#!/usr/bin/env python3
"""Concurrency-bounded threaded HTTP server for the Hermes SCM broker."""

from __future__ import annotations

import threading
from http.server import ThreadingHTTPServer

MAX_CONCURRENT_REQUESTS = 2


class BoundedThreadingHTTPServer(ThreadingHTTPServer):
    """Cap active handlers so large Git exchanges cannot exhaust memory."""

    daemon_threads = True
    block_on_close = True
    request_queue_size = 16

    def __init__(self, *args, **kwargs):
        self._slots = threading.BoundedSemaphore(MAX_CONCURRENT_REQUESTS)
        super().__init__(*args, **kwargs)

    def process_request(self, request, client_address) -> None:
        if not self._slots.acquire(blocking=False):
            try:
                request.sendall(
                    b"HTTP/1.1 503 Service Unavailable\r\n"
                    b"Connection: close\r\nContent-Length: 0\r\n\r\n"
                )
            finally:
                self.shutdown_request(request)
            return
        try:
            super().process_request(request, client_address)
        except Exception:
            self._slots.release()
            self.shutdown_request(request)
            raise

    def process_request_thread(self, request, client_address) -> None:
        try:
            super().process_request_thread(request, client_address)
        finally:
            self._slots.release()