"""Fixed-window per-IP rate limiting for the agent-facing routes.

One implementation, several budgets. The bootstrap installer routes and the
enrollment route are both unauthenticated by design - a PC with no agent has
neither a credential nor a user session - so the only thing standing between
them and a loop is a limiter. Each caller gets its own budget name so the two
surfaces cannot spend each other's allowance.

Same shape and same cache extension as the login limiter in
shopdb.core.api.auth. Under the default SimpleCache the counter is per-process,
so with N gunicorn workers the effective budget is N times the configured
maximum; that is defence in depth rather than a hard quota, and a shared cache
backend (Redis/memcached) tightens it to a true global budget.
"""

import time

from flask import current_app, request

from shopdb.api import cache, client_ip, error_response


def caller_ip():
    return client_ip(request) or 'unknown'


def ratelimited(budget, configprefix, defaultmax, defaultwindow):
    """True when this caller is over budget for the current window.

    budget        cache key namespace, e.g. 'endpointenrollratelimit'
    configprefix  config key stem, e.g. 'ENDPOINTS_ENROLL_RATELIMIT'; reads
                  <prefix>_ENABLED, <prefix>_MAX and <prefix>_WINDOW_SECONDS
    """
    if not current_app.config.get(configprefix + '_ENABLED', True):
        return False
    window = current_app.config.get(configprefix + '_WINDOW_SECONDS',
                                    defaultwindow)
    maxhits = current_app.config.get(configprefix + '_MAX', defaultmax)
    # Time bucket makes this a fixed window: the key rolls over at each window
    # boundary, so a per-hit set() cannot turn it into a sliding window.
    bucket = int(time.time() // window) if window > 0 else 0
    key = '{0}:{1}:{2}'.format(budget, caller_ip(), bucket)
    count = cache.get(key) or 0
    if count >= maxhits:
        return True
    cache.set(key, count + 1, timeout=window)
    return False


def rate_limit_response(message):
    """The standard 429 shape every limiter in the product answers with."""
    return error_response('RATE_LIMITED', message, http_code=429)