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


-- helper function for yl_speak_up.fs_talkdialog
yl_speak_up.calculate_portrait = function(pname, n_id)
    local tex = yl_speak_up.speak_to[pname].textures

    local head = ""

    head = head .. "[combine:8x8:-8,-8=" .. tex[2] .. ":-40,-8=" .. tex[2]

    return head
end


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 = ""

	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
	    -- enter edit mode with that particular NPC
            yl_speak_up.edit_mode[pname] = yl_speak_up.speak_to[pname].n_id
	    -- 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
            local s = string.split(k, "_")

            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["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


function yl_speak_up.on_rightclick(self, clicker)
    --local item = clicker:get_wielded_item()
    local name = clicker:get_player_name()

    -- Take the mob only with net or lasso
    if self.owner and self.owner == name then
        if mobs:capture_mob(self, clicker, nil, 100, 100, true, nil) then
            return
        end
    end

    -- protect npc with mobs:protector
    if mobs:protect(self, clicker) then
        return
    end

    -- bring up the dialog options
    if clicker then
        yl_speak_up.talk(self, clicker)
        return
    end
end

function yl_speak_up.on_spawn(self)
    --Let's assign an ID

    local m_talk = yl_speak_up.talk_after_spawn or true
    local m_id = yl_speak_up.number_of_npcs + 1

    yl_speak_up.number_of_npcs = m_id
    yl_speak_up.modstorage:set_int("amount", m_id)

    yl_speak_up.mob_table[m_id] = "yl_speak_up:test_npc"

    self.yl_speak_up = {
        talk = m_talk,
        id = m_id,
        textures = self.textures
    }

    --Let's protect it
    self.protected = true
    self.tamed = true
    self.object:set_armor_groups({immortal = 100})

    minetest.log(
        "action",
        "[MOD] yl_speak_up: NPC with ID n_" ..
            self.yl_speak_up.id .. " spawned at " .. minetest.pos_to_string(self.object:get_pos(), 0)
    )

    --Let's do it only once
    return true
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

    if d_id ~= nil then
        active_dialog = dialog.n_dialogs[d_id]
        c_d_id = d_id
    elseif 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
        local lowest_sort = nil
        for k, v in pairs(dialog.n_dialogs) do
            if tonumber(v.d_sort) ~= nil then
                if not lowest_sort or tonumber(v.d_sort) < tonumber(lowest_sort) or v.d_sort == "0" then
                    if tonumber(v.d_sort) >= 0 then
                        lowest_sort = v.d_sort
                        active_dialog = v
                        c_d_id = k
                    end
                end
            end
        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 "size[8,1.5]"..
			"label[0.2,-0.2;"..
			minetest.formspec_escape(dialog.n_npc or "- ? -")..
			" does not seem to be intrested.\n"..
			"Please take your item back and try something else.]"..
			"button[2,1.0;1.5,0.9;show_player_offers_item;Ok]"
	end
    end

    yl_speak_up.speak_to[pname].allowed = allowed

    local portrait = yl_speak_up.calculate_portrait(pname, n_id)

    local formspec_v = minetest.get_player_information(pname).formspec_version
    local protocol_v = minetest.get_player_information(pname).protocol_version
    local formspec = {}
    local h

    -- show who owns the NPC (and is thus more or less responsible for what it says)
    local owner_info = ""
    if(yl_speak_up.npc_owner[ n_id ]) then
        owner_info = "\n\n(owned by "..minetest.formspec_escape(yl_speak_up.npc_owner[ n_id ])..")"
    end

    if formspec_v >= 4 then
        formspec = {
            "formspec_version[3]",
            "size[57,33]",
            "position[0,0.45]",
            "anchor[0,0.45]",
            "no_prepend[]",
            "bgcolor[#00000000;false]",
            -- Container

            "container[2,0.75]",
            -- Background

            "background[0,0;20,23;yl_speak_up_bg_dialog.png;false]",
            "background[0,24;54.5,7.5;yl_speak_up_bg_dialog.png;false]",
            -- Frame Dialog

            "image[-0.25,-0.25;1,1;yl_speak_up_bg_dialog_tl.png]",
            "image[-0.25,22.25;1,1;yl_speak_up_bg_dialog_bl.png]",
            "image[19.25,-0.25;1,1;yl_speak_up_bg_dialog_tr.png]",
            "image[19.25,22.25;1,1;yl_speak_up_bg_dialog_br.png]",
            "image[-0.25,0.75;1,21.5;yl_speak_up_bg_dialog_hl.png]",
            "image[19.25,0.75;1,21.5;yl_speak_up_bg_dialog_hr.png]",
            "image[0.75,-0.25;18.5,1;yl_speak_up_bg_dialog_vt.png]",
            "image[0.75,22.25;18.5,1;yl_speak_up_bg_dialog_vb.png]",
            -- Frame Options

            "image[-0.25,23.75;1,1;yl_speak_up_bg_dialog_tl.png]",
            "image[-0.25,30.75;1,1;yl_speak_up_bg_dialog_bl.png]",
            "image[53.75,23.75;1,1;yl_speak_up_bg_dialog_tr.png]",
            "image[53.75,30.75;1,1;yl_speak_up_bg_dialog_br.png]",
            "image[-0.25,24.75;1,6;yl_speak_up_bg_dialog_hl.png]",
            "image[53.75,24.75;1,6;yl_speak_up_bg_dialog_hr.png]",
            "image[0.75,23.75;53,1;yl_speak_up_bg_dialog_vt.png]",
            "image[0.75,30.75;53,1;yl_speak_up_bg_dialog_vb.png]",
            "style_type[button;bgcolor=#a37e45]",
            "style_type[button_exit;bgcolor=#a37e45]", -- Dialog

            --[[
            "background[-1,-1;22,25;yl_speak_up_bg_dialog2.png;false]",
            "background[-1,23;58,10;yl_speak_up_bg_dialog2.png;false]",
            "style_type[button;bgcolor=#a37e45]",
            ]]-- 
            "label[0.3,0.6;",
            minetest.formspec_escape(dialog.n_npc),
            "]",
            "label[0.3,1.8;",
            minetest.formspec_escape(dialog.n_description)..owner_info,
            "]",
            "image[15.5,0.5;4,4;",
            portrait,
            "]",
        }

	-- 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 and sorted_list[ i-1 ]) then
		    local prev_dialog = minetest.formspec_escape(sorted_list[i-1])
                    table.insert(formspec, "button[8.5,4.0;2,0.9;prev_dialog_"..prev_dialog..";<]")
                    table.insert(formspec, "tooltip[prev_dialog_"..prev_dialog..
		        ";Go to previous dialog "..prev_dialog..".]")
                end
                if(d == c_d_id and  sorted_list[ i+1 ]) then
		    local next_dialog = minetest.formspec_escape(sorted_list[i+1])
                    table.insert(formspec, "button[11,4.0;2,0.9;next_dialog_"..next_dialog..";>]")
                    table.insert(formspec, "tooltip[next_dialog_"..next_dialog..
			";Go to next dialog "..next_dialog..".]")
                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]")

            -- add a "+" button for creating a new dialog
            table.insert(formspec, "button[13.9,4.0;1,0.9;show_new_dialog;+]")
            table.insert(formspec, "tooltip[show_new_dialog;Create a new dialog.]")

            -- allow to edit name and description of the NPC
            table.insert(formspec, "button[13.4,0.3;2,0.9;button_edit_name_and_description;Edit]")
	    table.insert(formspec, "tooltip[button_edit_name_and_description;Edit name and description of your NPC.]")
	    table.insert(formspec, "button[15.7,0.3;2,0.9;button_save_dialog;Save]")
	    table.insert(formspec, "tooltip[button_save_dialog;Save this dialog.]")

            table.insert(formspec, "textarea[0.2,5;19.6,17.8;d_text;;")
            table.insert(formspec, minetest.formspec_escape(active_dialog.d_text))
            table.insert(formspec, "]")
	else
	    if(alternate_text) then
		alternate_text = string.gsub(alternate_text, "%$TEXT%$", active_dialog.d_text)
	    end
            -- replace $NPC_NAME$ etc.
            local t = minetest.formspec_escape(yl_speak_up.replace_vars_in_text(
				(alternate_text or active_dialog.d_text), dialog, pname))
            table.insert(formspec, "hypertext[0.2,5;19.6,17.8;d_text;<normal>")
            table.insert(formspec, t .. "\n</normal>")
            table.insert(formspec, "]")
            table.insert(formspec, "tooltip[d_text;")
            table.insert(formspec, t:trim())
            table.insert(formspec, ";#000000;#FFFFFF]")
        end

        table.insert(formspec, "scrollbaroptions[min=0;max=14;smallstep=1;largestep=2;arrows=show]")
        table.insert(formspec, "scrollbar[0.2,24.2;0.2,7;vertical;scr0;0]")
        table.insert(formspec, "scroll_container[0,24;56,7;scr0;vertical;1]")
        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_buttons = {}
            for _, ad_v in pairs(active_dialog.d_options) do
                sorted_buttons[tonumber(ad_v.o_sort)] = ad_v
		anz_options = anz_options + 1
            end

            for _, sb_v in pairs(sorted_buttons) do
		local oid = minetest.formspec_escape(sb_v.o_id)
                -- in edit_mode: show all options
		if edit_mode then
                    h = h + 1
		    -- add a button "o_<nr>:" that leads to an edit formspec for this option
                    table.insert(formspec, "button[2.3," .. h .. ";2,0.9;edit_option_" .. oid .. ";"..oid..":]")
		    -- add a tooltip "Edit target dialog, pre(C)onditions and (Ef)fects for option o_<nr>"
                    table.insert(formspec, "tooltip[edit_option_" .. oid .. ";Edit target dialog, pre(C)onditions and (Ef)fects for option "..oid..".]")

                    -- 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
		    if(target_dialog) then
		        -- add a button "-> d_<nr>" that leads to the target dialog (if one is set)
                        table.insert(formspec, "button[9.0," .. h .. ";1,0.9;button_" .. oid .. ";->]")
		        -- add a tooltip "Go to target dialog d_<nr>"
                        table.insert(formspec, "tooltip[button_" .. oid .. ";Go to target dialog "..minetest.formspec_escape(target_dialog).." that will be shown when this option ("..oid..") is selected.]")

			-- selecting an option this way MUST NOT execute the pre(C)onditions or (Ef)fects!
		    end
		    -- allow to set a new target dialog
	            table.insert(formspec, "dropdown[4.4,"..h..";4.7,1;d_id_"..oid..";"..dialog_list..";"..minetest.formspec_escape(d_id_to_dropdown_index[target_dialog] 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
		    if(prereq and next(prereq)) then
                        table.insert(formspec, "button[0.5," .. h .. ";0.5,0.9;conditions_"..oid..";C]")
		        -- label: "There are pre(C)onditions required for showing this option. Display them."
                        table.insert(formspec, "tooltip[conditions_" .. oid .. ";There are pre(C)onditions required for showing this option. Display them.]")
                    end
		    if(has_other_results) then
                        table.insert(formspec, "button[1.6," .. h .. ";0.6,0.9;effects_"..oid..";Ef]")
		        -- label: "There are further (Ef)fects (apart from switching to a new dialog)
			--         set for this option. Display them."
                        table.insert(formspec, "tooltip[effects_" .. oid .. ";"..
				"There are further (Ef)fects (apart from switching\n"..
				"to a new dialog) set for this option. Display them.]")
		    end
		    local actions = active_dialog.d_options[sb_v.o_id].actions
		    -- are there any actions defined?
                    if(actions and next(actions)) then
                        table.insert(formspec, "button[1.1," .. h .. ";0.5,0.9;effects_"..oid..";A]")
                        table.insert(formspec, "tooltip[effects_" .. oid .. ";"..
				"There is an (A)ction (i.e. a trade) that will happen\n"..
				"when switching to a new dialog. Display effects and\n"..
				"trade of this option.]")
                    end

		    -- show the actual text for the option
                    table.insert(formspec, "field[9.9," .. h .. ";44.4,0.9;text_option_" .. oid .. ";;"..
                        minetest.formspec_escape(sb_v.o_text_when_prerequisites_met).."]")
		    -- add a tooltip "Edit the text that is displayed on button o_<nr>."
                    table.insert(formspec, "tooltip[text_option_" .. oid .. ";Edit the text that is displayed on button "..oid..".]")

		-- normal mode: show an option if the prerequirements (if any are defined) are met
	        elseif allowed[sb_v.o_id] == true then
                    h = h + 1
                    -- replace $NPC_NAME$ etc.
		    local t = minetest.formspec_escape(yl_speak_up.replace_vars_in_text(
					sb_v.o_text_when_prerequisites_met, dialog, pname))
                    table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;button_" .. oid .. ";]")
                    table.insert(
                        formspec,
                        "tooltip[button_" .. oid .. ";" .. t .. "]"
                    )
                    local l = h + 0.45
                    table.insert(formspec, "label[0.7," .. l .. ";" .. t .. "]")
                else
                    if sb_v.o_hide_when_prerequisites_not_met == "true" then
                    else
                        -- replace $NPC_NAME$ etc.
		        local t = minetest.formspec_escape(yl_speak_up.replace_vars_in_text(
					sb_v.o_text_when_prerequisites_not_met, dialog, pname))
                        if
                            sb_v.o_grey_when_prerequisites_not_met == "true" and
                                sb_v.o_text_when_prerequisites_not_met == ""
                         then
                            h = h + 1
                            table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;button_" .. oid .. ";]")
                            table.insert(
                                formspec,
                                "tooltip[button_" ..
                                    oid ..
                                        ";" .. yl_speak_up.message_button_option_prerequisites_not_met_default .. "]"
                            )
                            local l = h + 0.45
                            table.insert(
                                formspec,
                                "label[0.7," ..
                                    l .. ";" .. yl_speak_up.message_button_option_prerequisites_not_met_default .. "]"
                            )
                            table.insert(formspec, "box[0.5," .. h .. ";53.8,0.9;#BBBBBB]")
                        end
                        if
                            sb_v.o_grey_when_prerequisites_not_met == "true" and
                                sb_v.o_text_when_prerequisites_not_met ~= ""
                         then
                            h = h + 1
                            table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;button_" .. oid .. ";]")
                            table.insert(
                                formspec,
                                "tooltip[button_" .. oid .. ";" .. t .. "]"
                            )
                            local l = h + 0.45
                            table.insert(
                                formspec,
                                "label[0.7," .. l .. ";" .. t .. "]"
                            )
                            table.insert(formspec, "box[0.5," .. h .. ";53.8,0.9;#BBBBBB]")
                        end
                        if
                            sb_v.o_grey_when_prerequisites_not_met == "false" and
                                sb_v.o_text_when_prerequisites_not_met == ""
                         then
                        -- no hide, no grey, no text
                        end
                        if
                            sb_v.o_grey_when_prerequisites_not_met == "false" and
                                sb_v.o_text_when_prerequisites_not_met ~= ""
                         then
                            -- no grey, but text
                            h = h + 1
                            table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;button_" .. oid .. ";]")
                            table.insert(
                                formspec,
                                "tooltip[button_" .. oid .. ";" .. t .. "]"
                            )
                            local l = h + 0.45
                            table.insert(
                                formspec,
                                "label[0.7," .. l .. ";" .. t .. "]"
                            )
                        end
                    end
                end
            end
        end

	-- add a "I want to give you something" button to the first dialog if the NPC accepts items
	if(active_dialog and active_dialog.d_sort and tonumber(active_dialog.d_sort) == 0) then
		local offer_item_add_text = ""
		if(edit_mode) then
			offer_item_add_text = minetest.formspec_escape("[dialog d_got_item] -> ")
		end
		-- show this in edit mode and when the NPC actually accepts items
		if(edit_mode or dialog.n_dialogs["d_got_item"]) then
		        h = h + 1
			table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;player_offers_item;]")
			table.insert(formspec, "tooltip[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.]")
			table.insert(formspec, "label[0.7,"..(h+0.45)..";"..offer_item_add_text..
				"I want to give you something.]")
		end
	end

	-- If in edit mode, add two new menu entries: "add new options" and "end edit mode".
	if(edit_mode) then
            -- chat option: "Add a new answer/option to this dialog."
            h = h + 1
	    if(anz_options < yl_speak_up.max_number_of_options_per_dialog) then
                table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;add_option;]")
                table.insert(formspec, "tooltip[add_option;Adds a new option to this dialog. You can "..
			"delete options via the option edit menu.]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";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
            else
                table.insert(formspec, "box[0.5,"..h..";53.8,0.9;#BBBBBB]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";Maximum number of allowed answers/options "..
			"reached. No further options/answers can be added.]")
            end

	    -- chat option: "Delete this dialog."
	    h = h + 1
	    if(active_dialog
		    and active_dialog.d_text == ""
		    and anz_options == 0) then
                table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;delete_this_empty_dialog;]")
                table.insert(formspec, "tooltip[delete_this_empty_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.]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";Delete this empty dialog.]")
	    -- (but only show this option if the dialog is empty)
            else
                table.insert(formspec, "box[0.5,"..h..";53.8,0.9;#BBBBBB]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";If you want to delete this dialog, you "..
			"need to delete all options and its text first.]")
            end

	    -- chat option: "Show what points to this dialog."
	    h = h + 1
            table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;show_what_points_to_this_dialog;]")
            table.insert(formspec, "tooltip[show_what_points_to_this_dialog;"..
			"Show which other dialog options or failed actions\n"..
			"or effects lead the player to this dialog here.]")
            table.insert(formspec, "label[0.7,"..(h+0.45)..";Show what points to this dialog.]")

	    -- chat option: "Make this dialog the first one shown when starting to talk."
            h = h + 1
	    if(active_dialog and active_dialog.d_sort and tonumber(active_dialog.d_sort) ~= 0) then
                table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;make_first_option;]")
                table.insert(formspec, "tooltip[make_first_option;The NPC has to start with one dialog "..
			"when he is right-clicked. Make this dialog the one shown.]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";Make this dialog the first one shown "..
			"when starting a conversation.]")
	    -- (but only show this option if it's not already the first one)
            else
                table.insert(formspec, "box[0.5,"..h..";53.8,0.9;#BBBBBB]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";This dialog will be shown whenever "..
			"a conversation is started.]")
            end

	    -- access the inventory of the NPC
	    h = h + 1
            table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;show_inventory;]")
            table.insert(formspec, "tooltip[show_inventory;Access and manage the inventory of the NPC. "..
			"This is used for adding trade items, getting collected payments and managing "..
			"quest items.]")
            table.insert(formspec, "label[0.7,"..(h+0.45)..";"..
			"Show your inventory (only accessible to owner)!]")

	    -- chat option: Mute/Unmute NPC
            h = h + 1
            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
	    if(luaentity and luaentity.yl_speak_up.talk) then
                table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;mute_npc;]")
                table.insert(formspec, "tooltip[mute_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.]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";State: Not muted. Stop talking to other "..
			"players while I give you new orders.]")
            elseif(luaentity) then
		-- unmute the NPC
                table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;un_mute_npc;]")
                table.insert(formspec, "tooltip[un_mute_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.]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";State: You are currently muted. Talk to "..
			"anyone again who wants to talk to you.]")
            end

            -- chat option: "That was all. I'm finished with giving you new orders. Remember them!"
            h = h + 1
            table.insert(formspec, "button_exit[0.5," .. h .. ";53.8,0.9;button_end_edit_mode;]")
            table.insert(formspec, "tooltip[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.]")
            table.insert(formspec, "label[0.7,"..(h+0.45)..";That was all. I'm finished with giving you new orders. Remember them!]")

        -- 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
            -- chat option: "I am your owner. I have new orders for you.
            h = h + 1
            table.insert(formspec, "button_exit[0.5," .. h .. ";53.8,0.9;button_start_edit_mode;]")
            table.insert(formspec, "tooltip[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.]")
            table.insert(formspec, "label[0.7,"..(h+0.45)..";I am your owner. I have new orders for you.]")
        end

	-- add a Let's trade button to the first dialog if the NPC has trades
	if(active_dialog and active_dialog.d_sort and tonumber(active_dialog.d_sort) == 0
	  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
	    if(has_trades) then
	        h = h + 1
                table.insert(formspec, "button[0.5," .. h .. ";53.8,0.9;show_trade_list;]")
                table.insert(formspec, "tooltip[show_trade_list;Show a list of trades the NPC has to offer.]")
                table.insert(formspec, "label[0.7,"..(h+0.45)..";Let's trade!]")
	    end
	end


        h = h + 1
        table.insert(formspec, "button_exit[0.5," .. h .. ";53.8,0.9;button_exit;]")
        table.insert(formspec, "tooltip[button_exit;" .. yl_speak_up.message_button_option_exit .. "]")
        local l = h + 0.45
        table.insert(formspec, "label[0.7," .. l .. ";" .. yl_speak_up.message_button_option_exit .. "]")

        table.insert(formspec, "scroll_container_end[]")

        table.insert(formspec, "container_end[]")

    -- if the player has an older formspec version
    -- TODO: the version for older formspec versions lacks quite a lot - in particular regarding editing
    else
        minetest.log(
            "info",
            "[MOD] yl_speak_up: User " .. pname .. " talked to NPC ID n_" .. n_id .. " with an old formspec version!"
        )

        local upgrade_warning = ""
        local max_number_of_buttons = yl_speak_up.max_number_of_buttons
        local start_index = yl_speak_up.speak_to[pname].option_index

        if formspec_v < 3 or protocol_v < 39 then
            local warn = {
                "box[0.3,3;15,2;red]",
                "label[0.7,3.2;",
                yl_speak_up.text_version_warning,
                "]"
            }
            upgrade_warning = table.concat(warn, "")
        end

        if(alternate_text) then
	    alternate_text = string.gsub(alternate_text, "%$TEXT%$", active_dialog.d_text)
        end
        -- replace $NPC_NAME$ etc.
        local t = minetest.formspec_escape(yl_speak_up.replace_vars_in_text(
				(alternate_text or active_dialog.d_text), dialog, pname))
        formspec = {
            "formspec_version[1]",
            "size[48,28]",
            "position[0,0.45]",
            "anchor[0,0.45]",
            "no_prepend[]",
            "bgcolor[#00000000;false]",
            -- Container

            "container[2,0.75]",
            -- Background

            "background[0,0;20,17;yl_speak_up_bg_dialog.png]",
            "background[0,18;45,8;yl_speak_up_bg_dialog.png]",
            -- Frame Dialog

            "image[-0.35,-0.35;1,1;yl_speak_up_bg_dialog_tl.png]",
            "image[-0.35,16.25;1,1;yl_speak_up_bg_dialog_bl.png]",
            "image[19.35,-0.35;1,1;yl_speak_up_bg_dialog_tr.png]",
            "image[19.35,16.25;1,1;yl_speak_up_bg_dialog_br.png]",
            "image[-0.35,0.35;1,19.5;yl_speak_up_bg_dialog_hl.png]",
            "image[19.35,0.35;1,19.5;yl_speak_up_bg_dialog_hr.png]",
            "image[0.35,-0.35;24.5,1;yl_speak_up_bg_dialog_vt.png]",
            "image[0.35,16.25;24.5,1;yl_speak_up_bg_dialog_vb.png]",
            -- Frame Options

            "image[-0.35,17.65;1,1;yl_speak_up_bg_dialog_tl.png]",
            "image[-0.35,25.35;1,1;yl_speak_up_bg_dialog_bl.png]",
            "image[44.35,17.65;1,1;yl_speak_up_bg_dialog_tr.png]",
            "image[44.35,25.35;1,1;yl_speak_up_bg_dialog_br.png]",
            "image[-0.35,18.35;1,8.5;yl_speak_up_bg_dialog_hl.png]",
            "image[44.35,18.35;1,8.5;yl_speak_up_bg_dialog_hr.png]",
            "image[0.35,17.65;56.5,1;yl_speak_up_bg_dialog_vt.png]",
            "image[0.35,25.35;56.5,1;yl_speak_up_bg_dialog_vb.png]",
            -- Upgrade Warning

            upgrade_warning,
            -- Dialog

            "label[0.3,0.6;",
            minetest.formspec_escape(dialog.n_npc),
            "]",
            "label[0.3,1.8;",
            minetest.formspec_escape(dialog.n_description),
            "]",
            "image[15.5,0.5;4,4;",
            portrait,
            "]",
            "textarea[0.5,5;19.6,13.5;;;",
            t .. "\n",
            "]",
            "container[0,18]"
        }
        h = -1

        if active_dialog ~= nil and active_dialog.d_options ~= nil then
            -- Let's sort the options by o_sort.
            local sorted_buttons = {}
            for _, ad_v in pairs(active_dialog.d_options) do
                sorted_buttons[tonumber(ad_v.o_sort)] = ad_v
            end

            if #sorted_buttons > max_number_of_buttons then
                -- Generate arrows
                table.insert(formspec, "button[0.1,0;1,0.9;button_down;^]")
                table.insert(formspec, "button[0.1,7.0;1,0.9;button_up;v]")
            end

            local counter = 1

            for _, sb_v in pairs(sorted_buttons) do
                local end_index = start_index + max_number_of_buttons
                if counter >= start_index and counter < end_index then
                    local oid = minetest.formspec_escape(sb_v.o_id)
                    if allowed[sb_v.o_id] == true then
                        h = h + 1
                        table.insert(
                            formspec,
                            "button[1," ..
                                h .. ";44,0.9;button_" .. oid .. ";" .. minetest.formspec_escape(sb_v.o_text_when_prerequisites_met) .. "]"
                        )
                        table.insert(
                            formspec,
                            "tooltip[button_" .. oid .. ";" .. minetest.formspec_escape(sb_v.o_text_when_prerequisites_met) .. "]"
                        )
                    else
                        if sb_v.o_hide_when_prerequisites_not_met == "true" then
                            -- hide! Nothing to do
                        else
                            if
                                sb_v.o_grey_when_prerequisites_not_met == "true" and
                                    sb_v.o_text_when_prerequisites_not_met == ""
                             then
                                h = h + 1
                                local l = h - 0.2
                                table.insert(formspec, "box[1," .. l .. ";43,1;#BBBBBB]")
                                table.insert(
                                    formspec,
                                    "label[3," ..
                                        h ..
                                            ";" ..
                                                yl_speak_up.message_button_option_prerequisites_not_met_default .. "]"
                                )
                            end
                            if
                                sb_v.o_grey_when_prerequisites_not_met == "true" and
                                    sb_v.o_text_when_prerequisites_not_met ~= ""
                             then
                                h = h + 1
                                local l = h - 0.2
                                table.insert(formspec, "box[1," .. l .. ";43,1;#BBBBBB]")
                                table.insert(
                                    formspec,
                                    "label[3," ..
                                        h ..
                                            ";" ..
                                                yl_speak_up.message_button_option_prerequisites_not_met_default ..
                                                    " : " .. minetest.formspec_escape(sb_v.o_text_when_prerequisites_not_met) .. "]"
                                )
                            end
                            if
                                sb_v.o_grey_when_prerequisites_not_met == "false" and
                                    sb_v.o_text_when_prerequisites_not_met == ""
                             then
                            -- no hide, no grey, no text
                            end
                            if
                                sb_v.o_grey_when_prerequisites_not_met == "false" and
                                    sb_v.o_text_when_prerequisites_not_met ~= ""
                             then
                                h = h + 1
                                table.insert(
                                    formspec,
                                    "button[1," ..
                                        h ..
                                            ";44,0.9;button_" ..
                                                oid .. ";" .. minetest.formspec_escape(sb_v.o_text_when_prerequisites_not_met) .. "]"
                                )
                                table.insert(
                                    formspec,
                                    "tooltip[button_" ..
                                        oid .. ";" .. minetest.formspec_escape(sb_v.o_text_when_prerequisites_not_met) .. "]"
                                )
                            end
                        end
                    end
                end

                counter = counter + 1
            end
        end
        h = h + 1
        table.insert(
            formspec,
            "button_exit[1," .. h .. ";44,0.9;button_exit;" .. yl_speak_up.message_button_option_exit .. "]"
        )
        table.insert(formspec, "tooltip[button_exit;" .. yl_speak_up.message_button_option_exit .. "]")

        table.insert(formspec, "container_end[]")
        table.insert(formspec, "container_end[]")
    end

    return table.concat(formspec, "")
end