/* IMPORT */

import {SYMBOL_OBSERVABLE_FROZEN, SYMBOL_OBSERVABLE_READABLE, SYMBOL_TEMPLATE_ACCESSOR, SYMBOL_UNTRACKED, SYMBOL_UNTRACKED_UNWRAPPED} from '~/constants';
import type {ComponentFunction, Falsy, TemplateActionProxy, Truthy} from '~/types';

/* MAIN */

const {assign} = Object;

const castArray = <T> ( value: T[] | T ): T[] => {

  return isArray ( value ) ? value : [value];

};

const castError = ( exception: unknown ): Error => {

  if ( isError ( exception ) ) return exception;

  if ( isString ( exception ) ) return new Error ( exception );

  return new Error ( 'Unknown error' );

};

const flatten = <T> ( arr: T[] ) => {

  for ( let i = 0, l = arr.length; i < l; i++ ) {

    if ( !isArray ( arr[i] ) ) continue;

    return arr.flat ( Infinity );

  }

  return arr;

};

const indexOf = (() => {

  const _indexOf = Array.prototype.indexOf;

  return <T> ( arr: ArrayLike<unknown>, value: T ): number => {

    return _indexOf.call ( arr, value );

  };

})();

const {isArray} = Array;

const isBoolean = ( value: unknown ): value is boolean => {

  return typeof value === 'boolean';

};

const isComponent = ( value: unknown ): value is ComponentFunction => {

  return isFunction ( value ) && ( SYMBOL_UNTRACKED_UNWRAPPED in value );

};

const isError = ( value: unknown ): value is Error => {

  return value instanceof Error;

};

const isFalsy = <T> ( value: T ): value is Falsy<T> => {

  return !value;

};

const isFunction = ( value: unknown ): value is (( ...args: any[] ) => any) => {

  return typeof value === 'function';

};

const isFunctionReactive = ( value: Function ): boolean => {

  return !( SYMBOL_UNTRACKED in value || SYMBOL_UNTRACKED_UNWRAPPED in value || SYMBOL_OBSERVABLE_FROZEN in value || value[SYMBOL_OBSERVABLE_READABLE]?.parent?.disposed );

};

const isNil = ( value: unknown ): value is null | undefined => {

  return value === null || value === undefined;

};

const isNode = ( value: unknown ): value is Node => {

  return value instanceof Node;

};

const isObject = ( value: unknown ): value is object => {

  return typeof value === 'object' && value !== null;

};

const isPromise = ( value: unknown ): value is Promise<unknown> => {

  return value instanceof Promise;

};

const isString = ( value: unknown ): value is string => {

  return typeof value === 'string';

};

const isSVG = ( value: Element ): value is SVGElement => {

  return !!value['isSVG'];

};

const isSVGElement = (() => {

  const svgRe = /^(t(ext$|s)|s[vwy]|g)|^set|tad|ker|p(at|s)|s(to|c$|ca|k)|r(ec|cl)|ew|us|f($|e|s)|cu|n[ei]|l[ty]|[GOP]/; //URL: https://regex101.com/r/Ck4kFp/1
  const svgCache = {};

  return ( element: string ): boolean => {

    const cached = svgCache[element];

    return ( cached !== undefined ) ? cached : ( svgCache[element] = !element.includes ( '-' ) && svgRe.test ( element ) );

  };

})();

const isTemplateAccessor = ( value: unknown ): value is TemplateActionProxy => {

  return isFunction ( value ) && ( SYMBOL_TEMPLATE_ACCESSOR in value );

};

const isTruthy = <T> ( value: T ): value is Truthy<T> => {

  return !!value;

};

const isVoidChild = ( value: unknown ): value is null | undefined | symbol | boolean => {

  return value === null || value === undefined || typeof value === 'boolean' || typeof value === 'symbol';

};

const noop = (): void => {

  return;

};

const once = <T> ( fn: () => T ): (() => T) => {

  let called = false;
  let result: T;

  return (): T => {

    if ( !called ) {

      called = true;
      result = fn ();

    }

    return result;

  };

};

/* EXPORT */

export {assign, castArray, castError, flatten, indexOf, isArray, isBoolean, isComponent, isError, isFalsy, isFunction, isFunctionReactive, isNil, isNode, isObject, isPromise, isString, isSVG, isSVGElement, isTemplateAccessor, isTruthy, isVoidChild, noop, once};