"""Bounded structured diagnostics for the two game-window supervisors."""

from __future__ import annotations

from collections import Counter
from collections.abc import Callable, Mapping, Sequence
import json
import math
import os
import re
import sys
import time


WINDOW_DIAGNOSTICS_ENV = "PTLINUX_WINDOW_DIAGNOSTICS"
WINDOW_DIAGNOSTICS_SESSION_ENV = "PTLINUX_WINDOW_DIAGNOSTICS_SESSION"
WINDOW_DIAGNOSTIC_PREFIX = "PTLINUX_WINDOW_DIAGNOSTIC "
WINDOW_DIAGNOSTIC_EVENT_LIMIT = 12
WINDOW_DIAGNOSTIC_LINE_LIMIT = 4096
WINDOW_DIAGNOSTIC_COMPONENTS = frozenset({"game_window", "gamescope_host"})
_DIAGNOSTIC_NAME_PATTERN = re.compile(r"[a-z][a-z0-9_]{0,63}\Z")
_SESSION_ID_PATTERN = re.compile(r"[0-9a-f]{32}\Z")
_TRUE_VALUES = frozenset({"1", "true", "yes"})
_MAX_DETAILS_DEPTH = 4
_MAX_DETAILS_ITEMS = 48
_MAX_STRING_CHARACTERS = 256


def window_diagnostics_enabled(
	environment: Mapping[str, str] | None = None,
) -> bool:
	env = os.environ if environment is None else environment
	return env.get(WINDOW_DIAGNOSTICS_ENV, "").strip().casefold() in _TRUE_VALUES


class WindowDiagnosticRecorder:
	"""Emit a few samples while retaining aggregate counts for session shutdown."""

	def __init__(
		self,
		component: str,
		*,
		environment: Mapping[str, str] | None = None,
		monotonic: Callable[[], float] | None = None,
	) -> None:
		if component not in WINDOW_DIAGNOSTIC_COMPONENTS:
			raise ValueError(f"unsupported window diagnostic component: {component}")
		env = os.environ if environment is None else environment
		session_id = env.get(WINDOW_DIAGNOSTICS_SESSION_ENV, "").strip().casefold()
		self.component = component
		self.enabled = window_diagnostics_enabled(env)
		self.session_id = (
			session_id if _SESSION_ID_PATTERN.fullmatch(session_id) is not None else None
		)
		self._monotonic = monotonic or time.monotonic
		self._started_at = self._monotonic()
		self._counts: Counter[str] = Counter()
		self._transitions: dict[str, object] = {}
		self._sequence = 0
		self._emitted = 0
		self._closed = False

	@property
	def accepts_samples(self) -> bool:
		return (
			self.enabled
			and not self._closed
			and self._emitted < WINDOW_DIAGNOSTIC_EVENT_LIMIT
		)

	def record(self, diagnostic: str, **details: object) -> None:
		if self._closed or _DIAGNOSTIC_NAME_PATTERN.fullmatch(diagnostic) is None:
			return
		self._sequence += 1
		self._counts[diagnostic] += 1
		if not self.enabled or self._emitted >= WINDOW_DIAGNOSTIC_EVENT_LIMIT:
			return
		self._emitted += 1
		self._emit(diagnostic, self._sequence, details)

	def transition(
		self,
		key: str,
		value: object,
		diagnostic: str,
		**details: object,
	) -> None:
		"""Record one diagnostic only when the observed state changes."""

		if self._closed or self._transitions.get(key, object()) == value:
			return
		self._transitions[key] = value
		self.record(diagnostic, **details)

	def close(self, **details: object) -> None:
		if self._closed:
			return
		self._closed = True
		if not self.enabled:
			return
		summary = {
			**details,
			"counts": dict(sorted(self._counts.items())),
			"sampled_events": self._emitted,
			"suppressed_events": max(0, self._sequence - self._emitted),
		}
		self._emit("session_summary", self._sequence + 1, summary)

	def _emit(
		self,
		diagnostic: str,
		sequence: int,
		details: Mapping[str, object],
	) -> None:
		payload: dict[str, object] = {
			"schema": 1,
			"component": self.component,
			"diagnostic": diagnostic,
			"sequence": sequence,
			"elapsed_ms": max(0, round((self._monotonic() - self._started_at) * 1000)),
			"details": _bounded_value(details, depth=0),
		}
		if self.session_id is not None:
			payload["session_id"] = self.session_id
		try:
			encoded = json.dumps(
				payload,
				sort_keys=True,
				separators=(",", ":"),
				ensure_ascii=True,
			)
			if len(encoded.encode("utf-8")) > WINDOW_DIAGNOSTIC_LINE_LIMIT:
				payload["details"] = {"payload_truncated": True}
				encoded = json.dumps(
					payload,
					sort_keys=True,
					separators=(",", ":"),
					ensure_ascii=True,
				)
			print(
				f"{WINDOW_DIAGNOSTIC_PREFIX}{encoded}",
				file=sys.stderr,
				flush=True,
			)
		except (OSError, TypeError, ValueError):
			return


def parse_window_diagnostic(line: str) -> dict[str, object] | None:
	"""Parse only launcher-generated, bounded window diagnostic records."""

	marker_index = line.find(WINDOW_DIAGNOSTIC_PREFIX)
	if marker_index < 0:
		return None
	encoded = line[marker_index + len(WINDOW_DIAGNOSTIC_PREFIX):].strip()
	if not encoded or len(encoded.encode("utf-8")) > WINDOW_DIAGNOSTIC_LINE_LIMIT:
		return None
	try:
		payload = json.loads(encoded)
	except (json.JSONDecodeError, UnicodeError):
		return None
	if not isinstance(payload, dict) or payload.get("schema") != 1:
		return None
	component = payload.get("component")
	diagnostic = payload.get("diagnostic")
	sequence = payload.get("sequence")
	elapsed_ms = payload.get("elapsed_ms")
	details = payload.get("details")
	session_id = payload.get("session_id")
	if (
		not isinstance(component, str)
		or component not in WINDOW_DIAGNOSTIC_COMPONENTS
		or not isinstance(diagnostic, str)
		or _DIAGNOSTIC_NAME_PATTERN.fullmatch(diagnostic) is None
		or not isinstance(sequence, int)
		or isinstance(sequence, bool)
		or sequence < 1
		or not isinstance(elapsed_ms, int)
		or isinstance(elapsed_ms, bool)
		or elapsed_ms < 0
		or not isinstance(details, dict)
		or (
			session_id is not None
			and (
				not isinstance(session_id, str)
				or _SESSION_ID_PATTERN.fullmatch(session_id) is None
			)
		)
	):
		return None
	return {
		"schema": 1,
		"component": component,
		"diagnostic": diagnostic,
		"sequence": sequence,
		"elapsed_ms": elapsed_ms,
		"details": _bounded_value(details, depth=0),
		**({"session_id": session_id} if isinstance(session_id, str) else {}),
	}


def _bounded_value(value: object, *, depth: int) -> object:
	if depth >= _MAX_DETAILS_DEPTH:
		return "<max-depth>"
	if value is None or isinstance(value, (bool, int)):
		return value
	if isinstance(value, float):
		return round(value, 3) if math.isfinite(value) else None
	if isinstance(value, str):
		return value[:_MAX_STRING_CHARACTERS]
	if isinstance(value, Mapping):
		result: dict[str, object] = {}
		for index, (raw_key, item) in enumerate(value.items()):
			if index >= _MAX_DETAILS_ITEMS:
				result["_truncated"] = True
				break
			key = str(raw_key)[:64]
			result[key] = _bounded_value(item, depth=depth + 1)
		return result
	if isinstance(value, Sequence) and not isinstance(value, (bytes, bytearray)):
		items = list(value[:_MAX_DETAILS_ITEMS])
		return [_bounded_value(item, depth=depth + 1) for item in items]
	return f"<{type(value).__name__}>"