Add initial library

src/callback.ts

@@ -0,0 +1,87 @@
+import { NextResponse, type NextRequest } from "next/server";
+
+import { AUTH_VALIDATE_URL, DEFAULT_COOKIE_NAMES } from "./constants";
+import type { SfAuthCookieNames } from "./middleware";
+
+export type SfAuthCallbackOptions = {
+  redirectTo: string;
+  cookieNames?: SfAuthCookieNames;
+  validateEndpoint?: string;
+};
+
+type ValidateResponse = {
+  valid: boolean;
+  user_id: string;
+};
+
+const resolveCookieNames = (cookieNames?: SfAuthCookieNames) => ({
+  userId: cookieNames?.userId ?? DEFAULT_COOKIE_NAMES.userId,
+  username: cookieNames?.username ?? DEFAULT_COOKIE_NAMES.username
+});
+
+const errorResponse = (message: string, status = 400) =>
+  new NextResponse(message, {
+    status,
+    headers: {
+      "content-type": "text/plain; charset=utf-8"
+    }
+  });
+
+export const createSfAuthCallbackRoute = (
+  options: SfAuthCallbackOptions
+) => {
+  const cookieNames = resolveCookieNames(options.cookieNames);
+  const validateUrl = options.validateEndpoint ?? AUTH_VALIDATE_URL;
+
+  return async (request: NextRequest) => {
+    const url = new URL(request.url);
+    const userId = url.searchParams.get("user_id");
+    const username = url.searchParams.get("username");
+    const key = url.searchParams.get("key");
+
+    if (!userId || !username || !key) {
+      return errorResponse("Missing required query parameters.");
+    }
+
+    let validateResponse: ValidateResponse;
+
+    try {
+      const response = await fetch(validateUrl, {
+        method: "POST",
+        headers: {
+          "content-type": "application/json"
+        },
+        body: JSON.stringify({ user_id: userId, key })
+      });
+
+      if (!response.ok) {
+        return errorResponse("Failed to validate credentials.");
+      }
+
+      validateResponse = (await response.json()) as ValidateResponse;
+    } catch (error) {
+      return errorResponse("Unable to validate credentials.", 500);
+    }
+
+    if (!validateResponse.valid || validateResponse.user_id !== userId) {
+      return errorResponse("Invalid credentials.");
+    }
+
+    const redirectTarget = new URL(options.redirectTo, request.url);
+    const response = NextResponse.redirect(redirectTarget);
+
+    response.cookies.set(cookieNames.userId, userId, {
+      httpOnly: true,
+      sameSite: "lax",
+      path: "/"
+    });
+
+    response.cookies.set(cookieNames.username, username, {
+      httpOnly: true,
+      sameSite: "lax",
+      path: "/"
+    });
+
+    return response;
+  };
+};