MarginLog — Resale Profit Tracker

marginlog.net

MarginLog is a web app for resellers (eBay, Poshmark, Mercari, Depop, Etsy, Facebook Marketplace, Vinted) to track sales, calculate real profit after fees, and understand their business performance — without a spreadsheet.

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What it does

Feature	Description
Log a sale	Record item, platform, sale price, cost of goods, shipping, and date
Auto fee calculation	Platform fees deducted automatically — see true net profit, not gross revenue
Dashboard	Monthly profit, margin %, top categories, chart of sales over time
Sales history	Full list of logged sales with delete and return marking
Expenses tracking	Log business expenses (packaging, mileage, subscriptions)
Sourcing trips	Group sales by the haul they came from
Haul calculator	Split a bulk purchase cost across multiple items to get per-item COGS
Bundle logger	Log a multi-item bundle as a single sale
CSV import	Bulk upload sales from any platform export (flexible column name matching)
CSV export	Download all sales as a spreadsheet for tax time
Free calculators	Public profit calculators for all 7 platforms — no login needed

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Plans

	Free	Pro ($9.99/month)
Sales logged	20/month	Unlimited
Dashboard & analytics	✅	✅
CSV import & export	✅	✅
Expenses & trips	✅	✅

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Tech stack

Layer	Technology
Framework	Next.js 16 (App Router, Server Actions)
Language	TypeScript
Styling	Tailwind CSS
Database	Supabase (Postgres + RLS)
Auth	Supabase Auth (email/password)
Payments	Stripe (Checkout + Customer Portal + Webhooks)
Email	Resend
Error monitoring	Sentry
Hosting	Vercel
Charts	Recharts

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Local setup

1. Clone and install

git clone https://github.com/AhmedSaqib/deposit-defender.git
cd deposit-defender
npm install

2. Environment variables

Create .env.local with the following:

# Supabase
NEXT_PUBLIC_SUPABASE_URL=https://your-project.supabase.co
NEXT_PUBLIC_SUPABASE_ANON_KEY=your-anon-key
SUPABASE_SERVICE_ROLE_KEY=your-service-role-key

# Stripe
STRIPE_SECRET_KEY=sk_test_...
NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY=pk_test_...
STRIPE_PRICE_ID=price_...
STRIPE_WEBHOOK_SECRET=whsec_...

# Site
NEXT_PUBLIC_SITE_URL=http://localhost:3000

# Email (Resend)
RESEND_API_KEY=re_...

# Sentry (optional locally)
SENTRY_AUTH_TOKEN=...

3. Database

Run supabase-schema.sql in your Supabase SQL editor. It creates:

• sales — sale records with platform, pricing, status
• expenses — business expense records
• sourcing_trips — sourcing trip groupings
• subscriptions — Stripe subscription state (managed by webhook)

4. Run

npm run dev

Open http://localhost:3000.

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Project structure

src/
├── app/
│   ├── page.tsx              # Landing page
│   ├── dashboard/            # Main analytics dashboard
│   ├── log/                  # Log a sale form
│   ├── sales/                # Sales history
│   ├── import/               # CSV bulk import
│   ├── expenses/             # Expense tracking
│   ├── trips/                # Sourcing trips
│   ├── haul/                 # Haul cost splitter
│   ├── bundle/               # Bundle logger
│   ├── calculators/          # Public fee calculators (SEO)
│   ├── api/
│   │   ├── stripe/           # checkout, webhook, portal
│   │   ├── export/           # CSV export
│   │   └── contact/          # Contact form (Resend)
│   ├── login/ signup/        # Auth pages
│   └── terms/ privacy/       # Legal pages
├── components/
│   ├── nav.tsx               # Top navigation with billing state
│   ├── app-footer.tsx        # Footer (Contact / Terms / Privacy)
│   ├── billing-button.tsx    # Upgrade / Pro / Pro-ending button
│   ├── upgrade-button.tsx    # Standalone upgrade CTA
│   ├── import-form.tsx       # CSV import UI
│   ├── haul-calculator.tsx
│   └── bundle-form.tsx
└── lib/
    ├── actions.ts            # All server actions (logSale, importSales, etc.)
    ├── subscription.ts       # Stripe gating helpers (canLogSale, getMonthlyCount)
    ├── platform-fees.ts      # Fee rates, profit/ROI calculation helpers
    ├── csv-import.ts         # CSV parsing with flexible column name matching
    ├── calculator-config.ts  # Per-platform calculator content + FAQ copy
    └── supabase/
        ├── server.ts         # SSR Supabase client
        ├── client.ts         # Browser Supabase client
        └── admin.ts          # Service-role client (webhook writes, bypasses RLS)

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Stripe webhook (local testing)

stripe listen --forward-to localhost:3000/api/stripe/webhook

Events handled:

• checkout.session.completed — create/upgrade subscription record
• customer.subscription.updated — sync cancel state and period end
• customer.subscription.deleted — mark subscription as free

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Deployment

Hosted on Vercel. Push to main → auto-deploys.

All environment variables above must be set in Vercel project settings. The Stripe webhook endpoint should point to https://marginlog.net/api/stripe/webhook.