UartReadLineStateComponent.h

#include "esphome.h"

    class UartReadLineStateComponent : public Component, public UARTDevice, public TextSensor {
     public:
      UartReadLineStateComponent(UARTComponent *parent) : UARTDevice(parent) {}    
      void setup() override {
        // nothing to do here
      }    

      int readline(int readch, char *buffer, int len)
      {
        static int pos = 0;
        int rpos;
      
        if (readch > 0) {
          switch (readch) {
            case '\n': // Ignore new-lines
              break;
            case '\r': // Return on CR
              rpos = pos;
              pos = 0;  // Reset position index ready for next time
              return rpos;
            default:
              if (pos < len-1) {
                buffer[pos++] = readch;
                buffer[pos] = 0;
              }
          }
        }
        // No end of line has been found, so return -1.
        return -1;
      }    

      void loop() override {
        const int max_line_length = 80;
        static char buffer[max_line_length];
        if (available() && readline(read(), buffer, max_line_length) > 0) {
          publish_state(buffer);
        }
      }
    };