import pytest

from app.rounds.draw import draw_winner, header_hex_to_block_hash


def test_header_hex_to_block_hash_matches_known_mainnet_block():
    # Real PLM mainnet block 477486: header from blockchain.block.header, hash
    # cross-checked against the blockhash reported by blockchain.transaction.get
    # for a tx confirmed in that block.
    header_hex = (
        "0020ed30fbc39ee45200d10214f5107c5f36e7bf753032fd1d3279810c170000000000"
        "009a4ea723f732be4c538f3a2490837dd6560103d73ece606aa7d578a66700447b28875"
        "e6a47a61b1ad8012582"
    )
    known_block_hash = "00000000000008788b55ade13b74d54ceffda9e54315b802411be1ca65064e86"
    assert header_hex_to_block_hash(header_hex) == known_block_hash


def test_draw_winner_is_deterministic_and_within_range():
    participants = ["addrA", "addrB", "addrC"]
    block_hash = "00" * 31 + "05"  # seed = 5, index = 5 % 3 = 2
    assert draw_winner(participants, block_hash) == "addrC"


def test_draw_winner_single_participant_always_wins():
    block_hash = "ff" * 32
    assert draw_winner(["only"], block_hash) == "only"


def test_draw_winner_raises_on_empty_participants():
    with pytest.raises(ValueError):
        draw_winner([], "00" * 32)