#!/usr/bin/python3

# file: statusd.py
# date: 26.07.2019
# email: berhsi@web.de

# server, who listen for ipv4 connections at port 10001.

import socket
import os
import logging
import json
from time import time, ctime, sleep
from sys import exit, byteorder


def read_config(CONFIGFILE, CONFIG):
    '''
    reads the given config file and sets the values are founded.
    param 1: string
    param 2: dictionary
    return: boolean
    '''
    logging.debug('Read configfile {}'.format(CONFIGFILE))
    if os.access(CONFIGFILE, os.R_OK):
        logging.debug('Configfile is readable')
        with open(CONFIGFILE, 'r') as config:
            logging.debug('Configfile successfull read')
            for line in config.readlines():
                if not line[0] in ('#', ';', '\n', '\r'):
                    logging.debug('Read entry')
                    key, value = (line.strip().split('='))
                    CONFIG[key.upper().strip()] = value.strip()
                    logging.debug('Set {} to {}'.format(key.upper().strip(), value.strip()))
    else:
        logging.error('Failed to read {}'.format(CONFIGFILE))
        logging.error('Using default values')
        return False
    return True


def print_config(CONFIG):
    '''
    Prints the used configuration, if loglevel ist debug.
    param 1: dictionary
    return: boolean (allways true)
    '''
    logging.debug('Using config:')
    for i in CONFIG.keys():
        logging.debug('{}: {}'.format(i, CONFIG[i]))
    return True


def receive_buffer_is_valid(raw_data):
    '''
    checks, if the received buffer from the connection is valid or not.
    param 1: byte
    return: boolean
    '''
    data = bytes2int(raw_data)
    if data == 0 or data == 1:
        logging.debug('Argument is valid: {}'.format(raw_data))
        return True
    else:
        logging.debug('Argument is not valid: {}'.format(raw_data))
        return False


def bytes2int(raw_data):
    '''
    Convert a given byte value into a integer. If it is possible, it returns
    the integer, otherwise false.
    param 1: byte
    return: integer or false
    '''
    bom = byteorder

    try:
        data = int.from_bytes(raw_data, bom)
    except Exception as e:
        logging.error('Unabele to convert raw data to int: {}'.format(raw_data))
        return False
    return data


def change_status(raw_data, api):
    '''
    Becomes the received byte and the path to API file. Grabs the content of
    the API with read_api() and replaces "open" and "lastchange". Write all
    lines back to API file.
    param 1: byte
    param 2: string
    return: boolean
    '''
    edit = False

    logging.debug('Change status API')
    data = read_api(api)
    if data != False:
        status, timestamp = set_values(raw_data)
        if os.access(api, os.W_OK):
            logging.debug('API file is writable')
            with open(api, 'w') as api_file:
                logging.debug('API file open successfull')
                data["state"]["open"] = status
                data["state"]["lastchange"] = timestamp
                try:
                    json.dump(data, api_file, indent=4)
                except Exception as e:
                    logging.error('Failed to change API file')
                    logging.error('{}'.format(e))
                logging.debug('API file changed')
        else:
            logging.error('API file is not writable. Wrong permissions?')
            return False
        logging.info('Status successfull changed to {}'.format(status))
        return True
    return False


def read_api(api):
    '''
    Reads the API file in an buffer und returns the buffer. If anything goes
    wrong, it returns False - otherwise it returns the buffer.
    param 1: string
    return: string or boolean
    '''
    logging.debug('Open API file: {}'.format(api))
    if os.access(api, os.R_OK):
       logging.debug('API is readable')
       with open(api, 'r') as api_file:
           logging.debug('API opened successfull')
           try:
              api_json_data = json.load(api_file)
              logging.debug('API file read successfull')
           except Exception as e:
               logging.error('Failed to read API file(): {}'.format(e))
               return False
       return (api_json_data)
    logging.error('Failed to read API file')
    return False
    

def set_values(raw_data):
    '''
    Create a timestamp, changes the value of the given byte into a string
    and returns both.
    param 1: byte
    return: tuple
    '''
    timestamp = str(time()).split('.')[0]
    callback = bytes2int(raw_data)
    if callback == 1:
        status = "true"
    else:
        status = "false"
    return (status, timestamp)


def main():
    '''
    The main function - opens a socket und listen for connections.
    '''
    CONFIG = {
        'HOST': 'localhost',
        'PORT': 10001,
        'CERT': None,
        'KEY' : None,
        'TIMEOUT': 3.0,
        'API': './api'
        }
    CONFIG_FILE = './statusd.conf'

    loglevel = logging.DEBUG
    logging.basicConfig(format='%(levelname)s: %(asctime)s: %(message)s', level=loglevel)
    read_config(CONFIG_FILE, CONFIG)
    print_config(CONFIG)

    with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as mySocket:
        logging.debug('Socket created')
        try:
            mySocket.bind((CONFIG['HOST'], int(CONFIG['PORT'])))
            mySocket.listen(5)
            logging.info('Listen on {} at Port {}'.format(CONFIG['HOST'], CONFIG['PORT']))
        except Exception as e:
            logging.error('unable to bind and listen')
            logging.error('{}'.format(e))
            exit()
        while True:
            try:
                conn, addr = mySocket.accept()
                logging.info('Connection from {}:{}'.format(addr[0], addr[1]))
                try:
                    conn.settimeout(float(CONFIG['TIMEOUT']))
                    logging.debug('Connection timeout set to {}'.format(CONFIG['TIMEOUT']))
                except Exception as e:
                    logging.error('Canot set timeout to {}'.format(CONFIG['TIMEOUT']))
                    logging.error('Use default value: 3.0')
                    conn.settimeout(3.0)
                raw_data = conn.recv(1)
                if receive_buffer_is_valid(raw_data) == True:
                    if change_status(raw_data, CONFIG['API']) == True:
                        logging.debug('Send {} back'.format(raw_data))
                        conn.send(raw_data)
                    # change_status returns false:
                    else:
                        logging.info('Failed to change status')
                        conn.send(b'\x03')
                # recive_handle returns false:
                else:
                    logging.info('Inalid argument recived: {}'.format(raw_data))
                    logging.debug('Send {} back'.format(b'\x03'))
                    conn.send(b'\x03')
                sleep(0.1) # protection against dos
            except KeyboardInterrupt:
                print('\rExit')
                logging.info('Exit')
                exit()
            except Exception as e:
                logging.error('{}'.format(e))


if __name__ == '__main__':
    main()