nopaque/app/main/events.py

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from flask import current_app, request
from flask_login import current_user, login_required
from .. import db, socketio
from ..models import User
import json
import jsonpatch
import os
'''
' A list containing session ids of disconnected Socket.IO sessions. It is used
' to signal associated background tasks to stop.
'''
disconnected = []
@socketio.on('connect')
@login_required
def connect():
'''
' The Socket.IO module creates a session id (sid) on each request. The
' initiating client is automatically placed in a room with that sid, which
' will be used for further information exchange generated by a background
' task associated with the sid.
'''
socketio.start_background_task(background_task,
current_app._get_current_object(),
current_user.id,
request.sid)
@socketio.on('disconnect')
@login_required
def disconnect():
'''
' On disconnect the session id (sid) of the connection gets placed in the
' disconnected list (see above).
'''
disconnected.append(request.sid)
def background_task(app, user_id, session_id):
'''
' Sends initial corpus and job lists to the client. Afterwards it checks
' every 3 seconds if changes to the initial values appeared. If changes are
' detected, a RFC 6902 compliant JSON patch gets send.
'
' NOTE: The initial values are send as a init-* events.
' The JSON patches are send as update-* events.
'
' > where '*' is either 'corpora' or 'jobs'
'''
with app.app_context():
user = db.session.query(User).filter_by(id=user_id).first()
''' Get current values from the database. '''
corpora = user.corpora_as_dict()
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jobs = user.jobs_as_dict()
''' Send initial values. '''
socketio.emit('init-corpora',
json.dumps(corpora),
room=session_id)
socketio.emit('init-jobs',
json.dumps(jobs),
room=session_id)
''' TODO: Implement maximum runtime for this loop. '''
while session_id not in disconnected:
''' Get current values from the database '''
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new_corpora = user.corpora_as_dict()
new_jobs = user.jobs_as_dict()
''' Compute JSON patches. '''
corpus_patch = jsonpatch.JsonPatch.from_diff(corpora, new_corpora)
jobs_patch = jsonpatch.JsonPatch.from_diff(jobs, new_jobs)
''' In case there are patches, send them to the user. '''
if corpus_patch:
socketio.emit('update-corpora',
corpus_patch.to_string(),
room=session_id)
if jobs_patch:
socketio.emit('update-jobs',
jobs_patch.to_string(),
room=session_id)
''' Set new values as references for the next iteration. '''
corpora = new_corpora
jobs = new_jobs
socketio.sleep(3)
disconnected.remove(session_id)