-- 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");

local token_protocol = module:get_option_string(module.name .. "_protocol", "v1");

-- depends

module:depends("disco");

-- namespace

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

local namespace = "urn:xmpp:http:upload:0";

-- identity and feature advertising

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

module:add_feature(namespace);

module:add_feature(legacy_namespace);

module:add_extension(dataform {

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

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

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

module:add_extension(dataform {

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

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

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

local function magic_crypto_dust(random, filename, filesize, filetype)

	local param, message;

	if token_protocol == "v1" then

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

	else

		param, message = "v2", string.format("%s/%s\0%d\0%s", random, filename, filesize, filetype);

	end

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

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

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

end

local function handle_request(origin, stanza, xmlns, filename, filesize, filetype)

	-- 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 nil, nil;

	end

	-- validate

	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 nil, nil;

	end

	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 nil, nil;

	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})

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

		return nil, nil;

	end

	local random = uuid();

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

	local put_url = get_url .. verify;

	return get_url, put_url;

end

-- hooks

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

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

	local request = stanza.tags[1];

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

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

	local filetype = request.attr["content-type"] or "application/octet-stream";

	local get_url, put_url = handle_request(

		origin, stanza, legacy_namespace, filename, filesize, filetype);

	if not get_url then

		-- error was already sent

		return true;

	end

	local reply = st.reply(stanza)

		:tag("slot", { xmlns = legacy_namespace })

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

			:tag("put"):text(put_url):up()

		:up();

	origin.send(reply);

	return true;

end);

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

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

	local request = stanza.tags[1];

	local filename = request.attr.filename;

	local filesize = tonumber(request.attr.size);

	local filetype = request.attr["content-type"] or "application/octet-stream";

	local get_url, put_url = handle_request(

		origin, stanza, namespace, filename, filesize, filetype);

	if not get_url then

		-- error was already sent

		return true;

	end

	local reply = st.reply(stanza)

		:tag("slot", { xmlns = namespace})

			:tag("get", { url = get_url }):up()

			:tag("put", { url = put_url }):up()

		:up();

	origin.send(reply);

	return true;

end);