"""
Plugin manager module.
Define the PluginManager class, the one that glues all the plugins and
the API together. Defines also a bunch of variables related to the
plugin env.
"""

import logging
import os
from typing import Dict, Set
from importlib import import_module, machinery
from pathlib import Path
from os import path
import pkg_resources

from poezio import tabs, xdg
from poezio.core.structs import Command, Completion
from poezio.plugin import PluginAPI
from poezio.config import config

log = logging.getLogger(__name__)


class PluginManager:
    """
    Plugin Manager
    Contains all the references to the plugins
    And keeps track of everything the plugin has done through the API.
    """

    rdeps: Dict[str, Set[str]] = {}

    def __init__(self, core):
        self.core = core
        # module name -> module object
        self.modules = {}
        # module name -> plugin object
        self.plugins = {}
        # module name -> dict of commands loaded for the module
        self.commands = {}
        # module name -> list of event_name/handler pairs loaded for the module
        self.event_handlers = {}
        # module name -> dict of tab types; tab type -> commands
        # loaded by the module
        self.tab_commands = {}
        # module name → dict of keys/handlers loaded for the module
        self.keys = {}
        # module name → dict of tab types; tab type → list of keybinds (tuples)
        self.tab_keys = {}
        self.roster_elements = {}

        self.finder = machinery.PathFinder()

        self.initial_set_plugins_dir()
        self.initial_set_plugins_conf_dir()
        self.fill_load_path()

        self.plugin_api = PluginAPI(core, self)

    def disable_plugins(self):
        for plugin in set(self.plugins.keys()):
            self.unload(plugin, notify=False)

    def set_rdeps(self, name):
        """
        Runs through plugin dependencies to build the reverse dependencies table.
        """

        if name not in self.rdeps:
            self.rdeps[name] = set()
        for dep in self.plugins[name].dependencies:
            if dep not in self.rdeps:
                self.rdeps[dep] = {name}
            else:
                self.rdeps[dep].add(name)

    def load(self, name: str, notify=True, unload_first=True):
        """
        Load a plugin.
        """
        if not unload_first and name in self.plugins:
            return None
        if name in self.plugins:
            self.unload(name)

        try:
            module = None
            loader = self.finder.find_module(name, self.load_path)
            if loader:
                log.debug('Found candidate loader for plugin %s: %r', name, loader)
                module = loader.load_module()
                if module is None:
                    log.debug('Failed to load plugin %s from loader', name)
            else:
                try:
                    module = import_module('poezio_plugins.%s' % name)
                except ModuleNotFoundError:
                    pass
            for entry in pkg_resources.iter_entry_points('poezio_plugins'):
                if entry.name == name:
                    log.debug('Found candidate entry for plugin %s: %r', name, entry)
                    try:
                        module = entry.load()
                    except Exception as exn:
                        log.debug('Failed to import plugin: %s\n%r', name,
                                  exn, exc_info=True)
                    finally:
                        break
            if not module:
                self.core.information('Could not find plugin: %s' % name,
                                      'Error')
                return
            log.debug('Plugin %s loaded from "%s"', name, module.__file__)
        except Exception as e:
            log.debug("Could not load plugin %s", name, exc_info=True)
            self.core.information("Could not load plugin %s: %s" % (name, e),
                                  'Error')
        finally:
            if not module:
                return

        self.modules[name] = module
        self.commands[name] = {}
        self.keys[name] = {}
        self.tab_keys[name] = {}
        self.tab_commands[name] = {}
        self.event_handlers[name] = []
        try:
            self.plugins[name] = None

            for dep in module.Plugin.dependencies:
                self.load(dep, unload_first=False)
                if dep not in self.plugins:
                    log.debug(
                        'Plugin %s couldn\'t load because of dependency %s',
                        name, dep
                    )
                    return None
                # Add reference of the dep to the plugin's usage
                module.Plugin.refs[dep] = self.plugins[dep]

            self.plugins[name] = module.Plugin(name, self.plugin_api, self.core,
                                               self.plugins_conf_dir)
            self.set_rdeps(name)

        except Exception as e:
            log.error('Error while loading the plugin %s', name, exc_info=True)
            if notify:
                self.core.information(
                    'Unable to load the plugin %s: %s' % (name, e), 'Error')
            self.unload(name, notify=False)
        else:
            if notify:
                self.core.information('Plugin %s loaded' % name, 'Info')

    def unload(self, name: str, notify=True):
        """
        Unloads plugin as well as plugins depending on it.
        """

        if name in self.plugins:
            try:
                if self.plugins[name] is not None:
                    self.plugins[name]._unloading = True  # Prevents loops
                    for rdep in self.rdeps[name].copy():
                        if rdep in self.plugins and not self.plugins[rdep]._unloading:
                            self.unload(rdep)
                            if rdep in self.plugins:
                                log.debug('Failed to unload reverse dependency %s first.', rdep)
                                return None

                for command in self.commands[name].keys():
                    del self.core.commands[command]
                for key in self.keys[name].keys():
                    del self.core.key_func[key]
                for tab in list(self.tab_commands[name].keys()):
                    for command in self.tab_commands[name][tab][:]:
                        self.del_tab_command(name, getattr(tabs, tab),
                                             command[0])
                    del self.tab_commands[name][tab]
                for tab in list(self.tab_keys[name].keys()):
                    for key in self.tab_keys[name][tab][:]:
                        self.del_tab_key(name, getattr(tabs, tab), key[0])
                    del self.tab_keys[name][tab]
                for event_name, handler in self.event_handlers[name][:]:
                    self.del_event_handler(name, event_name, handler)

                if self.plugins[name] is not None:
                    self.plugins[name].unload()
                del self.plugins[name]
                del self.rdeps[name]
                del self.commands[name]
                del self.keys[name]
                del self.tab_commands[name]
                del self.event_handlers[name]
                if notify:
                    self.core.information('Plugin %s unloaded' % name, 'Info')
            except Exception as e:
                log.debug("Could not unload plugin %s", name, exc_info=True)
                self.core.information(
                    "Could not unload plugin %s: %s" % (name, e), 'Error')

    def add_command(self,
                    module_name,
                    name,
                    handler,
                    help,
                    completion=None,
                    short='',
                    usage=''):
        """
        Add a global command.
        """
        if name in self.core.commands:
            raise Exception("Command '%s' already exists" % (name, ))

        commands = self.commands[module_name]
        commands[name] = Command(handler, help, completion, short, usage)
        self.core.commands[name] = commands[name]

    def del_command(self, module_name, name):
        """
        Remove a global command added through add_command.
        """
        if name in self.commands[module_name]:
            del self.commands[module_name][name]
            if name in self.core.commands:
                del self.core.commands[name]

    def add_tab_command(self,
                        module_name,
                        tab_type,
                        name,
                        handler,
                        help,
                        completion=None,
                        short='',
                        usage=''):
        """
        Add a command only for a type of Tab.
        """
        commands = self.tab_commands[module_name]
        t = tab_type.__name__
        if name in tab_type.plugin_commands:
            return
        if t not in commands:
            commands[t] = []
        commands[t].append((name, handler, help, completion))
        tab_type.plugin_commands[name] = Command(handler, help, completion,
                                                 short, usage)
        for tab in self.core.tabs:
            if isinstance(tab, tab_type):
                tab.update_commands()

    def del_tab_command(self, module_name, tab_type, name):
        """
        Remove a command added through add_tab_command.
        """
        commands = self.tab_commands[module_name]
        t = tab_type.__name__
        if t not in commands:
            return
        for command in commands[t]:
            if command[0] == name:
                commands[t].remove(command)
                del tab_type.plugin_commands[name]
                for tab in self.core.tabs:
                    if isinstance(tab, tab_type) and name in tab.commands:
                        del tab.commands[name]

    def add_tab_key(self, module_name, tab_type, key, handler):
        """
        Associate a key binding to a handler only for a type of Tab.
        """
        keys = self.tab_keys[module_name]
        t = tab_type.__name__
        if key in tab_type.plugin_keys:
            return
        if t not in keys:
            keys[t] = []
        keys[t].append((key, handler))
        tab_type.plugin_keys[key] = handler
        for tab in self.core.tabs:
            if isinstance(tab, tab_type):
                tab.update_keys()

    def del_tab_key(self, module_name, tab_type, key):
        """
        Remove a key binding added through add_tab_key.
        """
        keys = self.tab_keys[module_name]
        t = tab_type.__name__
        if t not in keys:
            return
        for _key in keys[t]:
            if _key[0] == key:
                keys[t].remove(_key)
                del tab_type.plugin_keys[key]
                for tab in self.core.tabs:
                    if isinstance(tab, tab_type) and key in tab.key_func:
                        del tab.key_func[key]

    def add_key(self, module_name, key, handler):
        """
        Associate a global key binding to a handler, except if it
        already exists.
        """
        if key in self.core.key_func:
            raise Exception("Key '%s' already exists" % (key, ))
        keys = self.keys[module_name]
        keys[key] = handler
        self.core.key_func[key] = handler

    def del_key(self, module_name, key):
        """
        Remove a global key binding added by a plugin.
        """
        if key in self.keys[module_name]:
            del self.keys[module_name][key]
            if key in self.core.key_func:
                del self.core.commands[key]

    def add_event_handler(self, module_name, event_name, handler, *args, **kwargs):
        """
        Add an event handler. If event_name isn’t in the event list, assume
        it is a slixmpp event.
        """
        eh = self.event_handlers[module_name]
        eh.append((event_name, handler))
        if event_name in self.core.events.events:
            self.core.events.add_event_handler(event_name, handler, *args, **kwargs)
        else:
            self.core.xmpp.add_event_handler(event_name, handler)

    def del_event_handler(self, module_name, event_name, handler):
        """
        Remove an event handler if it exists.
        """
        if event_name in self.core.events.events:
            self.core.events.del_event_handler(None, handler)
        else:
            self.core.xmpp.del_event_handler(event_name, handler)
        eh = self.event_handlers[module_name]
        eh = [e for e in eh if e != (event_name, handler)]

    def completion_load(self, the_input):
        """
        completion function that completes the name of the plugins, from
        all .py files in plugins_dir
        """
        names = set()
        for path_ in self.load_path:
            try:
                add = set(os.listdir(path_))
                names |= add
            except OSError:
                pass
        plugins_files = [
            name[:-3] for name in names if name.endswith('.py')
            and name != '__init__.py' and not name.startswith('.')
        ]
        plugins_files.sort()
        position = the_input.get_argument_position(quoted=False)
        return Completion(
            the_input.new_completion,
            plugins_files,
            position,
            '',
            quotify=False)

    def completion_unload(self, the_input):
        """
        completion function that completes the name of loaded plugins
        """
        position = the_input.get_argument_position(quoted=False)
        return Completion(
            the_input.new_completion,
            sorted(self.plugins.keys()),
            position,
            '',
            quotify=False)

    def on_plugins_dir_change(self, _, new_value):
        self.plugins_dir = Path(new_value).expanduser()
        self.check_create_plugins_dir()
        self.fill_load_path()

    def on_plugins_conf_dir_change(self, _, new_value):
        self.plugins_conf_dir = Path(new_value).expanduser()
        self.check_create_plugins_conf_dir()

    def initial_set_plugins_conf_dir(self):
        """
        Create the plugins_conf_dir
        """
        plugins_conf_dir = config.get('plugins_conf_dir')
        self.plugins_conf_dir = Path(plugins_conf_dir).expanduser(
        ) if plugins_conf_dir else xdg.CONFIG_HOME / 'plugins'
        self.check_create_plugins_conf_dir()

    def check_create_plugins_conf_dir(self):
        """
        Create the plugins config directory if it does not exist.
        Returns True on success, False on failure.
        """
        if not os.access(str(self.plugins_conf_dir), os.R_OK | os.X_OK):
            try:
                self.plugins_conf_dir.mkdir(parents=True, exist_ok=True)
            except OSError:
                log.error(
                    'Unable to create the plugin conf dir: %s',
                    self.plugins_conf_dir,
                    exc_info=True)
                return False
        return True

    def initial_set_plugins_dir(self):
        """
        Set the plugins_dir on start
        """
        plugins_dir = config.get('plugins_dir')
        self.plugins_dir = Path(plugins_dir).expanduser(
        ) if plugins_dir else xdg.DATA_HOME / 'plugins'
        self.check_create_plugins_dir()

    def check_create_plugins_dir(self):
        """
        Create the plugins directory if it does not exist.
        Returns True on success, False on failure.
        """
        if not os.access(str(self.plugins_dir), os.R_OK | os.X_OK):
            try:
                self.plugins_dir.mkdir(parents=True, exist_ok=True)
            except OSError:
                log.error(
                    'Unable to create the plugins dir: %s',
                    self.plugins_dir,
                    exc_info=True)
                return False
        return True

    def fill_load_path(self):
        """
        Append the global packages and the source directory if available
        """

        self.load_path = []

        default_plugin_path = path.join(
            path.dirname(path.dirname(__file__)), 'plugins')

        if os.access(default_plugin_path, os.R_OK | os.X_OK):
            self.load_path.insert(0, default_plugin_path)

        if os.access(str(self.plugins_dir), os.R_OK | os.X_OK):
            self.load_path.append(str(self.plugins_dir))
