#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
import importlib.metadata
import importlib.util
import inspect
import logging
import pkgutil
import re
import traceback

from packaging import version

import skywalking
from skywalking import config
from skywalking.loggings import logger
from skywalking.utils.comparator import operators
from skywalking.utils.exception import VersionRuleException

PackageNotFoundException = importlib.metadata.PackageNotFoundError


def get_pkg_version(pkg_name):
    return importlib.metadata.version(pkg_name)


def install():
    disable_patterns = config.agent_disable_plugins
    if isinstance(disable_patterns, str):
        disable_patterns = [re.compile(p.strip()) for p in disable_patterns.split(',') if p.strip()]
    else:
        disable_patterns = [re.compile(p.strip()) for p in disable_patterns if p.strip()]
    for importer, modname, _ispkg in pkgutil.iter_modules(skywalking.plugins.__path__):
        if any(pattern.match(modname) for pattern in disable_patterns):
            logger.info("plugin %s is disabled and thus won't be installed", modname)
            continue
        logger.debug('installing plugin %s', modname)
        spec = importer.find_spec(modname)
        plugin = importlib.util.module_from_spec(spec)
        spec.loader.exec_module(plugin)

        # todo: refactor the version checker, currently it doesn't really work as intended
        supported = pkg_version_check(plugin)
        if not supported:
            logger.debug("check version for plugin %s's corresponding package failed, thus "
                         "won't be installed", modname)
            continue

        if not hasattr(plugin, 'install') or inspect.ismethod(plugin.install):
            logger.warning("no `install` method in plugin %s, thus the plugin won't be installed", modname)
            continue

        # noinspection PyBroadException
        try:
            plugin.install()
            logger.debug('Successfully installed plugin %s', modname)
        except Exception:
            logger.warning(
                'Plugin %s failed to install, please ignore this warning '
                'if the package is not used in your application.',
                modname
            )
            traceback.print_exc() if logger.isEnabledFor(logging.DEBUG) else None


def pkg_version_check(plugin):
    supported = True

    # no version rules was set, no checks
    if not hasattr(plugin, 'version_rule'):
        return supported

    pkg_name = plugin.version_rule.get('name')
    rules = plugin.version_rule.get('rules')

    try:
        current_pkg_version = get_pkg_version(pkg_name)
    except PackageNotFoundException:
        # when failed to get the version, we consider it as supported.
        return supported

    current_version = version.parse(current_pkg_version)
    # pass one rule in rules (OR)
    for rule in rules:
        if rule.find(' ') == -1:
            if check(rule, current_version):
                return supported
        else:
            # have to pass all rule_uint in this rule (AND)
            rule_units = rule.split(' ')
            results = [check(unit, current_version) for unit in rule_units]
            if False in results:
                # check failed, try to check next rule
                continue
            else:
                return supported

    supported = False
    return supported


def check(rule_unit, current_version):
    idx = 2 if rule_unit[1] == '=' else 1
    symbol = rule_unit[0:idx]
    expect_pkg_version = rule_unit[idx:]

    expect_version = version.parse(expect_pkg_version)
    f = operators.get(symbol) or None
    if not f:
        raise VersionRuleException(f'version rule {rule_unit} error. only allow >,>=,==,<=,<,!= symbols')

    return f(current_version, expect_version)