import os
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import numpy as np

from datetime import datetime

DATA_DIR = "data"

# Find the latest data file
files = [f for f in os.listdir(DATA_DIR) if f.startswith("voltages_") and f.endswith(".csv")]
if not files:
    raise FileNotFoundError("No voltage data files found in 'data/'")

latest_file = max(files, key=lambda f: os.path.getmtime(os.path.join(DATA_DIR, f)))
filepath = os.path.join(DATA_DIR, latest_file)
print(f"Plotting data from {filepath}")

# Load CSV data
timestamps = []
voltages = []

with open(filepath, "r") as f:
    next(f)  # skip header
    for line in f:
        ts_str, v_str = line.strip().split(",")
        ts = datetime.strptime(ts_str, "%Y-%m-%d %H:%M:%S.%f")
        timestamps.append(ts)
        voltages.append(float(v_str))

# Plot
plt.figure(figsize=(12, 5))
plt.scatter(timestamps, voltages, marker='o', linestyle='-', s=0.2)

plt.xlabel("Time (CET)")
plt.ylabel("Voltage (V)")
plt.title(f"Voltage Measurements ({latest_file})")
plt.grid(True)

# Format x-axis for readable time
plt.gcf().autofmt_xdate()
plt.gca().xaxis.set_major_formatter(mdates.DateFormatter("%H:%M:%S"))

plt.tight_layout()
plt.show()