"""
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()