# The purpose of this test is to check that we have implementation parity between
# a Python `torch.nn.functional` function and its corresponding C++ `torch::nn::functional`
# function. Concretely, this test does the following:
#
# 1. Get a test params dict from common_nn.py, run forward pass on the Python functional
# created using the test params.
#
# 2. Serialize the Python functional's forward input arguments, deserialize them
# in C++ and use them as input for the C++ functional's forward pass.
#
# 3. Run the forward pass on the C++ functional, and serialize the C++ functional's
# forward output.
#
# 4. Compare Python/C++ functional's forward output. If they are the same, then we
# have implementation parity between Python/C++ module.

import tempfile
from string import Template
import re
import pprint
import os

import torch
from cpp_api_parity.utils import TorchNNFunctionalTestParams, TORCH_NN_COMMON_TEST_HARNESS, \
    compile_cpp_code_inline, set_python_tensors_requires_grad, move_python_tensors_to_device, \
    add_test, compute_cpp_args_construction_stmts_and_forward_arg_symbols, serialize_arg_dict_as_script_module, \
    compute_arg_dict, decorate_test_fn, compute_temp_file_path, generate_error_msg, is_torch_nn_functional_test, \
    try_remove_folder
from cpp_api_parity.sample_functional import SAMPLE_FUNCTIONAL_CPP_SOURCE

# Expected substitutions:
#
# ${functional_variant_name}  (e.g. `BCELoss_no_reduce`)
# ${cpp_args_construction_stmts}
# ${cpp_function_call}
TORCH_NN_FUNCTIONAL_TEST_FORWARD = Template("""
void ${functional_variant_name}_test_forward(
    const std::string& arg_dict_file_path,
    const std::string& forward_output_file_path) {
  pybind11::gil_scoped_release no_gil;

  namespace F = torch::nn::functional;

  // Declare arguments
  auto arg_dict = load_dict_from_file(arg_dict_file_path);
  ${cpp_args_construction_stmts};

  // Some functionals (such as `F::rrelu`) create random tensors in their call path.
  // To make sure the random tensors created are the same in Python/C++, we need
  // to set the RNG seed manually.
  torch::manual_seed(0);

  // Run function with arguments
  auto cpp_output = ${cpp_function_call};

  // Save the output into a file to be compared in Python later
  write_ivalue_to_file(torch::IValue(cpp_output), forward_output_file_path);
}
""")

def run_forward(unit_test_class, test_params):
    device = test_params.device

    inputs = set_python_tensors_requires_grad(move_python_tensors_to_device(
        [arg_value for _, arg_value in test_params.arg_dict['input']], device))
    inputs += move_python_tensors_to_device(
        [arg_value for _, arg_value in test_params.arg_dict['target']], device)
    inputs += move_python_tensors_to_device(
        [arg_value for _, arg_value in test_params.arg_dict['extra_args']], device)

    # Some functionals (such as `F.rrelu`) create random tensors in their call path.
    # To make sure the random tensors created are the same in Python/C++, we need
    # to set the RNG seed manually.
    torch.manual_seed(0)
    python_output = test_params.test_instance.constructor()(*inputs)

    return python_output

def test_forward(unit_test_class, test_params):
    functional_variant_name = test_params.functional_variant_name
    cpp_tmp_folder = test_params.cpp_tmp_folder
    # Remove the temporary folder if it exists already
    try_remove_folder(cpp_tmp_folder)
    os.mkdir(cpp_tmp_folder)

    # Run forward on Python functional
    python_output = run_forward(unit_test_class, test_params)

    # Save Python arguments to be used from C++ function
    arg_dict_file_path = compute_temp_file_path(cpp_tmp_folder, functional_variant_name, 'arg_dict')
    serialize_arg_dict_as_script_module(test_params.arg_dict).save(arg_dict_file_path)

    cpp_test_name = '{}_test_forward'.format(test_params.functional_variant_name)
    cpp_test_fn = getattr(unit_test_class.functional_impl_check_cpp_module, cpp_test_name)

    def run_cpp_test_fn_and_check_output():
        forward_output_file_path = compute_temp_file_path(cpp_tmp_folder, functional_variant_name, 'forward_output')

        cpp_test_fn(arg_dict_file_path, forward_output_file_path)
        cpp_output = torch.load(forward_output_file_path)

        # Check that forward outputs are equal
        unit_test_class.assertEqual(
            python_output, cpp_output,
            msg=generate_error_msg("forward output", cpp_output, python_output))

    run_cpp_test_fn_and_check_output()

    # Remove temporary folder that stores C++ outputs
    try_remove_folder(cpp_tmp_folder)

def compute_functional_name(test_params_dict):
    def camel_case_to_snake_case(camel_case_str):
        return re.sub(r'(?<!^)(?=[A-Z])', '_', camel_case_str).lower()

    if 'cpp_options_args' in test_params_dict:
        # Expected format for `cpp_options_args`: `F::FunctionalFuncOptions(...)`
        # Example output: `binary_cross_entropy`
        return camel_case_to_snake_case(
            test_params_dict['cpp_options_args'].split('(')[0].replace('F::', '').replace('FuncOptions', ''))
    elif 'cpp_function_call' in test_params_dict:
        # Expected format for `cpp_function_call`: `F::functional_name(...)`
        # Example output: `binary_cross_entropy`
        return test_params_dict['cpp_function_call'].split('(')[0].replace('F::', '')
    else:
        raise RuntimeError(
            "`cpp_options_args` or `cpp_function_call` entry must be present in test params dict:\n{}".format(
                pprint.pformat(test_params_dict)))

def compute_cpp_function_call(test_params_dict, arg_dict, functional_name):
    if 'cpp_function_call' in test_params_dict:
        return test_params_dict['cpp_function_call']
    elif 'cpp_options_args' in test_params_dict:
        cpp_forward_args_symbols = [arg_name for arg_name, _ in
                                    arg_dict['input'] + arg_dict['target'] + arg_dict['extra_args']]
        return 'F::{}({}, {})'.format(
            functional_name, ", ".join(cpp_forward_args_symbols), test_params_dict['cpp_options_args'])
    else:
        raise RuntimeError(
            "`cpp_options_args` or `cpp_function_call` entry must be present in test params dict:\n{}".format(
                pprint.pformat(test_params_dict)))

def process_test_params_for_functional(test_params_dict, device, test_instance_class):
    test_instance = test_instance_class(**test_params_dict)
    functional_name = compute_functional_name(test_params_dict)
    assert test_instance.get_name().startswith('test_')
    # Example output: `BCELoss_no_reduce_cuda`
    functional_variant_name = test_instance.get_name()[5:] + (('_' + device) if device != 'cpu' else '')
    arg_dict = compute_arg_dict(test_params_dict, test_instance)

    return TorchNNFunctionalTestParams(
        functional_name=functional_name,
        functional_variant_name=functional_variant_name,
        test_instance=test_instance,
        cpp_function_call=compute_cpp_function_call(test_params_dict, arg_dict, functional_name),
        arg_dict=arg_dict,
        has_parity=test_params_dict.get('has_parity', True),
        device=device,
        cpp_tmp_folder=tempfile.mkdtemp(),
    )

def write_test_to_test_class(
        unit_test_class, test_params_dict, test_instance_class, parity_table, devices):
    assert is_torch_nn_functional_test(test_params_dict)

    assert 'cpp_options_args' in test_params_dict or 'cpp_function_call' in test_params_dict, (
        "To enable C++ API parity test, "
        "`cpp_options_args` or `cpp_function_call` entry must be present in test params dict:\n{}. \n"
        "If you are interested in adding the C++ API parity test, please see:\n"
        "NOTE [How to check NN module / functional API parity between Python and C++ frontends]. \n"
        "If not, please add `test_cpp_api_parity=False` to the test params dict and file an issue about this."
    ).format(pprint.pformat(test_params_dict))

    assert not ('cpp_options_args' in test_params_dict and 'cpp_function_call' in test_params_dict), (
        "Only one of `cpp_options_args` and `cpp_function_call` entries "
        "should be present in test params dict:\n{}").format(pprint.pformat(test_params_dict))

    functional_name = compute_functional_name(test_params_dict)

    assert hasattr(torch.nn.functional, functional_name), \
        "`torch.nn.functional` doesn't have function `{}`. (Discovered while processing\n{}.)".format(
            functional_name, pprint.pformat(test_params_dict))

    functional_full_name = 'F::' + functional_name

    assert functional_full_name in parity_table['torch::nn::functional'], (
        "Please add `{}` entry to `torch::nn::functional` section of `test/cpp_api_parity/parity-tracker.md`. "
        "(Discovered while processing\n{}.)").format(functional_full_name, pprint.pformat(test_params_dict))

    for device in devices:
        test_params = process_test_params_for_functional(
            test_params_dict=test_params_dict,
            device=device,
            test_instance_class=test_instance_class,
        )
        unit_test_name = 'test_torch_nn_functional_{}'.format(test_params.functional_variant_name)
        unit_test_class.functional_test_params_map[unit_test_name] = test_params

        def test_fn(self):
            test_forward(
                unit_test_class=self, test_params=unit_test_class.functional_test_params_map[self._testMethodName])

        test_fn = decorate_test_fn(
            test_fn=test_fn,
            test_cuda=test_params_dict.get('test_cuda', True),
            has_impl_parity=parity_table['torch::nn::functional'][functional_full_name][0] and
            test_params_dict.get('has_parity', True),
            device=device)

        add_test(unit_test_class, unit_test_name, test_fn)

def generate_test_cpp_sources(test_params, template):
    cpp_args_construction_stmts, _ = compute_cpp_args_construction_stmts_and_forward_arg_symbols(test_params)

    test_cpp_sources = template.substitute(
        functional_variant_name=test_params.functional_variant_name,
        cpp_args_construction_stmts=";\n  ".join(cpp_args_construction_stmts),
        cpp_function_call=test_params.cpp_function_call,
    )
    return test_cpp_sources

# Build all C++ tests together, instead of once per test.
def build_cpp_tests(unit_test_class, print_cpp_source=False):
    assert len(unit_test_class.functional_test_params_map) > 0
    cpp_sources = TORCH_NN_COMMON_TEST_HARNESS + SAMPLE_FUNCTIONAL_CPP_SOURCE
    functions = []
    for test_name, test_params in unit_test_class.functional_test_params_map.items():
        cpp_sources += generate_test_cpp_sources(test_params=test_params, template=TORCH_NN_FUNCTIONAL_TEST_FORWARD)
        functions.append('{}_test_forward'.format(test_params.functional_variant_name))
    if print_cpp_source:
        print(cpp_sources)

    cpp_module = compile_cpp_code_inline(
        name='functional_impl_check',
        cpp_sources=cpp_sources,
        functions=functions)
    unit_test_class.functional_impl_check_cpp_module = cpp_module
