-- allow show_fs to be extended more easily;
--   key: formname without yl_speak_up: prefix
yl_speak_up.registered_forms_get_fs = {}
yl_speak_up.registered_forms_input_handler = {}
-- force_fs_ver can be nil if no special formspec version is required
yl_speak_up.registered_forms_force_fs_ver = {}

yl_speak_up.register_fs = function(formname, fun_input_handler, fun_get_fs, force_fs_ver)
	yl_speak_up.registered_forms_input_handler[formname] = fun_input_handler
	yl_speak_up.registered_forms_get_fs[formname] = fun_get_fs
	yl_speak_up.registered_forms_force_fs_ver[formname] = force_fs_ver
end


-- route player input to the right functions;
-- return true when the right function has been found
-- called in minetest.register_on_player_receive_fields
yl_speak_up.input_handler = function(player, formname, fields)
	if(not(formname)) then
		return false
	end
	-- cut off the leading "yl_speak_up:" prefix
	local fs_name = string.sub(formname, 13)
	if(fs_name and fs_name ~= "") then
		local fun = yl_speak_up.registered_forms_input_handler[fs_name]
		if(fun) then
			fun(player, formname, fields)
			return true
		end
	end


	-- handled in fs_initial_config.lua
	if formname == "yl_speak_up:initial_config" then
		yl_speak_up.input_fs_initial_config(player, formname, fields)
		return true
	end
end


-- show formspec with highest possible version information for the player
-- force_version: optional parameter
yl_speak_up.show_fs_ver = function(pname, formname, formspec, force_version)
	-- if the formspec already calls for a specific formspec version: use that one
	if(string.sub(formspec, 1, 17) == "formspec_version[") then
		minetest.show_formspec(pname, formname, formspec)
		return
	end
	local fs_ver = (yl_speak_up.fs_version[pname] or "2")
	if(force_version) then
		fs_ver = force_version
	end
	minetest.show_formspec(pname, formname,
		"formspec_version["..tostring(fs_ver).."]"..
		formspec)
end


-- call show_formspec with the right input_* function for the right formspec
-- (handles all show_formspec-calls)
yl_speak_up.show_fs = function(player, fs_name, param)
	if(not(player)) then
		return
	end
	local pname = player:get_player_name()
	if(not(yl_speak_up.speak_to[pname])) then
		return
	end

	local last_fs = yl_speak_up.speak_to[pname].last_fs

	if(false) then
	-- the player either saved or discarded; we may proceed now
	elseif(fs_name and fs_name == "proceed_after_save") then
		fs_name = yl_speak_up.speak_to[pname].next_fs
		param = yl_speak_up.speak_to[pname].next_fs_param
		yl_speak_up.speak_to[pname].next_fs = nil
		yl_speak_up.speak_to[pname].next_fs_param = nil
		yl_speak_up.speak_to[pname].last_fs = fs_name
		yl_speak_up.speak_to[pname].last_fs_param = param
		if(not(fs_name) or fs_name == "quit") then
			yl_speak_up.reset_vars_for_player(pname, false)
			return
		end

	-- the player clicked on "back" in the above dialog
	elseif(fs_name and fs_name == "show_last_fs") then
		-- call the last formspec again - and with the same parameters
		fs_name = yl_speak_up.speak_to[pname].last_fs
		param = yl_speak_up.speak_to[pname].last_fs_param

	-- do we need to check if there is something that needs saving?
	elseif(fs_name
	  -- msg is just a loop for displaying (mostly error) messages
	  and fs_name ~= "msg"
	  and fs_name ~= "player_offers_item"
	  -- is the player editing the NPC? that is: might there be any changes?
	  and yl_speak_up.edit_mode
	  and (yl_speak_up.edit_mode[pname] == yl_speak_up.speak_to[pname].n_id)) then
		local last_fs = yl_speak_up.speak_to[pname].last_fs
		local d_id = yl_speak_up.speak_to[pname].d_id
		local o_id = yl_speak_up.speak_to[pname].o_id
		-- only these two formspecs need to ask specificly if the data ought to be saved
		if(last_fs == "talk" or last_fs == "edit_option_dialog" or fs_name == "quit") then
			local last_param = yl_speak_up.speak_to[pname].last_fs_param
			local show_save_fs = false
			if(not(param)) then
				param = {}
			end
			-- set the target dialog
			yl_speak_up.speak_to[pname].target_dialog = param.d_id
			-- if we are switching from one dialog to another: is it the same?
			if(last_fs == "talk" and fs_name == last_fs
			  and param and param.d_id and param.d_id ~= d_id) then
				-- diffrent parameters: save (if needed)
				show_save_fs = true
			elseif(fs_name == "talk" and param and param.do_save) then
				-- player clicked on save button
				show_save_fs = true
			-- leaving a dialog: save!
			elseif(last_fs == "talk" and fs_name ~= last_fs) then
				show_save_fs = true
			-- clicking on "save" in an edit option dialog: save!
			elseif(last_fs == "edit_option_dialog" and fs_name == last_fs
			  and param and param.caller and param.caller == "save_option") then
				show_save_fs = true
			-- leaving editing an option: save!
			elseif(last_fs == "edit_option_dialog" and fs_name ~= last_fs) then
				show_save_fs = true
			-- quitting: save!
			elseif(fs_name == "quit") then
				yl_speak_up.speak_to[pname].target_dialog = nil
				show_save_fs = true
			end
			-- show the save or discard dialog
			if(show_save_fs) then
				yl_speak_up.speak_to[pname].next_fs = fs_name
				yl_speak_up.speak_to[pname].next_fs_param = param
				-- check first if it's necessary to ask for save or discard
				yl_speak_up.input_save_or_discard_changes(player, "", {})
				return
			end
		end
		-- store the new formspec
		yl_speak_up.speak_to[pname].last_fs = fs_name
		-- and its parameter
		yl_speak_up.speak_to[pname].last_fs_param = param
	end

	-- abort talk if we hit d_end
	if(fs_name == "talk" and param and param.d_id and param.d_id == "d_end") then
		yl_speak_up.stop_talking(pname)
		return
	end

	local fun = yl_speak_up.registered_forms_get_fs[fs_name]
	if(fun) then
		yl_speak_up.show_fs_ver(pname, "yl_speak_up:"..fs_name,
			fun(player, param),
			yl_speak_up.registered_forms_force_fs_ver[fs_name])
		return true
	end

	-- this is here mostly to fascilitate debugging - so that really all calls to
	-- minetest.show_formspec are routed through here
	if(fs_name == "msg") then
		if(not(param)) then
			param = {}
		end
		yl_speak_up.show_fs_ver(pname, param.input_to, param.formspec, 1)


	elseif(fs_name == "quit") then
		return

	elseif(fs_name == "initial_config") then
		if(not(param)) then
			param = {}
		end
		yl_speak_up.show_fs_ver(pname, "yl_speak_up:initial_config",
			yl_speak_up.get_fs_initial_config(player, param.n_id, param.d_id,
				param.is_initial_config))

	-- fallback in case of wrong call
	else
		minetest.chat_send_player(pname, "Error: Trying to show wrong "..
			"formspec: \""..tostring(fs_name).."\". Please notify "..
			"an admin.")
	end
end