From b2db902e5c8a7192bc6baa1f15b474e9d1b3ab91 Mon Sep 17 00:00:00 2001
From: Julien Froidefond <julien.froidefond@cdbdx.biz>
Date: Fri, 28 Nov 2025 14:01:26 +0100
Subject: [PATCH] feat: implement aggregated and per-account balance
 visualization in statistics page with interactive chart options

---
 app/statistics/page.tsx                      |  84 ++++++++++--
 components/statistics/balance-line-chart.tsx | 131 +++++++++++++++++--
 2 files changed, 189 insertions(+), 26 deletions(-)

diff --git a/app/statistics/page.tsx b/app/statistics/page.tsx
index 4017a2c..3dbc0e7 100644
--- a/app/statistics/page.tsx
+++ b/app/statistics/page.tsx
@@ -119,27 +119,84 @@ export default function StatisticsPage() {
     const avgMonthlyExpenses =
       monthlyData.size > 0 ? totalExpenses / monthlyData.size : 0;
 
-    // Balance evolution
-    const sortedTransactions = [...transactions].sort(
+    // Balance evolution - Aggregated
+    const allTransactionsForBalance = data.transactions.filter(
+      (t) => new Date(t.date) >= startDate
+    );
+    const sortedAllTransactions = [...allTransactionsForBalance].sort(
       (a, b) => new Date(a.date).getTime() - new Date(b.date).getTime()
     );
 
     let runningBalance = 0;
-    const balanceByDate = new Map<string, number>();
-    sortedTransactions.forEach((t) => {
+    const aggregatedBalanceByDate = new Map<string, number>();
+    sortedAllTransactions.forEach((t) => {
       runningBalance += t.amount;
-      balanceByDate.set(t.date, runningBalance);
+      aggregatedBalanceByDate.set(t.date, runningBalance);
     });
 
-    const balanceChartData = Array.from(balanceByDate.entries()).map(
-      ([date, balance]) => ({
+    const aggregatedBalanceData = Array.from(
+      aggregatedBalanceByDate.entries()
+    ).map(([date, balance]) => ({
+      date: new Date(date).toLocaleDateString("fr-FR", {
+        day: "2-digit",
+        month: "short",
+      }),
+      solde: Math.round(balance),
+    }));
+
+    // Balance evolution - Per account
+    const accountBalances = new Map<string, Map<string, number>>();
+    data.accounts.forEach((account) => {
+      accountBalances.set(account.id, new Map());
+    });
+
+    // Calculate running balance per account
+    const accountRunningBalances = new Map<string, number>();
+    data.accounts.forEach((account) => {
+      accountRunningBalances.set(account.id, 0);
+    });
+
+    sortedAllTransactions.forEach((t) => {
+      const currentBalance = accountRunningBalances.get(t.accountId) || 0;
+      const newBalance = currentBalance + t.amount;
+      accountRunningBalances.set(t.accountId, newBalance);
+
+      const accountDates = accountBalances.get(t.accountId);
+      if (accountDates) {
+        accountDates.set(t.date, newBalance);
+      }
+    });
+
+    // Merge all dates and create data points
+    const allDates = new Set<string>();
+    accountBalances.forEach((dates) => {
+      dates.forEach((_, date) => allDates.add(date));
+    });
+
+    const sortedDates = Array.from(allDates).sort();
+    const lastBalances = new Map<string, number>();
+    data.accounts.forEach((account) => {
+      lastBalances.set(account.id, 0);
+    });
+
+    const perAccountBalanceData = sortedDates.map((date) => {
+      const point: { date: string; [key: string]: string | number } = {
         date: new Date(date).toLocaleDateString("fr-FR", {
           day: "2-digit",
           month: "short",
         }),
-        solde: Math.round(balance),
-      })
-    );
+      };
+
+      data.accounts.forEach((account) => {
+        const accountDates = accountBalances.get(account.id);
+        if (accountDates?.has(date)) {
+          lastBalances.set(account.id, accountDates.get(date)!);
+        }
+        point[account.id] = Math.round(lastBalances.get(account.id) || 0);
+      });
+
+      return point;
+    });
 
     return {
       monthlyChartData,
@@ -148,7 +205,8 @@ export default function StatisticsPage() {
       totalIncome,
       totalExpenses,
       avgMonthlyExpenses,
-      balanceChartData,
+      aggregatedBalanceData,
+      perAccountBalanceData,
       transactionCount: transactions.length,
     };
   }, [data, period, selectedAccount]);
@@ -219,7 +277,9 @@ export default function StatisticsPage() {
           formatCurrency={formatCurrency}
         />
         <BalanceLineChart
-          data={stats.balanceChartData}
+          aggregatedData={stats.aggregatedBalanceData}
+          perAccountData={stats.perAccountBalanceData}
+          accounts={data.accounts}
           formatCurrency={formatCurrency}
         />
         <TopExpensesList
diff --git a/components/statistics/balance-line-chart.tsx b/components/statistics/balance-line-chart.tsx
index ef30e4e..dedcfc7 100644
--- a/components/statistics/balance-line-chart.tsx
+++ b/components/statistics/balance-line-chart.tsx
@@ -1,6 +1,9 @@
 "use client";
 
+import { useState } from "react";
 import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
+import { Button } from "@/components/ui/button";
+import { Layers, SplitSquareHorizontal } from "lucide-react";
 import {
   LineChart,
   Line,
@@ -9,29 +12,75 @@ import {
   CartesianGrid,
   Tooltip,
   ResponsiveContainer,
+  Legend,
 } from "recharts";
+import type { Account } from "@/lib/types";
 
-interface BalanceChartData {
+interface BalanceChartDataPoint {
   date: string;
-  solde: number;
+  [key: string]: string | number;
 }
 
 interface BalanceLineChartProps {
-  data: BalanceChartData[];
+  aggregatedData: BalanceChartDataPoint[];
+  perAccountData: BalanceChartDataPoint[];
+  accounts: Account[];
   formatCurrency: (amount: number) => string;
 }
 
+const ACCOUNT_COLORS = [
+  "#6366f1", // indigo
+  "#22c55e", // green
+  "#f59e0b", // amber
+  "#ef4444", // red
+  "#8b5cf6", // violet
+  "#06b6d4", // cyan
+  "#ec4899", // pink
+  "#84cc16", // lime
+];
+
 export function BalanceLineChart({
-  data,
+  aggregatedData,
+  perAccountData,
+  accounts,
   formatCurrency,
 }: BalanceLineChartProps) {
+  const [mode, setMode] = useState<"aggregated" | "split">("aggregated");
+  const [hoveredAccount, setHoveredAccount] = useState<string | null>(null);
+
+  const data = mode === "aggregated" ? aggregatedData : perAccountData;
+  const hasData = data.length > 0;
+
+  const getLineOpacity = (accountId: string) => {
+    if (!hoveredAccount) return 1;
+    return hoveredAccount === accountId ? 1 : 0.15;
+  };
+
   return (
     <Card>
-      <CardHeader>
+      <CardHeader className="flex flex-row items-center justify-between space-y-0 pb-2">
         <CardTitle>Évolution du solde</CardTitle>
+        <div className="flex gap-1">
+          <Button
+            variant={mode === "aggregated" ? "default" : "ghost"}
+            size="sm"
+            onClick={() => setMode("aggregated")}
+            title="Tous les comptes agrégés"
+          >
+            <Layers className="w-4 h-4" />
+          </Button>
+          <Button
+            variant={mode === "split" ? "default" : "ghost"}
+            size="sm"
+            onClick={() => setMode("split")}
+            title="Par compte"
+          >
+            <SplitSquareHorizontal className="w-4 h-4" />
+          </Button>
+        </div>
       </CardHeader>
       <CardContent>
-        {data.length > 0 ? (
+        {hasData ? (
           <div className="h-[300px]">
             <ResponsiveContainer width="100%" height="100%">
               <LineChart data={data}>
@@ -50,13 +99,68 @@ export function BalanceLineChart({
                     borderRadius: "8px",
                   }}
                 />
-                <Line
-                  type="monotone"
-                  dataKey="solde"
-                  stroke="#6366f1"
-                  strokeWidth={2}
-                  dot={false}
-                />
+                {mode === "aggregated" ? (
+                  <Line
+                    type="monotone"
+                    dataKey="solde"
+                    name="Solde total"
+                    stroke="#6366f1"
+                    strokeWidth={2}
+                    dot={false}
+                  />
+                ) : (
+                  accounts.map((account, index) => (
+                    <Line
+                      key={account.id}
+                      type="monotone"
+                      dataKey={account.id}
+                      name={account.name}
+                      stroke={ACCOUNT_COLORS[index % ACCOUNT_COLORS.length]}
+                      strokeWidth={hoveredAccount === account.id ? 3 : 2}
+                      strokeOpacity={getLineOpacity(account.id)}
+                      dot={false}
+                    />
+                  ))
+                )}
+                {mode === "split" && (
+                  <Legend
+                    content={({ payload }) => (
+                      <div
+                        className="flex flex-wrap justify-center gap-x-4 gap-y-1 mt-2"
+                        onMouseLeave={() => setHoveredAccount(null)}
+                      >
+                        {payload?.map((entry, index) => {
+                          const accountId = entry.dataKey as string;
+                          const isHovered = hoveredAccount === accountId;
+                          const isDimmed =
+                            hoveredAccount && hoveredAccount !== accountId;
+                          return (
+                            <div
+                              key={`legend-${index}`}
+                              className="flex items-center gap-1.5 text-sm cursor-pointer transition-opacity"
+                              style={{
+                                opacity: isDimmed ? 0.3 : 1,
+                              }}
+                              onMouseEnter={() => setHoveredAccount(accountId)}
+                            >
+                              <div
+                                className="w-3 h-3 rounded-full"
+                                style={{
+                                  backgroundColor: entry.color,
+                                  transform: isHovered ? "scale(1.2)" : "scale(1)",
+                                  transition: "transform 0.15s",
+                                }}
+                              />
+                              <span className="text-foreground">
+                                {entry.value}
+                              </span>
+                            </div>
+                          );
+                        })}
+                      </div>
+                    )}
+                  />
+                )}
               </LineChart>
             </ResponsiveContainer>
           </div>
@@ -69,4 +173,3 @@ export function BalanceLineChart({
     </Card>
   );
 }
-