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

"""
   download-settings.py - Upload Tasmota settings file

   Copyright (C) 2021  Theo Arends

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.

Requirements:
   - Python 3.x and Pip:
      sudo apt-get install python3 python3-pip
      pip3 install paho-mqtt json

Instructions:
   Edit file and change parameters in User Configuration Section

   Then execute command download-settings.py

"""

import paho.mqtt.client as mqtt
import time
import base64
import hashlib
import json

# **** Start of User Configuration Section

broker = "domus1"                      # MQTT broker ip address or name
broker_port = 1883                     # MQTT broker port

mytopic = "demo"                       # Tasmota MQTT topic
myfiletype = 2                         # Tasmota Settings file type

# **** End of User Configuration Section

# Derive fulltopic from broker LWT message
mypublish = "cmnd/"+mytopic+"/filedownload"
mysubscribe = "stat/"+mytopic+"/FILEDOWNLOAD"  # Case sensitive

# Tasmota currently supports MQTT message size of 1040 characters. Base64 adds 0.25 chars
chucksize = 700                        # Tasmota max chunk size
Ack_flag = False

file_name = ""
file_id = 0
file_type = 0
file_size = 0
file_md5 = ""

# The callback for when mysubscribe message is received
def on_message(client, userdata, msg):
   global Ack_flag
   global Run_flag
   global file_name
   global file_id
   global file_type
   global file_size
   global file_md5
   global in_hash_md5

   base64_data = ""
   rcv_id = 0

#   print("Received message =",str(msg.payload.decode("utf-8")))

   root = json.loads(msg.payload.decode("utf-8"))
   if "File" in root: file_name = root["File"]
   if "Id" in root: rcv_id = root["Id"]
   if "Type" in root: file_type = root["Type"]
   if "Size" in root: file_size = root["Size"]
   if "Data" in root: base64_data = root["Data"]
   if "Md5" in root: file_md5 = root["Md5"]

   if file_id == 0 and rcv_id > 0 and file_size > 0 and file_type > 0 and file_name:
      file_id = rcv_id
      fi = open(file_name,"wb")
      fi.close()

   else:
      if file_id > 0 and file_id != rcv_id:
         Run_flag = False
         return

   if file_md5 == "" and base64_data:
      base64_decoded_data = base64_data.encode('utf-8')
      chunk = base64.decodebytes(base64_decoded_data)
      in_hash_md5.update(chunk)    # Update hash

      fi = open(file_name,"ab")
      fi.write(chunk)
      fi.close()

   if file_md5 != "":
      md5_hash = in_hash_md5.hexdigest()
      if md5_hash != file_md5:
         print("Error: MD5 mismatch")
         Run_flag = False

   Ack_flag = False

def wait_for_ack():
   global Ack_flag
   global Run_flag
   if Run_flag == False:
      print("Error: Transmission")
      return True

   timeout = 100
   while Ack_flag and timeout > 0:
      time.sleep(0.01)
      timeout = timeout -1

   if Ack_flag:
      print("Error: Timeout")

   return Ack_flag

client = mqtt.Client()
client.on_message = on_message
client.connect(broker, broker_port)
client.loop_start()                    # Start loop to process received messages
client.subscribe(mysubscribe)

time_start = time.time()
print("Downloading file from "+mytopic+" ...")

in_hash_md5 = hashlib.md5()

Err_flag = False

client.publish(mypublish, str(myfiletype))
Ack_flag = True

Run_flag = True
while Run_flag:
   if wait_for_ack():                  # We use Ack here
      Err_flag = True
      Run_flag = False

   else:
      if file_md5 == "":
         client.publish(mypublish, "?")
         Ack_flag = True

      else:
         Run_flag = False

if Err_flag:
   client.publish(mypublish, "0")      # Abort any failed download

time_taken = time.time() - time_start

file_type_name = " Data"
if file_type == 2:
   file_type_name = " Settings"

print("Downloaded"+file_type_name+" saved as "+file_name)
print("Done in "+str("%.2f"%time_taken)+" seconds")

client.disconnect()                    # Disconnect
client.loop_stop()                     # Stop loop