"""Physical unit conversions for the laser control module.

Converts between physical quantities (°C, mA, V) and the raw ADC/DAC integer
values used by the device firmware, using the hardware's bridge/divider formulas.
"""

import math
from .constants import ADC_BITS_16, BETA_INTERNAL, R0, R1, R3, R4, R5, R6, RREF, T0_K, VREF


def temp_c_to_n(temp_c: float) -> int:
    """
    Convert temperature (°C) to 16-bit DAC integer (Wheatstone bridge setpoint).

    Args:
        temp_c: Temperature in degrees Celsius.

    Returns:
        Integer in [0, 65535] for the DAC.
    """
    rt = R0 * math.exp(BETA_INTERNAL / (temp_c + 273) - BETA_INTERNAL / T0_K)
    u = VREF / (R5 * (R3 + R4)) * (
        R1 * R4 * (R5 + R6) - rt * (R3 * R6 - R4 * R5)
    ) / (rt + R1)
    n = int(u * ADC_BITS_16 / VREF)
    n = max(0, min(ADC_BITS_16, n))
    return n




def current_ma_to_n(current_ma: float) -> int:
    """
    Convert laser drive current (mA) to 16-bit DAC integer.

    Args:
        current_ma: Current in milliamps.

    Returns:
        Integer in [0, 65535] for the DAC.
    """
    n = int(ADC_BITS_16 / 2000 * RREF * current_ma)
    n = max(0, min(ADC_BITS_16, n))
    return n