local st = require "util.stanza";

local new_id = require"util.id".medium;

local dataform = require "util.dataforms".new;

local local_domain = module:get_host();

local service = module:get_option(module.name .. "_service") or "pubsub." .. local_domain;

local node = module:get_option(module.name .. "_node") or "serverinfo";

local actor = module.host .. "/modules/" .. module.name;

local publication_interval = module:get_option(module.name .. "_publication_interval") or 300;

local cache_ttl = module:get_option(module.name .. "_cache_ttl") or 3600;

function module.load()

	discover_node():next(

		function(exists)

			if not exists then create_node() end

		end

	):catch(

		function(error)

			module:log("warn", "Error prevented discovery or creation of pub/sub node at %s: %s", service, error)

		end

	)

	module:add_feature("urn:xmpp:serverinfo:0");

	module:add_extension(dataform {

		{ name = "FORM_TYPE", type = "hidden", value = "http://jabber.org/network/serverinfo" },

		{ name = "serverinfo-pubsub-node", type = "text-single" },

	}:form({ ["serverinfo-pubsub-node"] = ("xmpp:%s?;node=%s"):format(service, node) }, "result"));

	if cache_ttl < publication_interval then

		module:log("warn", "It is recommended to have a cache interval higher than the publication interval");

	end

	cache_warm_up()

	module:add_timer(10, publish_serverinfo);

end

function module.unload()

	-- This removes all subscribers, which may or may not be desirable, depending on the reason for the unload.

	delete_node(); -- Should this block, to delay unload() until the node is deleted?

end

-- Returns a promise of a boolean

function discover_node()

	local request = st.iq({ type = "get", to = service, from = actor, id = new_id() })

		:tag("query", { xmlns = "http://jabber.org/protocol/disco#items" })

	module:log("debug", "Sending request to discover existence of pub/sub node '%s' at %s", node, service)

	return module:send_iq(request):next(

		function(response)

			if response.stanza == nil or response.stanza.attr.type ~= "result" then

				module:log("warn", "Unexpected response to service discovery items request at %s: %s", service, response.stanza)

				return false

			end

			local query = response.stanza:get_child("query", "http://jabber.org/protocol/disco#items")

			if query ~= nil then

				for item in query:childtags("item") do

					if item.attr.jid == service and item.attr.node == node then

						module:log("debug", "pub/sub node '%s' at %s does exist.", node, service)

						return true

					end

				end

			end

			module:log("debug", "pub/sub node '%s' at %s does not exist.", node, service)

			return false;

		end

	);

end

-- Returns a promise of a boolean

function create_node()

	local request = st.iq({ type = "set", to = service, from = actor, id = new_id() })

		:tag("pubsub", { xmlns = "http://jabber.org/protocol/pubsub" })

			:tag("create", { node = node }):up()

			:tag("configure")

				:tag("x", { xmlns = "jabber:x:data", type = "submit" })

					:tag("field", { var = "FORM_TYPE", type = "hidden"})

						:text_tag("value", "http://jabber.org/protocol/pubsub#node_config")

						:up()

					:tag("field", { var = "pubsub#max_items" })

						:text_tag("value", "1")

						:up()

					:tag("field", { var = "pubsub#persist_items" })

						:text_tag("value", "0")

	module:log("debug", "Sending request to create pub/sub node '%s' at %s", node, service)

	return module:send_iq(request):next(

		function(response)

			if response.stanza == nil or response.stanza.attr.type ~= "result" then

				module:log("warn", "Unexpected response to pub/sub node '%s' creation request at %s: %s", node, service, response.stanza)

				return false

			else

				module:log("debug", "Successfully created pub/sub node '%s' at %s", node, service)

				return true

			end

		end

	)

end

-- Returns a promise of a boolean

function delete_node()

	local request = st.iq({ type = "set", to = service, from = actor, id = new_id() })

		:tag("pubsub", { xmlns = "http://jabber.org/protocol/pubsub" })

			:tag("delete", { node = node });

	module:log("debug", "Sending request to delete pub/sub node '%s' at %s", node, service)

	return module:send_iq(request):next(

		function(response)

			if response.stanza == nil or response.stanza.attr.type ~= "result" then

				module:log("warn", "Unexpected response to pub/sub node '%s' deletion request at %s: %s", node, service, response.stanza)

				return false

			else

				module:log("debug", "Successfully deleted pub/sub node '%s' at %s", node, service)

				return true

			end

		end

	)

end

function get_remote_domain_names()

	-- Iterate over s2s sessions, adding them to a multimap, where the key is the local domain name,

	-- mapped to a collection of remote domain names. De-duplicate all remote domain names by using

	-- them as an index in a table.

	local domains_by_host = {}

	for session, _ in pairs(prosody.incoming_s2s) do

		if session ~= nil and session.from_host ~= nil and local_domain == session.to_host then

			module:log("debug", "Local host '%s' has remote '%s' (inbound)", session.to_host, session.from_host);

			local sessions = domains_by_host[session.to_host]

			if sessions == nil then sessions = {} end; -- instantiate a new entry if none existed

			sessions[session.from_host] = true

			domains_by_host[session.to_host] = sessions

		end

	end

	-- At an earlier stage, the code iterated over all prosody.hosts, trying to generate one pubsub item for all local hosts. That turned out to be

	-- to noisy. Instead, this code now creates an item that includes the local vhost only. It is assumed that this module will also be loaded for

	-- other vhosts. Their data should then be published to distinct pub/sub services and nodes.

	-- for host, data in pairs(prosody.hosts) do

	local host = local_domain

	local data = prosody.hosts[host]

	if data ~= nil then

		local sessions = domains_by_host[host]

		if sessions == nil then sessions = {} end; -- instantiate a new entry if none existed

		if data.s2sout ~= nil then

			for _, session in pairs(data.s2sout) do

				if session.to_host ~= nil then

					module:log("debug", "Local host '%s' has remote '%s' (outbound)", host, session.to_host);

					sessions[session.to_host] = true

					domains_by_host[host] = sessions

				end

			end

		end

		-- When the instance of Prosody hosts more than one host, the other hosts can be thought of as having a 'permanent' s2s connection.

		for host_name, host_info in pairs(prosody.hosts) do

			if host ~= host_name and host_info.type ~= "component" then

				module:log("debug", "Local host '%s' has remote '%s' (vhost)", host, host_name);

				sessions[host_name] = true;

				domains_by_host[host] = sessions

			end

		end

	end

	return domains_by_host

end

function publish_serverinfo()

	module:log("debug", "Publishing server info...");

	local domains_by_host = get_remote_domain_names()

	-- Build the publication stanza.

	local request = st.iq({ type = "set", to = service, from = actor, id = new_id() })

		:tag("pubsub", { xmlns = "http://jabber.org/protocol/pubsub" })

			:tag("publish", { node = node, xmlns = "http://jabber.org/protocol/pubsub" })

				:tag("item", { id = "current", xmlns = "http://jabber.org/protocol/pubsub" })

					:tag("serverinfo", { xmlns = "urn:xmpp:serverinfo:0" })

	request:tag("domain", { name = local_domain })

		:tag("federation")

	local remotes = domains_by_host[local_domain]

	if remotes ~= nil then

		for remote, _ in pairs(remotes) do

			-- include a domain name for remote domains, but only if they advertise support.

			if does_opt_in(remote) then

				request:tag("remote-domain", { name = remote }):up()

			else

				request:tag("remote-domain"):up()

			end

		end

	end

	request:up():up()

	module:send_iq(request):next(

		function(response)

			if response.stanza == nil or response.stanza.attr.type ~= "result" then

				module:log("warn", "Unexpected response to item publication at pub/sub node '%s' on %s: %s", node, service, response.stanza)

				return false

			else

				module:log("debug", "Successfully published item on pub/sub node '%s' at %s", node, service)

				return true

			end

		end,

		function(error)

			module:log("warn", "Error prevented publication of item on pub/sub node at %s: %s", service, error)

		end

	)

	return publication_interval;

end

local opt_in_cache = {}

function cache_warm_up()

	module:log("debug", "Warming up opt-in cache")

	local domains_by_host = get_remote_domain_names()

	local remotes = domains_by_host[local_domain]

	if remotes ~= nil then

		for remote, _ in pairs(remotes) do

			does_opt_in(remote)

		end

	end

end

function does_opt_in(remoteDomain)

	-- try to read answer from cache.

	local cached_value = opt_in_cache[remoteDomain]

	local ttl = cached_value and os.difftime(cached_value.expires, os.time());

	if cached_value and ttl > (publication_interval + 60) then

		module:log("debug", "Opt-in status (from cache) for '%s': %s", remoteDomain, cached_value.opt_in)

		return cached_value.opt_in;

	end

	-- We don't have a cached value, or it is nearing expiration - refresh it now

	-- TODO worry about not having multiple requests in flight to the same domain.cached_value

	module:log("debug", "%s: performing disco/info to determine opt-in", remoteDomain)

	local discoRequest = st.iq({ type = "get", to = remoteDomain, from = actor, id = new_id() })

		:tag("query", { xmlns = "http://jabber.org/protocol/disco#info" })

	module:send_iq(discoRequest):next(

		function(response)

			if response.stanza ~= nil and response.stanza.attr.type == "result" then

				local query = response.stanza:get_child("query", "http://jabber.org/protocol/disco#info")

				if query ~= nil then

					for feature in query:childtags("feature") do

						--module:log("debug", "Disco/info feature for '%s': %s", remoteDomain, feature)

						if feature.attr.var == 'urn:xmpp:serverinfo:0' then

							module:log("debug", "Disco/info response included opt-in for '%s'", remoteDomain)

							opt_in_cache[remoteDomain] = {

								opt_in = true;

								expires = os.time() + cache_ttl;

							}

							return; -- prevent 'false' to be cached, down below.

						end

					end

				end

			end

			module:log("debug", "Disco/info response did not include opt-in for '%s'", remoteDomain)

			opt_in_cache[remoteDomain] = {

				opt_in = false;

				expires = os.time() + cache_ttl;

			}

		end,

		function(response)

			module:log("debug", "An error occurred while performing a disco/info request to determine opt-in for '%s'", remoteDomain, response)

			opt_in_cache[remoteDomain] = {

				opt_in = false;

				expires = os.time() + cache_ttl;

			}

		end

	);

	if ttl and ttl <= 0 then

		-- Cache entry expired, remove it and assume not opted in

		opt_in_cache[remoteDomain] = nil;

		return false;

	end

	return cached_value and cached_value.opt_in;

end