"""本模块实现插件加载流程。

参考: [import hooks](https://docs.python.org/3/reference/import.html#import-hooks), [PEP302](https://www.python.org/dev/peps/pep-0302/)

FrontMatter:
    sidebar_position: 5
    description: nonebot.plugin.manager 模块
"""
import sys
import pkgutil
import importlib
from pathlib import Path
from itertools import chain
from types import ModuleType
from importlib.abc import MetaPathFinder
from importlib.machinery import PathFinder, SourceFileLoader
from typing import Set, Dict, List, Union, Iterable, Optional, Sequence

from nonebot.log import logger
from nonebot.utils import escape_tag, path_to_module_name

from .plugin import Plugin, PluginMetadata
from . import (
    _managers,
    _new_plugin,
    _revert_plugin,
    _current_plugin_chain,
    _module_name_to_plugin_name,
)


class PluginManager:
    """插件管理器。

    参数:
        plugins: 独立插件模块名集合。
        search_path: 插件搜索路径（文件夹）。
    """

    def __init__(
        self,
        plugins: Optional[Iterable[str]] = None,
        search_path: Optional[Iterable[str]] = None,
    ):
        # simple plugin not in search path
        self.plugins: Set[str] = set(plugins or [])
        self.search_path: Set[str] = set(search_path or [])

        # cache plugins
        self._third_party_plugin_names: Dict[str, str] = {}
        self._searched_plugin_names: Dict[str, Path] = {}
        self.prepare_plugins()

    @property
    def third_party_plugins(self) -> Set[str]:
        """返回所有独立插件名称。"""
        return set(self._third_party_plugin_names.keys())

    @property
    def searched_plugins(self) -> Set[str]:
        """返回已搜索到的插件名称。"""
        return set(self._searched_plugin_names.keys())

    @property
    def available_plugins(self) -> Set[str]:
        """返回当前插件管理器中可用的插件名称。"""
        return self.third_party_plugins | self.searched_plugins

    def _previous_plugins(self) -> Set[str]:
        _pre_managers: List[PluginManager]
        if self in _managers:
            _pre_managers = _managers[: _managers.index(self)]
        else:
            _pre_managers = _managers[:]

        return {
            *chain.from_iterable(manager.available_plugins for manager in _pre_managers)
        }

    def prepare_plugins(self) -> Set[str]:
        """搜索插件并缓存插件名称。"""
        # get all previous ready to load plugins
        previous_plugins = self._previous_plugins()
        searched_plugins: Dict[str, Path] = {}
        third_party_plugins: Dict[str, str] = {}

        # check third party plugins
        for plugin in self.plugins:
            name = _module_name_to_plugin_name(plugin)
            if name in third_party_plugins or name in previous_plugins:
                raise RuntimeError(
                    f"Plugin already exists: {name}! Check your plugin name"
                )
            third_party_plugins[name] = plugin

        self._third_party_plugin_names = third_party_plugins

        # check plugins in search path
        for module_info in pkgutil.iter_modules(self.search_path):
            # ignore if startswith "_"
            if module_info.name.startswith("_"):
                continue

            if (
                module_info.name in searched_plugins
                or module_info.name in previous_plugins
                or module_info.name in third_party_plugins
            ):
                raise RuntimeError(
                    f"Plugin already exists: {module_info.name}! Check your plugin name"
                )

            if not (
                module_spec := module_info.module_finder.find_spec(
                    module_info.name, None
                )
            ):
                continue
            if not (module_path := module_spec.origin):
                continue
            searched_plugins[module_info.name] = Path(module_path).resolve()

        self._searched_plugin_names = searched_plugins

        return self.available_plugins

    def load_plugin(self, name: str) -> Optional[Plugin]:
        """加载指定插件。

        对于独立插件，可以使用完整插件模块名或者插件名称。

        参数:
            name: 插件名称。
        """

        try:
            if name in self.plugins:
                module = importlib.import_module(name)
            elif name in self._third_party_plugin_names:
                module = importlib.import_module(self._third_party_plugin_names[name])
            elif name in self._searched_plugin_names:
                module = importlib.import_module(
                    path_to_module_name(self._searched_plugin_names[name])
                )
            else:
                raise RuntimeError(f"Plugin not found: {name}! Check your plugin name")

            logger.opt(colors=True).success(
                f'Succeeded to import "<y>{escape_tag(name)}</y>"'
            )
            if (plugin := getattr(module, "__plugin__", None)) is None:
                raise RuntimeError(
                    f"Module {module.__name__} is not loaded as a plugin! "
                    "Make sure not to import it before loading."
                )
            return plugin
        except Exception as e:
            logger.opt(colors=True, exception=e).error(
                f'<r><bg #f8bbd0>Failed to import "{escape_tag(name)}"</bg #f8bbd0></r>'
            )

    def load_all_plugins(self) -> Set[Plugin]:
        """加载所有可用插件。"""

        return set(
            filter(None, (self.load_plugin(name) for name in self.available_plugins))
        )


class PluginFinder(MetaPathFinder):
    def find_spec(
        self,
        fullname: str,
        path: Optional[Sequence[Union[bytes, str]]],
        target: Optional[ModuleType] = None,
    ):
        if _managers:
            module_spec = PathFinder.find_spec(fullname, path, target)
            if not module_spec:
                return
            module_origin = module_spec.origin
            if not module_origin:
                return
            module_path = Path(module_origin).resolve()

            for manager in reversed(_managers):
                # use path instead of name in case of submodule name conflict
                if (
                    fullname in manager.plugins
                    or module_path in manager._searched_plugin_names.values()
                ):
                    module_spec.loader = PluginLoader(manager, fullname, module_origin)
                    return module_spec
        return


class PluginLoader(SourceFileLoader):
    def __init__(self, manager: PluginManager, fullname: str, path) -> None:
        self.manager = manager
        self.loaded = False
        super().__init__(fullname, path)

    def create_module(self, spec) -> Optional[ModuleType]:
        if self.name in sys.modules:
            self.loaded = True
            return sys.modules[self.name]
        # return None to use default module creation
        return super().create_module(spec)

    def exec_module(self, module: ModuleType) -> None:
        if self.loaded:
            return

        # create plugin before executing
        plugin = _new_plugin(self.name, module, self.manager)
        setattr(module, "__plugin__", plugin)

        # detect parent plugin before entering current plugin context
        parent_plugins = _current_plugin_chain.get()
        for pre_plugin in reversed(parent_plugins):
            if _managers.index(pre_plugin.manager) < _managers.index(self.manager):
                plugin.parent_plugin = pre_plugin
                pre_plugin.sub_plugins.add(plugin)
                break

        # enter plugin context
        _plugin_token = _current_plugin_chain.set(parent_plugins + (plugin,))

        try:
            super().exec_module(module)
        except Exception:
            _revert_plugin(plugin)
            raise
        finally:
            # leave plugin context
            _current_plugin_chain.reset(_plugin_token)

        # get plugin metadata
        metadata: Optional[PluginMetadata] = getattr(module, "__plugin_meta__", None)
        plugin.metadata = metadata

        return


sys.meta_path.insert(0, PluginFinder())