database

-module(database).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).
-define(FILEPATH, "src\\database.gleam").
-export([transaction/2, insert/2, delete/2, find/2, drop_table/1, create_table/2]).
-export_type([storage/0, table_attributes/0, table_ref/1, table/1, table_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(
    " An outrageously simple set of functions to interact with the BEAM\n"
    " DETS (Disk-based Erlang Term Storage) API.\n"
    " \n"
    " Good for small projects and POCs.\n"
    "\n"
    "\n"
    " This project DOES NOT intend to serve as direct bindings to the \n"
    " DETS API, but rather to interact with it in a gleamy way:\n"
    "   1. with a simple and concise interface;\n"
    "   2. type-safely;\n"
    "   3. no unexpected crashes, all errors are values.\n"
).

-type storage() :: set.

-type table_attributes() :: {file, gleam@erlang@charlist:charlist()} |
    {type, storage()} |
    {keypos, integer()}.

-type table_ref(EIC) :: any() | {gleam_phantom, EIC}.

-opaque table(EID) :: {table,
        gleam@erlang@atom:atom_(),
        list(table_attributes()),
        gleam@erlang@charlist:charlist()} |
    {gleam_phantom, EID}.

-type table_error() :: badarg | unable_to_open | unable_to_close.

-file("src\\database.gleam", 156).
?DOC(
    " Allows you to interact with the table.\n"
    "\n"
    " It opens and locks the .dets file, then execute your operations.\n"
    " Once the operations are done, it writes the changes into the file,\n"
    " closes and releases it.\n"
    "\n"
    " # Example\n"
    "\n"
    " ```gleam\n"
    " pub fn is_pet_registered(table: Table(Pet), petname: String) {\n"
    "   use ref <- database.transaction(table)\n"
    "   case database.find(ref, petname) {\n"
    "     Ok(_) -> True\n"
    "     Error(Nil) -> False\n"
    "   }\n"
    " }\n"
    " ```\n"
).
-spec transaction(table(EJO), fun((table_ref(EJO)) -> EJR)) -> {ok, EJR} |
    {error, table_error()}.
transaction(Table, Procedure) ->
    case dets:open_file(erlang:element(2, Table), erlang:element(3, Table)) of
        {error, _} ->
            {error, unable_to_open};

        {ok, Ref} ->
            Resp = Procedure(Ref),
            case dets:close(Ref) of
                {error, _} ->
                    {error, unable_to_close};

                _ ->
                    {ok, Resp}
            end
    end.

-file("src\\database.gleam", 193).
?DOC(
    " Inserts a value into a table.\n"
    "\n"
    " DETS tables do not have support for update, only for upsert.\n"
    " So if you have to change a value, just insert a new value\n"
    " with the same index, and it will replace the previous value.\n"
    "\n"
    " # Example\n"
    "\n"
    " ```gleam\n"
    " pub fn new_pet(table: Table(Pet), animal: Animal, name: String) {\n"
    "   let pet = Pet(name, animal)\n"
    "   let op = database.transaction(table, fn(ref) {\n"
    "     database.insert(ref, pet)\n"
    "   })\n"
    "   case op {\n"
    "     Ok(_) -> Ok(pet)\n"
    "     Error(reason) -> Error(reason)\n"
    "   }\n"
    " }\n"
    " ```\n"
).
-spec insert(table_ref(EJU), EJU) -> {ok, nil} | {error, any()}.
insert(Transac, Value) ->
    case dets:insert(Transac, Value) of
        {error, Reason} ->
            {error, Reason};

        _ ->
            {ok, nil}
    end.

-file("src\\database.gleam", 211).
?DOC(
    " Deletes a value from a table.\n"
    "\n"
    " # Example\n"
    "\n"
    " ```gleam\n"
    " pub fn delete_pet(table: Table(Pet) petname: String) {\n"
    "   use ref <- database.transaction(table)\n"
    "   database.delete(ref, petname)\n"
    " }\n"
    " ```\n"
).
-spec delete(table_ref(any()), any()) -> {ok, nil} | {error, any()}.
delete(Transac, Index) ->
    case dets:delete(Transac, Index) of
        {error, Reason} ->
            {error, Reason};

        _ ->
            {ok, nil}
    end.

-file("src\\database.gleam", 233).
?DOC(
    " Finds a value by its index\n"
    "\n"
    " # Example\n"
    "\n"
    " ```gleam\n"
    " pub fn play_with_pluto(table: Table(Pet)) {\n"
    "   use ref <- database.transaction(table)\n"
    "   let resp = database.find(ref, \"Pluto\")\n"
    "   case resp {\n"
    "     Error(_) -> Error(PlutoNotFoundBlameTheAstronomers)\n"
    "     Ok(pluto) -> Ok(play_with(pluto))\n"
    "   }\n"
    " }\n"
    " ```\n"
).
-spec find(table_ref(EKB), any()) -> {ok, EKB} | {error, nil}.
find(Transac, Index) ->
    case dets:lookup(Transac, Index) of
        [Resp] ->
            {ok, Resp};

        _ ->
            {error, nil}
    end.

-file("src\\database.gleam", 256).
?DOC(
    " Deletes de entire table file\n"
    "\n"
    " # Example\n"
    "\n"
    " ```gleam\n"
    " pub fn destroy_all_pets(table: Table(Pet), password: String) {\n"
    "   case password {\n"
    "     \"Yes, I am evil.\" -> {\n"
    "       database.drop(table)\n"
    "       Ok(Nil)\n"
    "     }\n"
    "     _ -> Error(WrongPassword)\n"
    "   }\n"
    " }\n"
    " ```\n"
).
-spec drop_table(table(any())) -> {ok, nil} | {error, any()}.
drop_table(Table) ->
    case file:delete(erlang:element(4, Table)) of
        {error, Reason} ->
            {error, Reason};

        _ ->
            {ok, nil}
    end.

-file("src\\database.gleam", 263).
-spec is_record(any()) -> boolean().
is_record(Value) ->
    erlang:is_tuple(Value) andalso erlang:is_atom(erlang:element(1, Value)).

-file("src\\database.gleam", 107).
?DOC(
    " Creats a table.\n"
    "\n"
    " If no .dets file exists for the provided sample, creates one.\n"
    " Otherwise, just checks whether the file is accessible and not\n"
    " corrupted.\n"
    "\n"
    " # Example\n"
    "\n"
    " ```gleam\n"
    " pub fn start_database() {\n"
    "   let pluto = Pet(name: \"Pluto\", animal: Dog)\n"
    "   database.create_table(sample: pluto, index_at: 0)\n"
    "   // -> Ok(Table(Pet))\n"
    " }\n"
    " ```\n"
).
-spec create_table(EJK, integer()) -> {ok, table(EJK)} | {error, table_error()}.
create_table(Sample, Keypos) ->
    case {is_record(Sample), Keypos >= 0} of
        {true, true} ->
            case (Keypos + 2) > erlang:tuple_size(Sample) of
                true ->
                    {error, badarg};

                false ->
                    At = erlang:element(1, Sample),
                    Name = erlang:atom_to_binary(At),
                    Path = unicode:characters_to_list(
                        <<Name/binary, ".dets"/utf8>>
                    ),
                    Att = [{file, Path}, {type, set}, {keypos, Keypos + 2}],
                    case dets:open_file(At, Att) of
                        {ok, Tab} ->
                            case dets:close(Tab) of
                                {error, _} ->
                                    {error, unable_to_close};

                                _ ->
                                    {ok, {table, At, Att, Path}}
                            end;

                        {error, _} ->
                            {error, unable_to_open}
                    end
            end;

        {_, _} ->
            {error, badarg}
    end.