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_interval_config = config.get("*", "statistics_interval");

local stats_interval = tonumber(stats_interval_config);

if stats_interval_config and not stats_interval then

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

end

local stats_provider_name;

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

local stats_provider = stats_provider_config;

if not stats_provider and stats_interval then

	stats_provider = "internal";

elseif stats_provider and not stats_interval then

	stats_interval = 60;

end

local builtin_providers = {

	internal = "util.statistics";

	statsd = "util.statsd";

};

local stats, stats_err = false, nil;

if stats_provider then

	if stats_provider:sub(1,1) == ":" then

		stats_provider = stats_provider:sub(2);

		stats_provider_name = "external "..stats_provider;

	elseif stats_provider then

		stats_provider_name = "built-in "..stats_provider;

		stats_provider = builtin_providers[stats_provider];

		if not stats_provider then

			log("error", "Unrecognized statistics provider '%s', statistics will be disabled", stats_provider_config);

		end

	end

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

	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);

		stats_provider_name = stats_lib._NAME or stats_provider_name;

	end

end

if stats == nil 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

	if stats_interval then

		log("debug", "Statistics enabled using %s provider, collecting every %d seconds", stats_provider_name, 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");

			mark_collection_done();

			if stats.get_stats then

				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

				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();

			end

			return stats_interval;

		end

		timer.add_task(stats_interval, collect);

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

	else

		log("debug", "Statistics enabled using %s provider, collection is disabled", stats_provider_name);

	end

else

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

	function measure() return measure; 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;

};