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

DATA_DIR = "data"
SAMPLE_INTERVAL_MS = 300  # time between measurements in milliseconds

# Find the latest data file
files = [f for f in os.listdir(DATA_DIR) if f.startswith("voltages_") and f.endswith(".txt")]
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 voltage values
voltages = np.loadtxt(filepath)

# Create time axis (in seconds)
times = np.arange(len(voltages)) * (SAMPLE_INTERVAL_MS / 1000.0)

# Plot
plt.figure(figsize=(10, 5))
plt.plot(times, voltages, marker='o', linestyle='-')
plt.xlabel("Time (s)")
plt.ylabel("Voltage (V)")
plt.title(f"Voltage Measurements ({latest_file})")
plt.grid(True)
plt.tight_layout()
plt.show()