from mfrc522 import SimpleMFRC522
reader = SimpleMFRC522()


def read():
    try:
        rfid, title = reader.read()
    finally:
        GPIO.cleanup()

def write(input_text):
    try:
        rfid, title = reader.write(input_text)
    finally:
        GPIO.cleanup()

@app.route("/inventory")
def inventory():
    books = Book.query.all()
    return render_template('inventory.html', rows=books)

@app.route("/inventory", methods=['POST'])
def update_inventory():
    if 'return' in request.form:
        rfid = request.form['return']
        book = Book.query.filter(Book.rfid == rfid).first()
        book.loaned_to = None
        db.session.commit()
    elif 'delete' in request.form:
        rfid = request.form['delete']
        book = Book.query.filter(Book.rfid == rfid).first()
        db.session.delete(book)
        db.session.commit()
    return redirect(url_for('inventory'))

@app.route('/register')
def register():
    return render_template('register.html')

@app.route('/register', methods=['POST'])
def register_post():
    form_title = request.form['title']
    try:
        rfid, title = reader.write(form_title)
    finally:
        GPIO.cleanup()
    book = Book(rfid=rfid, title=title)
    db.session.add(book)
    db.session.commit()
    return redirect(url_for('index'))

  def write(self, text):
      id, text_in = self.write_no_block(text)
      while not id:
          id, text_in = self.write_no_block(text)
      return id, text_in

  def write_no_block(self, text):
      (status, TagType) = self.READER.MFRC522_Request(self.READER.PICC_REQIDL)
        ... <Cool and crazy Register stuff>
      return id, text[0:(len(self.BLOCK_ADDRS) * 16)]

from flask import Response

@app.route('/large.csv')
def generate_large_csv():
    def generate():
        for row in iter_all_rows():
            yield ','.join(row) + '\n'
    return Response(generate(), mimetype='text/csv')

@app.route('/stream')
def streamed_response():
    def generate():
        yield 'Hello '
        yield request.args['name']
        yield '!'
    return Response(stream_with_context(generate()))

@app.route('/scanning')
def scanning():
    start = time.time()
    timeout = 1.0
    while time.time() < start + timeout:
        try:
            id, text = reader.read_no_block()
            if (id and id not in scans):
                scans.add(id)
                break
        finally:
            GPIO.cleanup()
    books = Book.query.filter(Book.rfid.in_(scans)).all()
    return render_template('stream.html', rows=books)

<h1>Scan your books</h1>
<a href="/checkout">Done</a>
<ul>
    {% for book in rows %}
      <li>{{ book.title }}</li>
    {% endfor %}
</ul>
<script>
    setTimeout(function() {
      location.reload();
    }, 250);
</script>
<a href="/" >Home Screen</a>

@app.route("/checkout")
def checkout():
    global scans, cart
    cart = scans.copy()
    books = Book.query.filter(Book.rfid.in_(cart)).all()
    scans = set()
    return render_template('checkout.html', rows=books)

@app.route("/checkout", methods=['POST'])
def checkout_post():
    global cart
    lendee = request.form['lendee']
    books = Book.query.filter(Book.rfid.in_(cart)).all()
    for book in books:
        book.loaned_to = lendee
        db.session.commit()
    return redirect(url_for('index'))