-module(migrant@database).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([exec/2, 'query'/4, create_migrations_table/2, filter_applied_migrations/3, apply_migrations/2]).

-spec exec(sqlight:connection(), binary()) -> {ok, nil} |
    {error, migrant@types:error()}.
exec(Db, Sql) ->
    _pipe = sqlight:exec(Sql, Db),
    _pipe@1 = gleam@result:replace(_pipe, nil),
    gleam@result:map_error(
        _pipe@1,
        fun(Field@0) -> {database_error, Field@0} end
    ).

-spec 'query'(
    sqlight:connection(),
    binary(),
    list(sqlight:value()),
    fun((gleam@dynamic:dynamic_()) -> {ok, GBB} |
        {error, list(gleam@dynamic:decode_error())})
) -> {ok, list(GBB)} | {error, migrant@types:error()}.
'query'(Db, Sql, Args, Decoder) ->
    _pipe = sqlight:'query'(Sql, Db, Args, Decoder),
    gleam@result:map_error(_pipe, fun(Field@0) -> {database_error, Field@0} end).

-spec create_migrations_table(
    sqlight:connection(),
    fun(() -> {ok, nil} | {error, migrant@types:error()})
) -> {ok, nil} | {error, migrant@types:error()}.
create_migrations_table(Db, Next) ->
    gleam@io:println(<<"-> Creating migrations table"/utf8>>),
    Query = <<"
    CREATE TABLE IF NOT EXISTS __migrations (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      name TEXT NOT NULL,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP
    );
  "/utf8>>,
    case exec(Db, Query) of
        {ok, _} ->
            Next();

        {error, E} ->
            {error, E}
    end.

-spec pluralise_migration(integer()) -> binary().
pluralise_migration(Count) ->
    case Count of
        1 ->
            <<"migration"/utf8>>;

        _ ->
            <<"migrations"/utf8>>
    end.

-spec filter_applied_migrations(
    sqlight:connection(),
    gleam@dict:dict(binary(), migrant@types:migration()),
    fun((gleam@dict:dict(binary(), migrant@types:migration())) -> {ok, nil} |
        {error, migrant@types:error()})
) -> {ok, nil} | {error, migrant@types:error()}.
filter_applied_migrations(Db, Migrations, Next) ->
    gleam@io:println(<<"-> Filtering applied migrations"/utf8>>),
    Sql = <<"SELECT name FROM __migrations ORDER BY id, name ASC;"/utf8>>,
    case 'query'(
        Db,
        Sql,
        [],
        gleam@dynamic:element(0, fun gleam@dynamic:string/1)
    ) of
        {ok, Applied} ->
            _pipe = Migrations,
            _pipe@1 = gleam@dict:drop(_pipe, Applied),
            (fun(M) ->
                Count = gleam@dict:size(M),
                case Count of
                    0 ->
                        gleam@io:println(<<"-> No migrations to apply"/utf8>>),
                        {ok, nil};

                    _ ->
                        gleam@io:println(
                            <<<<<<<<"-> Found "/utf8,
                                            (gleam@int:to_string(
                                                gleam@dict:size(M)
                                            ))/binary>>/binary,
                                        " "/utf8>>/binary,
                                    (pluralise_migration(Count))/binary>>/binary,
                                " to apply"/utf8>>
                        ),
                        Next(M)
                end
            end)(_pipe@1);

        {error, E} ->
            gleam@io:debug(E),
            gleam@io:println(<<"-> Failed to filter applied migrations"/utf8>>),
            {error, E}
    end.

-spec rollback({binary(), migrant@types:migration()}, sqlight:connection()) -> {ok,
        nil} |
    {error, migrant@types:error()}.
rollback(Migration_tuple, Db) ->
    {Name, Migration} = Migration_tuple,
    case erlang:element(3, Migration) of
        {some, Sql} ->
            case exec(Db, Sql) of
                {ok, _} ->
                    {ok, nil};

                {error, E} ->
                    {error, E}
            end;

        none ->
            {error,
                {migration_error,
                    <<"Unable to rollback migration: "/utf8, Name/binary>>,
                    rollback_error}}
    end.

-spec mark_migration_as_applied(
    sqlight:connection(),
    {binary(), migrant@types:migration()}
) -> {ok, nil} | {error, migrant@types:error()}.
mark_migration_as_applied(Db, Migration_tuple) ->
    {Name, _} = Migration_tuple,
    Sql = <<"INSERT INTO __migrations (name) VALUES (?) returning id;"/utf8>>,
    case 'query'(
        Db,
        Sql,
        [sqlight:text(Name)],
        gleam@dynamic:element(0, fun gleam@dynamic:int/1)
    ) of
        {ok, _} ->
            {ok, nil};

        {error, E} ->
            {error, E}
    end.

-spec apply({binary(), migrant@types:migration()}, sqlight:connection()) -> {ok,
        nil} |
    {error, migrant@types:error()}.
apply(Migration_tuple, Db) ->
    {Name, Migration} = Migration_tuple,
    case erlang:element(2, Migration) of
        {some, Sql} ->
            gleam@io:println(<<"-> Applying migration: "/utf8, Name/binary>>),
            case exec(Db, Sql) of
                {ok, _} ->
                    case mark_migration_as_applied(Db, Migration_tuple) of
                        {ok, _} ->
                            {ok, nil};

                        {error, E} ->
                            gleam@io:println(
                                <<"-> Failed to mark migration as applied: "/utf8,
                                    Name/binary>>
                            ),
                            gleam@io:debug(E),
                            gleam@io:println(
                                <<"-> Rolling back migration: "/utf8,
                                    Name/binary>>
                            ),
                            case rollback(Migration_tuple, Db) of
                                {ok, _} ->
                                    {error,
                                        {migration_error,
                                            <<"Rollback complete, failed to mark migration as applied: "/utf8,
                                                Name/binary>>,
                                            E}};

                                {error, E@1} ->
                                    gleam@io:println(
                                        <<"-> Failed to rollback migration: "/utf8,
                                            Name/binary>>
                                    ),
                                    {error, E@1}
                            end
                    end,
                    {ok, nil};

                {error, E@2} ->
                    gleam@io:println(
                        <<"-> Failed to apply migration: "/utf8, Name/binary>>
                    ),
                    gleam@io:debug(E@2),
                    gleam@io:println(
                        <<"-> Rolling back migration: "/utf8, Name/binary>>
                    ),
                    case rollback(Migration_tuple, Db) of
                        {ok, _} ->
                            {error,
                                {migration_error,
                                    <<"Rollback complete, failed to apply migration: "/utf8,
                                        Name/binary>>,
                                    E@2}};

                        {error, E@3} ->
                            {error, E@3}
                    end
            end;

        none ->
            gleam@io:println(
                <<<<"-> Skipping migration: "/utf8, Name/binary>>/binary,
                    " no `up` query"/utf8>>
            ),
            {ok, nil}
    end.

-spec run_migration(
    list({binary(), migrant@types:migration()}),
    sqlight:connection(),
    integer()
) -> {ok, integer()} | {error, migrant@types:error()}.
run_migration(Migrations, Db, Count) ->
    case Migrations of
        [] ->
            {ok, Count};

        [Migration | Rest] ->
            case apply(Migration, Db) of
                {ok, _} ->
                    run_migration(Rest, Db, Count + 1);

                {error, E} ->
                    {error, E}
            end
    end.

-spec sort_migrations(gleam@dict:dict(binary(), migrant@types:migration())) -> list({binary(),
    migrant@types:migration()}).
sort_migrations(Migrations) ->
    _pipe = Migrations,
    _pipe@1 = gleam@dict:to_list(_pipe),
    gleam@list:sort(
        _pipe@1,
        fun(A, B) ->
            {Name_a, _} = A,
            {Name_b, _} = B,
            gleam@string:compare(Name_a, Name_b)
        end
    ).

-spec apply_migrations(
    sqlight:connection(),
    gleam@dict:dict(binary(), migrant@types:migration())
) -> {ok, nil} | {error, migrant@types:error()}.
apply_migrations(Db, Migrations) ->
    gleam@io:println(<<"-> Applying migrations"/utf8>>),
    Count = begin
        _pipe = Migrations,
        _pipe@1 = sort_migrations(_pipe),
        run_migration(_pipe@1, Db, 0)
    end,
    case Count of
        {ok, Count@1} ->
            gleam@io:println(
                <<<<"-> Applied "/utf8, (gleam@int:to_string(Count@1))/binary>>/binary,
                    " migrations"/utf8>>
            ),
            {ok, nil};

        {error, E} ->
            {error, E}
    end.