matching.ex

defmodule Zxcvbn.Matching do
  @moduledoc false

  alias Zxcvbn.Scoring

  @l33t_table %{
    a: ["4", "@"],
    b: ["8"],
    c: ["(", "{", "[", "<"],
    e: ["3"],
    g: ["6", "9"],
    i: ["1", "!", "|"],
    l: ["1", "|", "7"],
    o: ["0"],
    s: ["$", "5"],
    t: ["+", "7"],
    x: ["%"],
    z: ["2"]
  }

  @regexen %{recent_year: ~r/19\d\d|200\d|201\d/}

  @date_max_year 2050
  @date_min_year 1000
  @date_splits %{
    # for length-4 strings, eg 1191 or 9111, two ways to split:
    4 => [
      # 1 1 91 (2nd split starts at index 1, 3rd at index 2)
      [1, 2],
      # 91 1 1
      [2, 3]
    ],
    5 => [
      # 1 11 91
      [1, 3],
      # 11 1 91
      [2, 3]
    ],
    6 => [
      # 1 1 1991
      [1, 2],
      # 11 11 91
      [2, 4],
      # 1991 1 1
      [4, 5]
    ],
    7 => [
      # 1 11 1991
      [1, 3],
      # 11 1 1991
      [2, 3],
      # 1991 1 11
      [4, 5],
      # 1991 11 1
      [4, 6]
    ],
    8 => [
      # 11 11 1991
      [2, 4],
      # 1991 11 11
      [4, 6]
    ]
  }

  @shifted_rx ~r/[~!@#$%^&*()_+QWERTYUIOP{}|ASDFGHJKL:"ZXCVBNM<>?]/

  @max_delta 5

  # ----------------------------------------------------------------------------
  # Matchers
  # ----------------------------------------------------------------------------

  @doc """
  Omnimatch -- combine everything.
  """
  def omnimatch(_password) do
    # matches = []
    # matchers = [
    #   @dictionary_match
    #   @reverse_dictionary_match
    #   @l33t_match
    #   @spatial_match
    #   @repeat_match
    #   @sequence_match
    #   @regex_match
    #   @date_match
    # ]

    # for matcher in matchers
    #   @extend matches, matcher.call(this, password)

    # @sorted matches
  end

  @doc """
  Dictionary match (common passwords, english, last names, etc).
  """
  def dictionary_match(password, ranked_dictionaries \\ ranked_dictionaries())

  def dictionary_match("", _), do: []

  def dictionary_match(password, ranked_dictionaries) do
    password
    |> word_permutations
    |> Enum.flat_map(&dictionaries_matches(ranked_dictionaries, &1, []))
    |> sorted
  end

  defp word_permutations(word) do
    len = String.length(word)

    for i <- 0..len,
        j <- 1..(len - i),
        do: %{i: i, j: i + j - 1, token: String.slice(word, i, j)}
  end

  defp dictionaries_matches([], _, matches), do: matches

  defp dictionaries_matches([head | tail], permutation, matches) do
    matched_word = String.downcase(permutation.token)

    case head.words[matched_word] do
      nil ->
        dictionaries_matches(tail, permutation, matches)

      rank ->
        match = %{
          i: permutation.i,
          j: permutation.j,
          token: permutation.token,
          matched_word: matched_word,
          reversed: false,
          l33t: false,
          rank: rank,
          dictionary_name: head.name,
          pattern: "dictionary"
        }

        dictionaries_matches(tail, permutation, matches ++ [match])
    end
  end

  def reverse_dictionary_match(password, ranked_dictionaries \\ ranked_dictionaries()) do
    password
    |> String.reverse()
    |> dictionary_match(ranked_dictionaries)
    |> Enum.map(&reverse_match(&1, String.length(password)))
    |> sorted
  end

  defp reverse_match(match, length) do
    %{
      match
      | i: length - 1 - match.j,
        j: length - 1 - match.i,
        reversed: true,
        token: String.reverse(match.token)
    }
  end

  @doc """
  Dictionary match with common l33t substitutions.
  """
  def l33t_match(
        _password,
        _ranked_dictionaries \\ ranked_dictionaries(),
        _l33t_table \\ @l33t_table
      ) do
    # matches = []
    # for sub in @enumerate_l33t_subs @relevant_l33t_subtable(password, _l33t_table)
    #   break if @empty sub # corner case: password has no relevant subs.
    #   subbed_password = @translate password, sub
    #   for match in @dictionary_match(subbed_password, _ranked_dictionaries)
    #     token = password[match.i..match.j]
    #     if token.toLowerCase() == match.matched_word
    #       continue # only return the matches that contain an actual substitution
    #     match_sub = {} # subset of mappings in sub that are in use for this match
    #     for subbed_chr, chr of sub when token.indexOf(subbed_chr) != -1
    #       match_sub[subbed_chr] = chr
    #     match.l33t = true
    #     match.token = token
    #     match.sub = match_sub
    #     match.sub_display = ("#{k} -> #{v}" for k,v of match_sub).join(', ')
    #     matches.push match
    # @sorted matches.filter (match) ->
    #   # filter single-character l33t matches to reduce noise.
    #   # otherwise '1' matches 'i', '4' matches 'a', both very common English words
    #   # with low dictionary rank.
    #   match.token.length > 1
  end

  @doc """
  Spatial match (qwerty/dvorak/keypad).
  """
  def spatial_match(_password, _graph \\ graphs()) do
    # matches = []
    # for graph_name, graph of _graphs
    #   @extend matches, @spatial_match_helper(password, graph, graph_name)
    # @sorted matches
  end

  @doc """
  Repeats (aaa, abcabcabc) and sequences (abcdef).
  """
  def repeat_match() do
    # matches = []
    # greedy = /(.+)\1+/g
    # lazy = /(.+?)\1+/g
    # lazy_anchored = /^(.+?)\1+$/
    # lastIndex = 0
    # while lastIndex < password.length
    #   greedy.lastIndex = lazy.lastIndex = lastIndex
    #   greedy_match = greedy.exec password
    #   lazy_match = lazy.exec password
    #   break unless greedy_match?
    #   if greedy_match[0].length > lazy_match[0].length
    #     # greedy beats lazy for 'aabaab'
    #     #   greedy: [aabaab, aab]
    #     #   lazy:   [aa,     a]
    #     match = greedy_match
    #     # greedy's repeated string might itself be repeated, eg.
    #     # aabaab in aabaabaabaab.
    #     # run an anchored lazy match on greedy's repeated string
    #     # to find the shortest repeated string
    #     base_token = lazy_anchored.exec(match[0])[1]
    #   else
    #     # lazy beats greedy for 'aaaaa'
    #     #   greedy: [aaaa,  aa]
    #     #   lazy:   [aaaaa, a]
    #     match = lazy_match
    #     base_token = match[1]
    #   [i, j] = [match.index, match.index + match[0].length - 1]
    #   # recursively match and score the base string
    #   base_analysis = scoring.most_guessable_match_sequence(
    #     base_token
    #     @omnimatch base_token
    #   )
    #   base_matches = base_analysis.sequence
    #   base_guesses = base_analysis.guesses
    #   matches.push
    #     pattern: 'repeat'
    #     i: i
    #     j: j
    #     token: match[0]
    #     base_token: base_token
    #     base_guesses: base_guesses
    #     base_matches: base_matches
    #     repeat_count: match[0].length / base_token.length
    #   lastIndex = j + 1
    # matches
  end

  @doc """
  Identifies sequences by looking for repeated differences in unicode codepoint.
  This allows skipping, such as 9753, and also matches some extended unicode sequences
  such as Greek and Cyrillic alphabets.

  For example, consider the input `'abcdb975zy'`

      password: a   b   c   d   b    9   7   5   z   y
      index:    0   1   2   3   4    5   6   7   8   9
      delta:      1   1   1  -2  -41  -2  -2  69   1

  Expected result:

      [(i, j, delta), ...] = [(0, 3, 1), (5, 7, -2), (8, 9, 1)]

  """
  def sequence_match(_password) do
    # return [] if password.length == 1

    # update = (i, j, delta) =>
    #   if j - i > 1 or Math.abs(delta) == 1
    #     if 0 < Math.abs(delta) <= @MAX_DELTA
    #       token = password[i..j]
    #       if /^[a-z]+$/.test(token)
    #         sequence_name = 'lower'
    #         sequence_space = 26
    #       else if /^[A-Z]+$/.test(token)
    #         sequence_name = 'upper'
    #         sequence_space = 26
    #       else if /^\d+$/.test(token)
    #         sequence_name = 'digits'
    #         sequence_space = 10
    #       else
    #         # conservatively stick with roman alphabet size.
    #         # (this could be improved)
    #         sequence_name = 'unicode'
    #         sequence_space = 26
    #       result.push
    #         pattern: 'sequence'
    #         i: i
    #         j: j
    #         token: password[i..j]
    #         sequence_name: sequence_name
    #         sequence_space: sequence_space
    #         ascending: delta > 0

    # result = []
    # i = 0
    # last_delta = null

    # for k in [1...password.length]
    #   delta = password.charCodeAt(k) - password.charCodeAt(k - 1)
    #   unless last_delta?
    #     last_delta = delta
    #   continue if delta == last_delta
    #   j = k - 1
    #   update(i, j, last_delta)
    #   i = j
    #   last_delta = delta
    # update(i, password.length - 1, last_delta)
    # result
  end

  @doc """
  Regex matching.
  """
  def regex_match(_password, _regexen \\ @regexen) do
    # matches = []
    # for name, regex of _regexen
    #   regex.lastIndex = 0 # keeps regex_match stateless
    #   while rx_match = regex.exec password
    #     token = rx_match[0]
    #     matches.push
    #       pattern: 'regex'
    #       token: token
    #       i: rx_match.index
    #       j: rx_match.index + rx_match[0].length - 1
    #       regex_name: name
    #       regex_match: rx_match
    # @sorted matches
  end

  @doc """
  A "date" is recognized as:

    * any 3-tuple that starts or ends with a 2- or 4-digit year,
    * with 2 or 0 separator chars (1.1.91 or 1191),
    * maybe zero-padded (01-01-91 vs 1-1-91),
    * a month between 1 and 12,
    * a day between 1 and 31.

  Note: this isn't true date parsing in that "feb 31st" is allowed,
  this doesn't check for leap years, etc.

  Recipe:

  Start with regex to find maybe-dates, then attempt to map the integers
  onto month-day-year to filter the maybe-dates into dates.
  finally, remove matches that are substrings of other matches to reduce noise.

  Note: instead of using a lazy or greedy regex to find many dates over the full string,
  this uses a `^...$` regex against every substring of the password -- less performant but leads
  to every possible date match.
  """
  def date_matching(_password) do
    # matches = []
    # maybe_date_no_separator = /^\d{4,8}$/
    # maybe_date_with_separator = ///
    #   ^
    #   ( \d{1,4} )    # day, month, year
    #   ( [\s/\\_.-] ) # separator
    #   ( \d{1,2} )    # day, month
    #   \2             # same separator
    #   ( \d{1,4} )    # day, month, year
    #   $
    # ///

    # # dates without separators are between length 4 '1191' and 8 '11111991'
    # for i in [0..password.length - 4]
    #   for j in [i + 3..i + 7]
    #     break if j >= password.length
    #     token = password[i..j]
    #     continue unless maybe_date_no_separator.exec token
    #     candidates = []
    #     for [k,l] in DATE_SPLITS[token.length]
    #       dmy = @map_ints_to_dmy [
    #         parseInt token[0...k]
    #         parseInt token[k...l]
    #         parseInt token[l...]
    #       ]
    #       candidates.push dmy if dmy?
    #     continue unless candidates.length > 0
    #     # at this point: different possible dmy mappings for the same i,j substring.
    #     # match the candidate date that likely takes the fewest guesses: a year closest to 2000.
    #     # (scoring.REFERENCE_YEAR).
    #     #
    #     # ie, considering '111504', prefer 11-15-04 to 1-1-1504
    #     # (interpreting '04' as 2004)
    #     best_candidate = candidates[0]
    #     metric = (candidate) -> Math.abs candidate.year - scoring.REFERENCE_YEAR
    #     min_distance = metric candidates[0]
    #     for candidate in candidates[1..]
    #       distance = metric candidate
    #       if distance < min_distance
    #         [best_candidate, min_distance] = [candidate, distance]
    #     matches.push
    #       pattern: 'date'
    #       token: token
    #       i: i
    #       j: j
    #       separator: ''
    #       year: best_candidate.year
    #       month: best_candidate.month
    #       day: best_candidate.day

    # # dates with separators are between length 6 '1/1/91' and 10 '11/11/1991'
    # for i in [0..password.length - 6]
    #   for j in [i + 5..i + 9]
    #     break if j >= password.length
    #     token = password[i..j]
    #     rx_match = maybe_date_with_separator.exec token
    #     continue unless rx_match?
    #     dmy = @map_ints_to_dmy [
    #       parseInt rx_match[1]
    #       parseInt rx_match[3]
    #       parseInt rx_match[4]
    #     ]
    #     continue unless dmy?
    #     matches.push
    #       pattern: 'date'
    #       token: token
    #       i: i
    #       j: j
    #       separator: rx_match[2]
    #       year: dmy.year
    #       month: dmy.month
    #       day: dmy.day

    # # matches now contains all valid date strings in a way that is tricky to capture
    # # with regexes only. while thorough, it will contain some unintuitive noise:
    # #
    # # '2015_06_04', in addition to matching 2015_06_04, will also contain
    # # 5(!) other date matches: 15_06_04, 5_06_04, ..., even 2015 (matched as 5/1/2020)
    # #
    # # to reduce noise, remove date matches that are strict substrings of others
    # @sorted matches.filter (match) ->
    #   is_submatch = false
    #   for other_match in matches
    #     continue if match is other_match
    #     if other_match.i <= match.i and other_match.j >= match.j
    #       is_submatch = true
    #       break
    #   not is_submatch
  end

  # ----------------------------------------------------------------------------
  # Helpers
  # ----------------------------------------------------------------------------

  # makes a pruned copy of l33t_table that only includes password's possible substitutions
  defp relevant_l33t_subtable(_password, _table) do
    # password_chars = {}

    # for chr in password.split('')
    #   password_chars[chr] = true

    # subtable = {}

    # for letter, subs of table
    #   relevant_subs = (sub for sub in subs when sub of password_chars)
    #   if relevant_subs.length > 0
    #     subtable[letter] = relevant_subs

    # subtable
  end

  # returns the list of possible 1337 replacement dictionaries for a given password
  defp enumerate_l33t_subs(_table) do
    # keys = (k for k of table)
    # subs = [[]]

    # dedup = (subs) ->
    #   deduped = []
    #   members = {}
    #   for sub in subs
    #     assoc = ([k,v] for k,v in sub)
    #     assoc.sort()
    #     label = (k+','+v for k,v in assoc).join('-')
    #     unless label of members
    #       members[label] = true
    #       deduped.push sub
    #   deduped

    # helper = (keys) ->
    #   return if not keys.length
    #   first_key = keys[0]
    #   rest_keys = keys[1..]
    #   next_subs = []

    #   for l33t_chr in table[first_key]
    #     for sub in subs
    #       dup_l33t_index = -1
    #       for i in [0...sub.length]
    #         if sub[i][0] == l33t_chr
    #           dup_l33t_index = i
    #           break
    #       if dup_l33t_index == -1
    #         sub_extension = sub.concat [[l33t_chr, first_key]]
    #         next_subs.push sub_extension
    #       else
    #         sub_alternative = sub.slice(0)
    #         sub_alternative.splice(dup_l33t_index, 1)
    #         sub_alternative.push [l33t_chr, first_key]
    #         next_subs.push sub
    #         next_subs.push sub_alternative

    #   subs = dedup next_subs
    #   helper(rest_keys)

    # helper(keys)
    # sub_dicts = [] # convert from assoc lists to dicts
    # for sub in subs
    #   sub_dict = {}
    #   for [l33t_chr, chr] in sub
    #     sub_dict[l33t_chr] = chr
    #   sub_dicts.push sub_dict
    # sub_dicts
  end

  defp spatial_match_helper(_password, _graph, _graph_name) do
    # matches = []
    # i = 0
    # while i < password.length - 1
    #   j = i + 1
    #   last_direction = null
    #   turns = 0
    #   if graph_name in ['qwerty', 'dvorak'] and @SHIFTED_RX.exec(password.charAt(i))
    #     # initial character is shifted
    #     shifted_count = 1
    #   else
    #     shifted_count = 0
    #   loop
    #     prev_char = password.charAt(j-1)
    #     found = false
    #     found_direction = -1
    #     cur_direction = -1
    #     adjacents = graph[prev_char] or []
    #     # consider growing pattern by one character if j hasn't gone over the edge.
    #     if j < password.length
    #       cur_char = password.charAt(j)
    #       for adj in adjacents
    #         cur_direction += 1
    #         if adj and adj.indexOf(cur_char) != -1
    #           found = true
    #           found_direction = cur_direction
    #           if adj.indexOf(cur_char) == 1
    #             # index 1 in the adjacency means the key is shifted,
    #             # 0 means unshifted: A vs a, % vs 5, etc.
    #             # for example, 'q' is adjacent to the entry '2@'.
    #             # @ is shifted w/ index 1, 2 is unshifted.
    #             shifted_count += 1
    #           if last_direction != found_direction
    #             # adding a turn is correct even in the initial case when last_direction is null:
    #             # every spatial pattern starts with a turn.
    #             turns += 1
    #             last_direction = found_direction
    #           break
    #     # if the current pattern continued, extend j and try to grow again
    #     if found
    #       j += 1
    #     # otherwise push the pattern discovered so far, if any...
    #     else
    #       if j - i > 2 # don't consider length 1 or 2 chains.
    #         matches.push
    #           pattern: 'spatial'
    #           i: i
    #           j: j-1
    #           token: password[i...j]
    #           graph: graph_name
    #           turns: turns
    #           shifted_count: shifted_count
    #       # ...and then start a new search for the rest of the password.
    #       i = j
    #       break
    # matches
  end

  # Given a 3-tuple, discard if:
  #   * middle int is over 31 (for all dmy formats, years are never allowed in the middle)
  #   * middle int is zero
  #   * any int is over the max allowable year
  #   * any int is over two digits but under the min allowable year
  #   * 2 ints are over 31, the max allowable day
  #   * 2 ints are zero
  #   * all ints are over 12, the max allowable month
  defp map_ints_to_dmy(_ints) do
    # return if ints[1] > 31 or ints[1] <= 0
    # over_12 = 0
    # over_31 = 0
    # under_1 = 0
    # for int in ints
    #   return if 99 < int < DATE_MIN_YEAR or int > DATE_MAX_YEAR
    #   over_31 += 1 if int > 31
    #   over_12 += 1 if int > 12
    #   under_1 += 1 if int <= 0
    # return if over_31 >= 2 or over_12 == 3 or under_1 >= 2

    # # first look for a four digit year: yyyy + daymonth or daymonth + yyyy
    # possible_year_splits = [
    #   [ints[2], ints[0..1]] # year last
    #   [ints[0], ints[1..2]] # year first
    # ]
    # for [y, rest] in possible_year_splits
    #   if DATE_MIN_YEAR <= y <= DATE_MAX_YEAR
    #     dm = @map_ints_to_dm rest
    #     if dm?
    #       return {
    #         year: y
    #         month: dm.month
    #         day: dm.day
    #       }
    #     else
    #       # for a candidate that includes a four-digit year,
    #       # when the remaining ints don't match to a day and month,
    #       # it is not a date.
    #       return

    # # given no four-digit year, two digit years are the most flexible int to match, so
    # # try to parse a day-month out of ints[0..1] or ints[1..0]
    # for [y, rest] in possible_year_splits
    #   dm = @map_ints_to_dm rest
    #   if dm?
    #     y = @two_to_four_digit_year y
    #     return {
    #       year: y
    #       month: dm.month
    #       day: dm.day
    #     }
  end

  defp map_ints_to_dm(_ints) do
    # for [d, m] in [ints, ints.slice().reverse()]
    #   if 1 <= d <= 31 and 1 <= m <= 12
    #     return {
    #       day: d
    #       month: m
    #     }
  end

  defp two_to_four_digit_year(year) do
    cond do
      year > 99 -> year
      # 87 -> 1987
      year > 50 -> year + 1900
      # 15 -> 2015
      true -> year + 2000
    end
  end

  defp ranked_dictionaries do
    Enum.map(frequency_lists(), fn {k, v} ->
      {k, build_ranked_dict(v)}
    end)
  end

  defp build_ranked_dict(_ordered_list) do
    # result = {}
    # i = 1 # rank starts at 1, not 0
    # for word in ordered_list
    #   result[word] = i
    #   i += 1
    # result
  end

  defp empty?(_obj) do
    # (k for k of obj).length == 0
  end

  defp extend(_list1, _list2) do
    # lst.push.apply lst, lst2
  end

  defp translate(_string, _chr_map) do
    # (chr_map[chr] or chr for chr in string.split('')).join('')
  end

  defp mod(_n, _m) do
    # ((n % m) + m) % m # mod impl that works for negative numbers
  end

  def sorted([]), do: []

  def sorted(matches) do
    matches |> Enum.sort(&(&1.i < &2.i or (&1.i == &2.i and &1.j < &2.j)))
  end

  defp frequency_lists, do: Zxcvbn.Data.FrequencyLists.all()

  defp graphs, do: Zxcvbn.Data.AdjacencyGraphs.all()
end