export type PopulatedRelationship = { id: number }

const isRelationshipId = (value: unknown): value is number =>
  typeof value === 'number' && Number.isSafeInteger(value) && value > 0

export const isPopulatedRelationship = <Relationship extends PopulatedRelationship>(
  value: unknown,
): value is Relationship =>
  typeof value === 'object' && value !== null && 'id' in value && isRelationshipId(value.id)

export const relationshipId = (value: unknown): number | null => {
  if (isRelationshipId(value)) return value
  return isPopulatedRelationship(value) ? value.id : null
}

/** Display name from a populated `Contact` relation (or `fallback` when unpopulated). */
export const populatedContactName = (contact: unknown, fallback = 'Contato'): string => {
  if (typeof contact !== 'object' || contact === null || !('name' in contact)) return fallback
  const { name } = contact
  return typeof name === 'string' && name.length > 0 ? name : fallback
}

export const requireRelationshipId = (
  value: unknown,
  message = 'Relacionamento inválido.',
): number => {
  const id = relationshipId(value)
  if (id === null) throw new Error(message)
  return id
}

/** Normalizes a `hasMany` relationship field (ids or populated docs, any depth) into a deduped id list. */
export const uniqueRelationshipIds = (values: readonly unknown[] | null | undefined): number[] => [
  ...new Set((values ?? []).map(relationshipId).filter((id): id is number => id !== null)),
]