fix(display): default from-selector to last N months; keep all months selectable

Instead of hiding older months entirely, show all months in the from/to
selectors but default the from-select to the last MONTHS_TO_SHOW months
on page load. The "All" button resets to full history as before.

Python: passes months_to_show to render_template, IIFE sets fromSelect.value.
Go: adds MonthsToShow to response structs, data-months-to-show attr in
templates, filters.js reads it and defaults fromSelect after hideFutureMonths.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app.py

@@ -33,12 +33,6 @@ from cache_utils import get_sheet_modified_time, read_cache, write_cache, _LAST_
 from sync_fio_to_sheets import sync_to_sheets
 from infer_payments import infer_payments
 
-
-def _last_n_months(months):
-    """Return the last MONTHS_TO_SHOW months; 0 means show all."""
-    return months[-MONTHS_TO_SHOW:] if MONTHS_TO_SHOW > 0 else months
-
-
 def get_cached_data(cache_key, sheet_id, fetch_func, *args, serialize=None, deserialize=None, **kwargs):
     mod_time = get_sheet_modified_time(cache_key)
     if mod_time:
@@ -181,7 +175,7 @@ def api_adults():
     )
     result = reconcile(members, sorted_months, transactions, exceptions)
     vm = build_adults_view_model(
-        members, _last_n_months(sorted_months), result, transactions,
+        members, sorted_months, result, transactions,
         datetime.now().strftime("%Y-%m"),
         attendance_url=attendance_url, payments_url=payments_url, bank_account=BANK_ACCOUNT,
     )
@@ -205,7 +199,7 @@ def api_juniors():
     adapted_members = adapt_junior_members(junior_members)
     result = reconcile(adapted_members, sorted_months, transactions, exceptions)
     vm = build_juniors_view_model(
-        junior_members, adapted_members, _last_n_months(sorted_months), result, transactions,
+        junior_members, adapted_members, sorted_months, result, transactions,
         datetime.now().strftime("%Y-%m"),
         attendance_url=attendance_url, payments_url=payments_url, bank_account=BANK_ACCOUNT,
     )
@@ -254,14 +248,14 @@ def adults_view():
     record_step("reconcile")
 
     vm = build_adults_view_model(
-        members, _last_n_months(sorted_months), result, transactions,
+        members, sorted_months, result, transactions,
         datetime.now().strftime("%Y-%m"),
         attendance_url=attendance_url,
         payments_url=payments_url,
         bank_account=BANK_ACCOUNT,
     )
     record_step("process_data")
-    return render_template("adults.html", **vm)
+    return render_template("adults.html", months_to_show=MONTHS_TO_SHOW, **vm)
 
 @app.route("/juniors")
 def juniors_view():
@@ -290,14 +284,14 @@ def juniors_view():
     record_step("reconcile")
 
     vm = build_juniors_view_model(
-        junior_members, adapted_members, _last_n_months(sorted_months), result, transactions,
+        junior_members, adapted_members, sorted_months, result, transactions,
         datetime.now().strftime("%Y-%m"),
         attendance_url=attendance_url,
         payments_url=payments_url,
         bank_account=BANK_ACCOUNT,
     )
     record_step("process_data")
-    return render_template("juniors.html", **vm)
+    return render_template("juniors.html", months_to_show=MONTHS_TO_SHOW, **vm)
 
 @app.route("/payments")
 def payments():

go/internal/web/api/adults.go

@@ -39,4 +39,5 @@ type AdultsResponse struct {
 	PaymentsURL   string                      `json:"payments_url"`
 	BankAccount   string                      `json:"bank_account"`
 	CurrentMonth  string                      `json:"current_month"`
+	MonthsToShow  int                         `json:"months_to_show"`
 }

go/internal/web/api/build_adults.go

@@ -140,6 +140,7 @@ func buildAdultsResponse(
 		PaymentsURL:   "https://docs.google.com/spreadsheets/d/" + config.PaymentsSheetID + "/edit",
 		BankAccount:   cfg.QRAccount,
 		CurrentMonth:  currentMonth,
+		MonthsToShow:  cfg.MonthsToShow,
 	}
 }
 

go/internal/web/api/build_juniors.go

@@ -136,6 +136,7 @@ func buildJuniorsResponse(
 		PaymentsURL:   "https://docs.google.com/spreadsheets/d/" + config.PaymentsSheetID + "/edit",
 		BankAccount:   cfg.QRAccount,
 		CurrentMonth:  currentMonth,
+		MonthsToShow:  cfg.MonthsToShow,
 	}
 }
 

go/internal/web/api/handler.go

@@ -53,7 +53,7 @@ func (h *Handler) AssembleAdults(ctx context.Context) (AdultsResponse, error) {
 		return AdultsResponse{}, err
 	}
 	result := domreconcile.Reconcile(members, sortedMonths, txns, exceptions, time.Now().Year())
-	return buildAdultsResponse(members, lastNMonths(sortedMonths, h.Config.MonthsToShow), result, txns, h.Config, time.Now().Format("2006-01")), nil
+	return buildAdultsResponse(members, sortedMonths, result, txns, h.Config, time.Now().Format("2006-01")), nil
 }
 
 // ServeJuniors handles GET /api/juniors.
@@ -74,16 +74,7 @@ func (h *Handler) AssembleJuniors(ctx context.Context) (JuniorsResponse, error)
 		return JuniorsResponse{}, err
 	}
 	result := domreconcile.Reconcile(members, sortedMonths, txns, exceptions, time.Now().Year())
-	return buildJuniorsResponse(members, lastNMonths(sortedMonths, h.Config.MonthsToShow), result, txns, h.Config, time.Now().Format("2006-01")), nil
+	return buildJuniorsResponse(members, sortedMonths, result, txns, h.Config, time.Now().Format("2006-01")), nil
-}
-
-// lastNMonths returns the last n elements of months.
-// If n <= 0 or n >= len(months), the full slice is returned unchanged.
-func lastNMonths(months []string, n int) []string {
-	if n > 0 && len(months) > n {
-		return months[len(months)-n:]
-	}
-	return months
 }
 
 // ServePayments handles GET /api/payments.

go/internal/web/api/juniors.go

@@ -38,4 +38,5 @@ type JuniorsResponse struct {
 	PaymentsURL   string                       `json:"payments_url"`
 	BankAccount   string                       `json:"bank_account"`
 	CurrentMonth  string                       `json:"current_month"`
+	MonthsToShow  int                          `json:"months_to_show"`
 }

go/internal/web/static/js/filters.js

@@ -13,6 +13,7 @@
   if (!container) return;
 
   const currentMonth  = container.dataset.currentMonth || '';
+  const monthsToShow  = parseInt(container.dataset.monthsToShow || '0', 10);
 
   const nameInput   = document.getElementById('nameFilter');
   const fromSelect  = document.getElementById('fromMonth');
@@ -88,4 +89,10 @@
   // ── Initialise ────────────────────────────────────────────────────────────
 
   hideFutureMonths();
+  // Default the from-select to show only the last N months.
+  if (monthsToShow > 0 && toSelect.value !== '') {
+    const defaultFrom = Math.max(0, parseInt(toSelect.value, 10) - monthsToShow + 1);
+    fromSelect.value = String(defaultFrom);
+    applyMonthFilter();
+  }
 }());

go/internal/web/templates/adults.tmpl

@@ -12,7 +12,7 @@
   <a href="{{.Data.PaymentsURL}}" target="_blank" rel="noopener">Payments Ledger</a>
 </div>
 
-<div class="filter-container" id="filterContainer" data-current-month="{{.Data.CurrentMonth}}" data-page="adults" data-bank-account="{{.Data.BankAccount}}">
+<div class="filter-container" id="filterContainer" data-current-month="{{.Data.CurrentMonth}}" data-page="adults" data-bank-account="{{.Data.BankAccount}}" data-months-to-show="{{.Data.MonthsToShow}}">
   <div class="filter-item">
     <label class="filter-label" for="nameFilter">Member</label>
     <input id="nameFilter" class="filter-input" type="text" placeholder="Filter by name…">

go/internal/web/templates/juniors.tmpl

@@ -12,7 +12,7 @@
   <a href="{{.Data.PaymentsURL}}" target="_blank" rel="noopener">Payments Ledger</a>
 </div>
 
-<div class="filter-container" id="filterContainer" data-current-month="{{.Data.CurrentMonth}}" data-page="juniors" data-bank-account="{{.Data.BankAccount}}">
+<div class="filter-container" id="filterContainer" data-current-month="{{.Data.CurrentMonth}}" data-page="juniors" data-bank-account="{{.Data.BankAccount}}" data-months-to-show="{{.Data.MonthsToShow}}">
   <div class="filter-item">
     <label class="filter-label" for="nameFilter">Member</label>
     <input id="nameFilter" class="filter-input" type="text" placeholder="Filter by name…">

go/tests/fixtures/api-schema/adults.schema.json

@@ -143,6 +143,9 @@
         },
         "current_month": {
           "type": "string"
+        },
+        "months_to_show": {
+          "type": "integer"
         }
       },
       "additionalProperties": false,
@@ -161,7 +164,8 @@
         "attendance_url",
         "payments_url",
         "bank_account",
-        "current_month"
+        "current_month",
+        "months_to_show"
       ]
     },
     "Credit": {

go/tests/fixtures/api-schema/juniors.schema.json

@@ -187,6 +187,9 @@
         },
         "current_month": {
           "type": "string"
+        },
+        "months_to_show": {
+          "type": "integer"
         }
       },
       "additionalProperties": false,
@@ -205,7 +208,8 @@
         "attendance_url",
         "payments_url",
         "bank_account",
-        "current_month"
+        "current_month",
+        "months_to_show"
       ]
     },
     "MemberOtherEntry": {

templates/adults.html

@@ -1045,6 +1045,7 @@
             });
 
             toSelect.value = maxMonthIdx;
+            fromSelect.value = Math.max(0, maxMonthIdx - {{ months_to_show }} + 1);
             applyMonthFilter();
         })();
     </script>

templates/juniors.html

@@ -1026,6 +1026,7 @@
             });
 
             toSelect.value = maxMonthIdx;
+            fromSelect.value = Math.max(0, maxMonthIdx - {{ months_to_show }} + 1);
             applyMonthFilter();
         })();
     </script>