/**
 * Whether a state machine keeps its current state per behavior instance or shares one for the whole
 * run. Everything was `local` before scopes existed, so a missing field means `local` and old
 * projects load unchanged. Variables are shared by living on a Variables asset instead (#91).
 */
export type Scope = 'local' | 'global';

export interface Scoped {
  scope?: Scope;
}

export function scopeOf(owner: Scoped): Scope {
  return owner.scope === 'global' ? 'global' : 'local';
}

export function isGlobal(owner: Scoped): boolean {
  return owner.scope === 'global';
}

/** Reads a scope out of loaded data, where anything but the one known word means `local`. */
export function readScope(raw: unknown): Scope {
  return raw === 'global' ? 'global' : 'local';
}

/** Keeps `local` out of the document: the field is present only when it says `global`. */
export function setScope(owner: Scoped, scope: Scope): void {
  if (scope === 'global') owner.scope = 'global';
  else delete owner.scope;
}