random text replacement generator

example_output.txt

lua gen.lua --times=25 sample.txt

Your pack contains another rucksack containing a shard of bone, some lint and an old bronze ring.
Your bag contains a tin of tobacco, an old bronze ring and a tin of tobacco.
Your pack contains a tin of tobacco, some lint and another bag containing another pack containing a handkerchief.
Your knapsack contains another bag containing an old bronze ring, a tin of tobacco and a tin of tobacco.
Your pack contains an old silver ring, a tin of tobacco and a shard of bone.
Your purse contains another backpack containing a tin of tobacco, some lint and some lint.
Your bag contains some coins, another rucksack containing some coins and some coins.
Your bag contains a tin of tobacco, an old silver ring and an old silver ring.
Your bag contains another knapsack containing a handkerchief, another bag containing another pack containing some coins and a tin of tobacco.
Your bag contains an old bronze ring, a tin of tobacco and a tin of tobacco.
Your purse contains some coins, an old silver ring and a tin of tobacco.
Your purse contains a tin of tobacco, a tin of tobacco and a shard of bone.
Your pack contains some coins, some lint and an old silver ring.
Your pack contains another pack containing a tin of tobacco, a shard of bone and some coins.
Your purse contains a handkerchief, some coins and a shard of bone.
Your pack contains an old bronze ring, a tin of tobacco and some lint.
Your pack contains some coins, some lint and some coins.
Your bag contains a handkerchief, some lint and an old bronze ring.
Your purse contains a shard of bone, a handkerchief and an old silver ring.
Your bag contains another rucksack containing a tin of tobacco, a handkerchief and some coins.
Your knapsack contains a shard of bone, a handkerchief and some coins.
Your bag contains a tin of tobacco, an old bronze ring and another bag containing an old silver ring.
Your knapsack contains another purse containing another purse containing another knapsack containing some lint, a tin of tobacco and another pack containing an old bronze ring.
Your bag contains a tin of tobacco, an old bronze ring and another pack containing a shard of bone.
Your bag contains another backpack containing a tin of tobacco, a handkerchief and some coins.

gen.lua

math.randomseed(os.time())
math.random()
math.random()
math.random()

function createState()
  local state = {
    outputs = {},
    sets = {},
    mode = 'outputs',
  }
  return state
end

function preprocess(line, state)
  line = line:match("^%s*(.*)%s*$")
  local includeFile = string.match(line, "^#include \"([^\"]+)\"")
  if includeFile then
    parseFile(includeFile, state)
    return ""
  end
  return line
end

function parseLine(line, state)
  if line ~= nil and #line > 0 then
    if line:sub(1,1)=='[' then
      assert(line:sub(-1)==']', 'set declaration must end with right bracket')
      state.mode = 'sets'
      state.currSet = line:sub(2, -2)
      state.sets[state.currSet] = state.sets[state.currSet] or {}
      assert(#state.currSet>1, 'set declaration is empty')
    else
      if state.mode == 'outputs' then
        table.insert(state.outputs, line)
      else
        table.insert(state.sets[state.currSet], line)
      end
    end
  end
  return state
end

function parseFile(filename, state)
  for line in io.lines(filename) do
    line = preprocess(line, state)
    parseLine(line, state)
  end
  return state
end

function split(s, sep)
  local o = {}
  for k in string.gmatch(s, "[^|]+") do
    o[#o+1] = k
  end
  return o
end

function pick(collection)
  return collection[math.random(1, #collection)]
end

function resolveBrackets(line)
  return line:gsub("{[^{}]-}", function(s)
    return pick(split(s:sub(2, -2), '|'))
  end)
end

function runLine(line, sets)
  line = resolveBrackets(line)
  return line:gsub("<.->", function(s)
    return runLine(pick(sets[s:sub(2, -2)]), sets)
  end)
end

function run(output, sets)
  for i = 1, #output do
    io.write(runLine(output[1], sets), '\n')
  end
end

function options(...)
  local opt = {}
  for i = 1, select('#', ...) do
    local arg = select(i, ...)
    if arg:sub(1,1) == '-' then
      local param, value = arg:match('%-%-?([^-=]+)=?(.*)')
      if value == nil then value = true end
      opt[param] = value
    else
      opt[#opt+1] = arg
    end
  end
  return opt
end

function main(opt)
  local times = tonumber(opt['times']) or 1
  for i = 1, #opt do
    local state = createState()
    local output, sets = parseFile(opt[i], state)
    for j = 1, times do
      run(state.outputs, state.sets)
    end
  end
end

function globalerror(_, index) error("global access: "..index) end
setmetatable(_G, { __newindex = globalerror, __index = globalerror })

main(options(...))

sample.txt

Your <pack> contains <item>, <item> and <item>.

[item]
some coins
an old {silver|bronze} ring
a handkerchief
a shard of bone
some lint
a tin of tobacco
another <pack> containing <item>

[pack]
pack
#include "sample_packs.txt"

sample_packs.txt

purse
backpack
bag
knapsack
rucksack