import { makeGeneric } from "../generics/generics.js";
import { Type } from "../metacircular.js";
import { DefaultMap } from "../util.js";
import { typedFnType } from "./function.js";

const symbolProduct = Symbol("Product");
const productTypeRegistry = new DefaultMap(leftType => new DefaultMap(rightType => ({
    symbol: symbolProduct,
    params: [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;

export const ModuleProduct = {l: [
  // binary type constructor
  // Type -> Type -> Type
  ...typedFnType(prodType, fnType => fnType
    (Type)
    (fnType
      (Type)
      (Type)
    )
  ),

  // a -> b -> (a, b)
  ...typedFnType(constructor, fnType => makeGeneric((a, b) => fnType
    (a)
    (fnType
      (b)
      (prodType(a)(b))
    )
  )),

  // (a, b) -> a
  ...typedFnType(getLeft, fnType => makeGeneric((a, b) => fnType
    (prodType(a)(b))
    (a)
  )),

  // (a, b) -> b
  ...typedFnType(getRight, fnType => makeGeneric((a, b) => fnType
    (prodType(a)(b))
    (b)
  )),
]};