from __future__ import unicode_literals

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


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

    serialization_expand_args = ['fields', 'options']

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

    def state_forwards(self, app_label, state):
        state.models[app_label, self.name.lower()] = ModelState(
            app_label,
            self.name,
            list(self.fields),
            dict(self.options),
            tuple(self.bases),
        )

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

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        apps = from_state.render()
        model = apps.get_model(app_label, self.name)
        if self.allowed_to_migrate(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.rel:
                if isinstance(field.rel.to, six.string_types):
                    strings_to_check.append(field.rel.to.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

    def __eq__(self, other):
        return (
            (self.__class__ == other.__class__) and
            (self.name == other.name) and
            (self.options == other.options) and
            (self.bases == other.bases) and
            ([(k, f.deconstruct()[1:]) for k, f in self.fields] == [(k, f.deconstruct()[1:]) for k, f in other.fields])
        )


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

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

    def state_forwards(self, app_label, state):
        del state.models[app_label, self.name.lower()]

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

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        apps = to_state.render()
        model = apps.get_model(app_label, self.name)
        if self.allowed_to_migrate(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.
    """

    reversible = False

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

    def state_forwards(self, app_label, state):
        # Get all of the related objects we need to repoint
        apps = state.render(skip_cache=True)
        model = apps.get_model(app_label, self.old_name)
        related_objects = model._meta.get_all_related_objects()
        related_m2m_objects = model._meta.get_all_related_many_to_many_objects()
        # 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
        del state.models[app_label, self.old_name.lower()]
        # Repoint the FKs and M2Ms pointing to us
        for related_object in (related_objects + related_m2m_objects):
            related_key = (
                related_object.model._meta.app_label,
                related_object.model._meta.object_name.lower(),
            )
            new_fields = []
            for name, field in state.models[related_key].fields:
                if name == related_object.field.name:
                    field = field.clone()
                    field.rel.to = "%s.%s" % (app_label, self.new_name)
                new_fields.append((name, field))
            state.models[related_key].fields = new_fields

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        old_apps = from_state.render()
        new_apps = to_state.render()
        old_model = old_apps.get_model(app_label, self.old_name)
        new_model = new_apps.get_model(app_label, self.new_name)
        if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
            # 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
            related_objects = old_model._meta.get_all_related_objects()
            related_m2m_objects = old_model._meta.get_all_related_many_to_many_objects()
            for related_object in (related_objects + related_m2m_objects):
                to_field = new_apps.get_model(
                    related_object.model._meta.app_label,
                    related_object.model._meta.object_name.lower(),
                )._meta.get_field_by_name(related_object.field.name)[0]
                schema_editor.alter_field(
                    related_object.model,
                    related_object.field,
                    to_field,
                )

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        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, 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

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

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        old_apps = from_state.render()
        new_apps = to_state.render()
        old_model = old_apps.get_model(app_label, self.name)
        new_model = new_apps.get_model(app_label, self.name)
        if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
            schema_editor.alter_db_table(
                new_model,
                old_model._meta.db_table,
                new_model._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)
        # need None rather than an empty set to prevent infinite migrations
        # after removing unique_together from a model
        self.unique_together = set(tuple(cons) for cons in unique_together) or None

    def state_forwards(self, app_label, state):
        model_state = state.models[app_label, self.name.lower()]
        model_state.options[self.option_name] = self.unique_together

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        old_apps = from_state.render()
        new_apps = to_state.render()
        old_model = old_apps.get_model(app_label, self.name)
        new_model = new_apps.get_model(app_label, self.name)
        if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
            schema_editor.alter_unique_together(
                new_model,
                getattr(old_model._meta, self.option_name, set()),
                getattr(new_model._meta, self.option_name, set()),
            )

    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 "Alter %s for %s (%s constraint(s))" % (self.option_name, self.name, len(self.unique_together or ''))


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

    def __init__(self, name, index_together):
        self.name = name
        index_together = normalize_together(index_together)
        # need None rather than an empty set to prevent infinite migrations
        # after removing unique_together from a model
        self.index_together = set(tuple(cons) for cons in index_together) or None

    def state_forwards(self, app_label, state):
        model_state = state.models[app_label, self.name.lower()]
        model_state.options[self.option_name] = self.index_together

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        old_apps = from_state.render()
        new_apps = to_state.render()
        old_model = old_apps.get_model(app_label, self.name)
        new_model = new_apps.get_model(app_label, self.name)
        if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
            schema_editor.alter_index_together(
                new_model,
                getattr(old_model._meta, self.option_name, set()),
                getattr(new_model._meta, self.option_name, set()),
            )

    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 "Alter %s for %s (%s constraint(s))" % (self.option_name, self.name, len(self.index_together or ''))


class AlterOrderWithRespectTo(Operation):
    """
    Represents a change with the order_with_respect_to option.
    """

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

    def state_forwards(self, app_label, state):
        model_state = state.models[app_label, self.name.lower()]
        model_state.options['order_with_respect_to'] = self.order_with_respect_to

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        from_model = from_state.render().get_model(app_label, self.name)
        to_model = to_state.render().get_model(app_label, self.name)
        if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
            # Remove a field if we need to
            if from_model._meta.order_with_respect_to and not to_model._meta.order_with_respect_to:
                schema_editor.remove_field(from_model, from_model._meta.get_field_by_name("_order")[0])
            # Add a field if we need to (altering the column is untouched as
            # it's likely a rename)
            elif to_model._meta.order_with_respect_to and not from_model._meta.order_with_respect_to:
                field = to_model._meta.get_field_by_name("_order")[0]
                schema_editor.add_field(
                    from_model,
                    field,
                )

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        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 "Set order_with_respect_to on %s to %s" % (self.name, self.order_with_respect_to)


class AlterModelOptions(Operation):
    """
    Sets new model options that don't directly affect the database schema
    (like verbose_name, permissions, ordering). Python code in migrations
    may still need them.
    """

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

    def state_forwards(self, app_label, state):
        model_state = state.models[app_label, self.name.lower()]
        model_state.options = dict(model_state.options)
        model_state.options.update(self.options)

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        pass

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        pass

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

    def describe(self):
        return "Change Meta options on %s" % (self.name, )
