import importlib
import os
import sys

from django.db.models.loading import cache
from django.utils import datetime_safe
from django.utils.six.moves import input
from django.core.exceptions import ImproperlyConfigured


class MigrationQuestioner(object):
    """
    Gives the autodetector responses to questions it might have.
    This base class has a built-in noninteractive mode, but the
    interactive subclass is what the command-line arguments will use.
    """

    def __init__(self, defaults=None, specified_apps=None):
        self.defaults = defaults or {}
        self.specified_apps = specified_apps or set()

    def ask_initial(self, app_label):
        "Should we create an initial migration for the app?"
        # If it was specified on the command line, definitely true
        if app_label in self.specified_apps:
            return True
        # Otherwise, we look to see if it has a migrations module
        # without any Python files in it, apart from __init__.py.
        # Apps from the new app template will have these; the python
        # file check will ensure we skip South ones.
        try:
            models_module = cache.get_app(app_label)
        except ImproperlyConfigured:  # It's a fake app
            return self.defaults.get("ask_initial", False)
        migrations_import_path = "%s.migrations" % models_module.__package__
        try:
            migrations_module = importlib.import_module(migrations_import_path)
        except ImportError:
            return self.defaults.get("ask_initial", False)
        else:
            filenames = os.listdir(os.path.dirname(migrations_module.__file__))
            return not any(x.endswith(".py") for x in filenames if x != "__init__.py")

    def ask_not_null_addition(self, field_name, model_name):
        "Adding a NOT NULL field to a model"
        # None means quit
        return None

    def ask_rename(self, model_name, old_name, new_name, field_instance):
        "Was this field really renamed?"
        return self.defaults.get("ask_rename", False)

    def ask_merge(self, app_label):
        "Do you really want to merge these migrations?"
        return self.defaults.get("ask_merge", False)


class InteractiveMigrationQuestioner(MigrationQuestioner):

    def _boolean_input(self, question, default=None):
        result = input("%s " % question)
        if not result and default is not None:
            return default
        while len(result) < 1 or result[0].lower() not in "yn":
            result = input("Please answer yes or no: ")
        return result[0].lower() == "y"

    def _choice_input(self, question, choices):
        print(question)
        for i, choice in enumerate(choices):
            print(" %s) %s" % (i + 1, choice))
        result = input("Select an option: ")
        while True:
            try:
                value = int(result)
                if 0 < value <= len(choices):
                    return value
            except ValueError:
                pass
            result = input("Please select a valid option: ")

    def ask_not_null_addition(self, field_name, model_name):
        "Adding a NOT NULL field to a model"
        choice = self._choice_input(
            "You are trying to add a non-nullable field '%s' to %s without a default;\n" % (field_name, model_name) +
            "we can't do that (the database needs something to populate existing rows).\n" +
            "Please select a fix:",
            [
                "Provide a one-off default now (will be set on all existing rows)",
                "Quit, and let me add a default in models.py",
            ]
        )
        if choice == 2:
            sys.exit(3)
        else:
            print("Please enter the default value now, as valid Python")
            print("The datetime module is available, so you can do e.g. datetime.date.today()")
            while True:
                code = input(">>> ")
                if not code:
                    print("Please enter some code, or 'exit' (with no quotes) to exit.")
                elif code == "exit":
                    sys.exit(1)
                else:
                    try:
                        return eval(code, {}, {"datetime": datetime_safe})
                    except (SyntaxError, NameError) as e:
                        print("Invalid input: %s" % e)

    def ask_rename(self, model_name, old_name, new_name, field_instance):
        "Was this field really renamed?"
        return self._boolean_input("Did you rename %s.%s to %s.%s (a %s)? [y/N]" % (model_name, old_name, model_name, new_name, field_instance.__class__.__name__), False)

    def ask_merge(self, app_label):
        return self._boolean_input(
            "\nMerging will only work if the operations printed above do not conflict\n" +
            "with each other (working on different fields or models)\n" +
            "Do you want to merge these migration branches? [y/N]",
            False,
        )