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


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

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

    def __init__(self, name, fields, options=None, bases=None, managers=None):
        self.name = name
        self.fields = fields
        self.options = options or {}
        self.bases = bases or (models.Model,)
        self.managers = managers or []

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

    def deconstruct(self):
        kwargs = {
            'name': self.name,
            'fields': self.fields,
        }
        if self.options:
            kwargs['options'] = self.options
        if self.bases and self.bases != (models.Model,):
            kwargs['bases'] = self.bases
        if self.managers and self.managers != [('objects', models.Manager())]:
            kwargs['managers'] = self.managers
        return (
            self.__class__.__name__,
            [],
            kwargs
        )

    def state_forwards(self, app_label, state):
        state.add_model(ModelState(
            app_label,
            self.name,
            list(self.fields),
            dict(self.options),
            tuple(self.bases),
            list(self.managers),
        ))

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        model = to_state.apps.get_model(app_label, self.name)
        if self.allow_migrate_model(schema_editor.connection.alias, model):
            schema_editor.create_model(model)

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        model = from_state.apps.get_model(app_label, self.name)
        if self.allow_migrate_model(schema_editor.connection.alias, model):
            schema_editor.delete_model(model)

    def describe(self):
        return "Create %smodel %s" % ("proxy " if self.options.get("proxy", False) else "", self.name)

    def references_model(self, name, app_label=None):
        strings_to_check = [self.name]
        # Check we didn't inherit from the model
        for base in self.bases:
            if isinstance(base, six.string_types):
                strings_to_check.append(base.split(".")[-1])
        # Check we have no FKs/M2Ms with it
        for fname, field in self.fields:
            if field.remote_field:
                if isinstance(field.remote_field.model, six.string_types):
                    strings_to_check.append(field.remote_field.model.split(".")[-1])
        # Now go over all the strings and compare them
        for string in strings_to_check:
            if string.lower() == name.lower():
                return True
        return False


class DeleteModel(Operation):
    """
    Drops a model's table.
    """

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

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

    def deconstruct(self):
        kwargs = {
            'name': self.name,
        }
        return (
            self.__class__.__name__,
            [],
            kwargs
        )

    def state_forwards(self, app_label, state):
        state.remove_model(app_label, self.name_lower)

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        model = from_state.apps.get_model(app_label, self.name)
        if self.allow_migrate_model(schema_editor.connection.alias, model):
            schema_editor.delete_model(model)

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        model = to_state.apps.get_model(app_label, self.name)
        if self.allow_migrate_model(schema_editor.connection.alias, model):
            schema_editor.create_model(model)

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

    def describe(self):
        return "Delete model %s" % (self.name, )


class RenameModel(Operation):
    """
    Renames a model.
    """

    def __init__(self, old_name, new_name):
        self.old_name = old_name
        self.new_name = new_name

    @cached_property
    def old_name_lower(self):
        return self.old_name.lower()

    @cached_property
    def new_name_lower(self):
        return self.new_name.lower()

    def deconstruct(self):
        kwargs = {
            'old_name': self.old_name,
            'new_name': self.new_name,
        }
        return (
            self.__class__.__name__,
            [],
            kwargs
        )

    def state_forwards(self, app_label, state):
        apps = state.apps
        model = apps.get_model(app_label, self.old_name)
        model._meta.apps = apps
        # Get all of the related objects we need to repoint
        all_related_objects = (
            f for f in model._meta.get_fields(include_hidden=True)
            if f.auto_created and not f.concrete and (not f.hidden or f.many_to_many)
        )
        # Rename the model
        state.models[app_label, self.new_name_lower] = state.models[app_label, self.old_name_lower]
        state.models[app_label, self.new_name_lower].name = self.new_name
        state.remove_model(app_label, self.old_name_lower)
        # Repoint the FKs and M2Ms pointing to us
        for related_object in all_related_objects:
            if related_object.model is not model:
                # The model being renamed does not participate in this relation
                # directly. Rather, a superclass does.
                continue
            # Use the new related key for self referential related objects.
            if related_object.related_model == model:
                related_key = (app_label, self.new_name_lower)
            else:
                related_key = (
                    related_object.related_model._meta.app_label,
                    related_object.related_model._meta.model_name,
                )
            new_fields = []
            for name, field in state.models[related_key].fields:
                if name == related_object.field.name:
                    field = field.clone()
                    field.remote_field.model = "%s.%s" % (app_label, self.new_name)
                new_fields.append((name, field))
            state.models[related_key].fields = new_fields
            state.reload_model(*related_key)
        state.reload_model(app_label, self.new_name_lower)

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        new_model = to_state.apps.get_model(app_label, self.new_name)
        if self.allow_migrate_model(schema_editor.connection.alias, new_model):
            old_model = from_state.apps.get_model(app_label, self.old_name)
            # Move the main table
            schema_editor.alter_db_table(
                new_model,
                old_model._meta.db_table,
                new_model._meta.db_table,
            )
            # Alter the fields pointing to us
            for related_object in old_model._meta.related_objects:
                if related_object.related_model == old_model:
                    model = new_model
                    related_key = (app_label, self.new_name_lower)
                else:
                    model = related_object.related_model
                    related_key = (
                        related_object.related_model._meta.app_label,
                        related_object.related_model._meta.model_name,
                    )
                to_field = to_state.apps.get_model(
                    *related_key
                )._meta.get_field(related_object.field.name)
                schema_editor.alter_field(
                    model,
                    related_object.field,
                    to_field,
                )
            # Rename M2M fields whose name is based on this model's name.
            fields = zip(old_model._meta.local_many_to_many, new_model._meta.local_many_to_many)
            for (old_field, new_field) in fields:
                # Skip self-referential fields as these are renamed above.
                if new_field.model == new_field.related_model or not new_field.remote_field.through._meta.auto_created:
                    continue
                # Rename the M2M table that's based on this model's name.
                old_m2m_model = old_field.remote_field.through
                new_m2m_model = new_field.remote_field.through
                schema_editor.alter_db_table(
                    new_m2m_model,
                    old_m2m_model._meta.db_table,
                    new_m2m_model._meta.db_table,
                )
                # Rename the column in the M2M table that's based on this
                # model's name.
                schema_editor.alter_field(
                    new_m2m_model,
                    old_m2m_model._meta.get_field(old_model._meta.model_name),
                    new_m2m_model._meta.get_field(new_model._meta.model_name),
                )

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        self.new_name_lower, self.old_name_lower = self.old_name_lower, self.new_name_lower
        self.new_name, self.old_name = self.old_name, self.new_name

        self.database_forwards(app_label, schema_editor, from_state, to_state)

        self.new_name_lower, self.old_name_lower = self.old_name_lower, self.new_name_lower
        self.new_name, self.old_name = self.old_name, self.new_name

    def references_model(self, name, app_label=None):
        return (
            name.lower() == self.old_name_lower or
            name.lower() == self.new_name_lower
        )

    def describe(self):
        return "Rename model %s to %s" % (self.old_name, self.new_name)


class AlterModelTable(Operation):
    """
    Renames a model's table
    """

    def __init__(self, name, table):
        self.name = name
        self.table = table

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

    def deconstruct(self):
        kwargs = {
            'name': self.name,
            'table': self.table,
        }
        return (
            self.__class__.__name__,
            [],
            kwargs
        )

    def state_forwards(self, app_label, state):
        state.models[app_label, self.name_lower].options["db_table"] = self.table
        state.reload_model(app_label, self.name_lower)

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        new_model = to_state.apps.get_model(app_label, self.name)
        if self.allow_migrate_model(schema_editor.connection.alias, new_model):
            old_model = from_state.apps.get_model(app_label, self.name)
            schema_editor.alter_db_table(
                new_model,
                old_model._meta.db_table,
                new_model._meta.db_table,
            )
            # Rename M2M fields whose name is based on this model's db_table
            for (old_field, new_field) in zip(old_model._meta.local_many_to_many, new_model._meta.local_many_to_many):
                if new_field.remote_field.through._meta.auto_created:
                    schema_editor.alter_db_table(
                        new_field.remote_field.through,
                        old_field.remote_field.through._meta.db_table,
                        new_field.remote_field.through._meta.db_table,
                    )

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        return self.database_forwards(app_label, schema_editor, from_state, to_state)

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

    def describe(self):
        return "Rename table for %s to %s" % (self.name, self.table)


class AlterUniqueTogether(Operation):
    """
    Changes the value of unique_together to the target one.
    Input value of unique_together must be a set of tuples.
    """
    option_name = "unique_together"

    def __init__(self, name, unique_together):
        self.name = name
        unique_together = normalize_together(unique_together)
        self.unique_together = set(tuple(cons) for cons in unique_together)

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

    def deconstruct(self):
        kwargs = {
            'name': self.name,
            'unique_together': self.unique_together,
        }
        return (
            self.__class__.__name__,
            [],
            kwargs
        )