import os
import sys

import pytest


REPO_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
CPP_BUILD_DIR = os.path.join(REPO_ROOT, "migration", "protocol_core")

sys.path.insert(0, CPP_BUILD_DIR)

cpp = pytest.importorskip(
    "ble_protocol_core_cpp",
    reason=(
        "compiled pybind11 module missing; build with "
        "`python3 migration/protocol_core/setup.py build_ext --inplace`"
    ),
)


def identity(base):
    return bytes((base + i) & 0xFF for i in range(16))


def snapshot(address, *, mtu=None):
    snap = cpp.ConnectionSnapshot()
    snap.current = cpp.ConnectionId(address)
    snap.local_role = cpp.LocalRole.Peripheral
    snap.negotiated_mtu = mtu
    return snap


def action_types(result):
    return {action.type for action in result.actions}


def test_import_module_succeeds():
    assert cpp.BLEPeerSessionManager is not None
    assert cpp.ConnectionSnapshot is not None


def test_non_16_byte_payload_passes_to_reassembler():
    manager = cpp.BLEPeerSessionManager()
    result = manager.handle_identity_handshake(snapshot("AA:00"), b"abc", 1.0)

    assert result.decision == cpp.InputDecision.PassToReassembler
    assert result.consumed is False


def test_new_16_byte_identity_sets_keys_and_consumes():
    manager = cpp.BLEPeerSessionManager()
    peer_identity = identity(0x10)

    result = manager.handle_identity_handshake(
        snapshot("AA:01"), peer_identity, 2.0
    )

    assert result.decision == cpp.InputDecision.AcceptedNewIdentity
    assert result.consumed is True
    assert result.accepted is True
    assert result.identity_key == "1011121314151617"
    assert result.fragmenter_key == "101112131415161718191a1b1c1d1e1f"
    assert result.peer_identity == peer_identity


def test_static_key_helpers():
    peer_identity = bytes.fromhex("0102030405060708090a0b0c0d0e0f10")

    assert cpp.BLEPeerSessionManager.compute_identity_key(peer_identity) == "0102030405060708"
    assert (
        cpp.BLEPeerSessionManager.compute_fragmenter_key(peer_identity)
        == "0102030405060708090a0b0c0d0e0f10"
    )
    assert cpp.BLEPeerSessionManager.identity_from_payload(peer_identity) == peer_identity


def test_identity_from_payload_rejects_non_16_byte_input():
    with pytest.raises(Exception):
        cpp.BLEPeerSessionManager.identity_from_payload(b"abc")


def test_known_identity_duplicate_same():
    manager = cpp.BLEPeerSessionManager()
    peer_identity = identity(0x20)
    snap = snapshot("AA:02")
    snap.set_known_identity(peer_identity)

    result = manager.handle_identity_handshake(snap, peer_identity, 3.0)

    assert result.decision == cpp.InputDecision.ConsumedDuplicateSameIdentity
    assert result.consumed is True


def test_known_identity_duplicate_mismatch():
    manager = cpp.BLEPeerSessionManager()
    snap = snapshot("AA:03")
    snap.set_known_identity(identity(0x30))

    result = manager.handle_identity_handshake(snap, identity(0x40), 4.0)

    assert result.decision == cpp.InputDecision.ConsumedDuplicateMismatchedIdentity
    assert result.consumed is True
    assert cpp.SessionActionType.Warn in action_types(result)


def test_mtu_provided_is_preserved():
    manager = cpp.BLEPeerSessionManager()
    peer_identity = identity(0x50)

    result = manager.handle_identity_handshake(
        snapshot("AA:04", mtu=185), peer_identity, 5.0
    )

    assert result.mtu == 185
    view = manager.session_by_identity(peer_identity)
    assert view is not None
    assert view.mtu == 185


def test_mtu_missing_falls_back_to_23():
    manager = cpp.BLEPeerSessionManager()

    result = manager.handle_identity_handshake(
        snapshot("AA:05"), identity(0x60), 6.0
    )

    assert result.mtu == 23


def test_duplicate_identity_active_elsewhere_requests_disconnect_current():
    manager = cpp.BLEPeerSessionManager()
    peer_identity = identity(0x70)
    manager.handle_identity_handshake(snapshot("AA:06"), peer_identity, 7.0)

    duplicate = snapshot("AA:07")
    duplicate.existing_address_for_identity = "AA:06"
    duplicate.existing_address_connected = True
    duplicate.existing_address_in_peer_table = True

    result = manager.handle_identity_handshake(duplicate, peer_identity, 8.0)

    assert result.decision == cpp.InputDecision.RejectedDuplicateIdentity
    assert result.should_disconnect_current is True
    assert cpp.SessionActionType.DisconnectCurrentPeer in action_types(result)


def test_pending_identity_timeout_can_be_marked_and_expired():
    manager = cpp.BLEPeerSessionManager(30.0, 45.0)
    first = cpp.ConnectionId("AA:08", 8)
    second = cpp.ConnectionId("AA:09", 9)

    manager.mark_pending_identity(first, 100.0)
    manager.mark_pending_identity(second, 120.0)

    expired = manager.expired_pending_identities(131.0)
    assert len(expired) == 1
    assert expired[0].address == "AA:08"
    assert expired[0].handle == 8


def test_peer_address_update_preserves_identity_and_fragmenter_key():
    manager = cpp.BLEPeerSessionManager()
    peer_identity = identity(0x80)
    first_result = manager.handle_identity_handshake(
        snapshot("AA:0A"), peer_identity, 9.0
    )

    rotated = snapshot("AA:0B")
    rotated.existing_address_for_identity = "AA:0A"
    rotated.identity_has_pending_detach = True

    second_result = manager.handle_identity_handshake(rotated, peer_identity, 10.0)

    assert second_result.decision == cpp.InputDecision.AcceptedNewIdentity
    assert first_result.fragmenter_key == second_result.fragmenter_key
    assert manager.session_by_address("AA:0A") is None
    view = manager.session_by_address("AA:0B")
    assert view is not None
    assert view.identity == peer_identity
    assert view.identity_key == first_result.identity_key