-- This file contains what is necessary to execute an action.

-- monitor changes to the npc_gives and npc_wants slots (in particular when editing actions)
-- how: can be "put" or "take"
yl_speak_up.action_inv_changed = function(inv, listname, index, stack, player, how)
	if(not(player)) then
		return
	end
	local pname = player:get_player_name()
	local n_id = yl_speak_up.speak_to[pname].n_id
	-- if not in edit mode: the player may just be normally interacting with the NPC;
	-- nothing to do for us here (wait for the player to click on "save")
	if(not(n_id) or yl_speak_up.edit_mode[pname] ~= n_id) then
		return
	end
	-- is the player in the process of editing an action of the npc_gives/npc_wants type?
	local target_fs = "edit_actions"
	local data = yl_speak_up.speak_to[pname][ "tmp_action" ]
	if(not(data) or (data.what ~= 4 and data.what ~= 5)) then
		-- we are editing an action
		if(data) then
			return
		end
		-- it might be a precondition
		data = yl_speak_up.speak_to[pname][ "tmp_prereq" ]
		if(not(data) or (data.what ~= 8)) then
			return
		end
		target_fs = "edit_preconditions"
	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
	if(how == "put") then
		data.item_node_name = stack:get_name().." "..stack:get_count()
		local meta = stack:get_meta()
		if(meta and meta:get_string("description")) 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
		if(meta and meta:get_string("yl_speak_up:quest_id")) then
			data.item_quest_id = meta:get_string("yl_speak_up:quest_id")
		end
	elseif(how == "take" and data.what == 4) then
		data.item_desc = "- no item set -"
		data.item_node_name = ""
	elseif(how == "take" and data.what == 5) then
		data.item_desc = "- no item set -"
		data.item_node_name = ""
	end
	-- show the updated formspec to the player
	yl_speak_up.show_fs(player, target_fs, nil)
	-- no need to check anything more here; the real checks need to be done
	-- when the player presses the save/store/execute button
end


-- actions - in contrast to preconditions and effects - may take time
-- because the player usually gets presented a formspec and needs to
-- react to that; thus, we can't just execute all actions simultaneously
yl_speak_up.execute_next_action = function(player, a_id, result_of_a_id)
	local pname = player:get_player_name()
	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 dialog = yl_speak_up.speak_to[pname].dialog
	yl_speak_up.debug_msg(player, n_id, o_id, "Last action: "..tostring(a_id).." returned "..
				tostring(result_of_a_id)..".")
	local actions = {}
	local effects = {}
	local sorted_key_list = {}
	if(dialog
	  and dialog.n_dialogs
	  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
		-- get the actual actions
		actions = dialog.n_dialogs[d_id].d_options[o_id].actions
		-- needed later on when all actions are executed
		effects = dialog.n_dialogs[d_id].d_options[o_id].o_results
	end
	if(actions) then
		-- sort the actions so that we can execute them always in the
		-- same order
		sorted_key_list = yl_speak_up.sort_keys(actions)
		local nr = 0
		if(not(a_id)) then
			-- check if the action(s) can be executed
			local time_now = yl_speak_up.get_time_in_seconds()
			-- is there a limiton how many failed attempts there can be per time?
			local timer_name = "timer_on_failure_"..tostring(d_id).."_"..tostring(o_id)
			local timer_data = yl_speak_up.get_variable_metadata( timer_name, "parameter", true)
			if(timer_data
			  and timer_data["max_attempts"] and tonumber(timer_data["max_attempts"]) > 0
			  and timer_data["duration"]     and tonumber(timer_data["duration"]) > 0) then
				local new_times = ""
				local times = yl_speak_up.get_quest_variable_value(pname, timer_name)
				local parts = string.split(times or "", " ")
				local count = 0
				for i, p in ipairs(parts) do
					if(p and tonumber(p)
					  and (tonumber(p) + tonumber(timer_data["duration"])>time_now)) then
						new_times = new_times.." "..p
						count = count + 1
					end
				end
				-- all timers are expired
				if(count == 0) then
					yl_speak_up.set_quest_variable_value(pname, timer_name, nil)
				-- some timers are expired
				elseif(new_times ~= times) then
					yl_speak_up.set_quest_variable_value(pname, timer_name, new_times)
				end
				if(count >= tonumber(timer_data["max_attempts"])) then
					-- show the same dialog again, but with the failure message
					yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = d_id,
						alternate_text = timer_data[ "alternate_text" ]
						or yl_speak_up.standard_text_if_action_failed_too_often})
					return
				end
			end
			-- is there a limiton how fast the action may be repeated again?
			timer_name = "timer_on_success_"..tostring(d_id).."_"..tostring(o_id)
			timer_data = yl_speak_up.get_variable_metadata(timer_name, "parameter", true)
			if(timer_data
			  and timer_data["duration"]     and tonumber(timer_data["duration"]) > 0) then
				local last_time = yl_speak_up.get_quest_variable_value(pname, timer_name)
				if(last_time and tonumber(last_time)
				  and tonumber(last_time) + tonumber(timer_data["duration"]) > time_now) then
					-- show the same dialog again, but with the failure message
					yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = d_id,
						alternate_text = timer_data[ "alternate_text" ]
						or yl_speak_up.standard_text_if_action_repeated_too_soon})
					return
				else
					-- the timer has expired
					yl_speak_up.set_quest_variable_value(pname, timer_name, nil)
				end
			end

		else -- if(a_id) then
			nr = table.indexof(sorted_key_list, a_id)
			-- did the player go back?
			if(nr > -1 and result_of_a_id == nil) then
				-- set the current action to nil
				yl_speak_up.speak_to[pname].a_id = nil
				-- no option of the new dialog has been selected yet
				yl_speak_up.speak_to[pname].o_id = nil
				-- show the new dialog
				yl_speak_up.debug_msg(player, n_id, o_id, "Action "..
					tostring(a_id).." aborted. Switching back to dialog "..
					tostring(d_id)..".")
				yl_speak_up.speak_to[pname].o_id = nil
				yl_speak_up.speak_to[pname].a_id = nil
				yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = d_id})
				return
			-- did the action fail?
			elseif(nr > -1 and not(result_of_a_id)) then
				-- is there a limiton how many failed attempts there can be per time?
				local timer_name = "timer_on_failure_"..tostring(d_id).."_"..tostring(o_id)
				local timer_data = yl_speak_up.get_variable_metadata(
								timer_name, "parameter", true)
				-- store that (another?) attempt to do the action failed
				if(timer_data
				  and timer_data["max_attempts"] and tonumber(timer_data["max_attempts"])> 0
				  and timer_data["duration"]     and tonumber(timer_data["duration"])> 0) then
					local times = yl_speak_up.get_quest_variable_value(pname, timer_name)
					if(not(times)) then
						times = ""
					end
					-- variables are stored as strings, not as lists
					yl_speak_up.set_quest_variable_value(pname, timer_name,
							times.." "..yl_speak_up.get_time_in_seconds())
				end

				local this_action = actions[ sorted_key_list[ nr ]]
				-- if there is an on_failure target dialog: go there

				-- set the current action to nil
				yl_speak_up.speak_to[pname].a_id = nil
				-- no option of the new dialog has been selected yet
				yl_speak_up.speak_to[pname].o_id = nil
				-- show the new dialog
				yl_speak_up.debug_msg(player, n_id, o_id, "Action "..
					tostring(a_id).." failed. Switching to dialog "..
					tostring(this_action.a_on_failure)..".")
				yl_speak_up.speak_to[pname].d_id = this_action.a_on_failure
				yl_speak_up.speak_to[pname].o_id = nil
				yl_speak_up.speak_to[pname].a_id = nil
				yl_speak_up.show_fs(player, "talk", {n_id = n_id,
					d_id = this_action.a_on_failure,
					alternate_text = this_action.alternate_text})
				return
			end
		end
		-- get the next entry
		if(nr > -1 and nr < #sorted_key_list and sorted_key_list[nr + 1]) then
			local next_action = actions[ sorted_key_list[ nr + 1 ]]
			-- store which action we are currently executing
			yl_speak_up.speak_to[pname].a_id = next_action.a_id
			-- execute the next action
			yl_speak_up.debug_msg(player, n_id, o_id, "Executing next action "..
				tostring(next_action.a_id)..".")
			yl_speak_up.execute_action(player, n_id, o_id, next_action)
			-- the player needs time to react
			return
		end
	end
	-- when all actions are executed:
	-- is there a limiton how fast the action may be repeated again?
	local timer_name = "timer_on_success_"..tostring(d_id).."_"..tostring(o_id)
	local timer_data = yl_speak_up.get_variable_metadata(timer_name, "parameter", true)
	-- store that the action was executed successfully
	if(timer_data
	  and timer_data["duration"]     and tonumber(timer_data["duration"]) > 0) then
		yl_speak_up.set_quest_variable_value(pname, timer_name, yl_speak_up.get_time_in_seconds())
	end
	-- set the current action to nil
	yl_speak_up.speak_to[pname].a_id = nil
	yl_speak_up.debug_msg(player, n_id, o_id, "All actions have been executed successfully. "..
		"Doing effects/results now.")
	-- execute all effects/results
	local res = yl_speak_up.execute_all_relevant_effects(player, effects, o_id, true)
	local target_dialog = res.next_dialog
	yl_speak_up.speak_to[pname].o_id = nil
	yl_speak_up.speak_to[pname].a_id = nil
	if(not(target_dialog)
	  or target_dialog == ""
	  or not(dialog.n_dialogs[target_dialog])) then
		target_dialog = d_id
	end
	-- the function above returns a target dialog; show that to the player
	yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = target_dialog,
				alternate_text = res.alternate_text})
end


yl_speak_up.execute_action = function(player, n_id, o_id, a)
	if(not(a.a_type) or a.a_type == "" or a.a_type == "none") then
		-- no action - nothing to do
		return true
	elseif(a.a_type == "trade") then
		yl_speak_up.show_fs(player, "trade_simple", a.a_value)
		return
	elseif(a.a_type == "npc_gives") then
		yl_speak_up.show_fs(player, "action_npc_gives", a.a_value)
		return
	elseif(a.a_type == "npc_wants") then
		yl_speak_up.show_fs(player, "action_npc_wants", a.a_value)
		return
	elseif(a.a_type == "text_input") then
		-- start with an empty answer
		yl_speak_up.show_fs(player, "action_text_input", "")
		return
	elseif(a.a_type == "custom") then
		yl_speak_up.show_fs(player, "action_custom", a.a_value)
		return
	end
	-- fallback: unkown type
	return false
end


-- helper function;
-- returns the action the player is currently faced with (or nil if none)
yl_speak_up.get_action_by_player = function(player)
	local pname = player:get_player_name()
	local dialog = yl_speak_up.speak_to[pname].dialog
	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 a_id = yl_speak_up.speak_to[pname].a_id
	if(not(dialog) or not(d_id) or not(o_id) or not(a_id)
	  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])
	  or not(dialog.n_dialogs[d_id].d_options[o_id].actions)
	  or not(dialog.n_dialogs[d_id].d_options[o_id].actions[a_id])) then
		return nil
	end
	return dialog.n_dialogs[d_id].d_options[o_id].actions[a_id]
end


-- Create the quest item by taking a raw item (i.e. a general piece of paper) out
-- of the NPC's inventory, applying a description (if given) and quest id (if
-- given); place the quest item in the trade inv of the player in the npc_gives slot.
-- The npc_gives inv is managed mostly by the NPC, except when in edit mode. We can
-- just overwrite anything old in there.
-- Returns false if the creation of the quest item wasn't possible (i.e. the
-- NPC had no paper left).
yl_speak_up.action_quest_item_prepare = function(player)
	-- which action are we talking about?
	local a = yl_speak_up.get_action_by_player(player)
	if(not(a) or not(a.a_id) or not(a.a_value)) then
		return false
	end
	local pname = player:get_player_name()
	local n_id = yl_speak_up.speak_to[pname].n_id
	-- what shall the NPC give?
	local stack = ItemStack(a.a_value)
	-- get the inventory of the NPC
	local npc_inv = minetest.get_inventory({type="detached", name="yl_speak_up_npc_"..tostring(n_id)})
	-- does the NPC have the item we are looking for?
	if(not(npc_inv:contains_item("npc_main", stack))) then
		local o_id = yl_speak_up.speak_to[pname].o_id
		yl_speak_up.debug_msg(player, n_id, o_id, "Action "..tostring(a.a_id)..": NPC ran out of "..
			tostring(a.a_value)..".")
		-- just go back; the player didn't do anything wrong
		return nil
	end
	-- get the items from the NPCs inventory
	local new_stack = npc_inv:remove_item("npc_main", stack)
	local meta = new_stack:get_meta()
	-- if given: set the item stack description
	if(a.a_item_desc and a.a_item_desc ~= "") then
		local dialog = yl_speak_up.speak_to[pname].dialog
		-- replace $PLAYER_NAME$ etc. in quest item description
		meta:set_string("description", yl_speak_up.replace_vars_in_text(a.a_item_desc, dialog, pname))
	end
	if(a.a_item_quest_id and a.a_item_quest_id ~= "") 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(a.a_item_quest_id))
	end
	-- put the stack in the npc_gives-slot of the trade inventory of the player
	-- (as that slot is managed by the NPC alone we don't have to worry about
	-- anything else in the slot)
	local trade_inv = minetest.get_inventory({type="detached", name="yl_speak_up_player_"..pname})
	-- actually put the stack in there
	trade_inv:set_stack("npc_gives", 1, new_stack)
	return true
end


-- check if the item in the npc_gives slot is the one the NPC wants
yl_speak_up.action_quest_item_check = function(player)
	-- which action are we talking about?
	local a = yl_speak_up.get_action_by_player(player)
	if(not(a) or not(a.a_id) or not(a.a_value)) then
		return false
	end
	local pname = player:get_player_name()
	local n_id = yl_speak_up.speak_to[pname].n_id
	local o_id = yl_speak_up.speak_to[pname].o_id
	-- get the item that needs to be checked
	local trade_inv = minetest.get_inventory({type="detached", name="yl_speak_up_player_"..pname})
	local stack = trade_inv:get_stack("npc_wants", 1)
	-- nothing there?
	if(stack:is_empty()) then
		yl_speak_up.debug_msg(player, n_id, o_id, "Action "..tostring(a.a_id)..": No item found.")
		return false
	end
	local cmp = tostring(stack:get_name()).." "..(stack:get_count())
	-- wrong item or wrong amount?
	if(cmp ~= a.a_value) then
		yl_speak_up.debug_msg(player, n_id, o_id, "Action "..tostring(a.a_id)..
			": Wrong item given. Got: "..stack:to_string()..
			" Expected: "..tostring(a.a_value)..".")
		return false
	end
	local meta = stack:get_meta()
	-- the description is not checked; just the quest id (if given)
	if(a.a_item_quest_id and a.a_item_quest_id ~= "") then
		-- we don't check here if the item was given by the right NPC;
		-- only the quest id has to fit
		if(meta:get_string("yl_speak_up:quest_id") ~= a.a_item_quest_id) then
			yl_speak_up.debug_msg(player, n_id, o_id, "Action "..tostring(a.a_id)..
				": Wrong quest item (wrong ID).")
			return false
		end
		-- was this quest item given to another player?
		if(meta:get_string("yl_speak_up:quest_item_for") ~= pname) then
			yl_speak_up.debug_msg(player, n_id, o_id, "Action "..tostring(a.a_id)..
				": Quest item was given to "..
				tostring(meta:get_string("yl_speak_up:quest_item_for"))..
				", but "..tostring(pname).." gave it.")
			return false
		end
	end
	yl_speak_up.debug_msg(player, n_id, o_id, "Action "..tostring(a.a_id)..
		": Quest item checked ok.")
	return true
end


-- strip the quest information from the item and give it back to the NPC;
-- returns the modified stack (but also places it in the NPC's inventory)
yl_speak_up.action_quest_item_take_back = function(player)
	-- which action are we talking about?
	local a = yl_speak_up.get_action_by_player(player)
	if(not(a) or not(a.a_id) or not(a.a_value)) then
		return false
	end
	local pname = player:get_player_name()
	local n_id = yl_speak_up.speak_to[pname].n_id
	-- get the item that the NPC shall take back (or accept in npc_wants)
	local trade_inv = minetest.get_inventory({type="detached", name="yl_speak_up_player_"..pname})
	local stack = trade_inv:get_stack("npc_wants", 1)
	-- if it was the wrong item:
	if(not(yl_speak_up.action_quest_item_check(player))) then
		local player_inv = player:get_inventory()
		-- give the item back to the player
		local remaining = player_inv:add_item("main", stack)
		-- very unlikely - but in case the item did not fit back into the player's inv:
		if(remaining and not(remaining:is_empty())) then
			local p = player:get_pos()
			-- throw it at the player
			minetest.add_item({x=p.x, y=p.y+1, z=p.z},  stack)
		end
		-- remove it from the trade inv slot
		trade_inv:set_stack("npc_wants", 1, ItemStack())
		return false
	end
	-- we already checked that it is the correct item
	local meta = stack:get_meta()
	-- if given: set the item stack description
	if(a.a_item_desc and a.a_item_desc ~= "") then
		meta:set_string("description", "")
	end
	-- delete all the special IDs that where added before
	if(a.a_item_quest_id and a.a_item_quest_id ~= "") then
		meta:set_string("yl_speak_up:quest_item_for", "")
		meta:set_string("yl_speak_up:quest_item_from", "")
		meta:set_string("yl_speak_up:quest_id", "")
	end
	local npc_inv = minetest.get_inventory({type="detached", name="yl_speak_up_npc_"..tostring(n_id)})
	-- Has the NPC room enough for the item?
	-- If the NPC doesn't have room, the item will be destroyed in the next step by setting
	-- npc_wants to an empty stack. While this may lead to some item loss, it is more important
	-- that the quest item was properly accepted (and discarded of) rather than worrying about
	-- where to put it or even giving it back and letting the quest fail.
	if(npc_inv:room_for_item("npc_main", stack)) then
		npc_inv:add_item("npc_main", stack)
		-- save the inventory of the NPC
		yl_speak_up.save_npc_inventory(n_id)
	end
	-- the NPC has accepted the item
	trade_inv:set_stack("npc_wants", 1, ItemStack())
	return true
end


-- show the diffrent action-related formspecs and handle input to them
-- (Note: trade is handled in trade_simple.lua)

yl_speak_up.input_fs_action_npc_gives = function(player, formname, fields)
	-- back from error_msg? then show the formspec again
	if(fields.back_from_error_msg) then
		-- do not create a new item
		yl_speak_up.show_fs(player, "action_npc_gives", nil)
		return
	end
	local pname = player:get_player_name()
	local trade_inv = minetest.get_inventory({type="detached", name="yl_speak_up_player_"..pname})
	local a_id = yl_speak_up.speak_to[pname].a_id
	if(fields.npc_does_not_have_item) then
		-- the NPC can't supply the item - abort the action
		yl_speak_up.execute_next_action(player, a_id, nil)
		return
	end
	-- is the npc_gives inv empty? then all went as expected.
	-- (it does not really matter which button the player pressed in this case)
	if(trade_inv:is_empty("npc_gives")) then
		-- the NPC has given the item to the player; save the NPCs inventory
		local n_id = yl_speak_up.speak_to[pname].n_id
		yl_speak_up.save_npc_inventory(n_id)
		-- the action was a success; the NPC managed to give the item to the player
		yl_speak_up.execute_next_action(player, a_id, true)
		return
	end
	-- the npc_gives slot does not accept input - so we don't have to check for any misplaced items
	-- but if the player aborts, give the item back to the NPC
	if(fields.back_to_talk) then
		-- strip the quest item info from the stack (so that it may stack again)
		-- and give that (hopefully) stackable stack back to the NPC
		yl_speak_up.action_quest_item_take_back(player)
		-- the action failed
		yl_speak_up.execute_next_action(player, a_id, nil)
		return
	end
	-- else show a message to the player that he ought to take the item
	yl_speak_up.show_fs(player, "msg", {
		input_to = "yl_speak_up:action_npc_gives",
		formspec = "size[7,1.5]"..
			"label[0.2,-0.2;"..
				"Please take the offered item and click on \"Done\"!\n"..
				"If you can't take it, click on \"Back to talk\".]"..
				"button[2,1.0;1.5,0.9;back_from_error_msg;Back]"})
end


yl_speak_up.get_fs_action_npc_gives = function(player, param)
	-- called for the first time; create the item the NPC wants to give
	if(param) then
		if(not(yl_speak_up.action_quest_item_prepare(player))) then
			local pname = player:get_player_name()
			local dialog = yl_speak_up.speak_to[pname].dialog
			-- it's not the fault of the player that the NPC doesn't have the item;
			-- so tell him that (the action will still fail)
			return "size[7,2.0]"..
				"label[0.2,-0.2;"..
					minetest.formspec_escape(dialog.n_npc or "- ? -")..
					" is very sorry:\n"..
					"The item intended for you is currently unavailable.\n"..
					"Please come back later!]"..
					"button[2,1.5;1.5,0.9;npc_does_not_have_item;Back]"
		end
	end
	local pname = player:get_player_name()
	local dialog = yl_speak_up.speak_to[pname].dialog
	return "size[8.5,8]"..
		"list[current_player;main;0.2,3.85;8,1;]"..
		"list[current_player;main;0.2,5.08;8,3;8]"..
		"button[0.2,0.0;2.0,0.9;back_to_talk;Back to talk]"..
		"button[4.75,1.6;1.5,0.9;finished_action;Done]"..

		"tooltip[back_to_talk;Click here if you don't want to (or can't)\n"..
			"take the offered item.]"..
		"tooltip[finished_action;Click here once you have taken the item and\n"..
			"stored it in your inventory.]"..
		"label[1.5,0.7;"..minetest.formspec_escape(dialog.n_npc or "- ? -")..
			" offers to you:]"..
		-- unlike the npc_gives slot - which is used for setting up the NPC - the
		-- npc_gives slot does not allow putting something in
		"list[detached:yl_speak_up_player_"..pname..";npc_gives;3.25,1.5;1,1;]" ..
		"label[1.5,2.7;Take the offered item and click on \"Done\" to proceed.]"
end


yl_speak_up.input_fs_action_npc_wants = function(player, formname, fields)
	-- back from error_msg? then show the formspec again
	if(fields.back_from_error_msg) then
		yl_speak_up.show_fs(player, "action_npc_wants", nil)
		return
	end
	local pname = player:get_player_name()
	local trade_inv = minetest.get_inventory({type="detached", name="yl_speak_up_player_"..pname})
	local a_id = yl_speak_up.speak_to[pname].a_id
	-- is the npc_wants inv empty and the player pressed the back to talk button? then the action failed.
	if(trade_inv:is_empty("npc_wants") and fields.back_to_talk) then
		-- the action was aborted
		yl_speak_up.execute_next_action(player, a_id, nil)
		return
	end
	-- the player tried to give something; check if it is the right thing
	if(not(trade_inv:is_empty("npc_wants"))) then
		local stack = trade_inv:get_stack("npc_wants", 1)
		-- check if it really is the item the NPC wanted; let the NPC take it
		local is_correct_item = yl_speak_up.action_quest_item_take_back(player)
		-- the action may have been a success or failure
		yl_speak_up.execute_next_action(player, a_id, is_correct_item)
		return
	end
	-- else show a message to the player
	yl_speak_up.show_fs(player, "msg", {
		input_to = "yl_speak_up:action_npc_wants",
		formspec = "size[7,1.5]"..
			"label[0.2,-0.2;"..
				"Please insert the item for the npc and click on \"Done\"!\n"..
				"If you don't have what he wants, click on \"Back to talk\".]"..
				"button[2,1.0;1.5,0.9;back_from_error_msg;Back]"})
end


yl_speak_up.get_fs_action_npc_wants = function(player, param)
	local pname = player:get_player_name()
	local dialog = yl_speak_up.speak_to[pname].dialog
	return "size[8.5,8]"..
		"list[current_player;main;0.2,3.85;8,1;]"..
		"list[current_player;main;0.2,5.08;8,3;8]"..
		"button[0.2,0.0;2.0,0.9;back_to_talk;Back to talk]"..
		"button[4.75,1.6;1.5,0.9;finished_action;Done]"..

		"tooltip[back_to_talk;Click here if you don't know what item the\n"..
			"NPC wants or don't have the desired item.]"..
		"tooltip[finished_action;Click here once you have placed the item in\n"..
			"the waiting slot.]"..
		"label[1.5,0.7;"..minetest.formspec_escape(dialog.n_npc or "- ? -")..
			" expects something from you:]"..
		"list[detached:yl_speak_up_player_"..pname..";npc_wants;3.25,1.5;1,1;]" ..
		"label[1.5,2.7;Insert the right item and click on \"Done\" to proceed.]"
end


yl_speak_up.input_fs_action_text_input = function(player, formname, fields)
	-- back from error_msg? then show the formspec again
	if(fields.back_from_error_msg) then
		-- the error message is only shown if the input was empty
		yl_speak_up.show_fs(player, "action_text_input", "")
		return
	end
	local pname = player:get_player_name()
	local a_id = yl_speak_up.speak_to[pname].a_id
	local a = yl_speak_up.get_action_by_player(player)
	if(fields.back_to_talk) then
		-- the action was aborted
		yl_speak_up.execute_next_action(player, a_id, nil)
		return
	end
	if(fields.finished_action and fields.quest_answer and fields.quest_answer ~= "") then
		-- is the answer correct?
		-- strip leading and tailing blanks
		local success = not(not(fields.quest_answer and a.a_value
			and fields.quest_answer:trim() == a.a_value:trim()))
		-- the action was a either a success or failure
		yl_speak_up.execute_next_action(player, a_id, success)
		return
	end
	-- else show a message to the player
	yl_speak_up.show_fs(player, "msg", {
		input_to = "yl_speak_up:action_text_input",
		formspec = "size[7,1.5]"..
			"label[0.2,-0.2;"..
				"Please answer the question and click on \"Send answer\"!\n"..
				"If you don't know the answer, click on \"Back to talk\".]"..
				"button[2,1.0;1.5,0.9;back_from_error_msg;Back]"})
end


yl_speak_up.get_fs_action_text_input = function(player, param)
	local pname = player:get_player_name()
	local dialog = yl_speak_up.speak_to[pname].dialog
	local a = yl_speak_up.get_action_by_player(player)
	if(not(a)) then
		return ""
	end
	return "size[12.0,4.5]"..
		"button[0.2,0.0;2.0,0.9;back_to_talk;Back to talk]"..
		"button[2.0,3.7;3.0,0.9;finished_action;Send answer]"..

		"tooltip[back_to_talk;Click here if you don't know the answer.]"..
		"tooltip[finished_action;Click here once you've entered the answer.]"..
		"label[0.2,1.2;"..minetest.formspec_escape(a.a_question or "Your answer:").."]"..
		"label[0.2,1.9;Answer:]"..
		"field[1.6,2.2;10.0,0.6;quest_answer;;"..tostring(param or "").."]"..
		"label[0.2,2.8;"..minetest.formspec_escape(
			"["..(dialog.n_npc or "- ? -").." looks expectantly at you.]").."]"
end