fix(s3-csv): clarify naming of CSV container concepts

Co-Authored-By: Ilya Averyanov <av@rubybox.dev>

apps/emqx_bridge_s3/src/emqx_bridge_s3_aggreg_csv.erl

@@ -16,14 +16,22 @@
 
 -record(csv, {
     columns :: [binary()] | undefined,
-    order :: [binary()],
-    separator :: char() | iodata(),
-    delimiter :: char() | iodata(),
+    column_order :: [binary()],
+    %% A string or character that separates each field in a record from the next.
+    %% Default: ","
+    field_separator :: char() | iodata(),
+    %% A string or character that delimits boundaries of a record.
+    %% Default: "\n"
+    record_delimiter :: char() | iodata(),
     quoting_mp :: _ReMP
 }).
 
 -type container() :: #csv{}.
--type options() :: #{column_order => [column()]}.
+
+-type options() :: #{
+    %% Which columns have to be ordered first in the resulting CSV?
+    column_order => [column()]
+}.
 
 -type record() :: emqx_bridge_s3_aggregator:record().
 -type column() :: binary().
@@ -34,9 +42,9 @@
 new(Opts) ->
     {ok, MP} = re:compile("[\\[\\],\\r\\n\"]", [unicode]),
     #csv{
-        order = maps:get(column_order, Opts, []),
-        separator = $,,
-        delimiter = $\n,
+        column_order = maps:get(column_order, Opts, []),
+        field_separator = $,,
+        record_delimiter = $\n,
         quoting_mp = MP
     }.
 
@@ -56,28 +64,28 @@ close(#csv{}) ->
 
 %%
 
-mk_columns(Record, #csv{order = ColumnOrder}) ->
+mk_columns(Record, #csv{column_order = ColumnOrder}) ->
     Columns = [emqx_utils_conv:bin(C) || C <- lists:sort(maps:keys(Record))],
     Unoredered = Columns -- ColumnOrder,
     ColumnOrder ++ Unoredered.
 
 -spec emit_header([column()], container()) -> iodata().
-emit_header([C], #csv{delimiter = Delim}) ->
+emit_header([C], #csv{record_delimiter = Delim}) ->
     [C, Delim];
-emit_header([C | Rest], CSV = #csv{separator = Sep}) ->
+emit_header([C | Rest], CSV = #csv{field_separator = Sep}) ->
     [C, Sep | emit_header(Rest, CSV)];
-emit_header([], #csv{delimiter = Delim}) ->
+emit_header([], #csv{record_delimiter = Delim}) ->
     [Delim].
 
 -spec emit_row(record(), container()) -> iodata().
 emit_row(Record, CSV = #csv{columns = Columns}) ->
     emit_row(Record, Columns, CSV).
 
-emit_row(Record, [C], CSV = #csv{delimiter = Delim}) ->
+emit_row(Record, [C], CSV = #csv{record_delimiter = Delim}) ->
     [emit_cell(C, Record, CSV), Delim];
-emit_row(Record, [C | Rest], CSV = #csv{separator = Sep}) ->
+emit_row(Record, [C | Rest], CSV = #csv{field_separator = Sep}) ->
     [emit_cell(C, Record, CSV), Sep | emit_row(Record, Rest, CSV)];
-emit_row(#{}, [], #csv{delimiter = Delim}) ->
+emit_row(#{}, [], #csv{record_delimiter = Delim}) ->
     [Delim].
 
 emit_cell(Column, Record, CSV) ->