// Total ordering of primitive types

import { getSymbol } from "../type_constructor.js";

export const compareNumbers = x => y => {
  if (typeof(x) !== 'number' || typeof(y) !== 'number') {
    throw new Error(`was only meant to compare numbers! got ${x} and ${y}`);
  }
  return (x < y) ? -1 : (x > y) ? 1 : 0;
}

export const compareStrings = x => y => {
  if (typeof(x) !== 'string' || typeof(y) !== 'string') {
    throw new Error(`was only meant to compare strings! got ${x} and ${y}`);
  }
  return (x < y) ? -1 : (x > y) ? 1 : 0;
}

export const compareBools = x => y => {
  if (typeof(x) !== 'boolean' || typeof(y) !== 'boolean') {
    throw new Error(`was only meant to compare booleans! got ${x} and ${y}`);
  }
  return x - y;
};

// The Unit-type has only one instance, which is equal to itself:
export const compareUnits = x => y => 0;

export const compareTypes = x => y => {
  return compareSymbols(getSymbol(x))(getSymbol(y))
    || compareNumbers(x.params.length)(y.params.length)
    || x.params.reduce((acc, _, i) => acc || compareTypes(x.params[i])(y.params[i]), 0)
}

// Note: dirty assumption that every symbol has unique description.
// This will be fixed once we move from symbols to real UUIDs.
export const compareSymbols = a => b => (a !== b) && compareStrings(a.description)(b.description);