from __future__ import unicode_literals

from django.db import models
from django.db.migrations.operations.base import Operation
from django.db.migrations.state import ModelState
from django.db.models.options import normalize_together
from django.utils import six
from django.utils.functional import cached_property

from .fields import (
    AddField, AlterField, FieldOperation, RemoveField, RenameField,
)


def _check_for_duplicates(arg_name, objs):
    used_vals = set()
    for val in objs:
        if val in used_vals:
            raise ValueError(
                "Found duplicate value %s in CreateModel %s argument." % (val, arg_name)
            )
        used_vals.add(val)


class ModelOperation(Operation):
    def __init__(self, name):
        self.name = name

    @cached_property
    def name_lower(self):
        return self.name.lower()

    def references_model(self, name, app_label=None):
        return name.lower() == self.name_lower

    def reduce(self, operation, in_between, app_label=None):
        return (
            super(ModelOperation, self).reduce(operation, in_between, app_label=app_label) or
            not operation.references_model(self.name, app_label)
        )


class CreateModel(ModelOperation):
    """
    Create a model's table.
    """

    serialization_expand_args = ['fields', 'options', 'managers']

    def __init__(self, name, fields, options=None, bases=None, managers=None):
        self.fields = fields
        self.options = options or {}
        self.bases = bases or (models.Model,)
        self.managers = managers or []
        super(CreateModel, self).__init__(name)
        # Sanity-check that there are no duplicated field names, bases, or
        # manager names
        _check_for_duplicates('fields', (name for name, _ in self.fields))
        _check_for_duplicates('bases', (