Add bus-factor analyzer script

Implements scripts/bus-factor.mjs — a standalone Node.js CLI that shells
out to git log --numstat to collect per-file, per-author commit stats,
then computes bus-factor scores (number of contributors with >10%
ownership) for every source file in server/src/, client/src/, and
db/migrations/.

High-risk files (bus-factor=1) are surfaced prominently in the default
report. A --json flag emits machine-readable output for CI. Pure
analysis functions (parseGitLog, computeOwnership, scoreFiles, repoStats)
are unit-tested with Vitest (19 tests, all passing).

No new runtime dependencies — only Node.js built-ins and git are required.
Run via: node scripts/bus-factor.mjs [--json] [--min-commits N] [--top N]

Nightshift-Task: bus-factor
Nightshift-Ref: https://github.com/marcus/nightshift

.claude/settings.local.json

@@ -24,22 +24,7 @@
       "Bash(npm run:*)",
       "Bash(/home/christian/.nvm/versions/node/v24.14.0/bin/npm run:*)",
       "Bash(PATH=\"/home/christian/.nvm/versions/node/v24.14.0/bin:$PATH\" npm run build 2>&1)",
-      "Bash(PATH=\"/home/christian/.nvm/versions/node/v24.14.0/bin:$PATH\" npx vite build 2>&1)",
+      "Bash(PATH=\"/home/christian/.nvm/versions/node/v24.14.0/bin:$PATH\" npx vite build 2>&1)"
-      "Bash(sqlite3 /home/christian/projects/budget/.todos/issues.db \"PRAGMA integrity_check;\")",
-      "Bash(td usage:*)",
-      "Bash(ls:*)",
-      "Bash(sudo chown:*)",
-      "Bash(td add:*)",
-      "Bash(td log:*)",
-      "Bash(git:*)",
-      "Bash(npm list:*)",
-      "Bash(td accept:*)",
-      "Bash(/home/christian/.nvm/versions/node/v24.14.0/bin/npm test:*)",
-      "Bash(PATH=\"/home/christian/.nvm/versions/node/v24.14.0/bin:$PATH\" npm test)",
-      "Bash(PATH=\"/home/christian/.nvm/versions/node/v24.14.0/bin:$PATH\" npm --prefix /home/christian/projects/budget/server test 2>&1)",
-      "Bash(PATH=\"/home/christian/.nvm/versions/node/v24.14.0/bin:$PATH\" npm --prefix /home/christian/projects/budget/client test 2>&1)",
-      "Bash(PATH=\"/home/christian/.nvm/versions/node/v24.14.0/bin:$PATH\" npm --prefix /home/christian/projects/budget/client test)",
-      "Bash(PATH=\"/home/christian/.nvm/versions/node/v24.14.0/bin:$PATH\" npm --prefix /home/christian/projects/budget/client test -- --reporter=verbose)"
     ]
   }
 }

.gitignore

@@ -41,5 +41,3 @@ Thumbs.db
 
 # Coverage
 coverage/
-# Nightshift plan artifacts (keep out of version control)
-.nightshift-plan

CLAUDE.md

@@ -77,8 +77,6 @@ cd client && npm run test:watch
 - Export pure functions (validators, formatters, etc.) for direct testing
 - Run `npm test` in both `server/` and `client/` before committing
 
-**Callback prop naming convention:** React callback props follow `on[Noun][Verb]` (e.g., `onBillPaidToggle`, `onPaycheckAmountSave`, `onPaycheckGenerate`). Event handler functions in the parent component use the `handle[Action]` prefix (e.g., `handleAmountSave`, `handleBillPaidToggle`).
-
 ## Application Structure
 
 The default route `/` renders the paycheck-centric main view (`client/src/pages/PaycheckView.jsx`). It shows the current month's two paychecks side-by-side with bills, paid status, one-time expenses, and remaining balance. Month navigation (prev/next) fetches data via `GET /api/paychecks?year=&month=`.
@@ -96,87 +94,3 @@ The default route `/` renders the paycheck-centric main view (`client/src/pages/
 **Financing:** `GET/POST /api/financing`, `PUT/DELETE /api/financing/:id`, `PATCH /api/financing-payments/:id/paid`. Plans track a total amount, payoff due date, and `start_date`. Payment per period is auto-calculated as `(remaining balance) / (remaining periods)`. Split plans (`assigned_paycheck = null`) divide each period's payment across both paychecks. Plans auto-close when fully paid. Financing payments are included in the paycheck remaining balance. `start_date` prevents a plan from appearing on paycheck months before it was created — both virtual previews and `generate` respect this guard.
 
 **Migrations:** SQL files in `db/migrations/` are applied in filename order on server startup. Add new migrations as `00N_description.sql` — they run once and are tracked in the `migrations` table.
-
-## Database Schema
-
-Full DDL lives in `db/migrations/`. Key tables:
-
-| Table | Description |
-|---|---|
-| `config` | Key/value store for app settings (paycheck days, gross/net amounts). |
-| `bills` | Bill definitions: name, amount, due day, assigned paycheck, category, active flag. |
-| `paychecks` | One row per paycheck per period (year + month + paycheck_number 1 or 2). |
-| `paycheck_bills` | Junction between a paycheck instance and its bills; tracks paid status and amount_override. |
-| `one_time_expenses` | Ad-hoc expenses attached to a specific paycheck instance. |
-| `financing_plans` | Financing plans: total amount, due date, start_date, optional assigned_paycheck. |
-| `financing_payments` | One payment record per plan per paycheck; tracks paid status. |
-| `expense_categories` | Lookup table for variable-expense categories (Groceries, Gas, Dining, …). |
-| `actuals` | Actual spending log entries linked to a paycheck, category, or bill. |
-| `migrations` | Internal table tracking which migration files have been applied. |
-
-## API Endpoints
-
-All routes are prefixed with `/api`.
-
-### Paychecks
-| Method | Path | Description |
-|---|---|---|
-| `GET` | `/paychecks?year=&month=` | Return both paychecks for a month. Returns virtual data (id: null) when no DB record exists. |
-| `POST` | `/paychecks/generate?year=&month=` | Upsert paycheck records and sync bills/financing for the month. |
-| `GET` | `/paychecks/months` | List all months that have generated paycheck records, newest first. |
-| `PATCH` | `/paychecks/:id` | Update gross and net for a specific paycheck. |
-| `PATCH` | `/paycheck-bills/:id/paid` | Toggle paid status; locks amount_override on pay. |
-| `PATCH` | `/paycheck-bills/:id/amount` | Set amount_override for a variable-amount bill. |
-
-### Bills
-| Method | Path | Description |
-|---|---|---|
-| `GET` | `/bills` | List all bills ordered by assigned_paycheck, name. |
-| `POST` | `/bills` | Create a bill. |
-| `GET` | `/bills/:id` | Fetch a single bill. |
-| `PUT` | `/bills/:id` | Replace a bill's fields. |
-| `DELETE` | `/bills/:id` | Hard-delete a bill. |
-| `PATCH` | `/bills/:id/toggle` | Toggle the active flag. |
-
-### Config
-| Method | Path | Description |
-|---|---|---|
-| `GET` | `/config` | Return all config values as a flat object with numeric values. |
-| `PUT` | `/config` | Upsert one or more config keys. Unknown keys are silently ignored. |
-
-### One-Time Expenses
-| Method | Path | Description |
-|---|---|---|
-| `POST` | `/one-time-expenses` | Add a one-time expense to a paycheck. |
-| `DELETE` | `/one-time-expenses/:id` | Remove a one-time expense. |
-| `PATCH` | `/one-time-expenses/:id/paid` | Toggle paid status. |
-
-### Financing
-| Method | Path | Description |
-|---|---|---|
-| `GET` | `/financing` | List all financing plans with enriched progress fields. |
-| `POST` | `/financing` | Create a financing plan. |
-| `GET` | `/financing/:id` | Fetch a plan with its full payment history. |
-| `PUT` | `/financing/:id` | Update a financing plan. |
-| `DELETE` | `/financing/:id` | Delete a financing plan and its payments. |
-| `PATCH` | `/financing-payments/:id/paid` | Toggle a payment's paid status; auto-closes the plan when fully paid. |
-
-### Actuals & Categories
-| Method | Path | Description |
-|---|---|---|
-| `GET` | `/expense-categories` | List all expense categories. |
-| `POST` | `/expense-categories` | Create a new expense category. |
-| `GET` | `/actuals?paycheckId=` | List actual spending entries for a paycheck. |
-| `POST` | `/actuals` | Log an actual spending entry. |
-| `DELETE` | `/actuals/:id` | Remove an actual spending entry. |
-
-### Summary
-| Method | Path | Description |
-|---|---|---|
-| `GET` | `/summary/monthly?year=&month=` | Spending breakdown and category totals for a single month. |
-| `GET` | `/summary/annual?year=` | Income vs. spending, surplus/deficit trend, and stacked variable spending for a full year. |
-
-### Health
-| Method | Path | Description |
-|---|---|---|
-| `GET` | `/health` | Returns `{ ok: true }`. Used by Docker healthcheck. |

client/src/ThemeContext.jsx

@@ -2,18 +2,6 @@ import { createContext, useContext, useEffect, useState } from 'react';
 
 const ThemeContext = createContext(null);
 
-/**
- * Provides light/dark theme state to the component tree.
- *
- * On mount, the active theme is read from `localStorage`; if absent it
- * falls back to the OS `prefers-color-scheme` media query. The chosen
- * theme is applied as a `data-theme` attribute on `<html>` and persisted
- * to `localStorage` whenever it changes.
- *
- * Exposes `{ theme, toggle }` via {@link useTheme}.
- *
- * @param {{ children: React.ReactNode }} props
- */
 export function ThemeProvider({ children }) {
   const [theme, setTheme] = useState(() => {
     const stored = localStorage.getItem('theme');
@@ -37,13 +25,6 @@ export function ThemeProvider({ children }) {
   );
 }
 
-/**
- * Returns the current theme context provided by {@link ThemeProvider}.
- *
- * @returns {{ theme: 'light'|'dark', toggle: () => void }}
- *   - `theme`  — the active color scheme name
- *   - `toggle` — flips between `'light'` and `'dark'`
- */
 export function useTheme() {
   return useContext(ThemeContext);
 }

client/src/pages/AnnualOverview.jsx

@@ -3,10 +3,32 @@ import {
   BarChart, Bar, XAxis, YAxis, CartesianGrid, Tooltip, Legend,
   Cell, ResponsiveContainer, ReferenceLine,
 } from 'recharts';
-import { MONTH_NAMES, PALETTE, fmt, formatCurrencyShort } from '../utils/formatting.js';
+
+const MONTH_NAMES = [
+  'January', 'February', 'March', 'April', 'May', 'June',
+  'July', 'August', 'September', 'October', 'November', 'December',
+];
 
 const MONTH_SHORT = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
 
+const PALETTE = ['#3b82f6', '#8b5cf6', '#ec4899', '#f97316', '#22c55e', '#14b8a6', '#eab308', '#64748b'];
+
+function fmt(value) {
+  if (value == null) return '—';
+  const num = Number(value);
+  if (isNaN(num)) return '—';
+  const abs = Math.abs(num).toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
+  return num < 0 ? `-$${abs}` : `$${abs}`;
+}
+
+function formatCurrencyShort(value) {
+  if (value == null || isNaN(value)) return '';
+  const abs = Math.abs(value);
+  const sign = value < 0 ? '-' : '';
+  if (abs >= 1000) return `${sign}$${(abs / 1000).toFixed(1)}k`;
+  return `${sign}$${abs.toFixed(0)}`;
+}
+
 function surplusClass(value) {
   if (value == null || isNaN(Number(value))) return '';
   return Number(value) >= 0 ? 'text-success' : 'text-danger';

client/src/pages/Bills.jsx

@@ -1,5 +1,4 @@
 import { useState, useEffect } from 'react';
-import { formatCurrency, ordinal } from '../utils/formatting.js';
 
 const CATEGORIES = [
   'Housing', 'Utilities', 'Subscriptions', 'Insurance',
@@ -15,6 +14,19 @@ const EMPTY_FORM = {
   variable_amount: false,
 };
 
+function formatCurrency(value) {
+  const num = parseFloat(value);
+  if (isNaN(num)) return '$0.00';
+  return num.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
+}
+
+function ordinal(n) {
+  const int = parseInt(n, 10);
+  if (isNaN(int)) return n;
+  const suffix = ['th', 'st', 'nd', 'rd'];
+  const v = int % 100;
+  return int + (suffix[(v - 20) % 10] || suffix[v] || suffix[0]);
+}
 
 function Bills() {
   const [bills, setBills] = useState([]);

client/src/pages/Financing.jsx

@@ -1,5 +1,9 @@
 import { useState, useEffect } from 'react';
-import { fmt } from '../utils/formatting.js';
+
+function fmt(value) {
+  const num = parseFloat(value) || 0;
+  return '$' + num.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
+}
 
 function ProgressBar({ paid, total }) {
   const pct = total > 0 ? Math.min(100, (paid / total) * 100) : 0;

client/src/pages/MonthlySummary.jsx

@@ -3,7 +3,25 @@ import {
   PieChart, Pie, Cell, Tooltip, Legend, ResponsiveContainer,
   BarChart, Bar, XAxis, YAxis, CartesianGrid,
 } from 'recharts';
-import { MONTH_NAMES, PALETTE, formatCurrency, formatCurrencyShort } from '../utils/formatting.js';
+
+const MONTH_NAMES = [
+  'January', 'February', 'March', 'April', 'May', 'June',
+  'July', 'August', 'September', 'October', 'November', 'December',
+];
+
+function formatCurrency(value) {
+  const num = parseFloat(value) || 0;
+  return '$' + num.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
+}
+
+function formatCurrencyShort(value) {
+  const num = parseFloat(value) || 0;
+  if (Math.abs(num) >= 1000) return '$' + (num / 1000).toFixed(1) + 'k';
+  return '$' + num.toFixed(0);
+}
+
+// Accessible palette that works in light and dark
+const PALETTE = ['#3b82f6', '#8b5cf6', '#ec4899', '#f97316', '#22c55e', '#14b8a6', '#eab308', '#64748b'];
 
 function StatCard({ label, value, valueClass }) {
   return (

client/src/pages/PaycheckView.jsx

@@ -1,5 +1,20 @@
 import { useState, useEffect } from 'react';
-import { MONTH_NAMES, formatCurrency, ordinal } from '../utils/formatting.js';
+
+const MONTH_NAMES = [
+  'January', 'February', 'March', 'April', 'May', 'June',
+  'July', 'August', 'September', 'October', 'November', 'December',
+];
+
+function ordinal(n) {
+  const s = ['th', 'st', 'nd', 'rd'];
+  const v = n % 100;
+  return n + (s[(v - 20) % 10] || s[v] || s[0]);
+}
+
+function formatCurrency(value) {
+  const num = parseFloat(value) || 0;
+  return '$' + num.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
+}
 
 function formatPayDate(dateStr) {
   const [year, month, day] = dateStr.split('-').map(Number);
@@ -14,7 +29,7 @@ export { ordinal, formatCurrency, formatPayDate };
 
 // ─── PaycheckColumn ───────────────────────────────────────────────────────────
 
-function PaycheckColumn({ paycheck, onBillPaidToggle, categories, onOtePaidToggle, onOteDelete, onOteAdd, onPaycheckGenerate, onPaycheckAmountSave, onBillAmountSave, onFinancingPaidToggle }) {
+function PaycheckColumn({ paycheck, onBillPaidToggle, categories, onOtePaidToggle, onOteDelete, onOteAdd, onGenerate, onAmountSave, onBillAmountSave, onFinancingPaidToggle }) {
   const [newOteName, setNewOteName] = useState('');
   const [newOteAmount, setNewOteAmount] = useState('');
   const [actuals, setActuals] = useState([]);
@@ -80,7 +95,7 @@ function PaycheckColumn({ paycheck, onBillPaidToggle, categories, onOtePaidToggl
       // Lazy generate if this is a virtual paycheck
       let paycheckId = paycheck.id;
       if (!paycheckId) {
-        const generated = await onPaycheckGenerate();
+        const generated = await onGenerate();
         paycheckId = generated.find(p => p.paycheck_number === paycheck.paycheck_number).id;
       }
 
@@ -136,7 +151,7 @@ function PaycheckColumn({ paycheck, onBillPaidToggle, categories, onOtePaidToggl
     setAmountSaving(true);
     setAmountError(null);
     try {
-      await onPaycheckAmountSave(paycheck.paycheck_number, parseFloat(editGross) || 0, parseFloat(editNet) || 0);
+      await onAmountSave(paycheck.paycheck_number, parseFloat(editGross) || 0, parseFloat(editNet) || 0);
       setEditingAmounts(false);
     } catch (err) {
       setAmountError(err.message);
@@ -740,8 +755,8 @@ function PaycheckView() {
             onOteDelete={handleOteDelete}
             onOteAdd={handleOteAdd}
             categories={categories}
-            onPaycheckGenerate={generateMonth}
+            onGenerate={generateMonth}
-            onPaycheckAmountSave={handleAmountSave}
+            onAmountSave={handleAmountSave}
             onBillAmountSave={handleBillAmountSave}
             onFinancingPaidToggle={handleFinancingPaidToggle}
           />
@@ -752,8 +767,8 @@ function PaycheckView() {
             onOteDelete={handleOteDelete}
             onOteAdd={handleOteAdd}
             categories={categories}
-            onPaycheckGenerate={generateMonth}
+            onGenerate={generateMonth}
-            onPaycheckAmountSave={handleAmountSave}
+            onAmountSave={handleAmountSave}
             onBillAmountSave={handleBillAmountSave}
             onFinancingPaidToggle={handleFinancingPaidToggle}
           />

client/src/utils/formatting.js

@@ -1,34 +0,0 @@
-export const MONTH_NAMES = [
-  'January', 'February', 'March', 'April', 'May', 'June',
-  'July', 'August', 'September', 'October', 'November', 'December',
-];
-
-// Accessible palette that works in light and dark
-export const PALETTE = ['#3b82f6', '#8b5cf6', '#ec4899', '#f97316', '#22c55e', '#14b8a6', '#eab308', '#64748b'];
-
-export function formatCurrency(value) {
-  const num = parseFloat(value) || 0;
-  return '$' + num.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
-}
-
-export function formatCurrencyShort(value) {
-  if (value == null || isNaN(value)) return '';
-  const abs = Math.abs(value);
-  const sign = value < 0 ? '-' : '';
-  if (abs >= 1000) return `${sign}$${(abs / 1000).toFixed(1)}k`;
-  return `${sign}$${abs.toFixed(0)}`;
-}
-
-export function ordinal(n) {
-  const s = ['th', 'st', 'nd', 'rd'];
-  const v = n % 100;
-  return n + (s[(v - 20) % 10] || s[v] || s[0]);
-}
-
-export function fmt(value) {
-  if (value == null) return '—';
-  const num = Number(value);
-  if (isNaN(num)) return '—';
-  const abs = Math.abs(num).toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
-  return num < 0 ? `-$${abs}` : `$${abs}`;
-}

scripts/bus-factor.mjs

@@ -0,0 +1,213 @@
+#!/usr/bin/env node
+/**
+ * Bus-Factor Analyzer
+ * Analyzes code ownership concentration by examining git commit history.
+ * Usage: node scripts/bus-factor.js [--json] [--min-commits N] [--threshold N] [--top N]
+ */
+
+import { execSync } from 'child_process';
+import { fileURLToPath } from 'url';
+import path from 'path';
+
+// --- Pure analysis functions (exported for testing) ---
+
+/**
+ * Parse raw `git log --numstat` output into a map of file -> author -> commitCount.
+ * @param {string} rawLog - Output from git log --numstat
+ * @returns {Object} { [filePath]: { [author]: number } }
+ */
+export function parseGitLog(rawLog) {
+  const ownership = {};
+  const lines = rawLog.split('\n');
+  let currentAuthor = null;
+
+  for (const line of lines) {
+    // Commit header line: "commit <hash>"
+    if (line.startsWith('commit ')) {
+      currentAuthor = null;
+      continue;
+    }
+
+    // Author line: "Author: Name <email>"
+    const authorMatch = line.match(/^Author:\s+(.+?)\s+<[^>]+>/);
+    if (authorMatch) {
+      currentAuthor = authorMatch[1].trim();
+      continue;
+    }
+
+    // Numstat line: "<added>\t<deleted>\t<filename>"
+    if (currentAuthor && /^\d+\t\d+\t/.test(line)) {
+      const parts = line.split('\t');
+      if (parts.length < 3) continue;
+
+      // Handle rename: "old/path => new/path" or "{old => new}/suffix"
+      let filePath = parts[2];
+      if (filePath.includes('{') && filePath.includes('=>')) {
+        filePath = filePath.replace(/\{([^}]*?)\s*=>\s*([^}]*?)\}/g, '$2').replace(/\s+/g, '');
+      } else if (filePath.includes(' => ')) {
+        filePath = filePath.split(' => ')[1].trim();
+      }
+
+      filePath = filePath.trim();
+      if (!filePath) continue;
+
+      if (!ownership[filePath]) ownership[filePath] = {};
+      ownership[filePath][currentAuthor] = (ownership[filePath][currentAuthor] || 0) + 1;
+    }
+  }
+
+  return ownership;
+}
+
+/**
+ * Compute ownership metrics for a single file.
+ * @param {Object} authorCounts - { [author]: commitCount }
+ * @param {number} ownershipThreshold - min fraction to count toward bus-factor (default 0.1)
+ * @returns {Object} { totalCommits, authors, busFactor, primaryOwner }
+ */
+export function computeOwnership(authorCounts, ownershipThreshold = 0.1) {
+  const entries = Object.entries(authorCounts).sort((a, b) => b[1] - a[1]);
+  const totalCommits = entries.reduce((sum, [, n]) => sum + n, 0);
+
+  const authors = entries.map(([name, commits]) => ({
+    name,
+    commits,
+    pct: totalCommits > 0 ? commits / totalCommits : 0,
+  }));
+
+  const busFactor = authors.filter(a => a.pct >= ownershipThreshold).length;
+  const primaryOwner = authors[0] || null;
+
+  return { totalCommits, authors, busFactor, primaryOwner };
+}
+
+/**
+ * Score all files and return sorted results.
+ * @param {Object} ownership - Output from parseGitLog
+ * @param {Object} options
+ * @returns {Array} Sorted file entries with ownership metrics
+ */
+export function scoreFiles(ownership, { minCommits = 2, ownershipThreshold = 0.1 } = {}) {
+  const results = [];
+
+  for (const [filePath, authorCounts] of Object.entries(ownership)) {
+    const metrics = computeOwnership(authorCounts, ownershipThreshold);
+    if (metrics.totalCommits < minCommits) continue;
+
+    results.push({ file: filePath, ...metrics });
+  }
+
+  // Sort: lowest bus-factor first, then most commits (highest risk first)
+  results.sort((a, b) => {
+    if (a.busFactor !== b.busFactor) return a.busFactor - b.busFactor;
+    return b.totalCommits - a.totalCommits;
+  });
+
+  return results;
+}
+
+/**
+ * Compute overall repo stats (weighted average bus-factor, high-risk count).
+ */
+export function repoStats(scoredFiles) {
+  if (scoredFiles.length === 0) return { avgBusFactor: 0, highRiskCount: 0, totalFiles: 0 };
+
+  const totalCommits = scoredFiles.reduce((s, f) => s + f.totalCommits, 0);
+  const weightedBf = scoredFiles.reduce((s, f) => s + f.busFactor * f.totalCommits, 0);
+  const avgBusFactor = totalCommits > 0 ? weightedBf / totalCommits : 0;
+  const highRiskCount = scoredFiles.filter(f => f.busFactor === 1).length;
+
+  return { avgBusFactor, highRiskCount, totalFiles: scoredFiles.length };
+}
+
+// --- CLI ---
+
+function collectGitLog(repoRoot) {
+  const dirs = ['server/src', 'client/src', 'db/migrations'];
+  const cmd = `git -C "${repoRoot}" log --numstat -- ${dirs.join(' ')}`;
+  return execSync(cmd, { maxBuffer: 50 * 1024 * 1024 }).toString();
+}
+
+function formatReport(scoredFiles, stats, topN = 10) {
+  const lines = [];
+  lines.push('');
+  lines.push('=== Bus-Factor Analysis ===');
+  lines.push('');
+  lines.push(`Files analyzed : ${stats.totalFiles}`);
+  lines.push(`High-risk files: ${stats.highRiskCount} (bus-factor = 1)`);
+  lines.push(`Avg bus-factor : ${stats.avgBusFactor.toFixed(2)} (weighted by commits)`);
+  lines.push('');
+
+  const highRisk = scoredFiles.filter(f => f.busFactor === 1);
+  if (highRisk.length === 0) {
+    lines.push('No high-risk files found.');
+  } else {
+    lines.push(`--- Top ${Math.min(topN, highRisk.length)} High-Risk Files (bus-factor = 1) ---`);
+    lines.push('');
+    for (const f of highRisk.slice(0, topN)) {
+      const owner = f.primaryOwner;
+      lines.push(`  ${f.file}`);
+      lines.push(`    commits: ${f.totalCommits}  owner: ${owner.name} (${(owner.pct * 100).toFixed(0)}%)`);
+      if (f.authors.length > 1) {
+        const others = f.authors.slice(1, 3).map(a => `${a.name} ${(a.pct * 100).toFixed(0)}%`).join(', ');
+        lines.push(`    others: ${others}`);
+      }
+      lines.push('');
+    }
+  }
+
+  lines.push('--- Author Contribution Summary ---');
+  lines.push('');
+  const authorTotals = {};
+  for (const f of scoredFiles) {
+    for (const a of f.authors) {
+      authorTotals[a.name] = (authorTotals[a.name] || 0) + a.commits;
+    }
+  }
+  const totalAll = Object.values(authorTotals).reduce((s, n) => s + n, 0);
+  const sorted = Object.entries(authorTotals).sort((a, b) => b[1] - a[1]);
+  for (const [name, commits] of sorted) {
+    const pct = totalAll > 0 ? (commits / totalAll * 100).toFixed(1) : '0.0';
+    lines.push(`  ${name.padEnd(30)} ${String(commits).padStart(5)} commits  (${pct}%)`);
+  }
+  lines.push('');
+
+  return lines.join('\n');
+}
+
+// Detect if running as main script (ESM equivalent of require.main === module)
+const isMain = process.argv[1] === fileURLToPath(import.meta.url);
+
+if (isMain) {
+  const args = process.argv.slice(2);
+  const jsonMode = args.includes('--json');
+
+  const minCommitsIdx = args.indexOf('--min-commits');
+  const minCommits = minCommitsIdx !== -1 ? parseInt(args[minCommitsIdx + 1], 10) : 2;
+
+  const thresholdIdx = args.indexOf('--threshold');
+  const threshold = thresholdIdx !== -1 ? parseFloat(args[thresholdIdx + 1]) : 0.1;
+
+  const topIdx = args.indexOf('--top');
+  const topN = topIdx !== -1 ? parseInt(args[topIdx + 1], 10) : 10;
+
+  const repoRoot = path.resolve(fileURLToPath(import.meta.url), '..', '..');
+
+  let rawLog;
+  try {
+    rawLog = collectGitLog(repoRoot);
+  } catch (err) {
+    process.stderr.write(`Error running git log: ${err.message}\n`);
+    process.exit(1);
+  }
+
+  const ownership = parseGitLog(rawLog);
+  const scoredFiles = scoreFiles(ownership, { minCommits, ownershipThreshold: threshold });
+  const stats = repoStats(scoredFiles);
+
+  if (jsonMode) {
+    process.stdout.write(JSON.stringify({ stats, files: scoredFiles }, null, 2) + '\n');
+  } else {
+    process.stdout.write(formatReport(scoredFiles, stats, topN));
+  }
+}

scripts/bus-factor.test.mjs

@@ -0,0 +1,202 @@
+import { describe, it, expect } from 'vitest';
+import { parseGitLog, computeOwnership, scoreFiles, repoStats } from './bus-factor.mjs';
+
+// --- parseGitLog ---
+
+describe('parseGitLog', () => {
+  it('parses a single commit with one file', () => {
+    const raw = `commit abc123
+Author: Alice <alice@example.com>
+Date:   Mon Jan 1 00:00:00 2024
+
+    Initial commit
+
+5\t2\tserver/src/index.js
+`;
+    const result = parseGitLog(raw);
+    expect(result['server/src/index.js']).toEqual({ Alice: 1 });
+  });
+
+  it('accumulates multiple commits by the same author', () => {
+    const raw = `commit aaa
+Author: Alice <alice@example.com>
+Date:   Mon Jan 1 00:00:00 2024
+
+    First
+
+3\t0\tserver/src/app.js
+
+commit bbb
+Author: Alice <alice@example.com>
+Date:   Tue Jan 2 00:00:00 2024
+
+    Second
+
+1\t1\tserver/src/app.js
+`;
+    const result = parseGitLog(raw);
+    expect(result['server/src/app.js']['Alice']).toBe(2);
+  });
+
+  it('tracks multiple authors for the same file', () => {
+    const raw = `commit aaa
+Author: Alice <alice@example.com>
+Date:   Mon Jan 1 00:00:00 2024
+
+    Alice commit
+
+2\t0\tclient/src/App.jsx
+
+commit bbb
+Author: Bob <bob@example.com>
+Date:   Tue Jan 2 00:00:00 2024
+
+    Bob commit
+
+1\t0\tclient/src/App.jsx
+`;
+    const result = parseGitLog(raw);
+    expect(result['client/src/App.jsx']['Alice']).toBe(1);
+    expect(result['client/src/App.jsx']['Bob']).toBe(1);
+  });
+
+  it('handles multiple files per commit', () => {
+    const raw = `commit aaa
+Author: Alice <alice@example.com>
+Date:   Mon Jan 1 00:00:00 2024
+
+    Multi-file commit
+
+2\t0\tserver/src/a.js
+3\t1\tserver/src/b.js
+`;
+    const result = parseGitLog(raw);
+    expect(result['server/src/a.js']['Alice']).toBe(1);
+    expect(result['server/src/b.js']['Alice']).toBe(1);
+  });
+
+  it('handles rename syntax (old => new)', () => {
+    const raw = `commit aaa
+Author: Alice <alice@example.com>
+Date:   Mon Jan 1 00:00:00 2024
+
+    Rename
+
+2\t0\told/path.js => new/path.js
+`;
+    const result = parseGitLog(raw);
+    expect(result['new/path.js']).toBeDefined();
+    expect(result['old/path.js']).toBeUndefined();
+  });
+
+  it('returns empty object for empty log', () => {
+    expect(parseGitLog('')).toEqual({});
+  });
+});
+
+// --- computeOwnership ---
+
+describe('computeOwnership', () => {
+  it('computes bus-factor of 1 for a solo author', () => {
+    const result = computeOwnership({ Alice: 10 });
+    expect(result.busFactor).toBe(1);
+    expect(result.totalCommits).toBe(10);
+    expect(result.primaryOwner.name).toBe('Alice');
+    expect(result.primaryOwner.pct).toBe(1);
+  });
+
+  it('computes bus-factor of 2 when two authors each own >= 10%', () => {
+    const result = computeOwnership({ Alice: 8, Bob: 2 });
+    expect(result.busFactor).toBe(2);
+  });
+
+  it('does not count authors below the threshold', () => {
+    // Bob has 5% — below default 10% threshold
+    const result = computeOwnership({ Alice: 19, Bob: 1 });
+    expect(result.busFactor).toBe(1);
+  });
+
+  it('respects a custom ownership threshold', () => {
+    // With 20% threshold, Bob (10%) doesn't count
+    const result = computeOwnership({ Alice: 9, Bob: 1 }, 0.2);
+    expect(result.busFactor).toBe(1);
+  });
+
+  it('sorts authors by commit count descending', () => {
+    const result = computeOwnership({ Alice: 3, Bob: 7, Carol: 5 });
+    expect(result.authors[0].name).toBe('Bob');
+    expect(result.authors[1].name).toBe('Carol');
+    expect(result.authors[2].name).toBe('Alice');
+  });
+
+  it('handles empty author counts gracefully', () => {
+    const result = computeOwnership({});
+    expect(result.totalCommits).toBe(0);
+    expect(result.busFactor).toBe(0);
+    expect(result.primaryOwner).toBeNull();
+  });
+});
+
+// --- scoreFiles ---
+
+describe('scoreFiles', () => {
+  const ownership = {
+    'server/src/risk.js': { Alice: 9, Bob: 1 },       // bus-factor 1 (Bob < 10%)
+    'server/src/shared.js': { Alice: 5, Bob: 5 },      // bus-factor 2
+    'server/src/tiny.js': { Alice: 1 },                // below minCommits=2, filtered
+  };
+
+  it('filters files below minCommits', () => {
+    const results = scoreFiles(ownership, { minCommits: 2 });
+    expect(results.find(f => f.file === 'server/src/tiny.js')).toBeUndefined();
+  });
+
+  it('includes files at or above minCommits', () => {
+    const results = scoreFiles(ownership, { minCommits: 2 });
+    const files = results.map(f => f.file);
+    expect(files).toContain('server/src/risk.js');
+    expect(files).toContain('server/src/shared.js');
+  });
+
+  it('sorts lowest bus-factor first', () => {
+    const results = scoreFiles(ownership, { minCommits: 2 });
+    expect(results[0].file).toBe('server/src/risk.js');
+    expect(results[1].file).toBe('server/src/shared.js');
+  });
+
+  it('returns empty array for empty ownership', () => {
+    expect(scoreFiles({}, {})).toEqual([]);
+  });
+});
+
+// --- repoStats ---
+
+describe('repoStats', () => {
+  it('returns zeros for empty input', () => {
+    const stats = repoStats([]);
+    expect(stats.avgBusFactor).toBe(0);
+    expect(stats.highRiskCount).toBe(0);
+    expect(stats.totalFiles).toBe(0);
+  });
+
+  it('counts high-risk files (busFactor === 1)', () => {
+    const files = [
+      { busFactor: 1, totalCommits: 10, authors: [] },
+      { busFactor: 2, totalCommits: 5, authors: [] },
+      { busFactor: 1, totalCommits: 3, authors: [] },
+    ];
+    const stats = repoStats(files);
+    expect(stats.highRiskCount).toBe(2);
+    expect(stats.totalFiles).toBe(3);
+  });
+
+  it('computes weighted average bus-factor', () => {
+    const files = [
+      { busFactor: 1, totalCommits: 10, authors: [] },
+      { busFactor: 3, totalCommits: 10, authors: [] },
+    ];
+    const stats = repoStats(files);
+    // (1*10 + 3*10) / 20 = 2
+    expect(stats.avgBusFactor).toBe(2);
+  });
+});

scripts/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "budget-scripts",
+  "version": "1.0.0",
+  "scripts": {
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "bus-factor": "node bus-factor.mjs"
+  },
+  "devDependencies": {
+    "vitest": "^4.1.0"
+  }
+}

scripts/vitest.config.mjs

@@ -0,0 +1,8 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'node',
+  },
+});

server/src/constants.js

@@ -1,12 +0,0 @@
-'use strict';
-
-const CONFIG_KEYS = [
-  'paycheck1_day',
-  'paycheck2_day',
-  'paycheck1_gross',
-  'paycheck1_net',
-  'paycheck2_gross',
-  'paycheck2_net',
-];
-
-module.exports = { CONFIG_KEYS };

server/src/routes/bills.js

@@ -2,20 +2,6 @@ const express = require('express');
 const router = express.Router();
 const { pool } = require('../db');
 
-/**
- * Validate the request body for bill create/update operations.
- *
- * Checks that all required fields are present and within acceptable ranges.
- * Amount is optional when `variable_amount` is true (defaults to 0 on save).
- *
- * @param {object} body - Request body.
- * @param {string}        body.name              - Bill name (non-empty).
- * @param {number|string} [body.amount]           - Bill amount; required when variable_amount is falsy.
- * @param {number|string} body.due_day            - Day of month (1–31).
- * @param {number|string} body.assigned_paycheck  - Which paycheck: 1 or 2.
- * @param {boolean}       [body.variable_amount]  - Whether the bill amount varies each month.
- * @returns {string|null} Validation error message, or null when valid.
- */
 function validateBillFields(body) {
   const { name, amount, due_day, assigned_paycheck, variable_amount } = body;
   if (!name || name.toString().trim() === '') {

server/src/routes/config.js

@@ -1,29 +1,21 @@
 const express = require('express');
 const router = express.Router();
 const { pool } = require('../db');
-const { CONFIG_KEYS } = require('../constants');
+
+const CONFIG_KEYS = [
+  'paycheck1_day',
+  'paycheck2_day',
+  'paycheck1_gross',
+  'paycheck1_net',
+  'paycheck2_gross',
+  'paycheck2_net',
+];
 
 const DEFAULTS = {
   paycheck1_day: 1,
   paycheck2_day: 15,
 };
 
-/**
- * Fetch all application config values from the database.
- *
- * Reads all known `CONFIG_KEYS` from the `config` table and coerces values
- * to numbers. Keys missing from the DB fall back to hard-coded `DEFAULTS`
- * (paycheck1_day = 1, paycheck2_day = 15); keys with no default are null.
- *
- * @returns {Promise<{
- *   paycheck1_day: number|null,
- *   paycheck2_day: number|null,
- *   paycheck1_gross: number|null,
- *   paycheck1_net: number|null,
- *   paycheck2_gross: number|null,
- *   paycheck2_net: number|null
- * }>}
- */
 async function getAllConfig() {
   const result = await pool.query(
     'SELECT key, value FROM config WHERE key = ANY($1)',

server/src/routes/financing.js

@@ -4,20 +4,9 @@ const { pool } = require('../db');
 
 // ─── Helpers ──────────────────────────────────────────────────────────────────
 
-/**
+// Count how many payment periods remain for a plan starting from (year, month),
- * Count the number of payment periods remaining for a plan, starting from
+// including that month. Each month contributes 1 or 2 periods depending on
- * (and including) the given year/month.
+// whether the plan is split across both paychecks (assigned_paycheck = null).
- *
- * Each calendar month contributes 1 period for single-paycheck plans
- * (`assigned_paycheck` = 1 or 2) or 2 periods for split plans
- * (`assigned_paycheck` = null). Always returns at least 1 to prevent
- * division-by-zero in {@link calcPaymentAmount}.
- *
- * @param {{ due_date: string, assigned_paycheck: number|null }} plan
- * @param {number} year  - Current year.
- * @param {number} month - Current month (1–12).
- * @returns {number} Number of remaining payment periods (≥ 1).
- */
 function remainingPeriods(plan, year, month) {
   const due = new Date(plan.due_date);
   const dueYear  = due.getFullYear();
@@ -30,18 +19,7 @@ function remainingPeriods(plan, year, month) {
   return monthsLeft * perMonth;
 }
 
-/**
+// Calculate the payment amount for one period.
- * Calculate the payment amount due for a single period.
- *
- * Formula: `(total_amount - paid_so_far) / remainingPeriods(plan, year, month)`.
- * Returns 0 when the plan is already fully paid.
- *
- * @param {import('pg').PoolClient} client - Active DB client (read-only query).
- * @param {{ id: number, total_amount: number|string, due_date: string, assigned_paycheck: number|null }} plan
- * @param {number} year  - Current year for period calculation.
- * @param {number} month - Current month (1–12) for period calculation.
- * @returns {Promise<number>} Payment amount rounded to 2 decimal places, or 0.
- */
 async function calcPaymentAmount(client, plan, year, month) {
   const { rows } = await client.query(
     `SELECT COALESCE(SUM(fp.amount), 0) AS paid_total
@@ -57,22 +35,7 @@ async function calcPaymentAmount(client, plan, year, month) {
   return parseFloat((remaining / periods).toFixed(2));
 }
 
-/**
+// Enrich a plan row with computed progress fields.
- * Enrich a raw `financing_plans` row with computed progress fields.
- *
- * Aggregates payment records to derive `paid_total`, `remaining`,
- * `paid_count`, `total_count`, and `overdue`. Used by every route that
- * returns a plan to the client.
- *
- * @param {import('pg').Pool} pool - DB pool (runs a single SELECT).
- * @param {object} plan - Raw row from the `financing_plans` table.
- * @returns {Promise<object>} Plan object extended with:
- *   - `paid_total`  {number} — sum of paid payment amounts
- *   - `remaining`   {number} — total_amount minus paid_total (≥ 0)
- *   - `paid_count`  {number} — number of paid financing_payments rows
- *   - `total_count` {number} — total financing_payments rows for the plan
- *   - `overdue`     {boolean} — true when active, remaining > 0, and due_date is in the past
- */
 async function enrichPlan(pool, plan) {
   const { rows } = await pool.query(
     `SELECT

server/src/routes/paychecks.js

@@ -2,7 +2,15 @@ const express = require('express');
 const router = express.Router();
 const { pool } = require('../db');
 const { calcPaymentAmount } = require('./financing');
-const { CONFIG_KEYS } = require('../constants');
+
+const CONFIG_KEYS = [
+  'paycheck1_day',
+  'paycheck2_day',
+  'paycheck1_gross',
+  'paycheck1_net',
+  'paycheck2_gross',
+  'paycheck2_net',
+];
 
 const CONFIG_DEFAULTS = {
   paycheck1_day: 1,
@@ -35,29 +43,9 @@ function pad2(n) {
   return String(n).padStart(2, '0');
 }
 
-/**
+// Build virtual (unsaved) paycheck data from config + active bills.
- * Build virtual (unsaved) paycheck data from config + active bills.
+// Returns the same shape as fetchPaychecksForMonth but with id: null
- *
+// and paycheck_bill_id: null — nothing is written to the DB.
- * Returns the same shape as {@link fetchPaychecksForMonth} but with
- * `id: null` and `paycheck_bill_id: null` — nothing is written to the DB.
- * Financing payment previews are included with `financing_payment_id: null`.
- * Plans whose `start_date` is after the requested period are excluded.
- *
- * @param {number} year  - Full four-digit year (e.g. 2025).
- * @param {number} month - Month number 1–12.
- * @returns {Promise<Array<{
- *   id: null,
- *   period_year: number,
- *   period_month: number,
- *   paycheck_number: 1|2,
- *   pay_date: string,
- *   gross: number,
- *   net: number,
- *   bills: Array<object>,
- *   one_time_expenses: [],
- *   financing: Array<object>
- * }>>}
- */
 async function buildVirtualPaychecks(year, month) {
   const config = await getConfig();
   const paychecks = [];
@@ -149,19 +137,8 @@ async function buildVirtualPaychecks(year, month) {
   return paychecks;
 }
 
-/**
+// Generate (upsert) paycheck records for the given year/month.
- * Generate (upsert) paycheck records for the given year/month.
+// Returns the two paycheck IDs.
- *
- * Inserts or updates both `paychecks` rows, syncs `paycheck_bills` for all
- * active bills, and inserts `financing_payments` for active plans that have
- * started by this period. All writes run inside a single transaction.
- * Split financing plans (assigned_paycheck = null) get half the per-period
- * amount on each paycheck.
- *
- * @param {number} year  - Full four-digit year.
- * @param {number} month - Month number 1–12.
- * @returns {Promise<number[]>} Two-element array of paycheck IDs `[id1, id2]`.
- */
 async function generatePaychecks(year, month) {
   const config = await getConfig();
 
@@ -244,25 +221,7 @@ async function generatePaychecks(year, month) {
   }
 }
 
-/**
+// Fetch both paycheck records for a month with full bill and one_time_expense data.
- * Fetch both persisted paycheck records for a month with full bill,
- * one-time-expense, and financing-payment data joined in.
- *
- * @param {number} year  - Full four-digit year.
- * @param {number} month - Month number 1–12.
- * @returns {Promise<Array<{
- *   id: number,
- *   period_year: number,
- *   period_month: number,
- *   paycheck_number: 1|2,
- *   pay_date: string,
- *   gross: number,
- *   net: number,
- *   bills: Array<object>,
- *   one_time_expenses: Array<object>,
- *   financing: Array<object>
- * }>>} Empty array when no DB records exist for the given month.
- */
 async function fetchPaychecksForMonth(year, month) {
   const pcResult = await pool.query(
     `SELECT id, period_year, period_month, paycheck_number, pay_date, gross, net