from flask import flash, redirect, request, url_for
from flask_admin import AdminIndexView, BaseView, expose
from flask_admin.contrib.sqla import ModelView
from flask_admin.helpers import get_form_data
from flask_admin.model.helpers import get_mdict_item_or_list
from flask_login import current_user
from sqlalchemy import func, select

from .exceptions import DatabaseException, ModelViewException
from .model_independent_funs import reportBadAttempt
from .models import Assistant, ExperimentMark, GroupExperiment, SemesterExperiment, db


def adminViewIsAccessible():
    return current_user.has_role("admin")


def assistantViewIsAccessible():
    return current_user.has_role("assistant")


def get_url(kwargs):
    url = kwargs["url"]
    if "/" in url:
        raise ModelViewException("url can not contain a slash!")

    return url


class CustomIndexView(AdminIndexView):
    def inaccessible_callback(self, name, **kwargs):
        # Redirect to login page if user doesn't have access
        return redirect(url_for("security.login", next=request.url))


class SecureAdminIndexView(CustomIndexView):
    def is_accessible(self):
        return adminViewIsAccessible()

    @expose("/")
    def index(self):
        assistants_num_missing = db.session.execute(
            select(Assistant, func.count())
            .join(Assistant.semester_experiments)
            .where(SemesterExperiment.semester == current_user.active_semester)
            .join(SemesterExperiment.group_experiments)
            .where(GroupExperiment.experiment_marks_missing is True)
            .join(GroupExperiment.experiment_marks)
            .where(ExperimentMark.final_experiment_mark is None)
            .group_by(Assistant.id)
            .order_by(func.count().desc())
        )

        return self.render(
            "admin_index.jinja.html",
            assistants_num_missing=assistants_num_missing,
        )


class SecureAssistantIndexView(CustomIndexView):
    def is_accessible(self):
        return assistantViewIsAccessible()

    @expose("/")
    def index(self):
        number_of_missing_final_experiment_marks = db.session.scalar(
            select(func.count())
            .select_from(ExperimentMark)
            .join(GroupExperiment)
            .join(SemesterExperiment)
            .where(SemesterExperiment.semester == current_user.active_semester)
            .join(SemesterExperiment.assistants)
            .where(Assistant.user == current_user)
            .where(ExperimentMark.final_experiment_mark is None)
        )

        return self.render(
            "assistant_index.jinja.html",
            number_of_missing_final_experiment_marks=number_of_missing_final_experiment_marks,
        )


class CustomModelView(ModelView):
    create_modal = True
    edit_modal = True
    details_modal = True

    can_view_details = False

    refreshFiltersCache = False

    # Should not be a copy of column_formatters
    # because of link formatting.
    column_formatters_export: dict = {}

    # Used in the UserView because of create_user
    # Should not be touched in other views
    _skip_session_addition_on_model_creation = False

    @expose("/")
    def index_view(self):
        if self.refreshFiltersCache:
            # Update filter options
            self._refresh_filters_cache()

        return super().index_view()

    def inaccessible_callback(self, name, **kwargs):
        # Redirect to login page if user doesn't have access
        return redirect(url_for("security.login", next=request.url))

    def query_modifier(self, query):
        return query

    def get_query(self):
        return self.query_modifier(super().get_query())

    def get_count_query(self):
        return self.query_modifier(super().get_count_query())

    def handle_view_exception(self, exc):
        if type(exc) in (ModelViewException, DatabaseException):
            flash(str(exc), "error")
            return True

        return super().handle_view_exception(exc)

    def customCreateModel(self, form):
        model = self.build_new_instance()
        form.populate_obj(model)
        return model

    def create_model(self, form):
        try:
            model = self.customCreateModel(form)

            if not self._skip_session_addition_on_model_creation:
                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(str(ex), "error")

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

    def customUpdateModel(self, form, model):
        """
        Return True if something changed during update, False otherwise.
        """
        form.populate_obj(model)
        # No way to know if something changed. Therefore, return True anyway.
        return True

    def update_model(self, form, model):
        try:
            if self.customUpdateModel(form, model) is False:
                # Nothing changed
                return True

            self.on_model_change(form, model, False)
            self.session.commit()
        except Exception as ex:
            if not self.handle_view_exception(ex):
                flash(str(ex), "error")

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

    def create_form(self, obj=None):
        if hasattr(self, "CreateForm"):
            formClass = self.CreateForm
        elif hasattr(self, "CreateAndEditForm"):
            formClass = self.CreateAndEditForm
        else:
            return super().create_form(obj)

        return formClass(get_form_data(), obj=obj)

    def edit_form(self, obj=None):
        if hasattr(self, "EditForm"):
            formClass = self.EditForm
        elif hasattr(self, "CreateAndEditForm"):
            formClass = self.CreateAndEditForm
        else:
            return super().edit_form(obj)

        return formClass(get_form_data(), obj=obj)

    def get_export_columns(self):
        # Use column_details_list instead of column_list

        only_columns = self.column_export_list or self.column_details_list or self.scaffold_list_columns()

        return self.get_column_names(
            only_columns=only_columns,
            excluded_columns=self.column_export_exclude_list,
        )


class SecureAdminModelView(CustomModelView):
    can_export = True
    can_set_page_size = True

    can_create = True
    can_edit = True
    can_delete = True
    column_display_actions = True
    can_view_details = True

    list_template = "admin_list.jinja.html"
    create_template = "admin_create.jinja.html"
    edit_template = "admin_edit.jinja.html"
    details_template = "admin_details.jinja.html"

    def __init__(self, model, **kwargs):
        url = get_url(kwargs)
        super().__init__(model, db.session, endpoint="admin_" + url, category="Tables", **kwargs)

    def is_accessible(self):
        return adminViewIsAccessible()


class SecureAssistantModelView(CustomModelView):
    can_export = False
    can_set_page_size = False

    can_edit = False
    column_display_actions = False

    list_template = "assistant_list.jinja.html"
    create_template = "assistant_create.jinja.html"
    edit_template = "assistant_edit.jinja.html"
    details_template = "assistant_details.jinja.html"

    """
    SECURITY NOTES:
    - Every variable and method defined below in this class is NOT ALLOWED TO BE (completely) OVERWRITTEN!
    You can only extend the predefined methods.
    - The method query_modifier(self, query) has to be implemented!
    """

    # Assistants are not allowed to create or delete.
    can_create = False
    can_delete = False

    def __init__(self, model, **kwargs):
        url = get_url(kwargs)
        super().__init__(model, db.session, endpoint="assistant_" + url, **kwargs)

    def is_accessible(self):
        return assistantViewIsAccessible()

    def query_modifier(self, query):
        """
        A default query modifier has to be implemented to restrict assistant's read/write access.
        See on_model_change!
        """
        raise NotImplementedError()

    def on_model_change(self, form, model, is_created):
        """
        This method uses the modified query returned by query_modifier (which has to be implemented!) to prevent assistants
        from modifying models not listed on their view by sending a POST request with a different id.
        You can extend this method by implementing a custom on_model_change and then calling super().on_model_change within it.
        """
        if is_created:
            reportBadAttempt("An assistant tried to create a model!")
            raise ModelViewException("Assistants can not create models!")

        if model not in self.get_query():
            reportBadAttempt("An assistant tried to change a model not in his filter!")
            self.handle_view_exception(ModelViewException("Unauthorized action!"))
            return redirect(self.url)

        return None

    def on_model_delete(self, model):
        reportBadAttempt("An assistant tried to delete a model!")
        raise ModelViewException("Assistants can not delete models!")

    @expose("/edit/", methods=("GET", "POST"))
    def edit_view(self):
        """
        Prevent an assistant from seeing the edit form of a model not in his filter by using the GET method and entering an id.
        This is important if can_edit is set to True.
        """
        id = get_mdict_item_or_list(request.args, "id")

        if id is not None:
            model = self.get_one(id)

            if model not in self.get_query():
                reportBadAttempt("An assistant tried to edit a model not in his filter!")
                self.handle_view_exception(ModelViewException("Unauthorized action!"))
                return redirect(self.url)

        return super().edit_view()

    @expose("/details/")
    def details_view(self):
        """
        Prevent an assistant from seeing the details of a model not in his filter by using the GET method and entering an id.
        This is important if can_view_details is set to True.
        """
        id = get_mdict_item_or_list(request.args, "id")

        if id is not None:
            model = self.get_one(id)

            if model not in self.get_query():
                reportBadAttempt("An assistant tried to see details of a model not in his filter!")
                self.handle_view_exception(ModelViewException("Unauthorized action!"))
                return redirect(self.url)

        return super().details_view()

    def get_details_columns(self):
        """
        Prevent showing unintended data if can_view_details is set to True and column_details_list was not set (which equals None).
        """
        if not self.column_details_list:
            self.column_details_list = self.column_list

        return super().get_details_columns()


class CustomBaseView(BaseView):
    def inaccessible_callback(self, name, **kwargs):
        # Redirect to login page if user doesn't have access
        return redirect(url_for("security.login", next=request.url))


class SecureAdminBaseView(CustomBaseView):
    def __init__(self, **kwargs):
        url = get_url(kwargs)
        super().__init__(endpoint="admin_" + url, **kwargs)

    def is_accessible(self):
        return adminViewIsAccessible()


class SecureAssistantBaseView(CustomBaseView):
    def __init__(self, **kwargs):
        url = get_url(kwargs)
        super().__init__(endpoint="assistant_" + url, **kwargs)

    def is_accessible(self):
        return assistantViewIsAccessible()