add daemon mode

hopi/data_handler.py

@@ -1,11 +1,45 @@
+import csv
 import json
+import os
 import math
 import struct
-from typing import Iterable, List
+from typing import List, Optional
 
 from .models import PowerMeterReadings
 
 
+class ReadingsCsvLogger:
+    def __init__(self, file_path: str, fieldnames: List[str]):
+        self._file_path = file_path
+        self._fieldnames = fieldnames
+        self._fp = None
+        self._writer: Optional[csv.DictWriter] = None
+
+    def __enter__(self) -> "ReadingsCsvLogger":
+        is_new_file = (not os.path.exists(self._file_path)) or os.path.getsize(self._file_path) == 0
+        self._fp = open(self._file_path, "a", newline="", encoding="utf-8")
+        self._writer = csv.DictWriter(self._fp, fieldnames=self._fieldnames)
+        if is_new_file:
+            self._writer.writeheader()
+            self._fp.flush()
+        return self
+
+    def __exit__(self, exc_type, exc, tb) -> None:
+        if self._fp is not None:
+            try:
+                self._fp.flush()
+            finally:
+                self._fp.close()
+        self._fp = None
+        self._writer = None
+
+    def log(self, row: dict) -> None:
+        if self._writer is None or self._fp is None:
+            raise RuntimeError("CSV logger is not open")
+        self._writer.writerow(row)
+        self._fp.flush()
+
+
 class PowerMeterDataHandler:
     """Parses Modbus RTU responses and computes derived power metrics."""
 
@@ -90,6 +124,31 @@ class PowerMeterDataHandler:
     def print_readings_json(self, readings: PowerMeterReadings) -> None:
         print(self.readings_to_json(readings, ensure_ascii=False))
 
+    def open_csv_logger(self, file_path: str) -> ReadingsCsvLogger:
+        fieldnames = ["timestamp"] + self._flat_readings_keys()
+        return ReadingsCsvLogger(file_path=file_path, fieldnames=fieldnames)
+
+    @staticmethod
+    def _flat_readings_keys() -> List[str]:
+        # Keep order stable for CSV columns.
+        return [
+            "active_power_w",
+            "rms_current_a",
+            "voltage_v",
+            "frequency_hz",
+            "power_factor",
+            "annual_power_consumption_kwh",
+            "active_consumption_kwh",
+            "reactive_consumption_kwh",
+            "load_time_hours",
+            "work_hours_per_day",
+            "device_address",
+            "apparent_power_vi_va",
+            "apparent_power_pf_va",
+            "reactive_power_var",
+            "apparent_consumption_kvah",
+        ]
+
     @staticmethod
     def _bytes_to_registers_be(data: bytes) -> List[int]:
         registers: List[int] = []