import { newRight } from "./sum.js";
import { newProduct } from "./product.js";
import { unit } from "../primitives/unit.js";
import { RBTreeWrapper } from "../util/rbtree_wrapper.js";
import { indent } from "../util/util.js";

// only for debugging
function inspectSet(_depth, options, inspect) {
  const keys = [];
  this.tree.forEach((key) => { keys.push(inspect(key, options)); });
  return `{\n${indent(keys.join(',\n'), 2)}\n}`;
}

// (a -> a -> Int) -> Set(a)
export const emptySet = compareFn => RBTreeWrapper.new((x, y) => compareFn(x)(y), inspectSet);

export const has = set => key => set.tree.get(key) === true;
export const add = set => key => set.tree.get(key) === true ? set : new RBTreeWrapper(set.tree.insert(key, true), inspectSet);
export const remove = set => key => new RBTreeWrapper(set.tree.remove(key), inspectSet);
export const length = set => set.tree.length;

export const fold = callback => initial => set => {
  let acc = initial;
  for (const iter=set.tree.begin; iter !== undefined && iter.valid; iter.next()) {
    acc = callback(acc)(iter.key);
  }
  return acc;
};

export const first = set => set.tree.begin;
export const last  = set => set.tree.end;

// test if iterator is 'done', and if not, get element and advance iterator.
export const read = iter => {
  if (iter !== undefined && iter.valid) {
    return newRight(
      newProduct
        (iter.key)
        (iter.clone().next())
    );
  }
  else {
    return newLeft(unit);
  }
};

export const forEach = set => fn => {
  set.tree.forEach(key => { fn(key); });
};