Propose TemplatePrinter (#56)

* Added TemplatePrinter from @Chris--A  (properly this time)

src/TemplatePrinter.cpp

@@ -0,0 +1,90 @@
+  /************************************************************
+  
+	TemplatePrinter Class
+	
+	A basic templating engine for a stream of text.
+	This wraps the Arduino Print interface and writes to any
+	Print interface.
+	
+	Written by Christopher Andrews (https://github.com/Chris--A) 
+  
+  ************************************************************/
+
+#include "TemplatePrinter.h"
+
+void TemplatePrinter::resetParam(bool flush){
+  if(flush && _inParam){
+    _stream.write(_delimiter);
+
+    if(_paramPos)
+      _stream.print(_paramBuffer);
+  }
+
+  memset(_paramBuffer, 0, sizeof(_paramBuffer));
+  _paramPos = 0;
+  _inParam = false;
+}
+
+
+void TemplatePrinter::flush(){ 
+  resetParam(true);
+  _stream.flush();
+}
+
+size_t TemplatePrinter::write(uint8_t data){
+
+  if(data == _delimiter){
+
+    // End of parameter, send to callback
+    if(_inParam){
+
+      // On false, return the parameter place holder as is: not a parameter
+	  // Bug fix: ignore parameters that are zero length.
+      if(!_paramPos || !_cb(_stream, _paramBuffer)){
+        resetParam(true);
+        _stream.write(data);
+      }else{
+        resetParam(false);
+      }
+
+    // Start collecting parameter
+    }else{
+      _inParam = true;
+    }
+  }else{
+
+    // Are we collecting
+    if(_inParam){
+
+      // Is param still valid
+      if(isalnum(data) || data == '_'){
+
+        // Total param len must be 63, 1 for null.
+        if(_paramPos < sizeof(_paramBuffer) - 1){
+          _paramBuffer[_paramPos++] = data;
+
+        // Not a valid param
+        }else{
+          resetParam(true);
+        }
+      }else{
+        resetParam(true);
+        _stream.write(data);
+      }
+
+    // Just output
+    }else{
+      _stream.write(data);
+    }
+  }
+  return 1;
+}
+
+size_t TemplatePrinter::copyFrom(Stream &stream){
+  size_t count = 0;
+
+  while(stream.available())
+    count += this->write(stream.read());
+
+  return count;
+}

src/TemplatePrinter.h

@@ -0,0 +1,51 @@
+#ifndef TemplatePrinter_h
+  #define TemplatePrinter_h
+
+  #include "PsychicCore.h"
+  #include <Print.h>
+
+  /************************************************************
+  
+	TemplatePrinter Class
+	
+	A basic templating engine for a stream of text.
+	This wraps the Arduino Print interface and writes to any
+	Print interface.
+	
+	Written by Christopher Andrews (https://github.com/Chris--A) 
+  
+  ************************************************************/
+
+  class TemplatePrinter;
+
+  typedef std::function<bool(Print &output, const char *parameter)> TemplateCallback;
+  typedef std::function<void(TemplatePrinter &printer)> TemplateSourceCallback;
+
+  class TemplatePrinter : public Print{
+    private:
+      bool _inParam;
+      char _paramBuffer[64];
+      uint8_t _paramPos;
+      Print &_stream;
+      TemplateCallback _cb;
+      char _delimiter;
+
+      void resetParam(bool flush);
+
+    public:
+      using Print::write;
+
+      static void start(Print &stream, TemplateCallback cb, TemplateSourceCallback entry){
+        TemplatePrinter printer(stream, cb);
+        entry(printer);
+      }
+
+      TemplatePrinter(Print &stream, TemplateCallback cb, const char delimeter = '%') : _stream(stream), _cb(cb), _delimiter(delimeter) { resetParam(false); }
+      ~TemplatePrinter(){ flush(); }
+
+      void flush() override;
+      size_t write(uint8_t data) override;
+      size_t copyFrom(Stream &stream);
+  };
+
+#endif