"""Fit probability distributions to IPCC sea level rise forecasts.


Reads:
    'IPCC AR6.xlsx'

Writes:
    'png/*.png'

D. Howe
d.howe@wrl.unsw.edu.au
2022-05-12
"""
import os
import re
import numpy as np
import pandas as pd
from scipy import stats, optimize
import matplotlib.pyplot as plt

# Read data
df = pd.read_excel('IPCC AR6.xlsx', index_col=[0, 1, 2, 3, 4])
df = df.sort_index()

# Use all 'medium' confidence scenarios for intermediate quantiles
scenarios = ['ssp119', 'ssp126', 'ssp245', 'ssp370', 'ssp585']
dff = df.loc[838, 'total', 'medium', scenarios].groupby('quantile').mean()

# Use ssp119/ssp585 for 5th and 95th quantiles
dff.loc[5] = df.loc[838, 'total', 'medium', 'ssp119', 5]
dff.loc[95] = df.loc[838, 'total', 'medium', 'ssp585', 95]
dff = dff.T

dff.index.name = 'year'
percentiles = dff.columns.values / 100
values = dff.loc[2150].values

x_min = values.min() - 0.2
x_max = values.max() + 0.2
x = np.linspace(x_min, x_max, num=1000)

# Get statistical distributions
distributions = [
    getattr(stats, d) for d in dir(stats)
    if isinstance(getattr(stats, d), stats.rv_continuous)
]

for dist in distributions:

    def cdf(x, loc, scale):
        """Calculate cumulative density function"""
        return dist(loc=loc, scale=scale).cdf(x)

    try:
        loc, scale = optimize.curve_fit(cdf, values, percentiles)[0]
        p = {'loc': loc, 'scale': scale}

    except TypeError:
        continue

    fig, ax = plt.subplots(1, 2, figsize=(6, 2))

    ax[0].plot(x, 100 * dist.cdf(x, **p))
    ax[0].plot(values, 100 * percentiles, '.', c='#444444')
    ax[1].plot(x, 100 * dist.pdf(x, **p))

    ax[0].axhline(y=100, c='#000000', lw=0.8, zorder=-1)
    ax[0].set_ylim(0, 101)
    ax[1].set_ylim(bottom=0)

    ax[0].set_title(dist.name, x=-0.7, y=0.5, ha='left')

    for a in ax.ravel():
        a.spines['right'].set_visible(False)
        a.spines['top'].set_visible(False)

    ax[1].set_yticks([])

    plt.savefig(f'png/{dist.name}.png', bbox_inches='tight', dpi=100)
    plt.close()