"""TDD — build_presign_payload: client-side Step 1 of the mpack push protocol.

PS-1  Given known bytes, mpack_key is "sha256:" + sha256(bytes).hexdigest().
PS-2  size_bytes equals len(mpack_bytes).
PS-3  Empty bytes produce a valid (non-empty) mpack_key and size_bytes == 0.
PS-4  Two calls with identical bytes produce identical payloads (deterministic).
PS-5  Two calls with different bytes produce different mpack_keys.
"""
from __future__ import annotations

from muse.core.mpack import build_presign_payload
from muse.core.types import blob_id


def test_ps1_mpack_key_is_sha256_prefixed() -> None:
    data = b"hello mpack"
    payload = build_presign_payload(data)
    assert payload["mpack_key"] == blob_id(data)


def test_ps2_size_bytes_matches_len() -> None:
    data = b"x" * 1234
    payload = build_presign_payload(data)
    assert payload["size_bytes"] == 1234


def test_ps3_empty_bytes() -> None:
    payload = build_presign_payload(b"")
    assert payload["mpack_key"].startswith("sha256:")
    assert len(payload["mpack_key"]) == len("sha256:") + 64
    assert payload["size_bytes"] == 0


def test_ps4_deterministic() -> None:
    data = b"same bytes every time"
    assert build_presign_payload(data) == build_presign_payload(data)


def test_ps5_different_bytes_different_key() -> None:
    a = build_presign_payload(b"aaaa")
    b = build_presign_payload(b"bbbb")
    assert a["mpack_key"] != b["mpack_key"]