-- process input from formspec created in get_fs_edit_option_dialog(..)
yl_speak_up.input_edit_option_dialog = function(player, formname, fields)
	if formname ~= "yl_speak_up:edit_option_dialog" then
		return
	end
        local pname = player:get_player_name()

	-- 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(not(edit_mode) or not(fields.o_id)) then
		return
	end
	local n_id = yl_speak_up.speak_to[pname].n_id
	local d_id = yl_speak_up.speak_to[pname].d_id
	-- this is passed on as a hidden field
	local o_id = fields.o_id

	local dialog = yl_speak_up.speak_to[pname].dialog
	local n_dialog = dialog.n_dialogs[d_id]
	local d_option = n_dialog.d_options[o_id]

	-- this meny is specific to an option for a dialog; if no dialog is selected, we really
	-- can't know what to do
	if(not(d_id)) then
		return
	end

	-- handles changes to o_text_when_prerequisites_met, target dialog, adding of a new dialog
	local result = yl_speak_up.edit_mode_apply_changes(pname, fields)
	-- if a new option was added or the target dialog of this one changed, display the right new option
	if(result and result["show_next_option"] and n_dialog.d_options[result["show_next_option"]]) then
		yl_speak_up.show_fs(player, "edit_option_dialog",
			{n_id = n_id, d_id = d_id, o_id = result["show_next_option"],
			 caller="show_next_option"})
		return
	end

	-- back to the main dialog window?
	-- (this also happens when the last option was deleted)
	if(fields.show_current_dialog or fields.quit or fields.button_exit or not(d_option) or fields.del_option) then
		yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = d_id})
		return
	end

	-- for now, there's only trade as action
	if(fields.table_of_actions) then
		local trade_id = tostring(d_id).." "..tostring(o_id)
		if(dialog.trades and dialog.trades[ trade_id ]) then
			fields.effect_show_trade = true
		else
			fields.effect_add_trade = true
		end
	end

	-- add or edit the trade associated with this dialog and option
	if(fields.effect_add_trade) then
		-- remember which option was selected
		yl_speak_up.speak_to[pname].o_id = o_id
		-- do not switch target dialog (we are in edit mode)
		yl_speak_up.speak_to[pname].target_d_id = nil
		-- create a new trade for this dialog and option - with ID "<d_id> <o_id>"
		yl_speak_up.show_fs(player, "add_trade_simple", tostring(d_id).." "..tostring(o_id))
		return

	-- the player wants to see the previous option/answer
	elseif(fields.edit_option_prev) then
		-- sort all options by o_sort
		local sorted_list = yl_speak_up.get_sorted_options(n_dialog.d_options, "o_sort")
		local o_found = o_id
		for i, o in ipairs(sorted_list) do
			if(o == o_id and sorted_list[ i-1]) then
				o_found = sorted_list[ i-1 ]
			end
		end
		-- show that dialog; fallback: show the same (o_id) again
		yl_speak_up.show_fs(player, "edit_option_dialog",
			{n_id = n_id, d_id = d_id, o_id = o_found, caller="prev option"})
		return

	-- the player wants to see the next option/answer
	elseif(fields.edit_option_next) then
		-- sort all options by o_sort
		local sorted_list = yl_speak_up.get_sorted_options(n_dialog.d_options, "o_sort")
		local o_found = o_id
		for i, o in ipairs(sorted_list) do
			if(o == o_id and sorted_list[ i+1 ]) then
				o_found = sorted_list[ i+1 ]
			end
		end
		-- show that dialog; fallback: show the same (o_id) again
		yl_speak_up.show_fs(player, "edit_option_dialog",
			{n_id = n_id, d_id = d_id, o_id = o_found, caller="next option"})
		return

	-- show the trade associated with this dialog and option
	elseif(fields.effect_show_trade) then
		-- remember which option was selected
		yl_speak_up.speak_to[pname].o_id = o_id
		-- do not switch target dialog (we are in edit mode)
		yl_speak_up.speak_to[pname].target_d_id = nil
		-- show the trade with ID "<d_id> <o_id>"
		yl_speak_up.show_fs(player, "trade_simple", tostring(d_id).." "..tostring(o_id))
		return

	-- the player clicked on a precondition
	elseif(fields.table_of_preconditions) then

	-- the player clicked on an effect
	elseif(fields.table_of_effects) then
	end

	-- if ESC is pressed or anything else unpredicted happens: go back to the main dialog edit window
	-- reason: don't loose any unsaved changes to the dialog
	yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = d_id})
end


-- edit options (not via staff but via the "I am your owner" dialog)
yl_speak_up.get_fs_edit_option_dialog = function(player, n_id, d_id, o_id)
	-- n_id, d_id and o_id have already been checked when this function is called
	local pname = player:get_player_name()
	local dialog = yl_speak_up.speak_to[pname].dialog
	local n_dialog = dialog.n_dialogs[d_id]
	local d_option = n_dialog.d_options[o_id]

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

	if(not(d_option)) then
		return "size[6,2]"..
			"label[0.2,0.5;Ups! Option "..minetest.formspec_escape(tostring(o_id))..
				" does not exist.]"..
			"button_exit[2,1.5;1,0.9;exit;Exit]"
	end
	-- are there any preconditions?
	local list_of_preconditions = ""
	local prereq = d_option.o_prerequisites
	if(prereq) then
		local sorted_key_list = yl_speak_up.sort_keys(prereq)
		for i, k in ipairs(sorted_key_list) do
			local v = prereq[ k ]
			list_of_preconditions = list_of_preconditions..
				minetest.formspec_escape(v.p_id)..",#FFFF00,"..
				minetest.formspec_escape(v.p_type)..","..
				minetest.formspec_escape(v.p_value)..","
		end
	end
	list_of_preconditions = list_of_preconditions..",#00FF00,add,Add a new pre(C)ondition"

	local list_of_actions = ""
	if(dialog.trades and dialog.trades[ tostring(d_id).." "..tostring(o_id) ]) then
		local tr = dialog.trades[ tostring(d_id).." "..tostring(o_id)]
		-- show the trade in the result/effects list
		list_of_actions = ",#FF8800,trade,"..
				-- show a reasonable overview of what is traded for what
				minetest.formspec_escape("NPC sells "..
					table.concat(tr.buy, ";").." for "..
					table.concat(tr.pay, ";"))
	else
		list_of_actions = ",#00FF00,add,Add a new (A)ction"
	end

	-- find the right target dialog for this option (if it exists)
	local target_dialog = nil
	-- and build the list of effects
	local list_of_effects = ""
	local results = d_option.o_results
	if(results) then
		local sorted_key_list = yl_speak_up.sort_keys(results)
		for i, k in ipairs(sorted_key_list) do
			local v = results[ k ]
			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
				list_of_effects = list_of_effects..
					minetest.formspec_escape(v.r_id)..",#FFFF00,"..
					minetest.formspec_escape(v.r_type)..","..
					minetest.formspec_escape(v.r_value)..","
			end
		end
	end
	list_of_effects = list_of_effects..",#00FF00,add,Add a new (Ef)fect"

	-- if no target dialog has been selected: default is to go to the dialog with d_sort 0
	if(not(target_dialog) or target_dialog == "" or not(dialog.n_dialogs[target_dialog])) then
		for d, v in pairs(dialog.n_dialogs) do
			if(v.d_sort and tonumber(v.d_sort) == 0) then
				target_dialog = d
			end
		end
	end
	-- this is the text the NPC will say in reaction to this answer
	local next_text = ""
	if(target_dialog and dialog.n_dialogs[target_dialog]) then
		next_text = dialog.n_dialogs[target_dialog].d_text
	end
	-- build the list of available dialogs for the dropdown list(s)
	local dialog_list = yl_speak_up.text_new_dialog_id
	local dialog_selected = "1"
	-- if there are dialogs defined
	if(dialog and dialog.n_dialogs) then
		-- the first entry will be "New dialog"
		local n = 1
		for k, v in pairs(dialog.n_dialogs) do
			dialog_list = dialog_list .. "," .. minetest.formspec_escape(v.d_id)
			-- which one is the current dialog?
			n = n + 1
			if(v.d_id == target_dialog) then
				dialog_selected = tostring(n)
			end
		end
	end
	if(not(target_dialog)) then
		target_dialog = "- none -"
	end

	-- offer the correct preselection for hidden/grey/show text
	local alternate_answer_option = "3"
	if(d_option.o_hide_when_prerequisites_not_met == "true") then
		alternate_answer_option = "1"
	elseif(d_option.o_grey_when_prerequisites_not_met == "true") then
		alternate_answer_option = "2"
	end

	-- can the button "prev(ious)" be shown?
	local button_prev = ""
	-- can the button "next" be shown?
	local button_next = ""
	-- sort all options by o_sort
	local sorted_list = yl_speak_up.get_sorted_options(n_dialog.d_options, "o_sort")
	local o_found = o_id
	local anz_options = 0
	for i, o in ipairs(sorted_list) do
		if(o == o_id and sorted_list[ i-1 ]) then
			button_prev = ""..
				"button[7.4,18.7;2.0,0.9;edit_option_prev;Prev]"..
				"tooltip[edit_option_prev;Go to previous option/answer "..
				"(according to o_sort).]"
		end
		if(o == o_id and  sorted_list[ i+1 ]) then
			button_next = ""..
				"button[12.0,18.7;2.0,0.9;edit_option_next;Next]"..
				"tooltip[edit_option_next;Go to next option/answer "..
				"(according to o_sort).]"
		end
		anz_options = anz_options + 1
	end

	-- less than yl_speak_up.max_number_of_options_per_dialog options?
	local button_add = ""..
		"button[2.4,18.7;2.0,0.9;add_option;Add]"..
		"tooltip[add_option;Add a new option/answer to this dialog.]"
	if(anz_options >= yl_speak_up.max_number_of_options_per_dialog) then
		button_add = ""
	end

	-- build up the formspec
	local formspec = ""..
		"formspec_version[3]"..
		"size[21,20]"..
		"bgcolor[#00000000;false]"..
		-- button back to the current dialog (of which this is an option)
		"button[15.8,0.2;5.0,0.9;show_current_dialog;Back to dialog "..
			minetest.formspec_escape(d_id).."]"..
		"tooltip[show_current_dialog;Go back to dialog "..
			minetest.formspec_escape(d_id).." and continue editing that dialog.]"..
		-- the text the NPC says
		"label[0.2,0.6;NPC says:]"..
		"hypertext[1.2,1.2;19.6,2.5;d_text;<normal>"..
			minetest.formspec_escape(n_dialog.d_text) .. "\n</normal>".."]"..
		"tooltip[1.2,1.2;19.6,3.0;This is what the NPC says to the player.]"..
		-- list the preconditions
		"label[0.2,4.2;If all of the following pre(C)onditions are fulfilled:]"..
		-- TODO: perhaps add tooltip for the type of the conditions
		"tablecolumns[text;color,span=1;text;text]"..
		"table[1.2,4.5;19.6,2.0;table_of_preconditions;"..
			list_of_preconditions..";0]"..
		-- answer of the player (the actual option)
		"label[0.2,6.8;..the player may answer with this text:]"..
		"label[1.2,7.6;A:]"..
		"field[1.7,7.1;19.1,0.9;text_option_"..minetest.formspec_escape(o_id)..";;"..
			minetest.formspec_escape(d_option.o_text_when_prerequisites_met).."]"..
		"tooltip[option_text_met;This is the answer the player may choose if the "..
			"preconditions are all fulfilled.]"..
		-- dropdown for selecting weather to show the alternate answer or not
		"label[0.2,8.6;..but if at least one pre(C)ondition is not fulfilled, then...]"..
		"dropdown[12.0,8.2;8.6,0.9;hide_or_grey_or_alternate_answer;"..
			"..hide this answer.,"..
			"..grey out this answer.,"..
			"..display the following alternate answer:;"..
			alternate_answer_option..";]"..
		-- alternate answer
		"label[1.2,9.6;A:]"..
		"field[1.7,9.1;19.1,0.9;option_text_not_met;;"..
			minetest.formspec_escape(d_option.o_text_when_prerequisites_not_met).."]"..
		"tooltip[option_text_not_met;This is the answer the player may choose if the "..
			"preconditions are NOT all fulfilled.]"..
		-- list of (A)ctions (there can only be one per option; i.e. a trade)
		"label[0.2,10.6;When this answer has been selected, start the following (A)ction:]"..
		"tablecolumns[text;color,span=1;text;text]"..
		"table[1.2,10.9;19.6,0.7;table_of_actions;"..
			list_of_actions..";0]"..
		-- list of effects
		"label[0.2,12.0;If the player completed the above action successfully, "..
			"apply the following (Ef)fects:]"..
		-- TODO: perhaps add tooltip for the type of the conditions
		"tablecolumns[text;color,span=1;text;text]"..
		"table[1.2,12.3;21.0,2.0;table_of_effects;"..
			list_of_effects..";0]"..
		-- ..and what the NPC will reply to that answer
		"label[0.2,15.1;The NPC will react to this answer with the following dialog:]"..
		"hypertext[1.2,15.7;19.6,2.5;d_text_next;<normal>"..
			minetest.formspec_escape(next_text) .. "\n</normal>".."]"..
		"tooltip[1.2,16.8;21.0,2.5;This is what the NPC will say next when the player has "..
			"selected this answer here.]"..
		-- allow to change the target dialog via a dropdown menu
		"dropdown[14.8,14.7;5,0.9;d_id_"..minetest.formspec_escape(o_id)..";"..
			dialog_list..";"..dialog_selected..",]"..
		"tooltip[14.8,14.7;5,0.9;Select the target dialog with which the NPC shall react "..
			"to this answer. Currently, dialog "..minetest.formspec_escape(target_dialog)..
			" is beeing displayed.;#FFFFFF;#000000]"..
		-- button: delete
		"button[0.2,18.7;2.0,0.9;del_option;Delete]"..
		"tooltip[del_option;Delete this option/answer.]"..
		-- button: add new
		button_add..
		-- button: prev/next
		button_prev..
		button_next..
		-- button: go back to dialog (repeated from top of the page)
		"button[15.8,18.7;5.0,0.9;show_current_dialog;Back to dialog "..
			minetest.formspec_escape(d_id).."]"..
		"tooltip[show_current_dialog;Go back to dialog "..
			minetest.formspec_escape(d_id).." and continue editing that dialog.]"..
		-- allow to enter o_sort
		"label[9.6,19.2;Sort:]"..
		"field[10.6,18.7;1.0,0.9;edit_option_o_sort;;"..
			minetest.formspec_escape(d_option.o_sort).."]"..
		"tooltip[edit_option_o_sort;o_sort: The lower the number, the higher up in the "..
			"list this option goes\nNegative values are ignored;#FFFFFF;#000000]"..
		-- hidden field containing the value of o_id
		"field[40,40;0.1,0.1;o_id;;"..minetest.formspec_escape(o_id).."]"
	return formspec
end