import numpy as np
from modules.dcum import dcum  # 确保你有这个函数

def dladgen(a, b):
    """
    Generate Leaf Inclination Distribution Function (LIDF)
    using a two-parameter beta distribution.

    Parameters:
        a, b : shape parameters of beta distribution

    Returns:
        freq  : frequency (probability) per inclination class (length 13)
        litab : central inclination angles (degrees)
    """
    litab = np.array([5., 15., 25., 35., 45., 55., 65., 75., 81., 83., 85., 87., 89.])
    freq = np.zeros_like(litab)

    # First 8 bins: 10° steps
    for i in range(8):
        t = (i + 1) * 10
        freq[i] = dcum(a, b, t)

    # Next 4 bins: finer steps from 80° to 89°
    for i in range(8, 12):
        t = 80.0 + (i - 8 + 1) * 2.0
        freq[i] = dcum(a, b, t)

    freq[12] = 1.0  # total cumulative = 1

    # Convert cumulative to class probabilities
    for i in range(12, 0, -1):
        freq[i] -= freq[i - 1]

    return freq, litab