# start with our cyphertext
$orig = <<HERE
YRFFJ OSLXA PQPQY APVRR DPNSA ZAPIK
OXMQJ BOIMY XMSZZ FRIHE AUXJS IOROR
IEAHB QYAPQ YRHXJ STRIF ORIEX KOIKD
REAQK JHBOI QSFIQ AJHPA QPKIF FREKO
XMQJB OIGAA LRKIS PRNSA Z13VI PIKOX
MQJBO IGNSA ZIPVR FFYJM RXJSY IEUSH
HERE

# get rid of the spacing
cyp = $orig.gsub(/\s+/, '')

# count frequencies
f = Hash.new(0)
cyp.each_char {|i| f[i] += 1}

$letters = f.keys.sort_by {|i| -f[i]}.map {|x| [x, 100.0 * f[x] / (5*36)]}
p $letters

# paste in the letter frequency chart from wikipedia
$chart = %{
a 	8.167%
b 	1.492%
c 	2.782%
d 	4.253%
e 	12.702%
f 	2.228%
g 	2.015%
h 	6.094%
i 	6.966%
j 	0.153%
k 	0.772%
l 	4.025%
m 	2.406%
n 	6.749%
o 	7.507%
p 	1.929%
q 	0.095%
r 	5.987%
s 	6.327%
t 	9.056%
u 	2.758%
v 	0.978%
w 	2.360%
x 	0.150%
y 	1.974%
z 	0.074%
}.gsub(/%/, '').split(/\n/)

$chart.shift
$chart = $chart.map {|i| i.split(/\s+/)}.map {|p| [p[0], p[1].to_f]}.sort_by {|p| -p[1]}
p $chart

# okay, now we're getting somewhere. let's line the two up
c = $letters.zip($chart).map {|a,b| [a[0], b[0]]}
p c

# paste in the substitution chart so we can handtweak it
sub = [["I", "e"], ["R", "t"], ["A", "a"], ["O", "o"], ["S", "i"], ["Q", "n"],
  ["P", "s"], ["J", "h"], ["F", "r"], ["X", "d"], ["K", "l"], ["Y", "c"], 
  ["E", "u"], ["H", "m"], ["M", "w"], ["B", "f"], ["Z", "g"], ["V", "y"], 
  ["N", "p"], ["D", "b"], ["U", "v"], ["L", "k"], ["G", "j"], ["T", "x"], 
  ["1", "q"], ["3", "z"]]

o = $orig.dup
sub.each {|i, j| o.gsub! i, j}
puts o # =>
# ctrrh oikda snsnc asytt bspia gasel
# odwnh foewc dwigg rtemu avdhi eotot
# euamf ncasn ctmdh ixter oteud loelb
# tuanl hmfoe niren ahmsa nsler rtulo
# dwnhf oejaa ktlei stpia gqzye selod
# wnhfo ejpia gesyt rrchw tdhic euvim

# oh well :) try something else
# let's make sub a hash, for easier tweaking
$subs = Hash[*sub.flatten]
class << $subs
  def assign(x, y)
    old = self.index(y)
    self[old] = self[x]
    self[x] = y
  end

  def display
    self.keys.sort_by {|x| self[x]}.map {|x| [x, self[x]]}.transpose.map(&:join)
  end
end

p $subs
def try(*xys)
  o = $orig.dup
  xys.each {|xy| 
    x, y = xy.to_s.split(//)
    x = x.upcase
    $subs.assign(x,y)
  }
  $subs.each {|i, j| o.gsub! i, j}
  puts 
  puts $chart.map(&:first).join
  puts $letters.map(&:first).join
  puts $subs.display
  puts o.zip($orig)
end

def method_missing(meth)
  meth.to_s
end

# lots of FF - maybe F = e 
try fe # nope, maybe F = s?
try fs # the word 'grey' has appeared :) also 'bepia', suggesting a colour theme
try ds # nah
try ft # NSA = the?
try nt, sh, ae # note "the gray". still pondering all those FFs
try ro, fn # R is high-probability too
try jy # sorry?
try ys, fr # sorry i?
try oi