from machine import Pin
import time
import json
import os

CALIB_FILE = "calibration.cfg"


# ---------------------------------------------------------
# Calibration File Helpers
# ---------------------------------------------------------

def save_calibration(zero_offset, scale_factor):
    """Save calibration values to internal flash."""
    data = {
        "zero_offset": zero_offset,
        "scale_factor": scale_factor
    }
    with open(CALIB_FILE, "w") as f:
        json.dump(data, f)
    print("✔ Calibration saved.")


def load_calibration():
    """Load existing calibration or return defaults."""
    if CALIB_FILE not in os.listdir():
        print("⚠ No calibration file found, using defaults.")
        return 0, 1

    try:
        with open(CALIB_FILE, "r") as f:
            data = json.load(f)
        print("✔ Calibration loaded.")
        return data.get("zero_offset", 0), data.get("scale_factor", 1)
    except Exception as e:
        print("⚠ Calibration load error:", e)
        return 0, 1


# ---------------------------------------------------------
# HX710B Class
# ---------------------------------------------------------

class HX710B:
    def __init__(self, dout_pin, sck_pin):
        self.dout = Pin(dout_pin, Pin.IN)
        self.sck = Pin(sck_pin, Pin.OUT)
        self.sck.value(0)

        # Load previous calibration (or defaults)
        self.zero_offset, self.scale_factor = load_calibration()

    # -----------------------------------------------------
    # Low-level raw ADC read
    # -----------------------------------------------------
    def read_raw(self):
        """Read the 24-bit raw ADC value."""
        while self.dout.value():
            pass  # wait for data ready

        count = 0
        for _ in range(24):
            self.sck.value(1)
            count = (count << 1) | self.dout.value()
            self.sck.value(0)

        # 25th pulse to set gain for next reading
        self.sck.value(1)
        self.sck.value(0)

        # Signed 24-bit conversion
        if count & 0x800000:
            count -= 0x1000000

        return count

    # -----------------------------------------------------
    # Zero Calibration
    # -----------------------------------------------------
    def calibrate_zero(self, samples=20):
        """Measure 0 kPa and determine zero offset."""
        total = 0
        for _ in range(samples):
            total += self.read_raw()
            time.sleep_ms(5)

        self.zero_offset = total / samples
        save_calibration(self.zero_offset, self.scale_factor)

        print("✔ Zero calibrated:", self.zero_offset)
        return self.zero_offset

    # -----------------------------------------------------
    # Full-scale / Known Pressure Calibration
    # -----------------------------------------------------
    def calibrate_full(self, known_kpa, samples=20):
        """Measure raw ADC at known pressure and compute scaling."""
        total = 0
        for _ in range(samples):
            total += self.read_raw()
            time.sleep_ms(5)

        raw_avg = total / samples
        self.scale_factor = known_kpa / (raw_avg - self.zero_offset)

        save_calibration(self.zero_offset, self.scale_factor)

        print("✔ Scale calibrated:", self.scale_factor)
        return self.scale_factor

    # -----------------------------------------------------
    # Convert raw → kPa using saved calibration
    # -----------------------------------------------------
    def read_kpa(self):
        raw = self.read_raw()
        return (raw - self.zero_offset) * self.scale_factor