import collections
import inspect
from packaging import version

from django.apps import AppConfig
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.template.loader import get_template
from django.utils.module_loading import import_string

from extras.registry import registry
from utilities.choices import ButtonColorChoices


# Initialize plugin registry stores
registry['plugin_template_extensions'] = collections.defaultdict(list)
registry['plugin_menu_items'] = {}


#
# Plugin AppConfig class
#

class PluginConfig(AppConfig):
    """
    Subclass of Django's built-in AppConfig class, to be used for NetBox plugins.
    """
    # Plugin metadata
    author = ''
    author_email = ''
    description = ''
    version = ''

    # Root URL path under /plugins. If not set, the plugin's label will be used.
    base_url = None

    # Minimum/maximum compatible versions of NetBox
    min_version = None
    max_version = None

    # Default configuration parameters
    default_settings = {}

    # Mandatory configuration parameters
    required_settings = []

    # Middleware classes provided by the plugin
    middleware = []

    # Cacheops configuration. Cache all operations by default.
    caching_config = {
        '*': {'ops': 'all'},
    }

    # Default integration paths. Plugin authors can override these to customize the paths to
    # integrated components.
    template_extensions = 'template_content.template_extensions'
    menu_items = 'navigation.menu_items'

    def ready(self):

        # Register template content
        try:
            template_extensions = import_string(f"{self.__module__}.{self.template_extensions}")
            register_template_extensions(template_extensions)
        except ImportError:
            pass

        # Register navigation menu items (if defined)
        try:
            menu_items = import_string(f"{self.__module__}.{self.menu_items}")
            register_menu_items(self.verbose_name, menu_items)
        except ImportError:
            pass

    @classmethod
    def validate(cls, user_config):

        # Enforce version constraints
        current_version = version.parse(settings.VERSION)
        if cls.min_version is not None:
            min_version = version.parse(cls.min_version)
            if current_version < min_version:
                raise ImproperlyConfigured(
                    f"Plugin {cls.__module__} requires NetBox minimum version {cls.min_version}."
                )
        if cls.max_version is not None:
            max_version = version.parse(cls.max_version)
            if current_version > max_version:
                raise ImproperlyConfigured(
                    f"Plugin {cls.__module__} requires NetBox maximum version {cls.max_version}."
                )

        # Verify required configuration settings
        for setting in cls.required_settings:
            if setting not in user_config:
                raise ImproperlyConfigured(
                    f"Plugin {cls.__module__} requires '{setting}' to be present in the PLUGINS_CONFIG section of "
                    f"configuration.py."
                )

        # Apply default configuration values
        for setting, value in cls.default_settings.items():
            if setting not in user_config:
                user_config[setting] = value


#
# Template content injection
#

class PluginTemplateExtension:
    """
    This class is used to register plugin content to be injected into core NetBox templates. It contains methods
    that are overridden by plugin authors to return template content.

    The `model` attribute on the class defines the which model detail page this class renders content for. It
    should be set as a string in the form '<app_label>.<model_name>'. render() provides the following context data:

    * object - The object being viewed
    * request - The current request
    * settings - Global NetBox settings
    * config - Plugin-specific configuration parameters
    """
    model = None

    def __init__(self, context):
        self.context = context

    def render(self, template_name, extra_context=None):
        """
        Convenience method for rendering the specified Django template using the default context data. An additional
        context dictionary may be passed as `extra_context`.
        """
        if extra_context is None:
            extra_context = {}
        elif not isinstance(extra_context, dict):
            raise TypeError("extra_context must be a dictionary")

        return get_template(template_name).render({**self.context, **extra_context})

    def left_page(self):
        """
        Content that will be rendered on the left of the detail page view. Content should be returned as an
        HTML string. Note that content does not need to be marked as safe because this is automatically handled.
        """
        raise NotImplementedError

    def right_page(self):
        """
        Content that will be rendered on the right of the detail page view. Content should be returned as an
        HTML string. Note that content does not need to be marked as safe because this is automatically handled.
        """
        raise NotImplementedError

    def full_width_page(self):
        """
        Content that will be rendered within the full width of the detail page view. Content should be returned as an
        HTML string. Note that content does not need to be marked as safe because this is automatically handled.
        """
        raise NotImplementedError

    def buttons(self):
        """
        Buttons that will be rendered and added to the existing list of buttons on the detail page view. Content
        should be returned as an HTML string. Note that content does not need to be marked as safe because this is
        automatically handled.
        """
        raise NotImplementedError


def register_template_extensions(class_list):
    """
    Register a list of PluginTemplateExtension classes
    """
    # Validation
    for template_extension in class_list:
        if not inspect.isclass(template_extension):
            raise TypeError(f"PluginTemplateExtension class {template_extension} was passes as an instance!")
        if not issubclass(template_extension, PluginTemplateExtension):
            raise TypeError(f"{template_extension} is not a subclass of extras.plugins.PluginTemplateExtension!")
        if template_extension.model is None:
            raise TypeError(f"PluginTemplateExtension class {template_extension} does not define a valid model!")

        registry['plugin_template_extensions'][template_extension.model].append(template_extension)


#
# Navigation menu links
#

class PluginMenuItem:
    """
    This class represents a navigation menu item. This constitutes primary link and its text, but also allows for
    specifying additional link buttons that appear to the right of the item in the van menu.

    Links are specified as Django reverse URL strings.
    Buttons are each specified as a list of PluginMenuButton instances.
    """
    permissions = []
    buttons = []

    def __init__(self, link, link_text, permissions=None, buttons=None):
        self.link = link
        self.link_text = link_text
        if permissions is not None:
            if type(permissions) not in (list, tuple):
                raise TypeError("Permissions must be passed as a tuple or list.")
            self.permissions = permissions
        if buttons is not None:
            if type(buttons) not in (list, tuple):
                raise TypeError("Buttons must be passed as a tuple or list.")
            self.buttons = buttons


class PluginMenuButton:
    """
    This class represents a button within a PluginMenuItem. Note that button colors should come from
    ButtonColorChoices.
    """
    color = ButtonColorChoices.DEFAULT
    permissions = []

    def __init__(self, link, title, icon_class, color=None, permissions=None):
        self.link = link
        self.title = title
        self.icon_class = icon_class
        if permissions is not None:
            if type(permissions) not in (list, tuple):
                raise TypeError("Permissions must be passed as a tuple or list.")
            self.permissions = permissions
        if color is not None:
            if color not in ButtonColorChoices.values():
                raise ValueError("Button color must be a choice within ButtonColorChoices.")
            self.color = color


def register_menu_items(section_name, class_list):
    """
    Register a list of PluginMenuItem instances for a given menu section (e.g. plugin name)
    """
    # Validation
    for menu_link in class_list:
        if not isinstance(menu_link, PluginMenuItem):
            raise TypeError(f"{menu_link} must be an instance of extras.plugins.PluginMenuItem")
        for button in menu_link.buttons:
            if not isinstance(button, PluginMenuButton):
                raise TypeError(f"{button} must be an instance of extras.plugins.PluginMenuButton")

    registry['plugin_menu_items'][section_name] = class_list
