-- This is the main talkdialog the NPC shows when right-clicked.


yl_speak_up.input_talk = function(player, formname, fields)
        if formname ~= "yl_speak_up:talk" then
            return
        end

        local pname = player:get_player_name()
        local o = ""

	-- error: not talking?
	if(not(yl_speak_up.speak_to[pname])) then
		return
	end
	local n_id = yl_speak_up.speak_to[pname].n_id

	-- the NPC needs to be configured first; route input to the configuration dialog
	if(not(yl_speak_up.speak_to[pname].dialog)
	  or not(yl_speak_up.speak_to[pname].dialog.n_npc)
	  or not(yl_speak_up.speak_to[pname].d_id)) then
		yl_speak_up.input_fs_initial_config(player, formname, fields)
		return
	end

	-- Is the player working on this particular npc?
	local edit_mode = (yl_speak_up.edit_mode[pname] == yl_speak_up.speak_to[pname].n_id)

	-- if in edit mode: detect if something was changed;
	if(edit_mode or fields.button_edit_name_and_description) then
		local result = yl_speak_up.edit_mode_apply_changes(pname, fields)
        end

	-- show which dialogs point to this one
	if(edit_mode and fields.show_what_points_to_this_dialog) then
		local dialog = yl_speak_up.speak_to[pname].dialog
		local d_id = yl_speak_up.speak_to[pname].d_id
		yl_speak_up.show_fs(player, "show_what_points_to_this_dialog",
			yl_speak_up.speak_to[pname].d_id)
		return
	end

	-- the player wants to change name and description; show the formspec
	if(edit_mode and fields.button_edit_name_and_description) then
		-- this is not the initial config - but the same formspec can be used
		yl_speak_up.show_fs(player, "initial_config",
			{n_id = n_id, d_id = yl_speak_up.speak_to[pname].d_id, false})
		return
	end

	-- the player wants to access the inventory of the NPC
	if(edit_mode and fields.show_inventory) then
		-- the inventory is just an inventory with a back button; come back to this dialog here
		yl_speak_up.show_fs(player, "inventory")
		return
	end

	-- change skin, cape and wielded items
	if(edit_mode and fields.edit_skin) then
		local dialog = yl_speak_up.speak_to[pname].dialog
		-- necessary so that the fashin formspec can be created
		yl_speak_up.speak_to[pname].n_npc = dialog.n_npc
		yl_speak_up.show_fs(player, "fashion")
		return
	end

	if(edit_mode and fields.button_save_dialog) then
		yl_speak_up.show_fs(player, "talk",
			{n_id = n_id, d_id = yl_speak_up.speak_to[pname].d_id, do_save = true})
		return
	end

	-- start edit mode (requires npc_talk_owner)
	if fields.button_start_edit_mode then
	    -- check if this particular NPC is really owned by this player or if the player has global privs
            if(not(yl_speak_up.may_edit_npc(player, n_id))) then
                minetest.chat_send_player(pname, "Sorry. You do not have the npc_talk_owner or npc_master priv.")
                return
	    end
	    -- the staff allows to create multiple target dialogs as result; this makes no sense
	    -- and is too disambigous
	    if(yl_speak_up.check_for_disambigous_results(n_id, pname)) then
                -- this needs to be fixed by someone with a staff; we don't know which dialog is the right
		-- result
                return
            end
	    -- for older formspec versions: reset scroll counter
	    yl_speak_up.speak_to[pname].counter = 1
	    yl_speak_up.speak_to[pname].option_index = 1
	    -- enter edit mode with that particular NPC
            yl_speak_up.edit_mode[pname] = yl_speak_up.speak_to[pname].n_id
	    -- load the NPC dialog anew - but only what the NPC itself has to say, no generic dialogs
            yl_speak_up.speak_to[pname].dialog = yl_speak_up.load_dialog(n_id, false)
	    -- start a new chat - but this time in edit mode
            yl_speak_up.speak_to[pname].d_id = nil
            yl_speak_up.show_fs(player, "talk", {n_id = yl_speak_up.speak_to[pname].n_id, d_id = nil})
	    return
        -- end edit mode (does not require the priv; will only switch back to normal behaviour)
        elseif fields.button_end_edit_mode then
            -- if there are any changes done: ask first and don't end edit mode yet
	    yl_speak_up.show_fs(player, "quit", nil)
	    return
       end

        if fields.quit or fields.button_exit then
            -- if there are any changes done: ask first and don't quit yet
	    yl_speak_up.show_fs(player, "quit", nil)
            return
        end

	-- allow the player to take the item back
	if(fields.show_player_offers_item and fields.show_player_offers_item ~= "") then
	    yl_speak_up.show_fs(player, "player_offers_item", nil)
	    return
	end


        if fields.button_up then
            yl_speak_up.speak_to[pname].option_index =
                yl_speak_up.speak_to[pname].option_index + yl_speak_up.max_number_of_buttons
            yl_speak_up.show_fs(player, "talk", {n_id = yl_speak_up.speak_to[pname].n_id,
                                                 d_id = yl_speak_up.speak_to[pname].d_id})
            return
        elseif fields.button_down then --and yl_speak_up.speak_to[pname].option_index > yl_speak_up.max_number_of_buttons then
            yl_speak_up.speak_to[pname].option_index =
                yl_speak_up.speak_to[pname].option_index - yl_speak_up.max_number_of_buttons
            if yl_speak_up.speak_to[pname].option_index < 0 then
                yl_speak_up.speak_to[pname].option_index = 1
            end
            yl_speak_up.show_fs(player, "talk", {n_id = yl_speak_up.speak_to[pname].n_id,
                                                 d_id = yl_speak_up.speak_to[pname].d_id})
            return
        else
            yl_speak_up.speak_to[pname].option_index = 1
        end

	-- the player wants to see the trade list
	if(fields.show_trade_list) then
		yl_speak_up.show_fs(player, "trade_list", nil)
		return
	end

	-- the player wants to give something to the NPC
	if(fields.player_offers_item) then
		if(not(edit_mode)) then
			-- normal mode: take the item the player wants to offer
			yl_speak_up.show_fs(player, "player_offers_item", nil)
		else
			local dialog = yl_speak_up.speak_to[pname].dialog
			local future_d_id = "d_got_item"
			-- make sure this dialog exists; create if needed
			if(not(dialog.n_dialogs[ future_d_id ])) then
				dialog.n_dialogs[future_d_id] = {
					d_id = future_d_id,
					d_type = "text",
					d_text = "",
					d_sort = 9999 -- make this the last option
				}
			end
			-- in edit mode: allow to edit the options
			yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = future_d_id})
		end
		return
	end

        for k, v in pairs(fields) do
            -- only split into 2 parts at max
            local s = string.split(k, "_", false, 2)

            if
                s[1] == "button" and s[2] ~= nil and s[2] ~= "" and s[2] ~= "exit" and s[2] ~= "back" and s[3] ~= nil and
                    s[2] ~= "up" and
                    s[2] ~= "down"
             then
                o = s[2] .. "_" .. s[3]
            end
        end

	if not(edit_mode) and o == "" then
            return
        end

        -- Let's check if the button was among the "allowed buttons". Only those may be executed
        if not(edit_mode) and (yl_speak_up.speak_to[pname].allowed and yl_speak_up.speak_to[pname].allowed[o] == false) then
            return
        end

        -- button was clicked, now let's execute the results

        local d_id = yl_speak_up.speak_to[pname].d_id

        local dialog = yl_speak_up.speak_to[pname].dialog

	-- we may soon need actions and o_results from the selected_option
	local selected_option = {}
	if(d_id and o and 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]) then
		selected_option = dialog.n_dialogs[d_id].d_options[o]
	end

	if(not(edit_mode)) then
		-- abort if the option does not exist
		if(not(selected_option)) then
			return
		end
		yl_speak_up.speak_to[pname].o_id = o
		-- start with executing the first action
		yl_speak_up.execute_next_action(player, nil, true)
		return
	end

	-- all three buttons (pre(C)onditions, (Ef)fects, edit option) lead to the same new formspec
	if( edit_mode ) then
		local n_dialog = dialog.n_dialogs[d_id]

		if(n_dialog and n_dialog.d_options) then
			for o_id,v in pairs(n_dialog.d_options) do
				if( fields["edit_option_"..o_id]
				 or fields["conditions_"..o_id]
				 or fields["actions_"..o_id]
				 or fields["effects_"..o_id]) then
					-- store which option we want to edit
					yl_speak_up.speak_to[pname].o_id = o_id
					-- if something was changed: ask for confirmation
					yl_speak_up.show_fs(player, "edit_option_dialog",
						{n_id = yl_speak_up.speak_to[pname].n_id,
						d_id = d_id, o_id = o_id, caller="button"})
					return
				end
			end
		end


	    -- in edit mode: has another dialog been selected?
            -- if nothing better can be found: keep the old dialog
            local show_dialog = d_id
	    -- an option button was selected;
	    -- since we do not execute actions and effects in edit mode, we need to find out the
	    -- right target dialog manually (and assume all went correct)
	    if( o ~= "" ) then
		-- find out the normal target dialog of this option
		if(selected_option and selected_option.o_results) then
			for k, v in pairs(selected_option.o_results) do
				if(v and v.r_type == "dialog") then
					show_dialog = v.r_value
				end
			end
		end
            -- dropdown menu was used; provided the dialog exists (and it's not the "New dialog" option)
	    -- (if a new dialog was added using the "+" button, fields.d_id gets set accordingly)
            elseif(fields.d_id and fields.d_id ~= show_dialog and dialog.n_dialogs[fields.d_id]) then
                show_dialog = fields.d_id
            -- in edit mode: prev_dialog_../next_dialog_.. was selected
            else
                for k,v in pairs(dialog.n_dialogs) do
                    if(fields["prev_dialog_"..k]) then
                        show_dialog = k
                    elseif(fields["next_dialog_"..k]) then
                        show_dialog = k
	            end
	        end
	    end
            yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = show_dialog})
	    -- no option was selected - so we need to end this here
            return
	end
end


-- helper function for
-- 	yl_speak_up.get_fs_talkdialog and
-- 	yl_speak_up.check_and_add_as_generic_dialog
-- find the dialog with d_sort == 0 or lowest number
yl_speak_up.get_start_dialog_id = function(dialog)
	if(not(dialog) or not(dialog.n_dialogs)) then
		return nil
	end
	-- Find the dialog with d_sort = 0 or alternatively with the lowest number
	local lowest_sort = nil
	local d_id = nil
	for k, v in pairs(dialog.n_dialogs) do
		local nr = tonumber(v.d_sort)
		if(not(lowest_sort) or (nr and nr >= 0 and nr < lowest_sort)) then
			lowest_sort = nr
			d_id = k
		end
	end
	return d_id
end


-- recursion_depth is increased each time autoanswer is automaticly selected
yl_speak_up.get_fs_talkdialog = function(player, n_id, d_id, alternate_text, recursion_depth)
    local pname = player:get_player_name()
    local dialog = yl_speak_up.speak_to[pname].dialog
    local context_d_id = yl_speak_up.speak_to[pname].d_id
    local active_dialog

    if not player and not player:is_player() then
        minetest.log(
            "action",
            "[MOD] yl_speak_up: User " ..
                pname ..
                    " talked to unconfigured NPC with ID n_" ..
                        n_id .. ", position of user was " .. minetest.pos_to_string(player:get_pos(), 0)
        )
        return yl_speak_up.get_error_message()
    end

    -- currently no trade running (we're editing options)
    yl_speak_up.trade[pname] = nil
    yl_speak_up.speak_to[pname].trade_id = nil

    --[[ If we have an explicit call for a certain d_id, we grab it from parameters. 
    If not, we grab in from context. 
    When neither are present, we grab it from d_sort
    ]]--
    
    local c_d_id
    -- the generic start dialog contains only those options that are generic;
    -- choose the right start dialog of the NPC
    if(d_id ~= nil and d_id ~= "d_generic_start_dialog") then
        active_dialog = dialog.n_dialogs[d_id]
        c_d_id = d_id
    elseif(d_id and d_id ~= "d_generic_start_dialog" and yl_speak_up.speak_to[pname].d_id ~= nil) then
        c_d_id = yl_speak_up.speak_to[pname].d_id
        active_dialog = dialog.n_dialogs[c_d_id]
    elseif dialog.n_dialogs ~= nil then
        -- Find the dialog with d_sort = 0
	c_d_id = yl_speak_up.get_start_dialog_id(dialog)
	if(c_d_id) then
		active_dialog = dialog.n_dialogs[c_d_id]
	end
    else
	-- it may be possible that this player can initialize this npc
        minetest.log(
            "action",
            "[MOD] yl_speak_up: User " ..
                pname ..
                    " talked to unconfigured NPC with ID n_" ..
                        n_id .. ", position of user was " .. minetest.pos_to_string(player:get_pos(), 0)
        )
	-- this is the initial config
	-- (input ends up at yl_speak_up.input_talk and needs to be rerouted)
	return yl_speak_up.get_fs_initial_config(player, n_id, d_id, true)
    end

    if c_d_id == nil then return yl_speak_up.get_error_message() end

    yl_speak_up.speak_to[pname].d_id = c_d_id

    -- Now we have a dialog to display to the user

    -- do not crash in case of error
    if(not(active_dialog)) then
	return "size[6,2]"..
		"label[0.2,0.5;Ups! Something went wrong. Please try again.]"
    end

    -- Is the player working on this particular npc?
    local edit_mode = (yl_speak_up.edit_mode[pname] == yl_speak_up.speak_to[pname].n_id)

    -- evaluate the preconditions of each option and check if the option can be offered
    local allowed = yl_speak_up.calculate_displayable_options(pname, active_dialog.d_options, edit_mode,
			-- avoid loops by limiting max recoursion depths for autoanswers
			(recursion_depth < yl_speak_up.max_allowed_recursion_depth))
    -- abort here if needed - the autoanswer/autoselection did choose an option for us alread
    if(not(edit_mode) and allowed and allowed["autoanswer"] and allowed["autoanswer"] ~= "") then
	-- no actions shall be executed
	local o_id = allowed["autoanswer"]
	local effects = active_dialog.d_options[o_id].o_results
	-- 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 = yl_speak_up.speak_to[pname].d_id
        end
	-- show the new target dialog and exit
	-- the recursion_depth will be increased by one (we did autoselect here and need to
	-- avoid infinite loops)
        return yl_speak_up.get_fs_talkdialog(player, n_id, target_dialog, res.alternate_text,
		recursion_depth + 1)
    end

    -- is the player comming back from trying to offer something to the NPC?
    -- And is the NPC trying to return the item?
    if(not(edit_mode) and d_id == "d_got_item") then
	local pname = player:get_player_name()
	local trade_inv = minetest.get_inventory({type="detached", name="yl_speak_up_player_"..pname})
	if(not(trade_inv:is_empty("npc_wants"))) then
		return "formspec_version[1]"..
			yl_speak_up.show_fs_simple_deco(8, 2.5)..
			"label[0.5,0.5;"..
			minetest.formspec_escape(dialog.n_npc or "- ? -")..
			" does not seem to be intrested in that.\n"..
			"Please take your item back and try something else.]"..
			"button[3.5,1.5;1.5,1.0;show_player_offers_item;Ok]"
	end
    end

    yl_speak_up.speak_to[pname].allowed = allowed


	local pname_for_old_fs = yl_speak_up.get_pname_for_old_fs(pname)
	local fs_version = yl_speak_up.fs_version[pname]
	local formspec = {}
	local h

	-- this is used to build a list of all available dialogs for a dropdown menu in edit mode
	-- (only relevant in edit mode)
        local dialog_list = yl_speak_up.text_new_dialog_id
	-- find the right index for the dialog_list dropdown above
	local d_id_to_dropdown_index = {}

	-- allow to change skin, wielded items etc.
	if(edit_mode) then
		table.insert(formspec, "button[15.75,3.5;3.5,0.9;edit_skin;Edit Skin]")
	end

	-- display the window with the text the NPC is saying
	if(edit_mode and dialog and dialog.n_dialogs) then
            -- sort all dialogs by d_sort
            local sorted_list = yl_speak_up.get_sorted_options(dialog.n_dialogs, "d_sort")
	    -- add buttons for previous/next dialog
            for i, d in ipairs(sorted_list) do
                -- build the list of available dialogs for the dropdown list(s)
                dialog_list = dialog_list..","..minetest.formspec_escape(d)
		if(d == c_d_id) then
			local prev_dialog = tostring(minetest.formspec_escape(sorted_list[i-1]))
			yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
				"button", "8.5,4.0;2,0.9", "prev_dialog_"..prev_dialog,
				"<",
				"Go to previous dialog "..prev_dialog..".",
				(sorted_list[ i-1 ]))
			local next_dialog = tostring(minetest.formspec_escape(sorted_list[i+1]))
			yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
				"button", "11,4.0;2,0.9", "next_dialog_"..next_dialog,
				">",
				"Go to next dialog "..next_dialog..".",
				(sorted_list[ i+1 ]))
                end
                d_id_to_dropdown_index[d] = i + 1
            end

	    table.insert(formspec, "label[0.2,4.6;Dialog:]") -- "..minetest.formspec_escape(c_d_id)..":]")
	    table.insert(formspec, "dropdown[3.0,4.0;5,1;d_id;"..dialog_list..";"..
			d_id_to_dropdown_index[c_d_id]..",]")
	    table.insert(formspec, "tooltip[3.0,4.0;5,1;"..
			"Select the dialog you want to edit. Currently, dialog "..c_d_id..
				" is beeing displayed.;#FFFFFF;#000000]")

	    yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
			"button", "13.9,4.0;1,0.9", "show_new_dialog",
			"+",
			"Create a new dialog.",
			true)
	    yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
			"button", "13.4,0.3;2,0.9", "button_edit_name_and_description",
			"Edit",
			"Edit name and description of your NPC.",
			true)
	    yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
			"button", "15.7,0.3;2,0.9", "button_save_dialog",
			"Save",
			"Save this dialog.",
			true)

            table.insert(formspec, "textarea[0.2,5;19.6,17.8;d_text;;"..
			minetest.formspec_escape(active_dialog.d_text)..
			"]")
	end

	-- we are finished with adding buttons and text etc. to the left side of the formspec
	local left_window_fs = table.concat(formspec, "\n")
	-- empty formspec for the bottom part
	formspec = {}

        h = -0.8

	-- allow to delete entries that have no options later on
	local anz_options = 0
        -- Let#s sort the options by o_sort
        if active_dialog ~= nil and active_dialog.d_options ~= nil then
            local sorted_o_list = yl_speak_up.get_sorted_options(active_dialog.d_options, "o_sort")
            for _, sb_v in ipairs(sorted_o_list) do
               anz_options = anz_options + 1
            end

            for _, s_o_id in ipairs(sorted_o_list) do
		local sb_v = active_dialog.d_options[s_o_id]
		local oid = minetest.formspec_escape(sb_v.o_id)
                -- in edit_mode: show all options
		if(edit_mode and yl_speak_up.old_fs_version_show_line(pname_for_old_fs)) then
			local offset = 0.0
			local field_length = 44.4
			if(pname_for_old_fs) then
				offset = 0.7
				field_length = 42.4
			end
			h = h + 1
			-- add a button "o_<nr>:" that leads to an edit formspec for this option
			yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
				"button", tostring(2.3+offset).."," .. h .. ";2,0.9", "edit_option_" .. oid,
				oid,
				"Edit target dialog, pre(C)onditions and (Ef)fects for option "..oid..".",
				true)
                    -- find the right target dialog for this option (if it exists):
		    local target_dialog = nil
                    local results = active_dialog.d_options[sb_v.o_id].o_results
		    -- has this option more results/effects than just switching to another dialog?
		    local has_other_results = false
		    if(results ~= nil) then
                        for k, v in pairs(results) do
                            if v.r_type == "dialog" and dialog.n_dialogs[v.r_value] ~= nil then
			        -- there may be more than one in the data structure
                                target_dialog = v.r_value
                            elseif v.r_type ~= "dialog" then
                                has_other_results = true
                            end
                        end
                    end
		        -- add a button "-> d_<nr>" that leads to the target dialog (if one is set)
			-- selecting an option this way MUST NOT execute the pre(C)onditions or (Ef)fects!
			yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
				"button", tostring(9.0+offset).."," .. h .. ";1,0.9", "button_" .. oid,
				"->",
				"Go to target dialog "..minetest.formspec_escape(target_dialog or "")..
					" that will be shown when this option ("..oid..") is selected.",
				(target_dialog))

			-- allow to set a new target dialog
			table.insert(formspec, "dropdown["..tostring(4.4+offset)..","..h..";4.7,1;d_id_"..
					oid..";"..
				dialog_list..";"..
				minetest.formspec_escape(d_id_to_dropdown_index[(target_dialog or "?")] or "0")..",]")
			-- add a tooltip "Change target dialog"
			table.insert(formspec, "tooltip[4.4,"..h..";4.7,1;"..
				"Change target dialog for option "..oid..".;#FFFFFF;#000000]")

			-- are there any prerequirements?
			local prereq = active_dialog.d_options[sb_v.o_id].o_prerequisites
			yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
				"button", tostring(0.5+offset).."," .. h .. ";0.5,0.9", "conditions_"..oid,
				"C",
				"There are pre(C)onditions required for showing this option. Display them.",
				(prereq and next(prereq)))

			yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
				"button", tostring(1.6+offset).."," .. h .. ";0.6,0.9", "effects_"..oid,
				"Ef",
				"There are further (Ef)fects (apart from switching\n"..
					"to a new dialog) set for this option. Display them.",
				(has_other_results))

			-- are there any actions defined?
			local actions = active_dialog.d_options[sb_v.o_id].actions
			yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
				"button", tostring(1.1+offset).."," .. h .. ";0.5,0.9", "actions_"..oid,
				"A",
				"There is an (A)ction (i.e. a trade) that will happen\n"..
					"when switching to a new dialog. Display actions and\n"..
					"trade of this option.",
				(actions and next(actions)))

			-- show the actual text for the option
			yl_speak_up.add_formspec_element_with_tooltip_if(formspec,
				"field", tostring(9.9+offset).."," .. h .. ";"..
					 tostring(field_length)..",0.9",
				"text_option_" .. oid,
				";"..minetest.formspec_escape(sb_v.o_text_when_prerequisites_met),
				"Edit the text that is displayed on button "..oid..".",
				true)

		-- normal mode: show an option if the prerequirements (if any are defined) are met
		elseif(not(edit_mode)) then
			local t = "- no text given -"
			local t_alt = nil
			-- the preconditions are fulfilled; showe the option
			if(allowed[sb_v.o_id] == true) then
				-- replace $NPC_NAME$ etc.
				t = minetest.formspec_escape(yl_speak_up.replace_vars_in_text(
					sb_v.o_text_when_prerequisites_met, dialog, pname))
			-- precondition not fulfilled? the option shall be hidden
			elseif(sb_v.o_hide_when_prerequisites_not_met == "true") then
				-- show nothing; t_alt remains nil
				t = nil
			-- precondition not fulfilled? the option shall be greyed out
			-- default to greyed out (this option cannot be selected)
			elseif(sb_v.o_grey_when_prerequisites_not_met == "true") then
				local text = sb_v.o_text_when_prerequisites_not_met
				if(not(text) or text == "") then
					text = t or yl_speak_up.message_button_option_prerequisites_not_met_default
				end
				t = nil
				-- replace $NPC_NAME$ etc.
				t_alt = minetest.formspec_escape(yl_speak_up.replace_vars_in_text(
					text, dialog, pname))
			elseif(sb_v.o_grey_when_prerequisites_not_met == "false"
			   and sb_v.o_text_when_prerequisites_not_met ~= "") then
				-- show in normal coor
				t = minetest.formspec_escape(yl_speak_up.replace_vars_in_text(
					sb_v.o_text_when_prerequisites_not_met, dialog, pname))
			end
			if(t or t_alt) then
				-- actually show the button
				h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
					"button_" .. oid,
					t,
					t,
					(t and not(t_alt)),
					t_alt,
					nil, pname_for_old_fs)
			end
		end
            end
        end

	-- with automatic selection from the start dialog, it is possible that the
	-- real start dialog is never shown; thus, add those buttons which need to
	-- be shown just once to all dialogs with is_a_start_dialog set
	local is_a_start_dialog = (active_dialog and active_dialog.d_sort
				   and (tonumber(active_dialog.d_sort) == 0
				     or active_dialog.is_a_start_dialog))
	-- add a "I want to give you something" button to the first dialog if the NPC accepts items
	if(is_a_start_dialog) then
		local offer_item_add_text = ""
		if(edit_mode) then
			offer_item_add_text = minetest.formspec_escape("[dialog d_got_item] -> ")
		end
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"player_offers_item",
			"If you want to give something (items) to this NPC\n"..
				"- either because he requested it or as a present -\n"..
				"click here. The NPC will return items he doesn't want.",
			offer_item_add_text.."I want to give you something.",
			-- show this in edit mode and when the NPC actually accepts items
			(edit_mode or dialog.n_dialogs["d_got_item"]), nil, nil, pname_for_old_fs)
	end


	-- If in edit mode, add new menu entries: "add new options", "end edit mode" and what else is needed.
	if(edit_mode) then
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"add_option",
			-- chat option: "Add a new answer/option to this dialog."
			"Adds a new option to this dialog. You can delete options via the option edit menu.",
			"Add a new option/answer to this dialog. You can delete options via the option "..
				"edit menu.",
			-- the amount of allowed options/answers has been reached
			(anz_options < yl_speak_up.max_number_of_options_per_dialog),
			"Maximum number of allowed answers/options reached. No further options/answers "..
				"can be added.", nil, pname_for_old_fs)

		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"delete_this_empty_dialog",
			-- chat option: "Delete this dialog."
			"Dialogs can only be deleted when they are empty and have no more "..
				"options/answers. This is the case here, so the dialog can be deleted.",
			"Delete this empty dialog.",
			(active_dialog and active_dialog.d_text == "" and anz_options == 0),
			-- (but only show this option if the dialog is empty)
			"If you want to delete this dialog, you need to delete all options and its "..
				"text first.", nil, pname_for_old_fs)

		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"show_what_points_to_this_dialog",
			-- chat option: "Show what points to this dialog."
			"Show which other dialog options or failed actions\n"..
				"or effects lead the player to this dialog here.",
			"Show what points to this dialog.",
			-- there is no alternate text to show
			true, nil, nil, pname_for_old_fs)

		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"make_first_option",
			-- chat option: "Make this dialog the first one shown when starting to talk."
			"The NPC has to start with one dialog when he is right-clicked. "..
				"Make this dialog the one shown.",
			"Make this dialog the first one shown when starting a conversation.",
			(active_dialog and active_dialog.d_sort and tonumber(active_dialog.d_sort) ~= 0),
			-- (but only show this option if it's not already the first one)
			"This dialog will be shown whenever a conversation is started.", nil,pname_for_old_fs)

		local b_text = "Turn this into"
		if(is_a_start_dialog) then
			b_text = "This shall no longer be"
		end
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"turn_into_a_start_dialog",
			"With automatic selection of options, it is possible that the real\n"..
				"start dialog will never be shown to the player. However, we need\n"..
				"to add some buttons to that start dialog for i.e. giving items\n"..
				"to the NPC and for trading. Therefore, dialogs can be marked as\n"..
				"*a* start dialog so that these buttons will be added to those dialogs.",
			b_text.." *a* start dialog where buttons for trade etc. are shown.",
			not(active_dialog and active_dialog.d_sort and tonumber(active_dialog.d_sort) == 0),
			"The start dialog automaticly counts as *a* start dialog where buttons for "..
				"trade etc. are shown.", nil, pname_for_old_fs)

		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"show_inventory",
			"Access and manage the inventory of the NPC. This is used for adding trade "..
				"items, getting collected payments and managing quest items.",
			"Show your inventory (only accessible to owner)!",
			true, nil, nil, pname_for_old_fs)


		-- chat option: Mute/Unmute NPC
		local obj = yl_speak_up.speak_to[pname].obj
		-- some precautions - someone else might have eliminated the NPC in the meantime
		local luaentity = nil
		if(obj) then
			luaentity = obj:get_luaentity()
		end
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"mute_npc",
			-- chat option: mute the NPC
			"The NPC will no longer show his dialogs when he is right-clicked. This is "..
				"useful while you edit the NPC and don't want players to see "..
				"unfinished entries and/or quests.",
			"State: Not muted. Stop talking to other players while I give you new orders.",
			(luaentity and luaentity.yl_speak_up.talk), nil, nil, pname_for_old_fs)
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"un_mute_npc",
			-- unmute the NPC
			"The NPC will show his dialogs to other players when he is right-clicked. "..
				"This is the normal mode of operation. Choose this when you are "..
				"finished editing.",
			"State: You are currently muted. Talk to anyone again who wants to talk to you.",
			-- the NPC has to be there
			(luaentity and not(luaentity.yl_speak_up.talk)), nil, nil, pname_for_old_fs)


		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"button_end_edit_mode",
			"Ends edit mode. From now on, your NPC will talk to you like he talks to other "..
				"players. You can always give him new orders by entering edit mode again.",
			-- chat option:"That was all. I'm finished with giving you new orders. Remember them!"
			"That was all. I'm finished with giving you new orders. Remember them!",
			true, nil, true, pname_for_old_fs) -- is button_exit

	-- Offer to enter edit mode if the player has the npc_talk_owner priv AND owns the npc.
	-- The npc_master priv allows to edit all NPC.
	elseif(yl_speak_up.may_edit_npc(player, n_id)) then
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"button_start_edit_mode",
			"Enters edit mode. In this mode, you can edit the texts the NPC says and the "..
				"answers that can be given.",
			-- chat option: "I am your owner. I have new orders for you.
			"I am your owner. I have new orders for you.",
			true, nil, true, pname_for_old_fs) -- is button_exit
	end

	-- add a Let's trade button to the first dialog if the NPC has trades
	if(is_a_start_dialog and dialog.trades) then
		local has_trades = nil
		for k, v in pairs(dialog.trades) do
			-- has the NPC any *public* trades that are not effects/results?
			if(not(v.hide) and not(v.d_id)) then
				has_trades = true
				break
			end
		end
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"show_trade_list",
			"Show a list of trades the NPC has to offer.",
			"Let's trade!",
			(has_trades), nil, nil, pname_for_old_fs)
	end

	-- we are finished with adding buttons to the bottom of the formspec
	local bottom_window_fs = table.concat(formspec, "\n")

	return yl_speak_up.show_fs_decorated(pname, edit_mode, h, alternate_text,
	                                        left_window_fs, bottom_window_fs,
						active_dialog, h)
end