import importlib
import inspect
import logging
import os
import pkgutil
import re
import sys
import wrapt

from aws_xray_sdk import global_sdk_config
from .utils.compat import PY2, is_classmethod, is_instance_method

log = logging.getLogger(__name__)

SUPPORTED_MODULES = (
    'aiobotocore',
    'botocore',
    'pynamodb',
    'requests',
    'sqlite3',
    'mysql',
    'httplib',
    'pymongo',
    'pymysql',
    'psycopg2',
    'pg8000',
    'sqlalchemy_core',
)

NO_DOUBLE_PATCH = (
    'aiobotocore',
    'botocore',
    'pynamodb',
    'requests',
    'sqlite3',
    'mysql',
    'pymongo',
    'pymysql',
    'psycopg2',
    'pg8000',
    'sqlalchemy_core',
)

_PATCHED_MODULES = set()


def patch_all(double_patch=False):
    if double_patch:
        patch(SUPPORTED_MODULES, raise_errors=False)
    else:
        patch(NO_DOUBLE_PATCH, raise_errors=False)


def _is_valid_import(module):
    module = module.replace('.', '/')
    if PY2:
        return bool(pkgutil.get_loader(module))
    else:
        realpath = os.path.realpath(module)
        is_module = os.path.isdir(realpath) and (
            os.path.isfile('{}/__init__.py'.format(module)) or os.path.isfile('{}/__init__.pyc'.format(module))
        )
        is_file = not is_module and (
                os.path.isfile('{}.py'.format(module)) or os.path.isfile('{}.pyc'.format(module))
        )
        return is_module or is_file


def patch(modules_to_patch, raise_errors=True, ignore_module_patterns=None):
    enabled = global_sdk_config.sdk_enabled()
    if not enabled:
        log.debug("Skipped patching modules %s because the SDK is currently disabled." % ', '.join(modules_to_patch))
        return  # Disable module patching if the SDK is disabled.
    modules = set()
    for module_to_patch in modules_to_patch:
        # boto3 depends on botocore and patching botocore is sufficient
        if module_to_patch == 'boto3':
            modules.add('botocore')
        # aioboto3 depends on aiobotocore and patching aiobotocore is sufficient
        elif module_to_patch == 'aioboto3':
            modules.add('aiobotocore')
        # pynamodb requires botocore to be patched as well
        elif module_to_patch == 'pynamodb':
            modules.add('botocore')
            modules.add(module_to_patch)
        else:
            modules.add(module_to_patch)

    unsupported_modules = set(module for module in modules if module not in SUPPORTED_MODULES)
    native_modules = modules - unsupported_modules

    external_modules = set(module for module in unsupported_modules if _is_valid_import(module))
    unsupported_modules = unsupported_modules - external_modules

    if unsupported_modules:
        raise Exception('modules %s are currently not supported for patching'
                        % ', '.join(unsupported_modules))

    for m in native_modules:
        _patch_module(m, raise_errors)

    ignore_module_patterns = [re.compile(pattern) for pattern in ignore_module_patterns or []]
    for m in external_modules:
        _external_module_patch(m, ignore_module_patterns)


def _patch_module(module_to_patch, raise_errors=True):
    try:
        _patch(module_to_patch)
    except Exception:
        if raise_errors:
            raise
        log.debug('failed to patch module %s', module_to_patch)


def _patch(module_to_patch):

    path = 'aws_xray_sdk.ext.%s' % module_to_patch

    if module_to_patch in _PATCHED_MODULES:
        log.debug('%s already patched', module_to_patch)
        return

    imported_module = importlib.import_module(path)
    imported_module.patch()

    _PATCHED_MODULES.add(module_to_patch)
    log.info('successfully patched module %s', module_to_patch)


def _patch_func(parent, func_name, func, modifier=lambda x: x):
    if func_name not in parent.__dict__:
        # Ignore functions not directly defined in parent, i.e. exclude inherited ones
        return

    from aws_xray_sdk.core import xray_recorder

    capture_name = func_name
    if func_name.startswith('__') and func_name.endswith('__'):
        capture_name = '{}.{}'.format(parent.__name__, capture_name)
    setattr(parent, func_name, modifier(xray_recorder.capture(name=capture_name)(func)))


def _patch_class(module, cls):
    for member_name, member in inspect.getmembers(cls, inspect.isclass):
        if member.__module__ == module.__name__:
            # Only patch classes of the module, ignore imports
            _patch_class(module, member)

    for member_name, member in inspect.getmembers(cls, inspect.ismethod):
        if member.__module__ == module.__name__:
            # Only patch methods of the class defined in the module, ignore other modules
            if is_classmethod(member):
                # classmethods are internally generated through descriptors. The classmethod
                # decorator must be the last applied, so we cannot apply another one on top
                log.warning('Cannot automatically patch classmethod %s.%s, '
                            'please apply decorator manually', cls.__name__, member_name)
            else:
                _patch_func(cls, member_name, member)

    for member_name, member in inspect.getmembers(cls, inspect.isfunction):
        if member.__module__ == module.__name__:
            # Only patch static methods of the class defined in the module, ignore other modules
            if is_instance_method(cls, member_name, member):
                _patch_func(cls, member_name, member)
            else:
                _patch_func(cls, member_name, member, modifier=staticmethod)


def _on_import(module):
    for member_name, member in inspect.getmembers(module, inspect.isfunction):
        if member.__module__ == module.__name__:
            # Only patch functions of the module, ignore imports
            _patch_func(module, member_name, member)

    for member_name, member in inspect.getmembers(module, inspect.isclass):
        if member.__module__ == module.__name__:
            # Only patch classes of the module, ignore imports
            _patch_class(module, member)


def _external_module_patch(module, ignore_module_patterns):
    if module.startswith('.'):
        raise Exception('relative packages not supported for patching: {}'.format(module))

    if module in _PATCHED_MODULES:
        log.debug('%s already patched', module)
    elif any(pattern.match(module) for pattern in ignore_module_patterns):
        log.debug('%s ignored due to rules: %s', module, ignore_module_patterns)
    else:
        if module in sys.modules:
            _on_import(sys.modules[module])
        else:
            wrapt.importer.when_imported(module)(_on_import)

    for loader, submodule_name, is_module in pkgutil.iter_modules([module.replace('.', '/')]):
        submodule = '.'.join([module, submodule_name])
        if is_module:
            _external_module_patch(submodule, ignore_module_patterns)
        else:
            if submodule in _PATCHED_MODULES:
                log.debug('%s already patched', submodule)
                continue
            elif any(pattern.match(submodule) for pattern in ignore_module_patterns):
                log.debug('%s ignored due to rules: %s', submodule, ignore_module_patterns)
                continue

            if submodule in sys.modules:
                _on_import(sys.modules[submodule])
            else:
                wrapt.importer.when_imported(submodule)(_on_import)

            _PATCHED_MODULES.add(submodule)
            log.info('successfully patched module %s', submodule)

    if module not in _PATCHED_MODULES:
        _PATCHED_MODULES.add(module)
        log.info('successfully patched module %s', module)
