%%
%% %CopyrightBegin%
%% 
%% Copyright Ericsson AB 1997-2021. All Rights Reserved.
%% 
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%% 
%% %CopyrightEnd%
%%
-module(win32reg).

-export([open/1, close/1,
	 current_key/1, change_key/2, change_key_create/2,
	 sub_keys/1, delete_key/1,
	 value/2, values/1, set_value/3, delete_value/2,
	 expand/1,
	 format_error/1]).

-export_type([reg_handle/0]).

%% Key handles (always open).
-define(hkey_classes_root, 16#80000000).
-define(hkey_current_user, 16#80000001).
-define(hkey_local_machine, 16#80000002).
-define(hkey_users, 16#80000003).
-define(hkey_performance_data, 16#80000004).
-define(hkey_current_config, 16#80000005).
-define(hkey_dyn_data, 16#80000006).

%% Driver commands.
-define(cmd_get_current, 0).
-define(cmd_open_key, 1).
-define(cmd_create_key, 2).
-define(cmd_get_all_subkeys, 3).
-define(cmd_get_value, 4).
-define(cmd_get_all_values, 5).
-define(cmd_set_value, 6).
-define(cmd_delete_key, 7).
-define(cmd_delete_value, 8).

%% Data types.
-define(reg_sc, 1).
-define(reg_expand_sc, 2).
-define(reg_binary, 3).
-define(reg_dword, 4).

%% Basic types internal to this file.
-opaque reg_handle() :: {'win32reg',port()}.
-type name()       :: string() | 'default'.
-type value()      :: string() | integer() | binary().

%%% Exported functions.

-spec open(OpenModeList) -> ReturnValue when
      OpenModeList :: [OpenMode],
      OpenMode :: 'read' | 'write',
      ReturnValue :: {'ok', RegHandle} | {'error', ErrorId :: 'enotsup'},
      RegHandle :: reg_handle().

open(Modes) ->
    case os:type() of
	{win32, _} ->
	    case open_mode(Modes, []) of
		{error, Reason} ->
		    {error, Reason};
		ModeStr ->
		    P = open_port({spawn, "registry__drv__ " ++ ModeStr}, []),
		    {ok, {win32reg, P}}
	    end;
	_ ->
	    {error, enotsup}
    end.

-spec close(RegHandle) -> 'ok' when
      RegHandle :: reg_handle().

close({win32reg, Reg}) when is_port(Reg) ->
    unlink(Reg),
    exit(Reg, die),
    ok.

-spec current_key(RegHandle) -> ReturnValue when
      RegHandle :: reg_handle(),
      ReturnValue :: {'ok', string()}.

current_key({win32reg, Reg}) when is_port(Reg) ->
    Cmd = [?cmd_get_current],
    Reg ! {self(), {command, Cmd}},
    {state, Hkey, Name} = get_result(Reg),
    Root = hkey_to_string(Hkey),
    {ok, case Name of
	     [] -> Root;
	     _  -> Root ++ [$\\|Name]
	 end}.

-spec change_key(RegHandle, Key) -> ReturnValue when
      RegHandle :: reg_handle(),
      Key :: string(),
      ReturnValue :: 'ok' | {'error', ErrorId :: atom()}.

change_key({win32reg, Reg}, Key) when is_port(Reg) ->
    change_key(Reg, ?cmd_open_key, Key).

-spec change_key_create(RegHandle, Key) -> ReturnValue when
      RegHandle :: reg_handle(),
      Key :: string(),
      ReturnValue :: 'ok' | {'error', ErrorId :: atom()}.

change_key_create({win32reg, Reg}, Key) when is_port(Reg) ->
    change_key(Reg, ?cmd_create_key, Key).

change_key(Reg, Cmd, Key) ->
    case parse_key(Key, Reg) of
	{ok, Hkey, Path} ->
	    Reg ! {self(), {command, [Cmd, i32(Hkey), Path, 0]}},
	    get_result(Reg);
	{error, Reason} ->
	    {error, Reason}
    end.

-spec sub_keys(RegHandle) -> ReturnValue when
      RegHandle :: reg_handle(),
      ReturnValue :: {'ok', [SubKey]} | {'error', ErrorId :: atom()},
      SubKey :: string().

sub_keys({win32reg, Reg}) when is_port(Reg) ->
    Cmd = [?cmd_get_all_subkeys],
    Reg ! {self(), {command, Cmd}},
    collect_keys(Reg, []).

-spec delete_key(RegHandle) -> ReturnValue when
      RegHandle :: reg_handle(),
      ReturnValue :: 'ok' | {'error', ErrorId :: atom()}.

delete_key({win32reg, Reg}) when is_port(Reg) ->
    Cmd = [?cmd_get_current],
    Reg ! {self(), {command, Cmd}},
    case get_result(Reg) of
	{state, _Hkey, []} ->
	    {error, eperm};
	{state, _Hkey, Rest} ->
	    [Name|_] = split_key(Rest),
	    ok = change_key(Reg, ?cmd_open_key, ".."),
	    Cmd2 = [?cmd_delete_key],
	    Reg ! {self(), {command, [Cmd2, Name, 0]}},
	    get_result(Reg);
	{error, Erorr} ->
	    {error, Erorr}
    end.

-spec set_value(RegHandle, Name, Value) -> ReturnValue when
      RegHandle :: reg_handle(),
      Name :: name(),
      Value :: value(),
      ReturnValue :: 'ok' | {'error', ErrorId :: atom()}.

set_value({win32reg, Reg}, Name0, Value) when is_port(Reg) ->
    Name =
	case Name0 of
	    default -> [];
	    _ -> Name0
	end,
    {Type, V} = term_to_value(Value),
    Cmd = [?cmd_set_value, Type, Name, 0, V],
    Reg ! {self(), {command, Cmd}},
    get_result(Reg).

-spec value(RegHandle, Name) -> ReturnValue when
      RegHandle :: reg_handle(),
      Name :: name(),
      ReturnValue :: {'ok', Value :: value()} | {'error', ErrorId :: atom()}.

value({win32reg, Reg}, Name0) when is_port(Reg) ->
    Name =
	case Name0 of
	    default -> [];
	    _ -> Name0
	end,
    Cmd = [?cmd_get_value, Name, 0],
    Reg ! {self(), {command, Cmd}},
    case get_result(Reg) of
	{value, {default, Value}} when Name =:= [] ->
	    {ok, Value};
	{value, {Name, Value}} ->
	    {ok, Value};
	{error, Reason} ->
	    {error, Reason}
    end.
    
-spec values(RegHandle) -> ReturnValue when
      RegHandle :: reg_handle(),
      ReturnValue :: {'ok', [ValuePair]} | {'error', ErrorId :: atom()},
      ValuePair :: {Name :: name(), Value :: value()}.

values({win32reg, Reg}) when is_port(Reg) ->
    Cmd = [?cmd_get_all_values],
    Reg ! {self(), {command, Cmd}},
    collect_values(Reg, []).

-spec delete_value(RegHandle, Name) -> ReturnValue when
      RegHandle :: reg_handle(),
      Name :: name(),
      ReturnValue :: 'ok' | {'error', ErrorId :: atom()}.

delete_value({win32reg, Reg}, Name0) when is_port(Reg) ->
    Name =
	case Name0 of
	    default -> [];
	    _ -> Name0
	end,
    Cmd = [?cmd_delete_value, Name, 0],
    Reg ! {self(), {command, Cmd}},
    get_result(Reg).

-spec expand(String) -> ExpandedString when
      String :: string(),
      ExpandedString :: string().

expand(Value) ->
    expand(Value, [], []).

expand([$%, $%|Rest], [], Result) ->
    expand(Rest, [], [$%|Result]);
expand([$%, C|Rest], [], Result) ->
    expand(Rest, [C], Result);
expand([C|Rest], [], Result) ->
    expand(Rest, [], [C|Result]);
expand([$%|Rest], Env0, Result) ->
    Env = lists:reverse(Env0),
    expand(Rest, [], lists:reverse(os:getenv(Env, ""))++Result);
expand([C|Rest], Env, Result) ->
    expand(Rest, [C|Env], Result);
expand([], [], Result) ->
    lists:reverse(Result).

-spec format_error(ErrorId) -> ErrorString when
      ErrorId :: atom(),
      ErrorString :: string().

format_error(ErrorId) ->
    erl_posix_msg:message(ErrorId).

%%% Implementation.

-spec collect_values(port(), [{name(), value()}]) -> 
        {'ok', [{name(), value()}]} | {'error', ErrorId :: atom()}.

collect_values(P, Result) ->
    case get_result(P) of
	ok ->
	    {ok, lists:reverse(Result)};
	{value, ValueData} ->
	    collect_values(P, [ValueData|Result]);
	{error, Reason} ->
	    {error, Reason}
    end.

-spec collect_keys(port(), string()) -> {'ok', [string()]} | {'error', ErrorId :: atom()}.

collect_keys(P, Result) ->
    case get_result(P) of
	ok ->
	    {ok, lists:reverse(Result)};
	{key, KeyData} ->
	    collect_keys(P, [KeyData|Result]);
	{error, Reason} ->
	    {error, Reason}
    end.
    
get_result(P) ->
    receive
	{P, {data, Data}} ->
	    get_result1(Data)
    end.

get_result1([$e|Reason]) ->
    {error, list_to_atom(Reason)};
get_result1([$o]) ->
    ok;
get_result1([$k|Name]) ->
    {key, Name};
get_result1([$v|Rest0]) ->
    {ok, Type, Rest1} = i32_on_head(Rest0),
    {ok, Name0, Value} = get_cstring(Rest1),
    Name = 
	case Name0 of
	    [] -> default;
	    _ ->  Name0
	end,
    {value, {Name, encode_value(Type, Value)}};
get_result1([$s|Rest0]) ->
    {ok, Hkey, Name} = i32_on_head(Rest0),
    {state, Hkey, Name}.

encode_value(?reg_sc, Value) ->
    Value;
encode_value(?reg_expand_sc, Value) ->
    Value;
encode_value(?reg_dword, Value) ->
    i32(Value);
encode_value(_, Value) ->
    list_to_binary(Value).

term_to_value(Int) when is_integer(Int) ->
    {i32(?reg_dword), i32(Int)};
term_to_value(String) when is_list(String) ->
    {i32(?reg_sc), [String, 0]};
term_to_value(Bin) when is_binary(Bin) ->
    {i32(?reg_binary), Bin};
term_to_value(_) ->
    exit(badarg).
    
get_cstring(List) ->
    get_cstring(List, []).

get_cstring([0|Rest], Result) ->
    {ok, lists:reverse(Result), Rest};
get_cstring([C|Rest], Result) ->
    get_cstring(Rest, [C|Result]);
get_cstring([], Result) ->
    {ok, lists:reverse(Result), []}.
	    
i32(Int) when is_integer(Int) ->
    [(Int bsr 24) band 255,
     (Int bsr 16) band 255,
     (Int bsr  8) band 255,
     Int band 255];
i32([X1, X2, X3, X4]) ->
    (X1 bsl 24) bor (X2 bsl 16) bor (X3 bsl 8) bor X4.

i32_on_head([X1, X2, X3, X4 | Rest]) ->
    {ok, (X1 bsl 24) bor (X2 bsl 16) bor (X3 bsl 8) bor X4, Rest}.

parse_key([$\\|Rest], _) ->
    parse_root(Rest, []);
parse_key(Key, Reg) ->
    parse_relative(Key, Reg).

parse_relative(Path, Reg) ->
    Cmd = [?cmd_get_current],
    Reg ! {self(), {command, Cmd}},
    {state, RootHandle, Name} = get_result(Reg),
    Original = split_key(Name),
    Relative = lists:reverse(split_key(Path)),
    case parse_relative1(Relative, Original) of
	{error,Error} ->
	    {error,Error};
	NewPath ->
	    {ok, RootHandle, NewPath}
    end.

parse_relative1([".."|_], []) ->
    {error,enoent};
parse_relative1([".."|T1], [_|T2]) ->
    parse_relative1(T1, T2);
parse_relative1([Comp|Rest], Result) ->
    parse_relative1(Rest, [Comp|Result]);
parse_relative1([], Result) ->
    reverse_and_join(Result, []).

reverse_and_join([X|Rest], []) ->
    reverse_and_join(Rest, [X]);
reverse_and_join([X|Rest], Result) ->
    reverse_and_join(Rest, [X, "\\" | Result]);
reverse_and_join([], Result) ->
    Result.

split_key(Key) ->
    split_key(Key, [], []).

split_key([$\\|Rest], Current, Result) ->
    split_key(Rest, [], [lists:reverse(Current)|Result]);
split_key([C|Rest], Current, Result) ->
    split_key(Rest, [C|Current], Result);
split_key([], [], Result) ->
    Result;
split_key([], Current, Result) ->
    [lists:reverse(Current)|Result].

parse_root([$\\|Rest], Result) ->
    Root = 
	case lists:reverse(Result) of
	    [$h, $k, $e, $y, $_|Root0] ->
		Root0;
	    Root0 ->
		Root0
	end,
    case root_to_handle(list_to_atom(Root)) of
	false ->
	    {error, enoent};
	Handle ->
	    {ok, Handle, Rest}
    end;
parse_root([C|Rest], Result) ->
    parse_root(Rest, [C|Result]);
parse_root([], Result) ->
    parse_root([$\\], Result).

root_to_handle(classes_root) -> ?hkey_classes_root;
root_to_handle(hkcr) -> ?hkey_classes_root;
root_to_handle(current_user) -> ?hkey_current_user;
root_to_handle(hkcu) -> ?hkey_current_user;
root_to_handle(local_machine) -> ?hkey_local_machine;
root_to_handle(hklm) -> ?hkey_local_machine;
root_to_handle(users) -> ?hkey_users;
root_to_handle(hku) -> ?hkey_users;
root_to_handle(current_config) -> ?hkey_current_config;
root_to_handle(hkcc) -> ?hkey_current_config;
root_to_handle(dyn_data) -> ?hkey_dyn_data;
root_to_handle(hkdd) -> ?hkey_dyn_data;
root_to_handle(performance_data) -> ?hkey_performance_data;
root_to_handle(_) -> false.

hkey_to_string(?hkey_classes_root) -> "\\hkey_classes_root";
hkey_to_string(?hkey_current_user) -> "\\hkey_current_user";
hkey_to_string(?hkey_local_machine) -> "\\hkey_local_machine";
hkey_to_string(?hkey_users) -> "\\hkey_users";
hkey_to_string(?hkey_performance_data) -> "\\hkey_performance_data";
hkey_to_string(?hkey_current_config) -> "\\hkey_current_config";
hkey_to_string(?hkey_dyn_data) -> "\\hkey_dyn_data".

open_mode([read|Rest], Result) ->
    open_mode(Rest, [$r|Result]);
open_mode([write|Rest], Result) ->
    open_mode(Rest, [$w|Result]);
open_mode([], Result) ->
    Result;
open_mode(_, _) ->
    {error, einval}.