-module(gorrion@loader).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/gorrion/loader.gleam").
-export([load_migrations/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(
    " Loads migration SQL files from disk.\n"
    " Convention: {NNN}_{name}.sql (up) / {NNN}_{name}_down.sql (optional rollback)\n"
).

-file("src/gorrion/loader.gleam", 43).
-spec parse_migration(binary(), binary()) -> {ok, gorrion@types:migration()} |
    {error, gorrion@types:migration_error()}.
parse_migration(Directory, Filename) ->
    Base = gleam@string:drop_end(Filename, string:length(<<".sql"/utf8>>)),
    Down_filename = <<Base/binary, "_down.sql"/utf8>>,
    case gleam@string:split_once(Base, <<"_"/utf8>>) of
        {error, _} ->
            {error,
                {file_error,
                    <<"Invalid migration filename: "/utf8, Filename/binary>>}};

        {ok, {Version_str, Name}} ->
            case gleam_stdlib:parse_int(Version_str) of
                {error, _} ->
                    {error,
                        {file_error,
                            <<"Invalid version number in filename: "/utf8,
                                Filename/binary>>}};

                {ok, Version} ->
                    Up_path = <<<<Directory/binary, "/"/utf8>>/binary,
                        Filename/binary>>,
                    Down_path = <<<<Directory/binary, "/"/utf8>>/binary,
                        Down_filename/binary>>,
                    case simplifile:read(Up_path) of
                        {error, E} ->
                            {error,
                                {file_error,
                                    <<<<<<"Cannot read "/utf8, Up_path/binary>>/binary,
                                            ": "/utf8>>/binary,
                                        (gleam@string:inspect(E))/binary>>}};

                        {ok, Up_sql} ->
                            Down_sql = case simplifile:read(Down_path) of
                                {ok, Sql} ->
                                    Sql;

                                {error, _} ->
                                    <<""/utf8>>
                            end,
                            {ok, {migration, Version, Name, Up_sql, Down_sql}}
                    end
            end
    end.

-file("src/gorrion/loader.gleam", 14).
?DOC(
    " Load all migrations from .sql files in the given directory.\n"
    " Scans for *.sql files (excluding *_down.sql), and optionally pairs\n"
    " each with a *_down.sql companion. If no down file exists, down = \"\".\n"
).
-spec load_migrations(binary()) -> {ok, list(gorrion@types:migration())} |
    {error, gorrion@types:migration_error()}.
load_migrations(Directory) ->
    case simplifile_erl:read_directory(Directory) of
        {error, E} ->
            {error,
                {file_error,
                    <<<<<<"Cannot read migrations directory '"/utf8,
                                Directory/binary>>/binary,
                            "': "/utf8>>/binary,
                        (gleam@string:inspect(E))/binary>>}};

        {ok, Files} ->
            Up_files = begin
                _pipe = Files,
                _pipe@1 = gleam@list:filter(
                    _pipe,
                    fun(F) ->
                        gleam_stdlib:string_ends_with(F, <<".sql"/utf8>>)
                        andalso not gleam_stdlib:string_ends_with(
                            F,
                            <<"_down.sql"/utf8>>
                        )
                    end
                ),
                gleam@list:sort(_pipe@1, fun gleam@string:compare/2)
            end,
            _pipe@2 = Up_files,
            _pipe@3 = gleam@list:try_map(
                _pipe@2,
                fun(F@1) -> parse_migration(Directory, F@1) end
            ),
            gleam@result:map(
                _pipe@3,
                fun(Migrations) ->
                    gleam@list:sort(
                        Migrations,
                        fun(A, B) ->
                            gleam@int:compare(
                                erlang:element(2, A),
                                erlang:element(2, B)
                            )
                        end
                    )
                end
            )
    end.