#!/usr/bin/env lua

require 'luasql.postgres'
require 'config'
require 'base64'
local base64 = enc

function generate_token() -- generates a new token (the next)
  local len = config.key_len / 8 * 6
  local f = io.open("/dev/urandom","r")
  local r = f:read(len)
  return base64(r)
end

function add_token(token) -- add token to the database
  local env = luasql.postgres()
  local con = env:connect(config.db)

  local now = os.time()
  math.randomseed(now)
  local prefix = token:sub(1, config.prefix_len)
  local ttl = now + config.ttl + math.floor(math.random() * config.ruttl)
  local ttrd = config.ttrd  + math.floor(math.random() * config.ruttl) 
  local ruttl = math.floor((math.random()+0.5) * config.ruttl)
  local update = "delete from tokens where prefix='"..prefix.."';"
  local insert = "insert into tokens (prefix, token, ttl) values ('"..prefix.."', '"..token.."', "..ttl..");"
  local gravedigger = "insert into graveyard (prefix, token, ttrd) select prefix, token, ttl+"..ttrd.." from tokens where ttl<"..now..";"
  local clean = "delete from tokens where ttl<"..now..";"
  local dig = "delete from graveyard where ttrd<"..now..";"
  assert(con:execute(gravedigger .. clean .. dig .. update .. insert .. update .. insert))

  con:close()
  env:close()
end

function check_token(token) -- checks if the token is valid
  if not is_base64(token) then return false end
  local env = luasql.postgres()
  local con = env:connect(config.db)
  local result = true
  local ttl = con:execute("select ttl from tokens where token='"..token.."';"):fetch() 
  if ttl == nil then result = false end
  if type(ttl) == "number" then if tonumber(ttl) < os.time() then result = false end end
  con:close()
  env:close()
  return result
end

function set_prefix(old, new) -- sets the prefix from the old token on the new token
  local prefix = old:sub(1, config.prefix_len)
  return prefix .. new:sub(config.prefix_len+1)
end