%%-------------------------------------------------------------------
%% @doc `ldclient_config' module
%%
%% Acts as a storage interface for SDK client instance settings.
%% @end
%%-------------------------------------------------------------------

-module(ldclient_config).

%% API
-export([init/0]).
-export([parse_options/2]).
-export([get_registered_tags/0]).
-export([get_value/2]).
-export([register/2]).
-export([unregister/1]).
-export([get_user_agent/0]).
-export([get_event_schema/0]).
-export([tls_basic_linux_options/0]).
-export([tls_ca_certfile_options/1]).
-export([with_tls_revocation/1]).
-export([tls_basic_certifi_options/0]).
-export([tls_basic_options/0]).
-export([get_version/0]).

-type http_options() :: #{
    tls_options => [ssl:tls_client_option()] | undefined,
    connect_timeout => pos_integer() | undefined,
    custom_headers => [{Key :: string(), Value:: string()}] | undefined
}.

-type app_info() :: #{
    id => binary(),
    %% A unique identifier representing the application where the LaunchDarkly SDK is running.
    %%
    %% This can be specified as any string value, up to 64 characters in length, as long as it only uses the following
    %% characters: ASCII letters, ASCII digits, period, hyphen, underscore. A string containing any other characters
    %% will be ignored.
    %%
    %% Example: `authentication-service'
    version => binary()
    %% A unique identifier representing the version of the application where the LaunchDarkly SDK is running.
    %%
    %% This can be specified as any string value, up to 64 characters in length, as long as it only uses the following
    %% characters: ASCII letters, ASCII digits, period, hyphen, underscore. A string containing any other characters
    %% will be ignored.
    %%
    %% Example: `1.0.0' (standard version string) or `abcdef' (sha prefix)
}.
%% Information about the application where the LaunchDarkly SDK is running.

%% Types
-type instance() :: #{
    sdk_key => string(),
    base_uri => string(),
    events_uri => string(),
    stream_uri => string(),
    feature_store => atom(),
    events_capacity => pos_integer(),
    events_flush_interval => pos_integer(),
    events_dispatcher => atom(),
    context_keys_capacity => pos_integer(),
    private_attributes => private_attributes(),
    stream => boolean(),
    polling_interval => pos_integer(),
    polling_update_requestor => atom(),
    offline => boolean(),
    redis_host => string(),
    redis_port => pos_integer(),
    redis_database => integer(),
    redis_password => string(),
    redis_prefix => string(),
    cache_ttl => integer(), % Any negative integer is parsed as an infinite TTL, zero is parsed as testing mode
    use_ldd => boolean(),
    send_events => boolean(),
    file_datasource => boolean(),
    file_paths => [string()],
    file_auto_update => boolean(),
    file_poll_interval => pos_integer(),
    file_allow_duplicate_keys => boolean(),
    testdata_tag => atom(),
    datasource => poll | stream | file | testdata | undefined,
    http_options => http_options(),
    stream_initial_retry_delay_ms => non_neg_integer(),
    application => app_info()
}.
% Settings stored for each running SDK instance

-type private_attributes() :: all | [ldclient_attribute_reference:attribute_reference()].

-export_type([private_attributes/0]).
-export_type([http_options/0]).

%% Constants
-define(DEFAULT_BASE_URI, "https://sdk.launchdarkly.com").
-define(DEFAULT_EVENTS_URI, "https://events.launchdarkly.com").
-define(DEFAULT_STREAM_URI, "https://stream.launchdarkly.com").
-define(DEFAULT_FEATURE_STORE, ldclient_storage_ets).
-define(DEFAULT_EVENTS_CAPACITY, 10000).
-define(DEFAULT_EVENTS_FLUSH_INTERVAL, 30000).
-define(DEFAULT_EVENTS_DISPATCHER, ldclient_event_dispatch_httpc).
-define(DEFAULT_CONTEXT_KEYS_CAPACITY, 1000).
-define(DEFAULT_PRIVATE_ATTRIBUTES, []).
-define(DEFAULT_STREAM, true).
-define(DEFAULT_POLLING_UPDATE_REQUESTOR, ldclient_update_requestor_httpc).
-define(MINIMUM_POLLING_INTERVAL, 30).
-define(USER_AGENT, "ErlangClient").
-define(VERSION, "2.0.3").
-define(EVENT_SCHEMA, "4").
-define(DEFAULT_OFFLINE, false).
-define(DEFAULT_REDIS_HOST, "127.0.0.1").
-define(DEFAULT_REDIS_PORT, 6379).
-define(DEFAULT_REDIS_DATABASE, 0).
-define(DEFAULT_REDIS_PASSWORD, "").
-define(DEFAULT_REDIS_PREFIX, "launchdarkly").
-define(DEFAULT_CACHE_TTL, 15).
-define(DEFAULT_USE_LDD, false).
-define(DEFAULT_SEND_EVENTS, true).
-define(DEFAULT_FILE_DATASOURCE, false).
-define(DEFAULT_FILE_PATHS, []).
-define(DEFAULT_FILE_AUTO_UPDATE, false).
-define(DEFAULT_FILE_POLL_INTERVAL, 1000).
-define(DEFAULT_FILE_ALLOW_DUPLICATE_KEYS, false).
-define(DEFAULT_TESTDATA_TAG, default).
-define(DEFAULT_DATASOURCE, undefined).
-define(DEFAULT_STREAM_RETRY_DELAY, 1000).

-define(HTTP_DEFAULT_TLS_OPTIONS, undefined).
-define(HTTP_DEFAULT_CONNECT_TIMEOUT, 2000).
-define(HTTP_DEFAULT_CUSTOM_HEADERS, undefined).
-define(HTTP_DEFAULT_LINUX_CASTORE, "/etc/ssl/certs/ca-certificates.crt").

-define(APPLICATION_DEFAULT_OPTIONS, undefined).

%%===================================================================
%% API
%%===================================================================

%% @doc Initialize settings environment map
%%
%% Initializes an empty map for instance settings in application environment.
%% @end
-spec init() -> ok.
init() ->
    ok = ldclient_update_processor_state:init(),
    application:set_env(ldclient, instances, #{}).

%% @doc Parses given map of options
%% @private
%%
%% @end
-spec parse_options(SdkKey :: string(), Options :: map()) -> instance().
parse_options(SdkKey, Options) when is_list(SdkKey), is_map(Options) ->
    BaseUri = string:trim(maps:get(base_uri, Options, ?DEFAULT_BASE_URI), trailing, "/"),
    EventsUri = string:trim(maps:get(events_uri, Options, ?DEFAULT_EVENTS_URI), trailing, "/"),
    StreamUri = string:trim(maps:get(stream_uri, Options, ?DEFAULT_STREAM_URI), trailing, "/"),
    FeatureStore = maps:get(feature_store, Options, ?DEFAULT_FEATURE_STORE),
    EventsCapacity = maps:get(events_capacity, Options, ?DEFAULT_EVENTS_CAPACITY),
    EventsFlushInterval = maps:get(events_flush_interval, Options, ?DEFAULT_EVENTS_FLUSH_INTERVAL),
    EventsDispatcher = maps:get(events_dispatcher, Options, ?DEFAULT_EVENTS_DISPATCHER),
    ContextKeysCapacity = maps:get(context_keys_capacity, Options, ?DEFAULT_CONTEXT_KEYS_CAPACITY),
    PrivateAttributes = maps:get(private_attributes, Options, ?DEFAULT_PRIVATE_ATTRIBUTES),
    Stream = maps:get(stream, Options, ?DEFAULT_STREAM),
    PollingUpdateRequestor = maps:get(polling_update_requestor, Options, ?DEFAULT_POLLING_UPDATE_REQUESTOR),
    OfflineMode = maps:get(offline, Options, ?DEFAULT_OFFLINE),
    UseLdd = maps:get(use_ldd, Options, ?DEFAULT_USE_LDD),
    PollingInterval = lists:max([
        ?MINIMUM_POLLING_INTERVAL,
        maps:get(polling_interval, Options, ?MINIMUM_POLLING_INTERVAL)
    ]),
    RedisHost = maps:get(redis_host, Options, ?DEFAULT_REDIS_HOST),
    RedisPort = maps:get(redis_port, Options, ?DEFAULT_REDIS_PORT),
    RedisDatabase = maps:get(redis_database, Options, ?DEFAULT_REDIS_DATABASE),
    RedisPassword = maps:get(redis_password, Options, ?DEFAULT_REDIS_PASSWORD),
    RedisPrefix = maps:get(redis_prefix, Options, ?DEFAULT_REDIS_PREFIX),
    CacheTtl = maps:get(cache_ttl, Options, ?DEFAULT_CACHE_TTL),
    SendEvents = maps:get(send_events, Options, ?DEFAULT_SEND_EVENTS),
    FileDataSource = maps:get(file_datasource, Options, ?DEFAULT_FILE_DATASOURCE),
    FilePaths = maps:get(file_paths, Options, ?DEFAULT_FILE_PATHS),
    FileAutoUpdate = maps:get(file_auto_update, Options, ?DEFAULT_FILE_AUTO_UPDATE),
    FilePollInterval = maps:get(file_poll_interval, Options, ?DEFAULT_FILE_POLL_INTERVAL),
    FileAllowDuplicateKeys = maps:get(file_allow_duplicate_keys, Options, ?DEFAULT_FILE_ALLOW_DUPLICATE_KEYS),
    TestDataTag = maps:get(testdata_tag, Options, ?DEFAULT_TESTDATA_TAG),
    DataSource = maps:get(datasource, Options, ?DEFAULT_DATASOURCE),
    StreamInitialRetryDelayMs = maps:get(stream_initial_retry_delay_ms, Options, ?DEFAULT_STREAM_RETRY_DELAY),
    HttpOptions = parse_http_options(maps:get(http_options, Options, undefined)),
    AppInfo = parse_application_info(maps:get(application, Options, ?APPLICATION_DEFAULT_OPTIONS)),
    #{
        sdk_key => SdkKey,
        base_uri => BaseUri,
        events_uri => EventsUri,
        stream_uri => StreamUri,
        feature_store => FeatureStore,
        events_capacity => EventsCapacity,
        events_flush_interval => EventsFlushInterval,
        events_dispatcher => EventsDispatcher,
        context_keys_capacity => ContextKeysCapacity,
        private_attributes => parse_private_attributes(PrivateAttributes),
        stream => Stream,
        polling_update_requestor => PollingUpdateRequestor,
        offline => OfflineMode,
        polling_interval => PollingInterval,
        redis_host => RedisHost,
        redis_port => RedisPort,
        redis_database => RedisDatabase,
        redis_password => RedisPassword,
        redis_prefix => RedisPrefix,
        cache_ttl => CacheTtl,
        use_ldd => UseLdd,
        send_events => SendEvents,
        file_datasource => FileDataSource,
        file_paths => FilePaths,
        file_auto_update => FileAutoUpdate,
        file_poll_interval => FilePollInterval,
        file_allow_duplicate_keys => FileAllowDuplicateKeys,
        http_options => HttpOptions,
        testdata_tag => TestDataTag,
        datasource => DataSource,
        stream_initial_retry_delay_ms => StreamInitialRetryDelayMs,
        application => AppInfo
    }.

%% @doc Get all registered tags
%%
%% @end
-spec get_registered_tags() -> [atom()].
get_registered_tags() ->
    maps:keys(get_all()).

%% @doc Gets application environment variable value
%%
%% This is a convenience function to retrieve application environment variables
%% in one place. `Tag' is the instance tag. `Key' is the key of the
%% configuration option.
%% @end
-spec get_value(Tag :: atom(), Key :: atom()) -> undefined | term().
get_value(Tag, Key) when is_atom(Tag), is_atom(Key) ->
    {ok, Instances} = application:get_env(ldclient, instances),
    InstanceSettings = maps:get(Tag, Instances),
    maps:get(Key, InstanceSettings).

%% @doc Register settings for a new client instance
%%
%% @end
-spec register(Tag :: atom(), Settings :: instance()) -> ok.
register(Tag, Settings) when is_atom(Tag), is_map(Settings) ->
    Instances = get_all(),
    NewInstances = Instances#{Tag => Settings},
    application:set_env(ldclient, instances, NewInstances).

%% @doc Unregister settings for a client instance
%%
%% @end
-spec unregister(Tag :: atom()) -> ok.
unregister(Tag) when is_atom(Tag) ->
    NewInstances = maps:remove(Tag, get_all()),
    application:set_env(ldclient, instances, NewInstances).

-spec get_user_agent() -> string().
get_user_agent() ->
    ?USER_AGENT ++ "/" ++ ?VERSION.

-spec get_version() -> string().
get_version() ->
    ?VERSION.

-spec get_event_schema() -> string().
get_event_schema() ->
    ?EVENT_SCHEMA.

%% @doc Provide basic options for using TLS.
%% This will try to use the a certificate store located at
%% /etc/ssl/certs/ca-certificates.crt, but if that file
%% does not exist, then it will use the bundled certifi store.
%%
%% @end
-spec tls_basic_options() -> [ssl:tls_client_option()].
tls_basic_options() ->
    tls_basic_options(filelib:is_regular(?HTTP_DEFAULT_LINUX_CASTORE)).

%% @doc Provide basic options for using TLS with the default linux store.
%% This will try to use the a certificate store located at
%% /etc/ssl/certs/ca-certificates.crt.
%%
%% @end
-spec tls_basic_linux_options() -> [ssl:tls_client_option()].
tls_basic_linux_options() ->
    [
        {cacertfile, ?HTTP_DEFAULT_LINUX_CASTORE}
        | tls_base_options()].

%% @doc Provide basic options for using TLS with the given store.
%%
%% @end
-spec tls_ca_certfile_options(CaStorePath :: string()) -> [ssl:tls_client_option()].
tls_ca_certfile_options(CaStorePath) ->
    [
        {cacertfile, CaStorePath}
        | tls_base_options()].

%% @doc Append the specified TLS options with certificate revocation.
%% The crl_cache does not actually cache at this time, so this will
%% result in an additional request per TLS handshake.
%%
%% @end
-spec with_tls_revocation(Options :: [ssl:tls_client_option()]) -> [ssl:tls_client_option()].
with_tls_revocation(Options) ->
    [{crl_check, true},
        {crl_cache,
            {ssl_crl_cache,
                {internal, [{http, 1000}]}
            }
        } | Options].

%% @doc Provide basic TLS options using the bundled certifi store.
%%
%% @end
-spec tls_basic_certifi_options() -> [ssl:tls_client_option()].
tls_basic_certifi_options() ->
    CaCerts = certifi:cacerts(),
    [
        {cacerts, CaCerts}
        | tls_base_options()].

%%===================================================================
%% Internal functions
%%===================================================================

-spec parse_application_info(ApplicationInfoMap :: map()) -> app_info() | undefined.
parse_application_info(undefined) -> undefined;
parse_application_info(ApplicationInfoMap) ->
    Id = maps:get(id, ApplicationInfoMap, undefined),
    Version = maps:get(version, ApplicationInfoMap, undefined),
    set_valid_tag(version, Version,
        set_valid_tag(id, Id, undefined)).

-spec set_valid_tag(Key :: atom(), Value :: binary() | undefined, MapOrUndefined :: map() | undefined) -> app_info() | undefined.
set_valid_tag(_Key, _Value = undefined, MapOrUndefined) -> MapOrUndefined;
set_valid_tag(Key, Value, MapOrUndefined) ->
    case validate_tag_value(Value) of
        true ->
            case is_map(MapOrUndefined) of
                true -> MapOrUndefined#{Key => Value};
                false -> #{Key => Value}
            end;
        false ->
            error_logger:warning_msg("The application ~p was invalid. Must only contain letters, numbers, ., _ or -,"
            " be 64 characters or less, and cannot be an empty string.", [Key]),
            MapOrUndefined
    end.

-spec parse_http_options(HttpOptionsMap :: map()) -> http_options().
parse_http_options(undefined) -> parse_http_options(#{});
parse_http_options(HttpOptionsMap) ->
    TlsOptions = maps:get(tls_options, HttpOptionsMap, ?HTTP_DEFAULT_TLS_OPTIONS),
    ConnectTimeout = maps:get(connect_timeout, HttpOptionsMap, ?HTTP_DEFAULT_CONNECT_TIMEOUT),
    CustomHeaders = maps:get(custom_headers, HttpOptionsMap, ?HTTP_DEFAULT_CUSTOM_HEADERS),
    #{
        tls_options => TlsOptions,
        connect_timeout => ConnectTimeout,
        custom_headers => CustomHeaders
    }.

-spec get_all() -> #{Tag :: atom() => instance()}.
get_all() ->
    {ok, Instances} = application:get_env(ldclient, instances),
    Instances.

-spec tls_base_options() -> [ssl:tls_client_option()].
tls_base_options() ->
    DefaultCipherSuites = ssl:cipher_suites(default, 'tlsv1.2'),
    CipherSuites = ssl:filter_cipher_suites(DefaultCipherSuites, [
        {key_exchange, fun
                           (ecdhe_ecdsa) -> true;
                           (ecdhe_rsa) -> true;
                           (_) -> false
                       end
        },
        {mac, fun
                  (sha) -> false;
                  (_) -> true
              end
        }
    ]),

    [{verify, verify_peer},
        {ciphers, CipherSuites},
        {depth, 3},
        {customize_hostname_check, [
            {match_fun, public_key:pkix_verify_hostname_match_fun(https)}
        ]}].

-spec tls_basic_options(CaStoreExists :: boolean()) -> [ssl:tls_client_option()].
tls_basic_options(true) ->
    tls_basic_linux_options();
tls_basic_options(false) ->
    error_logger:warning_msg("TLS options are falling back to using the certifi store.
    This means the OS certificate store was not in the default location (/etc/ssl/certs/ca-certificates.crt).
    Please specify a custom location. You can use tls_ca_certfile_options, or fully specify the tls_options.
    You may see this warning in development on Mac/Windows."),
    tls_basic_certifi_options().

-spec validate_tag_value(Value :: binary() | undefined) -> boolean().
validate_tag_value(<<>>) -> false;
validate_tag_value(Value) when is_binary(Value) -> (byte_size(Value) =< 64) and valid_tag_chars(Value, true).

-spec valid_tag_chars(Value :: binary(), Valid :: boolean()) -> boolean().
valid_tag_chars(_Value, false) -> false;
valid_tag_chars(<<H, Remainder/binary>>, true) -> valid_tag_chars(Remainder, valid_tag_char(H));
valid_tag_chars(<<>>, true) -> true.

-spec valid_tag_char(Char :: integer()) -> boolean().
valid_tag_char($-) -> true;
valid_tag_char($.) -> true;
valid_tag_char($_) -> true;
valid_tag_char(H) ->
    ((H >= $0) and (H =< $9)) orelse %% Numbers
    ((H >= $A) and (H =< $Z)) orelse %% Capital letters
    ((H >= $a) and (H =< $z)). %% Lowercase letters

-spec parse_private_attributes(Attributes :: all | [binary() | ldclient_attribute_reference:attribute_reference()]) -> all | [ldclient_attribute_reference:attribute_reference()].
parse_private_attributes(all) -> all;
parse_private_attributes(Attributes) -> lists:map(fun ensure_attribute_reference/1, Attributes).

-spec ensure_attribute_reference(Attribute :: binary() | ldclient_attribute_reference:attribute_reference()) ->
    ldclient_attribute_reference:attribute_reference().
ensure_attribute_reference(Attribute) when is_binary(Attribute) -> ldclient_attribute_reference:new(Attribute);
ensure_attribute_reference(Attribute) -> Attribute.