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

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

import { repeatedly } from "@thi.ng/transducers/repeatedly";
import { autoQVar, isQVar, qvarName } from "./qvar.js";
const patternVarCount = (p) => {
  let n = 0;
  if (isQVar(p[0])) n++;
  if (isQVar(p[1])) n++;
  if (isQVar(p[2])) n++;
  return n;
};
const patternVars = ([s, p, o]) => {
  const vars = [];
  isQVar(s) && vars.push(qvarName(s));
  isQVar(p) && vars.push(qvarName(p));
  isQVar(o) && vars.push(qvarName(o));
  return vars;
};
const resolvePathPattern = ([s, p, o], maxLen = p.length) => {
  const res = [];
  const avars = [...repeatedly(autoQVar, maxLen - 1)];
  for (let i = 0; i < maxLen; i++) {
    res.push([s, p[i % p.length], s = avars[i]]);
  }
  res[res.length - 1][2] = o;
  return [res, avars];
};
const sortPatterns = (patterns) => patterns.sort((a, b) => patternVarCount(a) - patternVarCount(b));
export {
  patternVarCount,
  patternVars,
  resolvePathPattern,
  sortPatterns
};