gleeth

-module(gleeth@ethereum@address).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/gleeth/ethereum/address.gleam").
-export([to_lowercase/1, checksum/1, is_valid_checksum/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(
    " EIP-55 checksummed Ethereum addresses.\n"
    "\n"
    " Ethereum addresses are 20-byte hex strings. EIP-55 defines a mixed-case\n"
    " encoding that serves as a checksum: each hex character is uppercased if\n"
    " the corresponding nibble of the keccak256 hash of the lowercase address\n"
    " is >= 8.\n"
    "\n"
    " ## Examples\n"
    "\n"
    " ```gleam\n"
    " address.checksum(\"0xd8da6bf26964af9d7eed9e03e53415d37aa96045\")\n"
    " // -> Ok(\"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045\")\n"
    " ```\n"
).

-file("src/gleeth/ethereum/address.gleam", 55).
?DOC(" Convert a potentially checksummed address to lowercase with 0x prefix.\n").
-spec to_lowercase(binary()) -> {ok, binary()} | {error, binary()}.
to_lowercase(Address) ->
    Cleaned = case gleam_stdlib:string_starts_with(Address, <<"0x"/utf8>>) of
        true ->
            gleam@string:drop_start(Address, 2);

        false ->
            Address
    end,
    case string:length(Cleaned) of
        40 ->
            {ok, <<"0x"/utf8, (string:lowercase(Cleaned))/binary>>};

        _ ->
            {error, <<"Address must be 40 hex characters"/utf8>>}
    end.

-file("src/gleeth/ethereum/address.gleam", 85).
-spec is_letter(binary()) -> boolean().
is_letter(Char) ->
    case Char of
        <<"a"/utf8>> ->
            true;

        <<"b"/utf8>> ->
            true;

        <<"c"/utf8>> ->
            true;

        <<"d"/utf8>> ->
            true;

        <<"e"/utf8>> ->
            true;

        <<"f"/utf8>> ->
            true;

        _ ->
            false
    end.

-file("src/gleeth/ethereum/address.gleam", 92).
-spec nibble_value(binary()) -> integer().
nibble_value(Char) ->
    case Char of
        <<"0"/utf8>> ->
            0;

        <<"1"/utf8>> ->
            1;

        <<"2"/utf8>> ->
            2;

        <<"3"/utf8>> ->
            3;

        <<"4"/utf8>> ->
            4;

        <<"5"/utf8>> ->
            5;

        <<"6"/utf8>> ->
            6;

        <<"7"/utf8>> ->
            7;

        <<"8"/utf8>> ->
            8;

        <<"9"/utf8>> ->
            9;

        <<"a"/utf8>> ->
            10;

        <<"b"/utf8>> ->
            11;

        <<"c"/utf8>> ->
            12;

        <<"d"/utf8>> ->
            13;

        <<"e"/utf8>> ->
            14;

        <<"f"/utf8>> ->
            15;

        _ ->
            0
    end.

-file("src/gleeth/ethereum/address.gleam", 66).
-spec apply_checksum(binary()) -> binary().
apply_checksum(Lower_hex) ->
    Hash = gleeth@crypto@keccak:keccak256_binary(
        gleam_stdlib:identity(Lower_hex)
    ),
    Hash_hex = string:lowercase(gleam_stdlib:base16_encode(Hash)),
    Addr_chars = gleam@string:to_graphemes(Lower_hex),
    Hash_chars = gleam@string:to_graphemes(Hash_hex),
    _pipe = gleam@list:map2(
        Addr_chars,
        Hash_chars,
        fun(Addr_char, Hash_char) -> case is_letter(Addr_char) of
                false ->
                    Addr_char;

                true ->
                    case nibble_value(Hash_char) >= 8 of
                        true ->
                            string:uppercase(Addr_char);

                        false ->
                            Addr_char
                    end
            end end
    ),
    erlang:list_to_binary(_pipe).

-file("src/gleeth/ethereum/address.gleam", 21).
?DOC(" Produce the EIP-55 checksummed form of an Ethereum address.\n").
-spec checksum(binary()) -> {ok, binary()} | {error, binary()}.
checksum(Address) ->
    Cleaned = case gleam_stdlib:string_starts_with(Address, <<"0x"/utf8>>) of
        true ->
            gleam@string:drop_start(Address, 2);

        false ->
            Address
    end,
    case string:length(Cleaned) of
        40 ->
            {ok,
                <<"0x"/utf8,
                    (apply_checksum(string:lowercase(Cleaned)))/binary>>};

        _ ->
            {error, <<"Address must be 40 hex characters"/utf8>>}
    end.

-file("src/gleeth/ethereum/address.gleam", 35).
?DOC(
    " Check whether a mixed-case address has a valid EIP-55 checksum.\n"
    " All-lowercase and all-uppercase addresses are considered valid\n"
    " (no checksum applied).\n"
).
-spec is_valid_checksum(binary()) -> boolean().
is_valid_checksum(Address) ->
    Cleaned = case gleam_stdlib:string_starts_with(Address, <<"0x"/utf8>>) of
        true ->
            gleam@string:drop_start(Address, 2);

        false ->
            Address
    end,
    case string:length(Cleaned) of
        40 ->
            Lower = string:lowercase(Cleaned),
            Upper = string:uppercase(Cleaned),
            case (Cleaned =:= Lower) orelse (Cleaned =:= Upper) of
                true ->
                    true;

                false ->
                    apply_checksum(Lower) =:= Cleaned
            end;

        _ ->
            false
    end.