class Alphabetify

Constants

HASH_CHARS

Alphabetify.rb Generates sequential alphabetic hashes

Author: Todd Resudek - toddresudek@gmail.com | github: sprsmpl

Description: Taking an existing alphabetic hash (of any length), will return the next hash in sequence. If all characters in hash are rolled over, will append a new char (increase the length by 1.) eg. ‘ZZZZ’ -> ‘AAAAA’ eg. ‘AAAZ’ -> ‘AABA’

Seed the first hash - whatever length you’d like to start with - to begin.

Usage: Alphabetify.generate_hash(‘THELASTHASHUSED’)

Public Class Methods

generate_hash() click to toggle source

# File lib/alphabetify.rb, line 22
def self.generate_hash
  str = get_last_hash
  complete = false
  new_hash = ''
  str.chars.reverse.each do |ch|
    #check this char for a rollover, if it does not need a rollver, exit
    unless complete
      #replace this char with the next char
      next_char, rollover = get_next_char(ch)
      new_hash << next_char
    else
      #keep this char
      new_hash << ch
    end
    complete = true unless rollover
  end
  #need to add another character to the end if all letters rollover
  if !complete
    new_hash.reverse! << HASH_CHARS.first
  end
  result = new_hash.reverse
  set_last_hash(result)
  result
end

seed_hash(seed) click to toggle source

This method can be used (preferably only once, to set the initial hash)

# File lib/alphabetify.rb, line 48
def self.seed_hash(seed)
  #Check seed against HASH_CHARS. Throw error if any characters arent allowed
  raise ArgumentError.new("The seed cannot be empty.") if seed.to_s.empty? 
  unless seed.to_s.each_char.detect{|c| !HASH_CHARS.include?(c) }
    set_last_hash(seed)
    get_last_hash
  else
    raise ArgumentError.new("The seed can only contain characters in #{HASH_CHARS.join}.")
  end
end

Private Class Methods

get_last_hash() click to toggle source

# File lib/alphabetify.rb, line 61
def self.get_last_hash
  File.read( File.join( __dir__, 'last-hash.txt' )  )
end

get_next_char(char) click to toggle source

# File lib/alphabetify.rb, line 69
def self.get_next_char(char)
  unless char == HASH_CHARS.last
    return [char.next,false]
  else
    return [HASH_CHARS.first,true]
  end     
end

leading_chars(current_hash) click to toggle source

# File lib/alphabetify.rb, line 77
def self.leading_chars(current_hash)
  last_char = current_hash.slice!(-1)    
  [current_hash,last_char]
end

rollover() click to toggle source

# File lib/alphabetify.rb, line 82
def self.rollover
  new_last_char, needs_rollover = next_char(last_char)
end

set_last_hash(new_value) click to toggle source

# File lib/alphabetify.rb, line 65
def self.set_last_hash(new_value)
  File.open( File.join( __dir__, 'last-hash.txt' ), 'w+') {|f| f.write(new_value) }
end