# Source code for helper

    import re

    from django.urls import NoReverseMatch, reverse
    from django.utils.safestring import mark_safe

    from crispy_forms.exceptions import FormHelpersException
    from crispy_forms.layout import Layout
    from crispy_forms.layout_slice import LayoutSlice
    from crispy_forms.utils import TEMPLATE_PACK, flatatt, list_difference, render_field

    class DynamicLayoutHandler:
        def _check_layout(self):
            if self.layout is None:
                raise FormHelpersException("You need to set a layout in your FormHelper")

        def _check_layout_and_form(self):
            self._check_layout()
            if self.form is None:
                raise FormHelpersException("You need to pass a form instance to your FormHelper")

        def all(self):
            """
            Returns all layout objects of first level of depth
            """
            self._check_layout()
            return LayoutSlice(self.layout, slice(0, len(self.layout.fields), 1))

        def filter(self, *LayoutClasses, max_level=0, greedy=False):
            """
            Returns a LayoutSlice pointing to layout objects of type `LayoutClass`
            """
            self._check_layout()
            filtered_layout_objects = self.layout.get_layout_objects(LayoutClasses, max_level=max_level, greedy=greedy)

            return LayoutSlice(self.layout, filtered_layout_objects)

        def filter_by_widget(self, widget_type):
            """
            Returns a LayoutSlice pointing to fields with widgets of `widget_type`
            """
            self._check_layout_and_form()
            layout_field_names = self.layout.get_field_names()

            # Let's filter all fields with widgets like widget_type
            filtered_fields = []
            for pointer in layout_field_names:
                if isinstance(self.form.fields[pointer.name].widget, widget_type):
                    filtered_fields.append(pointer)

            return LayoutSlice(self.layout, filtered_fields)

        def exclude_by_widget(self, widget_type):
            """
            Returns a LayoutSlice pointing to fields with widgets NOT matching `widget_type`
            """
            self._check_layout_and_form()
            layout_field_names = self.layout.get_field_names()

            # Let's exclude all fields with widgets like widget_type
            filtered_fields = []
            for pointer in layout_field_names:
                if not isinstance(self.form.fields[pointer.name].widget, widget_type):
                    filtered_fields.append(pointer)

            return LayoutSlice(self.layout, filtered_fields)

        def __getitem__(self, key):
            """
            Return a LayoutSlice that makes changes affect the current instance of the layout
            and not a copy.
            """
            # when key is a string containing the field name
            if isinstance(key, str):
                # Django templates access FormHelper attributes using dictionary [] operator
                # This could be a helper['form_id'] access, not looking for a field
                if hasattr(self, key):
                    return getattr(self, key)

                self._check_layout()
                layout_field_names = self.layout.get_field_names()

                filtered_field = []
                for pointer in layout_field_names:
                    # There can be an empty pointer
                    if pointer.name == key:
                        filtered_field.append(pointer)

                return LayoutSlice(self.layout, filtered_field)

            return LayoutSlice(self.layout, key)

        def __setitem__(self, key, value):
            self.layout[key] = value

        def __delitem__(self, key):
            del self.layout.fields[key]

        def __len__(self):
            if self.layout is not None:
                return len(self.layout.fields)
            else:
                return 0

    class FormHelper(DynamicLayoutHandler):
        """
        This class controls the form rendering behavior of the form passed to
        the `{% crispy %}` tag. For doing so you will need to set its attributes
        and pass the corresponding helper object to the tag::

            {% crispy form form.helper %}

        Let's see what attributes you can set and what form behaviors they apply to:

            **form_method**: Specifies form method attribute.
                You can set it to 'POST' or 'GET'. Defaults to 'POST'

            **form_action**: Applied to the form action attribute:
                - Can be a named url in your URLconf that can be executed via the `{% url %}` template tag. \
                Example: 'show_my_profile'. In your URLconf you could have something like::

                    path('show/profile/', 'show_my_profile_view', name = 'show_my_profile')

                - It can simply point to a URL '/whatever/blabla/'.

            **form_id**: Generates a form id for dom identification.
                If no id provided then no id attribute is created on the form.

            **form_class**: String containing separated CSS classes to be applied
                to form class attribute.

            **form_group_wrapper_class**: String containing separated CSS classes to be applied
                to each row of inputs.

            **form_tag**: It specifies if <form></form> tags should be rendered when using a Layout.
                If set to False it renders the form without the <form></form> tags. Defaults to True.

            **form_error_title**: If a form has `non_field_errors` to display, they
                are rendered in a div. You can set title's div with this attribute.
                Example: "Oooops!" or "Form Errors"

            **formset_error_title**: If a formset has `non_form_errors` to display, they
                are rendered in a div. You can set title's div with this attribute.

            **include_media**: Whether to automatically include form media. Set to False if
                you want to manually include form media outside the form. Defaults to True.

        Public Methods:

            **add_input(input)**: You can add input buttons using this method. Inputs
                added using this method will be rendered at the end of the form/formset.

            **add_layout(layout)**: You can add a `Layout` object to `FormHelper`. The Layout
                specifies in a simple, clean and DRY way how the form fields should be rendered.
                You can wrap fields, order them, customize pretty much anything in the form.

        Best way to add a helper to a form is adding a property named helper to the form
        that returns customized `FormHelper` object::

            from crispy_forms.helper import FormHelper
            from crispy_forms.layout import Submit

            class MyForm(forms.Form):
                title = forms.CharField(_("Title"))

                @property
                def helper(self):
                    helper = FormHelper()
                    helper.form_id = 'this-form-rocks'
                    helper.form_class = 'search'
                    helper.add_input(Submit('save', 'save'))
                    [...]
                    return helper

        You can use it in a template doing::

            {% load crispy_forms_tags %}
            {% crispy form %}
        """

        _form_method = "post"
        _form_action = ""

        form = None
        form_id = ""
        form_class = ""
        form_group_wrapper_class = ""
        layout = None
        form_tag = True
        form_error_title = ""
        formset_error_title = ""
        form_show_errors = True
        render_unmentioned_fields = False
        render_hidden_fields = False
        render_required_fields = False
        _help_text_inline = False
        _error_text_inline = True
        form_show_labels = True
        template = None
        field_template = None
        disable_csrf = False
        use_custom_control = True
        label_class = ""
        field_class = ""
        include_media = True

        def __init__(self, form=None):
            self.attrs = {}
            self.inputs = []

            if form is not None:
                self.form = form
                self.layout = self.build_default_layout(form)

        def build_default_layout(self, form):
            return Layout(*form.fields.keys())

        @property
        def form_method(self):
            return self._form_method

        @form_method.setter
        def form_method(self, method):
            if method.lower() not in ("get", "post"):
                raise FormHelpersException("Only GET and POST are valid in the \
                        form_method helper attribute")

            self._form_method = method.lower()

        @property
        def form_action(self):
            try:
                return reverse(self._form_action)
            except NoReverseMatch:
                return self._form_action

        @form_action.setter
        def form_action(self, action):
            self._form_action = action

        @property
        def help_text_inline(self):
            return self._help_text_inline

        @help_text_inline.setter
        def help_text_inline(self, flag):
            self._help_text_inline = flag
            self._error_text_inline = not flag

        @property
        def error_text_inline(self):
            return self._error_text_inline

        @error_text_inline.setter
        def error_text_inline(self, flag):
            self._error_text_inline = flag
            self._help_text_inline = not flag

        def add_input(self, input_object):
            self.inputs.append(input_object)

        def add_layout(self, layout):
            self.layout = layout

        def render_layout(self, form, context, template_pack=TEMPLATE_PACK):
            """
            Returns safe html of the rendering of the layout
            """
            form.rendered_fields = set()
            form.crispy_field_template = self.field_template

            # This renders the specified Layout strictly
            html = self.layout.render(form, context, template_pack=template_pack)

            # Rendering some extra fields if specified
            if self.render_unmentioned_fields or self.render_hidden_fields or self.render_required_fields:
                fields = tuple(form.fields.keys())
                left_fields_to_render = list_difference(fields, form.rendered_fields)
                for field in left_fields_to_render:
                    if (
                        self.render_unmentioned_fields
                        or (self.render_hidden_fields and form.fields[field].widget.is_hidden)
                        or (self.render_required_fields and form.fields[field].widget.is_required)
                    ):
                        html += render_field(field, form, context, template_pack=template_pack)

            return mark_safe(html)

        def get_attributes(self, template_pack=TEMPLATE_PACK):
            """
            Used by crispy_forms_tags to get helper attributes
            """
            attrs = self.attrs.copy() if self.attrs else {}
            if self.form_action:
                attrs["action"] = self.form_action.strip()
            if self.form_id:
                attrs["id"] = self.form_id.strip()
            if self.form_class:
                attrs["class"] = self.form_class.strip()
            if self.form_group_wrapper_class:
                attrs["form_group_wrapper_class"] = self.form_group_wrapper_class

            items = {
                "attrs": attrs,
                "disable_csrf": self.disable_csrf,
                "error_text_inline": self.error_text_inline,
                "field_class": self.field_class,
                "field_template": self.field_template or "%s/field.html" % template_pack,
                "flat_attrs": flatatt(attrs),
                "form_error_title": self.form_error_title.strip(),
                "form_method": self.form_method.strip(),
                "form_show_errors": self.form_show_errors,
                "form_show_labels": self.form_show_labels,
                "form_tag": self.form_tag,
                "formset_error_title": self.formset_error_title.strip(),
                "help_text_inline": self.help_text_inline,
                "include_media": self.include_media,
                "label_class": self.label_class,
                "use_custom_control": self.use_custom_control,
            }

            if template_pack == "bootstrap4":
                if "form-horizontal" in self.form_class.split():
                    bootstrap_size_match = re.findall(r"col(-(xl|lg|md|sm))?-(\d+)", self.label_class)
                    if bootstrap_size_match:
                        offset_pattern = "offset%s-%s"
                        items["bootstrap_checkbox_offsets"] = [
                            offset_pattern % (m[0], m[-1]) for m in bootstrap_size_match
                        ]
            else:
                bootstrap_size_match = re.findall(r"col-(lg|md|sm|xs)-(\d+)", self.label_class)
                if bootstrap_size_match:
                    offset_pattern = "col-%s-offset-%s"
                    items["bootstrap_checkbox_offsets"] = [offset_pattern % m for m in bootstrap_size_match]

            if self.inputs:
                items["inputs"] = self.inputs

            for attribute_name, value in self.__dict__.items():
                if (
                    attribute_name not in items
                    and attribute_name not in ["layout", "inputs"]
                    and not attribute_name.startswith("_")
                ):
                    items[attribute_name] = value

            return items