"""Stub generator for C modules.

The public interface is via the mypy.stubgen module.
"""

import importlib
import os.path
import re
from typing import List, Dict, Tuple, Optional, Mapping, Any
from types import ModuleType

from mypy.stubutil import is_c_module, write_header, infer_sig_from_docstring


def generate_stub_for_c_module(module_name: str,
                               target: str,
                               add_header: bool = True,
                               sigs: Dict[str, str] = {},
                               class_sigs: Dict[str, str] = {},
                               ) -> None:
    module = importlib.import_module(module_name)
    assert is_c_module(module), '%s is not a C module' % module_name
    subdir = os.path.dirname(target)
    if subdir and not os.path.isdir(subdir):
        os.makedirs(subdir)
    functions = []  # type: List[str]
    done = set()
    items = sorted(module.__dict__.items(), key=lambda x: x[0])
    for name, obj in items:
        if is_c_function(obj):
            generate_c_function_stub(module, name, obj, functions, sigs=sigs)
            done.add(name)
    types = []  # type: List[str]
    for name, obj in items:
        if name.startswith('__') and name.endswith('__'):
            continue
        if is_c_type(obj):
            generate_c_type_stub(module, name, obj, types, sigs=sigs, class_sigs=class_sigs)
            done.add(name)
    variables = []
    for name, obj in items:
        if name.startswith('__') and name.endswith('__'):
            continue
        if name not in done:
            type_str = type(obj).__name__
            if type_str not in ('int', 'str', 'bytes', 'float', 'bool'):
                type_str = 'Any'
            variables.append('%s: %s' % (name, type_str))
    output = []
    for line in variables:
        output.append(line)
    if output and functions:
        output.append('')
    for line in functions:
        output.append(line)
    for line in types:
        if line.startswith('class') and output and output[-1]:
            output.append('')
        output.append(line)
    output = add_typing_import(output)
    with open(target, 'w') as file:
        if add_header:
            write_header(file, module_name)
        for line in output:
            file.write('%s\n' % line)


def add_typing_import(output: List[str]) -> List[str]:
    names = []
    for name in ['Any']:
        if any(re.search(r'\b%s\b' % name, line) for line in output):
            names.append(name)
    if names:
        return ['from typing import %s' % ', '.join(names), ''] + output
    else:
        return output[:]


def is_c_function(obj: object) -> bool:
    return type(obj) is type(ord)


def is_c_method(obj: object) -> bool:
    return type(obj) in (type(str.index),
                         type(str.__add__),
                         type(str.__new__))


def is_c_classmethod(obj: object) -> bool:
    type_str = type(obj).__name__
    return type_str == 'classmethod_descriptor'


def is_c_type(obj: object) -> bool:
    return type(obj) is type(int)


def generate_c_function_stub(module: ModuleType,
                             name: str,
                             obj: object,
                             output: List[str],
                             self_var: Optional[str] = None,
                             sigs: Dict[str, str] = {},
                             class_name: Optional[str] = None,
                             class_sigs: Dict[str, str] = {},
                             ) -> None:
    if self_var:
        self_arg = '%s, ' % self_var
    else:
        self_arg = ''
    if (name in ('__new__', '__init__') and name not in sigs and class_name and
            class_name in class_sigs):
        sig = class_sigs[class_name]
    else:
        docstr = getattr(obj, '__doc__', None)
        inferred = infer_sig_from_docstring(docstr, name)
        if inferred:
            sig = inferred
        else:
            if class_name and name not in sigs:
                sig = infer_method_sig(name)
            else:
                sig = sigs.get(name, '(*args, **kwargs)')
    sig = sig[1:-1]
    if sig:
        if sig.split(',', 1)[0] == self_var:
            self_arg = ''
    else:
        self_arg = self_arg.replace(', ', '')
    output.append('def %s(%s%s): ...' % (name, self_arg, sig))


def generate_c_type_stub(module: ModuleType,
                         class_name: str,
                         obj: type,
                         output: List[str],
                         sigs: Dict[str, str] = {},
                         class_sigs: Dict[str, str] = {},
                         ) -> None:
    # typeshed gives obj.__dict__ the not quite correct type Dict[str, Any]
    # (it could be a mappingproxy!), which makes mypyc mad, so obfuscate it.
    obj_dict = getattr(obj, '__dict__')  # type: Mapping[str, Any]
    items = sorted(obj_dict.items(), key=lambda x: method_name_sort_key(x[0]))
    methods = []
    done = set()
    for attr, value in items:
        if is_c_method(value) or is_c_classmethod(value):
            done.add(attr)
            if not is_skipped_attribute(attr):
                if is_c_classmethod(value):
                    methods.append('@classmethod')
                    self_var = 'cls'
                else:
                    self_var = 'self'
                if attr == '__new__':
                    # TODO: We should support __new__.
                    if '__init__' in obj_dict:
                        # Avoid duplicate functions if both are present.
                        # But is there any case where .__new__() has a
                        # better signature than __init__() ?
                        continue
                    attr = '__init__'
                generate_c_function_stub(module, attr, value, methods, self_var, sigs=sigs,
                                         class_name=class_name, class_sigs=class_sigs)
    variables = []
    for attr, value in items:
        if is_skipped_attribute(attr):
            continue
        if attr not in done:
            variables.append('%s: Any = ...' % attr)
    all_bases = obj.mro()
    if all_bases[-1] is object:
        # TODO: Is this always object?
        del all_bases[-1]
    # remove the class itself
    all_bases = all_bases[1:]
    # Remove base classes of other bases as redundant.
    bases = []  # type: List[type]
    for base in all_bases:
        if not any(issubclass(b, base) for b in bases):
            bases.append(base)
    if bases:
        bases_str = '(%s)' % ', '.join(base.__name__ for base in bases)
    else:
        bases_str = ''
    if not methods and not variables:
        output.append('class %s%s: ...' % (class_name, bases_str))
    else:
        output.append('class %s%s:' % (class_name, bases_str))
        for variable in variables:
            output.append('    %s' % variable)
        for method in methods:
            output.append('    %s' % method)


def method_name_sort_key(name: str) -> Tuple[int, str]:
    if name in ('__new__', '__init__'):
        return (0, name)
    if name.startswith('__') and name.endswith('__'):
        return (2, name)
    return (1, name)


def is_skipped_attribute(attr: str) -> bool:
    return attr in ('__getattribute__',
                    '__str__',
                    '__repr__',
                    '__doc__',
                    '__dict__',
                    '__module__',
                    '__weakref__')  # For pickling


def infer_method_sig(name: str) -> str:
    if name.startswith('__') and name.endswith('__'):
        name = name[2:-2]
        if name in ('hash', 'iter', 'next', 'sizeof', 'copy', 'deepcopy', 'reduce', 'getinitargs',
                    'int', 'float', 'trunc', 'complex', 'bool'):
            return '()'
        if name == 'getitem':
            return '(index)'
        if name == 'setitem':
            return '(index, object)'
        if name in ('delattr', 'getattr'):
            return '(name)'
        if name == 'setattr':
            return '(name, value)'
        if name == 'getstate':
            return '()'
        if name == 'setstate':
            return '(state)'
        if name in ('eq', 'ne', 'lt', 'le', 'gt', 'ge',
                    'add', 'radd', 'sub', 'rsub', 'mul', 'rmul',
                    'mod', 'rmod', 'floordiv', 'rfloordiv', 'truediv', 'rtruediv',
                    'divmod', 'rdivmod', 'pow', 'rpow'):
            return '(other)'
        if name in ('neg', 'pos'):
            return '()'
    return '(*args, **kwargs)'