# NextExpense — AI-Powered Expense Tracker

> A production-ready, mobile-first Progressive Web App (PWA) for expense management with passwordless OTP login, AI receipt extraction (Gemini / OpenAI-compatible), and CSV/PDF email reporting with receipt images.

**Tech Stack:** Go 1.23+ · HTMX · SQLite (pure Go) · Google Gemini / OpenAI · PWA

---

## 🚀 One-Command Install

```bash
curl -fsSL https://git.lohmar.co.uk/cclohmar/NextExpense/raw/branch/main/install.sh | bash -s -- --install
```

Or from a local clone:

```bash
./install.sh --install
```

Running without flags shows help:

```bash
./install.sh          # Show help
./install.sh --help   # Same
```

The installer will:

1. Clone the repo to `/opt/nextexpense/`
2. Build the binary (pure Go, no CGO, no dependencies)
3. Ask which AI provider to use:

   ```
   1) Google Gemini  (cloud API, needs API key)
   2) OpenAI / Compatible  (OpenAI, Perplexity, Groq, etc.)
   ```

4. Prompt for SMTP settings (for OTP emails and report delivery)
5. Create `/opt/nextexpense/.env` with all configuration
6. Set up a systemd service that auto-starts on boot
7. Start NextExpense

**Result:** A fully configured, always-running expense tracker at `http://YOUR_SERVER:8080`.

---

## 🔄 Updating

```bash
./install.sh --update
```

Update pulls the latest code, copies updated templates/static, rebuilds the binary, automatically backs up the database, and restarts the service.

## 🗑️ Uninstalling

```bash
./install.sh --remove
```

Stops the service, removes the systemd unit, and deletes `/opt/nextexpense/` (asks for confirmation).

---

## 🔧 Building from Source (install.sh does this automatically)

The installer automatically installs Go (if missing) and builds from source.  
No pre-built binaries are distributed — building from source guarantees the latest code compiled for your exact platform.

### Manual Build

```bash
git clone https://git.lohmar.co.uk/cclohmar/NextExpense.git
cd NextExpense

# Build for your current platform
CGO_ENABLED=0 go build -buildvcs=false -ldflags="-s -w" -o app .

# Cross-compile for any platform (no extra tools needed!)
CGO_ENABLED=0 GOOS=linux GOARCH=arm64 go build -buildvcs=false -ldflags="-s -w" -o app-linux-arm64 .
CGO_ENABLED=0 GOOS=darwin GOARCH=amd64 go build -buildvcs=false -ldflags="-s -w" -o app-darwin-amd64 .
CGO_ENABLED=0 GOOS=darwin GOARCH=arm64 go build -buildvcs=false -ldflags="-s -w" -o app-darwin-arm64 .
```

The binary is fully static — zero runtime dependencies, no CGO, no libc.

---

## ⚙️ Configuration

Configuration is via environment variables in `.env`. The install script builds this for you interactively.

| Variable | Required | Default | Description |
|----------|----------|---------|-------------|
| `PORT` | No | `8080` | HTTP server port |
| `BASE_URL` | No | `http://localhost:8080` | Public URL for email links |
| **AI Provider** | | | |
| `AI_PROVIDER` | No | `gemini` | `gemini` or `openai` |
| `GEMINI_API_KEY` | For Gemini | — | Google Gemini API key |
| `OPENAI_API_KEY` | For OpenAI | — | API key (omit for Ollama via OpenAI compat) |
| `AI_MODEL` | For OpenAI | `gpt-4o-mini` | Model name |
| `AI_BASE_URL` | For OpenAI | `https://api.openai.com/v1` | API endpoint |
| **SMTP** | | | |
| `SMTP_HOST` | See note | — | SMTP server hostname |
| `SMTP_PORT` | See note | `587` | SMTP server port |
| `SMTP_USER` | See note | — | SMTP username |
| `SMTP_PASS` | See note | — | SMTP password |

> **Note:** SMTP is optional — without it, OTP codes are logged to the server console for testing and reports cannot be emailed.

---

## 🚀 Usage

### 1. Start the Server

```bash
# If installed via systemd:
systemctl start nextexpense

# Or run directly:
./app
```

### 2. Open in Browser

Navigate to `http://YOUR_SERVER:8080`

### 3. Full Acceptance Flow

```
1. Enter your email → click "Send Verification Code"
2. Check your inbox (or server log) for the 6-digit OTP
3. Enter OTP → click "Verify Code"
4. Create a month (e.g. "July 2026") → click "Open"
5. Click "+ New" to add an event → set claim currency + conversion sample
6. Click "Open" on the event
7. Tap "📷 Camera" or "📁 Upload" to add a receipt
8. AI extracts amount, merchant, category, date → form is pre-filled
9. Click "Save Expense"
10. Back on the month view, click "Generate Monthly Report"
11. Monthly ZIP contains CSV + PDF report + all receipt images
```

---

## 📡 API Reference

### Public

| Method | Path | Description |
|--------|------|-------------|
| `GET` | `/` | Landing page |
| `POST` | `/request-otp` | Request OTP code |
| `POST` | `/verify-otp` | Verify OTP and create session |
| `POST` | `/logout` | Clear session |

### Protected (requires session)

| Method | Path | Description |
|--------|------|-------------|
| `GET` | `/dashboard` | Month list |
| `POST` | `/months` | Create month |
| `GET` | `/months/{mid}` | View month + events |
| `PUT` | `/months/{mid}` | Update month |
| `DELETE` | `/months/{mid}` | Delete month |
| `POST` | `/months/{mid}/events` | Create event |
| `PUT` | `/months/{mid}/events/{eid}` | Update event |
| `DELETE` | `/months/{mid}/events/{eid}` | Delete event |
| `GET` | `/months/{mid}/events/{eid}/expenses` | View event + expenses |
| `POST` | `/months/{mid}/events/{eid}/generate` | Generate event report |
| `POST` | `/months/{mid}/generate` | Generate monthly report |
| `POST` | `/expenses/upload` | Upload receipt image/PDF |
| `POST` | `/expenses` | Save expense |
| `GET` | `/expenses/{id}/edit` | Get edit form |
| `PUT` | `/expenses/{id}` | Update expense |
| `DELETE` | `/expenses/{id}` | Delete expense |

---

## 🏗️ Project Structure

```
/opt/nextexpense/
├── app                      # Compiled binary
├── .env                     # Configuration (optional)
├── backups/                 # Automatic DB backups (from -update)
├── templates/               # Go HTML templates
├── static/                  # CSS, icons, favicon, service worker
├── templates/               # Go HTML templates
├── static/                  # CSS, icons, favicon, service worker
│   ├── css/style.css
│   ├── favicon.svg          # Rx logo
│   ├── manifest.json
│   ├── sw.js
│   └── icons/
├── storage/                 # Uploaded receipt images (runtime)
├── install.sh               # Installer script
├── Makefile                 # Build targets
└── contrib/
    └── nextexpense.service  # Systemd service file
```

---

## 🧩 Features

### 🔐 Passwordless OTP Authentication
- Email-based 6-digit code, 5-minute expiry
- 3 failed attempts → 1-minute cooldown
- HTTP-only session cookie, 24h TTL

### 🤖 AI Receipt Extraction
- **Google Gemini** (default) — cloud vision API
- **OpenAI-compatible** — works with OpenAI, Perplexity, Groq, Together AI, etc.
- Supports: JPEG, PNG, WebP, HEIC, PDF (email receipts from Uber, etc.)

### 💱 Currency Conversion
- Sample-based: enter a real receipt amount and what you were charged
- System computes the rate automatically
- Each expense stores original + converted amount

### 📧 Email Reporting
- CSV or PDF report
- Receipt images bundled as ZIP (`expense-{event}-images.zip`)
- Filenames: `expense-{event}-report.csv`, `expense-{event}-report.pdf`
- Item numbers match between report rows and ZIP images

### 📱 Progressive Web App
- Installable on mobile home screen
- Camera capture + gallery upload
- Dark "Terminal Mint" theme (`#0F172A` base)
- Rx favicon in emerald green

---

## 🗄️ Database

SQLite, auto-created on first run — 5 tables: `users`, `auth_otps`, `months`, `events`, `expenses`.

---

## 🔒 Security

| Area | Implementation |
|------|---------------|
| Sessions | `crypto/rand` tokens, in-memory, 24h TTL |
| OTP | `crypto/rand` codes, 5min expiry, lockout after 3 failures |
| Cookies | HTTP-only, SameSite=Lax, path-restricted |
| SQL | Parameterized queries everywhere |
| Uploads | Magic byte validation, max 10MB, UUID filenames |
| Config | `.env` is optional — app runs with defaults if absent |

---

*Built with Go, HTMX, SQLite and ❤️*