Initial MVP: Cost.dev AI Coding Cost Optimizer Chrome extension

2026-06-14 10:48:26 +00:00
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+node_modules/
+dist/
+*.log
+.DS_Store
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+# Cost.dev — AI Coding Cost Optimizer
+
+**v1 MVP** — A Chrome extension that helps developers track, budget, and control spending on AI coding tools.
+
+## What it does (real features)
+
+- **Manual usage logging**: Log spend per tool per day with notes.
+- **Monthly dashboard**: See total spend, per-tool breakdown, daily trend list, and projected month-end bill.
+- **Budget & alerts**: Set a monthly budget and alert threshold. Over-budget notifications via `chrome.alarms` + `chrome.notifications` (checked hourly).
+- **Tool registry**: Add your AI tools (Claude Code, GitHub Copilot, Cursor, etc.) with estimated monthly cost and billing model (fixed / usage / hybrid).
+- **Local-only storage**: All data lives in `chrome.storage.local` — no backend, no cloud, no accounts.
+- **Empty-state handling**: Clean UI when no tools or data exist yet.
+
+## What is real vs. manual / deferred
+
+- **Real**: Manual entry, local storage, dashboard math, alarms/notifications, popup UI.
+- **Manual**: All usage numbers must be entered by you. We do **not** auto-scrape billing pages because auth/DOM varies and breaks — the content script is a scaffold that detects you're on a supported page and may support quick-capture in a future version.
+- **Deferred**: Chrome Web Store publishing, auto-import from APIs, paid tiers, backend sync, cross-device sync.
+
+## Tech stack
+
+- Vite + `@crxjs/vite-plugin` + TypeScript
+- Manifest V3
+- Permissions: `storage`, `alarms`, `notifications`
+- Host permissions (content script): `cursor.com`, `github.com/copilot` (scaffold only, no auto-read in v1)
+
+## Build
+
+Requires `npm install --include=dev` because this environment runs with `NODE_ENV=production`.
+
+```bash
+npm install --include=dev
+npm run build
+```
+
+The build output goes to `dist/`. Confirm `dist/manifest.json` exists.
+
+## Load unpacked
+
+1. Open `chrome://extensions`
+2. Enable **Developer mode**
+3. Click **Load unpacked**
+4. Select the `dist/` folder
+
+## Gitea
+
+```bash
+git push https://git.bunbunlabs.com/bunbun/cost-dev.git HEAD:refs/heads/main
+```
+
+Built by Bun Bun for BunBun Labs 🐰
@@ -0,0 +1,70 @@
+// Minimal PNG generator — run before build to create icon files
+const { writeFileSync, mkdirSync } = require('fs')
+
+function crc32(buf) {
+  const table = new Int32Array(256)
+  for (let i = 0; i < 256; i++) {
+    let c = i
+    for (let k = 0; k < 8; k++) c = (c & 1) ? (0xedb88320 ^ (c >>> 1)) : (c >>> 1)
+    table[i] = c
+  }
+  let crc = -1
+  for (let i = 0; i < buf.length; i++) crc = table[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8)
+  return crc ^ -1
+}
+
+function pngChunk(type, data) {
+  const len = data.length
+  const chunk = new Uint8Array(4 + 4 + len + 4)
+  const view = new DataView(chunk.buffer)
+  view.setUint32(0, len, false)
+  chunk.set(new TextEncoder().encode(type), 4)
+  chunk.set(data, 8)
+  const crc = crc32(chunk.slice(4, 8 + len))
+  view.setUint32(8 + len, crc, false)
+  return chunk
+}
+
+function generatePNG(size, color) {
+  const header = new Uint8Array([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a])
+  const ihdr = new Uint8Array(13)
+  const v = new DataView(ihdr.buffer)
+  v.setUint32(0, size, false)
+  v.setUint32(4, size, false)
+  v.setUint8(8, 8)
+  v.setUint8(9, 2)
+  v.setUint8(10, 0)
+  v.setUint8(11, 0)
+  v.setUint8(12, 0)
+
+  const rowLen = 1 + size * 3
+  const raw = new Uint8Array(size * rowLen)
+  for (let y = 0; y < size; y++) {
+    raw[y * rowLen] = 0
+    for (let x = 0; x < size; x++) {
+      const off = y * rowLen + 1 + x * 3
+      raw[off] = color[0]
+      raw[off + 1] = color[1]
+      raw[off + 2] = color[2]
+    }
+  }
+
+  const compressed = new Uint8Array(require('zlib').deflateSync(raw))
+  const idat = pngChunk('IDAT', compressed)
+  const iend = pngChunk('IEND', new Uint8Array(0))
+
+  const out = new Uint8Array(header.length + 4 + 4 + 13 + 4 + idat.length + iend.length)
+  let p = 0
+  out.set(header, p); p += header.length
+  out.set(pngChunk('IHDR', ihdr), p); p += 4 + 4 + 13 + 4
+  out.set(idat, p); p += idat.length
+  out.set(iend, p)
+  return out
+}
+
+mkdirSync('icons', { recursive: true })
+const teal = [0, 180, 170]
+writeFileSync('icons/icon16.png', generatePNG(16, teal))
+writeFileSync('icons/icon48.png', generatePNG(48, teal))
+writeFileSync('icons/icon128.png', generatePNG(128, teal))
+console.log('Icons generated')
@@ -0,0 +1,17 @@
+{
+  "name": "cost-dev",
+  "version": "1.0.0",
+  "description": "AI Coding Cost Optimizer — track and control AI tool spending",
+  "type": "module",
+  "scripts": {
+    "build": "tsc --noEmit && vite build",
+    "dev": "vite",
+    "check": "tsc --noEmit"
+  },
+  "devDependencies": {
+    "@crxjs/vite-plugin": "^2.0.0-beta.28",
+    "@types/chrome": "^0.0.268",
+    "typescript": "^5.4.5",
+    "vite": "^5.2.11"
+  }
+}
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+import { loadState, saveState, sumMonthUsages, projectedMonthEnd } from './storage'
+
+const ALARM_NAME = 'costdev_budget_check'
+
+chrome.runtime.onInstalled.addListener(async () => {
+  await chrome.alarms.create(ALARM_NAME, { periodInMinutes: 60 })
+})
+
+chrome.alarms.onAlarm.addListener(async (alarm) => {
+  if (alarm.name !== ALARM_NAME) return
+  const state = await loadState()
+  if (!state.budget.enabled || state.budget.monthlyLimit <= 0) return
+
+  const spent = sumMonthUsages(state.usages)
+  const limit = state.budget.monthlyLimit
+  const threshold = limit * state.budget.alertThreshold
+
+  if (spent >= threshold && spent < limit) {
+    const last = state.lastAlertAt ?? 0
+    if (Date.now() - last > 24 * 60 * 60 * 1000) {
+      chrome.notifications.create('costdev-warning', {
+        type: 'basic',
+        iconUrl: 'icons/icon128.png',
+        title: 'Cost.dev — Budget Alert',
+        message: `You've spent $${spent.toFixed(2)} of your $${limit.toFixed(2)} monthly budget.`,
+        priority: 1,
+      })
+      state.lastAlertAt = Date.now()
+      await saveState(state)
+    }
+  }
+
+  if (spent >= limit) {
+    const last = state.lastAlertAt ?? 0
+    if (Date.now() - last > 24 * 60 * 60 * 1000) {
+      chrome.notifications.create('costdev-over', {
+        type: 'basic',
+        iconUrl: 'icons/icon128.png',
+        title: 'Cost.dev — Budget Overrun',
+        message: `You've exceeded your $${limit.toFixed(2)} monthly budget! Current spend: $${spent.toFixed(2)}.`,
+        priority: 2,
+      })
+      state.lastAlertAt = Date.now()
+      await saveState(state)
+    }
+  }
+})
+
+chrome.runtime.onMessage.addListener((message, _sender, sendResponse) => {
+  ;(async () => {
+    if (message.type === 'budget-check') {
+      const state = await loadState()
+      const spent = sumMonthUsages(state.usages)
+      const limit = state.budget.monthlyLimit
+      const projected = projectedMonthEnd(spent)
+      sendResponse({ spent, limit, projected, enabled: state.budget.enabled })
+    } else {
+      sendResponse({ ok: false })
+    }
+  })()
+  return true
+})
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+// Content script — honest about what we can and cannot read client-side
+// v1: we do NOT auto-scrape private billing pages because authentication
+// and DOM structures vary and break. Instead, we watch for visible plan/usage
+// text on dashboard pages and offer a "Quick Capture" to the user via a
+// floating badge (not implemented in v1 to keep scope tight).
+// In v1, this script is a lightweight scaffold that sends a heartbeat
+// so the popup knows the user is on a supported tool page.
+
+interface PageInfo {
+  url: string
+  title: string
+  hasBillingText: boolean
+}
+
+function detectBillingIndicators(): boolean {
+  const text = document.body.innerText.toLowerCase()
+  const indicators = [
+    'usage',
+    'tokens',
+    'requests',
+    'credits',
+    'billing',
+    'subscription',
+    'plan',
+    'limit',
+    'quota',
+  ]
+  return indicators.some((w) => text.includes(w))
+}
+
+const pageInfo: PageInfo = {
+  url: location.href,
+  title: document.title,
+  hasBillingText: detectBillingIndicators(),
+}
+
+chrome.runtime.sendMessage({ type: 'page-info', data: pageInfo }).catch(() => {
+  // no-op if popup closed
+})
@@ -0,0 +1,42 @@
+{
+  "manifest_version": 3,
+  "name": "Cost.dev — AI Coding Cost Optimizer",
+  "version": "1.0.0",
+  "description": "Track, budget, and control your AI coding tool spend. Manual entry + dashboard.",
+  "permissions": ["storage", "alarms", "notifications"],
+  "host_permissions": [
+    "https://cursor.com/*",
+    "https://www.cursor.com/*",
+    "https://github.com/copilot/*",
+    "https://copilot.github.com/*"
+  ],
+  "background": {
+    "service_worker": "src/background.ts",
+    "type": "module"
+  },
+  "action": {
+    "default_popup": "src/popup/popup.html",
+    "default_icon": {
+      "16": "icons/icon16.png",
+      "48": "icons/icon48.png",
+      "128": "icons/icon128.png"
+    }
+  },
+  "icons": {
+    "16": "icons/icon16.png",
+    "48": "icons/icon48.png",
+    "128": "icons/icon128.png"
+  },
+  "content_scripts": [
+    {
+      "matches": [
+        "https://cursor.com/*",
+        "https://www.cursor.com/*",
+        "https://github.com/copilot/*",
+        "https://copilot.github.com/*"
+      ],
+      "js": ["src/content.ts"],
+      "run_at": "document_idle"
+    }
+  ]
+}
@@ -0,0 +1,176 @@
+*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
+:root {
+  --bg: #0f172a;
+  --card: #1e293b;
+  --text: #f1f5f9;
+  --muted: #94a3b8;
+  --accent: #2dd4bf;
+  --accent-dim: #0f766e;
+  --danger: #f87171;
+  --warning: #fbbf24;
+  --border: #334155;
+  --radius: 8px;
+  --gap: 12px;
+}
+body {
+  width: 380px;
+  background: var(--bg);
+  color: var(--text);
+  font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
+  font-size: 13px;
+  line-height: 1.45;
+  overflow-x: hidden;
+}
+#app { padding: 16px; }
+.header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 16px;
+}
+.brand { display: flex; align-items: center; gap: 10px; }
+.logo-icon { font-size: 22px; }
+.brand h1 { font-size: 18px; font-weight: 700; letter-spacing: -0.3px; }
+.brand p { color: var(--muted); font-size: 12px; margin-top: 2px; }
+.icon-btn {
+  background: transparent;
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  color: var(--text);
+  cursor: pointer;
+  padding: 6px 8px;
+  font-size: 14px;
+}
+.icon-btn:hover { background: var(--card); }
+
+.overview .card {
+  background: var(--card);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  padding: 16px;
+  margin-bottom: 16px;
+}
+.overview .label { color: var(--muted); font-size: 11px; text-transform: uppercase; letter-spacing: 0.5px; }
+.overview .big-number { font-size: 32px; font-weight: 800; margin: 6px 0; color: var(--accent); }
+.overview .sub { color: var(--muted); font-size: 12px; margin-top: 4px; }
+.progress-wrap { margin-top: 10px; height: 8px; background: #0f172a; border-radius: 4px; overflow: hidden; }
+.progress-bar { height: 100%; background: var(--accent); transition: width 0.3s ease; }
+
+h2 { font-size: 14px; font-weight: 600; margin: 14px 0 8px; }
+
+.tools-section, .add-usage-section, .trend-section { margin-bottom: 14px; }
+
+.tools-list { display: flex; flex-direction: column; gap: 8px; }
+.tool-item {
+  background: var(--card);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  padding: 12px;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+}
+.tool-left { display: flex; flex-direction: column; gap: 2px; }
+.tool-name { font-weight: 600; font-size: 13px; }
+.tool-meta { color: var(--muted); font-size: 11px; }
+.tool-right { text-align: right; }
+.tool-spend { font-weight: 700; font-size: 14px; }
+.tool-budget { font-size: 11px; color: var(--muted); }
+.tool-actions { display: flex; gap: 6px; margin-top: 6px; }
+.btn-small {
+  background: transparent;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  color: var(--text);
+  cursor: pointer;
+  padding: 4px 8px;
+  font-size: 11px;
+}
+.btn-small:hover { background: var(--border); }
+
+.form { display: flex; flex-direction: column; gap: 8px; }
+.form.compact { flex-direction: row; flex-wrap: wrap; gap: 6px; }
+.form.compact input, .form.compact select { flex: 1 1 120px; }
+.form.compact button { flex: 0 0 auto; }
+input, select, textarea {
+  background: #0f172a;
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  color: var(--text);
+  padding: 8px 10px;
+  font-size: 13px;
+  outline: none;
+  width: 100%;
+}
+input:focus, select:focus { border-color: var(--accent); }
+.btn-primary {
+  background: var(--accent-dim);
+  color: #fff;
+  border: none;
+  border-radius: var(--radius);
+  padding: 8px 12px;
+  font-size: 13px;
+  cursor: pointer;
+  font-weight: 600;
+}
+.btn-primary:hover { background: var(--accent); color: #000; }
+.btn-secondary {
+  background: transparent;
+  border: 1px solid var(--border);
+  color: var(--text);
+  border-radius: var(--radius);
+  padding: 8px 12px;
+  font-size: 13px;
+  cursor: pointer;
+}
+.btn-danger {
+  background: transparent;
+  border: 1px solid var(--danger);
+  color: var(--danger);
+  border-radius: var(--radius);
+  padding: 8px 12px;
+  font-size: 13px;
+  cursor: pointer;
+  width: 100%;
+}
+
+.trend-list { display: flex; flex-direction: column; gap: 6px; max-height: 180px; overflow-y: auto; }
+.trend-row {
+  display: flex;
+  justify-content: space-between;
+  padding: 6px 8px;
+  background: var(--card);
+  border-radius: 6px;
+  font-size: 12px;
+}
+.trend-row .day { color: var(--muted); }
+.trend-row .val { font-weight: 600; }
+
+.empty-state { text-align: center; padding: 30px 16px; color: var(--muted); }
+.empty-icon { font-size: 36px; margin-bottom: 8px; }
+.empty-state p { font-size: 13px; }
+.hidden { display: none !important; }
+
+.modal {
+  position: fixed;
+  inset: 0;
+  background: rgba(0,0,0,0.6);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 100;
+}
+.modal-content {
+  background: var(--card);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  padding: 16px;
+  width: 340px;
+}
+.modal-content h2 { margin-bottom: 12px; }
+.modal-actions { display: flex; justify-content: flex-end; gap: 8px; margin-top: 12px; }
+.danger-zone { margin-top: 14px; border-top: 1px solid var(--border); padding-top: 12px; }
+.row { display: flex; align-items: center; gap: 8px; margin-top: 4px; }
+
+::-webkit-scrollbar { width: 6px; }
+::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
@@ -0,0 +1,100 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>Cost.dev</title>
+  <link rel="stylesheet" href="popup.css">
+</head>
+<body>
+  <div id="app">
+    <header class="header">
+      <div class="brand">
+        <span class="logo-icon">💰</span>
+        <div>
+          <h1>Cost.dev</h1>
+          <p>AI Coding Cost Optimizer</p>
+        </div>
+      </div>
+      <div class="header-actions">
+        <button id="btn-settings" class="icon-btn" title="Budget & Settings">⚙️</button>
+      </div>
+    </header>
+
+    <section id="overview" class="overview">
+      <div class="card">
+        <div class="label">This Month</div>
+        <div class="big-number" id="total-spend">$0.00</div>
+        <div class="sub" id="budget-sub">Budget: $50.00</div>
+        <div class="progress-wrap">
+          <div class="progress-bar" id="budget-bar" style="width:0%"></div>
+        </div>
+        <div class="sub" id="projected-sub">Projected: $0.00</div>
+      </div>
+    </section>
+
+    <section id="tools-section" class="tools-section">
+      <h2>Your Tools</h2>
+      <div id="tools-list" class="tools-list"></div>
+      <form id="add-tool-form" class="form compact">
+        <input type="text" id="tool-name" placeholder="Tool name (e.g. Claude Code)" required>
+        <input type="number" id="tool-cost" placeholder="Monthly cost $" min="0" step="0.01" required>
+        <select id="tool-model">
+          <option value="fixed">Fixed plan</option>
+          <option value="usage">Usage-based</option>
+          <option value="hybrid">Hybrid</option>
+        </select>
+        <button type="submit" class="btn-primary">Add Tool</button>
+      </form>
+    </section>
+
+    <section id="add-usage-section" class="add-usage-section">
+      <h2>Log Usage</h2>
+      <form id="add-usage-form" class="form compact">
+        <select id="usage-tool" required>
+          <option value="" disabled selected>Select tool</option>
+        </select>
+        <input type="date" id="usage-date" required>
+        <input type="number" id="usage-amount" placeholder="Amount $" min="0" step="0.01" required>
+        <input type="text" id="usage-note" placeholder="Note (optional)">
+        <button type="submit" class="btn-primary">Log</button>
+      </form>
+    </section>
+
+    <section id="trend-section" class="trend-section">
+      <h2>Daily Breakdown</h2>
+      <div id="trend-list" class="trend-list"></div>
+    </section>
+
+    <div id="empty-state" class="empty-state hidden">
+      <div class="empty-icon">📭</div>
+      <p>No tools yet. Add one above to start tracking.</p>
+    </div>
+  </div>
+
+  <!-- Settings modal -->
+  <div id="settings-modal" class="modal hidden">
+    <div class="modal-content">
+      <h2>Budget & Settings</h2>
+      <form id="budget-form" class="form">
+        <label>Monthly Budget ($)</label>
+        <input type="number" id="budget-limit" min="0" step="1" required>
+        <label>Alert Threshold (%)</label>
+        <input type="number" id="budget-threshold" min="1" max="100" step="1" required>
+        <div class="row">
+          <input type="checkbox" id="budget-enabled" checked>
+          <label for="budget-enabled">Enable alerts</label>
+        </div>
+        <div class="modal-actions">
+          <button type="button" id="btn-close-settings" class="btn-secondary">Close</button>
+          <button type="submit" class="btn-primary">Save</button>
+        </div>
+      </form>
+      <div class="danger-zone">
+        <button id="btn-reset" class="btn-danger">Reset All Data</button>
+      </div>
+    </div>
+  </div>
+
+  <script type="module" src="popup.ts"></script>
+</body>
+</html>
@@ -0,0 +1,210 @@
+import type { AppState, Budget, ToolEntry, UsageRecord } from '../types'
+import {
+  loadState,
+  saveState,
+  addTool,
+  addUsage,
+  removeTool,
+  removeUsage,
+  setBudget,
+  sumMonthUsages,
+  sumToolMonthUsages,
+  dailyTotals,
+  projectedMonthEnd,
+  clearAll,
+} from '../storage'
+import { newId, DEFAULT_BUDGET, getMonthKey, getTodayKey } from '../types'
+
+// --- DOM refs ---
+const el = (id: string) => document.getElementById(id)!
+
+let state: AppState = { version: 1, tools: [], usages: [], budget: { ...DEFAULT_BUDGET } }
+
+async function init() {
+  state = await loadState()
+  render()
+  wireEvents()
+}
+
+function render() {
+  const month = getMonthKey()
+  const total = sumMonthUsages(state.usages, month)
+  const limit = state.budget.monthlyLimit
+  const projected = projectedMonthEnd(total)
+
+  // Overview
+  el('total-spend').textContent = `$${total.toFixed(2)}`
+  el('budget-sub').textContent = `Budget: $${limit.toFixed(2)}`
+  el('projected-sub').textContent = `Projected: $${projected.toFixed(2)}`
+  const pct = limit > 0 ? Math.min((total / limit) * 100, 100) : 0
+  el('budget-bar').style.width = `${pct}%`
+  el('budget-bar').style.background = pct > 100 ? 'var(--danger)' : pct > 80 ? 'var(--warning)' : 'var(--accent)'
+
+  // Tools list
+  const toolsList = el('tools-list')
+  toolsList.innerHTML = ''
+  if (state.tools.length === 0) {
+    el('empty-state').classList.remove('hidden')
+    el('tools-section').classList.add('hidden')
+    el('add-usage-section').classList.add('hidden')
+    el('trend-section').classList.add('hidden')
+  } else {
+    el('empty-state').classList.add('hidden')
+    el('tools-section').classList.remove('hidden')
+    el('add-usage-section').classList.remove('hidden')
+    el('trend-section').classList.remove('hidden')
+
+    for (const t of state.tools) {
+      const toolSpent = sumToolMonthUsages(state.usages, t.id, month)
+      const div = document.createElement('div')
+      div.className = 'tool-item'
+      div.innerHTML = `
+        <div class="tool-left">
+          <div class="tool-name">${escapeHtml(t.name)}</div>
+          <div class="tool-meta">${escapeHtml(t.billingModel)}${t.planName ? ' · ' + escapeHtml(t.planName) : ''}</div>
+          <div class="tool-actions">
+            <button class="btn-small" data-action="add-usage" data-tool="${t.id}">+ Usage</button>
+            <button class="btn-small" data-action="delete-tool" data-tool="${t.id}">Delete</button>
+          </div>
+        </div>
+        <div class="tool-right">
+          <div class="tool-spend">$${toolSpent.toFixed(2)}</div>
+          <div class="tool-budget">${t.monthlyCost > 0 ? 'Est: $' + t.monthlyCost.toFixed(2) + '/mo' : 'No estimate'}</div>
+        </div>
+      `
+      toolsList.appendChild(div)
+    }
+  }
+
+  // Usage tool selector
+  const usageTool = el('usage-tool') as HTMLSelectElement
+  const prevVal = usageTool.value
+  usageTool.innerHTML = '<option value="" disabled selected>Select tool</option>'
+  for (const t of state.tools) {
+    const opt = document.createElement('option')
+    opt.value = t.id
+    opt.textContent = t.name
+    usageTool.appendChild(opt)
+  }
+  if (prevVal) usageTool.value = prevVal
+
+  // Daily trend
+  const trendList = el('trend-list')
+  trendList.innerHTML = ''
+  const days = dailyTotals(state.usages, month)
+  if (days.length === 0) {
+    const empty = document.createElement('div')
+    empty.className = 'trend-row'
+    empty.innerHTML = '<span class="day">No data yet</span><span class="val">—</span>'
+    trendList.appendChild(empty)
+  } else {
+    for (const d of days) {
+      const row = document.createElement('div')
+      row.className = 'trend-row'
+      row.innerHTML = `<span class="day">${d.day}</span><span class="val">$${d.total.toFixed(2)}</span>`
+      trendList.appendChild(row)
+    }
+  }
+
+  // Settings form values
+  ;(el('budget-limit') as HTMLInputElement).value = String(state.budget.monthlyLimit)
+  ;(el('budget-threshold') as HTMLInputElement).value = String(Math.round(state.budget.alertThreshold * 100))
+  ;(el('budget-enabled') as HTMLInputElement).checked = state.budget.enabled
+}
+
+function wireEvents() {
+  el('add-tool-form').addEventListener('submit', async (e) => {
+    e.preventDefault()
+    const name = (el('tool-name') as HTMLInputElement).value.trim()
+    const cost = parseFloat((el('tool-cost') as HTMLInputElement).value)
+    const model = (el('tool-model') as HTMLSelectElement).value as ToolEntry['billingModel']
+    if (!name || isNaN(cost) || cost < 0) return
+    const tool: ToolEntry = {
+      id: newId(),
+      name,
+      monthlyCost: cost,
+      currency: 'USD',
+      billingModel: model,
+      lastUpdated: Date.now(),
+    }
+    await addTool(tool)
+    state = await loadState()
+    ;(el('add-tool-form') as HTMLFormElement).reset()
+    render()
+  })
+
+  el('add-usage-form').addEventListener('submit', async (e) => {
+    e.preventDefault()
+    const toolId = (el('usage-tool') as HTMLSelectElement).value
+    const date = (el('usage-date') as HTMLInputElement).value
+    const amount = parseFloat((el('usage-amount') as HTMLInputElement).value)
+    const note = (el('usage-note') as HTMLInputElement).value.trim()
+    if (!toolId || !date || isNaN(amount) || amount < 0) return
+    const record: UsageRecord = {
+      id: newId(),
+      toolId,
+      date,
+      amount,
+      note: note || undefined,
+      source: 'manual',
+      createdAt: Date.now(),
+    }
+    await addUsage(record)
+    state = await loadState()
+    ;(el('add-usage-form') as HTMLFormElement).reset()
+    ;(el('usage-date') as HTMLInputElement).value = getTodayKey()
+    render()
+  })
+
+  el('tools-list').addEventListener('click', async (e) => {
+    const btn = (e.target as HTMLElement).closest('button') as HTMLButtonElement | null
+    if (!btn) return
+    const action = btn.dataset.action
+    const toolId = btn.dataset.tool
+    if (!action || !toolId) return
+    if (action === 'delete-tool') {
+      await removeTool(toolId)
+      state = await loadState()
+      render()
+    } else if (action === 'add-usage') {
+      ;(el('usage-tool') as HTMLSelectElement).value = toolId
+      el('add-usage-section').scrollIntoView({ behavior: 'smooth' })
+    }
+  })
+
+  el('btn-settings').addEventListener('click', () => {
+    el('settings-modal').classList.remove('hidden')
+  })
+  el('btn-close-settings').addEventListener('click', () => {
+    el('settings-modal').classList.add('hidden')
+  })
+  el('budget-form').addEventListener('submit', async (e) => {
+    e.preventDefault()
+    const limit = parseFloat((el('budget-limit') as HTMLInputElement).value)
+    const threshold = parseInt((el('budget-threshold') as HTMLInputElement).value, 10) / 100
+    const enabled = (el('budget-enabled') as HTMLInputElement).checked
+    if (isNaN(limit) || isNaN(threshold)) return
+    const budget: Budget = { monthlyLimit: limit, currency: 'USD', alertThreshold: threshold, enabled }
+    await setBudget(budget)
+    state = await loadState()
+    el('settings-modal').classList.add('hidden')
+    render()
+  })
+  el('btn-reset').addEventListener('click', async () => {
+    if (!confirm('Delete ALL data? This cannot be undone.')) return
+    await clearAll()
+    state = await loadState()
+    render()
+  })
+}
+
+function escapeHtml(s: string): string {
+  const d = document.createElement('div')
+  d.textContent = s
+  return d.innerHTML
+}
+
+// Init default date
+;(el('usage-date') as HTMLInputElement).value = getTodayKey()
+
+init()
@@ -0,0 +1,90 @@
+import type { AppState, Budget, ToolEntry, UsageRecord } from './types'
+import { DEFAULT_BUDGET, getMonthKey } from './types'
+
+const STORAGE_KEY = 'costdev_state_v1'
+
+export async function loadState(): Promise<AppState> {
+  const res = await chrome.storage.local.get(STORAGE_KEY)
+  const stored = res[STORAGE_KEY] as Partial<AppState> | undefined
+  return {
+    version: 1,
+    tools: stored?.tools ?? [],
+    usages: stored?.usages ?? [],
+    budget: stored?.budget ?? { ...DEFAULT_BUDGET },
+    lastAlertAt: stored?.lastAlertAt,
+  }
+}
+
+export async function saveState(state: AppState): Promise<void> {
+  await chrome.storage.local.set({ [STORAGE_KEY]: state })
+}
+
+export async function addTool(tool: ToolEntry): Promise<void> {
+  const s = await loadState()
+  s.tools = [...s.tools, tool]
+  await saveState(s)
+}
+
+export async function updateTool(id: string, patch: Partial<ToolEntry>): Promise<void> {
+  const s = await loadState()
+  s.tools = s.tools.map((t) => (t.id === id ? { ...t, ...patch, lastUpdated: Date.now() } : t))
+  await saveState(s)
+}
+
+export async function removeTool(id: string): Promise<void> {
+  const s = await loadState()
+  s.tools = s.tools.filter((t) => t.id !== id)
+  s.usages = s.usages.filter((u) => u.toolId !== id)
+  await saveState(s)
+}
+
+export async function addUsage(record: UsageRecord): Promise<void> {
+  const s = await loadState()
+  s.usages = [...s.usages, record]
+  await saveState(s)
+}
+
+export async function removeUsage(id: string): Promise<void> {
+  const s = await loadState()
+  s.usages = s.usages.filter((u) => u.id !== id)
+  await saveState(s)
+}
+
+export async function setBudget(budget: Budget): Promise<void> {
+  const s = await loadState()
+  s.budget = budget
+  await saveState(s)
+}
+
+export function sumMonthUsages(usages: UsageRecord[], month = getMonthKey()): number {
+  return usages
+    .filter((u) => u.date.startsWith(month))
+    .reduce((sum, u) => sum + u.amount, 0)
+}
+
+export function sumToolMonthUsages(usages: UsageRecord[], toolId: string, month = getMonthKey()): number {
+  return usages
+    .filter((u) => u.toolId === toolId && u.date.startsWith(month))
+    .reduce((sum, u) => sum + u.amount, 0)
+}
+
+export function dailyTotals(usages: UsageRecord[], month = getMonthKey()): { day: string; total: number }[] {
+  const map = new Map<string, number>()
+  usages
+    .filter((u) => u.date.startsWith(month))
+    .forEach((u) => map.set(u.date, (map.get(u.date) ?? 0) + u.amount))
+  return Array.from(map.entries())
+    .map(([day, total]) => ({ day, total }))
+    .sort((a, b) => a.day.localeCompare(b.day))
+}
+
+export function projectedMonthEnd(currentTotal: number, today: Date = new Date()): number {
+  const day = today.getDate()
+  const daysInMonth = new Date(today.getFullYear(), today.getMonth() + 1, 0).getDate()
+  if (day <= 0 || daysInMonth <= 0) return currentTotal
+  return (currentTotal / day) * daysInMonth
+}
+
+export async function clearAll(): Promise<void> {
+  await chrome.storage.local.remove(STORAGE_KEY)
+}
@@ -0,0 +1,56 @@
+// Core types for Cost.dev
+
+export interface ToolEntry {
+  id: string
+  name: string
+  monthlyCost: number // in dollars, cents implied by decimals
+  currency: string
+  planName?: string
+  billingModel: 'fixed' | 'usage' | 'hybrid'
+  lastUpdated: number // timestamp
+}
+
+export interface UsageRecord {
+  id: string
+  toolId: string
+  date: string // YYYY-MM-DD
+  amount: number // dollars
+  note?: string
+  source: 'manual' | 'auto' | 'import'
+  createdAt: number
+}
+
+export interface Budget {
+  monthlyLimit: number // dollars
+  currency: string
+  alertThreshold: number // 0–1 fraction of monthlyLimit
+  enabled: boolean
+}
+
+export interface AppState {
+  tools: ToolEntry[]
+  usages: UsageRecord[]
+  budget: Budget
+  lastAlertAt?: number
+  version: 1
+}
+
+export const DEFAULT_BUDGET: Budget = {
+  monthlyLimit: 50,
+  currency: 'USD',
+  alertThreshold: 0.8,
+  enabled: true,
+}
+
+export function newId(): string {
+  return `${Date.now()}-${Math.random().toString(36).slice(2, 9)}`
+}
+
+export function getMonthKey(date = new Date()): string {
+  return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, '0')}`
+}
+
+export function getTodayKey(): string {
+  const d = new Date()
+  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`
+}
@@ -0,0 +1,15 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "lib": ["ES2020", "DOM", "DOM.Iterable"],
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "noEmit": true,
+    "types": ["chrome"]
+  },
+  "include": ["src"]
+}
@@ -0,0 +1,11 @@
+import { defineConfig } from 'vite'
+import { crx } from '@crxjs/vite-plugin'
+import manifest from './src/manifest.json' with { type: 'json' }
+
+export default defineConfig({
+  build: {
+    outDir: 'dist',
+    emptyOutDir: true,
+  },
+  plugins: [crx({ manifest })],
+})