from collections import OrderedDict
import inspect
import pkgutil

from django import forms
from django.conf import settings
from django.core.validators import RegexValidator

from .constants import LOG_DEFAULT, LOG_FAILURE, LOG_INFO, LOG_SUCCESS, LOG_WARNING
from .forms import ScriptForm


__all__ = [
    'Script',
    'StringVar',
    'IntegerVar',
    'BooleanVar',
    'ObjectVar',
]


class OptionalBooleanField(forms.BooleanField):
    required = False


#
# Script variables
#

class ScriptVariable:
    """
    Base model for script variables
    """
    form_field = forms.CharField

    def __init__(self, label='', description='', default=None, required=True):

        # Default field attributes
        self.field_attrs = {
            'help_text': description,
            'required': required
        }
        if label:
            self.field_attrs['label'] = label
        if default:
            self.field_attrs['initial'] = default

    def as_field(self):
        """
        Render the variable as a Django form field.
        """
        return self.form_field(**self.field_attrs)


class StringVar(ScriptVariable):
    """
    Character string representation. Can enforce minimum/maximum length and/or regex validation.
    """
    def __init__(self, min_length=None, max_length=None, regex=None, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # Optional minimum/maximum lengths
        if min_length:
            self.field_attrs['min_length'] = min_length
        if max_length:
            self.field_attrs['max_length'] = max_length

        # Optional regular expression validation
        if regex:
            self.field_attrs['validators'] = [
                RegexValidator(
                    regex=regex,
                    message='Invalid value. Must match regex: {}'.format(regex),
                    code='invalid'
                )
            ]


class IntegerVar(ScriptVariable):
    """
    Integer representation. Can enforce minimum/maximum values.
    """
    form_field = forms.IntegerField

    def __init__(self, min_value=None, max_value=None, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # Optional minimum/maximum values
        if min_value:
            self.field_attrs['min_value'] = min_value
        if max_value:
            self.field_attrs['max_value'] = max_value


class BooleanVar(ScriptVariable):
    """
    Boolean representation (true/false). Renders as a checkbox.
    """
    form_field = OptionalBooleanField


class ObjectVar(ScriptVariable):
    """
    NetBox object representation. The provided QuerySet will determine the choices available.
    """
    form_field = forms.ModelChoiceField

    def __init__(self, queryset, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # Queryset for field choices
        self.field_attrs['queryset'] = queryset


class Script:
    """
    Custom scripts inherit this object.
    """
    def __init__(self):

        # Initiate the log
        self.log = []

        # Grab some info about the script
        self.filename = inspect.getfile(self.__class__)
        self.source = inspect.getsource(self.__class__)

    def __str__(self):
        if hasattr(self, 'script_name'):
            return self.script_name
        return self.__class__.__name__

    def _get_vars(self):
        vars = OrderedDict()

        # Infer order from script_fields (Python 3.5 and lower)
        if hasattr(self, 'script_fields'):
            for name in self.script_fields:
                vars[name] = getattr(self, name)

        # Default to order of declaration on class
        for name, attr in self.__class__.__dict__.items():
            if name not in vars and issubclass(attr.__class__, ScriptVariable):
                vars[name] = attr

        return vars

    def run(self, data):
        raise NotImplementedError("The script must define a run() method.")

    def as_form(self, data=None):
        """
        Return a Django form suitable for populating the context data required to run this Script.
        """
        vars = self._get_vars()
        form = ScriptForm(vars, data)

        return form

    # Logging

    def log_debug(self, message):
        self.log.append((LOG_DEFAULT, message))

    def log_success(self, message):
        self.log.append((LOG_SUCCESS, message))

    def log_info(self, message):
        self.log.append((LOG_INFO, message))

    def log_warning(self, message):
        self.log.append((LOG_WARNING, message))

    def log_failure(self, message):
        self.log.append((LOG_FAILURE, message))


#
# Functions
#

def is_script(obj):
    """
    Returns True if the object is a Script.
    """
    return obj in Script.__subclasses__()


def is_variable(obj):
    """
    Returns True if the object is a ScriptVariable.
    """
    return isinstance(obj, ScriptVariable)


def get_scripts():
    scripts = OrderedDict()

    # Iterate through all modules within the reports path. These are the user-created files in which reports are
    # defined.
    for importer, module_name, _ in pkgutil.iter_modules([settings.SCRIPTS_ROOT]):
        module = importer.find_module(module_name).load_module(module_name)
        module_scripts = OrderedDict()
        for name, cls in inspect.getmembers(module, is_script):
            module_scripts[name] = cls
        scripts[module_name] = module_scripts

    return scripts