-module(telega@storage).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/telega/storage.gleam").
-export([session_settings_from_storage/4, flow_storage_from_storage/1]).
-export_type([key_value_storage/1]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(
    " Unified key-value storage contract shared by sessions and flows.\n"
    "\n"
    " `KeyValueStorage` is the single low-level contract that every backend\n"
    " implements (ETS in core; Postgres/SQLite/Redis as separate packages).\n"
    " Values are opaque `String`s — callers serialize to/from JSON themselves.\n"
    "\n"
    " The two bridges below derive the higher-level `SessionSettings` and\n"
    " `FlowStorage` contracts from a single `KeyValueStorage`, so a bot only\n"
    " needs to wire up one backend for both sessions and flows.\n"
).

-type key_value_storage(BEWC) :: {key_value_storage,
        fun((binary()) -> {ok, gleam@option:option(binary())} | {error, BEWC}),
        fun((binary(), binary()) -> {ok, nil} | {error, BEWC}),
        fun((binary(), binary(), integer()) -> {ok, nil} | {error, BEWC}),
        fun((binary()) -> {ok, nil} | {error, BEWC}),
        fun((binary()) -> {ok, list(binary())} | {error, BEWC})}.

-file("src/telega/storage.gleam", 46).
?DOC(
    " Derive `SessionSettings` from a `KeyValueStorage`.\n"
    "\n"
    " Sessions are stored under the `session:` key namespace as JSON produced by\n"
    " `encode`. A decode failure on load is treated as \"no session\" so the bot\n"
    " falls back to `default` instead of crashing on a corrupt or migrated value.\n"
).
-spec session_settings_from_storage(
    key_value_storage(BEWD),
    fun((BEWF) -> gleam@json:json()),
    gleam@dynamic@decode:decoder(BEWF),
    fun(() -> BEWF)
) -> telega@bot:session_settings(BEWF, BEWD).
session_settings_from_storage(Storage, Encode, Decoder, Default) ->
    {session_settings,
        fun(Key, Session) ->
            Payload = begin
                _pipe = Encode(Session),
                gleam@json:to_string(_pipe)
            end,
            _pipe@1 = (erlang:element(3, Storage))(
                <<"session:"/utf8, Key/binary>>,
                Payload
            ),
            gleam@result:map(_pipe@1, fun(_) -> Session end)
        end,
        fun(Key@1) ->
            gleam@result:'try'(
                (erlang:element(2, Storage))(<<"session:"/utf8, Key@1/binary>>),
                fun(Maybe) -> case Maybe of
                        none ->
                            {ok, none};

                        {some, Raw} ->
                            case gleam@json:parse(Raw, Decoder) of
                                {ok, Session@1} ->
                                    {ok, {some, Session@1}};

                                {error, _} ->
                                    {ok, none}
                            end
                    end end
            )
        end,
        Default}.

-file("src/telega/storage.gleam", 79).
?DOC(
    " Derive `FlowStorage` from a `KeyValueStorage`.\n"
    "\n"
    " Flow instances are stored under the `flow:` key namespace as complete JSON\n"
    " (see `instance.to_json`), so subflows and parallel state survive restarts.\n"
    " `list_by_user` is served by `scan` over the namespace, replacing the\n"
    " secondary index used by the legacy ETS-only implementation.\n"
).
-spec flow_storage_from_storage(key_value_storage(BEWJ)) -> telega@flow@types:flow_storage(BEWJ).
flow_storage_from_storage(Storage) ->
    {flow_storage,
        fun(Inst) ->
            (erlang:element(3, Storage))(
                <<"flow:"/utf8, (erlang:element(2, Inst))/binary>>,
                telega@flow@instance:to_json_string(Inst)
            )
        end,
        fun(Id) ->
            gleam@result:'try'(
                (erlang:element(2, Storage))(<<"flow:"/utf8, Id/binary>>),
                fun(Maybe) -> case Maybe of
                        none ->
                            {ok, none};

                        {some, Raw} ->
                            case telega@flow@instance:from_json_string(Raw) of
                                {ok, Inst@1} ->
                                    {ok, {some, Inst@1}};

                                {error, _} ->
                                    {ok, none}
                            end
                    end end
            )
        end,
        fun(Id@1) ->
            (erlang:element(5, Storage))(<<"flow:"/utf8, Id@1/binary>>)
        end,
        fun(User_id, Chat_id) ->
            gleam@result:'try'(
                (erlang:element(6, Storage))(<<"flow:"/utf8>>),
                fun(Keys) ->
                    gleam@list:try_fold(
                        Keys,
                        [],
                        fun(Acc, Key) ->
                            gleam@result:'try'(
                                (erlang:element(2, Storage))(Key),
                                fun(Maybe@1) -> case Maybe@1 of
                                        none ->
                                            {ok, Acc};

                                        {some, Raw@1} ->
                                            case telega@flow@instance:from_json_string(
                                                Raw@1
                                            ) of
                                                {ok, Inst@2} ->
                                                    case (erlang:element(
                                                        4,
                                                        Inst@2
                                                    )
                                                    =:= User_id)
                                                    andalso (erlang:element(
                                                        5,
                                                        Inst@2
                                                    )
                                                    =:= Chat_id) of
                                                        true ->
                                                            {ok, [Inst@2 | Acc]};

                                                        false ->
                                                            {ok, Acc}
                                                    end;

                                                {error, _} ->
                                                    {ok, Acc}
                                            end
                                    end end
                            )
                        end
                    )
                end
            )
        end}.