"""Per-agent iteration budget — thread-safe consume/refund counter.

Each ``AIAgent`` (parent or subagent) holds its own :class:`IterationBudget`:
the parent's cap is ``max_iterations`` (default 500), each subagent's is
``delegation.max_iterations`` (default 50), so total iterations across parent
+ subagents can exceed the parent's cap. ``run_agent`` re-exports the class so
``from run_agent import IterationBudget`` keeps working.
"""

from __future__ import annotations

import threading


class IterationBudget:
    """Thread-safe iteration counter. ``execute_code`` (programmatic tool
    calling) iterations are refunded via :meth:`refund` so they don't eat
    into the budget."""

    def __init__(self, max_total: int):
        self.max_total = max_total
        self._used = 0
        self._lock = threading.Lock()

    def consume(self) -> bool:
        """Try to consume one iteration.  Returns True if allowed."""
        with self._lock:
            if self._used >= self.max_total:
                return False
            self._used += 1
            return True

    def refund(self) -> None:
        """Give back one iteration (e.g. for execute_code turns)."""
        with self._lock:
            if self._used > 0:
                self._used -= 1

    @property
    def used(self) -> int:
        with self._lock:
            return self._used

    @property
    def remaining(self) -> int:
        with self._lock:
            return max(0, self.max_total - self._used)


__all__ = ["IterationBudget"]