"""
Process-wide concurrency limits for Streamlit single-process deployment.

These limits reduce tail latency and avoid a single user saturating network/CPU
and impacting other concurrent sessions.
"""

from __future__ import annotations

import os
import threading
from contextlib import contextmanager
from typing import Iterator


def _env_int(name: str, default: int) -> int:
    try:
        return max(1, int(os.getenv(name, str(default))))
    except Exception:
        return default


MAX_CONCURRENT_IMAGE = _env_int("MAX_CONCURRENT_IMAGE", 6)
MAX_CONCURRENT_VIDEO = _env_int("MAX_CONCURRENT_VIDEO", 1)

_image_sem = threading.BoundedSemaphore(MAX_CONCURRENT_IMAGE)
_video_sem = threading.BoundedSemaphore(MAX_CONCURRENT_VIDEO)


@contextmanager
def acquire_image(blocking: bool = True) -> Iterator[bool]:
    ok = _image_sem.acquire(blocking=blocking)
    try:
        yield ok
    finally:
        if ok:
            _image_sem.release()


@contextmanager
def acquire_video(blocking: bool = True) -> Iterator[bool]:
    ok = _video_sem.acquire(blocking=blocking)
    try:
        yield ok
    finally:
        if ok:
            _video_sem.release()