import logging
import warnings
import inspect

from sqlalchemy.orm.attributes import InstrumentedAttribute
from sqlalchemy.orm import joinedload, aliased
from sqlalchemy.sql.expression import desc, ColumnElement
from sqlalchemy import Boolean, Table, func, or_
from sqlalchemy.exc import IntegrityError
from sqlalchemy.sql.expression import cast
from sqlalchemy import Unicode

from flask import flash

from flask_admin._compat import string_types, text_type
from flask_admin.babel import gettext, ngettext, lazy_gettext
from flask_admin.model import BaseModelView
from flask_admin.model.form import wrap_fields_in_fieldlist
from flask_admin.model.fields import ListEditableFieldList

from flask_admin.actions import action
from flask_admin._backwards import ObsoleteAttr

from flask_admin.contrib.sqla import form, filters as sqla_filters, tools
from .typefmt import DEFAULT_FORMATTERS
from .tools import get_query_for_ids
from .ajax import create_ajax_loader

# Set up logger
log = logging.getLogger("flask-admin.sqla")


class ModelView(BaseModelView):
    """
        SQLAlchemy model view

        Usage sample::

            admin = Admin()
            admin.add_view(ModelView(User, db.session))
    """

    column_auto_select_related = ObsoleteAttr('column_auto_select_related',
                                              'auto_select_related',
                                              True)
    """
        Enable automatic detection of displayed foreign keys in this view
        and perform automatic joined loading for related models to improve
        query performance.

        Please note that detection is not recursive: if `__unicode__` method
        of related model uses another model to generate string representation, it
        will still make separate database call.
    """

    column_select_related_list = ObsoleteAttr('column_select_related',
                                             'list_select_related',
                                              None)
    """
        List of parameters for SQLAlchemy `subqueryload`. Overrides `column_auto_select_related`
        property.

        For example::

            class PostAdmin(ModelView):
                column_select_related_list = ('user', 'city')

        You can also use properties::

            class PostAdmin(ModelView):
                column_select_related_list = (Post.user, Post.city)

        Please refer to the `subqueryload` on list of possible values.
    """

    column_display_all_relations = ObsoleteAttr('column_display_all_relations',
                                                'list_display_all_relations',
                                                False)
    """
        Controls if list view should display all relations, not only many-to-one.
    """

    column_searchable_list = ObsoleteAttr('column_searchable_list',
                                          'searchable_columns',
                                          None)
    """
        Collection of the searchable columns.

        Example::

            class MyModelView(ModelView):
                column_searchable_list = ('name', 'email')

        You can also pass columns::

            class MyModelView(ModelView):
                column_searchable_list = (User.name, User.email)

        The following search rules apply:

        - If you enter ``ZZZ`` in the UI search field, it will generate ``ILIKE '%ZZZ%'``
          statement against searchable columns.

        - If you enter multiple words, each word will be searched separately, but
          only rows that contain all words will be displayed. For example, searching
          for ``abc def`` will find all rows that contain ``abc`` and ``def`` in one or
          more columns.

        - If you prefix your search term with ``^``, it will find all rows
          that start with ``^``. So, if you entered ``^ZZZ`` then ``ILIKE 'ZZZ%'`` will be used.

        - If you prefix your search term with ``=``, it will perform an exact match.
          For example, if you entered ``=ZZZ``, the statement ``ILIKE 'ZZZ'`` will be used.
    """

    column_filters = None
    """
        Collection of the column filters.

        Can contain either field names or instances of
        :class:`flask_admin.contrib.sqla.filters.BaseSQLAFilter` classes.

        Filters will be grouped by name when displayed in the drop-down.

        For example::

            class MyModelView(BaseModelView):
                column_filters = ('user', 'email')

        or::

            from flask_admin.contrib.sqla.filters import BooleanEqualFilter

            class MyModelView(BaseModelView):
                column_filters = (BooleanEqualFilter(column=User.name, name='Name'),)

        or::

            from flask_admin.contrib.sqla.filters import BaseSQLAFilter

            class FilterLastNameBrown(BaseSQLAFilter):
                def apply(self, query, value, alias=None):
                    if value == '1':
                        return query.filter(self.column == "Brown")
                    else:
                        return query.filter(self.column != "Brown")

                def operation(self):
                    return 'is Brown'

            class MyModelView(BaseModelView):
                column_filters = [
                    FilterLastNameBrown(
                        User.last_name, 'Last Name', options=(('1', 'Yes'), ('0', 'No'))
                    )
                ]
    """

    model_form_converter = form.AdminModelConverter
    """
        Model form conversion class. Use this to implement custom field conversion logic.

        For example::

            class MyModelConverter(AdminModelConverter):
                pass


            class MyAdminView(ModelView):
                model_form_converter = MyModelConverter
    """

    inline_model_form_converter = form.InlineModelConverter
    """
        Inline model conversion class. If you need some kind of post-processing for inline
        forms, you can customize behavior by doing something like this::

            class MyInlineModelConverter(InlineModelConverter):
                def post_process(self, form_class, info):
                    form_class.value = wtf.StringField('value')
                    return form_class

            class MyAdminView(ModelView):
                inline_model_form_converter = MyInlineModelConverter
    """

    filter_converter = sqla_filters.FilterConverter()
    """
        Field to filter converter.

        Override this attribute to use non-default converter.
    """

    fast_mass_delete = False
    """
        If set to `False` and user deletes more than one model using built in action,
        all models will be read from the database and then deleted one by one
        giving SQLAlchemy a chance to manually cleanup any dependencies (many-to-many
        relationships, etc).

        If set to `True`, will run a ``DELETE`` statement which is somewhat faster,
        but may leave corrupted data if you forget to configure ``DELETE
        CASCADE`` for your model.
    """

    inline_models = None
    """
        Inline related-model editing for models with parent-child relations.

        Accepts enumerable with one of the following possible values:

        1. Child model class::

            class MyModelView(ModelView):
                inline_models = (Post,)

        2. Child model class and additional options::

            class MyModelView(ModelView):
                inline_models = [(Post, dict(form_columns=['title']))]

        3. Django-like ``InlineFormAdmin`` class instance::

            class MyInlineModelForm(InlineFormAdmin):
                form_columns = ('title', 'date')

            class MyModelView(ModelView):
                inline_models = (MyInlineModelForm(MyInlineModel),)

        You can customize the generated field name by:

        1. Using the `form_name` property as a key to the options dictionary::

            class MyModelView(ModelView):
                inline_models = ((Post, dict(form_label='Hello')))

        2. Using forward relation name and `column_labels` property::

            class Model1(Base):
                pass

            class Model2(Base):
                # ...
                model1 = relation(Model1, backref='models')

            class MyModel1View(Base):
                inline_models = (Model2,)
                column_labels = {'models': 'Hello'}
    """

    column_type_formatters = DEFAULT_FORMATTERS

    form_choices = None
    """
        Map choices to form fields

        Example::

            class MyModelView(BaseModelView):
                form_choices = {'my_form_field': [
                    ('db_value', 'display_value'),
                ]}
    """

    form_optional_types = (Boolean,)
    """
        List of field types that should be optional if column is not nullable.

        Example::

            class MyModelView(BaseModelView):
                form_optional_types = (Boolean, Unicode)
    """

    def __init__(self, model, session,
                 name=None, category=None, endpoint=None, url=None, static_folder=None,
                 menu_class_name=None, menu_icon_type=None, menu_icon_value=None):
        """
            Constructor.

            :param model:
                Model class
            :param session:
                SQLAlchemy session
            :param name:
                View name. If not set, defaults to the model name
            :param category:
                Category name
            :param endpoint:
                Endpoint name. If not set, defaults to the model name
            :param url:
                Base URL. If not set, defaults to '/admin/' + endpoint
            :param menu_class_name:
                Optional class name for the menu item.
            :param menu_icon_type:
                Optional icon. Possible icon types:

                 - `flask_admin.consts.ICON_TYPE_GLYPH` - Bootstrap glyph icon
                 - `flask_admin.consts.ICON_TYPE_FONT_AWESOME` - Font Awesome icon
                 - `flask_admin.consts.ICON_TYPE_IMAGE` - Image relative to Flask static directory
                 - `flask_admin.consts.ICON_TYPE_IMAGE_URL` - Image with full URL
            :param menu_icon_value:
                Icon glyph name or URL, depending on `menu_icon_type` setting
        """
        self.session = session

        self._search_fields = None

        self._filter_joins = dict()

        self._sortable_joins = dict()

        if self.form_choices is None:
            self.form_choices = {}

        super(ModelView, self).__init__(model, name, category, endpoint, url, static_folder,
                                        menu_class_name=menu_class_name,
                                        menu_icon_type=menu_icon_type,
                                        menu_icon_value=menu_icon_value)

        # Primary key
        self._primary_key = self.scaffold_pk()

        if self._primary_key is None:
            raise Exception('Model %s does not have primary key.' % self.model.__name__)

        # Configuration
        if not self.column_select_related_list:
            self._auto_joins = self.scaffold_auto_joins()
        else:
            self._auto_joins = self.column_select_related_list

    # Internal API
    def _get_model_iterator(self, model=None):
        """
            Return property iterator for the model
        """
        if model is None:
            model = self.model

        return model._sa_class_manager.mapper.iterate_properties

    def _get_columns_for_field(self, field):
        if (not field or
            not hasattr(field, 'property') or
            not hasattr(field.property, 'columns') or
            not field.property.columns):
                raise Exception('Invalid field %s: does not contains any columns.' % field)

        return field.property.columns

    def _get_field_with_path(self, name):
        """
            Resolve property by name and figure out its join path.

            Join path might contain both properties and tables.
        """
        path = []

        model = self.model

        # For strings, resolve path
        if isinstance(name, string_types):
            for attribute in name.split('.'):
                value = getattr(model, attribute)

                if (hasattr(value, 'property') and
                        hasattr(value.property, 'direction')):
                    model = value.property.mapper.class_

                    table = model.__table__

                    if self._need_join(table):
                        path.append(value)

                attr = value
        else:
            attr = name

            # Determine joins if table.column (relation object) is provided
            if isinstance(attr, InstrumentedAttribute):
                columns = self._get_columns_for_field(attr)

                if len(columns) > 1:
                    raise Exception('Can only handle one column for %s' % name)

                column = columns[0]

                # TODO: Use SQLAlchemy "path-finder" to find exact join path to the target property
                if self._need_join(column.table):
                    path.append(column.table)

        return attr, path

    def _need_join(self, table):
        """
            Check if join to a table is necessary.
        """
        return table not in self.model._sa_class_manager.mapper.tables

    def _apply_path_joins(self, query, joins, path, inner_join=True):
        """
            Apply join path to the query.

            :param query:
                Query to add joins to
            :param joins:
                List of current joins. Used to avoid joining on same relationship more than once
            :param path:
                Path to be joined
            :param fn:
                Join function
        """
        last = None

        if path:
            for item in path:
                key = (inner_join, item)
                alias = joins.get(key)

                if key not in joins:
                    if not isinstance(item, Table):
                        alias = aliased(item.property.mapper.class_)

                    fn = query.join if inner_join else query.outerjoin

                    if last is None:
                        query = fn(item) if alias is None else fn(alias, item)
                    else:
                        prop = getattr(last, item.key)
                        query = fn(prop) if alias is None else fn(alias, prop)

                    joins[key] = alias

                last = alias

        return query, joins, last

    # Scaffolding
    def scaffold_pk(self):
        """
            Return the primary key name(s) from a model
            If model has single primary key, will return a string and tuple otherwise
        """
        return tools.get_primary_key(self.model)

    def get_pk_value(self, model):
        """
            Return the primary key value from a model object.
            If there are multiple primary keys, they're encoded into string representation.
        """
        if isinstance(self._primary_key, tuple):
            return tools.iterencode(getattr(model, attr) for attr in self._primary_key)
        else:
            return tools.escape(getattr(model, self._primary_key))

    def scaffold_list_columns(self):
        """
            Return a list of columns from the model.
        """
        columns = []

        for p in self._get_model_iterator():
            if hasattr(p, 'direction'):
                if self.column_display_all_relations or p.direction.name == 'MANYTOONE':
                    columns.append(p.key)
            elif hasattr(p, 'columns'):
                if len(p.columns) > 1:
                    filtered = tools.filter_foreign_columns(self.model.__table__, p.columns)

                    if len(filtered) > 1:
                        warnings.warn('Can not convert multiple-column properties (%s.%s)' % (self.model, p.key))
                        continue

                    column = filtered[0]
                else:
                    column = p.columns[0]

                if column.foreign_keys:
                    continue

                if not self.column_display_pk and column.primary_key:
                    continue

                columns.append(p.key)

        return columns

    def scaffold_sortable_columns(self):
        """
            Return a dictionary of sortable columns.
            Key is column name, value is sort column/field.
        """
        columns = dict()

        for p in self._get_model_iterator():
            if hasattr(p, 'columns'):
                # Sanity check
                if len(p.columns) > 1:
                    # Multi-column properties are not supported
                    continue

                column = p.columns[0]

                # Can't sort on primary or foreign keys by default
                if column.foreign_keys:
                    continue

                if not self.column_display_pk and column.primary_key:
                    continue

                columns[p.key] = column

        return columns

    def get_sortable_columns(self):
        """
            Returns a dictionary of the sortable columns. Key is a model
            field name and value is sort column (for example - attribute).

            If `column_sortable_list` is set, will use it. Otherwise, will call
            `scaffold_sortable_columns` to get them from the model.
        """
        self._sortable_joins = dict()

        if self.column_sortable_list is None:
            return self.scaffold_sortable_columns()
        else:
            result = dict()

            for c in self.column_sortable_list:
                if isinstance(c, tuple):
                    column, path = self._get_field_with_path(c[1])
                    column_name = c[0]
                elif isinstance(c, InstrumentedAttribute):
                    column, path = self._get_field_with_path(c)
                    column_name = str(c)
                else:
                    column, path = self._get_field_with_path(c)
                    column_name = c

                result[column_name] = column

                if path:
                    self._sortable_joins[column_name] = path

            return result

    def init_search(self):
        """
            Initialize search. Returns `True` if search is supported for this
            view.

            For SQLAlchemy, this will initialize internal fields: list of
            column objects used for filtering, etc.
        """
        if self.column_searchable_list:
            self._search_fields = []

            for p in self.column_searchable_list:
                attr, joins = self._get_field_with_path(p)

                if not attr:
                    raise Exception('Failed to find field for search field: %s' % p)

                for column in self._get_columns_for_field(attr):
                    self._search_fields.append((column, joins))

        return bool(self.column_searchable_list)

    def scaffold_filters(self, name):
        """
            Return list of enabled filters
        """

        attr, joins = self._get_field_with_path(name)

        if attr is None:
            raise Exception('Failed to find field for filter: %s' % name)

        # Figure out filters for related column, unless it's a hybrid_property
        if isinstance(attr, ColumnElement):
            warnings.warn(('Unable to scaffold the filter for %s, scaffolding '
                           'for hybrid_property is not supported yet.') % name)
        elif hasattr(attr, 'property') and hasattr(attr.property, 'direction'):
            filters = []

            for p in self._get_model_iterator(attr.property.mapper.class_):
                if hasattr(p, 'columns'):
                    # TODO: Check for multiple columns
                    column = p.columns[0]

                    if column.foreign_keys or column.primary_key:
                        continue

                    visible_name = '%s / %s' % (self.get_column_name(attr.prop.table.name),
                                                self.get_column_name(p.key))

                    type_name = type(column.type).__name__
                    flt = self.filter_converter.convert(type_name,
                                                        column,
                                                        visible_name)

                    if flt:
                        table = column.table

                        if joins:
                            self._filter_joins[column] = joins
                        elif self._need_join(table):
                            self._filter_joins[column] = [table]

                        filters.extend(flt)

            return filters
        else:
            columns = self._get_columns_for_field(attr)

            if len(columns) > 1:
                raise Exception('Can not filter more than on one column for %s' % name)

            column = columns[0]

            if self._need_join(column.table) and name not in self.column_labels:
                visible_name = '%s / %s' % (
                    self.get_column_name(column.table.name),
                    self.get_column_name(column.name)
                )
            else:
                if not isinstance(name, string_types):
                    visible_name = self.get_column_name(name.property.key)
                else:
                    visible_name = self.get_column_name(name)

            type_name = type(column.type).__name__

            flt = self.filter_converter.convert(
                type_name,
                column,
                visible_name,
                options=self.column_choices.get(name),
            )

            if joins:
                self._filter_joins[column] = joins
            elif self._need_join(column.table):
                self._filter_joins[column] = [column.table]

            return flt

    def handle_filter(self, filter):
        if isinstance(filter, sqla_filters.BaseSQLAFilter):
            column = filter.column

            # hybrid_property joins are not supported yet
            if (isinstance(column, InstrumentedAttribute) and
                    self._need_join(column.table)):
                self._filter_joins[column] = [column.table]

        return filter

    def scaffold_form(self):
        """
            Create form from the model.
        """
        converter = self.model_form_converter(self.session, self)
        form_class = form.get_form(self.model, converter,
                                   base_class=self.form_base_class,
                                   only=self.form_columns,
                                   exclude=self.form_excluded_columns,
                                   field_args=self.form_args,
                                   extra_fields=self.form_extra_fields)

        if self.inline_models:
            form_class = self.scaffold_inline_form_models(form_class)

        return form_class

    def scaffold_list_form(self, custom_fieldlist=ListEditableFieldList,
                           validators=None):
        """
            Create form for the `index_view` using only the columns from
            `self.column_editable_list`.

            :param validators:
                `form_args` dict with only validators
                {'name': {'validators': [required()]}}
            :param custom_fieldlist:
                A WTForm FieldList class. By default, `ListEditableFieldList`.
        """
        converter = self.model_form_converter(self.session, self)
        form_class = form.get_form(self.model, converter,
                                   base_class=self.form_base_class,
                                   only=self.column_editable_list,
                                   field_args=validators)

        return wrap_fields_in_fieldlist(self.form_base_class,
                                        form_class,
                                        custom_fieldlist)

    def scaffold_inline_form_models(self, form_class):
        """
            Contribute inline models to the form

            :param form_class:
                Form class
        """
        inline_converter = self.inline_model_form_converter(self.session,
                                                            self,
                                                            self.model_form_converter)

        for m in self.inline_models:
            form_class = inline_converter.contribute(self.model, form_class, m)

        return form_class

    def scaffold_auto_joins(self):
        """
            Return a list of joined tables by going through the
            displayed columns.
        """
        if not self.column_auto_select_related:
            return []

        relations = set()

        for p in self._get_model_iterator():
            if hasattr(p, 'direction'):
                # Check if it is pointing to same model
                if p.mapper.class_ == self.model:
                    continue

                if p.direction.name in ['MANYTOONE', 'MANYTOMANY']:
                    relations.add(p.key)

        joined = []

        for prop, name in self._list_columns:
            if prop in relations:
                joined.append(getattr(self.model, prop))

        return joined

    # AJAX foreignkey support
    def _create_ajax_loader(self, name, options):
        return create_ajax_loader(self.model, self.session, name, name, options)

    # Database-related API
    def get_query(self):
        """
            Return a query for the model type.

            If you override this method, don't forget to override `get_count_query` as well.

            This method can be used to set a "persistent filter" on an index_view.

            Example::

                class MyView(ModelView):
                    def get_query(self):
                        return super(MyView, self).get_query().filter(User.username == current_user.username)
        """
        return self.session.query(self.model)

    def get_count_query(self):
        """
            Return a the count query for the model type

            A ``query(self.model).count()`` approach produces an excessive
            subquery, so ``query(func.count('*'))`` should be used instead.

            See commit ``#45a2723`` for details.
        """
        return self.session.query(func.count('*')).select_from(self.model)

    def _order_by(self, query, joins, sort_joins, sort_field, sort_desc):
        """
            Apply order_by to the query

            :param query:
                Query
            :pram joins:
                Current joins
            :param sort_joins:
                Sort joins (properties or tables)
            :param sort_field:
                Sort field
            :param sort_desc:
                Ascending or descending
        """
        if sort_field is not None:
            # Handle joins
            query, joins, alias = self._apply_path_joins(query, joins, sort_joins, inner_join=False)

            column = sort_field if alias is None else getattr(alias, sort_field.key)

            if sort_desc:
                query = query.order_by(desc(column))
            else:
                query = query.order_by(column)

        return query, joins

    def _get_default_order(self):
        order = super(ModelView, self)._get_default_order()

        if order is not None:
            field, direction = order

            attr, joins = self._get_field_with_path(field)

            return attr, joins, direction

        return None

    def _apply_sorting(self, query, joins, sort_column, sort_desc):
        if sort_column is not None:
            if sort_column in self._sortable_columns:
                sort_field = self._sortable_columns[sort_column]
                sort_joins = self._sortable_joins.get(sort_column)

                query, joins = self._order_by(query, joins, sort_joins, sort_field, sort_desc)
        else:
            order = self._get_default_order()

            if order:
                sort_field, sort_joins, sort_desc = order

                query, joins = self._order_by(query, joins, sort_joins, sort_field, sort_desc)

        return query, joins

    def _apply_search(self, query, count_query, joins, count_joins, search):
        """
            Apply search to a query.
        """
        terms = search.split(' ')

        for term in terms:
            if not term:
                continue

            stmt = tools.parse_like_term(term)

            filter_stmt = []
            count_filter_stmt = []

            for field, path in self._search_fields:
                query, joins, alias = self._apply_path_joins(query, joins, path, inner_join=False)

                count_alias = None

                if count_query is not None:
                    count_query, count_joins, count_alias = self._apply_path_joins(count_query,
                                                                                   count_joins,
                                                                                   path,
                                                                                   inner_join=False)

                column = field if alias is None else getattr(alias, field.key)
                filter_stmt.append(cast(column, Unicode).ilike(stmt))

                if count_filter_stmt is not None:
                    column = field if count_alias is None else getattr(count_alias, field.key)
                    count_filter_stmt.append(cast(column, Unicode).ilike(stmt))

            query = query.filter(or_(*filter_stmt))

            if count_query is not None:
                count_query = count_query.filter(or_(*count_filter_stmt))

        return query, count_query, joins, count_joins

    def _apply_filters(self, query, count_query, joins, count_joins, filters):
        for idx, flt_name, value in filters:
            flt = self._filters[idx]

            alias = None
            count_alias = None

            # Figure out joins
            if isinstance(flt, sqla_filters.BaseSQLAFilter):
                path = self._filter_joins.get(flt.column, [])

                query, joins, alias = self._apply_path_joins(query, joins, path, inner_join=False)

                if count_query is not None:
                    count_query, count_joins, count_alias = self._apply_path_joins(
                        count_query,
                        count_joins,
                        path,
                        inner_join=False)

            # Clean value .clean() and apply the filter
            clean_value = flt.clean(value)

            try:
                query = flt.apply(query, clean_value, alias)
            except TypeError:
                spec = inspect.getargspec(flt.apply)

                if len(spec.args) == 3:
                    warnings.warn('Please update your custom filter %s to include additional `alias` parameter.' % repr(flt))
                else:
                    raise

                query = flt.apply(query, clean_value)

            if count_query is not None:
                try:
                    count_query = flt.apply(count_query, clean_value, count_alias)
                except TypeError:
                    count_query = flt.apply(count_query, clean_value)

        return query, count_query, joins, count_joins

    def _apply_pagination(self, query, page, page_size):
        if page_size is None:
            page_size = self.page_size

        if page_size:
            query = query.limit(page_size)

        if page and page_size:
            query = query.offset(page * page_size)

        return query

    def get_list(self, page, sort_column, sort_desc, search, filters,
                 execute=True, page_size=None):
        """
            Return records from the database.

            :param page:
                Page number
            :param sort_column:
                Sort column name
            :param sort_desc:
                Descending or ascending sort
            :param search:
                Search query
            :param execute:
                Execute query immediately? Default is `True`
            :param filters:
                List of filter tuples
            :param page_size:
                Number of results. Defaults to ModelView's page_size. Can be
                overriden to change the page_size limit. Removing the page_size
                limit requires setting page_size to 0 or False.
        """

        # Will contain join paths with optional aliased object
        joins = {}
        count_joins = {}

        query = self.get_query()
        count_query = self.get_count_query() if not self.simple_list_pager else None

        # Ignore eager-loaded relations (prevent unnecessary joins)
        # TODO: Separate join detection for query and count query?
        if hasattr(query, '_join_entities'):
            for entity in query._join_entities:
                for table in entity.tables:
                    joins[table] = None

        # Apply search criteria
        if self._search_supported and search:
            query, count_query, joins, count_joins = self._apply_search(query,
                                                                        count_query,
                                                                        joins,
                                                                        count_joins,
                                                                        search)

        # Apply filters
        if filters and self._filters:
            query, count_query, joins, count_joins = self._apply_filters(query,
                                                                         count_query,
                                                                         joins,
                                                                         count_joins,
                                                                         filters)

        # Calculate number of rows if necessary
        count = count_query.scalar() if count_query else None

        # Auto join
        for j in self._auto_joins:
            query = query.options(joinedload(j))

        # Sorting
        query, joins = self._apply_sorting(query, joins, sort_column, sort_desc)

        # Pagination
        query = self._apply_pagination(query, page, page_size)

        # Execute if needed
        if execute:
            query = query.all()

        return count, query

    def get_one(self, id):
        """
            Return a single model by its id.

            :param id:
                Model id
        """
        return self.session.query(self.model).get(tools.iterdecode(id))

    # Error handler
    def handle_view_exception(self, exc):
        if isinstance(exc, IntegrityError):
            flash(gettext('Integrity error. %(message)s', message=text_type(exc)), 'error')
            return True

        return super(ModelView, self).handle_view_exception(exc)

    # Model handlers
    def create_model(self, form):
        """
            Create model from form.

            :param form:
                Form instance
        """
        try:
            model = self.model()
            form.populate_obj(model)
            self.session.add(model)
            self._on_model_change(form, model, True)
            self.session.commit()
        except Exception as ex:
            if not self.handle_view_exception(ex):
                flash(gettext('Failed to create record. %(error)s', error=str(ex)), 'error')
                log.exception('Failed to create record.')

            self.session.rollback()

            return False
        else:
            self.after_model_change(form, model, True)

        return model

    def update_model(self, form, model):
        """
            Update model from form.

            :param form:
                Form instance
            :param model:
                Model instance
        """
        try:
            form.populate_obj(model)
            self._on_model_change(form, model, False)
            self.session.commit()
        except Exception as ex:
            if not self.handle_view_exception(ex):
                flash(gettext('Failed to update record. %(error)s', error=str(ex)), 'error')
                log.exception('Failed to update record.')

            self.session.rollback()

            return False
        else:
            self.after_model_change(form, model, False)

        return True

    def delete_model(self, model):
        """
            Delete model.

            :param model:
                Model to delete
        """
        try:
            self.on_model_delete(model)
            self.session.flush()
            self.session.delete(model)
            self.session.commit()
        except Exception as ex:
            if not self.handle_view_exception(ex):
                flash(gettext('Failed to delete record. %(error)s', error=str(ex)), 'error')
                log.exception('Failed to delete record.')

            self.session.rollback()

            return False
        else:
            self.after_model_delete(model)

        return True

    # Default model actions
    def is_action_allowed(self, name):
        # Check delete action permission
        if name == 'delete' and not self.can_delete:
            return False

        return super(ModelView, self).is_action_allowed(name)

    @action('delete',
            lazy_gettext('Delete'),
            lazy_gettext('Are you sure you want to delete selected records?'))
    def action_delete(self, ids):
        try:
            query = get_query_for_ids(self.get_query(), self.model, ids)

            if self.fast_mass_delete:
                count = query.delete(synchronize_session=False)
            else:
                count = 0

                for m in query.all():
                    if self.delete_model(m):
                        count += 1

            self.session.commit()

            flash(ngettext('Record was successfully deleted.',
                           '%(count)s records were successfully deleted.',
                           count,
                           count=count))
        except Exception as ex:
            if not self.handle_view_exception(ex):
                raise

            flash(gettext('Failed to delete records. %(error)s', error=str(ex)), 'error')
