import type { NextConfig } from "next";

const s3Host = process.env.S3_ENDPOINT
  ? new URL(process.env.S3_ENDPOINT).hostname
  : "";

// Derive the Clerk frontend API host so the CSP allowlist always matches the
// active environment. When a custom Clerk frontend API domain is configured in
// the Clerk dashboard (e.g. clerk.testbed.mk), it is resolved at runtime by
// clerk-js and can NOT be derived from the publishable key — so it must be
// provided explicitly via NEXT_PUBLIC_CLERK_FAPI_HOST. Otherwise Clerk
// supports two publishable key formats:
//
//   1) "Encoded" form (older):  pk_test_<base64slug>$
//      The base64 portion decodes to "<slug>.clerk.accounts.dev" (test)
//      or "<slug>.clerk.services" (live). Trailing '$' is a separator.
//
//   2) "Readable" form (newer): pk_test_<slug>-<randomSuffix>
//      -> <slug>.clerk.accounts.dev (test) or <slug>.clerk.services.
//      The slug may itself contain hyphens and digits, so only the
//      final dash-group is captured as the suffix.
function clerkFrontendApiHost(): string | null {
  const custom = process.env.NEXT_PUBLIC_CLERK_FAPI_HOST?.trim();
  if (custom) {
    try {
      const host = new URL(custom.includes("://") ? custom : `https://${custom}`).hostname;
      if (host) return host;
    } catch {
      // fall through to derivation from the publishable key
    }
  }

  const key = process.env.NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY;
  if (!key) return null;

  // Form 1: base64-encoded FAPI URL. Match everything between the
  // 'pk_test_'/'pk_live_' prefix and an optional trailing '$'.
  const enc = key.match(/^pk_(test|live)_([A-Za-z0-9+/=_-]+)\$?$/);
  if (enc) {
    const b64 = enc[2].replace(/-/g, "+").replace(/_/g, "/");
    if (/^[A-Za-z0-9+/=]+$/.test(b64)) {
      try {
        const padded = b64 + "=".repeat((4 - (b64.length % 4)) % 4);
        const decoded = Buffer.from(padded, "base64").toString("utf8");
        // If the decoded string doesn't look like a Clerk FAPI host
        // (e.g. it's garbage from decoding a non-base64 readable-form
        // key), fall through to form 2 rather than returning null.
        const fapi = decodeFapiHost(decoded);
        if (fapi) return fapi;
      } catch {
        // fall through to form 2
      }
    }
    // fall through to form 2 if the slug is non-base64 (e.g. readable form)
  }

  // Form 2: readable slug + random suffix.
  const m = key.match(/^pk_(test|live)_(.+?)-([a-z0-9]+)$/i);
  if (!m) return null;
  const slug = m[2].toLowerCase();
  return m[1].toLowerCase() === "test"
    ? `${slug}.clerk.accounts.dev`
    : `${slug}.clerk.services`;
}

function decodeFapiHost(decoded: string): string | null {
  // The decoded string is the FAPI host (e.g.
  // 'useful-louse-74.clerk.accounts.dev$'). Note: the encoded base64
  // payload always carries the literal FAPI host regardless of test vs
  // live mode — both `pk_test_...` and `pk_live_...` can decode to an
  // '.accounts.dev' host when the deployment is on the test endpoint.
  // We accept either well-known Clerk FAPI host pattern.
  const host = decoded.trim().replace(/\$$/, "").trim().toLowerCase();
  if (host.endsWith(".clerk.accounts.dev") || host.endsWith(".clerk.services")) {
    return host;
  }
  return null;
}

const clerkFapiHost = clerkFrontendApiHost();

const csp = [
  "default-src 'self'",
  // Clerk user avatars are served from img.clerk.com; S3 hosts are
  // also allowed for memorial uploads. data:/blob: for in-app previews.
  "img-src 'self' data: blob: https://img.clerk.com https:",
  "font-src 'self' data:",
  "style-src 'self' 'unsafe-inline'",
  // script-src: must include the Clerk FAPI host because Clerk JS is
  // loaded from <fapiHost>/npm/@clerk/clerk-js@<v>/dist/clerk.browser.js
  "script-src 'self' 'unsafe-inline' 'unsafe-eval'" +
    (clerkFapiHost ? ` https://${clerkFapiHost}` : ""),
  // connect-src: Clerk JS talks to <fapiHost> for all session calls.
  "connect-src 'self' https://api.clerk.com" +
    (clerkFapiHost ? ` https://${clerkFapiHost} wss://${clerkFapiHost}` : ""),
  "frame-ancestors 'self'",
].join("; ");

const securityHeaders = [
  { key: "Strict-Transport-Security", value: "max-age=63072000; includeSubDomains; preload" },
  { key: "X-Frame-Options", value: "SAMEORIGIN" },
  { key: "X-Content-Type-Options", value: "nosniff" },
  { key: "Referrer-Policy", value: "strict-origin-when-cross-origin" },
  { key: "Permissions-Policy", value: "camera=(), microphone=(), geolocation=()" },
  { key: "Content-Security-Policy", value: csp },
];

const nextConfig: NextConfig = {
  output: "standalone",
  poweredByHeader: false,
  compress: true,
  images: {
    remotePatterns: [
      { protocol: "https", hostname: "img.clerk.com" },
      ...(s3Host ? [{ protocol: "https", hostname: s3Host }] : []),
    ] as NonNullable<NonNullable<NextConfig["images"]>["remotePatterns"]>,
  },
  async headers() {
    return [
      {
        source: "/:path*",
        headers: securityHeaders,
      },
    ];
  },
};

export default nextConfig;