#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# I need
from glob import glob

# Pytroll/SatPy needs
from satpy import Scene, MultiScene
from satpy.writers import compute_writer_results

# Below is my version from PR#2394 where I copied multiscene.py to wd
from functools import partial
import multiscene
from multiscene import stack

sat = 'MetopB'
reader = 'avhrr_l1b_eps'
area = 'eurol'
generate = True

# Available composites in this script   (see .../satpy/etc/composites/visir.yaml):
# ********************************************************************************
# ['cloud_phase_distinction', 'cloud_phase_distinction_raw', 'cloudtop', 'green_snow',
#  'ir108_3d', 'ir_cloud_day', 'natural_color', 'natural_color_raw', 'natural_enh',
#  'natural_with_night_fog', 'night_fog', 'night_microphysics', 'overview', 'overview_raw']
composites = ['natural_color', 'ir108_3d']

outdir = './images'

# Use blend_type one of 'select_with_weights', 'blend_with_weights', 'stack_no_weights' or None
#blend_type = 'stack_no_weights'
#blend_type = 'select_with_weights'
blend_type = 'blend_with_weights'

scenes = []
for passnum in ['1', '2', '3']:
    passfiles = glob('./pass'+passnum+'/AVHR_xxx*Z')
    scenes.append(Scene(filenames=passfiles, reader=reader))
mscn = MultiScene(scenes)
mscn.load(composites, generate=generate)

if  blend_type in ['select_with_weights', 'blend_with_weights']:
    composites.append('satellite_zenith_angle')
    weights = True
else:
    weights = False

new_mscn = mscn.resample(area, resampler='nearest', reduce_data=False)

if weights:
    weights = []
    for scn in new_mscn.scenes:
        w = scn['satellite_zenith_angle']
        w = w / w.max(dim = ['x', 'y'])
        w = (1 - w * w)
        weights.append(w * w)
    composites.remove('satellite_zenith_angle')
    stack_with_weights = partial(stack, weights=weights, blend_type=blend_type)
    new_scn = new_mscn.blend(blend_function=stack_with_weights)
else:
    new_scn = new_mscn.blend()

if generate:
    for composite in composites:
        new_scn.save_dataset(composite, outdir+'/'+sat+'-'+composite+'-'+area+'-'+blend_type+'.png',
                             fill_value=0)
else:
    save_objects = []
    for composite in composites:
        save_objects.append(new_scn.save_dataset(composite, base_dir='.',
                            filename=outdir+'/'+sat+'-{name}-'+area+'-'+blend_type+'.png',
                            compute=False, fill_value=0))
    compute_writer_results(save_objects)