-module(libero@remote_data).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/libero/remote_data.gleam").
-export([map/2, map2/3, 'try'/2, map_error/2, unwrap/2, to_option/1, fold/5, format_transport_error/1, format_failure/2]).
-export_type([remote_data/2, rpc_outcome/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(
    " Typed states for async data loading.\n"
    " Inspired by Elm's RemoteData package.\n"
    "\n"
    " Use instead of Bool flags + Option fields for data that loads\n"
    " asynchronously. The view pattern matches directly on the state -\n"
    " impossible to show stale data while loading or forget to handle errors.\n"
    "\n"
    " Generated RPC stubs build `RpcData` directly: the per-endpoint\n"
    " `decode_response_<fn>` FFI returns an `RpcData(payload, domain)` that\n"
    " the page stores in its model. `NotAsked` and `Loading` are page-lifecycle\n"
    " states the page sets itself in `init` and `update`. `Failure` carries\n"
    " either a `TransportError(RpcError)` (framework / wire-level) or a typed\n"
    " `DomainError(domain)` from the handler's own error type.\n"
).

-type remote_data(NEP, NEQ) :: not_asked |
    loading |
    {failure, NEQ} |
    {success, NEP}.

-type rpc_outcome(NER) :: {transport_error, libero@error:rpc_error()} |
    {domain_error, NER}.

-file("src/libero/remote_data.gleam", 43).
?DOC(" Apply a function to the success value.\n").
-spec map(remote_data(NEX, NEY), fun((NEX) -> NFB)) -> remote_data(NFB, NEY).
map(Data, Transform) ->
    case Data of
        not_asked ->
            not_asked;

        loading ->
            loading;

        {failure, Error} ->
            {failure, Error};

        {success, Value} ->
            {success, Transform(Value)}
    end.

-file("src/libero/remote_data.gleam", 69).
?DOC(
    " Combine two independent `RemoteData` values with a function. Returns\n"
    " `Success` only when both inputs are `Success`. Short-circuits on the\n"
    " first `Failure` found (in either position), or `Loading` if either is\n"
    " `Loading` and neither has failed.\n"
    " When both inputs are `Failure`, the left-hand error is returned.\n"
    "\n"
    " Useful in `init` to batch parallel RPC calls into a single state\n"
    " transition:\n"
    "\n"
    " ```\n"
    " let result = remote_data.map2(config_rd, items_rd, fn(c, i) {\n"
    "   #(c, i)\n"
    " })\n"
    " ```\n"
).
-spec map2(remote_data(NFE, NFF), remote_data(NFI, NFF), fun((NFE, NFI) -> NFL)) -> remote_data(NFL, NFF).
map2(A, B, Combine) ->
    case {A, B} of
        {{success, A@1}, {success, B@1}} ->
            {success, Combine(A@1, B@1)};

        {{failure, E}, _} ->
            {failure, E};

        {_, {failure, E@1}} ->
            {failure, E@1};

        {loading, _} ->
            loading;

        {_, loading} ->
            loading;

        {_, _} ->
            not_asked
    end.

-file("src/libero/remote_data.gleam", 91).
?DOC(
    " Monadic bind for chaining dependent async work. When the data is\n"
    " `Success`, apply `f` to the value and return its result. Otherwise\n"
    " propagate the current state unchanged.\n"
    "\n"
    " RPC calls that depend on a prior result usually live in separate\n"
    " `update` arms rather than inside `init`, so this is less common than\n"
    " `map` or `map2` — but available when callers need it.\n"
).
-spec 'try'(remote_data(NFO, NFP), fun((NFO) -> remote_data(NFS, NFP))) -> remote_data(NFS, NFP).
'try'(Data, F) ->
    case Data of
        {success, Value} ->
            F(Value);

        not_asked ->
            not_asked;

        loading ->
            loading;

        {failure, Error} ->
            {failure, Error}
    end.

-file("src/libero/remote_data.gleam", 104).
?DOC(" Apply a function to the error value.\n").
-spec map_error(remote_data(NFX, NFY), fun((NFY) -> NGB)) -> remote_data(NFX, NGB).
map_error(Data, Transform) ->
    case Data of
        not_asked ->
            not_asked;

        loading ->
            loading;

        {failure, Error} ->
            {failure, Transform(Error)};

        {success, Value} ->
            {success, Value}
    end.

-file("src/libero/remote_data.gleam", 117).
?DOC(" Extract the success value, or return a default.\n").
-spec unwrap(remote_data(NGE, any()), NGE) -> NGE.
unwrap(Data, Default) ->
    case Data of
        {success, Value} ->
            Value;

        _ ->
            Default
    end.

-file("src/libero/remote_data.gleam", 125).
?DOC(" Convert to Option - Some for Success, None for everything else.\n").
-spec to_option(remote_data(NGI, any())) -> gleam@option:option(NGI).
to_option(Data) ->
    case Data of
        {success, Value} ->
            {some, Value};

        _ ->
            none
    end.

-file("src/libero/remote_data.gleam", 135).
?DOC(
    " Reduce all four states into a single value. Each case provides its\n"
    " own callback so the caller can return whatever shape they need\n"
    " (e.g. an `Element(msg)` for a Lustre view).\n"
).
-spec fold(
    remote_data(NGN, NGO),
    fun(() -> NGR),
    fun(() -> NGR),
    fun((NGO) -> NGR),
    fun((NGN) -> NGR)
) -> NGR.
fold(Data, On_not_asked, On_loading, On_failure, On_success) ->
    case Data of
        not_asked ->
            On_not_asked();

        loading ->
            On_loading();

        {failure, Error} ->
            On_failure(Error);

        {success, Value} ->
            On_success(Value)
    end.

-file("src/libero/remote_data.gleam", 153).
?DOC(
    " Default formatter for framework-level transport errors. Useful when\n"
    " the caller wants a single string for `RpcError` values rather than\n"
    " pattern-matching each variant.\n"
).
-spec format_transport_error(libero@error:rpc_error()) -> binary().
format_transport_error(Err) ->
    case Err of
        {internal_error, _, Message} ->
            Message;

        {unknown_function, Name} ->
            <<"Unknown RPC: "/utf8, Name/binary>>;

        malformed_request ->
            <<"Malformed request"/utf8>>
    end.

-file("src/libero/remote_data.gleam", 185).
?DOC(
    " Render an `RpcOutcome` as a single user-facing string. The caller\n"
    " supplies a formatter for their domain error type; transport errors\n"
    " are routed through `format_transport_error`.\n"
    "\n"
    " Use this anywhere two arms differ only by which formatter runs. In\n"
    " views:\n"
    "\n"
    " ```\n"
    " Failure(outcome) -> render(format_failure(outcome, format_my_error))\n"
    " ```\n"
    "\n"
    " In an update reducer that surfaces a flash message:\n"
    "\n"
    " ```\n"
    " LoadResult(Failure(outcome)) -> #(\n"
    "   model,\n"
    "   effect.none(),\n"
    "   Some(#(Danger, format_failure(outcome, format_my_error))),\n"
    " )\n"
    " ```\n"
    "\n"
    " The match becomes exhaustive over `RpcOutcome`, so no\n"
    " `Failure(_)` catch-all is needed and the per-tier `DomainError(err)` /\n"
    " `TransportError(rpc_err)` arms collapse into one.\n"
).
-spec format_failure(rpc_outcome(NGS), fun((NGS) -> binary())) -> binary().
format_failure(Outcome, Format_domain) ->
    case Outcome of
        {transport_error, Err} ->
            format_transport_error(Err);

        {domain_error, Err@1} ->
            Format_domain(Err@1)
    end.