From d9f5da576220fa21b8dc37542267cac0b95e009f Mon Sep 17 00:00:00 2001
From: Mika <kontakt@donau2space.de>
Date: Sun, 8 Mar 2026 03:07:04 +0000
Subject: [PATCH] Add data_logging/src/data_logging/core.py

---
 data_logging/src/data_logging/core.py | 75 +++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 data_logging/src/data_logging/core.py

diff --git a/data_logging/src/data_logging/core.py b/data_logging/src/data_logging/core.py
new file mode 100644
index 0000000..0594538
--- /dev/null
+++ b/data_logging/src/data_logging/core.py
@@ -0,0 +1,75 @@
+from __future__ import annotations
+import csv
+from dataclasses import dataclass, asdict
+from datetime import datetime
+from pathlib import Path
+from typing import Any, Dict
+import os
+import logging
+
+
+# Setup basic logging for internal operations
+logging.basicConfig(level=logging.INFO, format='%(asctime)s [%(levelname)s] %(message)s')
+
+
+class LogFileError(Exception):
+    """Custom exception raised when logfile writing fails."""
+    pass
+
+
+@dataclass
+class LogEntry:
+    """Represents a single sensor data point."""
+    time: str
+    lux: float
+    dB: float
+    temperature: float
+    inference_score: float
+
+    def __post_init__(self) -> None:
+        if not isinstance(self.time, str):
+            raise TypeError("time must be a string")
+        for field_name, value in [("lux", self.lux), ("dB", self.dB), ("temperature", self.temperature), ("inference_score", self.inference_score)]:
+            if not isinstance(value, (float, int)):
+                raise TypeError(f"{field_name} must be a number")
+        # Convert numeric values to float explicitly
+        self.lux = float(self.lux)
+        self.dB = float(self.dB)
+        self.temperature = float(self.temperature)
+        self.inference_score = float(self.inference_score)
+
+    def to_dict(self) -> Dict[str, Any]:
+        """Convert instance data to a dictionary for CSV/JSON writing."""
+        return asdict(self)
+
+
+def log_data(entry: LogEntry, output_path: str = 'output/sensor_data_log.csv') -> None:
+    """Appends a LogEntry to the configured log file."""
+    if not isinstance(entry, LogEntry):
+        raise TypeError("entry must be an instance of LogEntry")
+    if not isinstance(output_path, str):
+        raise TypeError("output_path must be a string")
+
+    output_file = Path(output_path)
+    output_file.parent.mkdir(parents=True, exist_ok=True)
+
+    row = entry.to_dict()
+    file_exists = output_file.exists()
+    try:
+        with open(output_file, mode='a', newline='', encoding='utf-8') as csvfile:
+            writer = csv.DictWriter(csvfile, fieldnames=row.keys())
+            if not file_exists:
+                writer.writeheader()
+            writer.writerow(row)
+            logging.info(f"Logged data to {output_file}: {row}")
+    except (OSError, csv.Error) as e:
+        logging.error(f"Failed to write to log file {output_file}: {e}")
+        raise LogFileError(f"Error writing to log file {output_file}: {e}")
+
+
+# Self-test safeguard for CI integrity
+if __name__ == '__main__':
+    now = datetime.now().strftime('%H:%M:%S')
+    test_entry = LogEntry(time=now, lux=120.5, dB=45.2, temperature=23.7, inference_score=0.87)
+    log_data(test_entry)
+    logging.info("Sample log entry written successfully.")