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

// a -> Int
const a_to_Int = makeGeneric(a => fnType({in: a, out: Int}));
// Bool -> Int
const Bool_to_Int = makeGeneric(() => fnType({in: lsType(Bool), out: 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({in: fnType({in: a, out: a}), out: b}));
// (Bool -> Bool) -> a
const fnType3 = makeGeneric(a => fnType({in: fnType({in: Bool, out: Bool}), out: a}));
console.log("should be: (Bool -> Bool) -> a");
console.log(pretty(unify(fnType2, fnType3)));

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

// (a -> Int) -> [a] -> a
const weirdFnType = makeGeneric(a =>
  fnType({
    in: fnType({in: a, out: Int}),
    out: fnType({in: lsType(a), out: a}),
  }));
console.log("should be: [Int] -> Int");
console.log(pretty(assign(weirdFnType, idFnType)));