-- httpserver-request
-- Part of nodemcu-httpserver, parses incoming client requests.
-- Author: Marcos Kirsch

local function validateMethod(method)
   local httpMethods = {GET=true, HEAD=true, POST=true, PUT=true, DELETE=true, TRACE=true, OPTIONS=true, CONNECT=true, PATCH=true}
   -- default for non-existent attributes returns nil, which evaluates to false
   return httpMethods[method]
end

local function uriToFilename(uri)
   return string.sub(uri, 2, -1)
end

local function hex_to_char(x)
  return string.char(tonumber(x, 16))
end

local function uri_decode(input)
  return input:gsub("%+", " "):gsub("%%(%x%x)", hex_to_char)
end

local function parseArgs(args)
   local r = {}; i=1
   if args == nil or args == "" then return r end
   for arg in string.gmatch(args, "([^&]+)") do
      local name, value = string.match(arg, "(.*)=(.*)")
      if name ~= nil then r[name] = uri_decode(value) end
      i = i + 1
   end
   return r
end

local function parseFormData(body)
   local data = {}
   --print("Parsing Form Data")
   for kv in body.gmatch(body, "%s*&?([^=]+=[^&]+)") do
      local key, value = string.match(kv, "(.*)=(.*)")
      --print("Parsed: " .. key .. " => " .. value)
      data[key] = uri_decode(value)
   end
   return data
end

local function isCheckModifiedRequest(payload)
   return function ()
      local checkResult = (string.find(payload, 'If%-Modified%-Since: ') ~= nil)
      return checkResult
   end
end

local function getRequestData(payload)
   local requestData
   return function ()
      --print("Getting Request Data")
      if requestData then
         return requestData
      else
         --print("payload = [" .. payload .. "]")
         local mimeType = string.match(payload, "Content%-Type: ([%w/-]+)")
         local bodyStart = payload:find("\r\n\r\n", 1, true)
         local body = payload:sub(bodyStart, #payload)
         payload = nil
         collectgarbage()
         --print("mimeType = [" .. mimeType .. "]")
         --print("bodyStart = [" .. bodyStart .. "]")
         --print("body = [" .. body .. "]")
         if mimeType == "application/json" then
            --print("JSON: " .. body)
            requestData = sjson.decode(body)
         elseif mimeType == "application/x-www-form-urlencoded" then
            requestData = parseFormData(body)
         else
            requestData = {}
         end
         return requestData
      end
   end
end

local function parseUri(uri)
   local r = {}
   local filename
   local ext
   local fullExt = {}

   if uri == nil then return r end
   if uri == "/" then uri = "/index.html" end
   questionMarkPos, b, c, d, e, f = uri:find("?")
   if questionMarkPos == nil then
      r.file = uri:sub(1, questionMarkPos)
      r.args = {}
   else
      r.file = uri:sub(1, questionMarkPos - 1)
      r.args = parseArgs(uri:sub(questionMarkPos+1, #uri))
   end
   filename = r.file
   while filename:match("%.") do
      filename,ext = filename:match("(.+)%.(.+)")
      table.insert(fullExt,1,ext)
   end
   if #fullExt > 1 and fullExt[#fullExt] == 'gz' then
      r.ext = fullExt[#fullExt-1]
      r.isGzipped = true
   elseif #fullExt >= 1 then
      r.ext = fullExt[#fullExt]
   end
   r.isScript = r.ext == "lua" or r.ext == "lc"
   r.file = uriToFilename(r.file)
   return r
end

-- Parses the client's request. Returns a dictionary containing pretty much everything
-- the server needs to know about the uri.
return function (request)
   --print("Request: \n", request)
   local e = request:find("\r\n", 1, true)
   if not e then return nil end
   local line = request:sub(1, e - 1)
   local r = {}
   _, i, r.method, r.request = line:find("^([A-Z]+) (.-) HTTP/[1-9]+.[0-9]+$")
   r.methodIsValid = validateMethod(r.method)
   r.uri = parseUri(r.request)
   r.isCheckModifiedRequest = isCheckModifiedRequest(request)
   r.getRequestData = getRequestData(request)
   return r
end
