views.py

# -*- coding: utf-8 -*-

from __future__ import division

__copyright__ = "Copyright (C) 2014 Andreas Kloeckner"

__license__ = """
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
"""

from django.shortcuts import (  # noqa
        render, get_object_or_404, redirect)
from django.contrib import messages
import django.forms as forms
from django.core.exceptions import PermissionDenied, SuspiciousOperation
from crispy_forms.helper import FormHelper
from crispy_forms.layout import Submit
from django.conf import settings
from django.contrib.auth.decorators import login_required
from django.contrib.auth.forms import \
        AuthenticationForm as AuthenticationFormBase
from django.core.urlresolvers import reverse

import datetime

from course.models import (
        UserStatus, user_status,
        Course, course_validation_state, Participation,
        FlowAccessException,
        FlowVisit,
        participation_role, participation_status)

from course.content import (
        get_course_repo, get_course_desc, parse_date_spec,
        get_flow_desc
        )


def get_role_and_participation(request, course):
    # "wake up" lazy object
    # http://stackoverflow.com/questions/20534577/int-argument-must-be-a-string-or-a-number-not-simplelazyobject  # noqa
    user = (request.user._wrapped
            if hasattr(request.user, '_wrapped')
            else request.user)

    if not user.is_authenticated():
        return participation_role.unenrolled, None

    participations = list(Participation.objects.filter(
            user=user, course=course))

    # The uniqueness constraint should have ensured that.
    assert len(participations) <= 1

    if len(participations) == 0:
        return participation_role.unenrolled, None

    participation = participations[0]
    if participation.status != participation_status.active:
        return participation_role.unenrolled, participation
    else:
        if participation.temporary_role:
            return participation.temporary_role, participation
        else:
            return participation.role, participation


def get_active_commit_sha(course, participation):
    sha = course.active_git_commit_sha

    if participation is not None and participation.preview_git_commit_sha:
        sha = participation.preview_git_commit_sha

    return sha.encode()


def get_flow_permissions(course_desc, participation, role, flow_id, flow_desc):
    now = datetime.datetime.now().date()

    # {{{ scan for exceptions in database

    for exc in (
            FlowAccessException.objects
            .filter(participation=participation, flow_id=flow_id)
            .order_by("expiration")):

        if exc.expiration is not None and exc.expiration < now:
            continue

        stipulations = exc.stipulations
        if not isinstance(stipulations, dict):
            stipulations = {}
        from course.content import dict_to_struct
        stipulations = dict_to_struct(exc.stipulations)

        return (
                [entry.permission for entry in exc.entries.all()],
                stipulations
                )

    # }}}

    # {{{ interpret flow rules

    for rule in flow_desc.access_rules:
        if hasattr(rule, "roles"):
            if role not in rule.roles:
                continue

        if hasattr(rule, "start"):
            start_date = parse_date_spec(course_desc, rule.start)
            if now < start_date:
                continue

        if hasattr(rule, "end"):
            end_date = parse_date_spec(course_desc, rule.end)
            if end_date < now:
                continue

        return rule.permissions, rule

    # }}}

    raise ValueError("Flow access rules of flow '%s' did not resolve "
            "to access answer for '%s'" % (flow_id, participation))


# {{{ views

def home(request):
    courses_and_descs_and_invalid_flags = []
    for course in Course.objects.all():
        repo = get_course_repo(course)
        desc = get_course_desc(repo, course.active_git_commit_sha.encode())

        role, participation = get_role_and_participation(request, course)

        show = True
        if course.hidden:
            if role not in [participation_role.teaching_assistant,
                    participation_role.instructor]:
                show = False

        if course.validation_state != course_validation_state.valid:
            if role != participation_role.instructor:
                show = False

        if show:
            courses_and_descs_and_invalid_flags.append(
                    (course, desc,
                        course.validation_state != course_validation_state.valid))

    def course_sort_key(entry):
        course, desc, invalid_flag = entry
        return desc.course_start

    courses_and_descs_and_invalid_flags.sort(key=course_sort_key)

    return render(request, "course/home.html", {
        "courses_and_descs_and_invalid_flags": courses_and_descs_and_invalid_flags
        })


# {{{ conventional login

class LoginForm(AuthenticationFormBase):
    def __init__(self, *args, **kwargs):
        self.helper = FormHelper()
        self.helper.form_tag = False
        self.helper.label_class = "col-lg-2"
        self.helper.field_class = "col-lg-8"
        self.helper.field_class = "col-lg-8"

        self.helper.add_input(Submit("submit", "Sign in",
            css_class="col-lg-offset-2"))

        super(LoginForm, self).__init__(*args, **kwargs)


def sign_in(request):
    from django.contrib.auth.views import login
    return login(request, template_name="course/login.html",
            authentication_form=LoginForm)

# }}}


# {{{ email sign-in flow

class SignInByEmailForm(forms.Form):
    email = forms.EmailField(required=True)

    def __init__(self, *args, **kwargs):
        self.helper = FormHelper()
        self.helper.form_class = "form-horizontal"
        self.helper.label_class = "col-lg-2"
        self.helper.field_class = "col-lg-8"

        self.helper.add_input(
                Submit("submit", "Send sign-in email",
                    css_class="col-lg-offset-2"))

        super(SignInByEmailForm, self).__init__(*args, **kwargs)


def make_sign_in_key(user):
    # try to ensure these hashes aren't guessable.
    import random
    import hashlib
    from time import time
    m = hashlib.sha1()
    m.update(user.email)
    m.update(hex(random.getrandbits(128)))
    m.update(str(time()))
    return m.hexdigest()


def sign_in_by_email(request):
    if request.method == 'POST':
        form = SignInByEmailForm(request.POST)
        if form.is_valid():
            from django.contrib.auth.models import User

            email = form.cleaned_data["email"]
            users = User.objects.filter(email=email)

            if users.count() > 1:
                messages.add_message(request, messages.ERROR,
                        "More than one user with this email. "
                        "Please contact site staff.")
                raise PermissionDenied("duplicate email")

            if users.count() == 0:
                user = User()
                user.username = email
                user.email = email
                user.set_unusable_password()
                user.save()

                ustatus = UserStatus()
                ustatus.user = user
                ustatus.status = user_status.requested
                ustatus.sign_in_key = make_sign_in_key(user)
                ustatus.save()

                messages.add_message(request, messages.INFO,
                        "Please check your email and click the link.")

            elif users.count() == 1:
                user, = users
                ustatus = user.user_status
                ustatus.user = user
                ustatus.sign_in_key = make_sign_in_key(user)
                ustatus.save()

            from django.template.loader import render_to_string
            message = render_to_string("course/sign-in-email.txt", {
                "user": user,
                "sign_in_uri": request.build_absolute_uri(
                    reverse(
                        "course.views.sign_in_link",
                        args=(ustatus.sign_in_key,))),
                "home_uri": request.build_absolute_uri(reverse("course.views.home"))
                })
            from django.core.mail import send_mail
            send_mail("Your CourseFlow sign-in link", message,
                    settings.ROBOT_EMAIL_FROM, recipient_list=[email])

            return redirect("course.views.home")
    else:
        form = SignInByEmailForm()

    return render(request, "course/login-by-email.html", {
        "form_description": "",
        "form": form
        })


def sign_in_link(request, sign_in_key):
    pass

# }}}


@login_required
def enroll(request, course_identifier):
    # FIXME
    raise NotImplementedError()


def check_course_state(course, role):
    if course.hidden:
        if role not in [participation_role.teaching_assistant,
                participation_role.instructor]:
            raise PermissionDenied("only course staff have access")
    elif course.validation_state != course_validation_state.valid:
        if role != participation_role.instructor:
            raise PermissionDenied("only the instructor has access")


def course_page(request, course_identifier):
    course = get_object_or_404(Course, identifier=course_identifier)
    role, participation = get_role_and_participation(request, course)

    check_course_state(course, role)

    commit_sha = get_active_commit_sha(course, participation)

    repo = get_course_repo(course)
    course_desc = get_course_desc(repo, commit_sha)

    from course.content import get_processed_course_chunks
    chunks = get_processed_course_chunks(course, course_desc,
            role)

    return render(request, "course/course-page.html", {
        "course": course,
        "course_desc": course_desc,
        "course_validation_state": course_validation_state,
        "participation": participation,
        "role": role,
        "chunks": chunks,
        "participation_role": participation_role,
        })


def start_flow(request, course_identifier, flow_identifier):
    course = get_object_or_404(Course, identifier=course_identifier)
    role, participation = get_role_and_participation(request, course)

    check_course_state(course, role)

    commit_sha = get_active_commit_sha(course, participation)

    repo = get_course_repo(course)
    course_desc = get_course_desc(repo, commit_sha)
    course = get_object_or_404(Course, identifier=course_identifier)

    flow_desc = get_flow_desc(repo, course, flow_identifier, commit_sha)

    permissions, stipulations = get_flow_permissions(
            course_desc, participation, role, flow_identifier, flow_desc)

    from course.models import flow_permission
    if flow_permission.view not in permissions:
        raise PermissionDenied()

    if request.method == "POST":
        from course.content import set_up_flow_visit_page_data

        if ("start_no_credit" in request.POST
                or "start_credit" in request.POST):
            visit = FlowVisit()
            visit.participation = participation
            visit.active_git_commit_sha = commit_sha.decode()
            visit.flow_id = flow_identifier
            visit.in_progress = True
            visit.for_credit = "start_credit" in request.POST
            visit.save()

            request.session["flow_visit_id"] = visit.id

            page_count = set_up_flow_visit_page_data(repo, visit,
                    flow_desc, commit_sha)
            visit.page_count = page_count
            visit.save()

            return redirect("course.views.view_flow_page",
                    course_identifier,
                    flow_identifier,
                    0)

        else:
            raise SuspiciousOperation("unrecognized POST action")

    else:
        can_start_credit = flow_permission.start_credit in permissions
        can_start_no_credit = flow_permission.start_no_credit in permissions

        # FIXME take into account max attempts
        # FIXME resumption
        # FIXME view past

        return render(request, "course/flow-start.html", {
            "participation": participation,
            "course_desc": course_desc,
            "course": course,
            "flow_desc": flow_desc,
            "flow_identifier": flow_identifier,
            "can_start_credit": can_start_credit,
            "can_start_no_credit": can_start_no_credit,
            })


class FlowPageContext(object):
    """This object acts as a container for all the information that a flow page
    may need to render itself or respond to a POST.
    """

    def __init__(self, request, course_identifier, flow_identifier,
            ordinal, flow_visit):
        self.flow_visit = flow_visit
        self.course_identifier = course_identifier
        self.flow_identifier = flow_identifier

        self.course = get_object_or_404(Course, identifier=course_identifier)
        self.role, self.participation = get_role_and_participation(
                request, self.course)

        check_course_state(self.course, self.role)

        self.commit_sha = self.flow_visit.active_git_commit_sha.encode()

        self.repo = get_course_repo(self.course)
        self.course_desc = get_course_desc(self.repo, self.commit_sha)

        self.flow_desc = get_flow_desc(self.repo, self.course,
                flow_identifier, self.commit_sha)

        self.permissions, self.stipulations = get_flow_permissions(
                self.course_desc, self.participation, self.role,
                flow_identifier, self.flow_desc)

        from course.models import FlowPageData
        page_data = self.page_data = get_object_or_404(
                FlowPageData, flow_visit=flow_visit, ordinal=ordinal)

        from course.content import get_flow_page_desc
        self.page_desc = get_flow_page_desc(
                flow_visit, self.flow_desc, page_data.group_id, page_data.page_id)

        from course.content import instantiate_flow_page
        self.page = instantiate_flow_page(
                "course '%s', flow '%s', page '%s/%s'"
                % (course_identifier, flow_identifier,
                    page_data.group_id, page_data.page_id),
                self.repo, self.page_desc, self.commit_sha)

        from course.page import PageContext
        self.page_context = PageContext(
                course=self.course,
                ordinal=page_data.ordinal,
                page_count=flow_visit.page_count,
                )

        # {{{ dig for previous answers

        from course.models import FlowPageVisit
        previous_answer_visits = (FlowPageVisit.objects
                .filter(flow_visit=flow_visit)
                .filter(page_data=page_data)
                .filter(answer__isnull=False)
                .order_by("-visit_time"))

        self.prev_answer_is_final = False
        self.prev_answer = None
        for prev_visit in previous_answer_visits:
            self.prev_answer = prev_visit.answer
            self.prev_answer_is_final = prev_visit.answer_is_final
            break

        # }}}

    @property
    def ordinal(self):
        return self.page_data.ordinal

    @property
    def page_count(self):
        return self.flow_visit.page_count

    def create_visit(self):
        from course.models import FlowPageVisit

        page_visit = FlowPageVisit()
        page_visit.flow_visit = self.flow_visit
        page_visit.page_data = self.page_data
        page_visit.save()

    def will_receive_feedback(self):
        from course.models import flow_permission
        return (
                flow_permission.see_correctness in self.permissions
                or flow_permission.see_answer in self.permissions)


def find_current_flow_visit(request, flow_identifier):
    flow_visit = None
    flow_visit_id = request.session.get("flow_visit_id")

    if flow_visit_id is not None:
        flow_visits = list(FlowVisit.objects.filter(id=flow_visit_id))

        if flow_visits and flow_visits[0].flow_id == flow_identifier:
            flow_visit, = flow_visits

        if not flow_visit.in_progress:
            flow_visit = False

    return flow_visit


def finish_flow_visit(flow_visit):
    from django.utils.timezone import now
    flow_visit.completion_time = now()
    flow_visit.in_progress = False
    flow_visit.save()

    # FIXME mark answers as final
    # FIXME assign grade


def render_flow_completion_response(request, fpctx):
    # FIXME show grade

    from course.content import html_body
    return render(request, "course/flow-completion.html", {
        "course": fpctx.course,
        "course_desc": fpctx.course_desc,
        "flow_identifier": fpctx.flow_identifier,
        "flow_desc": fpctx.flow_desc,
        "body": html_body(fpctx.course, fpctx.flow_desc.completion_text),
        "participation": fpctx.participation,
    })


def render_flow_page(request, fpctx, **kwargs):
    args = {
        "course": fpctx.course,
        "course_desc": fpctx.course_desc,
        "flow_identifier": fpctx.flow_identifier,
        "flow_desc": fpctx.flow_desc,
        "ordinal": fpctx.ordinal,
        "page_data": fpctx.page_data,
        "flow_visit": fpctx.flow_visit,
        "participation": fpctx.participation,
    }

    args.update(kwargs)

    return render(request, "course/flow-page.html", args)


def finalize_flow_page_form(fpctx, form):
    if form is not None and not fpctx.prev_answer_is_final:
        from crispy_forms.layout import Submit
        form.helper.add_input(
                Submit("save", "Save answer",
                    css_class="col-lg-offset-2"))

        if fpctx.will_receive_feedback():
            form.helper.add_input(Submit("submit", "Submit final answer"))
        else:
            # Only offer 'save and move on' if student will receive no feedback
            if fpctx.page_data.ordinal + 1 < fpctx.flow_visit.page_count:
                form.helper.add_input(
                        Submit("save_and_next", "Save answer and move on"))
            else:
                form.helper.add_input(
                        Submit("save_and_finish", "Save answer and finish"))

    return form


def view_flow_page(request, course_identifier, flow_identifier, ordinal):
    flow_visit = find_current_flow_visit(request, flow_identifier)

    if flow_visit is None:
        messages.add_message(request, messages.WARNING,
                "No in-progress visit record found for this flow. "
                "Redirected to flow start page.")

        return redirect("course.views.start_flow",
                course_identifier,
                flow_identifier)

    fpctx = FlowPageContext(request, course_identifier, flow_identifier,
            ordinal, flow_visit)

    page_context = fpctx.page_context
    page_data = fpctx.page_data

    from course.models import FlowPageVisit, flow_permission

    if flow_permission.view not in fpctx.permissions:
        raise PermissionDenied("not allowed to view flow")

    if request.method == "POST":
        if "finish" in request.POST:
            finish_flow_visit(flow_visit)
            request.session["flow_visit_id"] = None
            return render_flow_completion_response(request, fpctx)
        else:
            # reject if previous answer was final
            if fpctx.prev_answer_is_final:
                raise PermissionDenied("already have final answer")

            form = fpctx.page.post_form(fpctx.page_context, fpctx.page_data.data,
                    post_data=request.POST, files_data=request.POST)

            # {{{ figure out which button was pressed

            buttons = ["save", "save_and_next", "save_and_finish", "submit"]
            pressed_button = None
            for button in buttons:
                if button in form.data:
                    pressed_button = button
                    break

            if pressed_button is None:
                raise SuspiciousOperation("could not find which button was pressed")

            # }}}

            if form.is_valid():
                # {{{ form validated, process answer

                messages.add_message(request, messages.INFO,
                        "Answer saved.")

                page_visit = FlowPageVisit()
                page_visit.flow_visit = fpctx.flow_visit
                page_visit.page_data = fpctx.page_data
                page_visit.answer = fpctx.page.make_answer_data(
                        fpctx.page_context, fpctx.page_data.data,
                        form)
                page_visit.answer_is_final = pressed_button == "submit"
                page_visit.save()

                if (pressed_button == "save_and_next"
                        and not fpctx.will_receive_feedback()):
                    return redirect("course.views.view_flow_page",
                            course_identifier,
                            flow_identifier,
                            fpctx.ordinal + 1)
                elif (pressed_button == "save_and_finish"
                        and not fpctx.will_receive_feedback()):
                    finish_flow_visit(flow_visit)
                    request.session["flow_visit_id"] = None
                    return render_flow_completion_response(request, fpctx)
                else:
                    title = fpctx.page.title(page_context, page_data.data)
                    body = fpctx.page.body(page_context, page_data.data)

                    form = fpctx.page.form_with_answer(page_context, page_data.data,
                            page_visit.answer, page_visit.answer_is_final)

                    form = finalize_flow_page_form(fpctx, form)

                    # FIXME generate feedback

                    return render_flow_page(request, fpctx,
                            title=title, body=body, form=form)

                # }}}

            else:
                # {{{ form did not validate

                fpctx.create_visit()

                title = fpctx.page.title(page_context, page_data.data)
                body = fpctx.page.body(page_context, page_data.data)

                form = finalize_flow_page_form(fpctx, form)

                return render_flow_page(request,
                        fpctx, title=title, body=body, form=form)

                # }}}

    else:
        fpctx.create_visit()

        page_context = fpctx.page_context
        page_data = fpctx. page_data

        title = fpctx.page.title(page_context, page_data.data)
        body = fpctx.page.body(page_context, page_data.data)

        if fpctx.prev_answer:
            form = fpctx.page.form_with_answer(page_context, page_data.data,
                    fpctx.prev_answer, fpctx.prev_answer_is_final)
        else:
            form = fpctx.page.fresh_form(page_context, page_data.data)

        # FIXME generate feedback

        form = finalize_flow_page_form(fpctx, form)

        return render_flow_page(request, fpctx, title=title, body=body, form=form)

# }}}

# vim: foldmethod=marker