local Luan = require "luan:Luan.luan"
local error = Luan.error
local Http = require "luan:http/Http.luan"
local Pic = require "site:/lib/Pic.luan"
local User = require "site:/lib/User.luan"
local Db = require "site:/lib/Db.luan"
local run_in_transaction = Db.run_in_transaction or error()


return function()
	local user = User.current() or error()
	local pic_id = Http.request.parameters.pic or error()
	local prev_id = Http.request.parameters.prev or error()
	run_in_transaction( function()
		local pic = Pic.get_by_id(pic_id) or error()
		pic.user_id == user.id or error()
		local prev
		if prev_id == "null" then
			prev = nil
		else
			prev = Pic.get_by_id(prev_id) or error()
		end
		pic.move_after(prev)
		pic.save()
	end )
end