-- mod_http_upload_external

--

-- Copyright (C) 2015-2016 Kim Alvefur

--

-- This file is MIT/X11 licensed.

--

-- imports

local st = require"util.stanza";

local uuid = require"util.uuid".generate;

local http = require "util.http";

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

local HMAC = require "util.hashes".hmac_sha256;

-- config

local file_size_limit = module:get_option_number(module.name .. "_file_size_limit", 100 * 1024 * 1024); -- 100 MB

local base_url = assert(module:get_option_string(module.name .. "_base_url"), module.name .. "_base_url is a required option");

local secret = assert(module:get_option_string(module.name .. "_secret"), module.name .. "_secret is a required option");

-- depends

module:depends("disco");

-- namespace

local xmlns_http_upload = "urn:xmpp:http:upload";

-- identity and feature advertising

module:add_identity("store", "file", module:get_option_string("name", "HTTP File Upload"))

module:add_feature(xmlns_http_upload);

module:add_extension(dataform {

	{ name = "FORM_TYPE", type = "hidden", value = xmlns_http_upload },

	{ name = "max-file-size", type = "text-single" },

}:form({ ["max-file-size"] = tostring(file_size_limit) }, "result"));

local function magic_crypto_dust(random, filename, filesize)

	local message = string.format("%s/%s %d", random, filename, filesize);

	local digest = HMAC(secret, message, true);

	random, filename = http.urlencode(random), http.urlencode(filename);

	return base_url .. random .. "/" .. filename, "?v=" .. digest;

end

-- hooks

module:hook("iq/host/"..xmlns_http_upload..":request", function (event)

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

	local request = stanza.tags[1];

	-- local clients only

	if origin.type ~= "c2s" then

		module:log("debug", "Request for upload slot from a %s", origin.type);

		origin.send(st.error_reply(stanza, "cancel", "not-authorized"));

		return true;

	end

	-- validate

	local filename = request:get_child_text("filename");

	if not filename or filename:find("/") then

		module:log("debug", "Filename %q not allowed", filename or "");

		origin.send(st.error_reply(stanza, "modify", "bad-request", "Invalid filename"));

		return true;

	end

	local filesize = tonumber(request:get_child_text("size"));

	if not filesize then

		module:log("debug", "Missing file size");

		origin.send(st.error_reply(stanza, "modify", "bad-request", "Missing or invalid file size"));

		return true;

	elseif filesize > file_size_limit then

		module:log("debug", "File too large (%d > %d)", filesize, file_size_limit);

		origin.send(st.error_reply(stanza, "modify", "not-acceptable", "File too large",

			st.stanza("file-too-large", {xmlns=xmlns_http_upload})

				:tag("max-size"):text(tostring(file_size_limit))));

		return true;

	end

	local reply = st.reply(stanza);

	reply:tag("slot", { xmlns = xmlns_http_upload });

	local random = uuid();

	local get_url, verify = magic_crypto_dust(random, filename, filesize);

	reply:tag("get"):text(get_url):up();

	reply:tag("put"):text(get_url .. verify):up();

	module:log("info", "Handed out upload slot %s to %s@%s", get_url, origin.username, origin.host);

	origin.send(reply);

	return true;

end);