import assert from "node:assert";
import { assignFn, unify, UnifyError } from "../lib/generics/generics.js";
import { getDefaultTypeParser } from "../lib/parser/type_parser.js";
import { prettyT } from "../lib/util/pretty.js";

const mkType = getDefaultTypeParser();

// It would be better to compare the types directly with 'compareTypes', but the assert-module does not allow passing a custom comparison function.

assert.equal(
  // actual
  prettyT(
    unify(
      mkType("(a -> Int)"),
      mkType("[Bool] -> Int"),
    )
  ),
  // expected
  "([Bool] -> Int)",
);

assert.equal(
  // actual
  prettyT(
    unify(
      mkType("(a -> a) -> b"),
      mkType("(Bool -> Bool) -> a"),
    )
  ),
  // expected
  "((Bool -> Bool) -> a)",
);

assert.equal(
  // actual
  prettyT(
    assignFn(
      mkType("(a -> b) -> [a] -> [b]"),
      mkType("a -> a")
    )
  ),
  // expected
  "([a] -> [a])",
);

assert.equal(
  // actual
  prettyT(
    assignFn(
      mkType("(a -> Int) -> [a] -> a"),
      mkType("a -> a")
    )
  ),
  // expected
  "([Int] -> Int)",
);

assert.throws(
  () => {
    unify(
      mkType("Int"),
      mkType("Bool")
    )
  },
  // expected error
  UnifyError,
);

assert.throws(
  () => {
    unify(
      mkType("((a -> (a -> Ordering)) -> {a})"),
      mkType("([a] -> a)"),    
    )
  },
  UnifyError,
);