local base64 = require "prosody.util.encodings".base64;

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

local id = require "prosody.util.id";

local jid = require "prosody.util.jid";

local random = require "prosody.util.random";

local usermanager = require "prosody.core.usermanager";

local generate_identifier = require "prosody.util.id".short;

local token_store = module:open_store("auth_tokens", "keyval+");

local access_time_granularity = module:get_option_number("token_auth_access_time_granularity", 60);

local function select_role(username, host, role)

	if role then

		return prosody.hosts[host].authz.get_role_by_name(role);

	end

	return usermanager.get_user_role(username, host);

end

function create_grant(actor_jid, grant_jid, grant_ttl, grant_data)

	grant_jid = jid.prep(grant_jid);

	if not actor_jid or actor_jid ~= grant_jid and not jid.compare(grant_jid, actor_jid) then

		module:log("debug", "Actor <%s> is not permitted to create a token granting access to JID <%s>", actor_jid, grant_jid);

		return nil, "not-authorized";

	end

	local grant_username, grant_host, grant_resource = jid.split(grant_jid);

	if grant_host ~= module.host then

		return nil, "invalid-host";

	end

	local grant_id = id.short();

	local now = os.time();

	local grant = {

		id = grant_id;

		owner = actor_jid;

		created = now;

		expires = grant_ttl and (now + grant_ttl) or nil;

		accessed = now;

		jid = grant_jid;

		resource = grant_resource;

		data = grant_data;

		-- tokens[<hash-name>..":"..<secret>] = token_info

		tokens = {};

	};

	local ok, err = token_store:set_key(grant_username, grant_id, grant);

	if not ok then

		return nil, err;

	end

	module:fire_event("token-grant-created", {

		id = grant_id;

		grant = grant;

		username = grant_username;

		host = grant_host;

	});

	return grant;

end

function create_token(grant_jid, grant, token_role, token_ttl, token_purpose, token_data)

	if (token_data and type(token_data) ~= "table") or (token_purpose and type(token_purpose) ~= "string") then

		return nil, "bad-request";

	end

	local grant_username, grant_host = jid.split(grant_jid);

	if grant_host ~= module.host then

		return nil, "invalid-host";

	end

	if type(grant) == "string" then -- lookup by id

		grant = token_store:get_key(grant_username, grant);

		if not grant then return nil; end

	end

	if not grant.tokens then return nil, "internal-server-error"; end -- old-style token?

	local now = os.time();

	local expires = grant.expires; -- Default to same expiry as grant

	if token_ttl then -- explicit lifetime requested

		if expires then

			-- Grant has an expiry, so limit to that or shorter

			expires = math.min(now + token_ttl, expires);

		else

			-- Grant never expires, just use whatever expiry is requested for the token

			expires = now + token_ttl;

		end

	end

	local token_info = {

		role = token_role;

		created = now;

		expires = expires;

		purpose = token_purpose;

		data = token_data;

	};

	local token_secret = random.bytes(18);

	grant.tokens["sha256:"..hashes.sha256(token_secret, true)] = token_info;

	local ok, err = token_store:set_key(grant_username, grant.id, grant);

	if not ok then

		return nil, err;

	end

	local token_string = "secret-token:"..base64.encode("2;"..grant.id..";"..token_secret..";"..grant.jid);

	return token_string, token_info;

end

local function parse_token(encoded_token)

	if not encoded_token then return nil; end

	local encoded_data = encoded_token:match("^secret%-token:(.+)$");

	if not encoded_data then return nil; end

	local token = base64.decode(encoded_data);

	if not token then return nil; end

	local token_id, token_secret, token_jid = token:match("^2;([^;]+);([^;]+);(.+)$");

	if not token_id then return nil; end

	local token_user, token_host = jid.split(token_jid);

	return token_id, token_user, token_host, token_secret;

end

local function clear_expired_grant_tokens(grant, now)

	local updated;

	now = now or os.time();

	for secret, token_info in pairs(grant.tokens) do

		local expires = token_info.expires;

		if expires and expires < now then

			grant.tokens[secret] = nil;

			updated = true;

		end

	end

	return updated;

end

local function _get_validated_token_info(token_id, token_user, token_host, token_secret)

	if token_host ~= module.host then

		return nil, "invalid-host";

	end

	local grant, err = token_store:get_key(token_user, token_id);

	if not grant or not grant.tokens then

		if err then

			module:log("error", "Unable to read from token storage: %s", err);

			return nil, "internal-error";

		end

		module:log("warn", "Invalid token in storage (%s / %s)", token_user, token_id);

		return nil, "not-authorized";

	end

	-- Check provided secret

	local secret_hash = "sha256:"..hashes.sha256(token_secret, true);

	local token_info = grant.tokens[secret_hash];

	if not token_info then

		module:log("debug", "No tokens matched the given secret");

		return nil, "not-authorized";

	end

	-- Check expiry

	local now = os.time();

	if token_info.expires < now then

		module:log("debug", "Token has expired, cleaning it up");

		grant.tokens[secret_hash] = nil;

		token_store:set_key(token_user, token_id, grant);

		return nil, "not-authorized";

	end

	-- Invalidate grants from before last password change

	local account_info = usermanager.get_account_info(token_user, module.host);

	local password_updated_at = account_info and account_info.password_updated;

		module:log("debug", "Token grant issued before last password change, invalidating it now");

		token_store:set_key(token_user, token_id, nil);

		return nil, "not-authorized";

	end

	-- Update last access time if necessary

	local last_accessed = grant.accessed;

	if not last_accessed or (now - last_accessed) > access_time_granularity then

		grant.accessed = now;

		clear_expired_grant_tokens(grant); -- Clear expired tokens while we're here

		token_store:set_key(token_user, token_id, grant);

	end

	token_info.id = token_id;

	token_info.grant = grant;

	token_info.jid = grant.jid;

	return token_info;

end

function get_token_info(token)

	local token_id, token_user, token_host, token_secret = parse_token(token);

	if not token_id then

		module:log("warn", "Failed to verify access token: %s", token_user);

		return nil, "invalid-token-format";

	end

	return _get_validated_token_info(token_id, token_user, token_host, token_secret);

end

function get_token_session(token, resource)

	local token_id, token_user, token_host, token_secret = parse_token(token);

	if not token_id then

		module:log("warn", "Failed to verify access token: %s", token_user);

		return nil, "invalid-token-format";

	end

	local token_info, err = _get_validated_token_info(token_id, token_user, token_host, token_secret);

	if not token_info then return nil, err; end

	return {

		username = token_user;

		host = token_host;

		resource = token_info.resource or resource or generate_identifier();

		role = select_role(token_user, token_host, token_info.role);

	};

end

function revoke_token(token)

	local token_id, token_user, token_host = parse_token(token);

	if not token_id then

		module:log("warn", "Failed to verify access token: %s", token_user);

		return nil, "invalid-token-format";

	end

	if token_host ~= module.host then

		return nil, "invalid-host";

	end

	local ok, err = token_store:set_key(token_user, token_id, nil);

	if not ok then

		return nil, err;

	end

	module:fire_event("token-grant-revoked", { id = token_id, username = token_user, host = token_host });

	return true;

end

function sasl_handler(auth_provider, purpose, extra)

	return function (sasl, token, realm, _authzid)

		local token_info, err = get_token_info(token);

		if not token_info then

			module:log("debug", "SASL handler failed to verify token: %s", err);

			return nil, nil, extra;

		end

		local token_user, token_host, resource = jid.split(token_info.grant.jid);

		if realm ~= token_host or (purpose and token_info.purpose ~= purpose) then

			return nil, nil, extra;

		end

		if auth_provider.is_enabled and not auth_provider.is_enabled(token_user) then

			return true, false, token_info;

		end

		sasl.resource = resource;

		sasl.token_info = token_info;

		return token_user, true, token_info;

	end;

end