const nothing = require('./nothing.js');

const charset = '0123456789BFiuz';
const from_int = (n) => {
  let f = nothing.ZERO;
  for (let _ = 0; _ < n; _++) f = nothing.INC(f);
  return f;
};
const to_int = (f) => nothing.TIMES(f)(i => i+1)(0);
const from_bool = (b) => b ? nothing.TRUE : nothing.FALSE;
const to_bool = (f) => f(true)(false);
const to_array = (l) => {
  let a = [];

  while (!to_bool(nothing.IS_EMPTY(l))) {
    a.push(nothing.FIRST(l));
    l = nothing.REST(l);
  }

  return a;
};
const from_array = (a) => {
  let l = nothing.EMPTY;

  while (a.length) l = nothing.UNSHIFT(l)(a.pop());

  return l;
};
const to_char = (c) => charset[to_int(c)];
const from_char = (c) => from_int(charset.indexOf(c));
const to_string = (s) => to_array(s).map(to_char).join('');
const from_string = (s) => from_array(s.split('').map(from_char));
const representation_of = (v) => {
  if (typeof v == "number") return from_int(v);
  if (typeof v == "boolean") return from_bool(v);
  if (typeof v == "string") return from_string(v);
  if (Array.isArray(v)) return from_array(v.map(representation_of));
  throw Error(`Oops, I don’t know how represent this: ${v}`);
};
const zip = (a, b) => a.map((e, i) => [e, b[i]]);
const check_represent = function(r, v) {
  if (typeof v == "number") return to_int(r) == v;
  if (typeof v == "boolean") return to_bool(r) == v;
  if (typeof v == "string") return to_string(r) == v;
  if (Array.isArray(v)) {
    let a = to_array(r);
    return a.length == v.length && zip(a, v).every(([r, v]) => check_represent(r,v));
  }
  throw Error(`Oops, I don’t know how check this: ${v}`);
};
module.exports = {
  representation_of, check_represent
};