LZ78

local trm = require("term")
local shl = require("shell")
local fls = require("filesystem")
local b32 = require("bit32")
local args = shl.parse(...)

VALUE = 0 LEN = 0
function AddBite(value, len)
  VALUE = b32.lshift(VALUE, len) + value
  LEN = LEN + len
  while LEN > 7 do
    file:write(string.char(b32.rshift(VALUE, LEN - 8)))
    VALUE = VALUE % (2 ^ (LEN - 8))
    LEN = LEN - 8
  end
end

function deflate()
  file = io.open(args[1], "rb")
  if file == nil then trm.write("file "..args[1].." not found") os.exit()
  end
  STR = file:read("*a")
  file:close()

  local dict = {[""] = 0}
  local DLEN = 1
  local word = ""

  file = io.open(args[2], "wb")
  if file == nil then trm.write("file "..args[2].." already in use") os.exit()
  end
  for i=1, #STR do
    word = word..STR:sub(i, i)
    if dict[word] == nil then
      AddBite(dict[word:sub(1, -2)], math.ceil(math.log(DLEN+1, 2)))
      AddBite(word:byte(-1), 8)
      dict[word] = DLEN DLEN = DLEN + 1
      word = ""
    end
  end
  if word ~= "" then
    AddBite(dict[word], math.ceil(math.log(DLEN+1, 2)))
  end
  if LEN ~= 0 then
    file:write(string.char(b32.lshift(VALUE, 8 - LEN)))
  end
  file:close()
end

function PutBite(len)
  while LEN < len do
    if POS > #STR1 then return false
    end
    VALUE = VALUE * 256 + STR1:byte(POS)
    POS = POS + 1
    LEN = LEN + 8
  end
  LEN = LEN - len
  local tmp = b32.rshift(VALUE, LEN)
  VALUE = VALUE % (2 ^ LEN)
  return tmp
end


function inflate()
  file = io.open(args[2], "rb")
  if file == nil then trm.write("file "..args[2].." file no found") os.exit()
  end
  STR1 = file:read("*a")
  file:close()
  LEN = 0
  POS = 1
  VALUE = 0
  local dict = {[0] = ""}
  local DLE = 1
  OUT = ""
  while true do
    local TEMP = PutBite(math.ceil(math.log(DLE+1, 2)))
    local symbol = PutBite(8)
    if TEMP == false then break
    end
    if symbol == false then
      OUT = OUT..dict[TEMP]
      break
    else
      symbol = string.char(symbol)
      OUT = OUT..dict[TEMP]..symbol
      dict[DLE] = dict[TEMP]..symbol DLE = DLE + 1
    end
  end
end

deflate()
inflate()