Guida rapida — Genera la tua prima immagine OG

# Your website backend .env
FASTOG_API_KEY=sk_your_full_api_key
FASTOG_HMAC_SECRET=a1b2c3d4e5f6...  # 64 chars
FASTOG_API_URL=https://fastog.com/api/v1/og

// lib/fastog-signer.js
import crypto from "crypto";

// RFC-3986 encode (encodeURIComponent leaves !'()* unencoded).
const enc = (s) =>
    encodeURIComponent(s).replace(
        /[!'()*]/g,
        (c) => "%" + c.charCodeAt(0).toString(16).toUpperCase(),
    );

export function generateOgImageUrl(params) {
    const baseUrl = process.env.FASTOG_API_URL;
    const apiKey = process.env.FASTOG_API_KEY;
    const hmacSecret = process.env.FASTOG_HMAC_SECRET;

    const all = { ...params, key: apiKey };

    // Canonical: every param (except s), sorted, RFC-3986 encoded, joined with "&".
    const pairs = [];
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v])
            pairs.push(`${enc(k)}=${enc(vv)}`);
    }
    pairs.sort();
    const canonical = pairs.join("&");

    // Content-signed: message = path + canonical query. No timestamp.
    const signature = crypto
        .createHmac("sha256", hmacSecret)
        .update(`GET/api/v1/og\n${canonical}`)
        .digest("hex");

    const url = new URL(baseUrl);
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v])
            url.searchParams.append(k, vv);
    }
    url.searchParams.set("s", signature);
    return url.toString();
}

// app/Services/QuickogSigner.php
function generateOgImageUrl(array $params): string
{
    $baseUrl = config('services.fastog.api_url', 'https://fastog.com/api/v1/og');
    $apiKey = config('services.fastog.api_key');
    $hmacSecret = config('services.fastog.hmac_secret');

    $all = array_merge($params, ['key' => $apiKey]);

    // Canonical: every param except s, keys sorted (array values sorted too),
    // RFC-3986 encoded, joined with '&'. Content-signed — no timestamp.
    $pairs = [];
    foreach ($all as $k => $v) {
        $values = is_array($v) ? $v : [$v];
        sort($values, SORT_STRING);
        foreach ($values as $vv) {
            $pairs[] = rawurlencode((string) $k) . '=' . rawurlencode((string) $vv);
        }
    }
    sort($pairs, SORT_STRING);
    $canonical = implode('&', $pairs);

    $signature = hash_hmac('sha256', 'GET/api/v1/og' . "\n" . $canonical, $hmacSecret);

    return $baseUrl . '?' . http_build_query(array_merge($all, ['s' => $signature]));
}

# utils/fastog.py
import hmac
import hashlib
import os
from urllib.parse import quote, urlencode

def _enc(s):
    return quote(str(s), safe='-._~')  # RFC-3986: only unreserved chars

def generate_og_image_url(params: dict) -> str:
    base_url = os.environ['FASTOG_API_URL']
    api_key = os.environ['FASTOG_API_KEY']
    hmac_secret = os.environ['FASTOG_HMAC_SECRET']

    all_params = {**params, 'key': api_key}

    # Canonical: every param except s, sorted, RFC-3986 encoded, joined with '&'.
    pairs = []
    for k, v in all_params.items():
        for vv in sorted(v if isinstance(v, list) else [v]):
            pairs.append(f"{_enc(k)}={_enc(vv)}")
    canonical = '&'.join(sorted(pairs))

    # Content-signed: message = path + canonical query. No timestamp.
    signature = hmac.new(
        hmac_secret.encode(),
        f"GET/api/v1/og\n{canonical}".encode(),
        hashlib.sha256,
    ).hexdigest()

    return f"{base_url}?{urlencode({**all_params, 's': signature})}"

// app/blog/[slug]/page.tsx
import { generateOgImageUrl } from "@/lib/fastog-signer";

export async function generateMetadata({ params }) {
    const post = await getPost(params.slug);

    const ogImageUrl = generateOgImageUrl({
        template: "blog",
        title: post.title,
        subtitle: post.excerpt,
        author: post.author.name,
    });

    return {
        title: post.title,
        description: post.excerpt,
        openGraph: {
            images: [ogImageUrl],
        },
    };
}

{{-- resources/views/blog/show.blade.php --}}
@php
    $ogImageUrl = generateOgImageUrl([
        'template' => 'blog',
        'title' => $post->title,
        'subtitle' => $post->excerpt,
        'author' => $post->author->name,
    ]);
@endphp

<head>
    <meta property="og:image" content="{{ $ogImageUrl }}" />
    <meta property="og:title" content="{{ $post->title }}" />
    <meta property="og:description" content="{{ $post->excerpt }}" />
</head>

{# blog/post_detail.html #}
{% load fastog_tags %}

<head>
    <meta property="og:image" content="{% generate_og_image_url post %}" />
    <meta property="og:title" content="{{ post.title }}" />
    <meta property="og:description" content="{{ post.excerpt }}" />
</head>

# Generate a test URL
node -e "
const { generateOgImageUrl } = require('./lib/fastog-signer');
console.log(generateOgImageUrl({ title: 'Test', template: 'default' }));
"

# Test with curl
curl "https://fastog.com/api/v1/og?title=Test&key=sk_quick_123abc&s=<sig>"

if (response.status === 401) {
    const error = await response.json();

    switch (error.code) {
        case "missing_signature":
            // URL is missing `key` or `s` — re-generate it with your signer.
            break;
        case "invalid_signature":
            // A param changed after signing, or the secret doesn't match.
            // Re-sign the URL after any content change; verify the secret on both sides.
            break;
    }
}