Type-safe messages with Vercel AI SDK and Drizzle

message-schema.ts

import { pgTable, json, text, timestamp } from "drizzle-orm/pg-core";
import type { Message, Attachment } from "ai";

export const message = pgTable("message", {
  id: text("id").primaryKey(),
  chatId: text("chatId")
    .notNull()
    .references(() => chat.id),
  
  // infers: "data" | "user" | "system" | "assistant"
  role: text("role", { enum: ["data", "user", "system", "assistant"]}).notNull(),
  
  // infers: (TextUIPart | ReasoningUIPart | .... )[] | undefined
  parts: json("parts").notNull().$type<Message["parts"]>(),
  
  content: text("content").notNull(),
  attachments: json("attachments").notNull().$type<Attachment[]>(),
  createdAt: timestamp("createdAt").defaultNow().notNull(),
});

// ...