Clone conference durable workflow

README.md

@@ -71,6 +71,20 @@ To start a workflow from Django (a view, an admin action, a command), use
 `pycon.resonate_app.start_workflow(name, workflow_id, ...)`. The workflow id is
 the idempotency key: creating the same id twice joins the existing run.
 
+Creating the next edition of the conference is one of those workflows: select
+the conference to use as base in the admin and run the *Create new conference
+using this one as base* action, which asks for the code, name, hostname and
+dates of the new edition (prefilled with the next year's) and starts the
+workflow.
+
+It copies configuration only (deadlines, shifted by the new start date;
+durations; the schedule days, laid out over the new dates with the rooms and
+slots of the edition it copies; sponsor levels, benefits and special options;
+email templates; menus, copy and FAQs; forms and their questions; voting
+included events). Everything produced during an edition -- proposals, the talks
+scheduled into those slots, keynotes, sponsors, grants, vouchers, answers -- is
+not copied, and neither are the pretix ids or the logo.
+
 ## External repos
 
 Repos used by this project are in separate repositories.

backend/conferences/admin/actions.py

@@ -1,7 +1,18 @@
+from datetime import timedelta
+from uuid import uuid4
+
+from django import forms
 from django.contrib import admin, messages
+from django.contrib.admin import widgets
+from django.core.exceptions import ValidationError
+from django.template.response import TemplateResponse
+
+from conferences.models import Conference
 from conferences.tasks import send_conference_voucher_email
+from conferences.workflows import CLONE_CONFERENCE
 from custom_admin.admin import validate_single_conference_selection
 from pretix import create_voucher
+from pycon.resonate_app import start_workflow
 
 
 @admin.action(description="Send voucher via email")
@@ -48,3 +59,128 @@ def create_conference_vouchers_on_pretix(modeladmin, request, queryset):
         count = count + 1
 
     messages.success(request, f"{count} Vouchers created on Pretix!")
+
+
+class CloneConferenceForm(forms.Form):
+    """What the new conference overrides; everything else comes from the base one."""
+
+    code = forms.CharField(max_length=100)
+    name = forms.CharField(max_length=100)
+    hostname = forms.CharField(max_length=255)
+    start = forms.SplitDateTimeField(widget=widgets.AdminSplitDateTime())
+    end = forms.SplitDateTimeField(widget=widgets.AdminSplitDateTime())
+
+    def clean_code(self):
+        code = self.cleaned_data["code"]
+
+        if Conference.objects.filter(code=code).exists():
+            raise ValidationError(f"Conference {code} already exists")
+
+        return code
+
+    def clean_hostname(self):
+        hostname = self.cleaned_data["hostname"]
+
+        if Conference.objects.filter(hostname=hostname).exists():
+            raise ValidationError(f"Hostname {hostname} is already used")
+
+        return hostname
+
+    def clean(self):
+        cleaned_data = super().clean()
+        start = cleaned_data.get("start")
+        end = cleaned_data.get("end")
+
+        if start and end and start > end:
+            raise ValidationError("Start date cannot be after end")
+
+        return cleaned_data
+
+
+def next_edition_defaults(conference: Conference) -> dict:
+    """Prefill the form with the next edition: same values, one year later."""
+    year = conference.start.year if conference.start else None
+
+    def bump_year(value: str) -> str:
+        if not year or str(year) not in value:
+            return value
+
+        return value.replace(str(year), str(year + 1), 1)
+
+    def next_year(value):
+        if not value:
+            return value
+
+        try:
+            return value.replace(year=value.year + 1)
+        except ValueError:
+            # 29th of February: the next edition has no such day.
+            return value + timedelta(days=365)
+
+    return {
+        "code": bump_year(conference.code),
+        "name": bump_year(str(conference.name)),
+        "hostname": bump_year(conference.hostname),
+        "start": next_year(conference.start),
+        "end": next_year(conference.end),
+    }
+
+
+@admin.action(description="Create new conference using this one as base")
+def clone_conference(modeladmin, request, queryset):
+    selected = list(queryset)
+
+    if len(selected) != 1:
+        messages.error(request, "Select the single conference to use as base")
+        return None
+
+    source = selected[0]
+
+    if request.POST.get("apply"):
+        form = CloneConferenceForm(request.POST)
+
+        if form.is_valid():
+            start_clone_conference(request, source, form.cleaned_data)
+            return None
+    else:
+        form = CloneConferenceForm(initial=next_edition_defaults(source))
+
+    return TemplateResponse(
+        request,
+        "admin/conferences/clone_conference.html",
+        {
+            **modeladmin.admin_site.each_context(request),
+            "title": f"New conference based on {source.code}",
+            "opts": modeladmin.model._meta,
+            "media": modeladmin.media + form.media,
+            "source": source,
+            "form": form,
+            # The page posts back to the changelist, so it has to name the
+            # action; taken from the function so a rename cannot break it.
+            "action_name": clone_conference.__name__,
+        },
+    )
+
+
+def start_clone_conference(request, source: Conference, data: dict) -> None:
+    # A fresh id per submission, so a run that failed for good can be started
+    # again. Double submits are harmless anyway: every step of the workflow
+    # only creates what is not there yet.
+    workflow_id = f"clone-conference-{data['code']}-{uuid4().hex[:8]}"
+
+    start_workflow(
+        CLONE_CONFERENCE,
+        workflow_id,
+        source_code=source.code,
+        new_code=data["code"],
+        new_name=data["name"],
+        new_start=data["start"].isoformat(),
+        new_end=data["end"].isoformat(),
+        new_hostname=data["hostname"],
+    )
+
+    messages.success(
+        request,
+        f"Creating {data['code']} based on {source.code}. "
+        f"Follow the progress in Resonate (workflow {workflow_id}).",
+    )

backend/conferences/admin/conference.py

@@ -35,7 +35,11 @@
     Topic,
 )
 from conferences.admin.views import grants_summary
-from .actions import send_voucher_via_email, create_conference_vouchers_on_pretix
+from .actions import (
+    clone_conference,
+    create_conference_vouchers_on_pretix,
+    send_voucher_via_email,
+)
 
 
 def validate_deadlines_form(forms):
@@ -192,6 +196,7 @@ class ConferenceAdmin(
         ("YouTube", {"fields": ("video_title_template", "video_description_template")}),
     )
     inlines = [DeadlineInline, DurationInline, SponsorLevelInline, IncludedEventInline]
+    actions = [clone_conference]
 
     @admin.display(description="Schedule Builder")
     def schedule_builder_link(self, obj):

backend/conferences/models/conference.py

@@ -124,7 +124,9 @@ class Conference(GeoLocalizedModel, TimeFramedModel, TimeStampedModel):
         _("max proposals per user"),
         null=True,
         blank=True,
-        help_text=_("Maximum number of proposals a user can submit. Leave empty for no limit."),
+        help_text=_(
+            "Maximum number of proposals a user can submit. Leave empty for no limit."
+        ),
     )
 
     def get_slack_oauth_token(self):

backend/conferences/templates/admin/conferences/clone_conference.html

@@ -0,0 +1,55 @@
+{% extends "admin/base_site.html" %}
+{% load i18n admin_urls %}
+
+{% block extrahead %}{{ block.super }}{{ media }}{% endblock %}
+
+{% block breadcrumbs %}
+    <div class="breadcrumbs">
+        <a href="{% url 'admin:index' %}">{% translate 'Home' %}</a>
+        &rsaquo; <a href="{% url 'admin:app_list' app_label=opts.app_label %}">{{ opts.app_config.verbose_name }}</a>
+        &rsaquo; <a href="{% url opts|admin_urlname:'changelist' %}">{{ opts.verbose_name_plural|capfirst }}</a>
+        &rsaquo; {{ title }}
+    </div>
+{% endblock %}
+
+{% block content %}
+    <p>
+        The new conference starts as a copy of <strong>{{ source }}</strong>: deadlines
+        (shifted by the new start date), durations, the schedule days (laid out over the
+        dates below, with the rooms and slots of the edition they copy), sponsor levels,
+        benefits and special options, email templates, menus, copy and FAQs, forms and
+        their questions, and voting included events. Proposals, the talks scheduled into
+        those slots, keynotes, sponsors, grants, vouchers and answers are not copied,
+        and neither are the pretix ids or the logo.
+    </p>
+
+    <form method="post">
+        {% csrf_token %}
+
+        <input type="hidden" name="_selected_action" value="{{ source.pk }}">
+        <input type="hidden" name="action" value="{{ action_name }}">
+        <input type="hidden" name="apply" value="1">
+
+        <fieldset class="module aligned">
+            {% for field in form %}
+                <div class="form-row{% if field.errors %} errors{% endif %}">
+                    {{ field.errors }}
+                    <div>
+                        {{ field.label_tag }}
+                        {{ field }}
+                    </div>
+                </div>
+            {% endfor %}
+            {% if form.non_field_errors %}
+                <p class="errornote">{{ form.non_field_errors }}</p>
+            {% endif %}
+        </fieldset>
+
+        <div class="submit-row">
+            <input type="submit" class="default" value="Create conference">
+            <a href="{% url opts|admin_urlname:'changelist' %}" class="button cancel-link">
+                {% translate 'Cancel' %}
+            </a>
+        </div>
+    </form>
+{% endblock %}