Diff

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_muc_media_metadata/mod_muc_media_metadata.lua	Sun Sep 29 16:47:57 2019 +0100
@@ -0,0 +1,61 @@
+local async = require "util.async";
+local promise = require "util.promise";
+local http = require "net.http";
+local st = require "util.stanza";
+
+local xmlns_metadata = "https://prosody.im/protocol/media-metadata#0"
+
+local fetch_headers = {
+	bytes = "content-length";
+	type = "content-type";
+	etag = "etag";
+	blurhash = "blurhash";
+};
+
+local function fetch_media_metadata(url)
+	return promise.new(function (resolve)
+		http.request(url, { method = "HEAD" }, function (body, code, response) --luacheck: ignore 212/body
+			if code == 200 then
+				local metadata = {};
+				for metadata_name, header_name in pairs(fetch_headers) do
+					metadata[metadata_name] = response.headers[header_name];
+				end
+				resolve(metadata);
+			else
+				resolve(nil);
+			end
+		end);
+	end);
+end
+
+local function metadata_to_tag(metadata)
+	if not metadata then return; end
+
+	local metadata_tag = st.stanza("metadata", { xmlns = xmlns_metadata });
+	for k, v in pairs(metadata) do
+		metadata_tag:text_tag(k, v)
+	end
+
+	return metadata_tag;
+end
+
+module:hook("muc-occupant-groupchat", function (event)
+	local stanza = event.stanza;
+
+	local promises;
+
+	for oob in stanza:childtags("x", "jabber:x:oob") do
+		if not promises then promises = {}; end
+		local url = oob:get_child_text("url");
+		local p = fetch_media_metadata(url)
+			:next(metadata_to_tag)
+			:next(function (metadata_tag)
+				oob:add_child(metadata_tag);
+			end);
+		table.insert(promises, p);
+	end
+
+	if not promises then return; end
+
+	async.wait(promise.all(promises));
+end);