#!/usr/bin/env python3
"""Deterministic oracle for HTTP Age / local freshness-cap algebra.
No binary execution, no claim of measured throughput. Run with Python 3 only.
"""
import json
import random
from pathlib import Path


def old_freshness(max_age, header_age, apparent_age, response_delay, local_limit):
    age = max(header_age, apparent_age) + response_delay
    return max(0, min(max_age, local_limit) - age)


def new_freshness(max_age, header_age, apparent_age, response_delay, local_limit):
    # RFC 9111 corrected_initial_age = max(apparent_age, age_value + response_delay)
    age = max(apparent_age, header_age + response_delay)
    lifetime = min(max_age, age + local_limit)
    return max(0, lifetime - age)


def run():
    cases = [
        ('user_cdn_example', 2_592_000, 1_553_483, 0, 0, 86_400),
        ('user_cdn_example_7d', 2_592_000, 1_553_483, 0, 0, 604_800),
        ('origin_nearly_stale', 2_592_000, 2_591_990, 0, 0, 86_400),
        ('origin_stale', 2_592_000, 2_592_010, 0, 0, 86_400),
        ('normal_small', 3_600, 0, 0, 0, 86_400),
        ('date_is_older', 3_600, 10, 600, 2, 86_400),
        ('rfc_delay_case', 3_600, 3, 10, 2, 86_400),
    ]
    report = {'reference': 'RFC 9111 4.2.3 (Age) and 4.2.1 (freshness lifetime)',
              'kind': 'algebra simulation; not RustProxy RPS benchmark',
              'scenarios': [], 'randomized_checks': 0, 'false_miss_cases_old': 0}
    for name, max_age, age, apparent, delay, local in cases:
        old = old_freshness(max_age, age, apparent, delay, local)
        new = new_freshness(max_age, age, apparent, delay, local)
        report['scenarios'].append({'scenario': name, 'origin_max_age_seconds': max_age,
                                    'received_age_seconds': age, 'apparent_age_seconds': apparent,
                                    'response_delay_seconds': delay, 'local_max_ttl_seconds': local,
                                    'old_freshness_seconds': old, 'new_freshness_seconds': new})
    rng = random.Random(0x3400)
    for _ in range(100_000):
        origin = rng.randrange(0, 1 << 24)
        header_age = rng.randrange(0, 1 << 24)
        apparent = rng.randrange(0, 1 << 24)
        delay = rng.randrange(0, 300)
        local = rng.randrange(0, 604_801)
        corrected_age = max(apparent, header_age + delay)
        new = new_freshness(origin, header_age, apparent, delay, local)
        expected = min(max(0, origin - corrected_age), local)
        assert new == expected, (origin, header_age, apparent, delay, local, new, expected)
        assert new <= local and new <= max(0, origin - corrected_age)
        old = old_freshness(origin, header_age, apparent, delay, local)
        report['false_miss_cases_old'] += old == 0 < new
        report['randomized_checks'] += 1
    return report


if __name__ == '__main__':
    report = run()
    print(json.dumps(report, ensure_ascii=False, indent=2))