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

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

export const emptyDict = compareFn => RBTreeWrapper.new((x, y) => compareFn(x)(y), inspectDict);

export const has = dict => key => dict.tree.get(key) !== undefined;
export const get = dict => key => dict.tree.get(key);
export const set = dict => key => value => new RBTreeWrapper(dict.tree.remove(key).insert(key, value), inspectDict);
export const remove = dict => key => new RBTreeWrapper(dict.tree.remove(key), inspectDict);
export const length = dict => dict.tree.length;

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

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

export const read = iter => {
  if (iter !== undefined && iter.valid) {
    return newRight(
      newProduct(
        newProduct(iter.key)(iter.value)
        (iter.clone().next())
      )
    );
  }
  else {
    return newLeft(unit);
  }
};