feat: implement reports page with trends, category, and over-time charts

Add three chart tabs sharing a period selector: monthly income/expenses
area chart, horizontal category bar chart, and stacked category-over-time
bar chart with top 8 + Other grouping.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/reports/CategoryBarChart.tsx

@@ -0,0 +1,65 @@
+import { useTranslation } from "react-i18next";
+import {
+  BarChart,
+  Bar,
+  XAxis,
+  YAxis,
+  Tooltip,
+  ResponsiveContainer,
+  Cell,
+} from "recharts";
+import type { CategoryBreakdownItem } from "../../shared/types";
+
+const eurFormatter = (value: number) =>
+  new Intl.NumberFormat("fr-FR", { style: "currency", currency: "EUR", maximumFractionDigits: 0 }).format(value);
+
+interface CategoryBarChartProps {
+  data: CategoryBreakdownItem[];
+}
+
+export default function CategoryBarChart({ data }: CategoryBarChartProps) {
+  const { t } = useTranslation();
+
+  if (data.length === 0) {
+    return (
+      <div className="bg-[var(--card)] rounded-xl p-6 border border-[var(--border)]">
+        <p className="text-center text-[var(--muted-foreground)] py-8">{t("dashboard.noData")}</p>
+      </div>
+    );
+  }
+
+  return (
+    <div className="bg-[var(--card)] rounded-xl p-6 border border-[var(--border)]">
+      <ResponsiveContainer width="100%" height={Math.max(400, data.length * 40)}>
+        <BarChart data={data} layout="vertical" margin={{ top: 10, right: 30, left: 10, bottom: 0 }}>
+          <XAxis
+            type="number"
+            tickFormatter={(v) => eurFormatter(v)}
+            tick={{ fill: "var(--muted-foreground)", fontSize: 12 }}
+            stroke="var(--border)"
+          />
+          <YAxis
+            type="category"
+            dataKey="category_name"
+            width={120}
+            tick={{ fill: "var(--muted-foreground)", fontSize: 12 }}
+            stroke="var(--border)"
+          />
+          <Tooltip
+            formatter={(value: number | undefined) => eurFormatter(value ?? 0)}
+            contentStyle={{
+              backgroundColor: "var(--card)",
+              border: "1px solid var(--border)",
+              borderRadius: "8px",
+            }}
+          />
+          <Bar dataKey="total" name={t("dashboard.expenses")} radius={[0, 4, 4, 0]}>
+            {data.map((item, index) => (
+              <Cell key={index} fill={item.category_color} />
+            ))}
+          </Bar>
+        </BarChart>
+      </ResponsiveContainer>
+    </div>
+  );
+}

src/components/reports/CategoryOverTimeChart.tsx

@@ -0,0 +1,77 @@
+import { useTranslation } from "react-i18next";
+import {
+  BarChart,
+  Bar,
+  XAxis,
+  YAxis,
+  Tooltip,
+  ResponsiveContainer,
+  Legend,
+  CartesianGrid,
+} from "recharts";
+import type { CategoryOverTimeData } from "../../shared/types";
+
+const eurFormatter = (value: number) =>
+  new Intl.NumberFormat("fr-FR", { style: "currency", currency: "EUR", maximumFractionDigits: 0 }).format(value);
+
+function formatMonth(month: string): string {
+  const [year, m] = month.split("-");
+  const date = new Date(Number(year), Number(m) - 1);
+  return date.toLocaleDateString("default", { month: "short", year: "2-digit" });
+}
+
+interface CategoryOverTimeChartProps {
+  data: CategoryOverTimeData;
+}
+
+export default function CategoryOverTimeChart({ data }: CategoryOverTimeChartProps) {
+  const { t } = useTranslation();
+
+  if (data.data.length === 0) {
+    return (
+      <div className="bg-[var(--card)] rounded-xl p-6 border border-[var(--border)]">
+        <p className="text-center text-[var(--muted-foreground)] py-8">{t("dashboard.noData")}</p>
+      </div>
+    );
+  }
+
+  return (
+    <div className="bg-[var(--card)] rounded-xl p-6 border border-[var(--border)]">
+      <ResponsiveContainer width="100%" height={400}>
+        <BarChart data={data.data} margin={{ top: 10, right: 10, left: 10, bottom: 0 }}>
+          <CartesianGrid strokeDasharray="3 3" stroke="var(--border)" />
+          <XAxis
+            dataKey="month"
+            tickFormatter={formatMonth}
+            tick={{ fill: "var(--muted-foreground)", fontSize: 12 }}
+            stroke="var(--border)"
+          />
+          <YAxis
+            tickFormatter={(v) => eurFormatter(v)}
+            tick={{ fill: "var(--muted-foreground)", fontSize: 12 }}
+            stroke="var(--border)"
+            width={80}
+          />
+          <Tooltip
+            formatter={(value: number | undefined) => eurFormatter(value ?? 0)}
+            labelFormatter={(label) => formatMonth(String(label))}
+            contentStyle={{
+              backgroundColor: "var(--card)",
+              border: "1px solid var(--border)",
+              borderRadius: "8px",
+            }}
+          />
+          <Legend />
+          {data.categories.map((name) => (
+            <Bar
+              key={name}
+              dataKey={name}
+              stackId="stack"
+              fill={data.colors[name]}
+            />
+          ))}
+        </BarChart>
+      </ResponsiveContainer>
+    </div>
+  );
+}

src/components/reports/MonthlyTrendsChart.tsx

@@ -0,0 +1,93 @@
+import { useTranslation } from "react-i18next";
+import {
+  AreaChart,
+  Area,
+  XAxis,
+  YAxis,
+  Tooltip,
+  ResponsiveContainer,
+  CartesianGrid,
+} from "recharts";
+import type { MonthlyTrendItem } from "../../shared/types";
+
+const eurFormatter = (value: number) =>
+  new Intl.NumberFormat("fr-FR", { style: "currency", currency: "EUR", maximumFractionDigits: 0 }).format(value);
+
+function formatMonth(month: string): string {
+  const [year, m] = month.split("-");
+  const date = new Date(Number(year), Number(m) - 1);
+  return date.toLocaleDateString("default", { month: "short", year: "2-digit" });
+}
+
+interface MonthlyTrendsChartProps {
+  data: MonthlyTrendItem[];
+}
+
+export default function MonthlyTrendsChart({ data }: MonthlyTrendsChartProps) {
+  const { t } = useTranslation();
+
+  if (data.length === 0) {
+    return (
+      <div className="bg-[var(--card)] rounded-xl p-6 border border-[var(--border)]">
+        <p className="text-center text-[var(--muted-foreground)] py-8">{t("dashboard.noData")}</p>
+      </div>
+    );
+  }
+
+  return (
+    <div className="bg-[var(--card)] rounded-xl p-6 border border-[var(--border)]">
+      <ResponsiveContainer width="100%" height={400}>
+        <AreaChart data={data} margin={{ top: 10, right: 10, left: 10, bottom: 0 }}>
+          <defs>
+            <linearGradient id="gradientIncome" x1="0" y1="0" x2="0" y2="1">
+              <stop offset="5%" stopColor="var(--positive)" stopOpacity={0.3} />
+              <stop offset="95%" stopColor="var(--positive)" stopOpacity={0} />
+            </linearGradient>
+            <linearGradient id="gradientExpenses" x1="0" y1="0" x2="0" y2="1">
+              <stop offset="5%" stopColor="var(--negative)" stopOpacity={0.3} />
+              <stop offset="95%" stopColor="var(--negative)" stopOpacity={0} />
+            </linearGradient>
+          </defs>
+          <CartesianGrid strokeDasharray="3 3" stroke="var(--border)" />
+          <XAxis
+            dataKey="month"
+            tickFormatter={formatMonth}
+            tick={{ fill: "var(--muted-foreground)", fontSize: 12 }}
+            stroke="var(--border)"
+          />
+          <YAxis
+            tickFormatter={(v) => eurFormatter(v)}
+            tick={{ fill: "var(--muted-foreground)", fontSize: 12 }}
+            stroke="var(--border)"
+            width={80}
+          />
+          <Tooltip
+            formatter={(value: number | undefined) => eurFormatter(value ?? 0)}
+            labelFormatter={(label) => formatMonth(String(label))}
+            contentStyle={{
+              backgroundColor: "var(--card)",
+              border: "1px solid var(--border)",
+              borderRadius: "8px",
+            }}
+          />
+          <Area
+            type="monotone"
+            dataKey="income"
+            name={t("dashboard.income")}
+            stroke="var(--positive)"
+            fill="url(#gradientIncome)"
+            strokeWidth={2}
+          />
+          <Area
+            type="monotone"
+            dataKey="expenses"
+            name={t("dashboard.expenses")}
+            stroke="var(--negative)"
+            fill="url(#gradientExpenses)"
+            strokeWidth={2}
+          />
+        </AreaChart>
+      </ResponsiveContainer>
+    </div>
+  );
+}

src/hooks/useReports.ts

@@ -0,0 +1,147 @@
+import { useReducer, useCallback, useEffect, useRef } from "react";
+import type {
+  ReportTab,
+  DashboardPeriod,
+  MonthlyTrendItem,
+  CategoryBreakdownItem,
+  CategoryOverTimeData,
+} from "../shared/types";
+import { getMonthlyTrends, getCategoryOverTime } from "../services/reportService";
+import { getExpensesByCategory } from "../services/dashboardService";
+
+interface ReportsState {
+  tab: ReportTab;
+  period: DashboardPeriod;
+  monthlyTrends: MonthlyTrendItem[];
+  categorySpending: CategoryBreakdownItem[];
+  categoryOverTime: CategoryOverTimeData;
+  isLoading: boolean;
+  error: string | null;
+}
+
+type ReportsAction =
+  | { type: "SET_TAB"; payload: ReportTab }
+  | { type: "SET_PERIOD"; payload: DashboardPeriod }
+  | { type: "SET_LOADING"; payload: boolean }
+  | { type: "SET_ERROR"; payload: string | null }
+  | { type: "SET_MONTHLY_TRENDS"; payload: MonthlyTrendItem[] }
+  | { type: "SET_CATEGORY_SPENDING"; payload: CategoryBreakdownItem[] }
+  | { type: "SET_CATEGORY_OVER_TIME"; payload: CategoryOverTimeData };
+
+const initialState: ReportsState = {
+  tab: "trends",
+  period: "6months",
+  monthlyTrends: [],
+  categorySpending: [],
+  categoryOverTime: { categories: [], data: [], colors: {} },
+  isLoading: false,
+  error: null,
+};
+
+function reducer(state: ReportsState, action: ReportsAction): ReportsState {
+  switch (action.type) {
+    case "SET_TAB":
+      return { ...state, tab: action.payload };
+    case "SET_PERIOD":
+      return { ...state, period: action.payload };
+    case "SET_LOADING":
+      return { ...state, isLoading: action.payload };
+    case "SET_ERROR":
+      return { ...state, error: action.payload, isLoading: false };
+    case "SET_MONTHLY_TRENDS":
+      return { ...state, monthlyTrends: action.payload, isLoading: false };
+    case "SET_CATEGORY_SPENDING":
+      return { ...state, categorySpending: action.payload, isLoading: false };
+    case "SET_CATEGORY_OVER_TIME":
+      return { ...state, categoryOverTime: action.payload, isLoading: false };
+    default:
+      return state;
+  }
+}
+
+function computeDateRange(period: DashboardPeriod): { dateFrom?: string; dateTo?: string } {
+  if (period === "all") return {};
+
+  const now = new Date();
+  const year = now.getFullYear();
+  const month = now.getMonth();
+  const day = now.getDate();
+
+  const dateTo = `${year}-${String(month + 1).padStart(2, "0")}-${String(day).padStart(2, "0")}`;
+
+  let from: Date;
+  switch (period) {
+    case "month":
+      from = new Date(year, month, 1);
+      break;
+    case "3months":
+      from = new Date(year, month - 2, 1);
+      break;
+    case "6months":
+      from = new Date(year, month - 5, 1);
+      break;
+    case "12months":
+      from = new Date(year, month - 11, 1);
+      break;
+  }
+
+  const dateFrom = `${from.getFullYear()}-${String(from.getMonth() + 1).padStart(2, "0")}-${String(from.getDate()).padStart(2, "0")}`;
+
+  return { dateFrom, dateTo };
+}
+
+export function useReports() {
+  const [state, dispatch] = useReducer(reducer, initialState);
+  const fetchIdRef = useRef(0);
+
+  const fetchData = useCallback(async (tab: ReportTab, period: DashboardPeriod) => {
+    const fetchId = ++fetchIdRef.current;
+    dispatch({ type: "SET_LOADING", payload: true });
+    dispatch({ type: "SET_ERROR", payload: null });
+
+    try {
+      const { dateFrom, dateTo } = computeDateRange(period);
+
+      switch (tab) {
+        case "trends": {
+          const data = await getMonthlyTrends(dateFrom, dateTo);
+          if (fetchId !== fetchIdRef.current) return;
+          dispatch({ type: "SET_MONTHLY_TRENDS", payload: data });
+          break;
+        }
+        case "byCategory": {
+          const data = await getExpensesByCategory(dateFrom, dateTo);
+          if (fetchId !== fetchIdRef.current) return;
+          dispatch({ type: "SET_CATEGORY_SPENDING", payload: data });
+          break;
+        }
+        case "overTime": {
+          const data = await getCategoryOverTime(dateFrom, dateTo);
+          if (fetchId !== fetchIdRef.current) return;
+          dispatch({ type: "SET_CATEGORY_OVER_TIME", payload: data });
+          break;
+        }
+      }
+    } catch (e) {
+      if (fetchId !== fetchIdRef.current) return;
+      dispatch({
+        type: "SET_ERROR",
+        payload: e instanceof Error ? e.message : String(e),
+      });
+    }
+  }, []);
+
+  useEffect(() => {
+    fetchData(state.tab, state.period);
+  }, [state.tab, state.period, fetchData]);
+
+  const setTab = useCallback((tab: ReportTab) => {
+    dispatch({ type: "SET_TAB", payload: tab });
+  }, []);
+
+  const setPeriod = useCallback((period: DashboardPeriod) => {
+    dispatch({ type: "SET_PERIOD", payload: period });
+  }, []);
+
+  return { state, setTab, setPeriod };
+}

src/i18n/locales/en.json

@@ -225,9 +225,9 @@
   "reports": {
     "title": "Reports",
     "period": "Period",
-    "byCategory": "By Category",
+    "byCategory": "Expenses by Category",
-    "byMonth": "By Month",
+    "overTime": "Category Over Time",
-    "trends": "Trends",
+    "trends": "Monthly Trends",
     "export": "Export"
   },
   "common": {

src/i18n/locales/fr.json

@@ -225,9 +225,9 @@
   "reports": {
     "title": "Rapports",
     "period": "Période",
-    "byCategory": "Par catégorie",
+    "byCategory": "Dépenses par catégorie",
-    "byMonth": "Par mois",
+    "overTime": "Catégories dans le temps",
-    "trends": "Tendances",
+    "trends": "Tendances mensuelles",
     "export": "Exporter"
   },
   "common": {

src/pages/ReportsPage.tsx

@@ -1,14 +1,49 @@
 import { useTranslation } from "react-i18next";
+import { useReports } from "../hooks/useReports";
+import type { ReportTab } from "../shared/types";
+import PeriodSelector from "../components/dashboard/PeriodSelector";
+import MonthlyTrendsChart from "../components/reports/MonthlyTrendsChart";
+import CategoryBarChart from "../components/reports/CategoryBarChart";
+import CategoryOverTimeChart from "../components/reports/CategoryOverTimeChart";
+
+const TABS: ReportTab[] = ["trends", "byCategory", "overTime"];
 
 export default function ReportsPage() {
   const { t } = useTranslation();
+  const { state, setTab, setPeriod } = useReports();
 
   return (
-    <div>
+    <div className={state.isLoading ? "opacity-50 pointer-events-none" : ""}>
-      <h1 className="text-2xl font-bold mb-6">{t("reports.title")}</h1>
+      <div className="flex flex-col sm:flex-row sm:items-center justify-between gap-4 mb-6">
-      <div className="bg-[var(--card)] rounded-xl p-8 border border-[var(--border)] text-center text-[var(--muted-foreground)]">
+        <h1 className="text-2xl font-bold">{t("reports.title")}</h1>
-        <p>{t("common.noResults")}</p>
+        <PeriodSelector value={state.period} onChange={setPeriod} />
       </div>
+
+      <div className="flex gap-2 mb-6">
+        {TABS.map((tab) => (
+          <button
+            key={tab}
+            onClick={() => setTab(tab)}
+            className={`px-4 py-2 rounded-lg text-sm font-medium transition-colors ${
+              tab === state.tab
+                ? "bg-[var(--primary)] text-white"
+                : "bg-[var(--card)] border border-[var(--border)] text-[var(--foreground)] hover:bg-[var(--muted)]"
+            }`}
+          >
+            {t(`reports.${tab}`)}
+          </button>
+        ))}
+      </div>
+
+      {state.error && (
+        <div className="bg-red-100 text-red-700 rounded-xl p-4 mb-6">
+          {state.error}
+        </div>
+      )}
+
+      {state.tab === "trends" && <MonthlyTrendsChart data={state.monthlyTrends} />}
+      {state.tab === "byCategory" && <CategoryBarChart data={state.categorySpending} />}
+      {state.tab === "overTime" && <CategoryOverTimeChart data={state.categoryOverTime} />}
     </div>
   );
 }

src/services/reportService.ts

@@ -0,0 +1,146 @@
+import { getDb } from "./db";
+import type {
+  MonthlyTrendItem,
+  CategoryBreakdownItem,
+  CategoryOverTimeData,
+  CategoryOverTimeItem,
+} from "../shared/types";
+
+export async function getMonthlyTrends(
+  dateFrom?: string,
+  dateTo?: string
+): Promise<MonthlyTrendItem[]> {
+  const db = await getDb();
+
+  const whereClauses: string[] = [];
+  const params: unknown[] = [];
+  let paramIndex = 1;
+
+  if (dateFrom) {
+    whereClauses.push(`date >= $${paramIndex}`);
+    params.push(dateFrom);
+    paramIndex++;
+  }
+  if (dateTo) {
+    whereClauses.push(`date <= $${paramIndex}`);
+    params.push(dateTo);
+    paramIndex++;
+  }
+
+  const whereSQL =
+    whereClauses.length > 0 ? `WHERE ${whereClauses.join(" AND ")}` : "";
+
+  return db.select<MonthlyTrendItem[]>(
+    `SELECT
+       strftime('%Y-%m', date) AS month,
+       COALESCE(SUM(CASE WHEN amount > 0 THEN amount ELSE 0 END), 0) AS income,
+       ABS(COALESCE(SUM(CASE WHEN amount < 0 THEN amount ELSE 0 END), 0)) AS expenses
+     FROM transactions
+     ${whereSQL}
+     GROUP BY month
+     ORDER BY month ASC`,
+    params
+  );
+}
+
+export async function getCategoryOverTime(
+  dateFrom?: string,
+  dateTo?: string,
+  topN: number = 8
+): Promise<CategoryOverTimeData> {
+  const db = await getDb();
+
+  const whereClauses: string[] = ["t.amount < 0"];
+  const params: unknown[] = [];
+  let paramIndex = 1;
+
+  if (dateFrom) {
+    whereClauses.push(`t.date >= $${paramIndex}`);
+    params.push(dateFrom);
+    paramIndex++;
+  }
+  if (dateTo) {
+    whereClauses.push(`t.date <= $${paramIndex}`);
+    params.push(dateTo);
+    paramIndex++;
+  }
+
+  const whereSQL = `WHERE ${whereClauses.join(" AND ")}`;
+
+  // Get top N categories by total spend
+  const topCategories = await db.select<CategoryBreakdownItem[]>(
+    `SELECT
+       t.category_id,
+       COALESCE(c.name, 'Uncategorized') AS category_name,
+       COALESCE(c.color, '#9ca3af') AS category_color,
+       ABS(SUM(t.amount)) AS total
+     FROM transactions t
+     LEFT JOIN categories c ON t.category_id = c.id
+     ${whereSQL}
+     GROUP BY t.category_id
+     ORDER BY total DESC
+     LIMIT $${paramIndex}`,
+    [...params, topN]
+  );
+
+  const topCategoryIds = new Set(topCategories.map((c) => c.category_id));
+  const colors: Record<string, string> = {};
+  for (const cat of topCategories) {
+    colors[cat.category_name] = cat.category_color;
+  }
+
+  // Get monthly breakdown for all categories
+  const monthlyRows = await db.select<
+    Array<{
+      month: string;
+      category_id: number | null;
+      category_name: string;
+      total: number;
+    }>
+  >(
+    `SELECT
+       strftime('%Y-%m', t.date) AS month,
+       t.category_id,
+       COALESCE(c.name, 'Uncategorized') AS category_name,
+       ABS(SUM(t.amount)) AS total
+     FROM transactions t
+     LEFT JOIN categories c ON t.category_id = c.id
+     ${whereSQL}
+     GROUP BY month, t.category_id
+     ORDER BY month ASC`,
+    params
+  );
+
+  // Build pivot data
+  const monthMap = new Map<string, CategoryOverTimeItem>();
+  let hasOther = false;
+
+  for (const row of monthlyRows) {
+    if (!monthMap.has(row.month)) {
+      monthMap.set(row.month, { month: row.month });
+    }
+    const item = monthMap.get(row.month)!;
+
+    if (topCategoryIds.has(row.category_id)) {
+      item[row.category_name] = ((item[row.category_name] as number) || 0) + row.total;
+    } else {
+      item["Other"] = ((item["Other"] as number) || 0) + row.total;
+      hasOther = true;
+    }
+  }
+
+  if (hasOther) {
+    colors["Other"] = "#9ca3af";
+  }
+
+  const categories = topCategories.map((c) => c.category_name);
+  if (hasOther) {
+    categories.push("Other");
+  }
+
+  return {
+    categories,
+    data: Array.from(monthMap.values()),
+    colors,
+  };
+}

src/shared/types/index.ts

@@ -233,6 +233,27 @@ export interface RecentTransaction {
   category_color: string | null;
 }
 
+// --- Report Types ---
+
+export type ReportTab = "trends" | "byCategory" | "overTime";
+
+export interface MonthlyTrendItem {
+  month: string;       // "2025-01"
+  income: number;
+  expenses: number;
+}
+
+export interface CategoryOverTimeItem {
+  month: string;
+  [categoryName: string]: number | string;
+}
+
+export interface CategoryOverTimeData {
+  categories: string[];
+  data: CategoryOverTimeItem[];
+  colors: Record<string, string>;
+}
+
 export type ImportWizardStep =
   | "source-list"
   | "source-config"