#!/usr/bin/env python
# coding:utf-8
# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.

# Messenger API integration example
# We assume you have:
# * a Wit.ai bot setup (https://wit.ai/docs/quickstart)
# * a Messenger Platform setup (https://developers.facebook.com/docs/messenger-platform/quickstart)
# You need to `pip install the following dependencies: requests, bottle.
#
# 1. pip install requests bottle
# 2. You can run this example on a cloud service provider like Heroku, Google Cloud Platform or AWS.
#    Note that webhooks must have a valid SSL certificate, signed by a certificate authority and won't work on your localhost.
# 3. Set your environment variables e.g. WIT_TOKEN=your_wit_token
#                                        FB_PAGE_TOKEN=your_page_token
#                                        FB_VERIFY_TOKEN=your_verify_token
# 4. Run your server e.g. python examples/messenger.py {PORT}
# 5. Subscribe your page to the Webhooks using verify_token and `https://<your_host>/webhook` as callback URL.
# 6. Talk to your bot on Messenger!

from __future__ import absolute_import, division, print_function, unicode_literals

import os
from sys import argv

import requests
from bottle import Bottle, debug, request
from wit import Wit

# Wit.ai parameters
WIT_TOKEN = os.environ.get("WIT_TOKEN")
# Messenger API parameters
FB_PAGE_TOKEN = os.environ.get("FB_PAGE_TOKEN")
# A user secret to verify webhook get request.
FB_VERIFY_TOKEN = os.environ.get("FB_VERIFY_TOKEN")

# Setup Bottle Server
debug(True)
app = Bottle()


# Facebook Messenger GET Webhook
@app.get("/webhook")
def messenger_webhook():
    """
    A webhook to return a challenge
    """
    verify_token = request.query.get("hub.verify_token")
    # check whether the verify tokens match
    if verify_token == FB_VERIFY_TOKEN:
        # respond with the challenge to confirm
        challenge = request.query.get("hub.challenge")
        return challenge
    else:
        return "Invalid Request or Verification Token"


# Facebook Messenger POST Webhook
@app.post("/webhook")
def messenger_post():
    """
    Handler for webhook (currently for postback and messages)
    """
    data = request.json
    if data["object"] == "page":
        for entry in data["entry"]:
            # get all the messages
            messages = entry["messaging"]
            if messages[0]:
                # Get the first message
                message = messages[0]
                # Yay! We got a new message!
                # We retrieve the Facebook user ID of the sender
                fb_id = message["sender"]["id"]
                # We retrieve the message content
                text = message["message"]["text"]
                # Let's forward the message to Wit /message
                # and customize our response to the message in handle_message
                response = client.message(msg=text, context={"session_id": fb_id})
                handle_message(response=response, fb_id=fb_id)
    else:
        # Returned another event
        return "Received Different Event"
    return None


def fb_message(sender_id, text):
    """
    Function for returning response to messenger
    """
    data = {"recipient": {"id": sender_id}, "message": {"text": text}}
    # Setup the query string with your PAGE TOKEN
    qs = "access_token=" + FB_PAGE_TOKEN
    # Send POST request to messenger
    resp = requests.post("https://graph.facebook.com/me/messages?" + qs, json=data)
    return resp.content


def first_trait_value(traits, trait):
    """
    Returns first trait value
    """
    if trait not in traits:
        return None
    val = traits[trait][0]["value"]
    if not val:
        return None
    return val


def handle_message(response, fb_id):
    """
    Customizes our response to the message and sends it
    """
    # Checks if user's message is a greeting
    # Otherwise we will just repeat what they sent us
    greetings = first_trait_value(response["traits"], "wit$greetings")
    if greetings:
        text = "hello!"
    else:
        text = "We've received your message: " + response["_text"]
    # send message
    fb_message(fb_id, text)


# Setup Wit Client
client = Wit(access_token=WIT_TOKEN)

if __name__ == "__main__":
    # Run Server
    app.run(host="0.0.0.0", port=argv[1])