lnpireceiver

a simple flask server to accept json data from a source such as a flutter app. This is based on code from https://rahmanfadhil.com/flask-rest-api/

The expected format of the posted data is

{
	"studycode": "driving 0.1",
	"data_version": "0.1",
	"guid": "ab1235-x25",
	"data": "[[1,2,3], [4,5,6]]"
}

to post data

To post data
curl http://160.94.0.29:5000/posts \
    -X POST \
    -H "Content-Type: application/json" \
    -d '{"studycode":"driving", "guid": "ab1235-x25", "data_version":"0.1", "data":"[[1,2,3], [4,5,6]]"}'
    
curl http://160.94.0.29:5000/posts -X POST -H "Content-Type: application/json" -d '{"studycode":"driving", "guid": "ab1235-x25", "data_version":"0.1", "data":"[[1,2,3], [4,5,6]]"}'

For flutter see: https://flutter.dev/docs/cookbook/networking/send-data

to check on the data, only for testing, don't want to be able to do this in production

To check on all data
curl http://160.94.0.29:5000/posts

to initialize the database

# change the app.config['SQLALCHEMY_DATABASE_URI'] to a correct URI first
$ python
import receiverlnpi
receiverlnpi.db.create_all()
exit()

to start the server

# change the app.config['SQLALCHEMY_DATABASE_URI'] to a correct URI first
python receiverlnpi.py

to create a docker container

# run this command in the lnpireceiver directory
sudo docker build -t lnpireceiver .

to run the container

# get the info on the container
sudo docker images | grep lnpi
# to run the container on port 5001
# this makes it available at http://localhost:5001/posts 
sudo docker run -p 5001:5001 lnpireceiver

# there is a file x0-29.conf which is an apache config file
# which sets up reverseproxy

to initialize a virtual environment

python -m venv venv/flaskrest
source venv/flaskrest/bin/activate
cd lnpireceiver
pip install -r requirements.txt

python example pulling data

import requests
import json

# pull response #18
req = "http://160.94.0.29:5000/posts/18"

response = requests.get(req)
print(response.json()['created_on'])

# load the json in the data field into a python object
d = json.loads(response.json()['data'])
print("length of data list: ", len(d))

another data example with use of dictionary in the data element to make it more machine readable

{
	"studycode": "driving 0.1",
	"data_version": "0.1",
	"guid": "ab1235-x25",
	"data": {
  		"SubjectID": "1235",
		"moves": [
			["time", "pos1", "pos2"],
			[0, 0, 0],
			[20, 0.1, 2.0],
			[30, 0.2, 1.0]
		]
	}
}

sample code to read in the json into a pandas dataframe

import json
import pandas as pd

filename = "sample1.json"
f = open(filename, "r")

# returns JSON object as  
# a dictionary 
d = json.load(f) 

# read the "moves" list into a pandas dataframe
mdata = d["data"]["moves"]
column_names = mdata.pop(0)
df = pd.DataFrame(mdata, columns=column_names)
print(df)

some helpful info for handing datetime with python in json

https://code-maven.com/serialize-datetime-object-as-json-in-python

generating datetime json with dart

https://codingwithjoe.com/dart-fundamentals-working-with-json-in-dart-and-flutter/

class Student {
  final String name;
  final String email;
  final DateTime dob;

  Student(this.name, this.email, this.dob);
} 

import 'dart:convert';

  static String toJson(Student s) {
    Map<String, dynamic> map() =>
    {
      'name': s.name,
      'email': s.email,
      'dob': s.dob.toIso8601String()
    };

    String result = jsonEncode(map());
    return result;
  }