import { Bool, Int } from "../primitives/types.js";
import { fnType, lsType } from "../structures/types.js";
import { assign, makeGeneric, unify } from "./generics.js";
import { pretty } from "../util.js";

// a -> Int
const a_to_Int = makeGeneric(a => fnType(a)(Int));
// Bool -> Int
const Bool_to_Int = makeGeneric(() => fnType(lsType(Bool))(Int));
console.log("should be: [Bool] -> Int")
console.log(pretty(unify(a_to_Int, Bool_to_Int)));

// (a -> a) -> b
const fnType2 = makeGeneric((a,b) => fnType(fnType(a)(a))(b));
// (Bool -> Bool) -> a
const fnType3 = makeGeneric(a => fnType(fnType(Bool)(Bool))(a));
console.log("should be: (Bool -> Bool) -> a");
console.log(pretty(unify(fnType2, fnType3)));

// (a -> b) -> [a] -> [b]
const mapFnType = makeGeneric((a,b) =>
  fnType
    (fnType(a)(b))
    (fnType(lsType(a))(lsType(b))))
// a -> a
const idFnType = makeGeneric(a =>
  fnType(a)(a));
console.log("should be: [a] -> [a]");
console.log(pretty(assign(mapFnType, idFnType)));

// (a -> Int) -> [a] -> a
const weirdFnType = makeGeneric(a =>
  fnType
    (fnType(a)(Int))
    (fnType
      (lsType(a))
      (a)))
// we call this function with parameter of type (b -> b) ...
// giving these substitutions:
//    a := b
//    b := Int
console.log("should be: [Int] -> Int");
console.log(pretty(assign(weirdFnType, idFnType)));