local hashes = require "util.hashes";

local cache = require "util.cache";

local http = require "util.http";

local jid = require "util.jid";

local json = require "util.json";

local usermanager = require "core.usermanager";

local errors = require "util.error";

local url = require "socket.url";

local uuid = require "util.uuid";

local encodings = require "util.encodings";

local base64 = encodings.base64;

local tokens = module:depends("tokenauth");

local clients = module:open_store("oauth2_clients", "map");

local function filter_scopes(request_jid, requested_scope_string) --luacheck: ignore 212/requested_scope_string

	-- We currently don't really support scopes, so override

	-- to whatever real permissions the user has

	if usermanager.is_admin(request_jid, module.host) then

		return "prosody:scope:admin";

	end

	return "prosody:scope:default";

end

local function code_expired(code)

	return os.difftime(os.time(), code.issued) > 120;

end

local codes = cache.new(10000, function (_, code)

	return code_expired(code)

end);

module:add_timer(900, function()

	local k, code = codes:tail();

	while code and code_expired(code) do

		codes:set(k, nil);

		k, code = codes:tail();

	end

	return 900;

end)

local function oauth_error(err_name, err_desc)

	return errors.new({

		type = "modify";

		condition = "bad-request";

		code = err_name == "invalid_client" and 401 or 400;

		text = err_desc and (err_name..": "..err_desc) or err_name;

		extra = { oauth2_response = { error = err_name, error_description = err_desc } };

	});

end

local function new_access_token(token_jid, scope, ttl)

	local token = tokens.create_jid_token(token_jid, token_jid, scope, ttl);

	return {

		token_type = "bearer";

		access_token = token;

		expires_in = ttl;

		scope = scope;

		-- TODO: include refresh_token when implemented

	};

end

local grant_type_handlers = {};

local response_type_handlers = {};

function grant_type_handlers.password(params)

	local request_jid = assert(params.username, oauth_error("invalid_request", "missing 'username' (JID)"));

	local request_password = assert(params.password, oauth_error("invalid_request", "missing 'password'"));

	local request_username, request_host, request_resource = jid.prepped_split(request_jid);

	if not (request_username and request_host) or request_host ~= module.host then

		return oauth_error("invalid_request", "invalid JID");

	end

	if not usermanager.test_password(request_username, request_host, request_password) then

		return oauth_error("invalid_grant", "incorrect credentials");

	end

	local granted_jid = jid.join(request_username, request_host, request_resource);

	local granted_scopes = filter_scopes(granted_jid, params.scope);

	return json.encode(new_access_token(granted_jid, granted_scopes, nil));

end

function response_type_handlers.code(params, granted_jid)

	if not params.client_id then return oauth_error("invalid_request", "missing 'client_id'"); end

	if not params.redirect_uri then return oauth_error("invalid_request", "missing 'redirect_uri'"); end

	local client_owner, client_host, client_id = jid.prepped_split(params.client_id);

	if client_host ~= module.host then

		return oauth_error("invalid_client", "incorrect credentials");

	end

	local client, err = clients:get(client_owner, client_id);

	if err then error(err); end

	if not client then

		return oauth_error("invalid_client", "incorrect credentials");

	end

	local granted_scopes = filter_scopes(granted_jid, params.scope);

	local code = uuid.generate();

	assert(codes:set(params.client_id .. "#" .. code, {

		issued = os.time();

		granted_jid = granted_jid;

		granted_scopes = granted_scopes;

	}));

	local redirect = url.parse(params.redirect_uri);

	local query = http.formdecode(redirect.query or "");

	if type(query) ~= "table" then query = {}; end

	table.insert(query, { name = "code", value = code })

	if params.state then

		table.insert(query, { name = "state", value = params.state });

	end

	redirect.query = http.formencode(query);

	return {

		status_code = 302;

		headers = {

			location = url.build(redirect);

		};

	}

end

local pepper = module:get_option_string("oauth2_client_pepper", "");

local function verify_secret(stored, salt, i, secret)

	return base64.decode(stored) == hashes.pbkdf2_hmac_sha256(secret, salt .. pepper, i);

end

function grant_type_handlers.authorization_code(params)

	if not params.client_id then return oauth_error("invalid_request", "missing 'client_id'"); end

	if not params.client_secret then return oauth_error("invalid_request", "missing 'client_secret'"); end

	if not params.code then return oauth_error("invalid_request", "missing 'code'"); end

	if params.scope and params.scope ~= "" then

		return oauth_error("invalid_scope", "unknown scope requested");

	end

	local client_owner, client_host, client_id = jid.prepped_split(params.client_id);

	if client_host ~= module.host then

		module:log("debug", "%q ~= %q", client_host, module.host);

		return oauth_error("invalid_client", "incorrect credentials");

	end

	local client, err = clients:get(client_owner, client_id);

	if err then error(err); end

	if not client or not verify_secret(client.secret_hash, client.salt, client.iteration_count, params.client_secret) then

		module:log("debug", "client_secret mismatch");

		return oauth_error("invalid_client", "incorrect credentials");

	end

	local code, err = codes:get(params.client_id .. "#" .. params.code);

	if err then error(err); end

	if not code or type(code) ~= "table" or code_expired(code) then

		module:log("debug", "authorization_code invalid or expired: %q", code);

		return oauth_error("invalid_client", "incorrect credentials");

	end

	assert(codes:set(client_owner, client_id .. "#" .. params.code, nil));

	return json.encode(new_access_token(code.granted_jid, code.granted_scopes, nil));

end

local function check_credentials(request, allow_token)

	local auth_type, auth_data = string.match(request.headers.authorization, "^(%S+)%s(.+)$");

	if auth_type == "Basic" then

		local creds = base64.decode(auth_data);

		if not creds then return false; end

		local username, password = string.match(creds, "^([^:]+):(.*)$");

		if not username then return false; end

		username, password = encodings.stringprep.nodeprep(username), encodings.stringprep.saslprep(password);

		if not username then return false; end

		if not usermanager.test_password(username, module.host, password) then

			return false;

		end

		return username;

	elseif auth_type == "Bearer" and allow_token then

		local token_info = tokens.get_token_info(auth_data);

		if not token_info or not token_info.session or token_info.session.host ~= module.host then

			return false;

		end

		return token_info.session.username;

	end

	return nil;

end

if module:get_host_type() == "component" then

	local component_secret = assert(module:get_option_string("component_secret"), "'component_secret' is a required setting when loaded on a Component");

	function grant_type_handlers.password(params)

		local request_jid = assert(params.username, oauth_error("invalid_request", "missing 'username' (JID)"));

		local request_password = assert(params.password, oauth_error("invalid_request", "missing 'password'"));

		local request_username, request_host, request_resource = jid.prepped_split(request_jid);

		if params.scope then

			return oauth_error("invalid_scope", "unknown scope requested");

		end

		if not request_host or request_host ~= module.host then

			return oauth_error("invalid_request", "invalid JID");

		end

		if request_password == component_secret then

			local granted_jid = jid.join(request_username, request_host, request_resource);

			return json.encode(new_access_token(granted_jid, nil, nil));

		end

		return oauth_error("invalid_grant", "incorrect credentials");

	end

	-- TODO How would this make sense with components?

	-- Have an admin authenticate maybe?

	response_type_handlers.code = nil;

	grant_type_handlers.authorization_code = nil;

	check_credentials = function () return false end

end

function handle_token_grant(event)

	event.response.headers.content_type = "application/json";

	local params = http.formdecode(event.request.body);

	if not params then

		return oauth_error("invalid_request");

	end

	local grant_type = params.grant_type

	local grant_handler = grant_type_handlers[grant_type];

	if not grant_handler then

		return oauth_error("unsupported_grant_type");

	end

	return grant_handler(params);

end

local function handle_authorization_request(event)

	local request, response = event.request, event.response;

	if not request.headers.authorization then

		response.headers.www_authenticate = string.format("Basic realm=%q", module.host.."/"..module.name);

		return 401;

	end

	local user = check_credentials(request);

	if not user then

		return 401;

	end

	-- TODO ask user for consent here

	if not request.url.query then

		response.headers.content_type = "application/json";

		return oauth_error("invalid_request");

	end

	local params = http.formdecode(request.url.query);

	if not params then

		return oauth_error("invalid_request");

	end

	local response_type = params.response_type;

	local response_handler = response_type_handlers[response_type];

	if not response_handler then

		response.headers.content_type = "application/json";

		return oauth_error("unsupported_response_type");

	end

	return response_handler(params, jid.join(user, module.host));

end

local function handle_revocation_request(event)

	local request, response = event.request, event.response;

	if not request.headers.authorization then

		response.headers.www_authenticate = string.format("Basic realm=%q", module.host.."/"..module.name);

		return 401;

	elseif request.headers.content_type ~= "application/x-www-form-urlencoded"

	or not request.body or request.body == "" then

		return 400;

	end

	local user = check_credentials(request, true);

	if not user then

		return 401;

	end

	local form_data = http.formdecode(event.request.body);

	if not form_data or not form_data.token then

		return 400;

	end

	local ok, err = tokens.revoke_token(form_data.token);

	if not ok then

		module:log("warn", "Unable to revoke token: %s", tostring(err));

		return 500;

	end

	return 200;

end

module:depends("http");

module:provides("http", {

	route = {

		["POST /token"] = handle_token_grant;

		["GET /authorize"] = handle_authorization_request;

		["POST /revoke"] = handle_revocation_request;

	};

});

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

module:hook_object_event(http_server, "http-error", function (event)

	local oauth2_response = event.error and event.error.extra and event.error.extra.oauth2_response;

	if not oauth2_response then

		return;

	end

	event.response.headers.content_type = "application/json";

	event.response.status_code = event.error.code or 400;

	return json.encode(oauth2_response);

end, 5);