# this code should be common among cwrap and ATen preprocessing
# for now, I have put it in one place but right now is copied out of cwrap

from copy import deepcopy
from itertools import product


def parse_arguments(args):
    new_args = []
    for arg in args:
        # Simple arg declaration of form "<type> <name>"
        if isinstance(arg, str):
            t, _, name = arg.partition(' ')
            new_args.append({'type': t, 'name': name})
        elif isinstance(arg, dict):
            if 'arg' in arg:
                arg['type'], _, arg['name'] = arg['arg'].partition(' ')
                del arg['arg']
            new_args.append(arg)
        else:
            assert False
    return new_args


def set_declaration_defaults(declaration):
    declaration.setdefault('arguments', [])
    declaration.setdefault('return', 'void')
    if 'cname' not in declaration:
        declaration['cname'] = declaration['name']
    if 'backends' not in declaration:
        declaration['backends'] = ['CPU', 'CUDA']
    if 'api_name' not in declaration:
        declaration['api_name'] = (declaration['python_name']
                                   if 'python_name' in declaration else declaration['name'])
    # Simulate multiple dispatch, even if it's not necessary
    if 'options' not in declaration:
        declaration['options'] = [{'arguments': declaration['arguments']}]
        del declaration['arguments']
    # Parse arguments (some of them can be strings)
    for option in declaration['options']:
        option['arguments'] = parse_arguments(option['arguments'])
    # Propagate defaults from declaration to options
    for option in declaration['options']:
        for k, v in declaration.items():
            # TODO(zach): why does cwrap not propagate 'name'? I need it
            # propagaged for ATen
            if k != 'options':
                option.setdefault(k, v)

# TODO(zach): added option to remove keyword handling for C++ which cannot
# support it.


def filter_unique_options(options, allow_kwarg, type_to_signature, remove_self):
    def exclude_arg(arg):
        return arg.get('ignore_check') or arg['type'] == 'CONSTANT'

    def exclude_arg_with_self_check(arg):
        return exclude_arg(arg) or (remove_self and arg['name'] == 'self')

    def signature(option, kwarg_only_count):
        if kwarg_only_count == 0:
            kwarg_only_count = None
        else:
            kwarg_only_count = -kwarg_only_count
        arg_signature = '#'.join(
            type_to_signature.get(arg['type'], arg['type'])
            for arg in option['arguments'][:kwarg_only_count]
            if not exclude_arg_with_self_check(arg))
        if kwarg_only_count is None:
            return arg_signature
        kwarg_only_signature = '#'.join(
            arg['name'] + '#' + arg['type']
            for arg in option['arguments'][kwarg_only_count:]
            if not exclude_arg(arg))
        return arg_signature + "#-#" + kwarg_only_signature
    seen_signatures = set()
    unique = []
    for option in options:
        # if only check num_kwarg_only == 0 if allow_kwarg == False
        limit = len(option['arguments']) if allow_kwarg else 0
        for num_kwarg_only in range(0, limit + 1):
            sig = signature(option, num_kwarg_only)
            if sig not in seen_signatures:
                if num_kwarg_only > 0:
                    for arg in option['arguments'][-num_kwarg_only:]:
                        arg['kwarg_only'] = True
                unique.append(option)
                seen_signatures.add(sig)
                break
    return unique


def enumerate_options_due_to_default(declaration,
                                     allow_kwarg=True, type_to_signature=[], remove_self=True):

    # Checks to see if an argument with a default keyword is a Tensor that
    # by default can be NULL. In this case, instead of generating another
    # option that excludes this argument, we will instead generate a single
    # function call that allows for the Tensor to be NULL
    def is_nullable_tensor_arg(arg):
        return arg['type'] == 'THTensor*' and arg['default'] == 'nullptr'

    # TODO(zach): in cwrap this is shared among all declarations
    # but seems to assume that all declarations will have the same
    new_options = []
    for option in declaration['options']:
        optional_args = []
        for i, arg in enumerate(option['arguments']):
            if 'default' in arg:
                optional_args.append(i)
        for permutation in product((True, False), repeat=len(optional_args)):
            option_copy = deepcopy(option)
            for i, bit in zip(optional_args, permutation):
                arg = option_copy['arguments'][i]
                if not bit:
                    arg['type'] = 'CONSTANT'
                    arg['ignore_check'] = True
                    # PyYAML interprets NULL as None...
                    arg['name'] = 'NULL' if arg['default'] is None else arg['default']
            new_options.append(option_copy)
    declaration['options'] = filter_unique_options(new_options,
                                                   allow_kwarg, type_to_signature, remove_self)


def sort_by_number_of_options(declaration, reverse=True):
    def num_checked_args(option):
        return sum(map(lambda a: not a.get('ignore_check', False), option['arguments']))
    declaration['options'].sort(key=num_checked_args, reverse=reverse)


class Function(object):

    def __init__(self, name):
        self.name = name
        self.arguments = []

    def add_argument(self, arg):
        assert isinstance(arg, Argument)
        self.arguments.append(arg)

    def __repr__(self):
        return self.name + '(' + ', '.join(map(lambda a: a.__repr__(), self.arguments)) + ')'


class Argument(object):

    def __init__(self, _type, name, is_optional):
        self.type = _type
        self.name = name
        self.is_optional = is_optional

    def __repr__(self):
        return self.type + ' ' + self.name


def parse_header(path):
    with open(path, 'r') as f:
        lines = f.read().split('\n')

    # Remove empty lines and prebackend directives
    lines = filter(lambda l: l and not l.startswith('#'), lines)
    # Remove line comments
    lines = map(lambda l: l.partition('//'), lines)
    # Select line and comment part
    lines = map(lambda l: (l[0].strip(), l[2].strip()), lines)
    # Remove trailing special signs
    lines = map(lambda l: (l[0].rstrip(');').rstrip(','), l[1]), lines)
    # Split arguments
    lines = map(lambda l: (l[0].split(','), l[1]), lines)
    # Flatten lines
    new_lines = []
    for l, c in lines:
        for split in l:
            new_lines.append((split, c))
    lines = new_lines
    del new_lines
    # Remove unnecessary whitespace
    lines = map(lambda l: (l[0].strip(), l[1]), lines)
    # Remove empty lines
    lines = filter(lambda l: l[0], lines)
    generic_functions = []
    for l, c in lines:
        if l.startswith('TH_API void THNN_'):
            fn_name = l.lstrip('TH_API void THNN_')
            if fn_name[0] == '(' and fn_name[-2] == ')':
                fn_name = fn_name[1:-2]
            else:
                fn_name = fn_name[:-1]
            generic_functions.append(Function(fn_name))
        elif l:
            t, name = l.split()
            if '*' in name:
                t = t + '*'
                name = name[1:]
            generic_functions[-1].add_argument(
                Argument(t, name, '[OPTIONAL]' in c))
    return generic_functions
