60.0    # max backoff seconds
+
+    # Device config path
+    devices_config_path: str = str(CONFIG_DIR / "devices.yaml")
+
+    model_config = {"env_prefix": "DEMETER_", "env_file": ".env"}
+
+
+def load_devices_config(path: str | Path | None = None) -> DevicesConfig:
+    """Load and validate the device registry from YAML."""
+    if path is None:
+        path = CONFIG_DIR / "devices.yaml"
+    path = Path(path)
+
+    if not path.exists():
+        logger.warning("Device config not found at %s, using empty registry", path)
+        return DevicesConfig(devices=[])
+
+    with open(path) as f:
+        raw = yaml.safe_load(f)
+
+    if raw is None:
+        return DevicesConfig(devices=[])
+
+    return DevicesConfig.model_validate(raw)
+
+
+# Singleton settings instance
+settings = Settings()