add curly braces support to mqtt integration, documentation

contrib/etc/ebusd/mqtt-integration.cfg

@@ -6,6 +6,7 @@
 # where only the value is allowed to contain references to other variables.
 # A reference to a variable is escaped by a leading "%" character in front of the variable name consisting of only
 # alphabetic characters or the underscore. A double percent character "%%" is replaced by a single "%" in the value.
+# Curly braces may be used to separate a variable explicitly from the rest, e.g. as "%{version}" instead of "%version".
 # Every variable without an underscore in the name is automatically made available as well with an uppercase name and a
 # normalized value composed of only alphanumeric characters or underscore (i.e. suitable for being part of a topic).
 # When using "?=" instead of only the equal sign in a variable definition, the variable value is set to empty when one
@@ -93,12 +94,10 @@ filter-direction = r|u
 #filter-field =
 
 
-
 # the field type mapped from variables named "type_map-%direction-%type" or "type_map-%type" as fallback with the
 # field type and the optional direction in the suffix. The variable including the direction is evaluated first and
 # if it is missing or the result is empty, the variable excluding the direction is used instead.
 # This is also an implicit field type filter as missing or empty mappings are not published at all.
-
 type_map-number = number
 type_map-list = string
 type_map-string = string
@@ -107,6 +106,30 @@ type_map-time = string
 type_map-datetime = string
 
 
+# field type switch designator, see below.
+#type_switch-by = %name%field,%unit
+
+# field type switch variables names to use in addition to %type_switch in case of multiple keys (separated by comma).
+#type_switch-names = type_topic,type_class,type_state
+
+# field type switch for each field type and optionally direction (between dash before the field type) available as
+# %type_switch (as well as the variable names defined in "type_switch-names" if any).
+# The value needs to be a constant list of string pairs with one pair per line. Each pair is separated by "=" and the
+# left part is the value set to the type_switch variable (as well as the variable names defined in %type_switch-names)
+# when the wildcard string in the right part matched the "type_switch-by" value. The list is traversed from top to
+# bottom stopping at the first match. If direction specific definitions exist, these are traversed first. If no line
+# matches at all, the variable(s) are set to the empty string.
+#type_switch-w-number =
+
+
+# field type part suffix to use instead of the field type itself, see below.
+#type_part-by = %type_topic
+
+# field type part mappings for each field type (or the "type_part-by" variable value) in the suffix (available as
+# %type_part).
+#type_part-number = ,
+
+
 # the message definition config topic, payload, and retain setting.
 definition-topic = %prefixn/config/%CIRCUIT/%NAME/%FIELD
 definition-payload = {

src/ebusd/mqtthandler.cpp

@@ -338,7 +338,7 @@ static const char* knownFieldNames[] = {
 /** the number of known field names. */
 static const size_t knownFieldCount = sizeof(knownFieldNames) / sizeof(char*);
 
-std::pair<string, int> makeField(const string name, bool isField) {
+std::pair<string, int> makeField(const string& name, bool isField) {
   if (!isField) {
     return {name, -1};
   }
@@ -350,38 +350,55 @@ std::pair<string, int> makeField(const string name, bool isField) {
   return {name, knownFieldCount};
 }
 
+void addPart(ostringstream& stack, int inField, vector<std::pair<string, int>>& parts) {
+  string str = stack.str();
+  if (inField == 1 && str == "_") {
+    inField = 0; // single "%_" pattern to reduce to "_"
+  } else if (inField == 2) {
+    str = "%{" + str;
+    inField = 0;
+  }
+  if (inField == 0 && str.empty()) {
+    return;
+  }
+  stack.str("");
+  if (inField == 0 && !parts.empty() && parts[parts.size()-1].second < 0) {
+    // append constant to previous constant
+    parts[parts.size()-1].first += str;
+    return;
+  }
+  parts.push_back(makeField(str, inField>0));
+}
 
 bool MqttReplacer::parse(const string& templateStr, bool onlyKnown, bool noKnownDuplicates, bool emptyIfMissing) {
   m_parts.clear();
-  size_t end = templateStr.length();
-  bool inField = false;
+  int inField = 0; // 1 after '%', 2 after '%{'
   ostringstream stack;
-  for (size_t pos = 0; pos < end+1; pos++) {
-    char ch = pos<end ? templateStr[pos] : '\0';
+  for (auto ch : templateStr) {
     bool empty = stack.tellp()<=0;
-    if (ch=='%' || ch=='\0') {
-      if (inField && empty) {  // %% for plain %
-        inField = false;
+    if (ch=='%') {
+      if (inField==1 && empty) {  // %% for plain %
+        inField = 0;
         stack << ch;
       } else {
-        if (!empty) {
-          m_parts.push_back(makeField(stack.str(), inField));
-          stack.str("");
-        }
-        inField = true;
+        addPart(stack, inField, m_parts);
+        inField = 1;
       }
+    } else if (ch=='{' && inField==1 && empty) {
+      inField = 2;
+    } else if (ch=='}' && inField==2) {
+      addPart(stack, 1, m_parts);
+      inField = 0;
     } else {
-      if (inField && !((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || ch == '_')) {
+      if (inField>0 && !((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || ch == '_')) {
         // invalid field character
-        if (stack.tellp()>0) {
-          m_parts.push_back(makeField(stack.str(), true));
-          stack.str("");
-        }
-        inField = false;
+        addPart(stack, inField, m_parts);
+        inField = 0;
       }
       stack << ch;
     }
   }
+  addPart(stack, inField, m_parts);
   if (onlyKnown || noKnownDuplicates) {
     int foundMask = 0;
     int knownCount = knownFieldCount;