-- lib/supple/request.lua
--
-- Sandbox (for) Untrusted Procedure Partitioning (in) Lua Engine
--
-- Request/response serialisation/deserialisation including contextual object
-- management and organisation.
--
-- Copyright 2012 Daniel Silverstone <dsilvers@digital-scurf.org>
--
-- For licence terms, see COPYING
--

local capi = require 'supple.capi'
local objects = require 'supple.objects'

local tconcat = table.concat
local ipairs = ipairs
local select = select
local loadstring = loadstring
local load = load
local setfenv = setfenv

local function serialise_error(errstr, traceback)
   return tconcat {
      "error=true,",
      ("message=%q,"):format(errstr),
      ("traceback=%q"):format(traceback)
   }
end

local function _serialise_object(obj, ret)
   ret[#ret+1] = "{"
   local comma = ""
   if obj.type then
      ret[#ret+1] = ("type=%q"):format(obj.type)
      comma = ","
   end
   ret[#ret+1] = ("%stag=%q"):format(comma, obj.tag)
   if obj.methods then
      ret[#ret+1] = ",methods={"
      comma = ""
      for _, meth in ipairs(obj.methods) do
	 ret[#ret+1] = ("%s%q"):format(comma, meth)
	 comma = ","
      end
      ret[#ret+1] = "}"
   end
   ret[#ret+1] = "}"
end

local function serialise_request(obj, method, ...)
   assert(capi.rawtype(obj) == "string")
   assert(capi.rawtype(method) == "string")
   local args = { n = select("#", ...), ... }
   local ret = {
      ("object=%q,"):format(obj),
      ("method=%q,"):format(method),
      ("args={n=%d"):format(args.n)
   }

   for i = 1, args.n do
      local v = objects.give(args[i])
      if capi.rawtype(v) == "string" then
	 ret[#ret+1] = (",%q"):format(v)
      elseif capi.rawtype(v) == "table" then
	 ret[#ret+1] = ","
	 _serialise_object(v, ret)
      else
	 ret[#ret+1] = "," .. tostring(v)
      end
   end

   ret[#ret+1] = "}"
   return tconcat(ret)
end

local function serialise_response(...)
   local args = { n = select("#", ...), ... }
   local ret = {
      "error=false,",
      ("results={n=%d"):format(args.n)
   }

   for i = 1, args.n do
      local v = objects.give(args[i])
      if capi.rawtype(v) == "string" then
	 ret[#ret+1] = (",%q"):format(v)
      elseif capi.rawtype(v) == "table" then
	 ret[#ret+1] = ","
	 _serialise_object(v, ret)
      else
	 ret[#ret+1] = "," .. tostring(v)
      end
   end

   ret[#ret+1] = "}"
   return tconcat(ret)
end

local function deserialise_entity(entity)
   local str = ("return {%s}"):format(entity)
   local fn
   if setfenv ~= nil then
      fn = setfenv(assert(loadstring(str, "@supple-transfer")), {})
   else
      fn = load(str, "@supple-transfer", "t", {})
   end
   local res = fn()
   local walk = res.args or res.results
   if walk then
      assert(walk.n, "Elements missing 'n'")
      for i = 1, walk.n do
	 walk[i] = objects.receive(walk[i])
      end
   end
   return res
end

return {
   error = serialise_error,
   request = serialise_request,
   response = serialise_response,
   deserialise = deserialise_entity,
}