/**
 * A Standard Schema-compatible validator: a minimal duck-type covering Zod v3/v4, valibot, and
 * arktype schemas. Only the `~standard.validate` method is required at runtime.
 */
export type StandardSchemaValidator<TOutput = unknown> = {
  readonly '~standard': {
    validate(value: unknown): StandardSchemaResult<TOutput> | Promise<StandardSchemaResult<TOutput>>
  }
}

/**
 * The two possible outcomes of a Standard Schema `validate` call. A successful result carries
 * `value`; a failed result carries `issues`.
 */
export type StandardSchemaResult<TOutput> = { readonly value: TOutput; readonly issues?: undefined } | { readonly issues: ReadonlyArray<StandardSchemaIssue> }

/**
 * One validation issue from a Standard Schema `validate` call.
 */
export type StandardSchemaIssue = {
  readonly message?: string
  readonly path?: ReadonlyArray<PropertyKey | { readonly key: PropertyKey }>
}

/**
 * Thrown by `validateStandardSchema` when validation fails. Carries the raw `issues` array from
 * the schema's `validate` result so callers receive a uniform error shape regardless of which
 * schema library is in use.
 */
export class ParseError extends Error {
  readonly issues: ReadonlyArray<StandardSchemaIssue>

  constructor({ issues, message }: { issues: ReadonlyArray<StandardSchemaIssue>; message?: string }) {
    super(message ?? 'Validation failed')
    this.name = 'ParseError'
    this.issues = issues
  }
}

/**
 * Validates `value` against a Standard Schema-compatible `schema`. Returns the parsed output on
 * success; throws `ParseError` with the schema's `issues` on failure. Handles both sync and async
 * `validate` implementations transparently.
 *
 * @example
 * const pet = await validateStandardSchema(PetSchema, rawData)
 */
export async function validateStandardSchema<TOutput>(schema: StandardSchemaValidator<TOutput>, value: unknown): Promise<TOutput> {
  const result = await schema['~standard'].validate(value)
  if (result.issues) {
    throw new ParseError({ issues: result.issues })
  }
  return (result as { value: TOutput }).value
}