import base64
import os
import time
from typing import Dict, Any, List, Tuple


def b64(s: bytes) -> str:
    return base64.b64encode(s).decode("ascii")


def ub64(s: str) -> bytes:
    return base64.b64decode(s.encode("ascii"))


def make_random_bytes(size: int) -> bytes:
    return os.urandom(size)


def monotonic_ms() -> int:
    return int(time.monotonic() * 1000)


def assert_dict_has_keys(d: Dict[str, Any], keys: List[str]) -> None:
    missing = [k for k in keys if k not in d]
    assert not missing, f"Missing keys: {missing}; present: {list(d.keys())}"


def chunk_bytes(data: bytes, chunk_size: int) -> List[bytes]:
    out: List[bytes] = []
    for i in range(0, len(data), chunk_size):
        out.append(data[i:i+chunk_size])
    if len(data) == 0:
        out.append(b"")
    return out


def approx_eq_bytes(a: bytes, b: bytes, msg: str = "") -> None:
    assert a == b, msg or f"bytes mismatch: len(a)={len(a)} len(b)={len(b)}"


def measure_throughput(op_name: str, size_bytes: int, elapsed_s: float) -> Tuple[float, str]:
    if elapsed_s <= 0:
        return float("inf"), f"{op_name}: {size_bytes} bytes in {elapsed_s:.6f}s = inf B/s"
    thr = size_bytes / elapsed_s
    return thr, f"{op_name}: {size_bytes} bytes in {elapsed_s:.6f}s = {thr:.2f} B/s"