feat: initial @contact-api/vercel package

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          cache: npm
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Type check
+        run: npm run typecheck
+
+      - name: Run tests
+        run: npm run test:coverage

.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+node_modules
+dist
+dist-ssr
+*.local
+
+coverage/
+
+# Editor directories and files
+.vscode/*
+!.vscode/extensions.json
+.idea
+.DS_Store
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?

README.md

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+# Contact API Vercel
+
+Deployable **multi-provider** contact form API.
+
+## Features
+- Single `POST /api/contact` endpoint - drop into any project.
+- Multi-provider support: Resend and Nodemailer (SMTP).
+- CORS support via `ALLOWED_ORIGINS`.
+- Input validation with descriptive error responses.
+- Rate limiting via Vercel WAF to prevent spam and abuse.
+- Honeypot protection.
+> **Note:** To utilize the honeypot, include a hidden input field named `fax_number` in your frontend and keep it empty when submitting the form.
+
+## Usage
+```js
+await fetch("https://your-deployment.vercel.app/api/contact", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({
+        email: "sender@example.com",  // required
+        message: "Your message here", // required
+        subject: "Hello",             // optional
+        name: "Your name",            // optional
+        fax_number: ""                // optional; must be empty
+    })
+});
+```
+
+## Response
+| Status | Body |
+| ------ | ---- |
+| 200    | { success: true, message: "Message sent successfully" } |
+| 400    | { error: "Invalid or missing fields" } |
+| 403    | { error: "Forbidden" } |
+| 405    | { error: "Method not allowed" } |
+| 415    | { error: "Unsupported Media Type" } |
+| 429    | { error: "Too many requests. Please try again later" } |
+| 500    | { error: "Message delivery failed. Please try again later" } |
+| 503    | { error: "Service temporarily unavailable" } |
+
+## Deployment & Configuration
+
+### Prerequisites
+- Node.js 20+
+- Vercel
+- An email provider
+    - **Resend:** API key and verified domain.
+    - **Nodemailer:** Valid SMTP settings (`host`, `port`, `auth.user`, `auth.pass`, and `secure` when needed).
+
+### 1. Clone & Install
+```bash
+git clone https://github.com/masonlet/contact-api.git
+cd contact-api
+npm install
+```
+
+### 2. Configure `.env`
+Copy `.env.example` to `.env` and fill Environment Variables. Shared values are **required**; provider-specific values depend on `EMAIL_PROVIDER`.
+
+| Variable          | Description |
+| ----------------- | ----------- |
+| `FROM_EMAIL`      | Sender address |
+| `TO_EMAIL`        | Recipient email addresses, comma-separated. |
+| `ALLOWED_ORIGINS` | Allowed CORS origins, comma-separated. Leave empty to block all cross-origin requests. |
+| `EMAIL_PROVIDER`  | Email provider to use: `resend` or `nodemailer`. |
+| `RESEND_API_KEY`  | Resend API key, required when `EMAIL_PROVIDER=resend`. |
+| `SMTP_CONFIG`     | JSON string of Nodemailer SMTP config, required when `EMAIL_PROVIDER=nodemailer`. |
+
+### Local Development
+```bash
+npm run typecheck     # TypeScript type check
+npm run test          # Run Vitest tests
+npm run test:watch    # Run Vitest in watch mode
+npm run test:coverage # Run Vitest in coverage mode
+```
+
+## License
+MIT License - see [LICENSE](./LICENSE) for details.

api/contact/index.ts

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+import type { VercelRequest, VercelResponse } from "@vercel/node";
+import { checkRateLimit } from "@vercel/firewall";
+import { evaluateCors } from "@contact-api/core/cors";
+import { handleContact } from "@contact-api/core/handler";
+import { getEmailConfig, config } from "../../src/config.js";
+
+export default async (req: VercelRequest, res: VercelResponse): Promise<void> => {
+  const cors = evaluateCors(
+    { method: req.method ?? "", headers: req.headers as Record<string, string | undefined>, body: req.body },
+    config.allowedOrigins
+  );
+
+  for (const [key, value] of Object.entries(cors.headers)) res.setHeader(key, value);
+
+  if (cors.outcome === "preflight") {
+    res.status(cors.status!).end();
+    return;
+  }
+  if (cors.outcome === "forbidden") {
+    res.status(403).json({ error: "Forbidden" });
+    return;
+  }
+
+  const { rateLimited } = await checkRateLimit("contact-form-limit");
+  if (rateLimited) {
+    res.status(429).json({ error: "Too many requests. Please try again later" });
+    return;
+  }
+
+  const result = await handleContact(
+    { method: req.method ?? "", headers: req.headers as Record<string, string | undefined>, body: req.body },
+    { emailConfig: getEmailConfig(config) }
+  );
+
+  res.status(result.status);
+  if (result.body !== null) res.json(result.body);
+  else res.end();
+};