-- Log common stats to statsd

--

-- Copyright (C) 2014 Daurnimator

--

-- This module is MIT/X11 licensed.

module:set_global();

module:depends "http";

local s_format = string.format;

local t_insert = table.insert;

local socket = require "socket";

local mt = require "util.multitable";

local meta = mt.new(); meta.data = module:shared"meta";

local data = mt.new(); data.data = module:shared"data";

local function escape(text)

	return text:gsub("\\", "\\\\"):gsub("\"", "\\\""):gsub("\n", "\\n");

end

local function escape_name(name)

	return name:gsub("[^A-Za-z0-9_]", "_"):gsub("^[^A-Za-z_]", "_%1");

end

local function get_timestamp()

	-- Using LuaSocket for that because os.time() only has second precision.

	return math.floor(socket.gettime() * 1000);

end

local function repr_help(metric, docstring)

	docstring = docstring:gsub("\\", "\\\\"):gsub("\n", "\\n");

	return "# HELP "..escape_name(metric).." "..docstring.."\n";

end

-- local allowed_types = { counter = true, gauge = true, histogram = true, summary = true, untyped = true };

-- local allowed_types = { "counter", "gauge", "histogram", "summary", "untyped" };

local function repr_type(metric, type_)

	-- if not allowed_types:contains(type_) then

	-- 	return;

	-- end

	return "# TYPE "..escape_name(metric).." "..type_.."\n";

end

local function repr_label(key, value)

	return key.."=\""..escape(value).."\"";

end

local function repr_labels(labels)

	local values = {}

	for key, value in pairs(labels) do

		t_insert(values, repr_label(escape_name(key), escape(value)));

	end

	if #values == 0 then

		return "";

	end

	return "{"..table.concat(values, ", ").."}";

end

local function repr_sample(metric, labels, value, timestamp)

	return escape_name(metric)..repr_labels(labels).." "..value.." "..timestamp.."\n";

end

module:hook("stats-updated", function (event)

	local all_stats, this = event.stats_extra;

	local host, sect, name, typ, key;

	for stat, value in pairs(event.changed_stats) do

		this = all_stats[stat];

		-- module:log("debug", "changed_stats[%q] = %s", stat, tostring(value));

		host, sect, name, typ = stat:match("^/([^/]+)/([^/]+)/(.+):(%a+)$");

		if host == nil then

			sect, name, typ, host = stat:match("^([^.]+)%.([^:]+):(%a+)$");

		elseif host == "*" then

			host = nil;

		end

		if sect:find("^mod_measure_.") then

			sect = sect:sub(13);

		elseif sect:find("^mod_statistics_.") then

			sect = sect:sub(16);

		end

		key = escape_name(s_format("%s_%s_%s", host or "global", sect, typ));

		if not meta:get(key) then

			if host then

				meta:set(key, "", "graph_title", s_format("%s %s on %s", sect, typ, host));

			else

				meta:set(key, "", "graph_title", s_format("Global %s %s", sect, typ, host));

			end

			meta:set(key, "", "graph_vlabel", this and this.units or typ);

			meta:set(key, "", "graph_category", sect);

			meta:set(key, name, "label", name);

		elseif not meta:get(key, name, "label") then

			meta:set(key, name, "label", name);

		end

		data:set(key, name, value);

	end

end);

local function get_metrics(event)

	local response = event.response;

	response.headers.content_type = "text/plain; version=0.4.4";

	local response = {};

	local timestamp = tostring(get_timestamp());

	for section, data in pairs(data.data) do

		for key, value in pairs(data) do

			t_insert(response, repr_help(name, "TODO: add a description here."));

			t_insert(response, repr_type(name, "gauge"));

			t_insert(response, repr_sample(name, {}, value, timestamp));

		end

	end

	return table.concat(response, "");

end

function module.add_host(module)

	module:provides("http", {

		default_path = "metrics";

		route = {

			GET = get_metrics;

		};

	});

end