#!/usr/bin/env python3
# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0

"""
Assumption tests for KVBM connector's expectations of vLLM interfaces.

These unit tests validate that KVBM's assumptions about vLLM's internal
interfaces remain stable across vLLM releases. They do NOT test functional
correctness of KVBM or vLLM logic, but rather ensure the API contract remains
intact to prevent silent breakage.

Inspired by vLLM's test_lmcache_integration.py approach to interface testing.
"""

import typing
from typing import Any

import pytest

from .common import check_module_available

HAS_VLLM = check_module_available("vllm")

if HAS_VLLM:
    from vllm.config import (  # noqa: E402
        CacheConfig,
        KVTransferConfig,
        ModelConfig,
        ParallelConfig,
        VllmConfig,
    )
    from vllm.lora.request import LoRARequest  # noqa: E402
    from vllm.sampling_params import SamplingParams  # noqa: E402
    from vllm.v1.core.sched.output import (  # noqa: E402
        CachedRequestData,
        NewRequestData,
        SchedulerOutput,
    )
    from vllm.v1.request import Request  # noqa: E402

# Test markers
pytestmark = [
    pytest.mark.kvbm,
    pytest.mark.integration,
    pytest.mark.gpu_0,
    pytest.mark.vllm,
    pytest.mark.nightly,
    pytest.mark.pre_merge,
    pytest.mark.skipif(not HAS_VLLM, reason="requires vllm"),
]


def _get_obj_name(obj: Any) -> str:
    """Get a readable name for an object (class name or repr)."""
    return getattr(obj, "__name__", None) or obj.__class__.__name__


def _check_attr_exists(obj: Any, attr: str) -> str | None:
    """Check that an attribute exists on an object or dataclass.

    Returns error message if check fails, None if check passes.
    """
    obj_name = _get_obj_name(obj)
    # Check __dataclass_fields__ directly - works for both classes and instances,
    # and handles decorated dataclasses (e.g., @config @dataclass)
    dataclass_fields = getattr(obj, "__dataclass_fields__", None)
    if dataclass_fields is not None:
        if attr not in dataclass_fields:
            return f"Dataclass {obj_name} missing field '{attr}'"
    else:
        if not hasattr(obj, attr):
            return f"Object {obj_name} missing attribute '{attr}'"
    return None


def _get_property_return_type(prop: property) -> Any:
    """Extract return type from a property's fget annotations."""
    fget = prop.fget
    if fget is None or not hasattr(fget, "__annotations__"):
        return None
    annotations = fget.__annotations__
    if "return" not in annotations:
        return None
    return_type = annotations["return"]
    # Handle Optional types (Union[X, None]) by extracting the non-None type
    origin = typing.get_origin(return_type)
    if origin is typing.Union:
        args = typing.get_args(return_type)
        # Filter out NoneType to get the actual type
        non_none_args = [arg for arg in args if arg is not type(None)]
        if len(non_none_args) == 1:
            return_type = non_none_args[0]
    return return_type


def _check_instance_of(
    obj: Any, attr: str, value: Any, expected_type: Any
) -> str | None:
    """Check that value matches expected type, handling properties specially.

    Returns error message if check fails, None if check passes.
    """
    prop = type(obj).__dict__.get(attr)

    if isinstance(prop, property):
        return_type = _get_property_return_type(prop)
        if return_type is not None:
            is_match = return_type == expected_type or (
                isinstance(return_type, type) and issubclass(return_type, expected_type)
            )
            if not is_match:
                return f"Property '{attr}' return type {return_type} is not {expected_type}"
            return None

    if not isinstance(value, expected_type):
        return (
            f"Attribute '{attr}' value {type(value)} is not instance of {expected_type}"
        )
    return None


def _get_type_origin(t: Any) -> Any:
    """Extract the origin type from a potentially parameterized generic.

    e.g., list[int] -> list, set[str] -> set, dict[str, Any] -> dict
    """
    origin = getattr(t, "__origin__", None)
    return origin if origin is not None else t


def _check_dataclass_field_type(obj: type, attr: str, expected_type: Any) -> str | None:
    """Check dataclass field type annotation matches expected type.

    Returns error message if check fails, None if check passes.
    """
    field = obj.__dataclass_fields__[attr]
    field_type = field.type

    # Handle generic types (e.g., list[int] -> list, set[str] -> set)
    field_type_origin = _get_type_origin(field_type)
    expected_type_origin = _get_type_origin(expected_type)

    obj_name = _get_obj_name(obj)

    # First check exact match (including parameterized generics)
    if field_type == expected_type:
        return None

    # Then check origin types match (e.g., set[str] vs set[int] both have origin set)
    if field_type_origin == expected_type_origin:
        return None

    # Finally check subclass relationship (only works with actual types, not generics)
    if isinstance(field_type_origin, type) and isinstance(expected_type_origin, type):
        if issubclass(field_type_origin, expected_type_origin):
            return None

    return f"Dataclass {obj_name}.{attr} type {field_type} is not {expected_type}"


def assumes(
    obj: Any, attr: str, is_callable: bool = False, is_instance_of: Any = None
) -> str | None:
    """
    Helper function to validate interface assumptions.

    Checks that an object has the expected attribute with correct type and callability.
    Used to guard against breaking changes in vLLM's internal interfaces.

    Args:
        obj: The object to check
        attr: The attribute name to validate
        is_callable: If True, verify the attribute is callable
        is_instance_of: If provided, verify the attribute is an instance of this type

    Returns:
        Error message if check fails, None if check passes.
    """
    error = _check_attr_exists(obj, attr)
    if error is not None:
        return error

    # For dataclass classes (not instances), fields with default_factory don't exist
    # as class attributes, so check field type annotation instead of getattr
    dataclass_fields = getattr(obj, "__dataclass_fields__", None)
    is_dataclass_class = dataclass_fields is not None and isinstance(obj, type)

    if is_dataclass_class:
        if is_instance_of is not None:
            return _check_dataclass_field_type(obj, attr, is_instance_of)
        # Note: is_callable check not supported for dataclass class fields
        return None

    value = getattr(obj, attr)

    if is_callable:
        if not callable(value):
            return f"Attribute '{attr}' on {_get_obj_name(obj)} is not callable"

    if is_instance_of is not None:
        return _check_instance_of(obj, attr, value, is_instance_of)

    return None


def _assert_interface(
    checks: list[tuple[Any, str] | tuple[Any, str, dict[str, Any]]]
) -> None:
    """Run assumes() for each (obj, attr) or (obj, attr, kwargs); pytest.fail if any fail."""
    errors = []
    for item in checks:
        obj, attr = item[0], item[1]
        kwargs = item[2] if len(item) > 2 else {}
        errors.append(assumes(obj, attr, **kwargs))
    errors = [e for e in errors if e is not None]
    if errors:
        pytest.fail("\n".join(["Interface validation failed:"] + errors))


def test_config_interface():
    _assert_interface(
        [
            (VllmConfig, "model_config"),
            (VllmConfig, "cache_config"),
            (VllmConfig, "parallel_config"),
            (VllmConfig, "kv_transfer_config"),
            (VllmConfig, "kv_events_config"),
            (KVTransferConfig, "kv_role"),
            (KVTransferConfig, "kv_load_failure_policy"),
            (KVTransferConfig, "kv_connector_module_path"),
            (KVTransferConfig, "engine_id"),
            (KVTransferConfig, "kv_connector"),
            (KVTransferConfig, "kv_connector_extra_config"),
            (ModelConfig, "dtype"),
            (ParallelConfig, "world_size"),
            (ParallelConfig, "data_parallel_rank"),
            (CacheConfig, "cache_dtype"),
            (CacheConfig, "block_size"),
            (CacheConfig, "gpu_memory_utilization"),
            (CacheConfig, "enable_prefix_caching"),
        ]
    )


def test_scheduler_output_interface():
    """
    Test SchedulerOutput interface expectations for KVBM vLLM integration.
    Protects against interface changes in vLLM's SchedulerOutput object.
    """
    _assert_interface(
        [
            (SchedulerOutput, "finished_req_ids", {"is_instance_of": set[str]}),
            (
                SchedulerOutput,
                "scheduled_new_reqs",
                {"is_instance_of": list[NewRequestData]},
            ),
            (SchedulerOutput, "num_scheduled_tokens", {"is_instance_of": dict}),
            (SchedulerOutput, "total_num_scheduled_tokens"),
        ]
    )


def test_request_interface():
    """
    Test Request interface expectations for KVBM vLLM integration.
    Protects against interface changes in vLLM's Request object.
    """
    req = Request(
        request_id="test_request",
        prompt_token_ids=[1, 2, 3],
        sampling_params=SamplingParams(max_tokens=10),
        pooling_params=None,
        eos_token_id=100,
        lora_request=LoRARequest(
            lora_name="test_lora", lora_int_id=1, lora_path="test_path"
        ),
        cache_salt="test_salt",
    )

    _assert_interface(
        [
            (req, "request_id", {"is_instance_of": str}),
            (req, "all_token_ids"),  # ConstantList
            (req, "num_tokens", {"is_instance_of": int}),
            (req, "num_computed_tokens", {"is_instance_of": int}),
            (req, "cache_salt", {"is_instance_of": str}),
            (req, "lora_request", {"is_instance_of": LoRARequest}),
            (req, "priority", {"is_instance_of": int}),
            (req, "sampling_params", {"is_instance_of": SamplingParams}),
        ]
    )


def test_new_request_interface():
    """
    Test NewRequestData interface expectations for KVBM vLLM integration.
    Protects against interface changes in vLLM's NewRequestData object.
    """
    _assert_interface(
        [
            (NewRequestData, "req_id", {"is_instance_of": str}),
            (NewRequestData, "block_ids", {"is_instance_of": tuple[list[int], ...]}),
            (
                NewRequestData,
                "prompt_token_ids",
                {"is_instance_of": (list[int] | None)},
            ),
            (NewRequestData, "num_computed_tokens", {"is_instance_of": int}),
        ]
    )


def test_cached_request_interface():
    _assert_interface(
        [
            (CachedRequestData, "resumed_req_ids", {"is_instance_of": set[str]}),
            (CachedRequestData, "req_ids", {"is_instance_of": list[str]}),
            (CachedRequestData, "new_token_ids", {"is_instance_of": list[list[int]]}),
            (
                CachedRequestData,
                "new_block_ids",
                {"is_instance_of": list[tuple[list[int], ...] | None]},
            ),
            (CachedRequestData, "num_computed_tokens", {"is_instance_of": list[int]}),
        ]
    )
