import utils from './utils.mjs';
import estimateGuesses from './estimate.mjs';
import { MIN_GUESSES_BEFORE_GROWING_SEQUENCE } from '../data/const.mjs';

class Scoring {
  constructor(options) {
    this.options = options;
    this.password = '';
    this.optimal = {};
    this.excludeAdditive = false;
  }
  fillArray(size, valueType) {
    const result = [];
    for (let i = 0; i < size; i += 1) {
      let value = [];
      if (valueType === 'object') {
        value = {};
      }
      result.push(value);
    }
    return result;
  }
  // helper: make bruteforce match objects spanning i to j, inclusive.
  makeBruteforceMatch(i, j) {
    return {
      pattern: 'bruteforce',
      token: this.password.slice(i, j + 1 || 9e9),
      i,
      j
    };
  }
  // helper: considers whether a length-sequenceLength
  // sequence ending at match bestMatches is better (fewer guesses)
  // than previously encountered sequences, updating state if so.
  // eslint-disable-next-line max-statements
  update(match, sequenceLength) {
    const k = match.j;
    const estimatedMatch = estimateGuesses(this.options, match, this.password);
    let pi = estimatedMatch.guesses;
    if (sequenceLength > 1) {
      // we're considering a length-sequenceLength sequence ending with match bestMatches:
      // obtain the product term in the minimization function by multiplying bestMatches's guesses
      // by the product of the length-(sequenceLength-1)
      // sequence ending just before bestMatches, at bestMatches.i - 1.
      pi *= this.optimal.guessesProduct[estimatedMatch.i - 1][sequenceLength - 1];
    }
    // calculate the minimization func
    let g = utils.factorial(sequenceLength) * pi;
    if (!this.excludeAdditive) {
      g += MIN_GUESSES_BEFORE_GROWING_SEQUENCE ** (sequenceLength - 1);
    }
    // update state if new best.
    // first see if any competing sequences covering this prefix,
    // with sequenceLength or fewer matches,
    // fare better than this sequence. if so, skip it and return.
    let shouldSkip = false;
    const competingG = this.optimal.totalGuesses[k];
    Object.keys(competingG).forEach(competingPatternLengthStr => {
      const competingPatternLength = parseInt(competingPatternLengthStr, 10);
      const competingMetricMatch = competingG[competingPatternLength];
      if (competingPatternLength <= sequenceLength) {
        if (competingMetricMatch <= g) {
          shouldSkip = true;
        }
      }
    });
    if (!shouldSkip) {
      // this sequence might be part of the final optimal sequence.
      this.optimal.totalGuesses[k][sequenceLength] = g;
      this.optimal.bestMatches[k][sequenceLength] = estimatedMatch;
      this.optimal.guessesProduct[k][sequenceLength] = pi;
    }
  }
  // helper: evaluate bruteforce matches ending at passwordCharIndex.
  bruteforceUpdate(passwordCharIndex) {
    // see if a single bruteforce match spanning the passwordCharIndex-prefix is optimal.
    let match = this.makeBruteforceMatch(0, passwordCharIndex);
    this.update(match, 1);
    for (let i = 1; i <= passwordCharIndex; i += 1) {
      // generate passwordCharIndex bruteforce matches, spanning from (i=1, j=passwordCharIndex) up to (i=passwordCharIndex, j=passwordCharIndex).
      // see if adding these new matches to any of the sequences in optimal[i-1]
      // leads to new bests.
      match = this.makeBruteforceMatch(i, passwordCharIndex);
      const tmp = this.optimal.bestMatches[i - 1];
      Object.keys(tmp).forEach(sequenceLengthStr => {
        const sequenceLength = parseInt(sequenceLengthStr, 10);
        const lastMatch = tmp[sequenceLength];
        // corner: an optimal sequence will never have two adjacent bruteforce matches.
        // it is strictly better to have a single bruteforce match spanning the same region:
        // same contribution to the guess product with a lower length.
        // --> safe to skip those cases.
        if (lastMatch.pattern !== 'bruteforce') {
          // try adding bestMatches to this length-sequenceLength sequence.
          this.update(match, sequenceLength + 1);
        }
      });
    }
  }
  // helper: step backwards through optimal.bestMatches starting at the end,
  // constructing the final optimal match sequence.
  unwind(passwordLength) {
    const optimalMatchSequence = [];
    let k = passwordLength - 1;
    // find the final best sequence length and score
    let sequenceLength = 0;
    // eslint-disable-next-line no-loss-of-precision
    let g = 2e308;
    const temp = this.optimal.totalGuesses[k];
    // safety check for empty passwords
    if (temp) {
      Object.keys(temp).forEach(candidateSequenceLengthStr => {
        const candidateSequenceLength = parseInt(candidateSequenceLengthStr, 10);
        const candidateMetricMatch = temp[candidateSequenceLength];
        if (candidateMetricMatch < g) {
          sequenceLength = candidateSequenceLength;
          g = candidateMetricMatch;
        }
      });
    }
    while (k >= 0) {
      const match = this.optimal.bestMatches[k][sequenceLength];
      optimalMatchSequence.unshift(match);
      k = match.i - 1;
      sequenceLength -= 1;
    }
    return optimalMatchSequence;
  }
  // ------------------------------------------------------------------------------
  // search --- most guessable match sequence -------------------------------------
  // ------------------------------------------------------------------------------
  //
  // takes a sequence of overlapping matches, returns the non-overlapping sequence with
  // minimum guesses. the following is a O(l_max * (n + m)) dynamic programming algorithm
  // for a length-n password with m candidate matches. l_max is the maximum optimal
  // sequence length spanning each prefix of the password. In practice it rarely exceeds 5 and the
  // search terminates rapidly.
  //
  // the optimal "minimum guesses" sequence is here defined to be the sequence that
  // minimizes the following function:
  //
  //    totalGuesses = sequenceLength! * Product(m.guesses for m in sequence) + D^(sequenceLength - 1)
  //
  // where sequenceLength is the length of the sequence.
  //
  // the factorial term is the number of ways to order sequenceLength patterns.
  //
  // the D^(sequenceLength-1) term is another length penalty, roughly capturing the idea that an
  // attacker will try lower-length sequences first before trying length-sequenceLength sequences.
  //
  // for example, consider a sequence that is date-repeat-dictionary.
  //  - an attacker would need to try other date-repeat-dictionary combinations,
  //    hence the product term.
  //  - an attacker would need to try repeat-date-dictionary, dictionary-repeat-date,
  //    ..., hence the factorial term.
  //  - an attacker would also likely try length-1 (dictionary) and length-2 (dictionary-date)
  //    sequences before length-3. assuming at minimum D guesses per pattern type,
  //    D^(sequenceLength-1) approximates Sum(D^i for i in [1..sequenceLength-1]
  //
  // ------------------------------------------------------------------------------
  mostGuessableMatchSequence(password, matches, excludeAdditive = false) {
    this.password = password;
    this.excludeAdditive = excludeAdditive;
    const passwordLength = password.length;
    // partition matches into sublists according to ending index j
    let matchesByCoordinateJ = this.fillArray(passwordLength, 'array');
    matches.forEach(match => {
      matchesByCoordinateJ[match.j].push(match);
    });
    // small detail: for deterministic output, sort each sublist by i.
    matchesByCoordinateJ = matchesByCoordinateJ.map(match => match.sort((m1, m2) => m1.i - m2.i));
    this.optimal = {
      // optimal.bestMatches[k][sequenceLength] holds final match in the best length-sequenceLength
      // match sequence covering the
      // password prefix up to k, inclusive.
      // if there is no length-sequenceLength sequence that scores better (fewer guesses) than
      // a shorter match sequence spanning the same prefix,
      // optimal.bestMatches[k][sequenceLength] is undefined.
      bestMatches: this.fillArray(passwordLength, 'object'),
      // same structure as optimal.bestMatches -- holds the product term Prod(bestMatches.guesses for bestMatches in sequence).
      // optimal.guessesProduct allows for fast (non-looping) updates to the minimization function.
      guessesProduct: this.fillArray(passwordLength, 'object'),
      // same structure as optimal.bestMatches -- holds the overall metric.
      totalGuesses: this.fillArray(passwordLength, 'object')
    };
    for (let k = 0; k < passwordLength; k += 1) {
      matchesByCoordinateJ[k].forEach(match => {
        if (match.i > 0) {
          const prevM = this.optimal.bestMatches[match.i - 1];
          Object.keys(prevM).forEach(sequenceLengthStr => {
            const sequenceLength = parseInt(sequenceLengthStr, 10);
            this.update(match, sequenceLength + 1);
          });
        } else {
          this.update(match, 1);
        }
      });
      this.bruteforceUpdate(k);
    }
    const optimalMatchSequence = this.unwind(passwordLength);
    const optimalSequenceLength = optimalMatchSequence.length;
    const guesses = this.getGuesses(password, optimalSequenceLength);
    return {
      password,
      guesses,
      guessesLog10: utils.log10(guesses),
      sequence: optimalMatchSequence
    };
  }
  getGuesses(password, optimalSequenceLength) {
    const passwordLength = password.length;
    if (password.length === 0) {
      return 1;
    } else {
      return this.optimal.totalGuesses[passwordLength - 1][optimalSequenceLength];
    }
  }
}

export { Scoring as default };
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