import { If } from "../../Core/TypeConditionals";
import { Complete, CopyNull, NotUndefined } from "../../Core/TypeModifiers";
import ModelTraits, { IsValidSimpleTraitType } from "../../Traits/ModelTraits";

type SingleTrait<TTrait> = If<
  IsValidSimpleTraitType<NonNullable<TTrait>>,
  TTrait,
  TTrait extends ModelTraits ? FlattenedFromTraits<TTrait> : never
>;

type ArrayTrait<_TTrait, TElement> = ReadonlyArray<SingleTrait<TElement>>;

/**
 * Transforms a {@link ModelTraits} class into a type usable as a flattened view of multiple strata.
 * All properties of the new type:
 *
 *   * Are read-only.
 *   * May be undefined even if the traits class property has a default or is otherwise not allowed to be undefined.
 *
 * Nested traits classes follow the rules above.
 */
type FlattenedFromTraits<TDefinition extends ModelTraits> = Complete<{
  readonly [P in keyof TDefinition]: NotUndefined<TDefinition[P]> extends Array<
    infer TElement
  >
    ? ArrayTrait<TDefinition[P], TElement> extends infer R
      ? CopyNull<TDefinition[P], R> | undefined
      : never
    : SingleTrait<TDefinition[P]> extends infer R
      ? CopyNull<TDefinition[P], R> | undefined
      : never;
}>;

export default FlattenedFromTraits;