import { NextRequest, NextResponse } from "next/server";
import { cookies } from "next/headers";
import { requireAdmin } from "@/lib/auth/auth";

const TIKTOK_OAUTH_STATE_COOKIE = "tiktok-oauth-state";

function escapeHtml(value: unknown) {
  return String(value ?? "")
    .replaceAll("&", "&")
    .replaceAll("<", "&lt;")
    .replaceAll(">", "&gt;")
    .replaceAll('"', "&quot;")
    .replaceAll("'", "&#39;");
}

/**
 * GET /api/auth/tiktok/callback
 * Handles the OAuth callback from TikTok.
 * Exchanges the authorization code for access + refresh tokens.
 * Displays the tokens so you can copy them to your .env file.
 */
export async function GET(request: NextRequest) {
  await requireAdmin();

  const { searchParams } = new URL(request.url);
  const code = searchParams.get("code");
  const error = searchParams.get("error");

  const cookieStore = await cookies();
  const expectedState = cookieStore.get(TIKTOK_OAUTH_STATE_COOKIE)?.value;
  const state = searchParams.get("state");
  cookieStore.delete(TIKTOK_OAUTH_STATE_COOKIE);

  if (!expectedState || !state || state !== expectedState) {
    return NextResponse.json({ error: "Invalid OAuth state" }, { status: 400 });
  }

  if (error) {
    return NextResponse.json(
      { error, description: searchParams.get("error_description") },
      { status: 400 }
    );
  }

  if (!code) {
    return NextResponse.json(
      { error: "No authorization code received" },
      { status: 400 }
    );
  }

  const clientKey = process.env.TIKTOK_CLIENT_KEY;
  const clientSecret = process.env.TIKTOK_CLIENT_SECRET;
  const redirectUri = `${process.env.BASE_URL}/api/auth/tiktok/callback`;

  if (!clientKey || !clientSecret) {
    return NextResponse.json(
      { error: "TIKTOK_CLIENT_KEY or TIKTOK_CLIENT_SECRET not set" },
      { status: 500 }
    );
  }

  // Exchange the code for tokens
  const tokenRes = await fetch(
    "https://open.tiktokapis.com/v2/oauth/token/",
    {
      method: "POST",
      headers: { "Content-Type": "application/x-www-form-urlencoded" },
      body: new URLSearchParams({
        client_key: clientKey,
        client_secret: clientSecret,
        code,
        grant_type: "authorization_code",
        redirect_uri: redirectUri,
      }),
    }
  );

  const tokenData = (await tokenRes.json()) as Record<string, unknown>;

  if (tokenData.error) {
    return NextResponse.json(
    { error: tokenData.error, description: tokenData.error_description },
      { status: 400 }
    );
  }

  // Return an HTML page showing the tokens to copy
  const html = `
<!DOCTYPE html>
<html>
<head><title>TikTok OAuth Success</title></head>
<body style="font-family: system-ui; max-width: 600px; margin: 40px auto; padding: 20px; background: #0a0a0a; color: #e5e5e5;">
  <h1 style="color: #22c55e;">✅ TikTok OAuth Success!</h1>
  <p>Copy these values to your <code>.env</code> file:</p>
  
  <div style="background: #1a1a1a; padding: 16px; border-radius: 8px; margin: 16px 0; word-break: break-all;">
    <p><strong>TIKTOK_ACCESS_TOKEN=</strong><br/><code>${escapeHtml(tokenData.access_token)}</code></p>
    <p><strong>TIKTOK_REFRESH_TOKEN=</strong><br/><code>${escapeHtml(tokenData.refresh_token)}</code></p>
    <p><strong>TIKTOK_OPEN_ID=</strong><br/><code>${escapeHtml(tokenData.open_id)}</code></p>
  </div>

  <p style="color: #a3a3a3; font-size: 14px;">
    Access token expires in ${Math.floor(Number(tokenData.expires_in ?? 0) / 3600)} hours.<br/>
    Refresh token expires in ${Math.floor(Number(tokenData.refresh_expires_in ?? 0) / 86400)} days.<br/>
    The server will auto-refresh the access token using the refresh token.
  </p>

  <details style="margin-top: 20px;">
    <summary style="cursor: pointer;">Full response</summary>
    <pre style="background: #1a1a1a; padding: 12px; border-radius: 6px; overflow-x: auto;">${escapeHtml(JSON.stringify(tokenData, null, 2))}</pre>
  </details>
</body>
</html>`;

  return new NextResponse(html, {
    headers: { "Content-Type": "text/html" },
  });
}