"""Статистика использования API (#17): число запросов, их время и время, которое был открыт браузер."""
from dataclasses import dataclass, field
from datetime import datetime, timedelta

from sqlalchemy import select

from db.engine import Database
from db.models import Client, Request, Window, utcnow


@dataclass
class ClientUsage:
	client_id: int | None
	name: str
	requests: int = 0
	ok: int = 0
	# по code: challenge_failed, action_failed, request_failed; failed — задачу не выполнили
	errors: dict[str, int] = field(default_factory=dict)
	durations_ms: list[int] = field(default_factory=list)
	windows: int = 0
	browser_seconds: float = 0.0

	@property
	def avg_ms(self) -> int | None:
		return int(sum(self.durations_ms) / len(self.durations_ms)) if self.durations_ms else None

	@property
	def p95_ms(self) -> int | None:
		if not self.durations_ms:
			return None
		ordered = sorted(self.durations_ms)
		return ordered[min(len(ordered) - 1, int(len(ordered) * 0.95))]


def _aware(dt: datetime) -> datetime:
	# sqlite отдаёт время без зоны
	return dt if dt.tzinfo else dt.replace(tzinfo=utcnow().tzinfo)


async def usage(db: Database, since: datetime) -> list[ClientUsage]:
	"""По клиентам за период: запросы, начатые после since, и время окон в пределах периода."""
	now = utcnow()
	async with db.session() as session:
		names = {c.id: c.name for c in await session.scalars(select(Client))}
		requests = list(await session.scalars(select(Request).where(Request.started_at >= since)))
		windows = list(await session.scalars(
			select(Window).where((Window.closed_at.is_(None)) | (Window.closed_at >= since))
		))

	result: dict[int | None, ClientUsage] = {}

	def entry(client_id):
		return result.setdefault(client_id, ClientUsage(client_id, names.get(client_id, "—")))

	for r in requests:
		u = entry(r.client_id)
		u.requests += 1
		if r.status == "ok":
			u.ok += 1
		elif r.finished_at is not None:
			key = r.code or r.status or "unknown"
			u.errors[key] = u.errors.get(key, 0) + 1
		if r.duration_ms is not None:
			u.durations_ms.append(r.duration_ms)

	for w in windows:
		u = entry(w.client_id)
		u.windows += 1
		start = max(_aware(w.started_at), since)
		end = _aware(w.closed_at) if w.closed_at else now
		u.browser_seconds += max(0.0, (end - start).total_seconds())

	return sorted(result.values(), key=lambda u: -u.requests)


def since_days(days: float) -> datetime:
	return utcnow() - timedelta(days=days)