From 9bf65a415b17f635f2a86487920bc5a0ac8df580 Mon Sep 17 00:00:00 2001
From: zmstone <zmstone@gmail.com>
Date: Wed, 27 Mar 2024 17:34:18 +0100
Subject: [PATCH] feat(variform): add a variable transformer

---
 .gitignore                                    |  2 ++
 .../src/variform/emqx_variform_parser.yrl     | 16 ++++++++++++
 apps/emqx/src/variform/emqx_variform_scan.xrl | 26 +++++++++++++++++++
 3 files changed, 44 insertions(+)
 create mode 100644 apps/emqx/src/variform/emqx_variform_parser.yrl
 create mode 100644 apps/emqx/src/variform/emqx_variform_scan.xrl

diff --git a/.gitignore b/.gitignore
index 5e91d4bc5..a2c8b7e65 100644
--- a/.gitignore
+++ b/.gitignore
@@ -76,3 +76,5 @@ rebar-git-cache.tar
 .docker_image_tag
 .emqx_docker_image_tags
 .git/
+apps/emqx/src/emqx_variform_parser.erl
+apps/emqx/src/variform/emqx_variform_scan.erl
diff --git a/apps/emqx/src/variform/emqx_variform_parser.yrl b/apps/emqx/src/variform/emqx_variform_parser.yrl
new file mode 100644
index 000000000..3f2b739ba
--- /dev/null
+++ b/apps/emqx/src/variform/emqx_variform_parser.yrl
@@ -0,0 +1,16 @@
+Nonterminals expr call_or_var args.
+Terminals identifier number string '(' ')' ','.
+
+Rootsymbol expr.
+
+%% Grammar Rules
+expr -> call_or_var: '$1'.
+
+call_or_var -> identifier '(' args ')' : {call, element(3,'$1'), '$3'}.
+call_or_var -> identifier : {var, element(3, '$1')}.
+args -> expr : ['$1'].
+args -> args ',' expr : '$1' ++ ['$3'].
+
+%% Handling direct values and variables within arguments
+expr -> number : {num, element(3, '$1')}.
+expr -> string : {str, element(3, '$1')}.
diff --git a/apps/emqx/src/variform/emqx_variform_scan.xrl b/apps/emqx/src/variform/emqx_variform_scan.xrl
new file mode 100644
index 000000000..53657bad4
--- /dev/null
+++ b/apps/emqx/src/variform/emqx_variform_scan.xrl
@@ -0,0 +1,26 @@
+Definitions.
+%% Define regular expressions for tokens
+IDENTIFIER  = [a-zA-Z][a-zA-Z0-9_.]*
+SQ_STRING   = \'[^\']*\'
+DQ_STRING   = \"[^\"]*\"
+NUMBER      = [+-]?(\\d+\\.\\d+|[0-9]+)
+LPAREN      = \(
+RPAREN      = \)
+COMMA       = ,
+WHITESPACE  = [\s\t\n]+
+
+Rules.
+%% Match function names, variable names (with ${}), strings, numbers, and structural characters
+{WHITESPACE} : skip_token.
+{IDENTIFIER} : {token, {identifier, TokenLine, TokenChars}}.
+{SQ_STRING}  : {token, {string, TokenLine, unquote(TokenChars, $')}}.
+{DQ_STRING}  : {token, {string, TokenLine, unquote(TokenChars, $")}}.
+{NUMBER}     : {token, {number, TokenLine, TokenChars}}.
+{LPAREN}     : {token, {'(', TokenLine}}.
+{RPAREN}     : {token, {')', TokenLine}}.
+{COMMA}      : {token, {',', TokenLine}}.
+
+Erlang code.
+
+unquote(String, Char) ->
+    string:trim(String, both, [Char]).