#!/usr/bin/env python3
"""Calibration example for PyPCF8523 RTC driver.

This example demonstrates how to calibrate the RTC for better accuracy:
- Reading calibration settings
- Adjusting calibration offset
- Setting calibration schedule

The PCF8523 can drift up to 2 seconds per day. Calibration helps
compensate for this drift.

Calibration offset range: -64 to +63
- Positive values speed up the clock
- Negative values slow it down

Calibration schedule:
- Per minute: 1 LSB = 4.069 ppm
- Per 2 hours: 1 LSB = 4.340 ppm
"""

import time
from pypcf8523 import PCF8523


def main():
    print("PCF8523 Calibration Example")
    print("=" * 50)

    # Initialize the RTC
    rtc = PCF8523(i2c_bus=1)

    # Read current calibration settings
    current_offset = rtc.calibration
    per_minute = rtc.calibration_schedule_per_minute

    print(f"Current calibration offset: {current_offset}")
    print(f"Calibration schedule: {'Per minute' if per_minute else 'Per 2 hours'}")

    # Calculate ppm (parts per million) offset
    ppm_per_lsb = 4.069 if per_minute else 4.340
    ppm_offset = current_offset * ppm_per_lsb
    print(f"Approximate offset: {ppm_offset:.2f} ppm")

    # Example: Set calibration
    print("\n" + "-" * 50)
    print("Example calibration adjustment:")
    print("-" * 50)

    # If your RTC is running fast (gaining time), use negative offset
    # If your RTC is running slow (losing time), use positive offset

    # Example: Clock gains 2 seconds per day
    # 2 seconds / 86400 seconds = 23.15 ppm
    # Offset needed: 23.15 / 4.069 ≈ -6 (per minute mode)

    new_offset = 0  # Change this based on your measurements
    print(f"\nTo set calibration offset to {new_offset}:")
    print(f"  rtc.calibration = {new_offset}")

    if new_offset != 0:
        print("\nUncomment the following lines to apply:")
        print("  # rtc.calibration_schedule_per_minute = True")
        print(f"  # rtc.calibration = {new_offset}")
        print(f"  # This would give approximately {new_offset * 4.069:.2f} ppm offset")

    # Uncomment to actually apply calibration:
    # rtc.calibration_schedule_per_minute = True
    # rtc.calibration = new_offset

    # How to measure drift:
    print("\n" + "=" * 50)
    print("How to measure and calibrate your RTC:")
    print("=" * 50)
    print("1. Set the RTC to accurate time (sync with NTP)")
    print("2. Wait 24-48 hours")
    print("3. Compare RTC time with accurate time")
    print("4. Calculate drift in seconds per day")
    print("5. Convert to ppm: (drift_seconds / 86400) * 1,000,000")
    print("6. Calculate offset: ppm / 4.069 (per minute mode)")
    print("7. Apply opposite sign: if fast use negative, if slow use positive")
    print("8. Set the calibration offset")
    print("\nExample:")
    print("  If RTC gains 2 seconds/day:")
    print("    2 / 86400 * 1000000 = 23.15 ppm")
    print("    23.15 / 4.069 = 5.69 ≈ 6")
    print("    Use offset = -6 (negative because it's fast)")

    # Check battery status
    print("\n" + "-" * 50)
    if rtc.battery_low:
        print("⚠️  WARNING: Backup battery is low!")
    else:
        print("✓ Backup battery is OK")

    # Clean up
    rtc.close()
    print("\nRTC connection closed")


if __name__ == "__main__":
    main()