#!/usr/bin/env python


import sys, os
import argparse, json
import random, subprocess, signal, time


"""
" CLI
"""

parser = argparse.ArgumentParser(
    prog='wallpaper',
    description='Cycle through wallpapers'
)

parser.add_argument(
    '--config',
    required=True,
    help='{<weight>: { find: <path>, exclude: <path> }, <weight>:...}'
)

parser.add_argument(
    '--interval',
    default=600
)

args = parser.parse_args()

config = json.loads(args.config)


"""
" Program
"""

pid_running = -1
while True:
    probability_number = random.randrange(start=1, stop=100, step=1)

    # build "find" command based on args.config
    # see https://stackoverflow.com/questions/16489449/select-element-from-array-with-probability-proportional-to-its-value/16490300#16490300
    find_cmd = ''
    accumulative = 0
    for weight, wallpaper_path in config.items():
        lower_bound = accumulative
        accumulative += int(weight)
        upper_bound = accumulative

        if lower_bound <= probability_number and probability_number <= upper_bound:
            find_cmd = 'find "{find}" -type f'.format(find=wallpaper_path['find'])

            if 'exclude' in wallpaper_path.keys():
                find_cmd += ' -not -path "{exclude}"'.format(exclude=wallpaper_path['exclude'])

            break

    # run swaybg
    swaybg_cmd = f'swaybg -i $({find_cmd} | shuf -n1) -m fill &'
    subprocess.run(swaybg_cmd, shell=True)

    # wait until new instance of swaybg has booted up properly
    time.sleep(5)

    # kill the previous process
    # the new swaybg process takes its place automatically
    if pid_running != -1:
        os.kill(pid_running, signal.SIGTERM)

    # set pid for next iteration
    pid_running = int(subprocess.check_output(['pidof', 'swaybg']))

    # wait $INTERVAL seconds
    time.sleep(int(args.interval))