import { fnType } from "../metacircular.js";
import { Function, Type } from "../metacircular.js";
import { DefaultMap } from "../util.js";

const productTypeRegistry = new DefaultMap(leftType => new DefaultMap(rightType => ({ operator: "product", leftType, rightType })));

// type constructor
export const prodType = (leftType, rightType) => productTypeRegistry.getdefault(leftType, true).getdefault(rightType, true);

// In JS, all products are encoded in the same way:
const constructor = left => right => ({left, right});
const getLeft     = product => product.left;
const getRight    = product => product.right;

// Given two types A and B, create the type (A × B).
export const makeProductType = (leftType, rightType) => {
  const pType = prodType(leftType, rightType);

  const leftFnType  = fnType({in: pType, out: leftType});
  const rightFnType = fnType({in: pType, out: rightType});

  const constructorBoundType = fnType({in: rightType, out: pType});
  const constructorType      = fnType({in: leftType , out: constructorBoundType});

  return {l:[
    {i: pType, t: Type},

    {i: getLeft    , t: leftFnType},
    {i: getRight   , t: rightFnType},
    {i: leftFnType , t: Function},
    {i: rightFnType, t: Function},

    {i: constructor         , t: constructorType},
    {i: constructorType     , t: Function},
    {i: constructorBoundType, t: Function},
  ]};
};