Code Snippets

Anatomy of an Operation

Every capability in the system is this exact shape — a module with optional I/O schemas and a default handler that receives the worker as io:

// server/src/services/books/add.ts (structure)
import type { IO } from "~/agent"
import { z } from "@market/shared"

export const input = z.object({
  price: z.number(),
  catalogId: z.string(),
  meta: z.record(z.any()).optional(),
})

export const output = z.object({
  success: z.boolean(),
  id: z.string(),
})

export default async (io: IO, data: Input): Promise<Output> => {
  // io.identity  — who is calling (or null)
  // io.isSystem  — was this an internal, trusted call?
  // io.do(...)   — call another operation WITH permission checks
  // io.system()  — call another operation WITHOUT permission checks
  /* … handler … */
}

The worker guarantees data already passed input.parse, and whatever the handler returns must survive output.parse — the operation cannot receive a malformed request or leak an undeclared field.

The Rules Validator

The whole rules engine is two small functions over a parsed YAML object. Per-field checks compose from six primitives:

// server/src/rules/validate.ts (excerpt)
function validateMetaField(key, value, rule, prefix) {
  if (rule.required && (value === undefined || value === null || value === "")) {
    throw new InvalidError(`${prefix}Field "${key}" is required`)
  }

  if (value === undefined || value === null) return

  const str = String(value)

  if (rule.minLen !== undefined && str.length < rule.minLen) { /* … */ }
  if (rule.maxLen !== undefined && str.length > rule.maxLen) { /* … */ }
  if (rule.regex !== undefined && !new RegExp(rule.regex).test(str)) { /* … */ }
  if (rule.enum !== undefined && !rule.enum.includes(str)) { /* … */ }
  if (rule.contains !== undefined && !str.includes(rule.contains)) { /* … */ }
}

Every failure is an InvalidError with a message written for end users — the same string the Vue form displays.

The Client’s Single Call Site

All server communication funnels through one generic function. Note what it does not do: no URLs, no headers, no token handling — the agent owns those:

// client/src/application/query.ts
export async function command<R = any, D extends Record<string, any> = Record<string, any>>(
  to: string,
  data: D = {} as D
): Promise<R> {
  const reply = await agent.send<Msg<"command", D>, Msg<"reply", R & Record<string, any>>>({
    type: "command",
    to,
    data,
  })
  return reply.data as R
}

Channels: One Pub/Sub, Both Sides

A dependency-free topic map used by the agent for message events and by the client store for change subscriptions — the kind of small shared utility the isomorphic protocol package makes possible:

// shared/src/utils/channels.ts (shape)
const channels = createChannels<Message>()

// subscribe — returns an unsubscribe function
const off = channels.add("reply/command", (message) => {
  /* react to every command reply */
})

// publish
channels.send("reply/command", reply)

The agent wires it into send(), so any part of the client can observe traffic without touching the transport:

// shared/src/createAgent.ts (excerpt)
queueMicrotask(() => {
  this.events.send(message.type, message)
  this.events.send(`reply/${message.type}`, reply)
})

Fail-Fast Config

Server configuration is a zod schema too — CLI args override env vars, and a missing ENCRYPTION_KEY stops the process before it can serve a request:

// server/src/config.ts (excerpt)
export const zConfig = z.object({
  db: z.string().default("./sqlite.db"),
  port: z.coerce.number().default(3000),
  migrate: z.boolean().default(false),
  encryptionKey: z.string().min(1, "ENCRYPTION_KEY is required"),
})

// args take precedence, with env vars as a fallback
const config = zConfig.safeParse(merged)

if (!config.success) {
  console.error(config.error.issues.map(e => e.message).join("\n"))
  process.exit(1)
}