# plugins/traefik/scheduler.py
from __future__ import annotations
import logging
import time
from typing import TYPE_CHECKING

from fablednetmon.core.scheduler import ScheduledTask

if TYPE_CHECKING:
    from quart import Quart

logger = logging.getLogger(__name__)

# Module-level state: previous scrape data for delta computation
_prev_metrics: dict = {}
_prev_time: float = 0.0


def make_scrape_task(app: "Quart") -> ScheduledTask:
    """Return a ScheduledTask that scrapes Traefik metrics on the configured interval."""
    interval = app.config["PLUGINS"]["traefik"]["scrape_interval_seconds"]

    async def scrape() -> None:
        await _do_scrape(app)

    return ScheduledTask(
        name="traefik_scrape",
        coro_factory=scrape,
        interval_seconds=int(interval),
        run_on_startup=True,
    )


async def _do_scrape(app: "Quart") -> None:
    """Fetch Traefik metrics, write to DB, and emit plugin_metrics."""
    global _prev_metrics, _prev_time

    from datetime import datetime, timezone
    from .models import TraefikMetric
    from .scraper import fetch_metrics, compute_router_metrics
    from fablednetmon.core.alerts import record_metric

    metrics_url: str = app.config["PLUGINS"]["traefik"]["metrics_url"]

    try:
        current = await fetch_metrics(metrics_url)
    except Exception:
        logger.exception("Traefik scrape failed (url=%s)", metrics_url)
        return

    now = time.monotonic()
    elapsed = now - _prev_time if _prev_time else 60.0
    router_metrics = compute_router_metrics(current, _prev_metrics or None, elapsed)

    _prev_metrics = current
    _prev_time = now

    if not router_metrics:
        logger.debug("Traefik scrape: no router metrics found")
        return

    scraped_at = datetime.now(timezone.utc)

    async with app.db_sessionmaker() as session:
        async with session.begin():
            for router_name, metrics in router_metrics.items():
                # Write to traefik_metrics history table
                row = TraefikMetric(
                    router_name=router_name,
                    scraped_at=scraped_at,
                    request_rate=metrics["request_rate"],
                    error_rate_4xx_pct=metrics["error_rate_4xx_pct"],
                    error_rate_5xx_pct=metrics["error_rate_5xx_pct"],
                    latency_p50_ms=metrics["latency_p50_ms"],
                    latency_p95_ms=metrics["latency_p95_ms"],
                    latency_p99_ms=metrics["latency_p99_ms"],
                )
                session.add(row)

                # Emit plugin_metrics for alert rules
                for metric_name, value in [
                    ("request_rate", metrics["request_rate"]),
                    ("error_rate_4xx_pct", metrics["error_rate_4xx_pct"]),
                    ("error_rate_5xx_pct", metrics["error_rate_5xx_pct"]),
                    ("latency_p50_ms", metrics["latency_p50_ms"]),
                    ("latency_p95_ms", metrics["latency_p95_ms"]),
                    ("latency_p99_ms", metrics["latency_p99_ms"]),
                ]:
                    await record_metric(
                        session=session,
                        source_module="traefik",
                        resource_name=router_name,
                        metric_name=metric_name,
                        value=value,
                    )

    logger.debug("Traefik scrape: wrote metrics for %d router(s)", len(router_metrics))