Derive config keys from DEFAULTS and enforce minimum memory of 512M

The config command previously maintained a separate key list and used a
switch statement that would need updating for each new key. Deriving
VALID_KEYS from config.DEFAULTS keeps them in sync automatically.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/commands/config.ts

@@ -1,8 +1,7 @@
 import { die } from "../fmt.ts"
 import * as config from "../config.ts"
 
-const VALID_KEYS = ["memory"] as const
-type Key = (typeof VALID_KEYS)[number]
+const VALID_KEYS = Object.keys(config.DEFAULTS) as config.Key[]
 
 export async function action(args: string[]) {
   if (args.length === 0) {
@@ -16,25 +15,18 @@ export async function action(args: string[]) {
   }
 
   const [key, ...rest] = args
-  if (!VALID_KEYS.includes(key as Key)) die(`Unknown config key: ${key}\nAvailable keys: ${VALID_KEYS.join(", ")}`)
+  if (!VALID_KEYS.includes(key as config.Key)) die(`Unknown config key: ${key}\nAvailable keys: ${VALID_KEYS.join(", ")}`)
 
   if (rest.length === 0) {
-    const val = await config.get(key as Key)
-    console.log(val ?? `${config.DEFAULTS[key as Key]} (default)`)
+    const val = await config.get(key as config.Key)
+    console.log(val ?? `${config.DEFAULTS[key as config.Key]} (default)`)
     return
   }
 
   if (rest.length > 1) die(`Too many arguments. Usage: sandlot config ${key} <value>`)
 
-  switch (key) {
-    case "memory": {
-      let normalized: string
-      try { normalized = config.validateMemory(rest[0]) } catch { die("Must be a number followed by G or M (e.g. 16G)") }
-      await config.set("memory", normalized!)
-      console.log(`memory = ${normalized!}`)
-      break
-    }
-    default:
-      die(`Unhandled config key: ${key}`)
-  }
+  let normalized: string
+  try { normalized = config.validateMemory(rest[0]) } catch { return die("Must be a number followed by G or M, minimum 512M (e.g. 16G)") }
+  await config.set("memory", normalized)
+  console.log(`memory = ${normalized}`)
 }

src/config.ts

@@ -1,19 +1,28 @@
 import { mkdir } from "fs/promises"
 import { homedir } from "os"
-import { dirname, join } from "path"
+import { join } from "path"
 
-const CONFIG_PATH = join(homedir(), ".config", "sandlot", "config.json")
+const CONFIG_DIR = join(homedir(), ".config", "sandlot")
+const CONFIG_PATH = join(CONFIG_DIR, "config.json")
 
 export const DEFAULTS = {
   memory: "16G",
 } as const
 
+export type Key = keyof typeof DEFAULTS
+
 export interface Config {
   memory?: string
 }
 
+const MIN_MEMORY_MB = 512
+
 export function validateMemory(v: string): string {
   if (!/^[1-9]\d*[GMgm]$/.test(v)) throw new Error(`Invalid memory value: ${v} (must be a number followed by G or M, e.g. 16G)`)
+  const num = parseInt(v)
+  const unit = v.slice(-1).toUpperCase()
+  const mb = unit === "G" ? num * 1024 : num
+  if (mb < MIN_MEMORY_MB) throw new Error(`Memory too low: ${v} (minimum ${MIN_MEMORY_MB}M)`)
   return v.toUpperCase()
 }
 
@@ -30,7 +39,7 @@ export async function load(): Promise<Config> {
 }
 
 export async function save(config: Config): Promise<void> {
-  await mkdir(dirname(CONFIG_PATH), { recursive: true })
+  await mkdir(CONFIG_DIR, { recursive: true })
   await Bun.write(CONFIG_PATH, JSON.stringify(config, null, 2) + "\n")
 }
 

src/vm.ts

@@ -67,9 +67,8 @@ function hostMounts(home: string): { dev: boolean; code: boolean } {
 /** Pull the image and start the container in detached mode. */
 async function createContainer(home: string): Promise<void> {
   const mounts = hostMounts(home)
-  const raw = (await getConfig("memory")) ?? DEFAULTS.memory
   let memory: string
-  try { memory = validateMemory(raw) } catch { memory = DEFAULTS.memory }
+  try { memory = validateMemory((await getConfig("memory")) ?? DEFAULTS.memory) } catch { memory = DEFAULTS.memory }
   const args = ["container", "run", "-d", "--name", CONTAINER_NAME, "-m", memory]
   if (mounts.dev) args.push("--mount", `type=bind,source=${home}/dev,target=/host/dev,readonly`)
   if (mounts.code) args.push("--mount", `type=bind,source=${home}/code,target=/host/code,readonly`)