Initial commit: EGBE chatbot template

Stripped from vercel/chatbot (Apache 2.0):
- Dropped @vercel/* packages and AI Gateway
- Removed artifacts feature (code/text/sheet/image side panel)
- Switched AI provider to @ai-sdk/openai-compatible -> EGBE LiteLLM
- Replaced Vercel Blob upload with data URLs
- Dropped Redis resumable streams and rate limiter (in-memory now)
- Added Dockerfile (Next.js standalone) + entrypoint that runs migrations
- Wired DATABASE_URL, EGBE_AI_API_URL/KEY, NEXT_PUBLIC_BASE_URL for app-deploy.sh

lib/errors.ts

@@ -0,0 +1,119 @@
+export type ErrorType =
+  | "bad_request"
+  | "unauthorized"
+  | "forbidden"
+  | "not_found"
+  | "rate_limit"
+  | "offline";
+
+export type Surface =
+  | "chat"
+  | "auth"
+  | "api"
+  | "stream"
+  | "database"
+  | "history"
+  | "vote";
+
+export type ErrorCode = `${ErrorType}:${Surface}`;
+
+export type ErrorVisibility = "response" | "log" | "none";
+
+export const visibilityBySurface: Record<Surface, ErrorVisibility> = {
+  database: "log",
+  chat: "response",
+  auth: "response",
+  stream: "response",
+  api: "response",
+  history: "response",
+  vote: "response",
+};
+
+export class ChatbotError extends Error {
+  type: ErrorType;
+  surface: Surface;
+  statusCode: number;
+
+  constructor(errorCode: ErrorCode, cause?: string) {
+    super();
+
+    const [type, surface] = errorCode.split(":");
+
+    this.type = type as ErrorType;
+    this.cause = cause;
+    this.surface = surface as Surface;
+    this.message = getMessageByErrorCode(errorCode);
+    this.statusCode = getStatusCodeByType(this.type);
+  }
+
+  toResponse() {
+    const code: ErrorCode = `${this.type}:${this.surface}`;
+    const visibility = visibilityBySurface[this.surface];
+
+    const { message, cause, statusCode } = this;
+
+    if (visibility === "log") {
+      console.error({
+        code,
+        message,
+        cause,
+      });
+
+      return Response.json(
+        { code: "", message: "Something went wrong. Please try again later." },
+        { status: statusCode }
+      );
+    }
+
+    return Response.json({ code, message, cause }, { status: statusCode });
+  }
+}
+
+export function getMessageByErrorCode(errorCode: ErrorCode): string {
+  if (errorCode.includes("database")) {
+    return "An error occurred while executing a database query.";
+  }
+
+  switch (errorCode) {
+    case "bad_request:api":
+      return "The request couldn't be processed. Please check your input and try again.";
+
+    case "unauthorized:auth":
+      return "You need to sign in before continuing.";
+    case "forbidden:auth":
+      return "Your account does not have access to this feature.";
+
+    case "rate_limit:chat":
+      return "You've reached the message limit. Come back in 1 hour to continue chatting.";
+    case "not_found:chat":
+      return "The requested chat was not found. Please check the chat ID and try again.";
+    case "forbidden:chat":
+      return "This chat belongs to another user. Please check the chat ID and try again.";
+    case "unauthorized:chat":
+      return "You need to sign in to view this chat. Please sign in and try again.";
+    case "offline:chat":
+      return "We're having trouble sending your message. Please check your internet connection and try again.";
+
+    default:
+      return "Something went wrong. Please try again later.";
+  }
+}
+
+function getStatusCodeByType(type: ErrorType) {
+  switch (type) {
+    case "bad_request":
+      return 400;
+    case "unauthorized":
+      return 401;
+    case "forbidden":
+      return 403;
+    case "not_found":
+      return 404;
+    case "rate_limit":
+      return 429;
+    case "offline":
+      return 503;
+    default:
+      return 500;
+  }
+}