gpkm

-module(gpkm@sav@decrypt).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([decrypt_pkm/1]).

-file("src/gpkm/sav/decrypt.gleam", 7).
-spec tr_unencrypt_chunks(list(list(integer())), integer(), list(integer())) -> list(integer()).
tr_unencrypt_chunks(Bytes_chunks, Rand_value, Res) ->
    case Bytes_chunks of
        [] ->
            _pipe = Res,
            lists:reverse(_pipe);

        [Chunk | T] ->
            Next_rand = gpkm@sav@blocks:rand(Rand_value),
            Rand_i16 = gpkm@utils@bytes:take_upper_16_bits(Rand_value),
            Chunk_i16 = gpkm@utils@bytes:to_int(Chunk),
            Unencrypted_byte = erlang:'bxor'(Chunk_i16, Rand_i16),
            tr_unencrypt_chunks(T, Next_rand, [Unencrypted_byte | Res])
    end.

-file("src/gpkm/sav/decrypt.gleam", 25).
-spec unencrypt_chunks_as_bytes(list(list(integer())), list(integer())) -> list(integer()).
unencrypt_chunks_as_bytes(Bytes_chunks, Rand_seed) ->
    Initial_rand_value = begin
        _pipe = Rand_seed,
        _pipe@1 = gpkm@utils@bytes:to_int(_pipe),
        gpkm@sav@blocks:rand(_pipe@1)
    end,
    _pipe@2 = tr_unencrypt_chunks(Bytes_chunks, Initial_rand_value, []),
    gleam@list:flat_map(
        _pipe@2,
        fun(_capture) ->
            gpkm@utils@bytes:i16_to_i8_bytes(_capture, little_endian)
        end
    ).

-file("src/gpkm/sav/decrypt.gleam", 32).
-spec decrypt_pkm(bitstring()) -> list(integer()).
decrypt_pkm(Pkm_bits) ->
    Pkm_bytes = erlang:binary_to_list(Pkm_bits),
    Header = gpkm@pkm@ser_de:get_unencrypted_header(Pkm_bytes, little_endian),
    Decrypted_block_bytes = begin
        _pipe = Pkm_bytes,
        _pipe@1 = gpkm@utils@bytes:chunked_slice(
            _pipe,
            16#08,
            16#87,
            2,
            little_endian
        ),
        _pipe@2 = unencrypt_chunks_as_bytes(_pipe@1, erlang:element(4, Header)),
        gpkm@sav@blocks:shuffle_block_bytes(
            _pipe@2,
            erlang:element(2, Header),
            decrypt
        )
    end,
    Decrypted_non_block_bytes = begin
        _pipe@3 = Pkm_bytes,
        _pipe@4 = gpkm@utils@bytes:chunked_slice(
            _pipe@3,
            16#88,
            16#eb,
            2,
            little_endian
        ),
        unencrypt_chunks_as_bytes(_pipe@4, erlang:element(2, Header))
    end,
    Decrypted_pkm = begin
        _pipe@5 = Header,
        _pipe@6 = gpkm@pkm@ser_de:header_as_bytes(_pipe@5),
        _pipe@7 = lists:append(_pipe@6, Decrypted_block_bytes),
        lists:append(_pipe@7, Decrypted_non_block_bytes)
    end,
    Decrypted_pkm.