-module(atproto_openapi@refs).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/atproto_openapi/refs.gleam").
-export([describe/1, canonicalize/2, component_key/1, schema_pointer/2, find_collisions/1]).
-export_type([ref/0, ref_error/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(
    " Lexicon ref -> OpenAPI component-key resolution. Every `PropRef`/\n"
    " `ItemRef`/`BodySchemaRef`/union member string in the AST is one of\n"
    " three spellings (`#localName`, `nsid#name`, bare `nsid`); this module\n"
    " reduces all three to the canonical `Ref(nsid, name)` pair (bare `nsid`\n"
    " canonicalizes to `Ref(nsid, \"main\")`) and derives the `components/\n"
    " schemas` key from it. OpenAPI component keys must match\n"
    " `^[a-zA-Z0-9._-]+$`, so the lexicon's `#` separator cannot appear in\n"
    " one; `_` is used instead, which is safe because NSID segments and def\n"
    " names never contain `_`. Two distinct canonical refs landing on the\n"
    " same key is a collision, reported via `find_collisions` rather than\n"
    " silently merged, mirroring how `atproto_sdl`/`atproto_mlf` report NSID\n"
    " collisions. See `docs/lexicon-openapi.md` for the full scheme.\n"
).

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

-type ref_error() :: empty_ref |
    {multiple_fragments, binary()} |
    {empty_local_name, binary()} |
    {key_collision, binary(), ref(), ref()}.

-file("src/atproto_openapi/refs.gleam", 51).
-spec ref_to_string(ref()) -> binary().
ref_to_string(Ref) ->
    <<<<(erlang:element(2, Ref))/binary, "#"/utf8>>/binary,
        (erlang:element(3, Ref))/binary>>.

-file("src/atproto_openapi/refs.gleam", 35).
-spec describe(ref_error()) -> binary().
describe(Error) ->
    case Error of
        empty_ref ->
            <<"empty ref"/utf8>>;

        {multiple_fragments, Raw} ->
            <<"malformed ref (more than one '#'): "/utf8, Raw/binary>>;

        {empty_local_name, Raw@1} ->
            <<"malformed ref (empty name after '#'): "/utf8, Raw@1/binary>>;

        {key_collision, Key, First, Second} ->
            <<<<<<<<<<<<"component key collision: "/utf8,
                                    (ref_to_string(First))/binary>>/binary,
                                " and "/utf8>>/binary,
                            (ref_to_string(Second))/binary>>/binary,
                        " both map to \""/utf8>>/binary,
                    Key/binary>>/binary,
                "\""/utf8>>
    end.

-file("src/atproto_openapi/refs.gleam", 58).
?DOC(
    " Resolve a raw ref string against the NSID of the doc it appears in.\n"
    " `#foo` resolves to `Ref(doc_id, \"foo\")`; `nsid#foo` to `Ref(nsid,\n"
    " \"foo\")`; bare `nsid` to `Ref(nsid, \"main\")`.\n"
).
-spec canonicalize(binary(), binary()) -> {ok, ref()} | {error, ref_error()}.
canonicalize(Raw, Doc_id) ->
    case Raw of
        <<""/utf8>> ->
            {error, empty_ref};

        _ ->
            case gleam@string:split(Raw, <<"#"/utf8>>) of
                [Nsid] ->
                    {ok, {ref, Nsid, <<"main"/utf8>>}};

                [Nsid@1, Name] ->
                    case Name of
                        <<""/utf8>> ->
                            {error, {empty_local_name, Raw}};

                        _ ->
                            case Nsid@1 of
                                <<""/utf8>> ->
                                    {ok, {ref, Doc_id, Name}};

                                _ ->
                                    {ok, {ref, Nsid@1, Name}}
                            end
                    end;

                _ ->
                    {error, {multiple_fragments, Raw}}
            end
    end.

-file("src/atproto_openapi/refs.gleam", 80).
?DOC(
    " The `components/schemas` key for a canonical ref: `nsid` when `name`\n"
    " is `\"main\"`, else `nsid <> \"_\" <> name`.\n"
).
-spec component_key(ref()) -> binary().
component_key(Ref) ->
    case erlang:element(3, Ref) of
        <<"main"/utf8>> ->
            erlang:element(2, Ref);

        Name ->
            <<<<(erlang:element(2, Ref))/binary, "_"/utf8>>/binary,
                Name/binary>>
    end.

-file("src/atproto_openapi/refs.gleam", 89).
?DOC(
    " The `$ref` JSON pointer for a raw ref string, resolved against the\n"
    " containing doc's id: `#/components/schemas/<component_key>`.\n"
).
-spec schema_pointer(binary(), binary()) -> {ok, binary()} |
    {error, ref_error()}.
schema_pointer(Raw, Doc_id) ->
    gleam@result:'try'(
        canonicalize(Raw, Doc_id),
        fun(Ref) ->
            {ok, <<"#/components/schemas/"/utf8, (component_key(Ref))/binary>>}
        end
    ).

-file("src/atproto_openapi/refs.gleam", 111).
-spec group_by_key(list(ref())) -> list({binary(), list(ref())}).
group_by_key(Refs) ->
    gleam@list:fold(
        Refs,
        [],
        fun(Acc, Ref) ->
            Key = component_key(Ref),
            case gleam@list:key_find(Acc, Key) of
                {ok, Existing} ->
                    gleam@list:key_set(Acc, Key, lists:append(Existing, [Ref]));

                {error, _} ->
                    gleam@list:key_set(Acc, Key, [Ref])
            end
        end
    ).

-file("src/atproto_openapi/refs.gleam", 98).
?DOC(
    " Report every case where two distinct canonical refs land on the same\n"
    " component key, rather than letting the second silently overwrite the\n"
    " first in the emitted `components/schemas` map. Empty when `refs` has\n"
    " no collisions.\n"
).
-spec find_collisions(list(ref())) -> list(ref_error()).
find_collisions(Refs) ->
    _pipe = Refs,
    _pipe@1 = gleam@list:unique(_pipe),
    _pipe@2 = group_by_key(_pipe@1),
    gleam@list:flat_map(
        _pipe@2,
        fun(Group) ->
            {Key, Members} = Group,
            case Members of
                [First | Rest] ->
                    gleam@list:map(
                        Rest,
                        fun(_capture) ->
                            {key_collision, Key, First, _capture}
                        end
                    );

                [] ->
                    []
            end
        end
    ).