/**
 * Copyright 2013-2017  Zaid Abdulla
 *
 * This file is part of GenieACS.
 *
 * GenieACS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * GenieACS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with GenieACS.  If not, see <http://www.gnu.org/licenses/>.
 */
"use strict";

const WILDCARD_MULTIPLIER = 2;
const UNDISCOVERED_DEPTH = 7;

// Simple heuristic to estimate GPN count given a set of patterns to be
// discovered. Used to decide whether to use nextLevel = false in GPN.
// gpnPatterns is [pattern, flags]
// pattern is a path (array)
// flags is an int where its bits mark the segments in the pattern that
// need refreshing. Leading 0s indicate that the pattern up to that
// point has been discovered.
function estimateGpnCount(gpnPatterns, depth = 0) {
  const children = {};
  const wildcardChildren = [];
  let wildcardDiscovered = false;
  let gpnCount = 0;

  for (let pattern of gpnPatterns) {
    const path = pattern[0];
    const flags = pattern[1] >> depth;

    let k = path[depth];

    if (!k) {
      if (flags & 1)
        gpnCount = 1;
      continue;
    }

    if (flags & 1) {
      gpnCount = 1;

      if (depth > UNDISCOVERED_DEPTH)
        continue;
    }
    else if (k === "*")
      wildcardDiscovered = true;

    if (k === "*") {
      wildcardChildren.push(pattern);
    }
    else {
      children[k] = children[k] || [];
      children[k].push(pattern);
    }
  }

  let wildcardGpnCount = 0;
  if (!wildcardDiscovered && wildcardChildren.length)
      wildcardGpnCount += estimateGpnCount(wildcardChildren, depth + 1) * WILDCARD_MULTIPLIER;

  for (let k of Object.keys(children)) {
    let c = estimateGpnCount(children[k].concat(wildcardChildren), depth + 1);
    wildcardGpnCount -= c;
    gpnCount += c;
  }

  gpnCount += Math.max(0, wildcardGpnCount);

  return gpnCount;
}

exports.estimateGpnCount = estimateGpnCount;