@thi.ng/rstream-query/qvar.js

@thi.ng/rstream based triple store & reactive query engine

import { isString } from "@thi.ng/checks/is-string";
const AUTO_QVAR_PREFIX = "?__q";
let AUTO_QVAR_ID = 0;
const isQVar = (x) => isString(x) && x.charAt(0) === "?";
const isAutoQVar = (x) => isString(x) && x.indexOf(AUTO_QVAR_PREFIX) == 0;
const autoQVar = () => AUTO_QVAR_PREFIX + (AUTO_QVAR_ID++).toString(36);
const qvarName = (x) => x.substring(1);
const qvarResolver = (vs, vp, vo, s, p, o) => {
  const type = vs << 2 | vp << 1 | vo;
  let ss = vs && qvarName(s);
  let pp = vp && qvarName(p);
  let oo = vo && qvarName(o);
  switch (type) {
    case 0:
    default:
      return;
    case 1:
      return (f) => ({ [oo]: f[2] });
    case 2:
      return (f) => ({ [pp]: f[1] });
    case 3:
      return (f) => ({ [pp]: f[1], [oo]: f[2] });
    case 4:
      return (f) => ({ [ss]: f[0] });
    case 5:
      return (f) => ({ [ss]: f[0], [oo]: f[2] });
    case 6:
      return (f) => ({ [ss]: f[0], [pp]: f[1] });
    case 7:
      return (f) => ({ [ss]: f[0], [pp]: f[1], [oo]: f[2] });
  }
};
export {
  autoQVar,
  isAutoQVar,
  isQVar,
  qvarName,
  qvarResolver
};