module:depends("cache_c2s_caps");

local st = require "util.stanza";

local encodings = require "util.encodings";

local b64_encode = encodings.base64.encode;

local b64_decode = encodings.base64.decode;

local sha1 = require"util.hashes".sha1;

-- TODO: Move that to storage.

local cache = {};

-- TODO: use util.cache for this.

local in_flight = {};

local function check_cid(src)

	return src:match("^cid:(%w+%+%w+@bob%.xmpp%.org)$");

end

local function handle_data_carrier(tag)

	if tag.name ~= "data" or tag.attr.xmlns ~= "urn:xmpp:bob" then

		return tag;

	end

	local cid = tag.attr.cid;

	local media_type = tag.attr.type;

	local max_age = tag.attr['max-age'];

	local b64_content = tag:get_text();

	local content = b64_decode(b64_content);

	local hash = sha1(content, true);

	if cid ~= "sha1+"..hash.."@bob.xmpp.org" then

		module:log("debug", "Invalid BoB cid, %s ~= %s", cid, "sha1+"..hash.."@bob.xmpp.org");

		return nil;

	end

	cache[cid] = { media_type = media_type, max_age = max_age, content = content };

	if in_flight[cid] then

		local iq = st.iq({ type = "result", id = "fixme" });

		iq:add_direct_child(tag);

		for jid, data in pairs(in_flight[cid]) do

			iq.attr.from = data.from;

			iq.attr.to = jid;

			iq.attr.id = data.id;

			module:send(iq);

		end

		in_flight[cid] = nil;

	end

	return nil;

end

local current_id = 0;

local function send_iq(room_jid, jid, cid, log)

	local iq = st.iq({ type = "get", from = room_jid, to = jid, id = "bob-"..current_id })

		:tag("data", { xmlns = "urn:xmpp:bob", cid = cid });

	log("debug", "found BoB image in XHTML-IM, asking %s for cid %s", jid, cid);

	module:send(iq);

	in_flight[cid] = {};

end

local function find_images(tag, jid, room_jid, log)

	if tag.name == "img" and tag.attr.xmlns == "http://www.w3.org/1999/xhtml" then

		local src = tag.attr.src;

		local cid = check_cid(src);

		if not cid then

			return;

		end

		if cache[cid] then

			log("debug", "cid %s already found in cache", cid);

			return;

		end

		if in_flight[cid] then

			log("debug", "cid %s already queried", cid);

			return;

		end

		send_iq(room_jid, jid, cid, log);

		return;

	end

	for child in tag:childtags(nil, "http://www.w3.org/1999/xhtml") do

		find_images(child, jid, room_jid, log);

	end

end

local function message_handler(event)

	local stanza, origin = event.stanza, event.origin;

	local jid = stanza.attr.from;

	local room_jid = stanza.attr.to;

	local log = origin.log or module._log;

	-- Remove and cache all <data/> elements embedded here.

	stanza:maptags(handle_data_carrier);

	-- Find and query all of the cids not already cached.

	local tag = stanza:get_child("html", "http://jabber.org/protocol/xhtml-im");

	if not tag then

		return;

	end

	for body in tag:childtags("body", "http://www.w3.org/1999/xhtml") do

		find_images(body, jid, room_jid, log);

	end

end

local function handle_data_get(stanza, cid, log)

	local data = cache[cid];

	if not data then

		log("debug", "BoB requested for data not in cache (cid %s), falling through.", cid);

		if in_flight[cid] then

			log("debug", "But an iq has already been sent, let’s wait…");

			in_flight[cid][stanza.attr.from] = { id = stanza.attr.id, from = stanza.attr.to };

			return true;

		end

		return nil;

	end

	local iq = st.reply(stanza);

	iq:text_tag("data", b64_encode(data.content), {

		xmlns = "urn:xmpp:bob",

		cid = cid,

		type = data.media_type,

		['max-age'] = data.max_age,

	});

	log("debug", "Answering BoB request for cid %s on the behalf of %s", cid, stanza.attr.to);

	module:send(iq);

	return true;

end

local function iq_handler(event)

	local stanza, origin = event.stanza, event.origin;

	local tag = stanza.tags[1];

	if tag.name ~= "data" or tag.attr.xmlns ~= "urn:xmpp:bob" then

		return nil;

	end

	local log = origin.log or module._log;

	local cid = tag.attr.cid;

	if not cid then

		log("debug", "BoB iq doesn’t contain a cid attribute.");

		return;

	end

	if stanza.attr.type == "get" then

		return handle_data_get(stanza, cid, log);

	elseif stanza.attr.type == "result" then

		handle_data_carrier(tag);

		return true;

	end

	-- TODO: also handle error iqs.

end

module:hook("message/bare", message_handler, 1);

module:hook("iq/full", iq_handler, 1);

module:hook("iq/bare", iq_handler, 1);