-module(database).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).
-define(FILEPATH, "src\\database.gleam").
-export([create_table/2, transaction/2, insert/2, delete/2, find/2, drop_table/1, select/2, migrate/2, field/3]).
-export_type([storage/0, table_attributes/0, table_ref/1, transaction/1, table/1, file_error/0, select_option/1, migrate_options/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(
    " 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(EKR) :: any() | {gleam_phantom, EKR}.

-opaque transaction(EKS) :: {transaction,
        table_ref({binary(), EKS}),
        gleam@dynamic@decode:decoder(EKS)}.

-opaque table(EKT) :: {table,
        gleam@erlang@atom:atom_(),
        list(table_attributes()),
        gleam@erlang@charlist:charlist(),
        gleam@dynamic@decode:decoder(EKT)}.

-type file_error() :: unable_to_open | unable_to_close.

-type select_option(EKU) :: skip | {continue, EKU} | {done, EKU}.

-type migrate_options(EKV) :: {update, EKV} | keep | delete.

-file("src\\database.gleam", 116).
?DOC(
    " Creats a table.\n"
    "\n"
    " If no .dets file exists for the provided definition, 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 decoder = {\n"
    "     use name <- database.field(0, decode.string)\n"
    "     use animal <- database.field(1, my_animal_decoder)\n"
    "     decode.success(Pet(name:, animal:))\n"
    "   }\n"
    "   database.create_table(name: \"pets\", decode_with: decoder)\n"
    "   // -> Ok(Table(Pet))\n"
    " }\n"
    " ```\n"
).
-spec create_table(binary(), gleam@dynamic@decode:decoder(EMG)) -> {ok,
        table(EMG)} |
    {error, file_error()}.
create_table(Name, Decoder) ->
    Name_atom = erlang:binary_to_atom(Name),
    Path = unicode:characters_to_list(<<Name/binary, ".dets"/utf8>>),
    Att = [{file, Path}, {type, set}, {keypos, 1}],
    case dets:open_file(Name_atom, Att) of
        {ok, Tab} ->
            case dets:close(Tab) of
                {error, _} ->
                    {error, unable_to_close};

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

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

-file("src\\database.gleam", 155).
?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), pet_id: String) {\n"
    "   use ref <- database.transaction(table)\n"
    "   case database.find(ref, pet_id) {\n"
    "     Some(_) -> True\n"
    "     None -> False\n"
    "   }\n"
    " }\n"
    " ```\n"
).
-spec transaction(table(EML), fun((transaction(EML)) -> EMO)) -> {ok, EMO} |
    {error, file_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({transaction, Ref, erlang:element(5, Table)}),
            case dets:close(Ref) of
                {error, _} ->
                    {error, unable_to_close};

                _ ->
                    {ok, Resp}
            end
    end.

-file("src\\database.gleam", 187).
?DOC(
    " Inserts a value into a table and return their generated id.\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) -> String {\n"
    "   let pet = Pet(name, animal)\n"
    "   use ref <- database.transaction(table)\n"
    "   database.insert(ref, pet)  \n"
    " }\n"
    " ```\n"
).
-spec insert(transaction(EMR), EMR) -> {ok, binary()} | {error, any()}.
insert(Transac, Value) ->
    Id = begin
        _pipe = crypto:strong_rand_bytes(16),
        gleam@bit_array:base64_url_encode(_pipe, false)
    end,
    case dets:insert(erlang:element(2, Transac), {Id, Value}) of
        {error, Reason} ->
            {error, Reason};

        _ ->
            {ok, Id}
    end.

-file("src\\database.gleam", 206).
?DOC(
    " Deletes a value from a table.\n"
    "\n"
    " # Example\n"
    "\n"
    " ```gleam\n"
    " pub fn delete_pet(table: Table(Pet) pet_id: String) {\n"
    "   use ref <- database.transaction(table)\n"
    "   database.delete(ref, pet_id)\n"
    " }\n"
    " ```\n"
).
-spec delete(transaction(any()), binary()) -> {ok, nil} | {error, any()}.
delete(Transac, Id) ->
    case dets:delete(erlang:element(2, Transac), Id) of
        {error, Reason} ->
            {error, Reason};

        _ ->
            {ok, nil}
    end.

-file("src\\database.gleam", 228).
?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, known_pluto_id)\n"
    "   case resp {\n"
    "     None -> Error(PlutoNotFoundBlameTheAstronomers)\n"
    "     Some(pluto) -> Ok(play_with(pluto))\n"
    "   }\n"
    " }\n"
    " ```\n"
).
-spec find(transaction(EMX), binary()) -> gleam@option:option(EMX).
find(Transac, Id) ->
    case dets:lookup(erlang:element(2, Transac), Id) of
        [{_, Resp}] ->
            case gleam@dynamic@decode:run(Resp, erlang:element(3, Transac)) of
                {ok, Val} ->
                    {some, Val};

                _ ->
                    none
            end;

        _ ->
            none
    end.

-file("src\\database.gleam", 255).
?DOC(
    " Deletes the 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(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", 296).
?DOC(
    " Searches for somethig on the table.\n"
    "\n"
    " # Example\n"
    " \n"
    " ```gleam\n"
    " pub fn fetch_all_parrots(table: Table(Pet)) {\n"
    "   use ref <- database.transaction(table)\n"
    "   use value <- database.select(ref)\n"
    "   case value {\n"
    "     #(_id, Pet(_name, Parrot)) -> Continue(value)\n"
    "     _ -> Skip\n"
    "   }\n"
    " }\n"
    " ```\n"
    "\n"
    " # IMPORTANT\n"
    " **DETS tables are not sorted in any deterministic way, so\n"
    " never assume that the last value inserted will be the last\n"
    " one on the table.**\n"
).
-spec select(transaction(END), fun(({binary(), END}) -> select_option(ENF))) -> list(ENF).
select(Transac, Select_fn) ->
    Continue = erlang:binary_to_atom(<<"continue"/utf8>>),
    New_fn = fun(Tab_value) ->
        {Id, Dyn_value} = Tab_value,
        case gleam@dynamic@decode:run(Dyn_value, erlang:element(3, Transac)) of
            {ok, Value} ->
                case Select_fn({Id, Value}) of
                    skip ->
                        Continue;

                    Res ->
                        Res
                end;

            _ ->
                Continue
        end
    end,
    dets:traverse(erlang:element(2, Transac), New_fn).

-file("src\\database.gleam", 353).
?DOC(
    " Migrates the table to a new structure.\n"
    " When the type stored in the table changes, this function\n"
    " allows you to update the table to the new structure.\n"
    "\n"
    " # IMPORTANT\n"
    " **To avoid conflicts, this function will start its own\n"
    " transaction, so you should not use it inside another.**\n"
    "\n"
    " # Example\n"
    "\n"
    " ```gleam\n"
    " pub fn migrate_pets(table: Table(Pet)) {\n"
    "   use value <- database.migrate(table)\n"
    "   case decode.run(value, my_pet_decoder()) {\n"
    "     Ok(pet) -> Update(pet)\n"
    "     _ -> Delete\n"
    "   } \n"
    " }\n"
    " ```\n"
).
-spec migrate(
    table(ENI),
    fun((gleam@dynamic:dynamic_()) -> migrate_options(ENI))
) -> {ok, nil} | {error, file_error()}.
migrate(Table, Migration) ->
    transaction(
        Table,
        fun(Transac) ->
            Continue = erlang:binary_to_atom(<<"continue"/utf8>>),
            Func = fun(Tab_value) ->
                {Id, Dyn_value} = Tab_value,
                case Migration(Dyn_value) of
                    {update, New_value} ->
                        _ = dets:insert(
                            erlang:element(2, Transac),
                            {Id, New_value}
                        ),
                        Continue;

                    delete ->
                        _ = dets:delete(erlang:element(2, Transac), Id),
                        Continue;

                    keep ->
                        Continue
                end
            end,
            _ = dets:traverse(erlang:element(2, Transac), Func),
            nil
        end
    ).

-file("src\\database.gleam", 389).
?DOC(
    " Field decoder\n"
    " \n"
    " # Example\n"
    " \n"
    " ```gleam\n"
    " let decoder = {\n"
    "   use name <- database.field(0, decode.string)\n"
    "   use animal <- database.field(1, my_animal_decoder)\n"
    "   decode.success(Pet(name:, animal:))\n"
    " }\n"
    " ```\n"
).
-spec field(
    integer(),
    gleam@dynamic@decode:decoder(ENN),
    fun((ENN) -> gleam@dynamic@decode:decoder(ENP))
) -> gleam@dynamic@decode:decoder(ENP).
field(Field_index, Field_decoder, Next) ->
    gleam@dynamic@decode:field(Field_index + 1, Field_decoder, Next).