#!/usr/bin/env python3

import serial
import os
import time
import configparser
import sys

CONFIG = '/etc/sim.conf'
SERIAL_DEV = '/dev/ttyACM0'
GPIO_PATH = '/sys/class/gpio/'
GPIO_SIM_SW = '44'
GPIO_SIM_RST = '57'
RST_FILE = '/tmp/modem-reset-required'

rst = False

def write_to_file(file, value):
    f = open(file, 'w')                  
    f.write(value)                                          
    f.close()

def reset_modem():
    print("modem reset")
    write_to_file(GPIO_PATH + 'export', GPIO_SIM_RST)
    write_to_file(GPIO_PATH + 'gpio' + GPIO_SIM_RST + '/direction', 'out')
    write_to_file(GPIO_PATH + 'gpio' + GPIO_SIM_RST + '/value', '1')
    time.sleep(2)
    write_to_file(GPIO_PATH + 'gpio' + GPIO_SIM_RST + '/value', '0')
    print("reset done")
    # Wait until modem rebooted   
    while True:                  
        dirs = os.listdir("/dev")                      
        for file in dirs:        
            if file == 'ttyACM2':
                sys.exit(0);
        time.sleep(1)

def is_rst_required():
    global rst
    if rst:
        return True
    elif os.path.exists(RST_FILE):
        return True
    else:
        return False

def switch_sim():
    global rst
    write_to_file(GPIO_PATH + 'export', GPIO_SIM_SW)
    write_to_file(GPIO_PATH + 'gpio' + GPIO_SIM_SW + '/direction', 'out')
    write_to_file(GPIO_PATH + 'gpio' + GPIO_SIM_SW + '/value', '0')
    rst = True

def sim_present(ser):
    cmd = b'AT+CCID?'
    while True:
        try:
            ser.flushInput()
            ser.write(cmd)
            ser.write(b'\r')
            s = ser.read_until(b'OK')
            if b'ERROR' in s:
                return False
            elif b'OK' in s:
                return True
        except Exception as e:
            print("Exception : " + str(e))
        time.sleep(1)
                
    return s


def check_sim_presence():
    while not os.path.exists(SERIAL_DEV):               
        time.sleep(1)                                       
                                                        
    ser = serial.Serial(SERIAL_DEV, 115200, timeout=0.5)
    while True:                                             
        try:             
            ser.read()   
            break        
        except Exception:
            pass 

    if sim_present(ser):
        print("sim present")
    else:
        print("no sim, switching to esim")
        switch_sim()
    ser.close()

def read_config():
    config = configparser.ConfigParser()
    config.read(CONFIG)
    print(config.get('default', 'SIM'))
    sim = config.get('default', 'SIM')
    if sim == 'auto':
        check_sim_presence()
    elif sim == 'esim' or sim == 'ui-top':
         switch_sim()
    # ui-btm and main are default
    if is_rst_required():
        reset_modem()


read_config();