-module(atproto_codegen@emit@union).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/atproto_codegen/emit/union.gleam").
-export([emit_union/4]).
-export_type([union_parts/0, variant/0]).

-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(
    " Open-union synthesis: a named type per union field with one variant per\n"
    " ref plus `Other(Dynamic)`, `$type`-dispatching codecs included.\n"
    "\n"
    " The three parts (type, encoder, decoder) are returned separately rather\n"
    " than as one joined string: the `types` plugin renders the first two, the\n"
    " `decode-json` plugin the third, and the host interleaves them with the\n"
    " def's own type/encoder/decoder so the emitted file matches the order the\n"
    " monolithic emitter used to produce.\n"
).

-type union_parts() :: {union_parts, binary(), binary(), binary()}.

-type variant() :: {variant,
        binary(),
        binary(),
        list(binary()),
        binary(),
        binary()}.

-file("src/atproto_codegen/emit/union.gleam", 31).
-spec union_variant(
    atproto_codegen@config:config(),
    binary(),
    binary(),
    binary()
) -> variant().
union_variant(Cfg, Nsid, Name, Ref) ->
    R = atproto_codegen@naming:parse_ref(Nsid, Ref),
    Ref_name = atproto_codegen@naming:ref_type_name(erlang:element(5, Cfg), R),
    Qual = atproto_codegen@naming:qualifier(
        erlang:element(5, Cfg),
        Nsid,
        erlang:element(2, R)
    ),
    Type_keys = case erlang:element(3, R) of
        <<"main"/utf8>> ->
            [erlang:element(2, R),
                <<(erlang:element(2, R))/binary, "#main"/utf8>>];

        Def_name ->
            [<<<<(erlang:element(2, R))/binary, "#"/utf8>>/binary,
                    Def_name/binary>>]
    end,
    {variant,
        <<Name/binary, Ref_name/binary>>,
        <<Qual/binary, Ref_name/binary>>,
        Type_keys,
        <<<<Qual/binary, (justin:snake_case(Ref_name))/binary>>/binary,
            "_fields"/utf8>>,
        <<<<Qual/binary, (justin:snake_case(Ref_name))/binary>>/binary,
            "_decoder()"/utf8>>}.

-file("src/atproto_codegen/emit/union.gleam", 56).
?DOC(
    " An open union: one variant per ref plus `Other(Dynamic)`, which round-trips\n"
    " unrecognized `$type`s untouched instead of destroying them.\n"
).
-spec emit_union(
    atproto_codegen@config:config(),
    binary(),
    binary(),
    list(binary())
) -> union_parts().
emit_union(Cfg, Nsid, Name, Refs) ->
    Variants = gleam@list:map(
        Refs,
        fun(_capture) -> union_variant(Cfg, Nsid, Name, _capture) end
    ),
    Snake = justin:snake_case(Name),
    Type_lines = begin
        _pipe = gleam@list:map(
            Variants,
            fun(V) ->
                <<<<<<<<"  "/utf8, (erlang:element(2, V))/binary>>/binary,
                            "("/utf8>>/binary,
                        (erlang:element(3, V))/binary>>/binary,
                    ")"/utf8>>
            end
        ),
        lists:append(
            _pipe,
            [<<<<"  "/utf8, Name/binary>>/binary,
                    "Other(dynamic.Dynamic)"/utf8>>]
        )
    end,
    Type_def = <<<<<<<<"pub type "/utf8, Name/binary>>/binary, " {\n"/utf8>>/binary,
            (gleam@string:join(Type_lines, <<"\n"/utf8>>))/binary>>/binary,
        "\n}"/utf8>>,
    Encode_arms = begin
        _pipe@1 = gleam@list:map(
            Variants,
            fun(V@1) ->
                Primary@1 = case erlang:element(4, V@1) of
                    [Primary | _] -> Primary;
                    _assert_fail ->
                        erlang:error(#{gleam_error => let_assert,
                                    message => <<"Pattern match failed, no pattern matched the value."/utf8>>,
                                    file => <<?FILEPATH/utf8>>,
                                    module => <<"atproto_codegen/emit/union"/utf8>>,
                                    function => <<"emit_union"/utf8>>,
                                    line => 73,
                                    value => _assert_fail,
                                    start => 2295,
                                    'end' => 2333,
                                    pattern_start => 2306,
                                    pattern_end => 2319})
                end,
                <<<<<<<<<<<<"    "/utf8, (erlang:element(2, V@1))/binary>>/binary,
                                    "(inner) ->\n      json.object([\n        #(\"$type\", json.string(\""/utf8>>/binary,
                                (atproto_codegen@emit@exprs:escape(Primary@1))/binary>>/binary,
                            "\")),\n        .."/utf8>>/binary,
                        (erlang:element(5, V@1))/binary>>/binary,
                    "(inner)\n      ])"/utf8>>
            end
        ),
        lists:append(
            _pipe@1,
            [<<<<"    "/utf8, Name/binary>>/binary,
                    "Other(inner) -> internal.dynamic_to_json(inner)"/utf8>>]
        )
    end,
    Encoder = <<<<<<<<<<<<"pub fn encode_"/utf8, Snake/binary>>/binary,
                        "(value: "/utf8>>/binary,
                    Name/binary>>/binary,
                ") -> json.Json {\n  case value {\n"/utf8>>/binary,
            (gleam@string:join(Encode_arms, <<"\n"/utf8>>))/binary>>/binary,
        "\n  }\n}"/utf8>>,
    Decode_arms = begin
        _pipe@4 = gleam@list:map(
            Variants,
            fun(V@2) ->
                Patterns = begin
                    _pipe@2 = erlang:element(4, V@2),
                    _pipe@3 = gleam@list:map(
                        _pipe@2,
                        fun(K) ->
                            <<<<"\""/utf8,
                                    (atproto_codegen@emit@exprs:escape(K))/binary>>/binary,
                                "\""/utf8>>
                        end
                    ),
                    gleam@string:join(_pipe@3, <<" | "/utf8>>)
                end,
                <<<<<<<<<<<<"    "/utf8, Patterns/binary>>/binary,
                                    " -> decode.map("/utf8>>/binary,
                                (erlang:element(6, V@2))/binary>>/binary,
                            ", "/utf8>>/binary,
                        (erlang:element(2, V@2))/binary>>/binary,
                    ")"/utf8>>
            end
        ),
        lists:append(
            _pipe@4,
            [<<<<"    _ -> decode.map(decode.dynamic, "/utf8, Name/binary>>/binary,
                    "Other)"/utf8>>]
        )
    end,
    Decoder = <<<<<<<<<<<<"pub fn "/utf8, Snake/binary>>/binary,
                        "_decoder() -> decode.Decoder("/utf8>>/binary,
                    Name/binary>>/binary,
                ") {\n  use tag <- decode.optional_field(\"$type\", \"\", decode.string)\n  case tag {\n"/utf8>>/binary,
            (gleam@string:join(Decode_arms, <<"\n"/utf8>>))/binary>>/binary,
        "\n  }\n}"/utf8>>,
    {union_parts, Type_def, Encoder, Decoder}.