import { isString, optionalKey, struct } from 'is-kit';
import type {
  InferSchema,
  ParseResult,
  Predicate,
  StructOptions,
} from 'is-kit';

const userSchema = {
  id: isString,
  nickname: optionalKey(isString),
} as const;

type User = InferSchema<typeof userSchema>;

const options: StructOptions = { exact: true };
const isUser: Predicate<User> = struct(userSchema, options);

declare const result: ParseResult<User>;
if (result.valid) {
  result.value.id; // string
}

Primary types

• Predicate<T>, Guard<T> — The core unknown-input type guard contract. Guard is a readability alias for Predicate.
• Refinement<A, B>, Refine<A, B> — Narrows a known input type A to a subtype B. Refine is a readability alias for Refinement.
• ParseResult<T> — The tagged valid/value result returned by safeParse and related helpers.
• Primitive — The union of JavaScript primitive value types.
• InferSchema<S> — Infers the readonly object type represented by a struct schema.
• StructOptions — The public exact-key options accepted by struct and typedStruct.
• TypedStructShape<T>, TypedStructFields<T, S> — Public contracts for annotating wrappers and reusable helpers around typedStruct.

Advanced building blocks

• GuardedOf<F> — Extracts the guarded output type from one predicate.
• OutOfGuards<T>, GuardedWithin<Fs, A> — Extracts and constrains unions produced by collections of guards.
• RefineChain<In, T>, ChainResult<In, T> — Models the ordered refinements and final output used by refinement chains.
• OptionalSchemaField<G>, SchemaField, Schema — Building blocks for wrappers that accept or construct struct schemas.
• NoExtraKeys<S, Shape> — Rejects keys outside an expected type-level shape.
• OptionalObjectKeys<T>, RequiredObjectKeys<T> — Extracts optional or required keys from an object type.

SchemaShape is not exported from the package root. It remains an implementation detail unless a concrete external use case requires a public contract.