Add chart with average basket price (#450)

* Add chart with average basket price

* Avg -> Sum, cleanup

---------

Co-authored-by: tvedeane <marekjeszka@fastmail.com>

tapir/accounts/templates/accounts/user_detail.html

@@ -14,6 +14,8 @@
 {% block head %}
     {{ block.super }}
     <link rel="stylesheet" href="{% static 'shifts/css/shifts.css' %}">
+<script src="{% static 'statistics/chart_4.4.0.js' %}"></script>
+<script src="{% static 'statistics/tapir_charts.js' %}" defer></script>
 {% endblock %}
 
 {% block title %}

tapir/statistics/templates/statistics/tags/purchase_statistics_card.html

@@ -31,4 +31,18 @@ <h5 class="card-header d-flex justify-content-between align-items-center">
             </table>
         </li>
     </ul>
+    <div class="card-body">
+        <p>
+                <span class="{% tapir_button_link %}"
+                      onclick="chartManager.show_stats_chart(
+                              this,
+                              '{% url "statistics:basket_sum_evolution_json" tapir_user.pk %}',
+                              'basket_sum_evolution_canvas',
+                )">
+            <span class="material-icons">leaderboard</span>
+            <span class="button-text">{% translate "Show graph: " %}{% translate "Evolution of total spends per month" %}</span>
+            </span>
+            <canvas id="basket_sum_evolution_canvas" style="display: none;"></canvas>
+        </p>
+    </div>
 </div>

tapir/statistics/urls.py

@@ -39,4 +39,9 @@
         views.UpdatePurchaseDataManuallyView.as_view(),
         name="update_purchase_data_manually",
     ),
+    path(
+        "user/<int:pk>/basket_sum_evolution_json",
+        views.BasketSumEvolutionJsonView.as_view(),
+        name="basket_sum_evolution_json",
+    ),
 ]

tapir/statistics/views.py

@@ -5,32 +5,40 @@
 from django.contrib.auth.mixins import LoginRequiredMixin, PermissionRequiredMixin
 from django.core.management import call_command
 from django.db.models import Sum
+from django.db.models.functions import TruncMonth
 from django.shortcuts import get_object_or_404
 from django.urls import reverse
 from django.utils import timezone
 from django.utils.translation import gettext_lazy as _
 from django.views import generic
 from django.views.generic import RedirectView
 
-from tapir.accounts.models import UpdateTapirUserLogEntry
+from tapir.accounts.models import (
+    TapirUser,
+    UpdateTapirUserLogEntry,
+)
 from tapir.coop.models import ShareOwnership, ShareOwner, MemberStatus
 from tapir.coop.views import ShareCountEvolutionJsonView
 from tapir.financingcampaign.models import (
     FinancingCampaign,
     FinancingSourceDatapoint,
 )
-from tapir.settings import PERMISSION_COOP_MANAGE
+from tapir.settings import PERMISSION_COOP_MANAGE, PERMISSION_ACCOUNTS_VIEW
 from tapir.shifts.models import (
     ShiftUserData,
     ShiftSlotTemplate,
     ShiftAttendanceMode,
 )
 from tapir.shifts.services.shift_expectation_service import ShiftExpectationService
-from tapir.statistics.models import ProcessedPurchaseFiles
+from tapir.statistics.models import (
+    PurchaseBasket,
+    ProcessedPurchaseFiles,
+)
 from tapir.statistics.utils import (
     build_pie_chart_data,
     build_line_chart_data,
 )
+from tapir.utils.shortcuts import get_first_of_next_month
 
 
 class MainStatisticsView(LoginRequiredMixin, generic.TemplateView):
@@ -206,6 +214,64 @@ def get_context_data(self, **kwargs):
         return context_data
 
 
+class BasketSumEvolutionJsonView(LoginRequiredMixin, PermissionRequiredMixin, JSONView):
+    def get_permission_required(self):
+        if self.request.user.pk == self.kwargs["pk"]:
+            return []
+        return [PERMISSION_ACCOUNTS_VIEW]
+
+    def get_context_data(self, **kwargs):
+        tapir_user = get_object_or_404(TapirUser, pk=(self.kwargs["pk"]))
+
+        user_purchases = (
+            PurchaseBasket.objects.filter(tapir_user=tapir_user)
+            .annotate(month=TruncMonth("purchase_date"))
+            .values("month")
+            .annotate(average_gross_amount=Sum("gross_amount"))
+            .order_by("month")
+        )
+
+        months = self.get_months(user_purchases)
+
+        return build_line_chart_data(
+            x_axis_values=months,
+            y_axis_values=[self.get_sums_per_month(user_purchases, months)],
+            data_labels=[_("Total spends per month")],
+        )
+
+    @staticmethod
+    def get_months(user_purchases):
+        if len(user_purchases) == 0:
+            return []
+
+        months = []
+        now = timezone.now().date().replace(day=1)
+
+        month = user_purchases[0]["month"].date()
+        months.append(month.strftime("%Y-%m"))
+
+        while month < now:
+            month = get_first_of_next_month(month)
+            months.append(month.strftime("%Y-%m"))
+
+        return months
+
+    @staticmethod
+    def get_sums_per_month(purchases_query_set, months):
+        if len(purchases_query_set) == 0:
+            return []
+
+        prices = []
+        purchases_dict = {
+            entry["month"].strftime("%Y-%m"): entry["average_gross_amount"]
+            for entry in purchases_query_set
+        }
+        for month in months:
+            prices.append(purchases_dict.get(month, 0))
+
+        return prices
+
+
 class FrozenMembersJsonView(JSONView):
     def get_context_data(self, **kwargs):
         relevant_members = self.get_relevant_members()