"""Границы PHY, расчёт полезной скорости и отдельный компактный заголовок."""

from __future__ import annotations

import pytest

from protocol.video003_compact_header import HEADER_SIZE as COMPACT_SIZE
from protocol.video003_compact_header import decode, encode
from protocol.video_stream_transport import (
    HEADER_SIZE as CURRENT_SIZE, FrameType, VideoFragment, VideoTransportError,
)
from tools.video003_design import estimate, run


def test_current_packet_limit_and_exact_max_video_fragment() -> None:
    result = run()
    assert result["max_full_phy_packet_bytes"] == 1024
    assert result["current_fixed_lab_generator_phy_payload_bytes"] == 256
    assert result["packet_header_bytes"] == 8
    assert result["packet_crc_bytes"] == 4
    assert result["video_header_bytes"] == 17
    assert result["max_format_phy_payload_bytes"] == 1012
    assert result["max_format_video_fragment_bytes"] == 995
    assert len(result["rows"]) == 7 * 4 * 5
    assert sorted(set(row["gap_ms"] for row in result["rows"])) == [0, 0.5, 1, 2, 5]
    with pytest.raises(ValueError, match="1024"):
        estimate("QPSK", 500_000, "3/4", 1013, 0)


def test_maximum_does_not_reach_600k_even_without_video_header() -> None:
    result = run()
    best = result["best_calculated"]
    assert best["modulation"] == "QPSK"
    assert best["symbol_rate"] == 500_000
    assert best["fec_rate"] == "3/4"
    assert best["full_packet_bytes"] == 1024
    assert best["gap_ms"] == 0
    assert best["useful_video_rate_bps"] == pytest.approx(574_148.8747836122)
    assert best["useful_video_rate_bps"] < 600_000
    no_video_header = estimate("QPSK", 500_000, "3/4", 1012, 0, video_header_bytes=0)
    assert no_video_header.useful_video_rate_bps < 600_000


def test_compact_header_roundtrip_preserves_identity_age_and_reassembly_fields() -> None:
    assert CURRENT_SIZE == 17 and COMPACT_SIZE == 13
    fragment = VideoFragment(0x56303032, 0xFFFFFFFE, 255, 256,
                             FrameType.KEYFRAME, 299, b"video")
    wire = encode(fragment, 1012)
    assert len(wire) == COMPACT_SIZE + len(fragment.data)
    assert decode(wire, 1012) == fragment
    assert (CURRENT_SIZE - COMPACT_SIZE) / CURRENT_SIZE == pytest.approx(4 / 17)
    with pytest.raises(VideoTransportError):
        decode(bytes([0x12]) + wire[1:], 1012)
    with pytest.raises(VideoTransportError):
        decode(wire[:9], 1012)


def test_compact_header_does_not_make_600k_reachable() -> None:
    row = estimate("QPSK", 500_000, "3/4", 1012, 0,
                   video_header_bytes=COMPACT_SIZE)
    assert row.video_fragment_bytes == 999
    assert row.useful_video_rate_bps == pytest.approx(576_457.0109636468)
    assert row.useful_video_rate_bps < 600_000