local config = require "core.configmanager";

local log = require "util.logger".init("stats");

local timer = require "util.timer";

local fire_event = prosody.events.fire_event;

local stats_config = config.get("*", "statistics_interval");

local stats_interval = tonumber(stats_config);

if stats_config and not stats_interval then

	log("error", "Invalid 'statistics_interval' setting, statistics will be disabled");

end

local stats_provider_config = config.get("*", "statistics_provider");

local stats_provider = stats_provider_config or "internal";

local builtin_providers = {

	internal = "util.statistics";

};

if stats_provider:match("^library:") then

	stats_provider = stats_provider:match(":(.+)$");

else

	stats_provider = builtin_providers[stats_provider];

	if not stats_provider then

		log("error", "Unrecognized built-in statistics provider '%s', using internal instead", stats_provider_config);

		stats_provider = builtin_providers["internal"];

	end

end

local have_stats_provider, stats_lib = pcall(require, stats_provider);

local stats, stats_err;

if not have_stats_provider then

	stats, stats_err = nil, stats_lib;

else

	local stats_config = config.get("*", "statistics_config");

	stats, stats_err = stats_lib.new(stats_config);

end

if not stats then

	log("error", "Error loading statistics provider '%s': %s", stats_provider, stats_err);

end

local measure, collect;

local latest_stats = {};

local changed_stats = {};

local stats_extra = {};

if stats then

	function measure(type, name)

		local f = assert(stats[type], "unknown stat type: "..type);

		return f(name);

	end

end

if stats_interval then

	if stats.get_stats then

		log("debug", "Statistics collection is enabled every %d seconds", stats_interval);

		local mark_collection_start = measure("times", "stats.collection");

		local mark_processing_start = measure("times", "stats.processing");

		function collect()

			local mark_collection_done = mark_collection_start();

			fire_event("stats-update");

			changed_stats, stats_extra = {}, {};

			for stat_name, getter in pairs(stats.get_stats()) do

				local type, value, extra = getter();

				local old_value = latest_stats[stat_name];

				latest_stats[stat_name] = value;

				if value ~= old_value then

					changed_stats[stat_name] = value;

				end

				if extra then

					stats_extra[stat_name] = extra;

				end

			end

			mark_collection_done();

			local mark_processing_done = mark_processing_start();

			fire_event("stats-updated", { stats = latest_stats, changed_stats = changed_stats, stats_extra = stats_extra });

			mark_processing_done();

			return stats_interval;

		end

		timer.add_task(stats_interval, collect);

		prosody.events.add_handler("server-started", function () collect() end, -1);

	else

		log("error", "statistics_interval specified, but the selected statistics_provider (%s) does not support statistics collection", stats_provider_config or "internal");

	end

end

if not stats_interval and stats_provider == "util.statistics" then

	log("debug", "Statistics collection is disabled");

	-- nop

	function measure()

		return measure;

	end

	function collect()

	end

end

return {

	measure = measure;

	get_stats = function ()

		return latest_stats, changed_stats, stats_extra;

	end;

	get = function (name)

		return latest_stats[name], stats_extra[name];

	end;

};