From ad95473aaef0148d350996f2a2bfccc1b812f90f Mon Sep 17 00:00:00 2001
From: zmstone <zmstone@gmail.com>
Date: Thu, 28 Mar 2024 13:59:31 +0100
Subject: [PATCH] refactor: move string functions to emqx_variform

---
 apps/emqx/src/variform/emqx_variform.erl      |  39 ++
 apps/emqx/src/variform/emqx_variform_str.erl  | 353 ++++++++++++++++++
 apps/emqx_rule_engine/src/emqx_rule_funcs.erl | 271 +++-----------
 3 files changed, 434 insertions(+), 229 deletions(-)
 create mode 100644 apps/emqx/src/variform/emqx_variform.erl
 create mode 100644 apps/emqx/src/variform/emqx_variform_str.erl

diff --git a/apps/emqx/src/variform/emqx_variform.erl b/apps/emqx/src/variform/emqx_variform.erl
new file mode 100644
index 000000000..6f4fd6f47
--- /dev/null
+++ b/apps/emqx/src/variform/emqx_variform.erl
@@ -0,0 +1,39 @@
+%%--------------------------------------------------------------------
+%% Copyright (c) 2020-2024 EMQ Technologies Co., Ltd. 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.
+%%--------------------------------------------------------------------
+
+%% Predefined functions for templating
+-module(emqx_variform).
+
+-export([render/2]).
+
+render(Expression, Context) ->
+    case emqx_variform_scan:string(Expression) of
+        {ok, Tokens, _Line} ->
+            case emqx_variform_parser:parse(Tokens) of
+                {ok, Expr} ->
+                    eval(Expr, Context);
+                {error, {_, emqx_variform_parser, Msg}} ->
+                    %% syntax error
+                    {error, lists:flatten(Msg)};
+                {error, Reason} ->
+                    {error, Reason}
+            end;
+        {error, Reason, _Line} ->
+            {error, Reason}
+    end.
+
+eval(Expr, _Context) ->
+    io:format(user, "~p~n", [Expr]).
diff --git a/apps/emqx/src/variform/emqx_variform_str.erl b/apps/emqx/src/variform/emqx_variform_str.erl
new file mode 100644
index 000000000..d94519f76
--- /dev/null
+++ b/apps/emqx/src/variform/emqx_variform_str.erl
@@ -0,0 +1,353 @@
+%%--------------------------------------------------------------------
+%% Copyright (c) 2020-2024 EMQ Technologies Co., Ltd. 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.
+%%--------------------------------------------------------------------
+
+%% Predefined functions string templating
+-module(emqx_variform_str).
+
+%% String Funcs
+-export([
+    coalesce/1,
+    coalesce/2,
+    lower/1,
+    ltrim/1,
+    ltrim/2,
+    reverse/1,
+    rtrim/1,
+    rtrim/2,
+    strlen/1,
+    substr/2,
+    substr/3,
+    trim/1,
+    trim/2,
+    upper/1,
+    split/2,
+    split/3,
+    concat/1,
+    concat/2,
+    tokens/2,
+    tokens/3,
+    sprintf_s/2,
+    pad/2,
+    pad/3,
+    pad/4,
+    replace/3,
+    replace/4,
+    regex_match/2,
+    regex_replace/3,
+    ascii/1,
+    find/2,
+    find/3,
+    join_to_string/1,
+    join_to_string/2,
+    unescape/1
+]).
+
+-define(IS_EMPTY(X), (X =:= <<>> orelse X =:= "" orelse X =:= undefined)).
+
+%%------------------------------------------------------------------------------
+%% String Funcs
+%%------------------------------------------------------------------------------
+
+%% @doc Return the first non-empty string
+coalesce(A, B) when ?IS_EMPTY(A) andalso ?IS_EMPTY(B) ->
+    <<>>;
+coalesce(A, _) when is_binary(A) ->
+    A;
+coalesce(_, B) ->
+    B.
+
+%% @doc Return the first non-empty string
+coalesce([]) ->
+    <<>>;
+coalesce([H | T]) ->
+    coalesce(H, coalesce(T)).
+
+lower(S) when is_binary(S) ->
+    string:lowercase(S).
+
+ltrim(S) when is_binary(S) ->
+    string:trim(S, leading).
+
+ltrim(S, Chars) ->
+    string:trim(S, leading, Chars).
+
+reverse(S) when is_binary(S) ->
+    iolist_to_binary(string:reverse(S)).
+
+rtrim(S) when is_binary(S) ->
+    string:trim(S, trailing).
+
+rtrim(S, Chars) when is_binary(S) ->
+    string:trim(S, trailing, Chars).
+
+strlen(S) when is_binary(S) ->
+    string:length(S).
+
+substr(S, Start) when is_binary(S), is_integer(Start) ->
+    string:slice(S, Start).
+
+substr(S, Start, Length) when
+    is_binary(S),
+    is_integer(Start),
+    is_integer(Length)
+->
+    string:slice(S, Start, Length).
+
+trim(S) when is_binary(S) ->
+    string:trim(S).
+
+trim(S, Chars) when is_binary(S) ->
+    string:trim(S, both, Chars).
+
+upper(S) when is_binary(S) ->
+    string:uppercase(S).
+
+split(S, P) when is_binary(S), is_binary(P) ->
+    [R || R <- string:split(S, P, all), R =/= <<>> andalso R =/= ""].
+
+split(S, P, <<"notrim">>) ->
+    string:split(S, P, all);
+split(S, P, <<"leading_notrim">>) ->
+    string:split(S, P, leading);
+split(S, P, <<"leading">>) when is_binary(S), is_binary(P) ->
+    [R || R <- string:split(S, P, leading), R =/= <<>> andalso R =/= ""];
+split(S, P, <<"trailing_notrim">>) ->
+    string:split(S, P, trailing);
+split(S, P, <<"trailing">>) when is_binary(S), is_binary(P) ->
+    [R || R <- string:split(S, P, trailing), R =/= <<>> andalso R =/= ""].
+
+tokens(S, Separators) ->
+    [list_to_binary(R) || R <- string:lexemes(binary_to_list(S), binary_to_list(Separators))].
+
+tokens(S, Separators, <<"nocrlf">>) ->
+    [
+        list_to_binary(R)
+     || R <- string:lexemes(binary_to_list(S), binary_to_list(Separators) ++ [$\r, $\n, [$\r, $\n]])
+    ].
+
+%% implicit convert args to strings, and then do concatenation
+concat(S1, S2) ->
+    concat([S1, S2], unicode).
+
+concat(List) ->
+    unicode:characters_to_binary(lists:map(fun str/1, List), unicode).
+
+sprintf_s(Format, Args) when is_list(Args) ->
+    erlang:iolist_to_binary(io_lib:format(binary_to_list(Format), Args)).
+
+pad(S, Len) when is_binary(S), is_integer(Len) ->
+    iolist_to_binary(string:pad(S, Len, trailing)).
+
+pad(S, Len, <<"trailing">>) when is_binary(S), is_integer(Len) ->
+    iolist_to_binary(string:pad(S, Len, trailing));
+pad(S, Len, <<"both">>) when is_binary(S), is_integer(Len) ->
+    iolist_to_binary(string:pad(S, Len, both));
+pad(S, Len, <<"leading">>) when is_binary(S), is_integer(Len) ->
+    iolist_to_binary(string:pad(S, Len, leading)).
+
+pad(S, Len, <<"trailing">>, Char) when is_binary(S), is_integer(Len), is_binary(Char) ->
+    Chars = unicode:characters_to_list(Char, utf8),
+    iolist_to_binary(string:pad(S, Len, trailing, Chars));
+pad(S, Len, <<"both">>, Char) when is_binary(S), is_integer(Len), is_binary(Char) ->
+    Chars = unicode:characters_to_list(Char, utf8),
+    iolist_to_binary(string:pad(S, Len, both, Chars));
+pad(S, Len, <<"leading">>, Char) when is_binary(S), is_integer(Len), is_binary(Char) ->
+    Chars = unicode:characters_to_list(Char, utf8),
+    iolist_to_binary(string:pad(S, Len, leading, Chars)).
+
+replace(SrcStr, P, RepStr) when is_binary(SrcStr), is_binary(P), is_binary(RepStr) ->
+    iolist_to_binary(string:replace(SrcStr, P, RepStr, all)).
+
+replace(SrcStr, P, RepStr, <<"all">>) when is_binary(SrcStr), is_binary(P), is_binary(RepStr) ->
+    iolist_to_binary(string:replace(SrcStr, P, RepStr, all));
+replace(SrcStr, P, RepStr, <<"trailing">>) when
+    is_binary(SrcStr), is_binary(P), is_binary(RepStr)
+->
+    iolist_to_binary(string:replace(SrcStr, P, RepStr, trailing));
+replace(SrcStr, P, RepStr, <<"leading">>) when is_binary(SrcStr), is_binary(P), is_binary(RepStr) ->
+    iolist_to_binary(string:replace(SrcStr, P, RepStr, leading)).
+
+regex_match(Str, RE) ->
+    case re:run(Str, RE, [global, {capture, none}]) of
+        match -> true;
+        nomatch -> false
+    end.
+
+regex_replace(SrcStr, RE, RepStr) ->
+    re:replace(SrcStr, RE, RepStr, [global, {return, binary}]).
+
+ascii(Char) when is_binary(Char) ->
+    [FirstC | _] = binary_to_list(Char),
+    FirstC.
+
+find(S, P) when is_binary(S), is_binary(P) ->
+    find_s(S, P, leading).
+
+find(S, P, <<"trailing">>) when is_binary(S), is_binary(P) ->
+    find_s(S, P, trailing);
+find(S, P, <<"leading">>) when is_binary(S), is_binary(P) ->
+    find_s(S, P, leading).
+
+find_s(S, P, Dir) ->
+    case string:find(S, P, Dir) of
+        nomatch -> <<"">>;
+        SubStr -> SubStr
+    end.
+
+join_to_string(List) when is_list(List) ->
+    join_to_string(<<", ">>, List).
+
+join_to_string(Sep, List) when is_list(List), is_binary(Sep) ->
+    iolist_to_binary(lists:join(Sep, [str(Item) || Item <- List])).
+
+unescape(Bin) when is_binary(Bin) ->
+    UnicodeList = unicode:characters_to_list(Bin, utf8),
+    UnescapedUnicodeList = unescape_string(UnicodeList),
+    UnescapedUTF8Bin = unicode:characters_to_binary(UnescapedUnicodeList, utf32, utf8),
+    case UnescapedUTF8Bin of
+        Out when is_binary(Out) ->
+            Out;
+        Error ->
+            throw({invalid_unicode_character, Error})
+    end.
+
+unescape_string(Input) -> unescape_string(Input, []).
+
+unescape_string([], Acc) ->
+    lists:reverse(Acc);
+unescape_string([$\\, $\\ | Rest], Acc) ->
+    unescape_string(Rest, [$\\ | Acc]);
+unescape_string([$\\, $n | Rest], Acc) ->
+    unescape_string(Rest, [$\n | Acc]);
+unescape_string([$\\, $t | Rest], Acc) ->
+    unescape_string(Rest, [$\t | Acc]);
+unescape_string([$\\, $r | Rest], Acc) ->
+    unescape_string(Rest, [$\r | Acc]);
+unescape_string([$\\, $b | Rest], Acc) ->
+    unescape_string(Rest, [$\b | Acc]);
+unescape_string([$\\, $f | Rest], Acc) ->
+    unescape_string(Rest, [$\f | Acc]);
+unescape_string([$\\, $v | Rest], Acc) ->
+    unescape_string(Rest, [$\v | Acc]);
+unescape_string([$\\, $' | Rest], Acc) ->
+    unescape_string(Rest, [$\' | Acc]);
+unescape_string([$\\, $" | Rest], Acc) ->
+    unescape_string(Rest, [$\" | Acc]);
+unescape_string([$\\, $? | Rest], Acc) ->
+    unescape_string(Rest, [$\? | Acc]);
+unescape_string([$\\, $a | Rest], Acc) ->
+    unescape_string(Rest, [$\a | Acc]);
+%% Start of HEX escape code
+unescape_string([$\\, $x | [$0 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$1 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$2 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$3 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$4 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$5 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$6 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$7 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$8 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$9 | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$A | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$B | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$C | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$D | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$E | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$F | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$a | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$b | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$c | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$d | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$e | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+unescape_string([$\\, $x | [$f | _] = HexStringStart], Acc) ->
+    unescape_handle_hex_string(HexStringStart, Acc);
+%% We treat all other escape sequences as not valid input to leave room for
+%% extending the function to support more escape codes
+unescape_string([$\\, X | _Rest], _Acc) ->
+    erlang:throw({unrecognized_escape_sequence, list_to_binary([$\\, X])});
+unescape_string([First | Rest], Acc) ->
+    unescape_string(Rest, [First | Acc]).
+
+unescape_handle_hex_string(HexStringStart, Acc) ->
+    {RemainingString, Num} = parse_hex_string(HexStringStart),
+    unescape_string(RemainingString, [Num | Acc]).
+
+parse_hex_string(SeqStartingWithHexDigit) ->
+    parse_hex_string(SeqStartingWithHexDigit, []).
+
+parse_hex_string([], Acc) ->
+    ReversedAcc = lists:reverse(Acc),
+    {[], list_to_integer(ReversedAcc, 16)};
+parse_hex_string([First | Rest] = String, Acc) ->
+    case is_hex_digit(First) of
+        true ->
+            parse_hex_string(Rest, [First | Acc]);
+        false ->
+            ReversedAcc = lists:reverse(Acc),
+            {String, list_to_integer(ReversedAcc, 16)}
+    end.
+
+is_hex_digit($0) -> true;
+is_hex_digit($1) -> true;
+is_hex_digit($2) -> true;
+is_hex_digit($3) -> true;
+is_hex_digit($4) -> true;
+is_hex_digit($5) -> true;
+is_hex_digit($6) -> true;
+is_hex_digit($7) -> true;
+is_hex_digit($8) -> true;
+is_hex_digit($9) -> true;
+is_hex_digit($A) -> true;
+is_hex_digit($B) -> true;
+is_hex_digit($C) -> true;
+is_hex_digit($D) -> true;
+is_hex_digit($E) -> true;
+is_hex_digit($F) -> true;
+is_hex_digit($a) -> true;
+is_hex_digit($b) -> true;
+is_hex_digit($c) -> true;
+is_hex_digit($d) -> true;
+is_hex_digit($e) -> true;
+is_hex_digit($f) -> true;
+is_hex_digit(_) -> false.
+
+%%------------------------------------------------------------------------------
+%% Data Type Conversion Funcs
+%%------------------------------------------------------------------------------
+
+str(Data) ->
+    emqx_utils_conv:bin(Data).
diff --git a/apps/emqx_rule_engine/src/emqx_rule_funcs.erl b/apps/emqx_rule_engine/src/emqx_rule_funcs.erl
index ac7f66597..ea8e192d4 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_funcs.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_funcs.erl
@@ -132,6 +132,8 @@
 
 %% String Funcs
 -export([
+    coalesce/1,
+    coalesce/2,
     lower/1,
     ltrim/1,
     reverse/1,
@@ -768,130 +770,67 @@ is_array(_) -> false.
 %% String Funcs
 %%------------------------------------------------------------------------------
 
-lower(S) when is_binary(S) ->
-    string:lowercase(S).
+coalesce(List) -> emqx_variform_str:coalesce(List).
 
-ltrim(S) when is_binary(S) ->
-    string:trim(S, leading).
+coalesce(A, B) -> emqx_variform_str:coalesce(A, B).
 
-reverse(S) when is_binary(S) ->
-    iolist_to_binary(string:reverse(S)).
+lower(S) -> emqx_variform_str:lower(S).
 
-rtrim(S) when is_binary(S) ->
-    string:trim(S, trailing).
+ltrim(S) -> emqx_variform_str:ltrim(S).
 
-strlen(S) when is_binary(S) ->
-    string:length(S).
+reverse(S) -> emqx_variform_str:reverse(S).
 
-substr(S, Start) when is_binary(S), is_integer(Start) ->
-    string:slice(S, Start).
+rtrim(S) -> emqx_variform_str:rtrim(S).
 
-substr(S, Start, Length) when
-    is_binary(S),
-    is_integer(Start),
-    is_integer(Length)
-->
-    string:slice(S, Start, Length).
+strlen(S) -> emqx_variform_str:strlen(S).
 
-trim(S) when is_binary(S) ->
-    string:trim(S).
+substr(S, Start) -> emqx_variform_str:substr(S, Start).
 
-upper(S) when is_binary(S) ->
-    string:uppercase(S).
+substr(S, Start, Length) -> emqx_variform_str:substr(S, Start, Length).
 
-split(S, P) when is_binary(S), is_binary(P) ->
-    [R || R <- string:split(S, P, all), R =/= <<>> andalso R =/= ""].
+trim(S) -> emqx_variform_str:trim(S).
 
-split(S, P, <<"notrim">>) ->
-    string:split(S, P, all);
-split(S, P, <<"leading_notrim">>) ->
-    string:split(S, P, leading);
-split(S, P, <<"leading">>) when is_binary(S), is_binary(P) ->
-    [R || R <- string:split(S, P, leading), R =/= <<>> andalso R =/= ""];
-split(S, P, <<"trailing_notrim">>) ->
-    string:split(S, P, trailing);
-split(S, P, <<"trailing">>) when is_binary(S), is_binary(P) ->
-    [R || R <- string:split(S, P, trailing), R =/= <<>> andalso R =/= ""].
+upper(S) -> emqx_variform_str:upper(S).
 
-tokens(S, Separators) ->
-    [list_to_binary(R) || R <- string:lexemes(binary_to_list(S), binary_to_list(Separators))].
+split(S, P) -> emqx_variform_str:split(S, P).
 
-tokens(S, Separators, <<"nocrlf">>) ->
-    [
-        list_to_binary(R)
-     || R <- string:lexemes(binary_to_list(S), binary_to_list(Separators) ++ [$\r, $\n, [$\r, $\n]])
-    ].
+split(S, P, Position) -> emqx_variform_str:split(S, P, Position).
 
-%% implicit convert args to strings, and then do concatenation
-concat(S1, S2) ->
-    unicode:characters_to_binary([str(S1), str(S2)], unicode).
+tokens(S, Separators) -> emqx_variform_str:tokens(S, Separators).
 
-sprintf_s(Format, Args) when is_list(Args) ->
-    erlang:iolist_to_binary(io_lib:format(binary_to_list(Format), Args)).
+tokens(S, Separators, NoCRLF) -> emqx_variform_str:tokens(S, Separators, NoCRLF).
 
-pad(S, Len) when is_binary(S), is_integer(Len) ->
-    iolist_to_binary(string:pad(S, Len, trailing)).
+concat(S1, S2) -> emqx_variform_str:concat(S1, S2).
 
-pad(S, Len, <<"trailing">>) when is_binary(S), is_integer(Len) ->
-    iolist_to_binary(string:pad(S, Len, trailing));
-pad(S, Len, <<"both">>) when is_binary(S), is_integer(Len) ->
-    iolist_to_binary(string:pad(S, Len, both));
-pad(S, Len, <<"leading">>) when is_binary(S), is_integer(Len) ->
-    iolist_to_binary(string:pad(S, Len, leading)).
+concat(List) -> emqx_variform_str:concat(List).
 
-pad(S, Len, <<"trailing">>, Char) when is_binary(S), is_integer(Len), is_binary(Char) ->
-    Chars = unicode:characters_to_list(Char, utf8),
-    iolist_to_binary(string:pad(S, Len, trailing, Chars));
-pad(S, Len, <<"both">>, Char) when is_binary(S), is_integer(Len), is_binary(Char) ->
-    Chars = unicode:characters_to_list(Char, utf8),
-    iolist_to_binary(string:pad(S, Len, both, Chars));
-pad(S, Len, <<"leading">>, Char) when is_binary(S), is_integer(Len), is_binary(Char) ->
-    Chars = unicode:characters_to_list(Char, utf8),
-    iolist_to_binary(string:pad(S, Len, leading, Chars)).
+sprintf_s(Format, Args) -> emqx_variform_str:sprintf_s(Format, Args).
 
-replace(SrcStr, P, RepStr) when is_binary(SrcStr), is_binary(P), is_binary(RepStr) ->
-    iolist_to_binary(string:replace(SrcStr, P, RepStr, all)).
+pad(S, Len) -> emqx_variform_str:pad(S, Len).
 
-replace(SrcStr, P, RepStr, <<"all">>) when is_binary(SrcStr), is_binary(P), is_binary(RepStr) ->
-    iolist_to_binary(string:replace(SrcStr, P, RepStr, all));
-replace(SrcStr, P, RepStr, <<"trailing">>) when
-    is_binary(SrcStr), is_binary(P), is_binary(RepStr)
-->
-    iolist_to_binary(string:replace(SrcStr, P, RepStr, trailing));
-replace(SrcStr, P, RepStr, <<"leading">>) when is_binary(SrcStr), is_binary(P), is_binary(RepStr) ->
-    iolist_to_binary(string:replace(SrcStr, P, RepStr, leading)).
+pad(S, Len, Position) -> emqx_variform_str:pad(S, Len, Position).
 
-regex_match(Str, RE) ->
-    case re:run(Str, RE, [global, {capture, none}]) of
-        match -> true;
-        nomatch -> false
-    end.
+pad(S, Len, Position, Char) -> emqx_variform_str:pad(S, Len, Position, Char).
 
-regex_replace(SrcStr, RE, RepStr) ->
-    re:replace(SrcStr, RE, RepStr, [global, {return, binary}]).
+replace(SrcStr, Pattern, RepStr) -> emqx_variform_str:replace(SrcStr, Pattern, RepStr).
 
-ascii(Char) when is_binary(Char) ->
-    [FirstC | _] = binary_to_list(Char),
-    FirstC.
+replace(SrcStr, Pattern, RepStr, Position) ->
+    emqx_variform_str:replace(SrcStr, Pattern, RepStr, Position).
 
-find(S, P) when is_binary(S), is_binary(P) ->
-    find_s(S, P, leading).
+regex_match(Str, RE) -> emqx_variform_str:regex_match(Str, RE).
 
-find(S, P, <<"trailing">>) when is_binary(S), is_binary(P) ->
-    find_s(S, P, trailing);
-find(S, P, <<"leading">>) when is_binary(S), is_binary(P) ->
-    find_s(S, P, leading).
+regex_replace(SrcStr, RE, RepStr) -> emqx_variform_str:regex_replace(SrcStr, RE, RepStr).
 
-find_s(S, P, Dir) ->
-    case string:find(S, P, Dir) of
-        nomatch -> <<"">>;
-        SubStr -> SubStr
-    end.
+ascii(Char) -> emqx_variform_str:ascii(Char).
+
+find(S, P) -> emqx_variform_str:find(S, P).
+
+find(S, P, Position) -> emqx_variform_str:find(S, P, Position).
+
+join_to_string(Str) -> emqx_variform_str:join_to_string(Str).
+
+join_to_string(Sep, List) -> emqx_variform_str:join_to_string(Sep, List).
 
-join_to_string(List) when is_list(List) ->
-    join_to_string(<<", ">>, List).
-join_to_string(Sep, List) when is_list(List), is_binary(Sep) ->
-    iolist_to_binary(lists:join(Sep, [str(Item) || Item <- List])).
 join_to_sql_values_string(List) ->
     QuotedList =
         [
@@ -938,137 +877,7 @@ jq(FilterProgram, JSONBin) ->
         ])
     ).
 
-unescape(Bin) when is_binary(Bin) ->
-    UnicodeList = unicode:characters_to_list(Bin, utf8),
-    UnescapedUnicodeList = unescape_string(UnicodeList),
-    UnescapedUTF8Bin = unicode:characters_to_binary(UnescapedUnicodeList, utf32, utf8),
-    case UnescapedUTF8Bin of
-        Out when is_binary(Out) ->
-            Out;
-        Error ->
-            throw({invalid_unicode_character, Error})
-    end.
-
-unescape_string(Input) -> unescape_string(Input, []).
-
-unescape_string([], Acc) ->
-    lists:reverse(Acc);
-unescape_string([$\\, $\\ | Rest], Acc) ->
-    unescape_string(Rest, [$\\ | Acc]);
-unescape_string([$\\, $n | Rest], Acc) ->
-    unescape_string(Rest, [$\n | Acc]);
-unescape_string([$\\, $t | Rest], Acc) ->
-    unescape_string(Rest, [$\t | Acc]);
-unescape_string([$\\, $r | Rest], Acc) ->
-    unescape_string(Rest, [$\r | Acc]);
-unescape_string([$\\, $b | Rest], Acc) ->
-    unescape_string(Rest, [$\b | Acc]);
-unescape_string([$\\, $f | Rest], Acc) ->
-    unescape_string(Rest, [$\f | Acc]);
-unescape_string([$\\, $v | Rest], Acc) ->
-    unescape_string(Rest, [$\v | Acc]);
-unescape_string([$\\, $' | Rest], Acc) ->
-    unescape_string(Rest, [$\' | Acc]);
-unescape_string([$\\, $" | Rest], Acc) ->
-    unescape_string(Rest, [$\" | Acc]);
-unescape_string([$\\, $? | Rest], Acc) ->
-    unescape_string(Rest, [$\? | Acc]);
-unescape_string([$\\, $a | Rest], Acc) ->
-    unescape_string(Rest, [$\a | Acc]);
-%% Start of HEX escape code
-unescape_string([$\\, $x | [$0 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$1 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$2 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$3 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$4 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$5 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$6 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$7 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$8 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$9 | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$A | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$B | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$C | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$D | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$E | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$F | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$a | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$b | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$c | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$d | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$e | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-unescape_string([$\\, $x | [$f | _] = HexStringStart], Acc) ->
-    unescape_handle_hex_string(HexStringStart, Acc);
-%% We treat all other escape sequences as not valid input to leave room for
-%% extending the function to support more escape codes
-unescape_string([$\\, X | _Rest], _Acc) ->
-    erlang:throw({unrecognized_escape_sequence, list_to_binary([$\\, X])});
-unescape_string([First | Rest], Acc) ->
-    unescape_string(Rest, [First | Acc]).
-
-unescape_handle_hex_string(HexStringStart, Acc) ->
-    {RemainingString, Num} = parse_hex_string(HexStringStart),
-    unescape_string(RemainingString, [Num | Acc]).
-
-parse_hex_string(SeqStartingWithHexDigit) ->
-    parse_hex_string(SeqStartingWithHexDigit, []).
-
-parse_hex_string([], Acc) ->
-    ReversedAcc = lists:reverse(Acc),
-    {[], list_to_integer(ReversedAcc, 16)};
-parse_hex_string([First | Rest] = String, Acc) ->
-    case is_hex_digit(First) of
-        true ->
-            parse_hex_string(Rest, [First | Acc]);
-        false ->
-            ReversedAcc = lists:reverse(Acc),
-            {String, list_to_integer(ReversedAcc, 16)}
-    end.
-
-is_hex_digit($0) -> true;
-is_hex_digit($1) -> true;
-is_hex_digit($2) -> true;
-is_hex_digit($3) -> true;
-is_hex_digit($4) -> true;
-is_hex_digit($5) -> true;
-is_hex_digit($6) -> true;
-is_hex_digit($7) -> true;
-is_hex_digit($8) -> true;
-is_hex_digit($9) -> true;
-is_hex_digit($A) -> true;
-is_hex_digit($B) -> true;
-is_hex_digit($C) -> true;
-is_hex_digit($D) -> true;
-is_hex_digit($E) -> true;
-is_hex_digit($F) -> true;
-is_hex_digit($a) -> true;
-is_hex_digit($b) -> true;
-is_hex_digit($c) -> true;
-is_hex_digit($d) -> true;
-is_hex_digit($e) -> true;
-is_hex_digit($f) -> true;
-is_hex_digit(_) -> false.
+unescape(Str) -> emqx_variform_str:unescape(Str).
 
 %%------------------------------------------------------------------------------
 %% Array Funcs
@@ -1095,6 +904,10 @@ last(List) when is_list(List) ->
 contains(Elm, List) when is_list(List) ->
     lists:member(Elm, List).
 
+%%------------------------------------------------------------------------------
+%% Map Funcs
+%%------------------------------------------------------------------------------
+
 map_new() ->
     #{}.