"""
Background health-checker for registered feature services.

Polls each service's /health endpoint every POLL_INTERVAL seconds and stores
the result in an in-memory dict.  The REST layer reads from that dict — no DB,
no blocking calls on the request path.
"""
import asyncio
import logging
from dataclasses import dataclass, field

import httpx

logger = logging.getLogger(__name__)

POLL_INTERVAL = 30  # seconds


@dataclass
class ServiceDefinition:
    id: str
    name: str
    description: str
    internal_url: str          # e.g. http://doc-service:8001
    health_path: str = "/health"
    app_path: str = ""         # frontend route; empty = no open button
    settings_path: str = ""    # frontend admin-settings route


# ── Registry ──────────────────────────────────────────────────────────────────
# Add new services here.  The internal_url is filled in at startup from settings.

_REGISTRY: list[ServiceDefinition] = []

# id → True/False/None (None = not yet checked)
_health: dict[str, bool | None] = {}


def register_services(doc_service_url: str, ai_service_url: str) -> None:
    """Called once during app startup to populate the registry from config."""
    global _REGISTRY, _health

    _REGISTRY = [
        ServiceDefinition(
            id="doc-service",
            name="Documents",
            description="Upload PDF files, extract data, and organise them with categories.",
            internal_url=doc_service_url,
            health_path="/health",
            app_path="/apps/documents",
            settings_path="/apps/documents/settings/admin",
        ),
        ServiceDefinition(
            id="ai-service",
            name="AI Service",
            description="Shared AI provider for all features. Configure model, credentials, and connection.",
            internal_url=ai_service_url,
            health_path="/health",
            app_path="",
            settings_path="/apps/ai/settings/admin",
        ),
    ]

    _health = {svc.id: None for svc in _REGISTRY}


# ── Health check logic ────────────────────────────────────────────────────────


async def _check_service(svc: ServiceDefinition) -> None:
    url = f"{svc.internal_url}{svc.health_path}"
    try:
        async with httpx.AsyncClient(timeout=5.0) as client:
            resp = await client.get(url)
        _health[svc.id] = resp.status_code == 200
    except Exception:
        _health[svc.id] = False


async def check_all() -> None:
    """Run health checks for all registered services concurrently."""
    await asyncio.gather(*[_check_service(svc) for svc in _REGISTRY])


async def health_check_loop() -> None:
    """Runs forever; polls every POLL_INTERVAL seconds."""
    while True:
        await check_all()
        await asyncio.sleep(POLL_INTERVAL)


# ── Public read API ───────────────────────────────────────────────────────────


def get_all_statuses() -> list[dict]:
    """Return the current health snapshot for all registered services."""
    return [
        {
            "id": svc.id,
            "name": svc.name,
            "description": svc.description,
            "app_path": svc.app_path,
            "settings_path": svc.settings_path,
            # None means not yet checked; treat as unhealthy for the UI
            "healthy": bool(_health.get(svc.id)),
        }
        for svc in _REGISTRY
    ]