From 89c48757c68a9fc9f275a789117209fd90d751e8 Mon Sep 17 00:00:00 2001
From: Baptiste Jonglez <git@bitsofnetworks.org>
Date: Wed, 20 Oct 2021 22:44:52 +0200
Subject: [PATCH] Display monthly statistics for the range of months where the
 project was active

instead of the currently hard-coded "one year" range in the past starting
from today.
---
 ihatemoney/models.py |  8 ++++++++
 ihatemoney/web.py    | 16 ++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/ihatemoney/models.py b/ihatemoney/models.py
index e0ca07040..f14c20784 100644
--- a/ihatemoney/models.py
+++ b/ihatemoney/models.py
@@ -257,6 +257,14 @@ def get_member_bills(self, member_id):
             .order_by(Bill.id.desc())
         )
 
+    def get_most_recent_bill(self):
+        """Returns the most recent bill (according to bill date) or None if there are no bills"""
+        return self.get_bills_unordered().order_by(Bill.date.desc()).first()
+
+    def get_least_recent_bill(self):
+        """Returns the least recent bill (according to bill date) or None if there are no bills"""
+        return self.get_bills_unordered().order_by(Bill.date.asc()).first()
+
     def get_pretty_bills(self, export_format="json"):
         """Return a list of project's bills with pretty formatting"""
         bills = self.get_bills()
diff --git a/ihatemoney/web.py b/ihatemoney/web.py
index f783cd865..3bcc9eb73 100644
--- a/ihatemoney/web.py
+++ b/ihatemoney/web.py
@@ -10,6 +10,7 @@
 """
 from datetime import datetime
 from functools import wraps
+import itertools
 import json
 import os
 
@@ -895,12 +896,23 @@ def strip_ip_addresses():
 @main.route("/<project_id>/statistics")
 def statistics():
     """Compute what each member has paid and spent and display it"""
-    today = datetime.now()
+    if g.project.has_bills():
+        first_date = g.project.get_least_recent_bill().date
+        last_date = g.project.get_most_recent_bill().date
+    else:
+        first_date = datetime.now() - relativedelta(months=12)
+        last_date = datetime.now()
+    # Infinite iterator towards the past
+    all_months = (last_date - relativedelta(months=i) for i in itertools.count())
+    # Stop when reaching one month before the first date
+    months = itertools.takewhile(
+        lambda x: x > first_date - relativedelta(months=1), all_months
+    )
     return render_template(
         "statistics.html",
         members_stats=g.project.members_stats,
         monthly_stats=g.project.monthly_stats,
-        months=[today - relativedelta(months=i) for i in range(12)],
+        months=months,
         current_view="statistics",
     )