-module(ip_address_erl).
-author('happy <352626958@qq.com>').

-include_lib("kernel/include/inet.hrl").

-define(PRINT(MSG),io:format("~s:~w " ++ MSG ++ "~n",[?MODULE,?LINE])).
-define(PRINT(MSG,ARGS),io:format("~s:~w " ++ MSG ++ "~n",[?MODULE,?LINE] ++ ARGS)).

-define(IP_DB_DAT_FILE,"./priv/17monipdb.dat").

-export([find/1,find/2]).

-export([test/0,test/1]).

%% ------------- DAT struct --------------
%%
%% | 4 bytes 数据长度 DataOffset |
%% | 256 * 4 ip首位对应的数据偏移 |
%% | DataOffset * 8 (4 bytes Ip, 3 bypes offSet, 1 byte data len) |
%% | Data Address Info |
%%
%% ---------------------------------------

find(Ip) ->
    find(Ip,?IP_DB_DAT_FILE).

find(Ip,DbFile) ->
    
    {ok,#hostent{h_addr_list = [_Ip |_]}} =  inet:gethostbyname(Ip),
    Ip2 = inet:ntoa(_Ip),
    
    [FirstIpStr | _] = IdList = string:tokens(Ip2,"."),
    LongIp = ntohl(IdList),
    FirstIp = to_integer(FirstIpStr),


    {ok,FileBin} = file:read_file(DbFile),
    <<OffsetLen:32,DataBin/binary>> = FileBin,

    {_Bin1,Bin2} = erlang:split_binary(DataBin,FirstIp * 4),
    <<MinOffset:4/little-unsigned-integer-unit:8,MaxOffSet:4/little-unsigned-integer-unit:8,_/binary>> = Bin2,
    MaxOffSet2 =
        case FirstIpStr >= 255 of 
            true -> OffsetLen;
            false -> MaxOffSet * 8 + 1024 + 4
        end,
   
    %% 截取区间内的数据
    {Bin3,_Bin4} = erlang:split_binary(FileBin,MaxOffSet2),
    {_Bin5,Bin6} = erlang:split_binary(Bin3, 1024 + 4 + MinOffset * 8), 
    % ?PRINT("MinOffset:~w,MaxOffSet:~w,Diff:~w",[MinOffset,MaxOffSet,MaxOffSet - MinOffset]),
    case find_data_index(Bin6,LongIp) of
        {ok,DataOffset,DataLen} ->
            {_Bin7,Bin8} = erlang:split_binary(FileBin,OffsetLen + DataOffset - 1024),
            {Address,_} = erlang:split_binary(Bin8,DataLen),
            {ok,Address};
        false -> false
    end.

find_data_index(IpData,LongIp)  ->
    Len = size(IpData) div 8,
    Len2 = Len div 2, 
    case IpData of
        <<Bin1:Len2/binary-unit:8,IpInfo:8/binary-unit:8,Bin2>> ->
            <<A:8,B:8,C:8,D:8,_/binary>> = IpInfo,
            DataLongIp = ntohl([A,B,C,D]),
            case DataLongIp > LongIp of
                true ->
                    find_data_index(<<Bin1/binary,IpData/binary>>,LongIp);
                false ->
                    find_data_index(Bin2,LongIp)
            end;
        _ -> find_data_index2(IpData,LongIp)
    end.
find_data_index2(<<A:8,B:8,C:8,D:8,DataOffset:3/little-unsigned-unit:8,DataLen:8,Bin2/binary>>,LongIp) ->
    DataLongIp = ntohl([A,B,C,D]),
    case DataLongIp >= LongIp of
        true ->
            {ok,DataOffset,DataLen};
        false ->
            find_data_index2(Bin2,LongIp)
    end;
find_data_index2(_Bin,_LongIp) -> false.

ntohl([A,B,C,D]) ->
    (to_integer(A) bsl 24) + (to_integer(B) bsl 16) + (to_integer(C) bsl 8) + to_integer(D).


to_integer(Val) when is_integer(Val) -> Val;
to_integer(Val) when is_binary(Val) -> binary_to_integer(Val);
to_integer(Val) when is_list(Val) -> list_to_integer(Val).

test() ->
    test("115.29.161.118").
test(Ip) ->
    case find(Ip) of
        {ok,Bin} -> 
            ?PRINT("Ip:~s -> ~ts",[Ip,Bin]);
        false ->
            ?PRINT("Ip:~w N/A", [Ip])
    end.