falah-mobile/src/app/api/auth/[provider]/route.ts

import { NextRequest, NextResponse } from "next/server";
import { cookies } from "next/headers";
import {
  type Provider,
  PROVIDER_CONFIGS,
  generateState,
  buildAuthorizationUrl,
} from "@/lib/oauth";

const VALID_PROVIDERS = ["google", "github"];

export async function GET(
  _req: NextRequest,
  { params }: { params: Promise<{ provider: string }> }
) {
  const { provider } = await params;

  if (!VALID_PROVIDERS.includes(provider)) {
    return NextResponse.json(
      { error: `Unsupported provider. Must be one of: ${VALID_PROVIDERS.join(", ")}` },
      { status: 400 }
    );
  }

  const config = PROVIDER_CONFIGS[provider as Provider];
  const clientId = process.env[config.clientIdEnv];

  if (!clientId) {
    return NextResponse.json(
      {
        error: `${provider} OAuth is not configured. Missing ${config.clientIdEnv} environment variable.`,
      },
      { status: 503 }
    );
  }

  // Build the redirect URI — the callback URL for this provider
  const url = new URL(_req.url);
  const baseUrl = `${url.protocol}//${url.host}`;
  const redirectUri = `${baseUrl}/mobile/api/auth/${provider}/callback`;

  // Generate state for CSRF protection
  const state = await generateState(provider as Provider);

  // Store state in a cookie
  const cookieStore = await cookies();
  cookieStore.set("oauth_state", state, {
    httpOnly: true,
    secure: process.env.NODE_ENV === "production",
    sameSite: "lax",
    path: "/",
    maxAge: 60 * 10, // 10 minutes
  });

  // Build the authorization URL and redirect
  const authUrl = buildAuthorizationUrl(
    provider as Provider,
    state,
    redirectUri
  );

  return NextResponse.redirect(authUrl);
}