module:depends("cache_c2s_caps");

local st = require "util.stanza";

local hashes = require "util.hashes";

local base64 = require "util.encodings".base64;

local t_insert, t_sort, t_concat = table.insert, table.sort, table.concat;

local algorithms = module:get_option_set("ecaps2_hashes", { "sha-256", "sha-512" });

-- TODO: Add all of the other hashes supported.

local algorithm_map = {

	["sha-256"] = hashes.sha256;

	["sha-512"] = hashes.sha512;

};

-- TODO: move that to util.caps maybe.

local function calculate_hash(disco_info)

	local identities, features, extensions = {}, {}, {};

	for _, tag in ipairs(disco_info) do

		if tag.name == "identity" then

			t_insert(identities, ((tag.attr.category or "").."\31"..

			                      (tag.attr.type or "").."\31"..

					      (tag.attr["xml:lang"] or "").."\31"..

					      (tag.attr.name or "").."\31\30"));

		elseif tag.name == "feature" then

			t_insert(features, (tag.attr.var or "").."\31");

		elseif tag.name == "x" and tag.attr.xmlns == "jabber:x:data" then

			local form = {};

			for _, field in ipairs(tag.tags) do

				if field.name == "field" and field.attr.xmlns == "jabber:x:data" and field.attr.var then

					local values = {};

					for _, value in ipairs(field.tags) do

						if value.name == "value" and value.attr.xmlns == "jabber:x:data" then

							value = #value.tags == 0 and value:get_text();

							if value then t_insert(values, value.."\31"); end

						end

					end

					t_sort(values);

					if #values > 0 then

						t_insert(form, field.attr.var.."\31"..t_concat(values, "\31").."\31\30");

					else

						t_insert(form, field.attr.var.."\31\30");

					end

				end

			end

			t_sort(form);

			form = t_concat(form, "\29").."\29";

			t_insert(extensions, form);

		else

			return nil, "Unknown element in disco#info";

		end

	end

	t_sort(identities);

	t_sort(features);

	t_sort(extensions);

	if #identities > 0 then identities = t_concat(identities, "\28").."\28"; else identities = "\28"; end

	if #features > 0 then features = t_concat(features).."\28"; else features = "\28"; end

	if #extensions > 0 then extensions = t_concat(extensions, "\28").."\28"; else extensions = "\28"; end

	return features..identities..extensions;

end

local function caps_handler(event)

	local origin = event.origin;

	if origin.presence == nil or origin.presence:get_child("c", "urn:xmpp:caps") then

		return;

	end

	local disco_info = origin.caps_cache;

	if disco_info == nil then

		return;

	end

	local extension_string, err = calculate_hash(disco_info);

	if extension_string == nil then

		module:log("warn", "Failed to calculate ecaps2 hash: %s", err)

		return;

	end

	local ecaps2 = st.stanza("c", { xmlns = "urn:xmpp:caps" });

	for algo in algorithms do

		local func = algorithm_map[algo];

		if func ~= nil then

			local hash = base64.encode(func(extension_string));

			ecaps2:tag("hash", { xmlns = "urn:xmpp:hashes:2"; algo = algo })

			      :text(hash)

			      :up();

		end

	end

	module:log("debug", "Injected ecaps2 element in presence");

	origin.presence:add_child(ecaps2);

end

module:hook("c2s-capabilities-changed", caps_handler);