'use strict';

var utils = require('../../scoring/utils.js');
var Options = require('../../Options.js');

const calcAverageDegree = graph => {
  let average = 0;
  Object.keys(graph).forEach(key => {
    const neighbors = graph[key];
    average += neighbors.filter(entry => !!entry).length;
  });
  average /= Object.entries(graph).length;
  return average;
};
const estimatePossiblePatterns = ({
  token,
  graph,
  turns
}) => {
  const startingPosition = Object.keys(Options.default.graphs[graph]).length;
  const averageDegree = calcAverageDegree(Options.default.graphs[graph]);
  let guesses = 0;
  const tokenLength = token.length;
  // # estimate the number of possible patterns w/ tokenLength or less with turns or less.
  for (let i = 2; i <= tokenLength; i += 1) {
    const possibleTurns = Math.min(turns, i - 1);
    for (let j = 1; j <= possibleTurns; j += 1) {
      guesses += utils.nCk(i - 1, j - 1) * startingPosition * averageDegree ** j;
    }
  }
  return guesses;
};
var spatialMatcher = (({
  graph,
  token,
  shiftedCount,
  turns
}) => {
  let guesses = estimatePossiblePatterns({
    token,
    graph,
    turns
  });
  // add extra guesses for shifted keys. (% instead of 5, A instead of a.)
  // math is similar to extra guesses of l33t substitutions in dictionary matches.
  if (shiftedCount) {
    const unShiftedCount = token.length - shiftedCount;
    if (shiftedCount === 0 || unShiftedCount === 0) {
      guesses *= 2;
    } else {
      let shiftedVariations = 0;
      for (let i = 1; i <= Math.min(shiftedCount, unShiftedCount); i += 1) {
        shiftedVariations += utils.nCk(shiftedCount + unShiftedCount, i);
      }
      guesses *= shiftedVariations;
    }
  }
  return Math.round(guesses);
});

module.exports = spatialMatcher;
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