local Luan = require "luan:Luan.luan"
local error = Luan.error
local pairs = Luan.pairs or error()
local Table = require "luan:Table.luan"
local concat = Table.concat or error()
local is_empty = Table.is_empty or error()
local Http = require "luan:http/Http.luan"
local Shared = require "site:/lib/Shared.luan"
local http_push_to_users = Shared.http_push_to_users or error()
local User = require "site:/lib/User.luan"
local current_user = User.current or error()
local get_user_by_email = User.get_by_email or error()
local Utils = require "site:/lib/Utils.luan"
local to_set = Utils.to_set or error()
local Db = require "site:/lib/Db.luan"
local run_in_transaction = Db.run_in_transaction or error()
local Chat = require "site:/lib/Chat.luan"
local get_chat_by_user_ids = Chat.get_by_user_ids or error()


return function()
	local with = Http.request.parameters.with
	local user = current_user()
	with = to_set(with)
	if user == nil then
		local url = "/login.html"
		if not is_empty(with) then
			local t = {}
			for email in pairs(with) do
				t[#t+1] = "with="..email
			end
			url = url.."?"..concat(t,"&")
		end
		Http.response.send_redirect(url)
		return
	end
	if is_empty(with) then
		Http.response.send_redirect("/")
		return
	end
	with[user.email] = true
	local ids = {}
	for email in pairs(with) do
		local with_user = get_user_by_email(email) or error()
		local id = with_user.id
		ids[#ids+1] = id
	end
	local need_push = false
	local chat = run_in_transaction( function()
		local chat = get_chat_by_user_ids(ids)
		if chat == nil then
			chat = Chat.new{
				user_ids = ids
			}
			chat.save()
			need_push = true
		end
		return chat
	end )
	if need_push then
		local js = "getChats('"..chat.id.."')"
		http_push_to_users( chat.user_ids, js )
	end
	Http.response.send_redirect("/?chat="..chat.id)
end