import type { WorkspaceSessionState } from '../../shared/workspace-session-state-types'

/**
 * Keeps runtime-authored session state alive across a renderer's full write.
 *
 * A session write replaces the stored object, and the renderer builds its payload from Zustand --
 * which has no idea the runtime authority sharing this profile also persists the client-hosted
 * pages it owns. Without this, every ordinary desktop session write erases them, and the loss only
 * shows up a restart later when there is nothing left to rehydrate.
 *
 * Callers do not opt in: the Store applies this inside setLocalWorkspaceSession and
 * setHostWorkspaceSession, so the before-unload stage path inherits it too. Guarding the individual
 * writers instead is what let the quit write -- the most common one there is -- erase the field.
 *
 * A runtime clearing its own rows writes an empty map, not `undefined`, so this can never pin a
 * stale set: only an author that never mentioned the field inherits the previous one.
 */
export function preserveRuntimeAuthoredWorkspaceSessionFields(
  next: WorkspaceSessionState,
  prior: WorkspaceSessionState | null | undefined
): WorkspaceSessionState {
  if (
    next.clientHostedBrowserPagesByWorktree !== undefined ||
    prior?.clientHostedBrowserPagesByWorktree === undefined
  ) {
    return next
  }
  return {
    ...next,
    clientHostedBrowserPagesByWorktree: prior.clientHostedBrowserPagesByWorktree
  }
}