feat(app): improve desktop multi-server support (#30678)

Co-authored-by: Brendan Allan <git@brendonovich.dev>

packages/app/src/utils/server-scope.ts

@@ -0,0 +1,70 @@
+import type { ServerConnection } from "@/context/server"
+
+export type ServerScope = string & { readonly __brand: "ServerScope" }
+export type SessionRouteKey = string & { readonly __brand: "SessionRouteKey" }
+export type SessionStateKey = string & { readonly __brand: "SessionStateKey" }
+export type ScopedKey = string & { readonly __brand: "ScopedKey" }
+
+const separator = "\u0000"
+
+function fragment(label: string, value: string) {
+  if (value.includes(separator)) throw new Error(`${label} cannot contain null bytes`)
+  return value
+}
+
+function compose(scope: ServerScope, parts: string[]) {
+  return [fragment("Server scope", scope), ...parts.map((part) => fragment("Scoped key part", part))].join(separator)
+}
+
+export const ServerScope = {
+  local: "local" as ServerScope,
+  fromServerKey(key: ServerConnection.Key, canonicalLocalServer?: ServerConnection.Key) {
+    return fragment("Server scope", key === "sidecar" || key === canonicalLocalServer ? ServerScope.local : key) as ServerScope
+  },
+}
+
+export const SessionRouteKey = {
+  fromRoute(dir: string | undefined, sessionID?: string) {
+    return fragment("Session route", `${dir ?? ""}${sessionID ? "/" + sessionID : ""}`) as SessionRouteKey
+  },
+  fromLegacy(key: string) {
+    return fragment("Legacy session route", key) as SessionRouteKey
+  },
+}
+
+export const SessionStateKey = {
+  from(scope: ServerScope, route: SessionRouteKey) {
+    return compose(scope, [route]) as SessionStateKey
+  },
+  route(key: string) {
+    const split = key.lastIndexOf(separator)
+    return SessionRouteKey.fromLegacy(split === -1 ? key : key.slice(split + 1))
+  },
+  scope(key: string) {
+    const split = key.indexOf(separator)
+    if (split === -1) return ServerScope.local
+    return fragment("Stored server scope", key.slice(0, split)) as ServerScope
+  },
+}
+
+export const ScopedKey = {
+  from(scope: ServerScope, ...parts: string[]) {
+    return compose(scope, parts) as ScopedKey
+  },
+  prefix(scope: ServerScope, ...parts: string[]) {
+    return `${ScopedKey.from(scope, ...parts)}${separator}`
+  },
+}
+
+export function migrateLegacySessionStateKeys(value: unknown) {
+  if (!value || typeof value !== "object" || Array.isArray(value)) return value
+  const entries = Object.entries(value)
+  if (entries.every(([key]) => key.includes(separator))) return value
+  const scoped = Object.fromEntries(entries.filter(([key]) => key.includes(separator)))
+  for (const [key, item] of entries) {
+    if (key.includes(separator)) continue
+    const next = SessionStateKey.from(ServerScope.local, SessionRouteKey.fromLegacy(key))
+    if (!(next in scoped)) scoped[next] = item
+  }
+  return scoped
+}