import type { Call1W, Fn1, Return } from "../HKT";
import type { ValueOf } from "../Obj/ValueOf";
import type { Eq, Lazied, Lazied$Get } from "../helpers";

export type HKT = Lazied$Get<HKTL>;
/**
 * {@link Lazied} version of {@link HKT}.
 */
export type HKTL = Lazied<Return<HKTRegistry[keyof HKTRegistry][0]>>;

/**
 * Registry of HKT builders and extractors.
 *
 * Only HKT with **1** type parameter is supported.
 *
 * GADT is _not_ supported, i.e., the type builder must accept any type as its type parameter
 * (should match `Fn1<unknown, unknown>`, not something like `Fn1<string, unknown>`).
 */
export interface HKTRegistry {}

/**
 * Helper type for registering {@link HKT} builders and extractors.
 */
export type RegisterHKT<
  Builder extends Fn1<unknown, unknown>,
  Extractor extends Fn1<Return<Builder>, unknown>,
> = [Builder, Extractor];

/**
 * Build an {@link HKT} from a type parameter.
 */
export type Kind<H extends HKT, A> =
  HKT$GetBuilder<H> & { readonly Args: (_: [A]) => void } extends (
    { readonly def: (...args: never[]) => infer R }
  ) ?
    R
  : never;

/**
 * Get the matching entry of {@link HKT} for `H`.
 * @private
 */
type _HKT$GetMatch<H extends HKT> = ValueOf<{
  [P in keyof HKTRegistry as H extends Return<HKTRegistry[P][0]> ? P : never]: HKTRegistry[P];
}>;

/**
 * Get the builder of `H` from {@link HKTRegistry}.
 */
export type HKT$GetBuilder<H extends HKT> =
  _HKT$GetMatch<H> extends [infer Builder extends Fn1<unknown, unknown>, unknown] ? Builder : never;
/**
 * The **unsafe** version of {@link HKT$GetBuilder} (i.e. no type checking with `H`).
 */
export type HKT$GetBuilderW<H> = H extends HKT ? HKT$GetBuilder<H> : never;

/**
 * Get the extractor of `H` from {@link HKTRegistry}.
 */
export type HKT$GetExtractor<H extends HKT> =
  _HKT$GetMatch<H> extends [unknown, infer Extractor extends Fn1] ? Extractor : never;
/**
 * The **unsafe** version of {@link HKT$GetExtractor} (i.e. no type checking with `H`).
 */
export type HKT$GetExtractorW<H> = H extends HKT ? HKT$GetExtractor<H> : never;

/**
 * Extract the type parameter of `H`.
 */
export type HKT$Extract<H extends HKT> = Call1W<HKT$GetExtractor<H>, H>;
/**
 * The **unsafe** version of {@link HKT$Extract} (i.e. no type checking with `H`).
 */
export type HKT$ExtractW<H> = H extends HKT ? HKT$Extract<H> : never;

/**
 * Mutate the type parameter of `H`.
 */
export type HKT$Mutate<H extends HKT, T> = Call1W<HKT$GetBuilder<H>, T>;
/**
 * The **unsafe** version of {@link HKT$Mutate} (i.e. no type checking with `H`).
 */
export type HKT$MutateW<H, T> = H extends HKT ? HKT$Mutate<H, T> : never;

/**
 * Get the construct of `H` from {@link HKTRegistry}.
 */
export type HKT$GetConstruct<H extends HKT> =
  Eq<H, HKT> extends true ? H
  : _HKT$GetMatch<H> extends [infer Builder extends Fn1<unknown, unknown>, unknown] ?
    Return<Builder>
  : never;
/**
 * The **unsafe** version of {@link HKT$GetConstruct} (i.e. no type checking with `H`).
 */
export type HKT$GetConstructW<H> = H extends HKT ? HKT$GetConstruct<H> : never;