Merge PR #257: feat(reports) trend-by-category = income statement (#256)

# Conflicts:
#	.gitignore
#	CHANGELOG.fr.md
#	CHANGELOG.md

CHANGELOG.fr.md

@@ -6,6 +6,7 @@
 
 - Rapports → Comparaison (réel vs réel) : le rapport est désormais une **analyse de résultat**. Les catégories de revenu apparaissent aux côtés des dépenses, avec deux lignes de résultat — **résultat avant transferts** (revenus − dépenses) et **résultat net** (après annulation des transferts) — pour voir d'un coup d'œil si la période dégage un surplus ou un déficit. Les catégories sont regroupées Revenus → Dépenses → Transferts, les couleurs suivent le sens (plus de revenu = vert, plus de dépense = rouge), et un montant de résultat passe au vert pour un surplus, au rouge pour un déficit (#253).
 - Rapports : les rapports comparables s'ouvrent désormais par défaut sur le **mois précédent (dernier mois complet)** au lieu de décembre de l'année civile courante (#253).
+- Rapports → Tendances → Par catégorie (vue tableau) : le tableau des catégories dans le temps se lit désormais comme une analyse de résultat, à l'image du rapport de comparaison. Les catégories sont regroupées en sections **Revenus → Dépenses → Transferts** avec des sous-totaux par mois et un total, et l'ancienne ligne « Total » mélangée — qui additionnait revenus, dépenses et transferts en valeurs absolues pour un chiffre sans signification — est remplacée par une ligne **Résultat net** par mois (revenus − dépenses + transferts), colorée en vert pour un surplus et en rouge pour un déficit, plus une ligne **Résultat avant transferts** affichée lorsque des transferts existent. Les cellules de catégorie restent des niveaux neutres ; seules les lignes de résultat portent une couleur de signe (#256).
 
 ## [0.11.0] - 2026-07-05
 

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - Reports → Compare (real vs real): the report is now an **income statement**. Revenue categories are shown alongside expenses, with two result lines — **result before transfers** (revenues − expenses) and the **net result** (after netting transfers) — so you can see at a glance whether the period ran a surplus or a deficit. Categories are grouped Income → Expenses → Transfers, colours follow direction (more income is green, more spending is red), and a result amount turns green for a surplus, red for a deficit (#253).
 - Reports: the comparable reports now open on the **previous (last complete) month** by default instead of the current civil year's December (#253).
+- Reports → Trends → By category (table view): the category-over-time table now reads as a result analysis, mirroring the compare report. Categories are grouped into **Income → Expenses → Transfers** sections with per-month and total subtotals, and the old mixed "Total" row — which summed income, expenses, and transfers as absolute magnitudes into a meaningless figure — is replaced by a **Net result** row per month (income − expenses + transfers), coloured green for a surplus and red for a deficit, plus a **Result before transfers** row shown when transfers exist. Category cells stay neutral levels; only the result rows carry a sign colour (#256).
 
 ## [0.11.0] - 2026-07-05
 

src/components/reports/CategoryOverTimeTable.tsx

@@ -1,5 +1,7 @@
+import { Fragment } from "react";
 import { useTranslation } from "react-i18next";
 import type { CategoryOverTimeData } from "../../shared/types";
+import { computeOverTimeResults, type OverTimeType } from "./overTimeResults";
 
 const cadFormatter = (value: number) =>
   new Intl.NumberFormat("en-CA", { style: "currency", currency: "CAD", maximumFractionDigits: 0 }).format(value);
@@ -10,6 +12,25 @@ function formatMonth(month: string): string {
   return date.toLocaleDateString("default", { month: "short", year: "2-digit" });
 }
 
+/** Colours a result figure by sign: surplus green, deficit red, zero neutral. */
+function resultColor(value: number): string {
+  if (value > 0) return "var(--positive, #10b981)";
+  if (value < 0) return "var(--negative, #ef4444)";
+  return "";
+}
+
+const SECTION_LABEL_KEY: Record<OverTimeType, string> = {
+  income: "reports.compare.sections.income",
+  expense: "reports.compare.sections.expenses",
+  transfer: "reports.compare.sections.transfers",
+};
+
+const SECTION_TOTAL_KEY: Record<OverTimeType, string> = {
+  income: "reports.compare.totalIncome",
+  expense: "reports.compare.totalExpenses",
+  transfer: "reports.compare.totalTransfers",
+};
+
 interface CategoryOverTimeTableProps {
   data: CategoryOverTimeData;
   hiddenCategories?: Set<string>;
@@ -30,7 +51,8 @@ export default function CategoryOverTimeTable({ data, hiddenCategories }: Catego
     ? data.categories.filter((name) => !hiddenCategories.has(name))
     : data.categories;
 
-  const months = data.data.map((d) => d.month);
+  const { months, sections, hasTransfers, net, beforeTransfers } = computeOverTimeResults(data, visibleCategories);
+  const colSpan = months.length + 2;
 
   return (
     <div className="bg-[var(--card)] border border-[var(--border)] rounded-xl overflow-hidden">
@@ -52,10 +74,25 @@ export default function CategoryOverTimeTable({ data, hiddenCategories }: Catego
             </tr>
           </thead>
           <tbody>
-            {visibleCategories.map((category) => {
+            {sections.map((section) => (
-              const rowTotal = data.data.reduce((sum, d) => sum + ((d as Record<string, unknown>)[category] as number || 0), 0);
+              <Fragment key={section.type}>
+                {/* Section header */}
+                <tr className="bg-[var(--muted)]">
+                  <td
+                    colSpan={colSpan}
+                    className="px-3 py-1.5 font-semibold text-[var(--muted-foreground)] uppercase text-xs tracking-wider sticky left-0 bg-[var(--muted)]"
+                  >
+                    {t(SECTION_LABEL_KEY[section.type])}
+                  </td>
+                </tr>
+                {/* Category rows — neutral levels, not deltas */}
+                {section.categories.map((category) => {
+                  const rowTotal = data.data.reduce(
+                    (sum, d) => sum + ((d as Record<string, unknown>)[category] as number || 0),
+                    0,
+                  );
                   return (
-                <tr key={category} className="border-b border-[var(--border)]/50">
+                    <tr key={category} className="border-b border-[var(--border)]/50 hover:bg-[var(--muted)]/40">
                       <td className="px-3 py-1.5 sticky left-0 bg-[var(--card)] z-10">
                         <span className="flex items-center gap-2">
                           <span
@@ -69,38 +106,80 @@ export default function CategoryOverTimeTable({ data, hiddenCategories }: Catego
                         const monthData = data.data.find((d) => d.month === month);
                         const value = (monthData as Record<string, unknown>)?.[category] as number || 0;
                         return (
-                      <td key={month} className="text-right px-3 py-1.5">
+                          <td key={month} className="text-right px-3 py-1.5 tabular-nums">
                             {value ? cadFormatter(value) : "—"}
                           </td>
                         );
                       })}
-                  <td className="text-right px-3 py-1.5 font-semibold border-l border-[var(--border)]/50">
+                      <td className="text-right px-3 py-1.5 font-semibold border-l border-[var(--border)]/50 tabular-nums">
                         {cadFormatter(rowTotal)}
                       </td>
                     </tr>
                   );
                 })}
-            <tr className="border-t-2 border-[var(--border)] font-bold text-sm bg-[var(--muted)]/20">
+                {/* Section subtotal */}
-              <td className="px-3 py-3 sticky left-0 bg-[var(--muted)]/20 z-10">{t("common.total")}</td>
+                <tr className="border-b border-[var(--border)] bg-[color-mix(in_srgb,var(--muted)_40%,var(--card))] font-semibold">
-              {months.map((month) => {
+                  <td className="px-3 py-2.5 sticky left-0 bg-[color-mix(in_srgb,var(--muted)_40%,var(--card))] z-10">
-                const monthData = data.data.find((d) => d.month === month);
+                    {t(SECTION_TOTAL_KEY[section.type])}
-                const monthTotal = visibleCategories.reduce(
-                  (sum, cat) => sum + ((monthData as Record<string, unknown>)?.[cat] as number || 0),
-                  0,
-                );
-                return (
-                  <td key={month} className="text-right px-3 py-3">
-                    {cadFormatter(monthTotal)}
                   </td>
-                );
+                  {months.map((month) => (
-              })}
+                    <td key={month} className="text-right px-3 py-2.5 tabular-nums">
-              <td className="text-right px-3 py-3 border-l border-[var(--border)]/50">
+                      {cadFormatter(section.monthly[month])}
-                {cadFormatter(
+                    </td>
-                  visibleCategories.reduce(
+                  ))}
-                    (sum, cat) => sum + data.data.reduce((s, d) => s + ((d as Record<string, unknown>)[cat] as number || 0), 0),
+                  <td className="text-right px-3 py-2.5 border-l border-[var(--border)]/50 tabular-nums">
-                    0,
+                    {cadFormatter(section.total)}
-                  ),
+                  </td>
+                </tr>
+              </Fragment>
+            ))}
+
+            {/* Result before transfers — shown only when transfers exist */}
+            {hasTransfers && (
+              <tr className="border-t-2 border-[var(--border)] font-bold bg-[color-mix(in_srgb,var(--muted)_20%,var(--card))]">
+                <td className="px-3 py-3 sticky left-0 bg-[color-mix(in_srgb,var(--muted)_20%,var(--card))] z-10">
+                  {t("reports.compare.resultBeforeTransfers")}
+                </td>
+                {months.map((month) => (
+                  <td
+                    key={month}
+                    className="text-right px-3 py-3 tabular-nums"
+                    style={{ color: resultColor(beforeTransfers.monthly[month]) }}
+                  >
+                    {cadFormatter(beforeTransfers.monthly[month])}
+                  </td>
+                ))}
+                <td
+                  className="text-right px-3 py-3 border-l border-[var(--border)]/50 tabular-nums"
+                  style={{ color: resultColor(beforeTransfers.total) }}
+                >
+                  {cadFormatter(beforeTransfers.total)}
+                </td>
+              </tr>
             )}
+            {/* Net result — bottom line (income − expenses + transfers) */}
+            <tr
+              className={`font-bold bg-[color-mix(in_srgb,var(--muted)_20%,var(--card))] ${
+                hasTransfers ? "border-b border-[var(--border)]" : "border-t-2 border-[var(--border)]"
+              }`}
+            >
+              <td className="px-3 py-3 sticky left-0 bg-[color-mix(in_srgb,var(--muted)_20%,var(--card))] z-10">
+                {t("reports.compare.resultNet")}
+              </td>
+              {months.map((month) => (
+                <td
+                  key={month}
+                  className="text-right px-3 py-3 tabular-nums"
+                  style={{ color: resultColor(net.monthly[month]) }}
+                >
+                  {cadFormatter(net.monthly[month])}
+                </td>
+              ))}
+              <td
+                className="text-right px-3 py-3 border-l border-[var(--border)]/50 tabular-nums"
+                style={{ color: resultColor(net.total) }}
+              >
+                {cadFormatter(net.total)}
               </td>
             </tr>
           </tbody>

src/components/reports/overTimeResults.test.ts

@@ -0,0 +1,137 @@
+import { describe, it, expect } from "vitest";
+import { computeOverTimeResults, OVER_TIME_TYPE_ORDER } from "./overTimeResults";
+import type { CategoryOverTimeData } from "../../shared/types";
+
+function makeData(
+  data: CategoryOverTimeData["data"],
+  types: Record<string, "income" | "expense" | "transfer">,
+): CategoryOverTimeData {
+  return { categories: Object.keys(types), data, colors: {}, categoryIds: {}, types };
+}
+
+describe("OVER_TIME_TYPE_ORDER", () => {
+  it("is income-first (income → expense → transfer)", () => {
+    expect(OVER_TIME_TYPE_ORDER).toEqual({ income: 0, expense: 1, transfer: 2 });
+  });
+});
+
+describe("computeOverTimeResults", () => {
+  it("groups categories into ordered sections with per-month + total subtotals", () => {
+    const data = makeData(
+      [
+        { month: "2025-01", Salary: 3000, Rent: 1000, Groceries: 500, Savings: 200 },
+        { month: "2025-02", Salary: 3000, Rent: 1000, Groceries: 700, Savings: 200 },
+      ],
+      { Salary: "income", Rent: "expense", Groceries: "expense", Savings: "transfer" },
+    );
+
+    const r = computeOverTimeResults(data, ["Salary", "Rent", "Groceries", "Savings"]);
+
+    expect(r.months).toEqual(["2025-01", "2025-02"]);
+    // Income-first ordering, regardless of the input category order.
+    expect(r.sections.map((s) => s.type)).toEqual(["income", "expense", "transfer"]);
+
+    const income = r.sections.find((s) => s.type === "income")!;
+    const expense = r.sections.find((s) => s.type === "expense")!;
+    const transfer = r.sections.find((s) => s.type === "transfer")!;
+
+    expect(income.monthly).toEqual({ "2025-01": 3000, "2025-02": 3000 });
+    expect(income.total).toBe(6000);
+    expect(expense.categories).toEqual(["Rent", "Groceries"]);
+    expect(expense.monthly).toEqual({ "2025-01": 1500, "2025-02": 1700 });
+    expect(expense.total).toBe(3200);
+    expect(transfer.monthly).toEqual({ "2025-01": 200, "2025-02": 200 });
+    expect(transfer.total).toBe(400);
+  });
+
+  it("computes net (income − expense + transfer) and before-transfers per month", () => {
+    const data = makeData(
+      [
+        { month: "2025-01", Salary: 3000, Rent: 1000, Groceries: 500, Savings: 200 },
+        { month: "2025-02", Salary: 3000, Rent: 1000, Groceries: 700, Savings: 200 },
+      ],
+      { Salary: "income", Rent: "expense", Groceries: "expense", Savings: "transfer" },
+    );
+
+    const r = computeOverTimeResults(data, ["Salary", "Rent", "Groceries", "Savings"]);
+
+    expect(r.hasTransfers).toBe(true);
+    // before = income − expense
+    expect(r.beforeTransfers.monthly).toEqual({ "2025-01": 1500, "2025-02": 1300 });
+    expect(r.beforeTransfers.total).toBe(2800);
+    // net = before + transfer
+    expect(r.net.monthly).toEqual({ "2025-01": 1700, "2025-02": 1500 });
+    expect(r.net.total).toBe(3200);
+  });
+
+  it("collapses net to before-transfers when there are no transfers", () => {
+    const data = makeData(
+      [{ month: "2025-01", Salary: 2000, Rent: 2500 }],
+      { Salary: "income", Rent: "expense" },
+    );
+
+    const r = computeOverTimeResults(data, ["Salary", "Rent"]);
+
+    expect(r.hasTransfers).toBe(false);
+    expect(r.sections.map((s) => s.type)).toEqual(["income", "expense"]);
+    // Deficit: 2000 − 2500 = −500, identical for net and before-transfers.
+    expect(r.beforeTransfers.monthly["2025-01"]).toBe(-500);
+    expect(r.net.monthly["2025-01"]).toBe(-500);
+    expect(r.net.total).toBe(-500);
+  });
+
+  it("defaults an untyped category (e.g. Other) to expense", () => {
+    const data = makeData(
+      [{ month: "2025-01", Salary: 1000, Other: 300 }],
+      { Salary: "income" }, // Other has no type entry
+    );
+
+    const r = computeOverTimeResults(data, ["Salary", "Other"]);
+
+    const expense = r.sections.find((s) => s.type === "expense")!;
+    expect(expense.categories).toEqual(["Other"]);
+    expect(expense.total).toBe(300);
+    expect(r.net.monthly["2025-01"]).toBe(700); // 1000 − 300
+  });
+
+  it("drops empty sections and still nets a lone transfer section", () => {
+    const data = makeData([{ month: "2025-01", Move: 100 }], { Move: "transfer" });
+
+    const r = computeOverTimeResults(data, ["Move"]);
+
+    expect(r.sections.map((s) => s.type)).toEqual(["transfer"]);
+    expect(r.hasTransfers).toBe(true);
+    expect(r.beforeTransfers.monthly["2025-01"]).toBe(0);
+    expect(r.net.monthly["2025-01"]).toBe(100);
+  });
+
+  it("only counts the categories passed as visible (hidden ones excluded)", () => {
+    const data = makeData(
+      [{ month: "2025-01", Salary: 2000, Rent: 500, Hidden: 999 }],
+      { Salary: "income", Rent: "expense", Hidden: "expense" },
+    );
+
+    const r = computeOverTimeResults(data, ["Salary", "Rent"]); // Hidden filtered out upstream
+
+    const expense = r.sections.find((s) => s.type === "expense")!;
+    expect(expense.total).toBe(500);
+    expect(r.net.monthly["2025-01"]).toBe(1500); // 2000 − 500
+  });
+
+  it("treats a category absent from a month as zero", () => {
+    const data = makeData(
+      [
+        { month: "2025-01", Salary: 1000 },
+        { month: "2025-02", Salary: 1000, Bonus: 500 },
+      ],
+      { Salary: "income", Bonus: "income" },
+    );
+
+    const r = computeOverTimeResults(data, ["Salary", "Bonus"]);
+
+    const income = r.sections.find((s) => s.type === "income")!;
+    expect(income.monthly).toEqual({ "2025-01": 1000, "2025-02": 1500 });
+    expect(r.net.monthly).toEqual({ "2025-01": 1000, "2025-02": 1500 });
+    expect(r.net.total).toBe(2500);
+  });
+});

src/components/reports/overTimeResults.ts

@@ -0,0 +1,115 @@
+import type { CategoryOverTimeData, CategoryOverTimeItem } from "../../shared/types";
+
+export type OverTimeType = "income" | "expense" | "transfer";
+
+/**
+ * Income-statement reading order: revenue first, then expenses, then transfers,
+ * so the "net result" row reads naturally at the bottom (Income − Expenses +
+ * Transfers). Note this is income-first, unlike the compare report's
+ * `COMPARE_TYPE_ORDER` (expense-first) — see issue #256.
+ */
+export const OVER_TIME_TYPE_ORDER: Record<OverTimeType, number> = {
+  income: 0,
+  expense: 1,
+  transfer: 2,
+};
+
+/** A month -> value map plus the sum across all its months. */
+export interface OverTimeSeries {
+  /** month (YYYY-MM) -> value */
+  monthly: Record<string, number>;
+  /** sum across every month */
+  total: number;
+}
+
+/** One rendered section: a type, its member categories, and per-month + total subtotals. */
+export interface OverTimeSection extends OverTimeSeries {
+  type: OverTimeType;
+  categories: string[];
+}
+
+export interface OverTimeAnalysis {
+  /** Ordered list of months (mirrors `data.data` order). */
+  months: string[];
+  /** Sections ordered income → expense → transfer; empty types are dropped. */
+  sections: OverTimeSection[];
+  /** True when at least one visible transfer-type category is present. */
+  hasTransfers: boolean;
+  /** Income − Expenses + Transfers, per month (+ grand total). */
+  net: OverTimeSeries;
+  /** Income − Expenses, per month (+ grand total). Only shown when `hasTransfers`. */
+  beforeTransfers: OverTimeSeries;
+}
+
+/** Reads a numeric category cell off a pivot row, treating anything non-numeric as 0. */
+function cellValue(item: CategoryOverTimeItem | undefined, category: string): number {
+  const v = (item as Record<string, unknown> | undefined)?.[category];
+  return typeof v === "number" ? v : 0;
+}
+
+/**
+ * Pure reducer that turns the category-over-time pivot into an "income statement"
+ * shape: per-type sections with per-month subtotals, plus the net-result rows.
+ *
+ * Values coming from `getCategoryOverTime` are positive magnitudes (`ABS(SUM())`
+ * in SQL), so income/expense/transfer subtotals are all ≥ 0, and the net is
+ * `income − expense + transfer`. A category whose type is unknown (e.g. the
+ * "Other" bucket that aggregates non-top-N categories) defaults to `expense`,
+ * mirroring the `COALESCE(c.type, 'expense')` used by the service.
+ *
+ * Extracted from `CategoryOverTimeTable` and unit-tested independently — the
+ * project has no React render harness, so the arithmetic lives in a pure module.
+ */
+export function computeOverTimeResults(
+  data: CategoryOverTimeData,
+  visibleCategories: string[],
+): OverTimeAnalysis {
+  const months = data.data.map((d) => d.month);
+  const itemByMonth = new Map<string, CategoryOverTimeItem>();
+  for (const item of data.data) itemByMonth.set(item.month, item);
+
+  const typeOf = (cat: string): OverTimeType => {
+    const t = data.types[cat];
+    return t === "income" || t === "transfer" ? t : "expense";
+  };
+
+  // Bucket visible categories by type, preserving their incoming (magnitude) order.
+  const byType: Record<OverTimeType, string[]> = { income: [], expense: [], transfer: [] };
+  for (const cat of visibleCategories) byType[typeOf(cat)].push(cat);
+
+  const buildSection = (type: OverTimeType): OverTimeSection => {
+    const categories = byType[type];
+    const monthly: Record<string, number> = {};
+    let total = 0;
+    for (const month of months) {
+      const item = itemByMonth.get(month);
+      const sum = categories.reduce((s, cat) => s + cellValue(item, cat), 0);
+      monthly[month] = sum;
+      total += sum;
+    }
+    return { type, categories, monthly, total };
+  };
+
+  const income = buildSection("income");
+  const expense = buildSection("expense");
+  const transfer = buildSection("transfer");
+
+  const hasTransfers = transfer.categories.length > 0;
+
+  const net: OverTimeSeries = { monthly: {}, total: 0 };
+  const beforeTransfers: OverTimeSeries = { monthly: {}, total: 0 };
+  for (const month of months) {
+    const before = income.monthly[month] - expense.monthly[month];
+    const netMonth = before + transfer.monthly[month];
+    beforeTransfers.monthly[month] = before;
+    beforeTransfers.total += before;
+    net.monthly[month] = netMonth;
+    net.total += netMonth;
+  }
+
+  const sections = [income, expense, transfer]
+    .filter((s) => s.categories.length > 0)
+    .sort((a, b) => OVER_TIME_TYPE_ORDER[a.type] - OVER_TIME_TYPE_ORDER[b.type]);
+
+  return { months, sections, hasTransfers, net, beforeTransfers };
+}

src/hooks/useDashboard.ts

@@ -51,7 +51,7 @@ const yearStartStr = `${now.getFullYear()}-01-01`;
 const initialState: DashboardState = {
   summary: { totalCount: 0, totalAmount: 0, incomeTotal: 0, expenseTotal: 0 },
   categoryBreakdown: [],
-  categoryOverTime: { categories: [], data: [], colors: {}, categoryIds: {} },
+  categoryOverTime: { categories: [], data: [], colors: {}, categoryIds: {}, types: {} },
   budgetVsActual: [],
   period: "year",
   budgetYear: now.getMonth() === 0 ? now.getFullYear() - 1 : now.getFullYear(),

src/hooks/useTrends.ts

@@ -23,7 +23,7 @@ type Action =
 const initialState: State = {
   subView: "global",
   monthlyTrends: [],
-  categoryOverTime: { categories: [], data: [], colors: {}, categoryIds: {} },
+  categoryOverTime: { categories: [], data: [], colors: {}, categoryIds: {}, types: {} },
   isLoading: false,
   error: null,
 };

src/services/reportService.test.ts

@@ -115,33 +115,58 @@ describe("getCategoryOverTime", () => {
     expect(topCatParams).toEqual(["expense", "2025-01-01", "2025-06-30", 2, 10]);
   });
 
-  it("returns correct structure with categories, data, colors, and categoryIds", async () => {
+  it("projects category type into the top-N SELECT", async () => {
+    mockSelect
+      .mockResolvedValueOnce([]) // topCategories
+      .mockResolvedValueOnce([]); // monthlyRows
+
+    await getCategoryOverTime();
+
+    const topCatSQL = mockSelect.mock.calls[0][0] as string;
+    expect(topCatSQL).toContain("COALESCE(c.type, 'expense') AS category_type");
+  });
+
+  it("returns correct structure with categories, data, colors, categoryIds, and types", async () => {
     mockSelect
       .mockResolvedValueOnce([
-        { category_id: 1, category_name: "Food", category_color: "#ff0000", total: 500 },
+        { category_id: 1, category_name: "Food", category_color: "#ff0000", category_type: "expense", total: 500 },
-        { category_id: 2, category_name: "Transport", category_color: "#00ff00", total: 200 },
+        { category_id: 2, category_name: "Salary", category_color: "#00ff00", category_type: "income", total: 200 },
       ])
       .mockResolvedValueOnce([
         { month: "2025-01", category_id: 1, category_name: "Food", total: 300 },
-        { month: "2025-01", category_id: 2, category_name: "Transport", total: 100 },
+        { month: "2025-01", category_id: 2, category_name: "Salary", total: 100 },
         { month: "2025-02", category_id: 1, category_name: "Food", total: 200 },
-        { month: "2025-02", category_id: 2, category_name: "Transport", total: 100 },
+        { month: "2025-02", category_id: 2, category_name: "Salary", total: 100 },
       ]);
 
     const result = await getCategoryOverTime("2025-01-01", "2025-02-28", 50, undefined, "expense");
 
-    expect(result.categories).toEqual(["Food", "Transport"]);
+    expect(result.categories).toEqual(["Food", "Salary"]);
-    expect(result.colors).toEqual({ Food: "#ff0000", Transport: "#00ff00" });
+    expect(result.colors).toEqual({ Food: "#ff0000", Salary: "#00ff00" });
-    expect(result.categoryIds).toEqual({ Food: 1, Transport: 2 });
+    expect(result.categoryIds).toEqual({ Food: 1, Salary: 2 });
+    expect(result.types).toEqual({ Food: "expense", Salary: "income" });
     expect(result.data).toHaveLength(2);
-    expect(result.data[0]).toEqual({ month: "2025-01", Food: 300, Transport: 100 });
+    expect(result.data[0]).toEqual({ month: "2025-01", Food: 300, Salary: 100 });
-    expect(result.data[1]).toEqual({ month: "2025-02", Food: 200, Transport: 100 });
+    expect(result.data[1]).toEqual({ month: "2025-02", Food: 200, Salary: 100 });
   });
 
-  it("groups non-top-N categories into Other", async () => {
+  it("defaults a null category type to expense in the types map", async () => {
     mockSelect
       .mockResolvedValueOnce([
-        { category_id: 1, category_name: "Food", category_color: "#ff0000", total: 500 },
+        // COALESCE(c.type, 'expense') yields 'expense'; a null slipping through defaults too.
+        { category_id: 1, category_name: "Food", category_color: "#ff0000", category_type: null, total: 500 },
+      ])
+      .mockResolvedValueOnce([{ month: "2025-01", category_id: 1, category_name: "Food", total: 300 }]);
+
+    const result = await getCategoryOverTime();
+
+    expect(result.types).toEqual({ Food: "expense" });
+  });
+
+  it("groups non-top-N categories into Other (Other left out of the types map)", async () => {
+    mockSelect
+      .mockResolvedValueOnce([
+        { category_id: 1, category_name: "Food", category_color: "#ff0000", category_type: "expense", total: 500 },
       ])
       .mockResolvedValueOnce([
         { month: "2025-01", category_id: 1, category_name: "Food", total: 300 },
@@ -153,6 +178,7 @@ describe("getCategoryOverTime", () => {
 
     expect(result.categories).toEqual(["Food", "Other"]);
     expect(result.colors["Other"]).toBe("#9ca3af");
+    expect(result.types).toEqual({ Food: "expense" });
     expect(result.data[0]).toEqual({ month: "2025-01", Food: 300, Other: 150 });
   });
 });

src/services/reportService.ts

@@ -106,11 +106,14 @@ export async function getCategoryOverTime(
   const whereSQL = whereClauses.length > 0 ? `WHERE ${whereClauses.join(" AND ")}` : "";
 
   // Get top N categories by total spend
-  const topCategories = await db.select<CategoryBreakdownItem[]>(
+  const topCategories = await db.select<
+    (CategoryBreakdownItem & { category_type: "expense" | "income" | "transfer" })[]
+  >(
     `SELECT
        t.category_id,
        COALESCE(c.name, 'Uncategorized') AS category_name,
        COALESCE(c.color, '#9ca3af') AS category_color,
+       COALESCE(c.type, 'expense') AS category_type,
        ABS(SUM(t.amount)) AS total
      FROM transactions t
      LEFT JOIN categories c ON t.category_id = c.id
@@ -124,9 +127,11 @@ export async function getCategoryOverTime(
   const topCategoryIds = new Set(topCategories.map((c) => c.category_id));
   const colors: Record<string, string> = {};
   const categoryIds: Record<string, number | null> = {};
+  const types: Record<string, "expense" | "income" | "transfer"> = {};
   for (const cat of topCategories) {
     colors[cat.category_name] = cat.category_color;
     categoryIds[cat.category_name] = cat.category_id;
+    types[cat.category_name] = cat.category_type ?? "expense";
   }
 
   // Get monthly breakdown for all categories
@@ -135,6 +140,7 @@ export async function getCategoryOverTime(
       month: string;
       category_id: number | null;
       category_name: string;
+      category_type: "expense" | "income" | "transfer";
       total: number;
     }>
   >(
@@ -142,6 +148,7 @@ export async function getCategoryOverTime(
        strftime('%Y-%m', t.date) AS month,
        t.category_id,
        COALESCE(c.name, 'Uncategorized') AS category_name,
+       COALESCE(c.type, 'expense') AS category_type,
        ABS(SUM(t.amount)) AS total
      FROM transactions t
      LEFT JOIN categories c ON t.category_id = c.id
@@ -183,6 +190,7 @@ export async function getCategoryOverTime(
     data: Array.from(monthMap.values()),
     colors,
     categoryIds,
+    types,
   };
 }
 

src/shared/types/index.ts

@@ -372,6 +372,8 @@ export interface CategoryOverTimeData {
   data: CategoryOverTimeItem[];
   colors: Record<string, string>;
   categoryIds: Record<string, number | null>;
+  /** Category name -> its type. Built from the top-N rows (mirrors `colors`). */
+  types: Record<string, "expense" | "income" | "transfer">;
 }
 
 export interface BudgetVsActualRow {