-- Prosody IM
-- Copyright (C) 2008-2012 Matthew Wild
-- Copyright (C) 2008-2012 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

module:set_global();
pcall(function ()
	module:depends("http_errors");
end);

local portmanager = require "core.portmanager";
local moduleapi = require "core.moduleapi";
local url_parse = require "socket.url".parse;
local url_build = require "socket.url".build;
local normalize_path = require "util.http".normalize_path;
local set = require "util.set";

local ip_util = require "util.ip";
local new_ip = ip_util.new_ip;
local match_ip = ip_util.match;
local parse_cidr = ip_util.parse_cidr;

local server = require "net.http.server";

server.set_default_host(module:get_option_string("http_default_host"));

server.set_option("body_size_limit", module:get_option_number("http_max_content_size"));
server.set_option("buffer_size_limit", module:get_option_number("http_max_buffer_size"));

-- CORS settigs
local opt_methods = module:get_option_set("access_control_allow_methods", { "GET", "OPTIONS" });
local opt_headers = module:get_option_set("access_control_allow_headers", { "Content-Type" });
local opt_credentials = module:get_option_boolean("access_control_allow_credentials", false);
local opt_max_age = module:get_option_number("access_control_max_age", 2 * 60 * 60);

local function get_http_event(host, app_path, key)
	local method, path = key:match("^(%S+)%s+(.+)$");
	if not method then -- No path specified, default to "" (base path)
		method, path = key, "";
	end
	if method:sub(1,1) == "/" then
		return nil;
	end
	if app_path == "/" and path:sub(1,1) == "/" then
		app_path = "";
	end
	if host == "*" then
		return method:upper().." "..app_path..path;
	else
		return method:upper().." "..host..app_path..path;
	end
end

local function get_base_path(host_module, app_name, default_app_path)
	return (normalize_path(host_module:get_option("http_paths", {})[app_name] -- Host
		or module:get_option("http_paths", {})[app_name] -- Global
		or default_app_path)) -- Default
		:gsub("%$(%w+)", { host = host_module.host });
end

local function redir_handler(event)
	event.response.headers.location = event.request.path.."/";
	if event.request.url.query then
		event.response.headers.location = event.response.headers.location .. "?" .. event.request.url.query
	end
	return 301;
end

local ports_by_scheme = { http = 80, https = 443, };

-- Helper to deduce a module's external URL
function moduleapi.http_url(module, app_name, default_path)
	app_name = app_name or (module.name:gsub("^http_", ""));
	local external_url = url_parse(module:get_option_string("http_external_url")) or {};
	if external_url.scheme and external_url.port == nil then
		external_url.port = ports_by_scheme[external_url.scheme];
	end
	local services = portmanager.get_active_services();
	local http_services = services:get("https") or services:get("http") or {};
	for interface, ports in pairs(http_services) do -- luacheck: ignore 213/interface
		for port, service in pairs(ports) do -- luacheck: ignore 512
			local url = {
				scheme = (external_url.scheme or service[1].service.name);
				host = (external_url.host or module:get_option_string("http_host", module.host));
				port = tonumber(external_url.port) or port or 80;
				path = normalize_path(external_url.path or "/", true)..
					(get_base_path(module, app_name, default_path or "/"..app_name):sub(2));
			}
			if ports_by_scheme[url.scheme] == url.port then url.port = nil end
			return url_build(url);
		end
	end
	module:log("warn", "No http ports enabled, can't generate an external URL");
	return "http://disabled.invalid/";
end

local function apply_cors_headers(response, methods, headers, max_age, allow_credentials, origin)
	response.headers.access_control_allow_methods = tostring(methods);
	response.headers.access_control_allow_headers = tostring(headers);
	response.headers.access_control_max_age = tostring(max_age)
	response.headers.access_control_allow_origin = origin or "*";
	if allow_credentials then
		response.headers.access_control_allow_credentials = "true";
	end
end

function module.add_host(module)
	local host = module.host;
	if host ~= "*" then
		host = module:get_option_string("http_host", host);
	end
	local apps = {};
	module.environment.apps = apps;
	local function http_app_added(event)
		local app_name = event.item.name;
		local default_app_path = event.item.default_path or "/"..app_name;
		local app_path = get_base_path(module, app_name, default_app_path);
		if not app_name then
			-- TODO: Link to docs
			module:log("error", "HTTP app has no 'name', add one or use module:provides('http', app)");
			return;
		end
		apps[app_name] = apps[app_name] or {};
		local app_handlers = apps[app_name];

		local app_methods = opt_methods;

		local function cors_handler(event_data)
			local request, response = event_data.request, event_data.response;
			apply_cors_headers(response, app_methods, opt_headers, opt_max_age, opt_credentials, request.headers.origin);
		end

		local function options_handler(event_data)
			cors_handler(event_data);
			return "";
		end

		for key, handler in pairs(event.item.route or {}) do
			local event_name = get_http_event(host, app_path, key);
			if event_name then
				local method = event_name:match("^%S+");
				if not app_methods:contains(method) then
					app_methods = app_methods + set.new{ method };
				end
				local options_event_name = event_name:gsub("^%S+", "OPTIONS");
				if type(handler) ~= "function" then
					local data = handler;
					handler = function () return data; end
				elseif event_name:sub(-2, -1) == "/*" then
					local base_path_len = #event_name:match("/.+$");
					local _handler = handler;
					handler = function (_event)
						local path = _event.request.path:sub(base_path_len);
						return _handler(_event, path);
					end;
					module:hook_object_event(server, event_name:sub(1, -3), redir_handler, -1);
				elseif event_name:sub(-1, -1) == "/" then
					module:hook_object_event(server, event_name:sub(1, -2), redir_handler, -1);
				end
				if not app_handlers[event_name] then
					app_handlers[event_name] = {
						main = handler;
						cors = cors_handler;
						options = options_handler;
					};
					module:hook_object_event(server, event_name, handler);
					module:hook_object_event(server, event_name, cors_handler, 1);
					module:hook_object_event(server, options_event_name, options_handler, -1);
				else
					module:log("warn", "App %s added handler twice for '%s', ignoring", app_name, event_name);
				end
			else
				module:log("error", "Invalid route in %s, %q. See https://prosody.im/doc/developers/http#routes", app_name, key);
			end
		end
		local services = portmanager.get_active_services();
		if services:get("https") or services:get("http") then
			module:log("info", "Serving '%s' at %s", app_name, module:http_url(app_name, app_path));
		else
			module:log("warn", "Not listening on any ports, '%s' will be unreachable", app_name);
		end
	end

	local function http_app_removed(event)
		local app_handlers = apps[event.item.name];
		apps[event.item.name] = nil;
		for event_name, handlers in pairs(app_handlers) do
			module:unhook_object_event(server, event_name, handlers.main);
			module:unhook_object_event(server, event_name, handlers.cors);
			local options_event_name = event_name:gsub("^%S+", "OPTIONS");
			module:unhook_object_event(server, options_event_name, handlers.options);
		end
	end

	module:handle_items("http-provider", http_app_added, http_app_removed);

	if host ~= "*" then
		server.add_host(host);
		function module.unload()
			server.remove_host(host);
		end
	end
end

module.add_host(module); -- set up handling on global context too

local trusted_proxies = module:get_option_set("trusted_proxies", { "127.0.0.1", "::1" })._items;

local function is_trusted_proxy(ip)
	local parsed_ip = new_ip(ip)
	for trusted_proxy in trusted_proxies do
		if match_ip(parsed_ip, parse_cidr(trusted_proxy)) then
			return true;
		end
	end
	return false
end

local function get_ip_from_request(request)
	local ip = request.conn:ip();
	local forwarded_for = request.headers.x_forwarded_for;
	if forwarded_for then
		-- luacheck: ignore 631
		-- This logic looks weird at first, but it makes sense.
		-- The for loop will take the last non-trusted-proxy IP from `forwarded_for`.
		-- We append the original request IP to the header. Then, since the last IP wins, there are two cases:
		-- Case a) The original request IP is *not* in trusted proxies, in which case the X-Forwarded-For header will, effectively, be ineffective; the original request IP will win because it overrides any other IP in the header.
		-- Case b) The original request IP is in trusted proxies. In that case, the if branch in the for loop will skip the last IP, causing it to be ignored. The second-to-last IP will be taken instead.
		-- Case c) If the second-to-last IP is also a trusted proxy, it will also be ignored, iteratively, up to the last IP which isn’t in trusted proxies.
		-- Case d) If all IPs are in trusted proxies, something went obviously wrong and the logic never overwrites `ip`, leaving it at the original request IP.
		forwarded_for = forwarded_for..", "..ip;
		for forwarded_ip in forwarded_for:gmatch("[^%s,]+") do
			if not is_trusted_proxy(forwarded_ip) then
				ip = forwarded_ip;
			end
		end
	end
	return ip;
end

module:wrap_object_event(server._events, false, function (handlers, event_name, event_data)
	local request = event_data.request;
	if request then
		-- Not included in eg http-error events
		request.ip = get_ip_from_request(request);
	end
	return handlers(event_name, event_data);
end);

module:provides("net", {
	name = "http";
	listener = server.listener;
	default_port = 5280;
	multiplex = {
		pattern = "^[A-Z]";
	};
});

module:provides("net", {
	name = "https";
	listener = server.listener;
	default_port = 5281;
	encryption = "ssl";
	multiplex = {
		protocol = "http/1.1";
		pattern = "^[A-Z]";
	};
});
