sort.js

import ascending from "./ascending.js";
import permute from "./permute.js";

export default function sort(values, ...F) {
  if (typeof values[Symbol.iterator] !== "function") throw new TypeError("values is not iterable");
  values = Array.from(values);
  let [f] = F;
  if ((f && f.length !== 2) || F.length > 1) {
    const index = Uint32Array.from(values, (d, i) => i);
    if (F.length > 1) {
      F = F.map(f => values.map(f));
      index.sort((i, j) => {
        for (const f of F) {
          const c = ascendingDefined(f[i], f[j]);
          if (c) return c;
        }
      });
    } else {
      f = values.map(f);
      index.sort((i, j) => ascendingDefined(f[i], f[j]));
    }
    return permute(values, index);
  }
  return values.sort(compareDefined(f));
}

export function compareDefined(compare = ascending) {
  if (compare === ascending) return ascendingDefined;
  if (typeof compare !== "function") throw new TypeError("compare is not a function");
  return (a, b) => {
    const x = compare(a, b);
    if (x || x === 0) return x;
    return (compare(b, b) === 0) - (compare(a, a) === 0);
  };
}

export function ascendingDefined(a, b) {
  return (a == null || !(a >= a)) - (b == null || !(b >= b)) || (a < b ? -1 : a > b ? 1 : 0);
}