-- store which player is monitoring the NPC (for preconditions and
-- effects)
yl_speak_up.debug_mode_set_by_player = {}

-- for sending debug information about preconditions and effects to
-- the player who is monitoring the NPC
-- (sometimes it is not easy/obvious to see why something failed)
yl_speak_up.debug_msg = function(player, n_id, o_id, text)
	local dname = yl_speak_up.debug_mode_set_by_player[ n_id ]
	-- nobody cares
	if(not(dname)) then
		return
	end
	local pname = player:get_player_name()
	local d_id = yl_speak_up.speak_to[pname].d_id
	minetest.chat_send_player(dname, "[NPC "..tostring(n_id)..": "..
		tostring(pname).."] <"..tostring(d_id).." "..tostring(o_id)..
		"> "..tostring(text))
end


-- a chat command for entering and leaving debug mode; needs to be a chat command
-- because the player may have wandered off from his NPC and get too many messages
-- without a quick way to get rid of them otherwise
minetest.register_chatcommand( 'npc_talk_debug', {
	description = "Sets you as debugger for the yl_speak_up-NPC with the ID <n_id>.\n"..
		"  <list> lists the NPC you are currently debugging.\n"..
		"  <off> turns debug mode off again.",
	privs = {npc_talk_owner},
	func = function(pname, param)
		if(param and param == "off") then
			local count = 0
			for k, v in pairs(yl_speak_up.debug_mode_set_by_player) do
				if(v and v == pname) then
					yl_speak_up.debug_mode_set_by_player[ k ] = nil
					count = count + 1
					minetest.chat_send_player(pname, "You are no longer "..
						"debugging the NPC with the ID "..tostring(k)..".")
				end
			end
			minetest.chat_send_player(pname, "Removed you as debugger of "..
				tostring(count).." NPCs.")
			return
		elseif(not(param) or param == "" or param == "list") then
			local count = 0
			local text = "You are currently debugging the NPCs with the following IDs:\n"
			for k, v in pairs(yl_speak_up.debug_mode_set_by_player) do
				if(v and v == pname) then
					count = count + 1
					text = text.."  "..tostring(k)
				end
			end
			if(count == 0) then
				text = text.." - none -"
			else
				text = text.."\nTo turn debugging off, call this command with the "..
					"parameter <off>."
			end
			minetest.chat_send_player(pname, text)
			return
		elseif(not(yl_speak_up.may_edit_npc(minetest.get_player_by_name(pname), param))) then
			minetest.chat_send_player(pname, "You do not have the necessary privs to "..
				"edit that NPC.")
			return
		else
			yl_speak_up.debug_mode_set_by_player[ param ] = pname
			minetest.chat_send_player(pname, "You are now receiving debug information "..
				"for NPC "..tostring(param)..".\nTo turn that off, type "..
				"\"/npc_talk_debug off\".")
		end
	end
});


-- evaluate those preconditions of type "function" (set by the staff)
-- and execute those effects/results of type "function" (set by the staff)
-- WARNING: This is extremly powerful!
--          The code is taken out of the function
--              calculate_displayable_options(..)
--          (written by AliasAlreadyTaken).
-- It requires the npc_master priv to add or edit this prereq.
-- The function is called by
--   * yl_speak_up.eval_precondition and
--   * yl_speak_up.eval_effect.
yl_speak_up.eval_and_execute_function = function(player, x_v, id_prefix)
	local pname = player:get_player_name()

        --minetest.chat_send_all("this is in a single prereq or effect: "..dump(x_v))
        local x_id = x_v[ id_prefix.. "id" ]
        if x_v[ id_prefix.."type" ] ~= "function" then
		return true
	end

        local code = x_v[ id_prefix.."value" ]
        if code:byte(1) == 27 then
            local obj = yl_speak_up.speak_to[pname].obj
            local n_id = yl_speak_up.speak_to[pname].n_id
            local npc = yl_speak_up.get_number_from_id(n_id)
            if obj:get_luaentity() and tonumber(npc) then
                minetest.log("error","[MOD] yl_speak_up: NPC with ID n_"..npc.." at position "..minetest.pos_to_string(obj:get_pos(),0).." could not compile the content of "..x_id.." :"..dump(code) .. " because of illegal bytecode for player "..pname)
            else
                minetest.log("error","[MOD] yl_speak_up: NPC with ID unknown could not compile the content of "..x_id.." :"..dump(code) .. " for player unknown because of illegal bytecode")
            end
        end

	local param = "playername"
	if( id_prefix == "r_") then
		param = "player"
	end
        local f, msg = loadstring("return function("..param..") " .. code .. " end")

        if not f then
            local obj = yl_speak_up.speak_to[pname].obj
            local n_id = yl_speak_up.speak_to[pname].n_id
            local npc = yl_speak_up.get_number_from_id(n_id)
            if obj:get_luaentity() and tonumber(npc) then
                minetest.log("error","[MOD] yl_speak_up: NPC with ID n_"..npc.." at position "..minetest.pos_to_string(obj:get_pos(),0).." could not compile the content of "..x_id.." :"..dump(code) .. " for player "..pname)
            else
                minetest.log("error","[MOD] yl_speak_up: NPC with ID unknown could not compile the content of "..x_id.." :"..dump(code) .. " for player unknown")
            end
        else
            local func = f()

            local ok, ret = pcall(func,pname)

            if not ok then
                local obj = yl_speak_up.speak_to[pname].obj
                local n_id = yl_speak_up.speak_to[pname].n_id
                local npc = yl_speak_up.get_number_from_id(n_id)
                if obj:get_luaentity() and tonumber(npc) then
                    minetest.log("error","[MOD] yl_speak_up: NPC with ID n_"..npc.." at position "..minetest.pos_to_string(obj:get_pos(),0).." could not execute the content of "..x_id.." :"..dump(code) .. " for player "..pname)
                else
                    minetest.log("error","[MOD] yl_speak_up: NPC with ID unknown could not execute the content of "..x_id.." :"..dump(code) .. " for player unknown")
                end
            end

            if type(ret) == "boolean" then
                return ret
            end
        end
	-- fallback
	return false
end


-- These two functions
--   * yl_speak_up.input_fs_edit_option_related and
--   * yl_speak_up.get_fs_edit_option_related
-- are very similar for preconditions and effects. Therefore they're called here
-- with a lot of parameters. fs_edit_preconditions.lua and fs_edit_effects.lua
-- contain only wrappers.

yl_speak_up.input_fs_edit_option_related = function(player, formname, fields,
		id_prefix, element_list_name, max_entries_allowed,
		element_desc, tmp_data_cache,
		text_ask_for_punching,
		values_what, values_operator, values_block, values_trade, values_inv,
		check_what, check_operator, check_block, check_trade, check_inv,
		get_sorted_player_var_list_function,
		formspec_input_to
		)
	if(not(player)) then
		return
	end
	local pname = player:get_player_name()
	-- what are we talking about?
	local n_id = yl_speak_up.speak_to[pname].n_id
	local d_id = yl_speak_up.speak_to[pname].d_id
	local o_id = yl_speak_up.speak_to[pname].o_id
	local x_id = yl_speak_up.speak_to[pname][ id_prefix.."id"]

	-- this only works in edit mode
	if(not(n_id) or yl_speak_up.edit_mode[pname] ~= n_id) then
		return
	end

	if(fields.back_from_cannot_be_edited) then
		yl_speak_up.show_fs(player, formspec_input_to, x_id)
		return
	end

	-- delete precondition
	if(fields.delete_element) then
		local dialog = yl_speak_up.speak_to[pname].dialog
		if(dialog and dialog.n_dialogs
		  and x_id
		  and dialog.n_dialogs[d_id]
		  and dialog.n_dialogs[d_id].d_options
		  and dialog.n_dialogs[d_id].d_options[o_id]) then
			local old_elem = dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ][ x_id ]
			if(id_prefix == "r_" and old_elem.r_type == "dialog") then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2]"..
					"label[0.2,0.5;Effects of the type \"dialog\" cannot be deleted.\n"..
					"Use the edit options or dialog menu to change the target dialog.]"..
					"button[1.5,1.5;2,0.9;back_from_cannot_be_edited;Back]"})
				return
			end
			-- actually delete the element
			dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ][ x_id ] = nil
			-- record this as a change, but do not save do disk yet
			table.insert(yl_speak_up.npc_was_changed[ n_id ],
				"Dialog "..tostring(d_id)..": "..element_desc.." "..tostring( x_id )..
				" deleted for option "..tostring(o_id)..".")
			-- TODO: when trying to save: save to disk as well?
			-- show the new/changed element
			-- go back to the edit option dialog (after all we just deleted the prerequirement)
			yl_speak_up.show_fs(player, "msg", {
				input_to = "yl_speak_up:"..formspec_input_to,
				formspec = "size[6,2]"..
					"label[0.2,0.5;"..element_desc.." \""..
					minetest.formspec_escape(tostring( x_id ))..
					"\" has been deleted.]"..
					"button[1.5,1.5;2,0.9;back_from_delete_element;Back]"})
			return
		end
	end

	if(fields.select_block_pos) then
		minetest.chat_send_player(pname, text_ask_for_punching)
		-- this formspec expects the block punch:
		yl_speak_up.speak_to[pname].expect_block_punch = formspec_input_to
		return
	end

	-- field inputs: those do not trigger a sending of the formspec on their own

	local was_changed = false
	-- are we talking about an inventory?
	-- (inventory only applies to preconditions; not effects)
	local data = yl_speak_up.speak_to[pname][ tmp_data_cache ]
	if(((fields.inv_stack_name and fields.inv_stack_name ~= "")
	  or (fields.store_item_name and fields.store_item_name ~= ""))
	  and data and data.what
	  and ((id_prefix == "p_" and data.what >= 5 and data.what <= 6)
	    -- "give item (created out of thin air) to player (requires npc_master priv)", -- 7
	    -- "take item from player and destroy it (requires npc_master priv)", -- 8
	    or (id_prefix == "r_" and data.what >= 7 and data.what <= 8))) then
		local wanted = ""
		local wanted_name = ""
		if(not(fields.store_item_name)) then
			local parts = fields.inv_stack_name:split(" ")
			local size = 1
			if(parts and #parts > 1) then
				size = tonumber(parts[2])
				if(not(size) or size < 1) then
					size = 1
				end
			end
			wanted = parts[1].." "..tostring(size)
			wanted_name = parts[1]
		else
			local trade_inv = minetest.get_inventory({type="detached",
						name="yl_speak_up_player_"..pname})
			if(not(trade_inv) or trade_inv:is_empty("npc_wants", 1)) then
				-- show error message
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[8,2]"..
						"label[0.2,0.0;Please put an item(stack) into the slot "..
							"next to the\n\"Store\" button first!]"..
						"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
				return
			end
			local stack = trade_inv:get_stack("npc_wants", 1)
			wanted = stack:get_name().." "..stack:get_count()
			wanted_name = stack:get_name()
		end
		-- does the item exist?
		if(minetest.registered_items[ wanted_name ]) then
			data.inv_stack_name = wanted
			fields.inv_stack_name = wanted
		else
			-- show error message
			yl_speak_up.show_fs(player, "msg", {
				input_to = "yl_speak_up:"..formspec_input_to,
				formspec = "size[8,2]"..
					"label[0.2,0.5;Error: \""..
					minetest.formspec_escape(wanted)..
					"\" is not a valid item(stack).]"..
					"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
			return
		end

	-- comparison value for a variable (same for both preconditions and effects)
	elseif(fields.var_cmp_value
	  and data and data.what and data.what == 2 and id_prefix ~= "a_") then
		data.var_cmp_value = fields.var_cmp_value
		was_changed = true

	-- text for a chat message
	elseif(fields.chat_msg_text
	  and data and data.what and data.what == 6 and id_prefix == "r_") then
		data.chat_msg_text = fields.chat_msg_text
		was_changed = true

	elseif(fields.custom_param
	  and fields.custom_param ~= "- Insert a text that is passed on to your function here -"
	  and fields.custom_param ~= ""
	  and data and data.what and data.what == 7 and id_prefix == "a_") then
		data.custom_param = fields.custom_param
		was_changed = true

	elseif(fields.action_item_quest_id
	  and fields.action_item_quest_id ~= ""
	  and fields.action_item_quest_id ~= "- none set -"
	  and data and data.what and data.what == 4 and id_prefix == "a_") then
		data.item_quest_id = fields.action_item_quest_id
		was_changed = true
	end
	-- action_item_quest_id and action_item_desc can be set at the same time
	if(fields.action_item_desc
	  and fields.action_item_desc ~= ""
	  and fields.action_item_desc ~= "- no item set -"
	  and data and data.what and data.what == 4 and id_prefix == "a_") then
		-- TODO: check if it diffrent from the default one of the stack
		data.item_desc = fields.action_item_desc
		was_changed = true
	end
	if(fields.quest_question
	  and fields.quest_question ~= ""
	  and data and data.what and data.what == 6 and id_prefix == "a_") then
		data.quest_question = fields.quest_question
		was_changed = true
	end
	-- quest question and answer can be given with the same press of the save button
	if(fields.quest_answer
	  and fields.quest_answer ~= "- Insert the correct answer here -"
	  and fields.quest_answer ~= ""
	  and data and data.what and data.what == 6 and id_prefix == "a_") then
		data.quest_answer = fields.quest_answer
		was_changed = true
	end

	-- "move the player to a given position (requires npc_master priv)", -- 9
	if(fields.move_to_x or fields.move_to_y or fields.move_to_z) then
		local dimension = {"x","y","z"}
		for i, dim in ipairs(dimension) do
			local text = fields["move_to_"..dim]
			if(text and text ~= "") then
				local val = tonumber(text)
				if(not(val) or val < -32000 or val > 32000) then
					yl_speak_up.show_fs(player, "msg", {
						input_to = "yl_speak_up:"..formspec_input_to,
						formspec = "size[9,2]"..
							"label[0.2,0.5;Error: The coordinate values have "..
								"be in the range of -32000..32000.]"..
							"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
					return
				else
					data[ "move_to_"..dim ] = val
				end
			end
		end
	end

	-- the save button was pressed
	if(fields.save_element and data and data.what and values_what[ data.what ]) then
		-- for creating the new prerequirement; normal elements: p_type, p_value, p_id
		local v = {}
		-- determine p_type
		v[ id_prefix.."type" ] = values_what[ data.what ]

		local dialog = yl_speak_up.speak_to[pname].dialog
		if(not(dialog) or not(dialog.n_dialogs)
		  or not(dialog.n_dialogs[d_id])
		  or not(dialog.n_dialogs[d_id].d_options)
		  or not(dialog.n_dialogs[d_id].d_options[o_id])) then
			-- this really should not happen during the normal course of operation
			-- (only if the player sends forged formspec data or a bug occoured)
			minetest.chat_send_player(pname, "Dialog or option does not exist.")
			return
		end
		local elements = dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ]
		if(not(elements)) then
			dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ] = {}
			elements = dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ]
			x_id = "new"
		end
		-- set x_id appropriately
		if(not(x_id) or x_id == "new") then
			x_id = id_prefix..yl_speak_up.find_next_id(elements)
		end
		v[ id_prefix.."id" ] = x_id

		-- if needed: show a message after successful save so that the player can take
		-- his items back from the trade_inv slots
		local show_save_msg = nil
		local sorted_key_list = yl_speak_up.sort_keys(elements)
		if( x_id == "new" and #sorted_key_list >= max_entries_allowed) then
			-- this really should not happen during the normal course of operation
			-- (only if the player sends forged formspec data or a bug occoured)
			minetest.chat_send_player(pname, "Maximum number of allowed entries exceeded.")
			return
		end
		-- "an internal state (i.e. of a quest)", -- 2
		if(data.what == 2 and id_prefix ~= "a_") then
			v[ id_prefix.."value" ] = "expression"
			v[ id_prefix.."operator" ] = values_operator[ data.operator ]
			v[ id_prefix.."var_cmp_value" ] = (data.var_cmp_value or "")
			v[ id_prefix.."variable" ] = data.variable_name

		-- "a block somewhere", -- 3
		elseif(data.what == 3 and id_prefix ~= "a_") then
			v[ id_prefix.."value" ] = values_block[ data.block ]
			if(not(data.block_pos) or not(data.node_data) or not(data.node_data.name)) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[8,2]"..
						"label[0.2,0.5;Error: Please select a block first!]"..
						"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
				return
			end
			-- for "node_is_air", there is no need to store node name and parameter
			if(v[ id_prefix.."value" ]
			  and (v[ id_prefix.."value" ] == "node_is_like"
			    or v[ id_prefix.."value" ] == "node_is_diffrent_from")
			    or v[ id_prefix.."value" ] == "place"
			    or v[ id_prefix.."value" ] == "dig"
			    or v[ id_prefix.."value" ] == "punch"
			    or v[ id_prefix.."value" ] == "right-click") then
				v[ id_prefix.."node" ]   = data.node_data.name
				v[ id_prefix.."param2" ] = data.node_data.param2
			end
			-- preconditions can be applied to all blocks; effects may be more limited
			if(id_prefix == "r_"
			  and yl_speak_up.check_blacklisted(v[id_prefix.."value"],
					-- we don't know yet which node will be there later on
					data.node_data.name, data.node_data.name)) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[8,2]"..
						"label[0.2,0.5;Error: Blocks of type \""..
						tostring(data.node_data.name).."\" do not allow\n"..
						"interaction of type \""..tostring(v[id_prefix.."value"])..
						"\" for NPC.]"..
						"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
				return
			end
			-- we also need to store the position of the node
			v[ id_prefix.."pos" ] = {x = data.block_pos.x, y = data.block_pos.y, z = data.block_pos.z }
			-- "I can't punch it. The block is as the block *above* the one I punched.",
			if(id_prefix == "p_" and data.block == 5) then
				v.p_pos.y = v.p_pos.y + 1
			end

		-- "a trade", -- 4
		-- (only for preconditions; not for effects)
		elseif(data.what == 4 and id_prefix == "p_") then
			-- this depends on the trade associated with that option; therefore,
			-- it does not need any more parameters (they come dynamicly from the
			-- trade)
			v.p_value = values_trade[ data.trade ]

		-- "the inventory of the player", -- 5
		-- "the inventory of the NPC", -- 6
		-- (only for preconditions; not for effects)
		elseif((data.what == 5 or data.what == 6) and id_prefix == "p_") then
			v.p_value = values_inv[ data.inv ]
			if(v.p_value and v.p_value ~= "inv_is_empty") then
				-- we have checked this value earlier on
				v[ "p_itemstack" ] = data.inv_stack_name
			end

		-- "give item (created out of thin air) to player (requires npc_master priv)", -- 7
		-- "take item from player and destroy it (requires npc_master priv)", -- 8
		elseif(data.what and id_prefix == "r_" and (data.what == 7 or data.what == 8)) then
			if(not(data.inv_stack_name) or data.inv_stack_name == "") then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[8,2]"..
						"label[0.2,0.5;Error: Please provide the name of the "..
							"\nitem you want to give or take!]"..
						"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
				return
			end
			if(not(minetest.check_player_privs(player, {npc_master=true}))) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2]"..
						"label[0.2,0.5;Error: You need the \"npc_master\" priv "..
							" in order to set this effect.]"..
						"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
				return
			end
			v[ "r_value" ] = data.inv_stack_name


		-- "move the player to a given position (requires npc_master priv)", -- 9
		elseif(data.what and id_prefix == "r_" and data.what == 9) then
			if(not(data.move_to_x) or not(data.move_to_y) or not(data.move_to_z)) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2]"..
						"label[0.2,0.5;Error: Please provide valid coordinates "..
							" x, y and z!]"..
						"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
				return
			end
			if(not(minetest.check_player_privs(player, {npc_master=true}))) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2]"..
						"label[0.2,0.5;Error: You need the \"npc_master\" priv "..
							" in order to set this effect.]"..
						"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
				return
			end
			v[ "r_value" ] = minetest.pos_to_string(
				{x = data.move_to_x, y = data.move_to_y, z = data.move_to_z})


		-- "NPC crafts something", -- 4
		-- (only for effects; not for preconditions)
		elseif(data.what and id_prefix == "r_" and data.what == 4) then
			local player_inv = player:get_inventory()
			if(player_inv:get_stack("craftpreview", 1):is_empty()) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[8,2]"..
						"label[0.2,0.5;Error: Please prepare your craft grid first!"..
							"\nYour NPC needs to know what to craft.]"..
						"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
				return
			end
			-- store the craft result (Note: the craft result may change in the future
			-- if the server changes its craft result, making this craft invalid)
			v[ "r_value" ] = player_inv:get_stack("craftpreview", 1):to_string()
			v[ "r_craft_grid"] = {}
			for i = 1, 9 do
				-- store all the indigrents of the craft grid
				table.insert( v[ "r_craft_grid" ],
					player_inv:get_stack("craft", i):to_string())
			end

		-- "go to other dialog if the *previous* effect failed", -- 5
		-- (only for effects; not for preconditions)
		elseif(data.what and id_prefix == "r_" and data.what == 5) then
			v[ "r_value" ] = data.on_failure

		-- "send a chat message to all players", -- 6
		-- (only for effects; not for preconditions)
		elseif(data.what and id_prefix == "r_" and data.what == 6) then
			data.chat_msg_text = fields.chat_msg_text
			-- allow saving only if the placeholders are all present
			-- (reason for requiring them: players and server owners ought to
			-- be able to see who is responsible for a message)
			if(not(string.find(data.chat_msg_text, "%$NPC_NAME%$"))
			  or not(string.find(data.chat_msg_text, "%$PLAYER_NAME%$"))
			  or not(string.find(data.chat_msg_text, "%$OWNER_NAME%$"))) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;Error: Your chat message needs to contain "..
							"the following\nplaceholders: $NPC_NAME$, "..
							"$PLAYER_NAME$ and $OWNER_NAME$.\nThat way, other "..
							"players will know who sent the message.]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			v[ "r_value" ] = data.chat_msg_text

		-- "Normal trade - one item(stack) for another item(stack).", -- 3
		-- (only for actions)
		elseif(data.what and id_prefix == "a_" and data.what == 3) then
			-- remember which option was selected
			yl_speak_up.speak_to[pname].o_id = o_id
			-- do not switch target dialog (we are in edit mode)
			yl_speak_up.speak_to[pname].target_d_id = nil
			-- just to make sure that the trade_id is properly set...
			if(not(data.trade_id)) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;Error: Missing trade ID.]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			-- the button is called store_trade_simple instead of save_element in
			-- the trade simple function(s); we want to store a trade
			fields.store_trade_simple = true
			local res = yl_speak_up.input_add_trade_simple(player, "", fields)
			-- the above function sets:
			--    dialog.trades[ trade_id ] = {pay={ps},buy={bs}, d_id = d_id, o_id = o_id}
			-- store the trade as an action:
			local dialog = yl_speak_up.speak_to[pname].dialog
			if(res and dialog.trades and dialog.trades[ data.trade_id ]) then
				v[ "a_value" ] = data.trade_id
				v[ "a_pay"   ] = dialog.trades[ data.trade_id ].pay
				v[ "a_buy"   ] = dialog.trades[ data.trade_id ].buy
				v[ "a_on_failure" ] = ""
				if(data.action_failure_dialog) then
					local dialog = yl_speak_up.speak_to[pname].dialog
					local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
					v[ "a_on_failure" ] = sorted_dialog_list[ data.action_failure_dialog ]
				end
			end

		-- "The NPC gives something to the player (i.e. a quest item).", -- 4
		-- "The player is expected to give something to the NPC (i.e. a quest item).", -- 5
		-- (only for actions)
		elseif(data.what and id_prefix == "a_" and (data.what == 4 or data.what == 5)) then
			local trade_inv_list = "npc_gives"
			if(data.what == 5) then
				trade_inv_list = "npc_wants"
			end
			local trade_inv = minetest.get_inventory({type="detached", name="yl_speak_up_player_"..pname})
			if(not(trade_inv) or trade_inv:is_empty( trade_inv_list )) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;Please insert an item first! Your NPC"..
							"needs\nto know what it shall give to the player.]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			v[ "a_on_failure" ] = ""
			if(data.action_failure_dialog) then
				local dialog = yl_speak_up.speak_to[pname].dialog
				local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
				v[ "a_on_failure" ] = sorted_dialog_list[ data.action_failure_dialog ]
			end
			-- change the node in the slot
			local stack = trade_inv:get_stack( trade_inv_list, 1)
			if(not(stack) or not(minetest.registered_items[ stack:get_name() ])) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;This item is unkown. Please use only known"..
							"items.]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			-- is this particular item blacklisted on this server?
			if(yl_speak_up.blacklist_action_quest_item[ stack:get_name() ]) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;Sorry. This item is blacklisted on this "..
							"server.\nYou can't use it as a quest item.]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			local meta = stack:get_meta()
			-- what does the NPC want to give?
			v[ "a_value" ] = stack:get_name().." "..stack:get_count()
			-- for displaying as a background image
			data.item_string = v[ "a_value" ]
			if(data.what == 5) then
				-- try to reconstruct $PLAYER_NAME$ (may not always work)
				local item_was_for = meta:get_string("yl_speak_up:quest_item_for")
				local new_desc = meta:get_string("description")
				if(item_was_for and item_was_for ~= "") then
					new_desc = string.gsub(new_desc, item_was_for, "$PLAYER_NAME$")
				end
				data.item_desc = new_desc
			end
			-- set new description if there is one set (optional)
			if(data.item_desc
			  and data.item_desc ~= ""
			  and data.item_desc ~= "- none set -") then
				if(data.what == 4) then
					meta:set_string("description", data.item_desc)
				end
				v[ "a_item_desc" ] = data.item_desc
			end
			if(data.what == 5) then
				data.item_quest_id = meta:get_string("yl_speak_up:quest_id")
			end
			-- set special ID (optional)
			if(data.item_quest_id
			  and data.item_quest_id ~= ""
			  and data.item_quest_id ~= "- no item set -") then
				if(data.what == 4) then
					-- which player got this quest item?
					meta:set_string("yl_speak_up:quest_item_for", pname)
					-- include the NPC id so that we know which NPC gave it
					meta:set_string("yl_speak_up:quest_item_from", tostring(n_id))
					-- extend quest_id by NPC id so that it becomes more uniq
					meta:set_string("yl_speak_up:quest_id",
						tostring(n_id).." "..tostring(data.item_quest_id))
				end
				v[ "a_item_quest_id" ] = data.item_quest_id
			end
			if( v["a_item_quest_id"] and not(v[ "a_item_desc"]) and data.what == 4) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;You can't set a special quest ID without "..
						"also changing\nthe description. The player would be "..
						"unable to tell\nthe quest item and normal items "..
						"apartapart.]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			local player_inv = player:get_inventory()
			if(not(player_inv:room_for_item("main", stack))) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;You have no room in your inventory for "..
						"the example\nitem. Please make room so that it can be"..
						"given back to you!]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			player_inv:add_item("main", stack)
			trade_inv:remove_item(trade_inv_list, stack)
			-- just send a message that the save was successful and give the player time to
			-- take his items back
			show_save_msg = "size[9,2.5]"..
				"label[0.2,0.5;The information was saved successfully.\n"..
					"The item has been returned to your inventory.]"..
				"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"

		-- "The player has to manually enter a password or passphrase or some other text.", -- 6
		elseif(data.what and id_prefix == "a_" and data.what == 6) then
			if(not(data.quest_question)) then
				data.quest_question = "Your answer:"
			end
			v[ "a_question" ] = data.quest_question
			-- the player setting this up needs to provide the correct answer
			if(not(data.quest_answer)) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;Error: Please provide the correct answer!\n"..
						"The answer the player gives is checked against this.]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			v[ "a_value" ] = data.quest_answer
			if(not(data.action_failure_dialog)) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = "size[9,2.5]"..
						"label[0.2,0.5;Error: Please provide a target dialog if "..
						"the player gives the wrong answer.]"..
						"button[1.5,2.0;2,0.9;back_from_error_msg;Back]"})
				return
			end
			local dialog = yl_speak_up.speak_to[pname].dialog
			local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
			v[ "a_on_failure" ] = sorted_dialog_list[ data.action_failure_dialog ]

		-- "Call custom functions that are supposed to be overridden by the server.", -- 7
		elseif(data.what and id_prefix == "a_" and data.what == 7) then
			v[ "a_value" ] = data.custom_param
			local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
			v[ "a_on_failure" ] = sorted_dialog_list[ data.action_failure_dialog ]
		end

		-- only save if something was actually selected
		if(v[ id_prefix.."value"]) then
			if(not(dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ])) then
				dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ] = {}
			end
			-- store the change in the dialog
			dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ][ x_id ] = v
			-- clear up data
			yl_speak_up.speak_to[pname][ id_prefix.."id" ] = nil
			yl_speak_up.speak_to[pname][ tmp_data_cache ] = nil
			-- record this as a change, but do not save do disk yet
			table.insert(yl_speak_up.npc_was_changed[ n_id ],
				"Dialog "..tostring(d_id)..": "..element_desc.." "..tostring(x_id)..
				" added/changed for option "..tostring(o_id)..".")
			if(show_save_msg) then
				yl_speak_up.show_fs(player, "msg", {
					input_to = "yl_speak_up:"..formspec_input_to,
					formspec = show_save_msg})
				return
			end
			-- TODO: when trying to save: save to disk as well?
			-- show the new/changed precondition
			yl_speak_up.show_fs(player, formspec_input_to, x_id)
			return
		end
	end

	-- selections in a dropdown menu (they trigger sending the formspec)

	-- select a general direction/type first
	-- but *not* when enter was pressed (enter sends them all)
	if(fields.select_what and not(fields.key_enter) and not(fields.store_item_name)) then
		local nr = table.indexof(check_what, fields.select_what)
		yl_speak_up.speak_to[pname][ tmp_data_cache ] = { what = nr }
	end
	-- select a subtype for the "a trade" selection
	if(fields.select_trade) then
		local nr = table.indexof(check_trade, fields.select_trade)
		yl_speak_up.speak_to[pname][ tmp_data_cache ].trade = nr
	end
	-- select a subtype for the inventory selection (player or NPC)
	if(fields.select_inv) then
		local nr = table.indexof(check_inv, fields.select_inv)
		yl_speak_up.speak_to[pname][ tmp_data_cache ].inv = nr
	end
	-- select data regarding a block
	if(fields.select_block) then
		local nr = table.indexof(check_block, fields.select_block)
		yl_speak_up.speak_to[pname][ tmp_data_cache ].block = nr
	end
	-- select data regarding a variable
	if(fields.select_variable) then
		-- get the list of available variables (with the same elements
		-- and the same sort order as when the dropdown was displayed)
		local var_list = get_sorted_player_var_list_function(pname)
		local nr = table.indexof(var_list, fields.select_variable)
		if(nr) then
			yl_speak_up.speak_to[pname][ tmp_data_cache ].variable = nr
			yl_speak_up.speak_to[pname][ tmp_data_cache ].variable_name = var_list[ nr ]
		end
	end
	-- select data regarding an operator
	if(fields.select_operator) then
		local nr = table.indexof(check_operator, fields.select_operator)
		yl_speak_up.speak_to[pname][ tmp_data_cache ].operator = nr
	end
	if(fields.select_on_failure) then
		-- in this case we really want the name of the target dialog
		yl_speak_up.speak_to[pname][ tmp_data_cache ].on_failure = fields.select_on_failure
	end
	if(fields.select_on_action_failure
	  and data and data.what and id_prefix == "a_") then
		local dialog = yl_speak_up.speak_to[pname].dialog
		local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
		local nr = table.indexof(sorted_dialog_list, fields.select_on_action_failure)
		yl_speak_up.speak_to[pname][ tmp_data_cache ].action_failure_dialog = nr
	end

	-- new variables have to be added (and deleted) somewhere after all
	if(fields.manage_variables) then
		-- remember which formspec we are comming from
		yl_speak_up.speak_to[pname][ "working_at" ] = formspec_input_to
		yl_speak_up.show_fs(player, "manage_variables")
		return
	end

	-- the player wants to change/edit a precondition or effect
	if(not(fields.back)
	  and (fields.change_element or fields.select_what or fields.select_trade
	  or fields.select_inv or fields.select_block
	  or fields.select_variable or fields.select_operator
	  or fields.select_on_failure
	  or fields.select_on_action_failure
	  or fields.back_from_error_msg
	  or fields.store_item_name
	  or was_changed
	  or fields.key_enter
	  or fields.quit
	  -- return was pressed
	  or fields.key_enter_field)) then
		yl_speak_up.show_fs(player, formspec_input_to)
		return
	end

	-- go back to the edit option dialog
	yl_speak_up.show_fs(player, "edit_option_dialog",
		{n_id = n_id, d_id = d_id, o_id = o_id, caller= formspec_input_to})
end


yl_speak_up.get_fs_edit_option_related = function(player, table_click_result,
		id_prefix, element_list_name, max_entries_allowed,
		element_desc, tmp_data_cache,
		what_do_you_want_txt,
		values_what, values_operator, values_block, values_trade, values_inv,
		check_what, check_operator, check_block, check_trade, check_inv,
		get_sorted_player_var_list_function,
		show_element_function,
		table_of_name,
		text_variable, text_select_operator, text_select_value,
		text_block_position)
	if(not(player)) then
		return ""
	end
	local pname = player:get_player_name()
	-- what are we talking about?
	local n_id = yl_speak_up.speak_to[pname].n_id
	local d_id = yl_speak_up.speak_to[pname].d_id
	local o_id = yl_speak_up.speak_to[pname].o_id
	local x_id = yl_speak_up.speak_to[pname][ id_prefix.."id" ]

	-- this only works in edit mode
	if(not(n_id) or yl_speak_up.edit_mode[pname] ~= n_id) then
		return "size[1,1]label[0,0;You cannot edit this NPC.]"
	end

	local dialog = yl_speak_up.speak_to[pname].dialog
	if(not(dialog) or not(dialog.n_dialogs)
	  or not(dialog.n_dialogs[d_id])
	  or not(dialog.n_dialogs[d_id].d_options)
	  or not(dialog.n_dialogs[d_id].d_options[o_id])) then
		return "size[4,1]label[0,0;Dialog option does not exist.]"
	end

	local elements = dialog.n_dialogs[d_id].d_options[o_id][ element_list_name ]
	if(not(elements)) then
		elements = {}
	end

	-- did we arrive here through clicking on an element in the dialog edit options menu?
	if(table_click_result or elements[ table_click_result ]) then
		if(not(elements[ table_click_result ])) then
			-- which element has the player selected?
			local sorted_key_list = yl_speak_up.sort_keys(elements)
			local selected = minetest.explode_table_event(table_click_result)
			-- use "new" if nothing fits
			x_id = "new"
			if((selected.type == "CHG" or selected.type == "DLC")
			  and selected.row <= #sorted_key_list) then
				x_id = sorted_key_list[ selected.row ]
			end

			if( x_id == "new" and #sorted_key_list >= max_entries_allowed) then
				return "size[9,1.5]"..
					"label[0.2,0.0;There are only up to "..
						minetest.formspec_escape(yl_speak_up.max_result_effects)..
						" "..element_desc.."s allowed per dialog option.]"..
						"button[2.0,0.8;1.0,0.9;back;Back]"
			end
		else
			-- allow to directly specify a x_id to show
			x_id = table_click_result
		end

		-- store which element we are talking about
		yl_speak_up.speak_to[pname][ id_prefix.."id" ] = x_id
		-- nothing selected yet
		yl_speak_up.speak_to[pname][ tmp_data_cache ] = nil
		-- display the selected element
		if(x_id ~= "new") then
			return "formspec_version[3]"..
				"size[20,3]"..
				"bgcolor[#00000000;false]"..
				"label[0.2,0.5;Selected "..element_desc..":]"..
				"tablecolumns[text;color,span=1;text;text]"..
				"table[0.2,0.8;19.6,0.7;"..table_of_name..";"..
					minetest.formspec_escape(elements[ x_id ][ id_prefix.."id"])..
						",#FFFF00,"..
					minetest.formspec_escape(elements[ x_id ][ id_prefix.."type"])..
						","..
					minetest.formspec_escape(
						show_element_function(elements[ x_id ]))..";0]"..
				"button[2.0,1.8;1.5,0.9;delete_element;Delete]"..
				"button[4.0,1.8;1.5,0.9;change_element;Change]"..
				"button[6.0,1.8;5.5,0.9;back;Back to edit dialog option \""..
					tostring(o_id).."\"]"
		end
	end

	-- did the player get here through punching a block in the meantime?
	local block_pos = yl_speak_up.speak_to[pname].block_punched
	yl_speak_up.speak_to[pname].block_punched = nil

	local data = yl_speak_up.speak_to[pname][ tmp_data_cache ]
	if(not(data) or not(data.what)) then
		data = { what = 1}
	end
	-- fallback
	if(not(x_id)) then
		x_id = "new"
	end

	-- does the element exist already? if so: use the existing values as presets for data
	-- (so that the element can be edited)
	-- does kind of the opposite than the saving of values starting in line 323 of this file
	if(x_id ~= "new" and data.what == 1 and elements[ x_id ]) then
		local e = elements[ x_id ]
		if( id_prefix == "r_" and e[ "r_type" ] == "dialog") then
			-- dialog effects cannot be edited this way
			return "size[9,2]"..
				"label[0.2,0.5;Effects of the type \"dialog\" cannot be edited this way.\n"..
				"Use the edit options or dialog menu to change the target dialog.]"..
				"button[1.5,1.5;2,0.9;back_from_cannot_be_edited;Back]"
		end
		if( id_prefix == "p_" and e[ "p_type" ] == "item") then
			-- the staff-based item precondition can be translated to an editable
			-- inventory precondition which is equal
			e[ "p_type" ] = "player_inv"
			e[ "p_itemstack" ] = e[ "p_value"]
			e[ "p_value" ] = "inv_contains"
		end

		data.what = table.indexof(values_what, e[ id_prefix.."type" ])
		if(data.what == -1) then
			data.what = 1
		-- a state/variable (precondition + effect)
		elseif(data.what == 2 and id_prefix ~= "a_") then
			data.operator = math.max(1,table.indexof(values_operator, e[ id_prefix.."operator" ]))
			data.var_cmp_value = e[ id_prefix.."var_cmp_value" ]
			data.variable_name = e[ id_prefix.."variable" ]
			local var_list = get_sorted_player_var_list_function(pname)
			data.variable = math.max(1, table.indexof(var_list, e[ id_prefix.."variable"])+1)
		-- a block (precondition + effect)
		elseif(data.what == 3 and id_prefix ~= "a_") then
			data.block = math.max(1,table.indexof(values_block, e[ id_prefix.."value" ]))
			data.node_data = {}
			data.node_data.data = e[ id_prefix.."node" ]
			data.node_data.param2 = e[ id_prefix.."param2" ]
			data.block_pos = {x=e[ id_prefix.."pos" ].x,
					  y=e[ id_prefix.."pos" ].y,
					  z=e[ id_prefix.."pos" ].z}
			-- the block below was punched
			if(id_prefix == "p_" and data.block == 5) then
				data.block_pos.y = data.block_pos.y - 1
			end
		-- a trade (precondition)
		elseif(data.what == 4 and id_prefix == "p_") then
			data.trade = math.max(1,table.indexof(values_trade, e[ "p_value" ]))
		-- an invenetory (precondition)
		elseif((data.what == 5 or data.what == 6) and id_prefix == "p_") then
			data.inv = math.max(1,table.indexof(values_inv, e["p_value"]))
			data.inv_stack_name = e[ "p_itemstack" ]
		-- crafting (effect)
		elseif(data.what and id_prefix == "r_" and data.what == 4) then
			-- those items can at least be shown as background images
			data.craftresult = e[ "r_value" ]
			data.craft_grid = e[ "r_craft_grid"]
		-- on failure (effect)
		elseif(data.what and id_prefix == "r_" and data.what == 5) then
			data.on_failure = e[ "r_value" ]
		-- send a chat message (effect)
		elseif(data.what and id_prefix == "r_" and data.what == 6) then
			data.chat_msg_text = e[ "r_value" ]
		-- normal trade (action)
		elseif(data.what and id_prefix == "a_" and data.what == 3) then
			data.trade_id = e[ "a_value" ]
			-- use as background images
			if(dialog and dialog.trades and dialog.trades[ data.trade_id ]) then
				data.pay = dialog.trades[ data.trade_id ].pay[1]
				data.buy = dialog.trades[ data.trade_id ].buy[1]
			end
			local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
			data.action_failure_dialog = math.max(1,
					table.indexof(sorted_dialog_list, e[ "a_on_failure" ]))
		-- npc_gives/npc_wants (action)
		elseif(data.what and id_prefix == "a_" and (data.what == 4 or data.what == 5)) then
			local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
			data.action_failure_dialog = math.max(1,
					table.indexof(sorted_dialog_list, e[ "a_on_failure" ]))
			-- data.item_string is used to show a background image
			data.item_string = e[ "a_value"] -- stack name and count (as string)
			data.item_desc = e[ "a_item_desc" ]
			data.item_quest_id = e[ "a_item_quest_id" ]
			local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
			data.action_failure_dialog = math.max(1,
					table.indexof(sorted_dialog_list, e[ "a_on_failure" ]))
		-- entering password (action)
		elseif(data.what and id_prefix == "a_" and data.what == 6) then
			data.quest_question = e[ "a_question" ]
			data.quest_answer = e[ "a_value" ]
			local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
			data.action_failure_dialog = math.max(1,
					table.indexof(sorted_dialog_list, e[ "a_on_failure" ]))
		-- custom function (action)
		elseif(data.what and id_prefix == "a_" and data.what == 7) then
			data.custom_param = e[ "a_value" ]
			local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
			data.action_failure_dialog = math.max(1,
					table.indexof(sorted_dialog_list, e[ "a_on_failure" ]))

		-- give_item/take_item
		elseif(data.what and id_prefix == "r_" and data.what >= 7 and data.what <= 8) then
			data.inv_stack_name = e[ "r_value" ] or ""

		-- move
		elseif(data.what and id_prefix == "r_" and data.what == 9) then
			if(e[ "r_value"] and type(e[ "r_value" ]) == "string") then
				local pos = minetest.string_to_pos(e[ "r_value" ])
				if(pos) then
					data.move_to_x = pos.x
					data.move_to_y = pos.y
					data.move_to_z = pos.z
				end
			end
                end
		-- write that data back
		yl_speak_up.speak_to[pname][ tmp_data_cache ] = data
	end

	local save_button = "button[5.0,11.8;1,0.7;save_element;Save]"
	local formspec =
		"formspec_version[3]"..
		"size[20,13]"..
		"label[5,0.5;Edit "..element_desc.." \""..minetest.formspec_escape(x_id).."\"]"..
		"label[0.2,1.5;"..what_do_you_want_txt.."]"..
		"label[0.2,2.0;Something regarding...]"..
		"dropdown[4.0,1.8;14.0,0.6;select_what;"..
			table.concat(check_what, ",")..";"..
			tostring(data.what)..";]"..
		"button[3.0,11.8;1,0.7;back;Abort]"

	if(id_prefix ~= "a_") then
		formspec = formspec..
			"label[1,10.5;If you are unsure if your setup of pre(C)onditions and (Ef)fects "..
				"works as intended,\ntype \"/npc_talk_debug "..tostring(n_id).."\" "..
				"in chat in order to enter debug mode. You can leave it with "..
				"\"/npc_talk_debug off\".]"
	end

	-- "an internal state (i.e. of a quest)", -- 2
	-- (state is the second offered option in both preconditions and effects list)
	if(data.what and data.what == 2 and id_prefix ~= "a_") then
		if(not(data.variable) or data.variable < 1) then
			data.variable = 1
			-- not enough selected yet for saving
			save_button = ""
		elseif(not(data.operator) or data.operator == 1) then
			data.operator = 1
			save_button = ""
		end
		local field_for_value = "field[11.2,4.8;7.0,0.6;var_cmp_value;;"..
			minetest.formspec_escape(data.var_cmp_value or "- enter value -").."]"
		-- do not show value input field for unary operators
		-- (unary operators are diffrent for prerequirements and effects)
		if(not(data.operator)
		  or (id_prefix == "p_" and (data.operator == 1 or (data.operator>=8 and data.operator<11)))
		  -- "unset", "set_to_current_time"
		  or (id_prefix == "r_" and (data.operator == 3 or data.operator == 4))) then
			field_for_value = "label[11.2,5.1;- not used for this operator -]"
		end
		-- the list of available variables needs to be extended with the ones
		-- the player has read access to, and the order has to be constant
		-- (because dropdown just returns an index)
		local var_list = get_sorted_player_var_list_function(pname)
		local var_list_text = "- please select -"
		for i, v in ipairs(var_list) do
			local parts = string.split(v, " ")
			local var_name = v
			if(parts and parts[1] and parts[1] == pname) then
				table.remove(parts, 1)
				var_name = table.concat(parts, " ")
			end
			var_list_text = var_list_text..","..minetest.formspec_escape(tostring(var_name))
		end
		formspec = formspec..
			"label[0.2,3.3;"..text_variable.."]"..
			"label[0.2,4.3;Name of variable:]"..
			"dropdown[0.2,4.8;6.5,0.6;select_variable;"..
				var_list_text..";"..
				tostring(data.variable)..";]"..
			"label[7.0,4.3;"..text_select_operator.."]"..
			"dropdown[7.0,4.8;4.0,0.6;select_operator;"..
				table.concat(check_operator, ",")..";"..
				tostring(data.operator)..";]"..
			"label[11.2,4.3;"..text_select_value.."]"..
			field_for_value..
			"button[0.2,6.0;4.0,0.6;manage_variables;Manage variables]"..
			"hypertext[1.2,7.0;16.0,2.5;some_text;<normal>"..
				"<b>Note:</b> Each variable is player-specific and will be set and "..
				"checked for the player that currently talks to your NPC.\n"..
				"<b>Note:</b> You can set a variable to the current time in an effect. "..
				"After that, use a precondition to check if that variable was set \"more "..
				"than x seconds ago\" or \"less than x seconds ago\". This can be "..
				"useful for prevending your NPC from handing out the same quest item again "..
				"too quickly (players are inventive and may use your quest item for their "..
				"own needs).\n</normal>]"

	-- "a block somewhere", -- 3
	-- (block is the third offered option in both preconditions and effects list)
	elseif(data.what and data.what == 3 and id_prefix ~= "a_") then
		local block_pos_str = "- none set -"
		local node = {name = "- unknown -", param2 = "- unkown -"}
		if(not(block_pos) and data and data.block_pos) then
			block_pos = data.block_pos
		end
		local error_is_protected = ""
		if(block_pos) then
			-- store for later usage
			data.block_pos = block_pos
			local tmp_pos = {x=block_pos.x, y=block_pos.y, z=block_pos.z}
			-- "I can't punch it. The block is as the block *above* the one I punched.",
			-- (only valid for preconditions; not for effects - because the player and
			-- his NPC need to be able to build there)
			if(data.block and id_prefix == "p_" and data.block == 5) then
				tmp_pos.y = block_pos.y + 1
			end
			-- effects (and, likewise, preconditions): the player at least has to be able to
			-- build at that position - check that
			if(minetest.is_protected(tmp_pos, pname)) then
				error_is_protected = "label[0.2,7.8;Error: "..
					"The position you punched is protected. It cannot be used by "..
					"your NPC for checks or building. Please select a diffrent block!]"
				block_pos = nil
				data.block_pos = nil
			else
				block_pos_str = minetest.pos_to_string(tmp_pos)
				node = minetest.get_node_or_nil(tmp_pos)
				if(not(node)) then
					node = {name = "- unknown -", param2 = "- unkown -"}
				end
				-- "There shall be air instead of this block.",
				-- (only valid for preconditions)
				if(data.block and id_prefix == "p_" and data.block == 3) then
					node = {name = "air", param2 = 0}
				end
				-- cache that (in case a sapling grows or someone else changes it)
				data.node_data = node
			end
		end
		if(node.name == "- unknown -") then
			save_button = ""
		end
		if(not(data.block) or data.block == 1) then
			data.block = 1
			-- not enough selected yet for saving
			save_button = ""
		end
		formspec = formspec..
			"label[0.2,3.3;"..text_block_position.."]"..
			"dropdown[4.0,3.5;16.0,0.6;select_block;"..
				table.concat(check_block, ",")..";"..
				tostring(data.block)..";]"..
			"label[0.2,4.8;Position of the block:]"..
			"label[4.0,4.8;"..minetest.formspec_escape(block_pos_str).."]"..
			"label[0.2,5.8;Name of block:]"..
			"label[4.0,5.8;"..minetest.formspec_escape(node.name).."]"..
			"label[0.2,6.8;Orientation (param2):]"..
			"label[4.0,6.8;"..minetest.formspec_escape(node.param2).."]"..
			"button_exit[10.0,5.5;4.0,0.7;select_block_pos;Set position of block]"..
			"tooltip[select_block_pos;Click on this button to select a block.\n"..
				"This menu will close and you will be asked to punch\n"..
				"the block at the position you want to check or change.\n"..
				"After punching it, you will be returned to this menu.]"..
			error_is_protected

	-- "a trade", -- 4
	-- (trade - only for preconditions; effects have something else here)
	elseif(data.what and id_prefix == "p_" and data.what == 4) then
		if(not(data.trade) or data.trade == 1) then
			data.trade = 1
			-- not enough selected yet for saving
			save_button = ""
		end
		formspec = formspec..
			"label[0.2,3.3;If the action is a trade, the following shall be true:]"..
			"dropdown[4.0,3.5;16.0,0.6;select_trade;"..
				table.concat(check_trade, ",")..";"..
				tostring(data.trade)..";]"

	-- "the inventory of the player", -- 5
	-- "the inventory of the NPC", -- 6
	-- (inventory - only for preconditions; effects have something else here)
	elseif(data.what and id_prefix == "p_" and data.what >= 5 and data.what <= 6) then
		if(not(data.inv) or data.inv == 1) then
			data.inv = 1
			-- not enough selected yet for saving
			save_button = ""
		end
		formspec = formspec..
			"label[0.2,3.0;The following shall be true about the inventory:]"..
			"dropdown[4.0,3.2;16.0,0.6;select_inv;"..
				table.concat(check_inv, ",")..";"..
				tostring(data.inv)..";]"..
			"label[0.2,4.2;Name of the item(stack):]"..
			"field[4.0,4.0;16.0,0.6;inv_stack_name;;"..(data.inv_stack_name or "").."]"..
			"tooltip[inv_stack_name;Enter name of the block and amount.\n"..
				"Example: \"default:apple 3\" for three apples,\n"..
				"         \"farming:bread\" for a bread.]"..
			"label[0.2,5.7;Or put the item in here\nand click on \"Store\":]"..
			"button[5.5,5.5;1.5,0.9;store_item_name;Store]"..
			"list[detached:yl_speak_up_player_"..pname..";npc_wants;4.0,5.5;1,1;]"..
			"label[8,4.9;Your inventory:]"..
			"list[current_player;main;8,5.3;8,4;]"

	-- "give item (created out of thin air) to player (requires npc_master priv)", -- 7
	-- "take item from player and destroy it (requires npc_master priv)", -- 8
	elseif(data.what and id_prefix == "r_" and (data.what == 7 or data.what == 8)) then
		local text = "The following item shall be created out of thin air and added to the "..
				"player's inventory:"
		if(data.what == 8) then
			text = "The following item shall be removed from the player's inventory and "..
				"be destroyed:"
		end
		formspec = formspec..
			"label[0.2,3.0;"..text.."]"..
			"label[0.2,3.5;Note: You can *save* this effect only if you have the "..
				"\"npc_master\" priv!]"..
			"label[0.2,4.2;Name of the item(stack):]"..
			"field[4.0,4.0;16.0,0.6;inv_stack_name;;"..(data.inv_stack_name or "").."]"..
			"tooltip[inv_stack_name;Enter name of the block and amount.\n"..
				"Example: \"default:apple 3\" for three apples,\n"..
				"         \"farming:bread\" for a bread.]"..
			"label[0.2,5.7;Or put the item in here\nand click on \"Store\":]"..
			"button[5.5,5.5;1.5,0.9;store_item_name;Store]"..
			"list[detached:yl_speak_up_player_"..pname..";npc_wants;4.0,5.5;1,1;]"..
			"label[8,4.9;Your inventory:]"..
			"list[current_player;main;8,5.3;8,4;]"

	-- "move the player to a given position (requires npc_master priv)", -- 9
	elseif(data.what and id_prefix == "r_" and data.what == 9) then
		formspec = formspec..
			"label[0.2,3.0;Move the player to this position:]"..
			"label[0.2,3.5;Note: You can *save* this effect only if you have the "..
				"\"npc_master\" priv!]"..
			"label[0.2,5.3;X:]"..
			"label[3.7,5.3;Y:]"..
			"label[7.2,5.3;Z:]"..
			"field[0.7,5.0;2.0,0.6;move_to_x;;"..(data.move_to_x or "").."]"..
			"field[4.2,5.0;2.0,0.6;move_to_y;;"..(data.move_to_y or "").."]"..
			"field[7.7,5.0;2.0,0.6;move_to_z;;"..(data.move_to_z or "").."]"

	-- "NPC crafts something", -- 4
	-- (craft - only for effects - not for preconditions)
	elseif(data.what and id_prefix == "r_" and data.what == 4) then
		local bg_img = ""
		if(data and data.craftresult and data.craft_grid) then
			bg_img = "item_image[5.95,4.90;0.7,0.7;"..tostring(data.craftresult).."]"
			for i, v in ipairs(data.craft_grid) do
				if(v and v ~= "") then
					bg_img = bg_img.."item_image["..
						tostring(1.15 + ((i-1)%3)*1.25)..","..
						tostring(3.65 + math.floor((i-1)/3)*1.30)..
						";0.7,0.7;"..tostring(v).."]"
				end
			end
		end
		formspec = formspec..
			"label[8,2.6;Your invnetory:]"..
			"list[current_player;main;8,3;8,4;]"..
			"label[1,3.1;Your craft grid:]"..
			"list[current_player;craft;1,3.5;3,3;]"..
			"list[current_player;craftpreview;5.8,4.75;1,1;]"..
			"image[4.6,4.8;1,1;gui_furnace_arrow_bg.png^[transformR270]"..
			"label[1,8.0;Use your craft grid to show your NPC what to craft "..
				"and how. Click on \"Save\" to save.]"..
			bg_img

	-- "go to other dialog if the *previous* effect failed", -- 5
	-- (on_failure - only for effects - not for preconditions)
	elseif(data.what and id_prefix == "r_" and data.what == 5) then
		local dialog = yl_speak_up.speak_to[pname].dialog
		local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
		local nr = 1
		if(not(data) or not(data.on_failure)) then
			save_button = ""
		else
			nr = table.indexof(sorted_dialog_list, data.on_failure)
		end
		local on_failure_dialog = ""
		if(dialog and dialog.n_dialogs and dialog.n_dialogs[ data.on_failure ]) then
			on_failure_dialog =
				"label[0.2,5.5;This will switch to dialog "..tostring(data.on_failure)..":]"..
				"hypertext[1.2,6.0;19.6,2.5;d_text;<normal>"..
				minetest.formspec_escape(dialog.n_dialogs[ data.on_failure ].d_text or "?")..
				"\n</normal>]"
		end
		formspec = formspec..
			"label[0.2,3.3;If the *previous* effect failed,]"..
			"label[0.2,3.8;switch to the following dialog:]"..
			"dropdown[5.0,3.5;6.5,0.6;select_on_failure;"..
				table.concat(sorted_dialog_list, ",")..";"..
				tostring(nr)..";]"..
			on_failure_dialog

	-- "send a chat message to all players" -- 6
	elseif(data.what and id_prefix == "r_" and data.what == 6) then
		local default_text = "$NPC_NAME$ (owned by $OWNER_NAME$) announces: $PLAYER_NAME$ "..
			"- example; please enter the text -"
		if(not(data)) then
			data = {}
		end
		formspec = formspec..
			"label[0.2,3.3;Send the following chat message to *all* players:]"..
			"label[0.2,4.1;Message:]"..
			"field[2.0,3.8;16.0,0.6;chat_msg_text;;"..
				minetest.formspec_escape(
					data.chat_msg_text
					or default_text).."]"..
			"label[0.2,5.3;Note: Your chat message needs to contain the following placeholders,"..
				" which will be replaced automaticly like in dialog texts:"..
				"\n$NPC_NAME$, $PLAYER_NAME$ and $OWNER_NAME$.]"

	-- "Normal trade - one item(stack) for another item(stack).", -- 3
	elseif(data.what and id_prefix == "a_" and data.what == 3) then
		local dialog = yl_speak_up.speak_to[pname].dialog
		local d_id = yl_speak_up.speak_to[pname].d_id
		local o_id = yl_speak_up.speak_to[pname].o_id
		if(not(data.trade_id)) then
			data.trade_id = tostring(d_id).." "..tostring(o_id)
		end
		-- show the player which trade is stored
		local bg_img = ""
		if(data and data.buy and data.pay) then
			bg_img = "item_image[2.15,4.35;0.7,0.7;"..tostring(data.buy).."]"..
				 "item_image[5.15,4.35;0.7,0.7;"..tostring(data.pay).."]"
		end
		yl_speak_up.speak_to[pname].trade_id = data.trade_id
		formspec = formspec..
			"label[8,2.6;Your invnetory:]"..
			"list[current_player;main;8,3;8,4;]"..
			"label[0.2,3.1;Configure trade with "..minetest.formspec_escape(dialog.n_npc)..":]"..
			"label[0.5,3.8;The customer pays:]"..
			-- show the second slot of the setup inventory in the detached player's inv
			"list[detached:yl_speak_up_player_"..pname..";setup;2,4.2;1,1;]"..
			"image[3.5,4.2;1,1;gui_furnace_arrow_bg.png^[transformR270]"..
			"label[4.0,3.8;"..minetest.formspec_escape(dialog.n_npc or "?").." sells:]"..
			-- show the second slot of said inventory
			"list[detached:yl_speak_up_player_"..pname..";setup;5,4.2;1,1;1]"..
			bg_img..
			yl_speak_up.set_on_action_failure_dialog(pname, data,
				"The player shall trade at least once.")

	-- "The NPC gives something to the player (i.e. a quest item).", -- 4
	-- (only for actions)
	elseif(data.what and id_prefix == "a_" and data.what == 4) then
		if(not(data)) then
			data = {}
		end
		local bg_img = ""
		if(data and data.item_string) then
			bg_img = "item_image[2.15,3.65;0.7,0.7;"..tostring(data.item_string).."]"
		end
		formspec = formspec..
			"label[8,2.6;Your inventory:]"..
			"list[current_player;main;8,3;8,4;]"..
			"label[1,3.1;"..minetest.formspec_escape(dialog.n_npc or "?").." gives:]"..
			"list[detached:yl_speak_up_player_"..pname..";npc_gives;2,3.5;1,1;]"..
			"label[3.2,4.0;"..
					minetest.formspec_escape(
						data.item_node_name
						or "- no item set -").."]"..
			"label[0.2,5.6;Set a description to turn the item into a special\n"..
				"quest item. Set a special ID (short text) so that\n"..
				"the player cannot create a fake item. Click on \n"..
				"\"Save\" to apply the changes.\n"..
				"You can use placeholders like $PLAYER_NAME$ etc.]"..
			"label[0.2,8.3;Special ID to set:]"..
			"field[3.2,8.0;14.5,0.6;action_item_quest_id;;"..
					minetest.formspec_escape(
						data.item_quest_id
						or "- none set -").."]"..
			"tooltip[action_item_quest_id;"..
				"Set this to a text that helps *you* to remember what this\n"..
				"special quest item is for (i.e. \"quest_deliver_augusts_"..
				"letter\").\n"..
				"The ID will be extended with the ID of the NPC and the\n"..
				"name of the player who got this item from the NPC.]"..
			"label[0.2,9.0;Description to set:]"..
			"field[3.2,8.7;14.5,0.6;action_item_desc;;"..
					minetest.formspec_escape(
						data.item_desc
						or "- no item set -").."]"..
			"tooltip[action_item_desc;"..
				"Set this to a text that helps the *player* to remember what\n"..
				"this special quest item is for (i.e. \"Letter from August to\n"..
				"Frederike\" for a piece of paper).\n"..
				"This description is shown in the inventory on mouseover.]"..
			bg_img..
			yl_speak_up.set_on_action_failure_dialog(pname, data,
				"The player shall take this offered item.")


	-- "The player is expected to give something to the NPC (i.e. a quest item).", -- 5
	-- (only for actions)
	elseif(data.what and id_prefix == "a_" and data.what == 5) then
		if(not(data)) then
			data = {}
		end
		local bg_img = ""
		if(data and data.item_string) then
			bg_img = "item_image[2.15,3.65;0.7,0.7;"..tostring(data.item_string).."]"
		end
		formspec = formspec..
			"label[8,2.6;Your inventory:]"..
			"list[current_player;main;8,3;8,4;]"..
			"label[1,3.1;"..minetest.formspec_escape(dialog.n_npc or "?").." wants:]"..
			"list[detached:yl_speak_up_player_"..pname..";npc_wants;2,3.5;1,1;]"..
			"label[3.2,4.0;"..
				minetest.formspec_escape(
					data.item_node_name
					or "- no item set -").."]"..
			"label[0.2,6.1;If you want a special ID and description, create\n"..
				"those via the \"NPC gives something to the player\"\n"..
				"menu option first and insert that item here. Don't\n"..
				"use other placeholders than $PLAYER_NAME$ for this!]"..
			"label[0.2,8.3;Expected special ID:]"..
			"label[4.0,8.3;"..
				minetest.formspec_escape(
					data.item_quest_id
					or "- none set -").."]"..
			"label[0.2,9.0;Expected description:]"..
			"label[4.0,9.0;"..
				minetest.formspec_escape(
					 data.item_desc
					 or "- none set -").."]"..
			bg_img..
			yl_speak_up.set_on_action_failure_dialog(pname, data,
				"The player shall give the NPC this item.")

	-- "The player has to manually enter a password or passphrase or some other text.", -- 6
	-- (only for actions)
	elseif(data.what and id_prefix == "a_" and data.what == 6) then
		if(not(data)) then
			data = {}
		end
		formspec = formspec..
			"label[0.2,3.3;What to ask the player and which answer to expect:]"..
			"label[0.2,4.0;Question to show:]"..
			"field[4.0,3.8;10.0,0.6;quest_question;;"..
				minetest.formspec_escape(
					data.quest_question
					or "Your answer:").."]"..
			"label[0.2,5.0;Expected answer:]"..
			"field[4.0,4.8;10.0,0.6;quest_answer;;"..
				minetest.formspec_escape(
					data.quest_answer
					or "- Insert the correct answer here -").."]"..
			"tooltip[quest_question;"..
				"This is just a short text that will be shown to remind\n"..
				"the player what he is asked for. Most of the question\n"..
				"ought to be part of the normal dialog of the NPC.]"..
			"tooltip[quest_answer;"..
				"The correct answer will not be shown to the player.\n"..
				"What the player enters will be compared to this\n"..
				"correct value.]"..
			"tooltip[select_on_action_failure;"..
				"If the player gives the wrong answer, you can show him\n"..
				"a diffrent target dialog (i.e. with text \"No, that answer\n"..
				"was wrong, but please try again!\"). In such a case the\n"..
				"effects/results of the current dialog option are *not*\n"..
				"executed.]"..
			yl_speak_up.set_on_action_failure_dialog(pname, data,
				"The player shall enter the correct answer.")

	-- "Call custom functions that are supposed to be overridden by the server.", -- 7
	-- (only for actions)
	elseif(data.what and id_prefix == "a_" and data.what == 7) then
		if(not(data)) then
			data = {}
		end
		formspec = formspec..
			"label[0.2,3.3;Note: Calling a custom function will require direct support "..
				"from the server.]"..
			"label[0.2,4.0;Parameter for custom function:]"..
			"field[6.0,3.7;10.0,0.6;custom_param;;"..
				minetest.formspec_escape(
					data.custom_param
					or "- Insert a text that is passed on to your function here -").."]"..
			"tooltip[custom_param;"..
				"The custom parameter may help whoever implements the\n"..
				"custom function to more easily see what it belongs to.\n"..
				"Dialog and option ID are also passed as parameters.]"..
			"tooltip[select_on_action_failure;"..
				"If the player gives the wrong answer, you can show him\n"..
				"a diffrent target dialog (i.e. with text \"No, that answer\n"..
				"was wrong, but please try again!\"). In such a case the\n"..
				"effects/results of the current dialog option are *not*\n"..
				"executed.]"..
			yl_speak_up.set_on_action_failure_dialog(pname, data,
				"The player shall click on the right button.")
	end
	return formspec..save_button
end


-- helper function
yl_speak_up.set_on_action_failure_dialog = function(pname, data, instruction)
	local dialog = yl_speak_up.speak_to[pname].dialog
	local nr = 1
	if(data and data.action_failure_dialog) then
		nr = data.action_failure_dialog + 1
	end
	local sorted_dialog_list = yl_speak_up.sort_keys(dialog.n_dialogs)
	local on_failure_dialog =
		"label[0.2,9.9;"..tostring(instruction).." If he doesn't, go to dialog:]"..
		"dropdown[11.0,9.6;2.8,0.6;select_on_action_failure;"..
			"- current one -,"..
			table.concat(sorted_dialog_list, ",")..";"..tostring(nr)..";]"
	if(nr and nr > 1) then
		local failure_d_id = sorted_dialog_list[ nr - 1]
		on_failure_dialog = on_failure_dialog..
			"hypertext[1.2,10.4.0;19.6,1.0;d_text;<normal>"..
			minetest.formspec_escape(dialog.n_dialogs[ failure_d_id ].d_text or "?")..
			"\n</normal>]"
	end
	return on_failure_dialog
end