find_unknown_value.rb

# frozen_string_literal: true

require 'damerau-levenshtein'

BEST_GUESS_DISTANCE = 10

# Performs Levenshtein distance and partial match detection on unknown_value within list of known_values.
def find_unknown_value(known_values, unknown_value)
  # find levenshtein best guess
  lev_best_guess = perform_levenshtein(unknown_value, known_values)

  # levenshtein won't find partial matches
  # (e.g. if we are looking for 'max', we expect 'max_bright' to be a possible guess)
  # so look for partials in command list
  possible_partials = find_partials(unknown_value, known_values)

  # don't add levenshtein guess if already in partial list
  possible_partials.append(lev_best_guess) if !possible_partials.include?(lev_best_guess) && lev_best_guess != ''

  possible_partials
end

def find_partials(unknown_command, known_commands)
  possible = []
  known_commands.each do |command|
    possible.append(command) if command.include? unknown_command
  end
  possible
end

# returns a single best guess or empty string if distance is too high
def perform_levenshtein(unknown_command, known_commands)
  dl = DamerauLevenshtein

  best_guess = ''
  best_guess_distance = -1

  known_commands.each do |command|
    guess_distance = dl.distance(command, unknown_command)
    next unless best_guess.empty? || guess_distance <= best_guess_distance

    best_guess = command
    best_guess_distance = guess_distance
    next
  end

  # Return empty string if best_guess_distance is really high
  # How helpful would it be to provide a suggested match to 'ashpoijeiphasdrtqadjh' ?
  if best_guess_distance < BEST_GUESS_DISTANCE
    best_guess
  else
    ''
  end
end