# Copyright 2015 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import logging
import os
import socket

from flask import Flask, request


app = Flask(__name__)


def is_ipv6(addr):
    """Checks if a given address is an IPv6 address."""
    try:
        socket.inet_pton(socket.AF_INET6, addr)
        return True
    except socket.error:
        return False


# [START example]
@app.route('/')
def index():
    instance_id = os.environ.get('GAE_INSTANCE', '1')

    user_ip = request.remote_addr

    # Keep only the first two octets of the IP address.
    if is_ipv6(user_ip):
        user_ip = ':'.join(user_ip.split(':')[:2])
    else:
        user_ip = '.'.join(user_ip.split('.')[:2])

    with open('/tmp/seen.txt', 'a') as f:
        f.write('{}\n'.format(user_ip))

    with open('/tmp/seen.txt', 'r') as f:
        seen = f.read()

    output = """
Instance: {}
Seen:
{}""".format(instance_id, seen)

    return output, 200, {'Content-Type': 'text/plain; charset=utf-8'}
# [END example]


@app.errorhandler(500)
def server_error(e):
    logging.exception('An error occurred during a request.')
    return """
    An internal error occurred: <pre>{}</pre>
    See logs for full stacktrace.
    """.format(e), 500


if __name__ == '__main__':
    # This is used when running locally. Gunicorn is used to run the
    # application on Google App Engine. See entrypoint in app.yaml.
    app.run(host='127.0.0.1', port=8080, debug=True)