"""Small request-local timings; no board payloads or external tracing dependency."""
from contextlib import contextmanager
import json
import os
from threading import Lock
from time import perf_counter
from uuid import uuid4

class MoveTrace:
  def __init__(self, game_id, turn):
    self.id = uuid4().hex
    self.game_id = game_id
    self.turn = turn
    self.started = perf_counter()
    self._lock = Lock()
    self._fields = {}

  def set(self, **fields):
    with self._lock:
      self._fields.update(fields)

  @contextmanager
  def stage(self, name):
    started = perf_counter()
    try:
      yield
    finally:
      self.set(**{name + '_ms': round((perf_counter() - started) * 1000, 3)})

  def snapshot(self):
    with self._lock:
      return {'trace_id': self.id, **self._fields}

  def log(self, logger):
    fields = self.snapshot()
    # Every timeout/slow request, plus deterministic sampling of normal moves.
    try:
      sample = max(0, int(os.getenv('MOVE_TRACE_SAMPLE_EVERY', '100')))
      slow_ms = max(0, float(os.getenv('MOVE_TRACE_SLOW_MS', '300')))
    except ValueError:
      sample, slow_ms = 100, 300
    slow_stage = any(value >= slow_ms for key, value in fields.items()
                     if key.endswith('_ms') and isinstance(value, (int, float)))
    if not (fields.get('timed_out') or fields.get('metrics_publish_failed') or slow_stage
            or (sample and int(self.id[:8], 16) % sample == 0)):
      return
    logger.info('move_trace %s', json.dumps({
      'game_id': self.game_id, 'turn': self.turn, **fields,
    }, separators=(',', ':')))