import sys
import pathlib

# Ensure repository root is on sys.path so tests can import the package
sys.path.insert(0, str(pathlib.Path(__file__).resolve().parents[1]))

from cosmic_ledger.delta import DeltaLog, verify_delta_block


def test_export_and_verify_delta_block_with_signature():
    dl = DeltaLog()
    # add a few payloads
    for i in range(4):
        dl.add_entry({"v": i})

    key = b'unique-test-key-xyz'
    block = dl.export_delta_block(since_index=0, signer_key=key)

    assert "root" in block
    assert "digests" in block
    assert "aggregated_sig" in block
    assert block["aggregated_sig"] is not None

    # verify should succeed with correct key
    assert verify_delta_block(block, signer_key=key)


def test_verify_delta_block_tamper_detection():
    dl = DeltaLog()
    for i in range(3):
        dl.add_entry({"v": i})

    key = b'another-key-123'
    block = dl.export_delta_block(since_index=0, signer_key=key)

    # tamper with a digest
    if block["digests"]:
        block["digests"][0] = ("0" if block["digests"][0][0] != "0" else "1") + block["digests"][0][1:]

    assert not verify_delta_block(block, signer_key=key)