-module(thrifty@container).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/thrifty/container.gleam").
-export([element_type_to_code/1, code_to_element_type/1, encode_list_header/2, decode_list_header/2, encode_map_header/3, decode_map_header/2]).
-export_type([element_type/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.

-type element_type() :: bool_type |
    i8_type |
    i16_type |
    i32_type |
    i64_type |
    double_type |
    binary_type |
    list_type |
    set_type |
    map_type |
    struct_type.

-file("src/thrifty/container.gleam", 83).
?DOC(
    " Convert ElementType to compact protocol type code (4 bits).\n"
    "\n"
    " Inputs\n"
    " - `t`: the `ElementType` to convert.\n"
    "\n"
    " Outputs\n"
    " - Returns the 4-bit integer code used in Compact Protocol headers.\n"
    "\n"
    " Complexity\n"
    " - O(1)\n"
).
-spec element_type_to_code(element_type()) -> integer().
element_type_to_code(T) ->
    case T of
        bool_type ->
            2;

        i8_type ->
            3;

        i16_type ->
            4;

        i32_type ->
            5;

        i64_type ->
            6;

        double_type ->
            7;

        binary_type ->
            8;

        list_type ->
            9;

        set_type ->
            10;

        map_type ->
            11;

        struct_type ->
            12
    end.

-file("src/thrifty/container.gleam", 112).
?DOC(
    " Convert a compact protocol 4-bit type code to `ElementType`.\n"
    "\n"
    " Inputs\n"
    " - `code`: integer value extracted from a header nibble (0-15).\n"
    "\n"
    " Outputs\n"
    " - `Ok(ElementType)` when the code is recognized.\n"
    " - `Error(types.UnsupportedType(code))` when the code is unknown.\n"
    "\n"
    " Error modes\n"
    " - Returns `types.UnsupportedType` for unknown codes.\n"
).
-spec code_to_element_type(integer()) -> {ok, element_type()} |
    {error, thrifty@types:decode_error()}.
code_to_element_type(Code) ->
    case Code of
        1 ->
            {ok, bool_type};

        2 ->
            {ok, bool_type};

        3 ->
            {ok, i8_type};

        4 ->
            {ok, i16_type};

        5 ->
            {ok, i32_type};

        6 ->
            {ok, i64_type};

        7 ->
            {ok, double_type};

        8 ->
            {ok, binary_type};

        9 ->
            {ok, list_type};

        10 ->
            {ok, set_type};

        11 ->
            {ok, map_type};

        12 ->
            {ok, struct_type};

        _ ->
            {error, {unsupported_type, Code}}
    end.

-file("src/thrifty/container.gleam", 143).
?DOC(
    " Encode a list/set header consisting of size and element type.\n"
    "\n"
    " Inputs\n"
    " - `size`: number of elements in the list/set (non-negative).\n"
    " - `elem_type`: the `ElementType` of elements.\n"
    "\n"
    " Outputs\n"
    " - Returns a `BitArray` containing either the short-form header (1 byte)\n"
    "   when `size < 15` or the long-form header (1 byte + varint) otherwise.\n"
    "\n"
    " Complexity\n"
    " - O(1) (plus cost of varint encoding when required).\n"
).
-spec encode_list_header(integer(), element_type()) -> bitstring().
encode_list_header(Size, Elem_type) ->
    Type_code = element_type_to_code(Elem_type),
    case Size < 15 of
        true ->
            Header_byte = (Size * 16) + Type_code,
            <<Header_byte:8/integer>>;

        false ->
            Header_byte@1 = (15 * 16) + Type_code,
            Size_varint = thrifty@varint:encode_varint(Size),
            <<Header_byte@1:8/integer, Size_varint/bitstring>>
    end.

-file("src/thrifty/container.gleam", 171).
?DOC(
    " Decode a list/set header from a `BitArray` at `byte_position`.\n"
    "\n"
    " Inputs\n"
    " - `data`: the `BitArray` containing the encoded header and payload.\n"
    " - `byte_position`: byte offset where the header begins.\n"
    "\n"
    " Outputs\n"
    " - `Ok(#(size, element_type, next_byte_position))` on success where\n"
    "   `next_byte_position` is the byte index immediately after the header.\n"
    " - `Error(types.DecodeError)` on malformed input or unexpected end.\n"
).
-spec decode_list_header(bitstring(), integer()) -> {ok,
        {integer(), element_type(), integer()}} |
    {error, thrifty@types:decode_error()}.
decode_list_header(Data, Byte_position) ->
    case gleam_stdlib:bit_array_slice(Data, Byte_position, 1) of
        {error, _} ->
            {error, unexpected_end_of_input};

        {ok, Header_bits} ->
            case Header_bits of
                <<Header_byte:8/integer>> ->
                    Size_nibble = Header_byte div 16,
                    Type_nibble = Header_byte rem 16,
                    case code_to_element_type(Type_nibble) of
                        {error, E} ->
                            {error, E};

                        {ok, Elem_type} ->
                            case Size_nibble =:= 15 of
                                true ->
                                    case thrifty@varint:decode_varint(
                                        Data,
                                        Byte_position + 1
                                    ) of
                                        {error, E@1} ->
                                            {error, E@1};

                                        {ok, {Size, Next_pos}} ->
                                            {ok, {Size, Elem_type, Next_pos}}
                                    end;

                                false ->
                                    {ok,
                                        {Size_nibble,
                                            Elem_type,
                                            Byte_position + 1}}
                            end
                    end;

                _ ->
                    {error,
                        {invalid_wire_format,
                            <<"Invalid list header byte"/utf8>>}}
            end
    end.

-file("src/thrifty/container.gleam", 219).
?DOC(
    " Encode a map header (size + key type + value type).\n"
    "\n"
    " Inputs\n"
    " - `size`: number of entries in the map (non-negative).\n"
    " - `key_type`: the `ElementType` used for keys.\n"
    " - `value_type`: the `ElementType` used for values.\n"
    "\n"
    " Outputs\n"
    " - For empty maps returns a single zero byte.\n"
    " - For non-empty maps returns varint(size) followed by a single types byte\n"
    "   where the high nibble is key type and the low nibble is value type.\n"
).
-spec encode_map_header(integer(), element_type(), element_type()) -> bitstring().
encode_map_header(Size, Key_type, Value_type) ->
    case Size =:= 0 of
        true ->
            <<0:8/integer>>;

        false ->
            Size_varint = thrifty@varint:encode_varint(Size),
            Key_code = element_type_to_code(Key_type),
            Value_code = element_type_to_code(Value_type),
            Types_byte = (Key_code * 16) + Value_code,
            <<Size_varint/bitstring, Types_byte:8/integer>>
    end.

-file("src/thrifty/container.gleam", 246).
?DOC(
    " Decode a map header from `data` at `byte_position`.\n"
    "\n"
    " Inputs\n"
    " - `data`: the `BitArray` containing the encoded header and payload.\n"
    " - `byte_position`: byte offset where the header begins.\n"
    "\n"
    " Outputs\n"
    " - `Ok(#(size, key_type, value_type, next_byte_position))` where `next_byte_position`\n"
    "   points after the types byte (or after the varint for empty maps).\n"
    " - `Error(types.DecodeError)` on malformed input or unexpected end.\n"
).
-spec decode_map_header(bitstring(), integer()) -> {ok,
        {integer(), element_type(), element_type(), integer()}} |
    {error, thrifty@types:decode_error()}.
decode_map_header(Data, Byte_position) ->
    case thrifty@varint:decode_varint(Data, Byte_position) of
        {error, E} ->
            {error, E};

        {ok, {Size, Next_pos}} ->
            case Size =:= 0 of
                true ->
                    {ok, {0, i32_type, i32_type, Next_pos}};

                false ->
                    case gleam_stdlib:bit_array_slice(Data, Next_pos, 1) of
                        {error, _} ->
                            {error, unexpected_end_of_input};

                        {ok, Types_bits} ->
                            case Types_bits of
                                <<Types_byte:8/integer>> ->
                                    Key_code = Types_byte div 16,
                                    Value_code = Types_byte rem 16,
                                    case code_to_element_type(Key_code) of
                                        {error, E@1} ->
                                            {error, E@1};

                                        {ok, Key_type} ->
                                            case code_to_element_type(
                                                Value_code
                                            ) of
                                                {error, E@2} ->
                                                    {error, E@2};

                                                {ok, Value_type} ->
                                                    {ok,
                                                        {Size,
                                                            Key_type,
                                                            Value_type,
                                                            Next_pos + 1}}
                                            end
                                    end;

                                _ ->
                                    {error,
                                        {invalid_wire_format,
                                            <<"Invalid map types byte"/utf8>>}}
                            end
                    end
            end
    end.